Indirect fluorescence detection of amino sugars with the use of copper complexes of tryptophan and its analogues following high-performance liquid chromatographic separation

A simple, indirect fluorescence detection method has been developed for detecting specific mono-amino sugars (D-glucosamine, D-galactosamine, D-mannosamine) following chromatographic separation. The eluting amino sugars release L-tryptophan (L-Trp) from a copper-tryptophan complex which is introduced postcolumn. Analyte detection is based on measuring the increase in L-Trp fluorescence, which is quenched when complexed with copper. Two tryptophan analogues, 5-hydroxy-L-tryptophan (5-HTP) and DL-5-methoxytryptophan (5-MTP), were also evaluated as postcolumn reagents. 5-MTP was found to be a suitable alternative to L-Trp for the detection of these mono-amino sugars. Detection limits for D-glucosamine, D-galactosamine, and D-mannosamine are in the range of 0.15-0.30 nmol injected.     

Correlations of Active Galactic Nuclei with Microquasars

Correlations of active galactic nuclei (AGNs) with microquasars are discussed based on the coexistence of the Blandford-Znajek (BZ) and magnetic coupling (MC) processes (CEBZMC) in black hole (BH) accretion disk.The proportions of several quantities of BH systems for both AGNs and microquasars are derived by combining the observational data with CEBZMC. It is shown that the square of the magnetic field at the BH horizon is inversely proportional to the BH mass, while the accretion rate of the disk is proportional to the BH mass. In addition, the very steep emissivity indexes from the recent XMM-Newton observations of the nearby bright Seyfert 1 galaxy MCG-6-30-15 and the microquasars XTE J1650-500 are well fitted by considering the MC effects on the disk radiation. These results suggest strongly the correlations of A GNs with microquasars.     

Correlations of Active Galactic Nuclei with Microquasars

Correlations of active galactic nuclei （AGNs） with microquasars are discussed based on the coexistence of the Blandford-Znajek （BZ） and magnetic coupling （MC） processes （CEBZMC） in black hole （BH） accretion disk. The proportions of several quantities of BH systems for both AGNs and microquasars are derived by combining the observational data with CEBZMC. It is shown that the square of the magnetic field at the BH horizon is inversely proportional to the BH mass, while the accretion rate of the disk is proportional to the BH mass. In addition, the very steep emissivity indexes from the recent XMM-Newton observations of the nearby bright Seyfert 1 galaxy MCG-6-30-15 and the microquasars XTE J1650-500 are well fitted by considering the MC effects on the disk radiation. These results suggest strongly the correlations of A GNs with microquasars.     

Surface‐enhanced Raman spectra of melamine and other chemicals using a 1550 nm (retina‐safe) laser

Many trace chemical analyses are being transitioned from the lab to the field, among which is surface‐enhanced Raman spectroscopy. Although initial portable Raman analyzers primarily employ 785 nm laser excitation, recent studies suggest longer wavelengths, with an appropriate surface‐enhanced Raman‐active substrate, may provide equal sensitivity. Furthermore, 1550 nm excitation may provide added safety for the user, in that permanent retina damage does not occur. Here, we show that a reasonable enhancement factor can be obtained for melamine using 1550 nm laser excitation that is nearly equivalent to those obtained using 785 and 1064 nm laser excitation. We also demonstrate that a number of other chemicals of interest can be measured by 1550 nm surface‐enhanced Raman scattering, albeit only modest sensitivity is achieved because of instrument limitations, not enhancement factors. Copyright © 2011 John Wiley & Sons, Ltd.     

Single red up-conversion luminescence of Er sensitized layered Y2Ti2O7 phosphor

High color purity red emission with single band successfully achieved in a new Er³⁺, Tm³⁺ co-doped Y₂Ti₂O₇ system under 1550 nm excitation, value of red to green emission ratio of the samples is more than 10³. Efficient up-conversion luminescence can be obtained while the ⁴I_13/2 level of Er³⁺ pumped by 1500 nm directly based on the large absorption section and long luminescence lifetime, and red emission composition will greatly enhanced by co-doping with Tm³⁺ ions, color purity of red emission under 1550 nm excitation is much higher than that of 980 nm. The quenching concentration of Er³⁺ ions is up to 28 mol% in Y₂Ti₂O₇ rely on the layer distribution of cations, which can further improve the red emission color purity.     

Infrared-to-visible upconversion luminescence of Er doped barium-natrium-yttrium-fluoride phosphor

Infrared-to-visible upconversion luminescence has been investigated in Er³⁺-doped barium-natrium-yttrium-fluoride phosphor (Ba_xNa_yY_zF_2x+y+3z+3m:Er_m) with different cation concentrations. Intense upconversion emissions around 530, 550, and 660 nm corresponding to the ²H_11/2, ⁴S_3/2, and ⁴F_9/2 transitions, respectively to the ⁴I_15/2 ground state were observed when excited by CW laser radiation at 1550 nm. We adopted the low-temperature combustion synthesis (LCS) method to decrease the phosphor particle size to 40-70 nm in order to couple to the photosensitive surface of CCD. The effect of the amount of carbamide on the particle size and the upconversion luminescence intensity was analyzed. The upconversion luminescence mechanism was studied by the log-log plot of intensity-power.     

1550nm-VCSELs在偏振保持光反馈和正交光注入下的偏振转换特性

基于自旋反转模型,研究了1550 nm垂直腔面发射激光器(1550 nm-VCSELs)在偏振保持光反馈和正交光注入下的偏振转换特性.结果表明:正交光注入下的从激光器会随着注入强度的增加产生偏振转换.在归一化注入电流较小时,改变反馈强度,会使从激光器发生偏振转换的注入强度出现规律不同的变化;改变频率失谐,会使从激光器发生偏振转换的注入强度出现规律相同的变化.     

1550 nm垂直腔面发射激光器的特征参量随温度的变化

在采用自旋反转模型分析垂直腔面发射激光器（VCSELs）动力学行为的过程中,为了正确预测VCSELs的动力学行为,需要准确给出自旋反转模型中光场衰减速率k、总反转载流子衰减速率γ_N、线性二向色性系数γ_a、线性双折射系数γ_p、自旋反转速率γ_s和线宽增强因子α这6个特征参量.本文对1550 nm VCSELs在自由运行和平行光注入下的输出特性进行实验分析,获取了这6个特征参量的值,并着重研究了当激光器温度在10.00–30.00 ℃范围内变化时,这6个特征参量呈现的变化趋势.研究结果表明,随着温度的逐渐升高,γ_p整体呈现逐渐增加的趋势,γ_a,γ_s,γ_N和k呈现复杂的变化趋势,而α则呈现逐渐减小的趋势.     

Power-induced polarization switching and bistability characteristics in 1550-nm VCSELs subjected to orthogonal optical injection

The polarization switching(PS) and polarization bistability(PB) characteristics of a 1550-nm vertical-cavity surfaceemitting laser(VCSEL) subjected to orthogonal optical injection are systematically investigated.The simulated results show that the PS and polarization-resolved nonlinear dynamical states of the VCSEL are critically dependent on the changing paths of the injected power.The polarization dynamics for different scanning directions of the injected power is presented to explain the polarization evolution during the formation of PS.In the case of forward scanning injected power,with the increase of frequency detuning level between the VCSEL and the injected light,the injected power required for PS gradually increases for negative frequency detuning but exhibits fluctuations for positive frequency detuning.In the case of reversely scanning injected power,the injected power required for PS displays fluctuant changes within the whole frequency detuning range.Specifically,PS may disappear under certain negative frequency detuning and large bias current.Furthermore,the hysteresis width as a function of the frequency detuning is calculated,and the regions for the appearance and disappearance of PB have been determined in the parameter space of the bias current and frequency detuning.     

偏振保持光反馈下1550 nm垂直腔面发射激光器的非线性动力学特性研究

基于自旋反转模型,研究了1550 nm垂直腔面发射激光器(VCSELs)在偏振保持光反馈下的非线性动力学特性.结果表明:自由运行的1550 nm-VCSELs在电流增加的过程中,发生偏振转换所对应的电流值与内部参数的取值有关,随着有源介质线性色散效应系数γ_a的增大,偏振开关的转换点所对应的电流值将增加;偏振保持光反馈的引入将导致1550 nm-VCSELs中自由运行时的主导模(Y偏振模式)在不同电流下呈现不同动力学状态,引起另外一个模式(X模式)激射,两个模式的平均输出功率随电流的增加总体呈现增加的趋势,但伴随着起伏;反馈时间取不同值时,1550 nm-VCSELs的输出随着反馈强度的增大经历倍周期、准周期或阵发混沌等多种通向混沌的演化途径.