污泥内层和外层胞外聚合物的三维荧光光谱特性研究

运用三维荧光光谱技术对污泥LB-EPS和TB-EPS的荧光特性进行了研究.实验结果表明,在污泥LB-EPS和TB-EPS中都有三个明显的荧光峰,分别为Peak B(λex/λem=270～280 nm/345～360 nm),Peak C(λex/λem=330～340 nm/410～430 am)和Peak D(λex/λem=390 nm/450～470 nm).其中Peak B为类蛋白荧光(Protein-like)、Peak C为可见区类富里酸荧光(Visible fulvic-like)、Peak D为类腐殖酸荧光(Humic-like).从各荧光峰的荧光强度来分析,LB-EPS和TB-EPS中的主要成分都为类蛋白,然后依次为富里酸和腐殖酸.浓度和pH值对污泥LB-EPS和TB-EPS的三维荧光特性都有很大的影响,但影响程度略有区别,表明作为外层的胞外聚合物,LB-EPS表现出与TB-EPS不全相同的化学结构.     

石化废水的三维荧光光谱特征

石化废水是我国的主要工业废水之一,水量大、污染重.废水含有大量荧光物质,它的荧光光谱可以展现有机物组成,就像指纹一样与水样一一对应,被称为水质荧光指纹,简称水纹.论文通过对我国某大型石化企业的废水的三维荧光光谱特征的研究,揭示出石化废水荧光指纹丰富的特点,它含有近10个荧光峰,其中激发波长、发射波长(λex/λem)=...     

北京城市水体的三维荧光特征

基于三维荧光光谱的水质荧光指纹法已经逐渐显示出作为水体有机物的新型表征方法的价值.本文研究了北京的城市水体的三维荧光指纹.结果表明,北京城市水体的荧光指纹可以分为3种类型:Ⅰ型有2个荧光峰,其中心分别位于λex/λem=275～280/340 nm与225～230/340 nm附近,此类水体数量最多;Ⅱ型的两个荧光中心...     

电芬顿降解苯乙酮过程中有机物三维荧光特征的变化规律

采用荧光光谱技术检测分析了苯乙酮在电芬顿处理过程中的三维荧光光谱特征变化规律,研究了苯乙酮的三维荧光特征及其指纹特征,对苯乙酮去除率和荧光峰强度变化进行线性拟合研究.结果表明,苯乙酮具有两个荧光峰,分别在λEx/Em=270/305 nm(Peak A)和λEx/Em=215/305 nm(Peak B)处,且荧光指纹...     

制革废水处理过程溶解性有机物的光谱特性研究

制革工业是我国国民经济的传统产业,制革废水已成为工业废水的重要组成部分。现阶段对于制革废水的研究多关注于进水和出水的水质状况,对于废水处理过程溶解性有机物(DOM)的转化规律和净化行为涉及很少。通过紫外光谱和三维荧光光谱跟踪识别制革废水不同处理工段水体DOM的生成特性,尝试建立总荧光强度与水质参数的线性关系。结果表明：废水DOM的吸光度随着紫外波长的增加先上升后下降,最大吸收峰位于230 nm附近。A₂₅₃/A₂₀₃比值和SUVA₂₅₄的参数值先增大后减小,暗示了废水游离取代基和芳环取代基种类和数量的变化。废水原水荧光峰主要出现在λ_ex/em=320～350/440～460和λ_ex/em=270～300/390～420区域,分别归属为可见光区类腐殖酸荧光峰和可见光区类富里酸荧光峰。随着废水处理过程的进行,相继检测到类腐殖酸荧光峰蓝移(水解酸化池)、类色氨酸荧光峰(λ_ex/em=290/340,二级生化池)、弱荧光峰(λ_ex/em=350/520,四级生化池)以及荧光特性趋于稳定(二沉池和出水口)等现象,证实了废水有机物的降解特性和生成规律对荧光图谱的影响。制革废水总荧光强度去除率与总有机碳去除率的线性关系更好,相关系数r为0.835 5。紫外光谱和荧光光谱能在一定程度上揭示制革废水的净化规律和机制。     

炼油废水的荧光指纹特征

荧光有机物携带了有机物总量和组成信息,可作为新型水质参数来弥补COD和BOD等不能表达有机物组成的不足。炼油废水是典型的难降解工业废水,含有大量有毒化合物。我国某大型炼油企业废水的三维荧光光谱的研究结果表明,炼油废水的荧光光谱与水样一一对应;荧光强度很高,主要由λex/λem=270/300nm,220/300nm和230/350nm附近的荧光峰叠加而成,其中270/300nm的荧光强度最大,220/300nm稍弱;各峰的位置和荧光强度对于炼油废水是稳定的。炼油废水的荧光包含了产物和原料的信息。苯酚对270/300nm,220/300nm附近的荧光峰的荧光强度贡献显著,而二氯苯和苯等其他单环化合物对这两峰可能也有贡献。230/350nm附近的荧光峰可能与烷烃和苯有密切关系。各峰的位置和荧光强度可以作为炼油生产以及废水处理厂来水是否正常的判据。     

三维荧光光谱法测定水中氯苯的研究

对三维荧光光谱法测定水中氯苯(简称CB)进行了研究.研究表明,CB的三维荧光谱图只有一个荧光峰,该峰位于激发波长(λex)210～240 nm、发射波长(λem)330～370 nm范围内.当CB溶液浓度为0.002～0.05 mg·L-1时,λex/λem为225/340 nm处荧光强度最大.在此波长处,荧光强度与浓度呈很好的线性相关,相关系数为0.999 67,表明三维荧光光谱法可用于定量分析水中的CB.该方法在置信水平为90%时的检出限为3.68×10-6mg·L-1,标准偏差为0.04%.     

径流污染对城市污水处理过程的DOM荧光特性影响研究

结合污水处理流程,分别采集重庆市某污水厂晴天和雨天的污水,用三维荧光光谱分析了污水中的溶解性有机物(dissolved organic matter,DOM)的荧光特性。结合DOM的DOC ( dissolved organic carbon, DOC)、COD(chemical oxygen demand, COD)、荧光指数(f_450/500)和紫外区富里酸和可见区富里酸的荧光强度比值r(A, C)的变化特征,分析了雨天径流污染对污水DOM 的影响。实验表明：该污水厂DOM的荧光指纹与典型城市生活污水有较大差异,主要成分为低激发波长类色氨酸(Peak S), 长激发波长类色氨酸(Peak T)次之;A2/O工艺对雨天和晴天的类蛋白物质的去除效果相当,但是雨天的类富里酸以及DOC和COD的去除率较晴天高, 经过生化处理后的荧光峰均发生细微的红移;晴天和雨天污水的DOM 荧光指纹差异明显,雨天紫外富里酸(Peak A)荧光中心由晴天的240～248/390～440 nm蓝移到240～250/370～400 nm。虽然晴天和雨天的DOM种类相同,但是雨水径流使富里酸的来源复杂,组分比例发生了较大变化,雨天色氨酸(Peak S)的比例下降了10%,紫外富里酸(Peak A)的比例上升7%。     

基于荧光分析法和APTLD相结合的多环芳烃的检测

为准确进行浓度检测,用Savitzky-Golay(SG)多项式曲面平滑法去除三维荧光光谱数据的冗余信息,分别采用平行因子法(PARAFAC)算法和交替惩罚三线性分解(APTLD)算法对光谱数据进行分解。设计多环芳烃类污染物的检测实验,分析了芴(FLU)、苊(ANA)及两者混合溶液的荧光光谱特性。FLU溶液在λ_(ex)/λ_(em)=302/322 nm处存在一个明显的荧光峰,并且存在连续侧峰。ANA溶液存在两个荧光峰,分别为λ_(ex)/λ_(em)=290/322 nm和λ_(ex)/λ_(em)=290/336 nm。在激发波长200～370 nm扫描范围和发射波长240～390 nm扫描范围内,FLU和ANA荧光光谱重叠严重。结果表明,两种算法均能分辨出FLU和ANA,并取得了很高的回收率,但APTLD算法的检测效果更好。     

城市污水的三维荧光指纹特征

传统表征有机物含量的水质参量如化学需氧量(COD)和生化需氧量(BOD)等只能表示总量,无法展示有机物成分.荧光光谱可以作为一种新型的水质表示方法,它像指纹一样与水样一一对应,被称为水质荧光指纹.采用三维荧光光谱(EEM)技术研究了城市污水荧光指纹特征,结果表明城市污水具有4个典型荧光区,各区的荧光中心、强度以及1区荧光中心λex=280 nm,λem=340 nm与2区荧光中心λex=225 nm,λem=340 nm的荧光强度的比值可以作为城市污水的主要荧光指纹特征.荧光指纹包含了大量污染物信息,通过与城市污水中典型污染物质的荧光光谱的比对,初步确定了各荧光区可能的荧光信号来源.荧光指纹法可表示有机物类型和含量,可作为化学需氧量和生化需氧量等参量的有益补充.     

Influence of a layered polarization of piezoelectric ceramics on shear-horizontal surface-wave propagation

This paper presents the results of theoretical analysis concerning the propagation of shear-horizontal (SH) surface waves on a piezoelectric ceramic with a surface layer of piezoelectric properties different from those in the substrate. Phase velocity and amplitude distributions of the SH surface waves were calculated for the standard piezoelectric ceramic PZT-4. Some practical applications in acoustoelectronics are suggested.     

High-intensity brillouin scattering from parametrically excited phonons in FeBO3

The saturation of the ferromagnetic resonance in FeBO₃ is due to the parametric decay into short wavelength phonons of half the exciting frequency. These phonons are observed using the technique of inelastic light scattering. Their intensity is so high (10⁵ above thermal level) that the scattered light can be observed visually. Light scattering and parametric decay selection rules result in well defined scattering angles. The analysis of these directions allows the evaluation of anisotropic sound velocities.     

Extensions of the scattering-object function and the pulser-receiver impulse response in the field II formalism

The pulse-echo impulse-response format in the Field II formalism is generalized to separately located transmitter and receiver. To first order in sound velocity and density perturbations, identical results for the scattering-object function are obtained for the Morse-Ingard and the Chernov formulation in both the temporal and frequency domains: f(s)=-[2Delta(c/c)+(Delta(rho/rho))(1-cos(theta))] where for ultrasonic pulse-echo or transmission modality, cos(theta) approximately -1 or +1, respectively.     

Characteristics of thin gate dielectric in a rapid thermal processing machine and temperature uniformity studies

Rapid Thermal oxidation (RTO) of silicon has been investigated in the temperature range 1000° to 1250°C for an oxidation time of 5 to 60 s. The fairly extensive kinetics data show that linear growth occurs with an activation energyE _a of 1.4 eV. Rapid thermal nitridation of SiO₂ (96 Å) has been performed at three different temperatures: 1150°, 1200°, and 1250°C for a nitridation time up to 150 s. The characteristics of both materials have been investigated by capacitance-voltage, current-voltage, high resolution transmission electron microscopy and Auger spectroscopy. The results will be discussed with special emphasis on breakdown field statistics. The influence of Rapid Thermal Annealing (RTA) on the characteristics of both oxide and nitrided oxide will also be presented. A simulation model of a rapid thermal processing machine is presented with particular attention to the formation of slip lines. The theoretical results are in good agreement with those obtained experimentally.     

Fabrication of carbon nanoflowers by plasma-enhanced chemical vapor deposition

Two and three-dimensional (2D and 3D) carbon nanoflowers have been prepared on silicon (1 1 1) substrates by plasma-enhanced chemical vapor deposition, using CH₄, H₂ and Ar as reactive gases in the presence of Fe catalyst. The flower patterns are controlled by the flux ratio of the carrier gas, the reaction pressure and the growth temperature. Through observation by scanning electron microscopy, we find that the 2D carbon nanoflowers are formed by various nanoleaves while the 3D flowers are composed of hundreds of nanofibers. The former is related closely to the flux ratio of gas and the reaction pressure, while the latter depended mainly on the growth temperature. The nucleation and growth process of the nanoflowers seem to be a vapor/liquid/solid mechanism.     

A SQUID susceptometer for fields up to 8.5 tesla

A SQUID susceptometer working in fields up to 8.5 T has been built. Calibration measurements show a mass susceptibility sensitivity of 6.3 10⁻¹³ m³·kg⁻¹ (for a one gram sample) and an excellent reproducibility. The temperature of the samples can be changed from 1.6 to 300 K by a regulated continuous He flow. System design, strategy for minimizing the sources of noise and measurement techniques are described. A test measurement showing the martensitic transition of V₃Si in 8.5 T is presented.     

Differential evaluation of the Hall effect in silicon with oxygen-related donors

Three kinds of samples were used to form Co suicides by thermal annealing: firstly, a Co film of about 370 Å thick, evaporated on a (100) single crystal Si (Si ^c /Co); secondly, an evaporated boron-containing Si (Si ^e (B)) layer on the top of the first sample (Si ^c /Co/Si ^e (B)). The last sample is in the Co film of the first sample we deposited a Si^e(B) layer (Si ^c /Co/Si ^e (B)/Co). A laterally uniform CoSi₂ layer can be formed from the second and the third samples by annealing at 450 °C. In the first sample, the CoSi₂ can be formed only at temperatures above 500 °C and the disilicide is laterally less uniform than in the second and third samples. The Schottky barrier heights of the three samples derived from the forward and reverse I–V characteristics show that the barrier height is 0.01–0.02eV higher in the uniform case than in the nonuniform case.     

Thermal conductivity of selenium doped with indium and iodine in the solid and liquid states

We have measured the thermal conductivity in both the solid and liquid states for two amorphous samples. The first was selenium doped with indium and the second was selenium doped with iodine. The concentration of In and I in both samples was 50000 ppm in weight, which is equal to 3.33% for indium and 3.02% for iodine additives in atomic percent. The measurements were taken in the temperature range from 100 to 470°C and were carried out using the concentric cylindrical wall. It was found that the thermal conductivity of both samples is of the phonon type; its temperature dependence follows the relation K _ph T ^–1, and can be explained by the influence of thermal effects on the lattice structure.     

Brightness enhancement of slow positron beams

A study on the horizontally LPE-grown La, Ga: YIG films is presented. With the spin wave resonance technique the ratio of the saturation magnetizations of the bulk and transient layer has been measured. The average saturation magnetization was determined by means of a vibrating sample magnetometer and the Ga concentration by x-ray fluorescence analysis. These data are compared with the growth rates of both the transient and the bulk layer. A systematic dependence of the magnetization on the growth rate is found.     

Light amplification due to free and localized exciton states in ZnCdSe GRINSCH structures

Received: 27 April 1998/Accepted: 30 April 1998