Dry Sintering Meets Wet Silver‐Ion “Soldering”: Charge‐Transfer Plasmon Engineering of Solution‐Assembled Gold Nanodimers From Visible to Near‐Infrared I and II Regions

Achieving highly tunable and localized surface plasmon resonance up to near infrared (NIR) regions is a key target in nanoplasmonics. In particular, a self‐assembly process capable of producing highly uniform and solution‐processable nanomaterials with tailor‐made plasmonic properties is lacking. We herein address this problem through a conjunctive use of wet Ag⁺ soldering and dry thermal sintering to produce nanodimer‐derived structures with precisely engineered charge‐transfer plasmon (CTP). The sintered dimers are water soluble, featuring gradually shifted CTP spanning an 800 nm wavelength range (up to NIR II). Upon silica removal, the products are grafted by DNA to offer surface functionality. This process is also adaptable to DNA‐linked AuNP dimers toward plasmonic meta‐materials via DNA‐guided soldering and sintering.     

Single Atoms of Iron on MoS2 Nanosheets for N2 Electroreduction into Ammonia

Efforts have been devoted to achieving a highly efficient artificial synthesis of ammonia (NH₃). Reported herein is a novel Fe-MoS₂ catalyst with Fe atomically dispersed onto MoS₂ nanosheets, imitating natural nitrogenase, to boost N₂ electroreduction into NH₃ at room temperature. The Fe-MoS₂ nanosheets exhibited a faradic efficiency of 18.8 % with a yield rate of 8.63 μg mg_cat.⁻¹ h⁻¹ for NH₃ at −0.3 V versus the reversible hydrogen electrode. The mechanism study revealed that the electroreduction of N₂ was promoted and the competing hydrogen evolution reaction was suppressed by decorating the edge sites of S in MoS₂ with the atomically dispersed Fe, resulting in high catalytic performance for the electroreduction of N₂ into NH₃. This work provides new ideas for the design of catalysts for N₂ electroreduction and strengthens the understanding about N₂ activation over Mo-based catalysts.     

Transformation devices with optical nihility media and reduced realizations

Starting from optical nihility media (ONM), we design several intriguing devices with transformation optics method in two dimensions, such as a wave splitter, a concave lens, a field rotator, a concentrator, and an invisibility cloak. Though the extreme anisotropic property of ONM hinders the fabrication of these devices. We demonstrate that those devices could be effectively realized by simplified materials with Fabry–Pérot resonances (FPs) at discrete frequencies. Moreover, we propose a reduced version of simplified materials with FPs to construct a concentrator and a rotator, which is feasible in experimental fabrications. The simulations of total scattering cross-sections confirm their functionalities.     

Experimental Observations of Constricted and Diffuse Anode Attachment in a Magnetically Rotating Arc at Atmospheric Pressure

Plasma Chemistry and Plasma Processing - At atmospheric pressure, the anode attachment can appear in two different modes: constricted and diffuse. In this paper, a magnetically rotating arc plasma...     

Effect of energy dependent cross-section on flow velocity measurements with charge exchange spectroscopy in magnetized plasma

Charge exchange spectroscopy (CXS) is widely used to measure plasma flow velocity. Accurate measurement is heavily affected by energy dependent cross section between neutral atoms and impurity ions. One symmetric layout of poloidal CXS is applied on Large Helical Device. Correction velocity due to the cross section is exacted from total velocity when actual plasma flow velocity is acquired with the benefit of this layout. A linear relationship between correction velocity and ion temperature is observed. Abundant discharges with wide plasma conditions are investigated and the ratio of correction velocity to ion temperature with the same beam energy shows the normal distribution. The impact of beam energy on the ratio of correction velocity to ion temperature of the carbon system and the hydrogen system is discovered based upon the statistics. Effective emission coefficient (Q) from Atomic Data and Analysis Structure (ADAS) is utilized to study the dependence of correction velocity on Q. The relationship in which the ratio of correction velocity to ion temperature increases linearly with the increasing normalized effective emission coefficient ((1/Q)dQ/dv) is observed. Experimental (1/Q)dQ/dv is obtained according to this observation, and comparison with different fractions of n?=?2 excited state is also discussed. The influence of different receivers (carbon and hydrogen) is also presented. The experimental (1/Q)dQ/dv from the carbon system decreases with beam energy decreasing when beam energy is less than 30 keV/amu. This tendency of (1/Q)dQ/dv at low beam energy indicates the existence of the contribution of n?=?2 excited state donors to the cross section.     

利用空间外差光谱技术进行紫外高分辨率大气散射信号探测

羟基OH对于人类理解中间层化学成分非常重要,它是大气光化学反应中重要的氧化剂,OH在308 nm波段受到太阳能量激发,发射出OH A2Σ＋-X２Π（0,0）荧光信号。为了探测中间层大气中OH自由基的紫外共振荧光发射信号,从复杂背景信号中分离目标信号,研制了中高层大气OH自由基超分辨空间外差光谱仪,光谱范围为308.2～309.8 nm,光谱分辨率为0.008 25 nm。临边观测主要探测大气散射信号,能量来源为大气中的粒子,包括大气分子与气溶胶、云等对太阳能量的散射作用。中高层大气OH自由基超分辨空间外差光谱仪基于空间外差光谱技术,可以在设计的闪耀波长范围内获得极高的光谱分辨率,适用于大气成分的精细探测。通过在前置或后置光学系统中加入柱面镜,总视场内的场景被分成多个视场切片,每一个视场切片的干涉图分别成像到对应的探测器行上。利用空间外差光谱仪具有空间维分层成像功能,临边观测时可以同时获取不同高度层大气吸收光谱的散射辐射信号,无需像传统临边探测遥感器在不同高度层进行扫描来获取大气高度维的廓线信息。为了验证中高层大气OH自由基超分辨空间外差光谱仪的临边散射信号探测能力与对观测几何的敏感性,进行了地面临边观测实验,探测紫外308 nm波段大气散射信号。模拟临边观测几何,选取晴朗无云的一天,在空旷场地对大气散射信号进行观测。由于仪器基于空间外差光谱技术,需要对干涉数据进行干涉误差修正与光谱复原。对一段观测时间内间隔10分钟的干涉数据进行光谱复原并定标,得到最终临边观测光谱。由于散射信号的主要来源为大气分子对太阳光的散射作用,因此光谱中应包含太阳光谱高分辨率精细特征信息。从高分辨率太阳光谱中选取三个特征信息窗,分析观测光谱中对应波段,三个特征信息窗完全匹配,验证了中高层大气OH自由基超分辨空间外差光谱仪的超高分辨率光谱探测能力和光谱精细信息提取能力。将太阳辐射计实时测量获得的气溶胶光学厚度及根据观测时间计算的太阳天顶角与太阳方位角输入辐射传输模型SCIATRAN,结合对应日期与经纬度的大气廓线数据库,得到模拟光谱,将实测结果与辐射传输模型结果进行比对,两者残差较小。实测结果与模拟结果存在的残差,可能是由于大气环境参数并没有完全符合实测状态,后续可使用当地实时温湿压廓线对模拟数据库进行替换,使辐射传输模型更接近实际状态。与辐射传输模型对比的结果验证了中高层大气OH自由基超分辨空间外差光谱仪的散射信号探测能力与对观测几何的敏感性,验证了在轨探测多谱段、宽谱段大气散射光谱与OH目标信号的可行性,为在轨探测OH目标信号提供了理论与实验基础。     

基于ip-iq理论的改进谐波检测方法

有源电力滤波器(APF)是电力系统中实现电能质量管理的关键设备,谐波检测作为APF的关键技术之一,检测的精度和响应速度直接决定了APF的整体性能。介绍了传统的基于瞬时无功功率理论的ip-iq谐波电流检测算法; 针对其检测精度受锁相环输出相位误差影响,以及低通滤波器的存在限制了谐波检测系统的响应速度,提出了应用锁频环技术,产生与电网电压同频的单位正余弦信号的一种改进谐波检测算法; 并提出采用滑动平均滤波器(MAF)代替低通滤波器提高其响应速度以及改善谐波检测精度; 对改进的检测算法进行了理论分析,通过MATLAB进行仿真研究,理论分析和仿真结果都证明了该方法的有效性。     

小型超导电源系统退磁保护回路建模与仿真

计算了采用二极管等效电压源模型和等效电阻模型的退磁回路电流响应和二极管功耗,分析了两个模型的特点和差异,在此基础上,为了进一步提高精度,充分考虑了二极管的非线性特性,以实际二极管伏安特性进行曲线拟合建立函数关系式得到二极管非线性模型,代入回路方程并求解。综合对比各模型的仿真结果后,得出采用二极管非线性模型和等效电压源模型能更好地模拟退磁保护响应。     

基于细胞红外光谱预测乙酰化细胞的辐射敏感性

组蛋白乙酰化是表观遗传修饰的一种重要方式。肿瘤细胞的组蛋白大部分呈现低乙酰化状态,而组蛋白去乙酰化酶抑制剂（histone deacetylase inhibitor,HDACi）可以增加肿瘤细胞的乙酰化水平,诱导细胞周期阻滞及凋亡。曲古菌素A （trichostatin A,TSA）是组蛋白去乙酰化酶抑制剂的代表药物之一,能够提高肿瘤细胞组蛋白和非组蛋白的乙酰化水平。傅里叶变换红外（Fourier Transform Infrared,FTIR）光谱可以对无染色、无标记的生物样品进行无损检测,具有特征性明显、快速、分辨率高、重复性好等优点,已被广泛用于细胞的微观生物过程的研究。本文利用红外光谱技术结合免疫荧光技术的手段,研究TSA处理细胞后的乙酰化作用效果,发现红外光谱中甲基与亚甲基的伸缩振动强度之比能够表征细胞内的乙酰化水平变化,然后基于红外光谱的分析结果预测了乙酰化状态不同的细胞辐射敏感性的变化。结果表明,乙酰化细胞的辐射损伤效应可以通过甲基与亚甲基的伸缩振动强度之比进行评价,且该比值与细胞的辐射敏感性呈正相关,表明红外光谱技术可以辅助预测细胞的辐射敏感性,并进行细胞表观遗传学特征与辐射效应关系的研究。Histone acetylation is one of important epigenetic modifications, and histone in most of tumor cells shows low acetylation state. However, histone deacetylase inhibitor (HDACi) can correct abnormal acetylation status, induce cell cycle arrest and apoptosis. Trichostatin A (TSA) is one of the representatives of histone deacetylase inhibitors, which can inhibit histone deacetylase, increase the acetylation level of histone and nonhistone in cell. Fourier transform infrared (FTIR) spectroscopy is a powerful analytical tool which can detect nondestructively, quatitatively and quantitatively biological samples without bio-tagging and bio-labeling. FTIR spectroscopy technology has multiple advantages, including finger-print characteristics, rapid analysis, high resolution and good repeatability. Therefore, it has been widely used in the research of biological processes. This work applied FTIR spectroscopy to study the changes in cells treated with TSA, compared the acetylation level according to FTIR intensity ratio of methyl to methylene stretching vibration, and based on the FTIR analysis predicted the radiosensitivity of the cells with different acetylation levels. As a result, we have verified that the damage caused by radiation in acetylated cells can be evaluated by the ratio of methyl and methylene intensity which is positively correlated with cellular radiosensitivity. Therefore, this work demonstrates that FTIR spectroscopy can be useful for the prediction of radiosensitivity and may also open a door for the study of relationship between epigenetics and radiation bio-effects.     

机载腔增强吸收光谱系统应用于大气NO_2空间高时间分辨率测量

介绍了一套用于机载平台测量的非相干宽带腔增强吸收光谱(IBBCEAS)系统,并应用于实际大气NO_2空间分布的高时间分辨率观测.为满足机载测量中对时间分辨率的需求,系统采用离轴抛物面镜代替消色差透镜提高光学耦合效率;并运用Allan方差,对系统性能进行了分析.通过腔增强吸收光谱系统与长光程吸收光谱系统对实际大气NO_2的对比测试,两者线性相关系数R~2达到0.86.将IBBCEAS系统应用于机载平台,在时间分辨率为2 s的情况下,探测限达到95 ppt(1σ).通过机载观测,获得了华北地区石家庄等地上空对流层大气NO_2的廓线信息.