Supercritical fluid technologies in the chemistry of wood and its components

The advantages of application of supercritical fluid technologies at the stages of complex wood and plant processing are analyzed based on the modern concept of lignin-carbohydrate matrix formation.     

声表面波气相色谱仪及其应用*

声表面波气相色谱仪具有灵敏度高、色谱柱升温速度快(~20?C/s)、体积小等特点,可实现痕量气体的广谱(挥发和半挥发性有机物)、快速(5 min)、高灵敏度(ppb～ppt级)现场分析,在公共安全、环境监测、食品和药品检测等方面有广阔的应用前景。该文从仪器响应的机理分析、检测器设计、仪器研制及应用等方面出发介绍了我们的研究进展情况。     

独立成分分析及其在图像处理中的应用

独立成分分析是一种新的信号处理技术,在数字图像处理的诸多方向均表现出其独特性。对独立成分分析(ICA,Independent Component Analysis)及其在图像处理中的应用进行了综述。简要介绍了独立成分分析的数学模型,给出了极大化非高斯性的ICA估计方法、极大似然ICA估计方法、极小化互信息ICA估计方法的目标函数及其优化算法;对ICA在像素级图像融合、运动目标检测、人脸检测及特征提取、大脑信号和图像分析、数字水印、有噪图像分离等方向的应用研究进行了评述,进而显示ICA的应用价值和发展空间。     

脑电信号的标度分析及其在睡眠状态区分中的应用

脑电信号具有长程幂律相关性及多重分形的标度特性,并随生理病理状态改变.本文首次针对睡眠脑电信号应用单重分形去趋势波动分析(detrended fluctuation analysis,简记为DFA)方法与多重分形奇异谱对睡眠脑电信号的标度特征进行系统的对比研究.发现DFA标度指数α对于不同导联和样本组间的差异较为敏感,随睡眠状态的变化不规律;而多重分形奇异强度区间Δα随睡眠状态的变化更为规律,睡眠Ⅰ期至Ⅳ期不断增大,并且导联间差异和样本组间差异均较小.多重分形Δα参数更适合作为判定睡眠状态的定量参数.     

Phase-resolved correlation and its application to analysis of low-coherence interferograms

A new signal-processing technique is proposed that involves a phase-resolved correlation method that one can use to determine the phase distribution of low-coherence interferograms. This method improves the sensitivity and resolution of low-coherence interferometers. The depth structure of an aluminum oxide-coated aluminum mirror was determined by use of a low-coherence interferometer with this method. Three signal peaks were successfully extracted from a noisy interferogram.     

Supercritical fluid thermodynamics from equations of state

Supercritical multicomponent fluid thermodynamics are often built from equations of state. We investigate mathematically such a construction of a Gibbsian thermodynamics compatible at low density with that of ideal gas mixtures starting from a pressure law. We further study the structure of chemical production rates obtained from nonequilibrium statistical thermodynamics. As a typical application, we consider the Soave-Redlich-Kwong cubic equation of state and investigate mathematically the corresponding thermodynamics. This thermodynamics is then used to study the stability of H₂-O₂-N₂ mixtures at high pressure and low temperature as well as to illustrate the role of nonidealities in a transcritical H₂-O₂-N₂ flame.     

Supercritical fluid micronization of risperidone pharmaceutical substance

A comparative study of the supercritical fluid micronization of risperidone pharmaceutical substance with an initial particle size of 50 to 100 μm by the RESS and SAS methods aimed at increasing the bioavailability of risperidone as a drug was performed. Both methods makes it possible to prepare risperidone particle of various forms, 5–20 μm in size. However, the SAS method is preferable, because in contrast to RESS, it does not cause contamination of risperidone with organic solvents used in both processes or any other impurities and also makes it possible to vary the shape and size of particles. It is shown that, during SAS micronization, the polymorphic form of risperidone changes from triclinic to monoclinic.     

Supercritical fluid extraction of pesticides from human hair followed by gas chromatography-mass spectrometric analysis

A supercritical fluid extraction process using supercritical carbon dioxide for the isolation of chlororganic and phosphororganic pesticides from human hair is developed. The effect of process parameters (temperature, pressure, duration) on the efficiency of pesticide extraction is studied. The gas chromatography-mass spectrometry technique is used for the quantitative analysis of pesticide concentration in hair.     

FeTe合金结构分析及其薄膜制备

利用固态反应法制备了名义成分为FeTe的合金, 采用X射线粉末衍射技术和Rietveld全谱拟合分析方法测定了其相组成和晶体结构. 研究表明,主相为Fe_1.08Te,空间群为P4/nmm,点阵参数 a = 3.8214(3) Å, c = 6.2875(3) Å, Z = 2, Fe原子占据2a和2c晶位, Te原子占据2c晶位. 利用脉冲激光沉积技术制备的FeTe薄膜超导转变起始温度为13.2 K,零电阻温度为9.8 K. 关键词： FeTe Rietveld结构精修 超导薄膜     

Ultrasonic preparation of cationic cotton and its application in ultrasonic natural dyeing

Cationization of cotton fabric was conferred by the sonicator reaction of cellulose with bromoacetyl bromide, followed by substitution of the terminal bromo groups by triethylamine. Experiments showed that the optimal volume of bromoacetyl bromide necessary to succeed the first stage was 0.4 mL. The order of weight gain for various processes indicates, ultrasound, 25 kHz > ultrasound, 40 kHz > mechanical stirring. Also, for the second stage the order of nitrogen contents indicates ultrasound, 25 kHz > ultrasound, 40 kHz > mechanical stirring. The structures of both untreated and cationic fibres were investigated by FTIR spectroscopy. Modified cotton fabric was subsequently dyed in both conventional and ultrasonic techniques with isosalipurposide dye isolated from Acacia cyanophylla yellow flowers. The effect of dye bath pH, ultrasonic power and frequency, dyeing time and temperature were studied and the order of K/S values indicates ultrasound, 25 kHz > ultrasound, 40 kHz > CH. ultrasound was also found to enhance the dye uptake and the overall fastness properties. Analysis of the sorption isotherms of isosalipurposide dye on cationic cotton fabric shows that the Languimir isotherm equation is best able to correlate the data.     

The preparation of optical fibre nanoprobe and its application in spectral detection

As an important component of scanning near-field optical microscope (SNOM), optical fibre nanoprobe has been applied to many fields extensively. A melt-stretched etching method is proposed to produce optical fibre nanoprobe with low cost. Firstly, optical fibre tip with micrometer-sized diameter is created by the melt-stretched measure. Next, it is dipped into hydrofluoric acid (HF), and a fine optical fibre nanoprobe will be made after a short-time etching. Owing to the taper structure of tip, it can be etched again in acid if a nanoprobe is not constructed when the first etching is completed. In addition, optical fibre nanoprobe is applied to spectral investigation, and the fluorescence spectroscopy of rhodamine B (Rh B) solution is collected by an optical investigation system with a bifurcated fibre.     

Closed form solution to a second order boundary value problem and its application in fluid mechanics

The Adomian decomposition method is used by many researchers to investigate several scientific models. In this Letter, the modified Adomian decomposition method is applied to construct a closed form solution for a second order boundary value problem with singularity.     

The GaAs probe tunneling method and its application to superconducting compounds and intermediate valence rare earth intermetallics

Thep-GaAs Schottky-barrier point-contact tunneling technique has been analyzed and characterized with respect to uniaxial pressure effects, surface contaminations and the background in the metal vs.p-GaAs tunnel spectra. The latter have been calculated assuming parabolic bands and it is shown that density of states effects are unimportant.The method has been applied to the superconducting compounds LaAl₂, YSe, ErRh₄B₄ and to the intermediate valence (IV) rare earth intermetallics YbAl₂, YbInAu₂, CeCu₂Si₂ and CeRu₂. No anomalies as suggested by asymmetries in metal point-contact spectra of IV intermetallics have been found. Moreover, no indication of a strongly renormalized tunneling density of states like in the semiconductor-like IV materials SmB₆, SmS and TmSe or in superconductors has been observed, except CeRu₂. For the IV superconductor CeRu₂ an energy gap 2=3.3±0.3 meV has been deduced from the tunnel spectra.Dedicated to B. Mühlschlegel on the occasion of his 60th birthdayWork supported by Deutsche Forschungsgemeinschaft, SFB125     

Simplified laser-speckle-imaging analysis method and its application to retinal blood flow imaging

Laser speckle imaging (LSI) is widely used to study blood flow at high spatiotemporal resolution. Several papers recently pointed out that the commonly used LSI equation involves an approximation that could result in incorrect data analysis. We investigated the impact of such an approximation and introduced a simplified analysis method to improve computation time. Flow phantom studies were performed for validation. Moreover, we demonstrated a novel LSI application by imaging blood flow of rat retinas under normal and physiologic-challenge conditions. Because blood-flow abnormality is implicated in many retinal diseases, LSI could provide valuable physiologic, and potentially diagnostic, information.     

Supercritical fluid extraction of 1,1-dimethylhydrazine from peaty soils

Supercritical fluid extraction of a highly toxic rocket-fuel component (1,1-dimethylhydrazine, UDMH) from peaty soils with carbon dioxide is proposed as a rapid method of sample preparation for ion-chromatographic analysis. Optimum conditions of extraction have been determined. The efficiency of the UDMH extraction can be improved by basic treatments of the soil sample and by the use of proper additives to SC CO₂ (cosolvents).     

Supercritical fluid encapsulation of acizol into aliphatic polyether microparticles

Encapsulation of pharmaceutical grade acizol (Acizol® pharmaceutical substance) into bioresorbable D,L-polylactide and polylactoglycolide microparticles using supercritical carbon dioxide has been studied. An effective way for formation of polymer fine powders (mean particle size of about 10–20 µm) containing up to 20 wt % of the bioactive component without any organic solvent used has been suggested. Raman spectroscopy with spatial resolution was employed to analyze the distribution of acizol throughout the volume of the individual polymer microparticles and to study the kinetics of its release into saline. The rapid release (40–80% of the total amount of the encapsulated substance) from the samples under study was observed during the first hour, and then it was followed by a gradual, almost linear release between the 4th and 14th days of the experiment, with the total release continuing up to 100%.     

The spectroscopy of ion-induced photon emission and its application to quantitative surface analysis

Experimentally observed photon spectra produced by ion bombardment of transition elements Sc, Ti, V, Cr, Fe, Ni, and Cu and Zn with Ar⁺ ions are very similar to arc spectra of these same elements, with respect to relative intensities of lines observed. Standard spectrochemical analysis techniques, based on the assumption of local thermodynamic equilibrium in the arc plasma, have been applied to the spectra of the pure elements, to determine the effective arc temperature under relatively clean conditions and in an oxygen environment. These techniques have then been applied to the analysis of a stainless steel sample, again under relatively clean and oxygen environments. In order to explain differences in the $\text{Fe}\text{Cr}$ ratios measured, the behaviour of the intensities of the Fe and Cr emission has been investigated as a function of the oxygen background pressure. The results indicate that while analysis is possible the results depend on the oxygen background pressure.     

Supercritical fluid extraction of chlorophylls and carotenoids from White Sea algae

The supercritical fluid extraction of chlorophylls and carotenoids from marine algae Fucus vesiculosus and Laminaria digitata with carbon dioxide was studied. Complete extraction of carotenoids with carbon dioxide was achieved at a pressure of 250 atm and a temperature of 80°C after 20 min in the absence of a cosolvent. Extraction of chlorophylls in high contents required the use of a polar co-solvent (ethanol, 10–15 vol %) or extraction time increased to 50–90 min (at a co-solvent consumption of <5 vol %). The proposed method is more express compared with extraction in a Soxhlet apparatus.