Investigations of silicone breast implants with the NMR-MOUSE

Silicone breast implants are used for breast augmentation and breast reconstruction. The issues of concern associated with such implants are: (a) the quality control of each implant before implantation, and (b) the detection of implant bleeding after implantation. We have studied the use of the Nuclear Magnetic Resonance-MObile Universal Surface Explorer (NMR-MOUSE) for the nondestructive testing of (a) the quality of implant shells, and (b) changes in implant gel due to leakage of body fluid into the implant. Depth profiles measured nondestructively through implant shells at different positions of each implant by the Profile NMR-MOUSE assured good reproducibility of the quality and thickness of different shell layers. The leakage of implants upon rupture was mimicked by observing changes in the transverse NMR relaxation time of the implant gel upon ingress of physiological saline solution and safflower oil through the rupture. Results demonstrate that nondestructive testing with unilateral NMR is a potential method for use in the quality control of implants and for the screening of implants for rupture after implantation.     

Application of the NMR-MOUSE to food emulsions

The application of the NMR-MObile Universal Surface Explorer (NMR-MOUSE) to study food systems is evaluated using oil-in-water emulsions, and the results are compared to those obtained using a conventional low-field NMR (LF-NMR) instrument. The NMR-MOUSE is a small and portable LF-NMR system with a one-sided magnet layout that is used to replace the conventional magnet and probe on a LF-NMR instrument. The high magnetic field gradients associated with the one-sided MOUSE magnet result in NMR signal decays being dominated by molecular diffusion effects, which makes it possible to discriminate between the NMR signals from oil and water. Different data acquisition parameters as well as different approaches to the analysis of the NMR data from a range of oil-in-water emulsions are evaluated, and it is demonstrated how the concentration of oil and water can be determined from the NMR-MOUSE signals. From these model systems it is concluded that the NMR-MOUSE has good potential for the quantitative analysis of intact food products.     

Analysis of historical porous building materials by the NMR-MOUSE

Samples of sandstone with and without deposits of silicon oxide stone strengthener as well as samples of historical brick material were analyzed by transverse NMR relaxation and mercury intrusion porosimetry. Relaxation times and relaxation time distributions of the protons from the water saturated samples were measured by low-field NMR using homogeneous and inhomogeneous fields. The measurements in inhomogeneous fields were performed with two different NMR-MOUSE sensors, one with a field gradient of 2 T/m and the other with an average field gradient of about 20 T/m. In the sandstone samples the application of stone strengtheners was shown to result in a confinement of the large pores within the outer layer of a few millimeters depth. Depending on the ferromagnetic contamination of the brick samples, the relaxation time distributions can be affected. The agreement of T2 relaxation time distributions and pore size distributions from mercury intrusion porosimetry was found to be better for the NMR-MOUSE sensors than for the homogeneous field measurements. This is true even for different brick samples, unless the content in ferromagnetic particles is very strong.     

Time-Resolved FTIR Study on the Reaction of CHCl2 with NO2

采用时间分辨傅立叶变换红外发射光谱(TR-FTIR)研究了环境化学中重要的氯代甲基CHCl2和NO2分子的反应. 通 过0.5 cm-1高分辨的TR-FTIR发射光谱观察到四种振动激发态产物CHClO、NO、CO和HCl,进而推测出CHCl2+NO2反应三个相应的产物通道. 其中,CO是CHCl2+NO2反应中首次观测到的产物,而HCl则是明确肯定存在的初级反应产物.     

Degradation of historical paper: nondestructive analysis by the NMR-MOUSE

The NMR-MOUSE is a mobile sensor for single-sided NMR inspection of organic materials which takes advantage of the principles of magnetic resonance and inside-out-NMR. Historical books dating from the 17th century were measured at different points by positioning the NMR-MOUSE on the paper. Different degrees of paper degradation can be discriminated from the regularized inverse Laplace transform of the envelope of the acquired echo signals. For the first time the degradation of historical paper was characterized entirely nondestructively by NMR. As a contribution to current preservation efforts, NMR shows great promise for future use in damage assessment of historical documents.     

Thermo-oxidative aging of elastomers: a temperature control unit for operation with the NMR-MOUSE

Temperature-controlled measurements of the transverse relaxation time were conducted with the NMR-MOUSE (nuclear magnetic resonance mobile universal surface explorer) at 50°C to investigate the heterogeneity of rubber sheets induced by thermo-oxidative aging. With temperature stabilization the relative error ofT ₂ decreased by a factor of 4 on the short time scale. Without temperature stabilization it may reach 30% in the long-time range because of temperature changes in the laboratory. Two different types of mobile temperature control units operating with the NMR-MOUSE are described. These temperature control units are small and portable like the NMR-MOUSE.     

固相时间分辨荧光免疫标记技术研究

通过固相时间分辨荧光免疫分析双功能螯合剂4,7-二氯磺基苯-1,10菲罗啉-2,9-二羧酸标记抗-乙型肝炎表面抗体(HBsAb)IgG实验,对于BCPDA标记蛋白质的方法进行了研究。结果表明：BCPDA在相对温和条件下能与蛋白质反应,反应后蛋白质的相对生物活性高于78％,标记比为23～55,蛋白回收率达60％以上。在一定条件下与铕离子形成稳定的BCPDA-Eu^3 (HBsAb)IgG标记物。利用自建的分析方法,测定了标记过程的有关参数。并对标记物的某些光学特性进行了研究。     

激光诱导氩气等离子体时间分辨特性研究

激光诱导击穿光谱(L IB S)以激光诱导微等离子体的原子发射为技术特征,在科研与工业领域正得到重视与蓬勃发展.作为环境气体的氩气对等离子体演化过程中粒子的碰撞过程有重要影响,决定着L IBS技术分析性能的发挥.利用光谱诊断技术深入研究LIBS技术条件下氩气的光谱特征,对于提升LIBS技术及其应用水平具有重要的意义.利...     

Study of Organized Media Using Time-Resolved Fluorescence Spectroscopy

Many photophysical processes which occur on an ultrafast time scale in ordinary liquids become significantly retarded in organized assemblies, by two to three orders of magnitude. Recently many groups have applied ultrafast laser spectroscopy and theoretical methods to elucidate this dramatic phenomenon. Although the implications of this phenomenon in biology and chemistry are not yet fully understood, it has been demonstrated that ultrafast time-resolved fluorescence spectroscopy is a very powerful tool to study the microscopic properties of the organized assemblies and that water or other liquids confined inside these assemblies are fundamentally different from the corresponding liquid in bulk.     

Time-Resolved Fluorescence Spectroscopy Study on the Photophysical Behavior of Quantum Dots

Room-temperature time-resolved luminescence measurements on single CdSe/ZnS quantum dots (QDs) are presented. Fluorescence emission spectra were recorded over periods of up to 30 minutes with a time resolution as small as 6 ms. For QDs in ambient air, a clear 30–40 nm blue shift in the emission wavelength is observed, before the luminescence stops after about 2–3 minutes because of photobleaching. In a nitrogen atmosphere, the blue shift is absent while photobleaching occurs after much longer times (i.e., 10–15 minutes). These observations are explained by photoinduced oxidation. The CdSe surface is oxidized during illumination in the presence of oxygen. This effectively results in shrinkage of the CdSe core diameter by almost 1 nm and consequently in a blue shift. The faster fading of the luminescence in air suggests that photoinduced oxidation results in the formation of non-radiative recombination centers at the CdSe/CdSeO_x interface. In a nitrogen atmosphere, photoinduced oxidation is prevented by the absence of oxygen. Additionally, a higher initial light output for CdSe/ZnS QDs in air is observed. This can be explained by a fast reduction of the lifetime of the long-lived defect states of CdSe QDs by oxygen.     

用FTIR研究聚酰胺树脂固化过程中官能团的变化

通过红外光谱分析对其反应过程中官能基的变化进行初步的探讨.红外光谱分析得出的结论为:环氧树脂的固化剂聚酰胺树脂,随着温度的升高,酰胺羰基C=O的伸缩振动及NH2的变角振动与C-N的伸缩振动发生耦合作用是引起1640-1657cm-1吸收峰强度显著变化的原因.聚合反应过程中,影响聚合物微观结构变化的因素很多,本文重点讨论温度的影响.     

多环芳烃时间分辨荧光光谱特性研究

利用时间分辨荧光光谱技术,研究了菲、荧蒽、芴、蒽、芘等五种多环芳烃的荧光时间分辨发射光谱特性。以289 nm受激拉曼光作为激发光源,研究了289 nm激发光作用下五种多环芳烃的延时特性和门宽特性。并以多环芳烃随延时时间的荧光峰强度衰减关系曲线,得到菲、荧蒽、芴、芘的荧光寿命分别为37.0, 32.7, 10.9, 147.0 ns。不同荧光物质具有特定的荧光光谱特性,多环芳烃时间分辨荧光光谱特性的研究可以为复杂水体中不同种类多环芳烃的诊断提供依据。     

A Nanosecond Time-Resolved Fluorescence Study of Recombinant Human Myelin Basic Protein

Myelin basic protein (MBP) is a major component of myelin and plays a central role in the maintenance of its compact multilayered structure. Tryptophan fluorescence is sensitive to environmental factors such as polarity and rotational mobility and often reflects conformational changes in proteins. This work describes a detailed examination of the time-resolved emission properties of the single tryptophan of recombinant human myelin basic protein. Fluorescence decay curves were collected at two separate excitation wavelengths and at different wavelengths across the emission spectrum. The fitting parameters obtained with the aid of global analysis were combined with steady-state emission spectra collected from the same samples and are presented as decay-associated spectra (DAS) and time-resolved emission spectra (TRES). The effects of temperature and binding to anionic membranes on the decay of emission of MBP were investigated. The changes in fitted parameters and the appearance of DAS and TRES as a function of experimental conditions are interpreted in terms of variation in the local environment of the single tryptophan in MBP. The implications of the changes in local environment resulting from experimental treatments are discussed in the context of the overall conformation of MBP and are compared to structural and photophysical properties of MBP obtained from the central nervous system tissue of several species [P. Cavatorta, S. Giovanelli, A. Bobba, P. Riccio, and E. Quagliariello, Acta Neurol. (Napoli) 13, 162–169, (1991; P. Cavatorta, S. Giovanelli, A. Bobba, P. Riccio, A. G. Szabo, and E. Quagliarello, Biophys. J. 66, 1174–1179, 1994; P. Cavatorta, L. Masotti, A. G. Szabo, D. Juretic, P. Riccio, and E. Quagliariello, Cell Biophys. 13, 201–215, 1988].     

近红外吸收带在高折射率光学塑料结构表征中的应用

我们合成了 MESDMA、TBBDA、TDGDMA等光学塑料单体 ,并用它们聚合成光塑料。用红外光谱法对它们进行表征 ,对一些吸收谱带的吸收和结构的关系进行了讨论 ,得出了一些规律     

用时间分辨光谱研究红细胞悬液的荧光发射

实验获得了激光照射红细胞悬液的荧光光谱,并分别监测不同荧光峰值波长处强度随时间的衰变过程,测试了其相应的荧光寿命。结果表明,在波长为407nm的激光照射下,红细胞悬液向外发射中心波长分别位于596,628,692nm的荧光光谱,各荧光峰对应衰变过程的平均荧光寿命分别为1.97,13.31,14.58ns。利用荧光强度和吸收率的加和性表示了混合物的总吸收率和总荧光发射强度,通过理论计算获得了红细胞悬液中锌卟啉、原卟啉和其他游离物参与荧光发射的相对含量和相对强度在不同荧光峰位的变化关系,进一步解释了不同峰位处荧光发射强度和平均荧光寿命的变化原因。     

Study of Macromolecular Chain Dynamics in Polymer Complexes by Time-Resolved Fluorescence Spectroscopy

Poly(methyl methacrylate)s labeled with the anthracene fluorophore were prepared by free radical, anionic, and coordination polymerization yielding atactic and syndiotactic polymers. Unlabeled isotactic poly(methyl methacrylate) was prepared by anionic polymerization. Time-resolved fluorescence spectroscopy was used to study polymer association in solution. The time-dependent decays of fluorescence anisotropy show that stereocomplexation causes an increase in rotational correlation times of anthracene fluorophores both embedded in the polymer backbone and attached at the end of the side chain of polymer molecules. The rotational correlation time of anthracene fluorophore in dimethylformamide as a part of stereocomplex is 11.9 and 30 ns in the side chain and embedded in the polymer backbone, respectively, and shorter than 3 ns in noncomplexing solvent.     

Continuous-Wave and Time-Resolved Electron Paramagnetic Resonance Study of Dimerized Aza-Crown Copper Porphyrins

The dimerization of 5-(4’-(aza-15-crown-5)-phenyl) copper porphyrin (CuP) upon the addition of the K(SCN) salt to a solution of the CuP monomer has been proven by electron paramagnetic resonance (EPR). The magnetic resonance parameters of the CuP monomer, the exchange interaction parameter, J = +0.25 cm^?1, and the Cu–Cu distance of the CuP dimer have been determined by comparing the experimental continuous-wave EPR spectra with the results of the numerical calculations. The photoexcited states have been studied in the time-resolved EPR experiments. It has been shown that the time-resolved EPR spectra of the dimerized porphyrins can be presented as a sum of two components that represent the spectra derived by integrating the dataset in the time windows of 1.1–1.3 and 2.1–2.3 μs. To describe the spectrum in the time window of 2.1–2.3 μs, it is assumed that there is an essential contribution to the signal from the excited state of the supramolecule, which is formed by the interaction between the photoexcited porphyrin in the quartet state and the neighboring non-excited porphyrin in the ground state.     

Time-Resolved Flavin Adenine Dinucleotide Fluorescence Study of the Interaction Between Immobilized Glucose Oxidase and Glucose

Time-resolved fluorescence experiments have shown that flavin adenine dinucleotide (FAD) fluorescence emission of sol–gel immobilized glucose oxidase (GOD) exhibits a three-exponential decaying behaviour characterized by long- (about 2.0–3.0 ns), intermediate- (about 300 ps) and short- (less than 10 ps) lifetime, each one being characteristic of a peculiar conformational state of the FAD structure. In the present work time-resolved fluorescence is used to monitor FAD signals in the time interval immediately following the addition of glucose at various concentrations in order to detect the conformational changes occurring during the interaction between sol–gel immobilized GOD and glucose. The analysis of time-dependent fluorescence emission signal has shown that the FAD conformational state changes during the process from a configuration with a prevalence of the state characterized by the long lifetime to a configuration with increased contribution from the process with the intermediate lifetime. The time needed to complete this configuration change decreases with the concentration of added glucose. The results here reported indicate that time-resoled fluorescence can be extremely useful for a better understanding of solid phase biocatalysis that is particularly important in light of their clinical and biotechnological applications.     

安息香笼化合物光化学反应的时间分辨红外光谱

采用时间分辨红外吸收光谱方法,研究了邻甲基苯甲酸安息香酯在266 nm激光作用下发生的光化学反应,并考察了溶剂对反应过程的影响. 从瞬态红外光谱上观察到了邻甲基苯甲酸和苯甲酰自由基及苯偶酰,提供了直接的光谱证据证明了脱保护反应及C-C=O处均裂反应的发生. 通过对比溶剂中不同水含量下均裂反应中间体及邻甲基苯甲酸的产率,发现水含量在溶剂中的增加能促进脱保护反应的发生.