菌紫质薄膜光致折射率变化的理论计算和实验测量

基因改性细菌视紫红质BR-D96N由于M态寿命的延长而具有显著的光致变色特性.根据Kramers-Kronig变换关系,样品吸收光谱的变化会引起样品折射率的变化.本文首先从实验上测量了BR-D96N薄膜样品在光激发前后的吸收光谱,然后根据Kramers-Kronig变换关系,理论计算了对应此光致变色光谱变化的光致折射率变化光谱.实验上为了直接测量样品的光致折射率变化,采用Michelson干涉方法测量BR-D96N薄膜在不同探测波长下的光致折射率变化量,并与理论计算曲线进行了比较.     

Discrimination of basal cell carcinoma from normal dermal stroma by quantitative multiphoton imaging

We performed multiphoton fluorescence (MF) and second-harmonic generation (SHG) imaging on human basal cell carcinoma samples. In the dermis, basal cell carcinomas can be identified by masses of autofluorescent cells with relatively large nuclei and marked peripheral palisading. In the normal dermis, SHG from dermal collagen contributes largely to the multiphoton signal. However, within the cancer stroma, SHG signals diminish and are replaced by autofluorescent signals, indicating that normal collagen structures responsible for SHG have been altered. To better delineate the cancer cells and cancer stroma from the normal dermis, a quantitative MF to SHG index is developed. We demonstrate that this index can be used to differentiate cancer cells and adjacent cancer stroma from the normal dermis. Our work shows that MF and SHG imaging can be an alternative for Mohs' surgery in the real-time guidance of the secure removal of basal cell carcinoma.     

KBA显微镜成像系统的成像模拟及X光成像实验的研究

KBA显微镜是一种非轴对称、非共轴的掠入射成像系统。其结构复杂,调节精度要求很高,在实际成像实验操作中难以掌握其成像特性。利用光学设计软件模拟其成像,对系统的调节和成像分析提供有益的参考。利用光学设计软件ZEMAX模拟了KBA显微镜对点源的成像过程,给出了KBA显微镜成像系统的焦深约为1 mm,景深为50 mm左右。并且由模拟可知,掠入射角对成像的影响很大。对像素尺寸约10μm的探测设备,模拟得出KBA成像系统的空间分辨力上限为3μm左右。基于星光Ⅱ装置对周期为20μm的网格靶成像,获得了KBA显微镜较为清晰的X光图像。该项工作为进一步开展掠入射成像系统的研究奠定了基础。     

Electrochemically driven organic monolayer formation on silicon surfaces using alkylammonium and alkylphosphonium reagents

The functionalization of silicon surfaces with organic monolayers, bound through Si–C bonds, is an area of wide interest due to the technological promise of organosilicon hybrid devices, but also to investigate fundamental surface reactivity. In this paper, the use of alkylammonium and alkylphosphonium cations as sources of organic moieties to bind to hydrogen-terminated flat and porous silicon is demonstrated. Tetraalkylammonium, tetraalkyl/arylphosphonium reagents, and alkyl pyridinium salts can be utilized, but trialkylammonium salts cannot as they yield substantial surface oxidation. Under electrochemical conditions, either potentiostatic or galvanostatic modes, alkyl groups derived from the ammonium or phosphonium salts are grafted to the silicon surface and are bound through Si–C bonds. Covalent attachment of the organic monolayers to the surface was demonstrated by XPS, AFM scribing, and FTIR. The mechanism may proceed via reduction of the ammonium salt yielding alkyl radicals, R, which may be reduced to R⁻ and attack surface Si–Si bonds, leading to Si–C bonds, or the formation of silyl anions (≡Si⁻) under the cathodic conditions followed by nucleophilic attack on the trialkylammonium cation.     

Construction and cosmic-ray test of the new inner drift chamber for BESIII

A new inner drift chamber has been built which can replace the aged part of the BESIII drift chamber when needed. The design of the new inner drift chamber can minimize the ineffective area in the very forward and backward region and hence reduce the background event rate. With this design, the new inner drift chamber is expected to have a longer lifetime and improved performance due to the lower occupancy. The endplates and the cylinder were machined with high precision. Wire stringing was performed after the mechanical structure was assembled, and good quality of wire stringing was ensured by measurement of the tension and leakage current of the wires. After completion of the physical construction of the new chamber, a cosmic-ray test was carried out to test its performance. The results of the cosmic-ray test show that the new inner chamber achieves a spatial resolution of127 μm and a d E/dx resolution of 6.4%, which satisfies the design specifications.     

NⅡ离子2p4f—2p3d辐射跃迁概率的理论研究

在全相对论理论框架下，利用多组态Dirac-Fock(MCDF)方法，系统计算了NⅡ离子2p4f—2p3d的辐射跃迁概率，得到的结果与已有实验值符合很好.具体计算中，详细分析了相对论效应、电子关联、弛豫效应、Breit相互作用和量子电动力学(QED)效应对能级精细结构及辐射跃迁概率的影响.结果表明：相对论效应、电子关联和弛豫效应对NⅡ 2p4f-2p3d辐射跃迁概率有很重要的影响,考虑了这些效应后计算值得到明显改善.     

A high sensitivity spectrometer with tunable diode laser for ambient methane monitoring

Tunable diode laser absorption spectroscopy (TDLAS) has been widely employed in atmospheric trace gases detection. In the measurement of these trace gases, harmonic detection combined with a multi-pass white cell could remarkably enhance the detection sensitivity. In this paper, a portable TDLAS system built specifically for long time monitoring methane in the atmosphere is introduced. The detection limit is below 100 ppb that is enough for the monitoring of ambient methane, and the long time monitoring results obtained in Beijing are given, which is well coincident with that of the Fourier transform infrared (FTIR) spectroscopy.     

Multiparty-controlled quantum secure direct communication

A theoretical scheme of a multiparty-controlled quantum secure direct communication is proposed. The supervisor prepares a communication network with Einstein-Podolsky-Rosen pairs and auxiliary particles. After passing a security test of the communication network, a supervisor tells the users the network is secure and they can communicate. If the controllers allow the communicators to communicate, the controllers should perform measurements and inform the communicators of the outcomes. The communicators then begin to communicate after they perform a security test of the quantum channel and verify that it is secure. The recipient can decrypt the secret message in a classical message from the sender depending on the protocol. Any two users in the network can communicate through the above processes under the control of the supervisor and the controllers. The text was submitted by the authors in English.     

奇相干光源的测量设备无关量子密钥分配研究

刻画了奇相干光源的光子数分布特征,研究了奇相干光源下诱骗态测量设备无关量子密钥分配系统的密钥生成率与安全传输距离的关系,推导了奇相干光源下的计数率下界和误码率上界.仿真结果表明,奇相干光源光子数分布中多光子脉冲的比例低于弱相干光,可以有效提高诱骗态测量设备无关密钥分配系统的最大安全通信距离,为实用的量子密钥分配实验提供了重要的理论参数.