Biotinyl-Glucose-6-Phosphate Dehydrogenase Preparation,Kinetics, and Modulation by Avidin

The kinetics of free glucose-6-phosphate dehydrogenase (G-6-PDH), biotinylated G-6-PDH, and biotinylated G-6-PDH complexed with avidin were investigated. The kinetics of the free enzyme were consistent with a sequential rather than a ping-pong mechanism. The kinetics of the biotinylated enzyme were similar to that of the free enzyme, but the kinetic constants were different; theK _m value for NADP was halved, whereas theK _m for G-6-P decreased only slightly. In the presence of avidin, theK _m of biotinylated G-6-PDH for G-6-P nearly doubled whereas theK _m for NADP did not change significantly. Avidin complexed with biotinylated G-6-PDH inhibited the enzyme from acting. Based upon these reactions, it was possible to devise assays for either free biotin or free avidin using biotinylated G-6-PDH as the indicator enzyme. Concentrations of biotin between 40 and 60 mg/mL, or of 25–95 Μg/mL of avidin could be measured within 2 min through the use of biotinylated G-6-PDH.     

A2SnS5: A Structural Incommensurate Modulation Exhibiting Strong Second‐Harmonic Generation and a High Laser‐Induced Damage Threshold (A=Ba,Sr)

Structural modulations have been recently found to cause some unusual physical properties, such as superconductivity or charge density waves; however, thus‐induced nonlinear optical properties are rare. We report herein two unprecedented incommensurately modulated nonlinear optical sulfides exhibiting phase matching behavior, A₂SnS₅ (A=Ba, Sr), with the (3+1)D superspace groups P2₁2₁2(00γ)00s or P2₁(α0γ)0, featuring different modulations of the [Sn₂S₇]_∞ belts. Remarkably, Ba₂SnS₅ exhibits an excellent second harmonic generation (SHG) of 1.1 times that of the benchmark compound AgGaS₂ at 1570 nm and a very large laser‐induced damage threshold (LIDT) of 8×AgGaS₂. Theoretical studies revealed that the structural modulations increase the distortions of the Sn/S building units by about 44 or 25 % in A₂SnS₅ (A=Ba, Sr), respectively, and enhance significantly the SHG compared with α‐Ba₂SnSe₅ without modulation. Besides, despite the smaller E_g, the A₂SnS₅ samples exhibit higher LIDTs owing to their smaller thermal expansion anisotropies (Ba₂SnS₅ (1.51)<Sr₂SnS₅ (2.08)<AgGaS₂ (2.97)).     

Confocal scanning microfluorometry of dual-labelled specimens using two excitation wavelengths and lock-in detection technique

A new technique for simultaneous recording of multiple fluorophores has been implemented in a confocal scanning laser microscope. Dual excitation wavelengths, intensity-modulated at different frequencies and two lock-in amplifiers tuned to the corresponding frequencies are used. In this way two fluorophores can be independently, albeit simultaneously, excited. This technique, Intensity-modulated Multiple-beam Scanning (IMS) microfluorometry, has the potential to virtually eliminate the cross-talk between fluorophores that often occurs when recording multiple-labelled specimens. Furthermore, it will offer simultaneous information about both the excitation and emission spectra of the fluorophores used. Also, variations in decay time over the image area can be studied independently and simultaneously for two fluorophores.     

Distributed spatial media-based modulation for relay networks with RF mirrors

A novel distributed spatial media-based modulation scheme is proposed in this paper by cleverly utilizing distributed spatial modulation (DSM) and media-based modulation (MBM) principles. This proposed scheme is referred to as distributed channel modulation (DCM) for relay networks. In this scheme, decode-and-forward relaying protocol is adopted, and the channel states are exploited for transmitting extra information bits by using a number of radio frequency (RF) mirrors that are placed near each relay. To provide a fair comparison with the conventional state-of-the-art schemes, the symbol error rate (SER) performance of DSM scheme is evaluated. Besides, a low complexity detection technique known as iterative maximum ratio combining (i-MRC) is used in order to reduce the receiver complexity of the proposed scheme. Simulation results demonstrate that the proposed DCM scheme significantly outperforms DSM scheme for the same average rate. It is also shown that there is a negligible degradation in the SER performance of the proposed DCM scheme when i-MRC detection is used as compared to the performance with maximum likelihood (ML) detection. Furthermore, a significant reduction in the receiver complexity is achieved by using i-MRC detection technique in contrast to the results with ML detector. It has been also revealed that the proposed DCM scheme shows a performance drop of about 3 dB when the availability of an imperfect channel state information (CSI) is assumed with the presence of channel estimation errors (CEEs). Finally, simulation results have confirmed the analytical findings.     

磁绝缘线振荡器中空间电荷的调制

 首次研究了磁绝缘线振荡器中射频场（包括辐射波场和空间电荷波场）对空间电荷的调制,得到了在饱和时谐波电流一阶分量的公式。这个公式表明：考虑空间电荷波时,在小信号和辐射波与空间电荷波同相的条件下,它将增强谐波电流。在大信号时,情况不确定;谐波电流一阶分量将随二极管上电压的增加而增加,随运行频率和饱和长度的增加而减少。     

Cl+HN3产生NCl(a1Δ)和NCl(b1∑)的实验研究

对利用微波放电直接解离Cl2生成Cl, Cl与HN3反应生成NCl(a1Δ )和NCl(b1∑)的过程进行了实验研究。得到了较强的NCl(a1Δ 和NCl(b1∑)自发辐射光谱,考察了Cl2流量和He/Cl2配比对NCl(a1Δ 和NCl(b1∑)生成的影响。发现对于一定的He流量,Cl2流量对NCl(a1Δ 和NCl(b1∑)生成的影响存在一最佳范围,而最佳He/Cl2配比不是一定值,而是随He流量升高而变大,在实验所考察的He流量范围（5~40 L/min）内,最佳He/Cl 2配比在30∶1~100∶1之间。     

微型Nd：YVO4激光器在碘分子调制转移光谱中的应用

以半导体激光器抽运微型Nd:YVO4倍频激光器为光源获得碘分子在532nm处的光外差调制转移光谱信号,并对获取最佳稳频信号的实验条件进行了讨论。     

Diode laser spectroscopy of He,N2 and air broadened water vapour transitions belonging to the (2ν1 + ν2 + ν3) overtone band

The line shape parameters of rovibrational transitions of water vapour belonging to the (2ν₁ + ν₂ + ν₃) overtone band due to collisions between absorber molecules and noble gas helium have been measured in the spectral range between 11988.494 cm^?1 and 12218.829 cm^?1 using NIR diode laser spectrometer. In addition nitrogen and air broadening effects on some water vapour transitions belonging to the same band have also been studied. Wavelength modulation spectroscopy along with phase sensitive detection technique are used to record first derivative (1f) signal of buffer gas broadened water vapour transitions. Observed line shapes are fitted to standard Voigt profiles by non-linear least squares fitting program to extract the line shape parameters, like line strength and pressure broadening coefficients. The broadening effects induced by different types of buffer gases on water vapour line shapes are compared. Rotational quantum number (J) dependence of broadening coefficients of water vapour transitions is also examined.     

超短光脉冲在光纤中传输计算机模拟计算的研究

本文提出了一种研究超短光脉冲在介质中传输特性的简单的计算机计算方法.用该方法得到了正色散光纤中的频率调制、频谱加宽和方波自成形,以及负色散光纤中的一、二、三阶孤子传输.其数值计算结果与解非线性薛定谔方程的数值结果完全一致.     

Improved spatial phase detection for profilometry using a TDI imager

Performance of a time delay and integration (TDI) imager is analogous to a drum/periphery camera. Coupled to a modulated line generating laser diode, it is possible to use a TDI imager to encode the shape profile of a rotating cylindrical object as deformed gratings in a digital image. Among the various methods for extracting the phase from a deformed grating, the spatial phase detection (SPD) method is fast and easy to use. Errors are introduced in this method if the phase gradient is high over a grating interval. Here we propose a method to reduce the phase gradient by using a TDI feature which makes it possible to record images at variable lateral magnification.