Monte Carlo simulation of cutaneous reflectance and fluorescence measurements--the effect of melanin contents and localization

Melanin content and distribution in skin were studied by examining a patient with white, brown and blue skin tones expressed on skin affected by vitiligo. Both diffuse reflectance and autofluorescence spectra of the three distinction skin sites were measured and compared. Monte Carlo simulations were then performed to help explain the measured spectral differences. The modeling is based on a six-layer skin optical model established from published skin optical parameters and by adding melanin content into different locations in the model skin. Both the reflectance and fluorescence spectra calculated by Monte Carlo (MC) simulation were approximately in agreement with experimental results. The study suggests that: (1) trichrome vitiligo skin may be an ideal in vivo model for studying the effect of skin melanin content and distribution on skin spectroscopy properties. (2) Based on the skin optical model and MC simulation, the content and distribution of melanin in skin, or other component of skin could be simulated and predicted. (3) Both reflectance and fluorescence spectra provided information about superficial skin structures but fluorescence spectra are capable of providing information from deeper cutaneous structures. (4) The research method, including the spectral ratio method, the method of adding and modifying the melanin content in skin optical models, and MC simulation could be applied in other non-invasive optical studies of the skin.     

DNA and protein changes caused by disease in human breast tissues probed by the Kubelka-Munk spectral functional

Malignant, fibroadenoma, normal and adipose breast tissues were studied using diffuse reflectance spectroscopy. The absorption spectra of the breast tissues were extracted from the diffuse reflectance spectra using the Kubelka-Munk function (K-M function). The spectral features of the K-M function were identified and compared with those of the absorption spectra. The spectral features of the K-M function were assigned to DNA, protein, beta-carotene and hemoglobin (oxygenated and deoxygenated) molecules in the breast tissue. The amplitudes of the K-M function averaged from 275 to 285 nm and from 255 to 265 nm and were found to be different for malignant, fibroadenoma and normal tissues. These differences were attributed to changes in proteins and DNA. A set of critical parameters was determined for separating malignant tissues from fibroadenoma and normal tissues. This approach should hold for other tissue types such as cervix, uterus and colon.     

The effect of UV absorbing sunscreens on the reflectance and the consequent protection of skin

The in vivo reflectance spectra of Caucasian skin, coated with preparations containing sunscreen vehicle, vehicle with olive oil and vehicle with the UVB and UVA absorbers 2-ethylhexyl-4-methoxycinnamate and 4-t-butyl-4'-methoxydibenzoylmethane were determined. All preparations reduced the reflectance of skin throughout the UVA spectral range (320 to 400 nm), with the sunscreen preparations containing the UVB and UVB plus UVA absorbers reducing the reflectance more than the sunscreen vehicle alone. This phenomenon, which facilitates the penetration of UV radiation to the lower epidermis and dermal layers of skin and therefore lessens sunscreen efficacy, is attributed to optical coupling mediated by refractive index matching of the sunscreen to the upper epidermis. The greater reduction in skin diffuse reflectance caused by sunscreens containing methoxycinnamate is associated with this compound's high refractive index. Also, by determining the excitation spectra of the autofluorescence originating from the dermal layer of skin, the transmission spectra of the various components of sunscreen on skin were established, and these were in good general agreement with previously published spectra.     

Differences between infrared spectra of atrazine obtained under transmittance and diffuse reflectance modes

We hypothesized that the surface amino-group of chloro-atrazine particles protonates when exposed to atmospheric moisture and therefore an outer layer of chloro-atrazine colloids was expected to transform to hydroxy-atrazine. To test the hypothesis we compared transmittance infrared (FT-IR) spectra with diffuse reflectance spectra of pure chloro- and hydroxy-atrazine under various treatments and two commercial forms of atrazine, AATREX-4L and AATREX-90. These spectral comparisons indicated that a certain number of chloro-atrazine molecules in the outer-layer of chloro-atrazine crystals transformed to protonated hydroxy-atrazine molecules. This is believed to have practical implications on the fate and mobility of atrazine in the field.     

Evaluation of gel permeation chromatography to Fourier transform infrared spectrometric detection using a modified thermospray for analysis of polystyrene samples

A heated gas flow modified thermospray was used to couple gel permeation chromatography (GPC) to Fourier transform infrared spectrometry (FTIR) for the analysis of the standard polystyrene samples. Effluents from the GPC column were evaporated and the solutes were deposited as a series of spots on the surface of a moving stainless steel belt (0.025 mm thickness × 13 mm width). The belt continuously transferred the spots into the diffuse reflectance (DRIFT) accessory of the FTIR spectrometer, enabling identification of the deposited solutes by measurement of the diffuse reflectance IR spectrum. The IR spectra of the separated components showed excellent agreement of the spectral features to those of standard FTIR spectra and no thermal degradation was observed.     

Study of copper(II) succinate complexed with imidazole or methyl-substituted imidazoles

The preparation of complexes involving copper(II) succinate and imidazole or methyl-substituted imidazoles is described. The results of thermal and spectral analysis are reported for the various complexes prepared. The TGA curves, ESR and diffuse reflectance spectra are reported. The reactional behaviour of the 1,2 dimethylimidazole towards the copper(II) succinate is seen to be different from that of other imidazoles.     

Evaluation of gel permeation chromatography to Fourier transform infrared spectrometric detection using a modified thermospray for analysis of polystyrene samples

A heated gas flow modified thermospray was used to couple gel permeation chromatography (GPC) to Fourier transform infrared spectrometry (FTIR) for the analysis of the standard polystyrene samples. Effluents from the GPC column were evaporated and the solutes were deposited as a series of spots on the surface of a moving stainless steel belt (0.025 mm thickness × 13 mm width). The belt continuously transferred the spots into the diffuse reflectance (DRIFT) accessory of the FTIR spectrometer, enabling identification of the deposited solutes by measurement of the diffuse reflectance IR spectrum. The IR spectra of the separated components showed excellent agreement of the spectral features to those of standard FTIR spectra and no thermal degradation was observed. Received: 20 May 1996 / Revised: 17 October 1996 / Accepted: 28 November 1996     

Identification of origin of coal from the Ostrava-Karvina Mining District by infrared spectroscopy and discriminant analysis

Infrared (IR) spectra of coal from five mines of the Ostrava-Karvina Mining District were collected using diffuse reflectance techniques. The spectral data were classified by the application of discriminant analysis. The aim of this paper is to test out identification of coal origin by IR spectroscopy and discriminant analysis. The results of this study confirm that infrared spectroscopy together with multivariate statistical methods could provide a powerful discriminating tool for the identification of origin of the most of coal from the Ostrava-Karvina Mining District.     

A vibrational spectroscopic study of tris triphenyl phosphine rhodium (I) chloride

In this work we report the first Raman spectrum of tris triphenyl phosphine rhodium (I) chloride. The vibrational spectrum of triphenyl phosphine has also been recorded under similar conditions to facilitate comparisons. FT-Raman spectra and diffuse reflectance mid-IR and far-IR spectra are presented and a full skeletal vibrational assignment is made.     

中药口服固体制剂原辅料近红外光谱数据库的构建及应用

建立了中药口服固体制剂原辅料近红外(NIR)光谱数据库,采用模式识别方法研究了NIR光谱数据在物料分类和物性预测中的应用。使用便携式近红外光谱仪快速测量149批原辅料粉末的NIR漫反射光谱数据,并录入iTCM数据库。利用主成分分析(PCA)法探究NIR光谱数据对已知结构物料的分类能力,采用偏最小二乘(PLS)法研究了NIR光谱对原辅料物性参数和直接压片片剂性能的预测能力。经标准正态变量变换(SNV)+Savitzky-Golay(SG)平滑+一阶导数处理后的NIR光谱数据对微晶纤维素、乳糖、乙基纤维素、交联聚维酮和羟丙基甲基纤维素这5类辅料的区分能力较好。NIR光谱数据与原辅料粉末粒径、密度和吸湿性的相关性较强。NIR光谱信息作为物料物理性质的补充,可提高粉末直接压片片剂性能预测模型的性能。NIR光谱数据是iTCM数据库物性参数数据的补充,物性参数与NIR光谱数据的结合能更全面地表征原辅料的性质。     

Application of an HPLC-FTIR modified thermospray interface for analysis of dye samples.

Previously, we developed a reversed-phase HPLC method compatible to high performance liquid chromatography diffuse reflectance Fourier-transform infrared (HPLC-FTIR) thermospray interface for the analysis of dyes. Dye separation achieved with a mixed-mode (SCX-ODS) column using a small gradient (90 to 80% water with acetic acid) and pH 3.25; 10 to 20% acetonitrile was considered to be suitable for HPLC-FTIR. A constant-voltage setting for the thermospray temperature (227 degrees C) was successfully used for this gradient condition. The HPLC-separated components deposited as a series of concentrated spots on a moving tape were scanned by specially developed HPLC-FTIR software. Excellent repeatability of the thermospray deposition FTIR chromatograms and IR spectra was obtained. The interface-derived spectra of the separated components of formulated and purified reactive dyes were compared and differences in spectral features were observed.     

Quality control of the powder pharmaceutical samples of sulfaguanidine by using NIR reflectance spectrometry and temperature-constrained cascade correlation networks

Temperature-constrained cascade correlation networks (TCCCNs) were applied to the identification of the powder pharmaceutical samples of sulfaguanidine based on near infrared (NIR) diffuse reflectance spectra and their first derivative spectra. This work focused on the comparison of performances of the uni-output TCCCN (Uni-TCCCN) and multi-output (Multi-TCCCN) by near infrared diffuse reflectance spectra and their first derivative spectra of sulfaguanidine. The TCCCN models were verified with independent prediction samples by using the “cross-validation” method. The networks were used to discriminate qualified, un-qualified and counterfeit sulfaguanidines pharmaceutical powders. The results showed that single outputs network generally worked better than the multiple outputs networks, and the first derivative spectra were more suitable for the identification comparing with original diffuse reflectance spectra. With proper network parameters the pharmaceutical powders can be classified at rate of 100% in this work. Also, the effects of parameters and related problems were discussed.     

Investigation of Thermal Degradation of PVC in the Solid State

The thermal degradation of PVC powders and the inhibition of this process by cadmium laurate was investigated by the measurement of discoloration, diffuse reflectance spectra, and the quantity of hydrochloric acid formed. Kinetic analysis of the data obtained by us previously showed that both the data of color measurements and those of diffuse reflectance spectra may be used conveniently for the calculation of the number of double bonds formed during the degradation.     

基于近红外光谱分析技术的栽培香菇产地快速鉴别

建立了一种基于近红外光谱分析技术的香菇产地鉴别方法。利用近红外光谱仪扫描不同主产地的香菇干样,获得样品的近红外漫反射光谱。利用偏最小二乘判别分析(PLSDA)分别建立了吉林、湖北、福建3个省份栽培香菇的产地判别模型,同时使用光谱预处理和波长筛选技术对判别模型进行优化,最后使用预测样品对模型进行验证。结果表明,使用原始光谱建立的模型能够初步实现对产地的判别,使用光谱预处理技术扣除光谱中的背景信息,同时利用波长筛选技术选择特定波长对模型进行优化后,可进一步提高预测正确率。该方法为香菇产地真实性溯源提供了一种新方法,对香菇产业发展具有重要的实际意义。     

铂丝表面电化学聚合膜的外反射红外光谱研究

<正> 金属丝表面的聚合物很难用普通红外吸收技术进行表征。因为金属丝使入射光向各个方向散射,平面形光学镜不能有效地收集这种散射光。漫反射装置主要用于粉末样品的研究,用椭球形光学镜收集粉末样品的漫反射光线。我们在研究了光线在金属表面叠加效应的基础上,综合平面反射吸收和漫反射技术的特点,建立了研究金属丝表面涂层技术。即用漫反射装置的椭球光学镜收集反射光,从而得到金属丝表面薄层聚合物的外反     

Complexes of Oxamic Acid with La(III), Gd(III), Tb(III), Er(III), Tm(III) and Lu(III)

The preparation, for the first time, of the deprotonated complexes of oxamic acid with La(III), Gd(III), Tb(III), Er(III), Tm(III) and Lu(III) is reported. Analytical results, conductometric measurements, magnetic moments and spectral data (IR and diffuse reflectance spectra) are discussed in terms of possible structural types. The oxamate anion acts as a N, O bidentate non-bridging ligand.     

银镜增强的近红外漫反射光谱法测定血清尿素

针对近红外漫反射光谱(NIRDRS)技术灵敏度低或检出限高的缺点,采用银镜作为吸附基底以改善其灵敏度.银镜的强反射能力不仅能够降低光谱的背景干扰,还能增强光谱的响应信号.研究了NIRDRS技术结合银镜基质用于快速定量分析血清尿素含量的可行性.直接采集富集了血清的银镜基质的NIRDRS光谱,结合光谱预处理和变量选择方法,采用偏最小二乘回归建立了定量校正模型并进行快速预测.结果表明,采用银镜基质结合NIRDRS技术可以准确地测定含量为2.8~26.1 mmol/L的血清尿素,预测值与参考值的相关系数(R2p)为0.9823,样品回收率为86.0%~117.0%,且预测得到的最大误差值低至1.45 mmol/L.     

Synthesis and optical properties of non-stoichiometric lanthanide (Sm,Eu, Tm,Yb) fluorides

Nonstoichiometric samarium, europium, ytterbium, and thulium fluorides were prepared by reduction of the corresponding trifluorides with the same lanthanide metal or silicon. Crystal lattice type and lattice parameters of the compounds were determined by powder X-ray diffraction. In the synthesis of ytterbium fluoride, the formation of cubic superstructure Yb₂₇F₆₄ was detected. Data reflecting the relationship between the structure and optical characteristics of the phases (IR spectra, electronic diffuse reflectance spectra) were obtained and the spectral bands were assigned.     

CHANGES IN TOTAL DIFFUSE SPECTRAL REFLECTANCE OF AMINO ACIDS AND PROTEINS AFTER ULTRAVIOLET IRRADIATION

Abstract— Total diffuse reflectance spectra of air-dried surfaces of free and neutralized amino acid preparations before and after irradiation in vitro are reported. It was found that some free or neutralized amino acid surfaces underwent modification which resulted in changes in the diffuse reflectance spectra after U.V. exposure. It is suggested that these reflectance changes result from transformations in the side chains of the amino acids and that the transformations may differ from those occurring when amino acids in solution are irradiated. Histidine, cystine, hydroxyproline and some protein surfaces showed changes in reflectance of 330–400 nm light similar to those reported in skin after U.V. irradiation in viuo.     

Enhancing calibration models for non-invasive near-infrared spectroscopical blood glucose determination

Partial least-squares regression (PLS) and radial basis function (RBF) networks are used to compute calibration models for non-invasive blood glucose determination by NIR diffuse reflectance spectroscopy. A model computation shows that even extremely small deviations of the spectra induce increased prediction errors. Since the spectral contribution of blood glucose is much smaller than deviations resulting from the non-invasive measuring process a method based on Pearson’s correlation coefficient can be used for evaluating the quality of the recorded spectra during the prediction step. Another method is based on the leverage values from the hat matrix of the RBF network. Both methods lead to a significant decrease in prediction error.