NMR Fast Field Cycling Relaxometry of Unsaturated Soils

The bioavailability of water for plant nutrition in natural soils is controlled by the pore system structure and the interaction of water with the pore walls at variable degrees of saturation. For the characterization of these processes T ₁ relaxometry is particularly suitable because it is not influenced by internal gradients and the frequency dependence of T ₁ includes detailed information about the local dynamics at the pore walls. Using Fast Field Cycling Relaxometry, we have determined T ₁ relaxation dispersion curves of unsaturated soil materials which cover a broad range of textures between pure sand and silt-loam. The mean relaxation rates scale inversely with the water content, as expected according to the Brownstein–Tarr model, which means that the effective pore volume is the only water-contributing fraction. By further analysis of the relaxation dispersion curves we find a bi-logarithmic behavior which is describable by a model of two-dimensional diffusion at the liquid–solid interface in the neighborhood of paramagnetic impurities at the surface. The microscopic wettability, as expressed by the ratio of surface residence time and correlation time, is identical for the soil material but decreases by a factor of two for the sand. This relaxation mechanism is unique for all textures and water contents and proves that the water mobility at the surface does not decrease even at the lowest water contents.     

Riccati-Type Equations, Generalised WZNW Equations, and Multidimensional Toda Systems

We associate to an arbitrary ℤ-gradation of the Lie algebra of a Lie group a system of Riccati-type first order differential equations. The particular cases under consideration are the ordinary Riccati and the matrix Riccati equations. The multidimensional extension of these equations is given. The generalisation of the associated Redheffer–Reid differential systems appears in a natural way. The connection between the Toda systems and the Riccati-type equations in lower and higher dimensions is established. Within this context the integrability problem for those equations is studied. As an illustration, some examples of the integrable multidimensional Riccati-type equations related to the maximally nonabelian Toda systems are given. Received: 3 August 1998 / Accepted: 21 December 1998     

Aggregation and Deposition Characteristics of Fullerene Nanoparticles in Aqueous Systems

The propensity of n-C₆₀ to aggregate and deposit will play a key role in determining its longevity in aquatic systems, and therefore the potential exposure and risk presented by these colloids. We consider the origin of n-C₆₀ stability and compare the aggregation and deposition characteristics of n-C₆₀ under conditions of variable ionic strength using an indifferent electrolyte. Relatively weak electrolyte solutions (0.001 M) were observed to destabilize suspensions of n-C₆₀ resulting in the formation of settleable aggregates. This behavior supports the hypothesis that the stabilizing mechanism for n-C₆₀ clusters is electrostatic in origin. Similarly, the deposition of n-C₆₀ in porous media increased as ionic strength increased. These observations suggest that under some conditions present in natural aquatic systems, these materials may have limited mobility as they form large aggregates that may settle out of suspension or deposit on surfaces. These phenomena may, at least partially, offset any risk presented by n-C₆₀ toxicity due to a reduced potential for exposure.     

The Stochastic Adiabatic Approximation of Multidimensional Non-Markovian Systems Driven by the Ornstein-Uhlenbeck Noises

A set of nonlinear stochastic differential equations (NSDE'S) that describes a large class of nonlinear multidimensional non-Markovian dynamical systems driven by the Ornstein- Uhlenbeck(O-U) noises is studied. By virtue of the stochastic generalization of usual adiabatic approximation, we obtain the equation for the order parameter. The statistical properties of the new stochastic variables occurred are studied. The effective Fokker-Planck equation (EFPE) corresponding to the equation for the order parameter is derived and the stationary solution of EFPE is calculated.     

双水相体系中钼与铼的分离

在聚乙二醇2000-NaOH双水相体系,研究了Mo(Ⅵ)与Re(Ⅶ)的萃取行为。在6mol/L的NaOH碱液体系中,通过加入掩蔽剂的方法,可实现Mo(Ⅵ)与Re(Ⅶ)的萃取分离,同时探讨了聚乙二醇对金属离子的萃取机理。     

Relaxometry of insensitive nuclei: optimizing dissolution dynamic nuclear polarization

We report measurements of spin-lattice relaxation of carbon-13 as a function of the magnetic field ('relaxometry') in view of optimizing dissolution-DNP. The sample is temporarily lifted into the stray field above a high-resolution magnet using a simple and inexpensive 'shuttle'. The signals of arbitrary molecules can be observed at high field with high-resolution and sensitivity. During the dissolution process and subsequent 'voyage' from the polarizer to the NMR magnet, relaxation is accelerated by paramagnetic polarizing agents, but it can be quenched by using scavengers.     

Magnetic Properties of Nanoparticles Useful for SQUID Relaxometry in Biomedical Applications

We use dynamic susceptometry measurements to extract semiempirical temperature-dependent, 255-400 K, magnetic parameters that determine the behavior of single-core nanoparticles useful for SQUID relaxometry in biomedical applications. Volume susceptibility measurements were made in 5 K degree steps at nine frequencies in the 0.1-1000 Hz range, with a 0.2 mT amplitude probe field. The saturation magnetization (M_s) and anisotropy energy density (K) derived from the fitting of theoretical susceptibility to the measurements both increase with decreasing temperature; good agreement between the parameter values derived separately from the real and imaginary components is obtained. Characterization of the Néel relaxation time indicates that the conventional prefactor, 0.1 ns, is an upper limit, strongly correlated with the anisotropy energy density. This prefactor decreases substantially for lower temperatures as K increases. We find, using the values of the parameters determined from the real part of the susceptibility measurements at 300 K, that SQUID relaxometry measurements of relaxation and excitation curves on the same sample are well described.     

Multidimensional Particle Size Distributions and Their Application to Nonspherical Particle Systems in Two Dimensions

Particle science and technology evolve toward ever increasing complexity with respect to the multidimensional particle properties of size, shape, surface, internal structure, and composition. In this study, the theoretical background is elaborated for multidimensional particle size distributions (PSDs) by transferring the concepts known from 1D size distributions to anisotropic particles comprising at least two different length dimensions, e.g., nanorods and platelets. After introducing 2D PSDs, the calculation of differently weighted probability density functions including their interconversion is presented. This is necessary in order to compare data resulting from different measurement techniques which probe different physical properties and thus provide differently weighted PSDs. In addition, it is shown how 1D distributions with reduced content of information can be deduced from 2D PSDs. As a proof‐of‐concept and for illustration purposes, this approach is applied to a 2D Gaussian size distribution. Furthermore, a generalized scheme is suggested which outlines the conversion of number, surface, and volume weighted densities within the 2D space. The application of these methods to the more general n‐dimensional case is straightforward.     

Spherical-Symmetry and Spin Effects on the Uncertainty Measures of Multidimensional Quantum Systems with Central Potentials

The spreading of the stationary states of the multidimensional single-particle systems with a central potential is quantified by means of Heisenberg-like measures (radial and logarithmic expectation values) and entropy-like quantities (Fisher, Shannon, Rényi) of position and momentum probability densities. Since the potential is assumed to be analytically unknown, these dispersion and information-theoretical measures are given by means of inequality-type relations which are explicitly shown to depend on dimensionality and state’s angular hyperquantum numbers. The spherical-symmetry and spin effects on these spreading properties are obtained by use of various integral inequalities (Daubechies–Thakkar, Lieb–Thirring, Redheffer–Weyl, ...) and a variational approach based on the extremization of entropy-like measures. Emphasis is placed on the uncertainty relations, upon which the essential reason of the probabilistic theory of quantum systems relies.     

Effects of Cross-Correlation Colour Noises on Tumour Growth Process

We present a tumour cell growth process model including a multiplicative coloured noise and an additive coloured noise correlated. How the noise cross-correlation intensity λ and correlation time T can affect the steady state properties of tumour cell growth model are discussed by solving an approximative Fokker-Planck equation. It is found that the increase of noise correlation time T can cause the tumour cell number increasing, but the increase of multiplicative noise intensity can cause the tumour cell number extinction. We also find that the increase of cross-correlation intensity λ in the case of 0 〈 λ 〈 1 can cause the tumour cell number extinction, whereas increase of cross-correlation intensity λ in the case of λ 〈 0 can cause the tumour cell number increasing.     

Use of NMR Relaxometry to identify frankfurters of different meat sources

ABSTRACT

Frankfurters are categorised as ready to eat meat products and are prepared by using different meat sources including beef, chicken, turkey or pork or mixtures of them. Due to cost and feasibility, it is very common to adulterate beef-, chicken- and turkey-based frankfurters with pork meat. Since pork is not consumed by some part of the population due to religion, it is important to identify pork frankfurters based on easy quality control methods. In this study, NMR Relaxometry was used to differentiate four different frankfurter types based on their relaxation times. Relaxation measurements were conducted on three permanent field benchtop NMR spectrometers (13.52/20.34/22.35?MHz) and also using an FFC Relaxometer at a frequency range of 40?kHz–8.86?MHz. Physical properties of frankfurters such as moisture and solid fat contents, water activity (a_w) and hardness values were also measured. Results showed that among the permanent field systems, 22.34?MHz was the best to differentiate frankfurters based on both T₁ and T₂ relaxation times. FFC experiments also showed that the dependence of T₁ with respect to frequency follows a well fitted power law behaviour throughout the whole frequency range (R²?>?0.97) and the highest difference on T₁ was observed at the lowest frequency of 40?kHz. Thus the results of the study showed that NMR Relaxometry has the potential to discriminate frankfurters of different meat origin. Further studies are needed to detect the authenticity of the type of mixture in frankfurters.     

双水相体系中镍的光谱性能及测定

本文研究了聚乙二醇 硫酸铵 锌试剂双水相体系中镍的光谱性能及测定。结果表明 ,该体系显色的最佳酸度为pH 8 5 ,络合物光谱最大吸收波长位于 6 75nm ,摩尔吸光系数ε=1 2 6× 10 4 L·mol- 1 ·cm- 1 ,Ni(Ⅱ )线性范围为 0 2～ 2 4 μg·mL 1 。Ni(Ⅱ )和锌试剂络合比为 1∶3。与一般水溶液光度法比较 ,络合物光谱最大吸收波长红移 10nm ,络合比增加 (由 1∶1到 1∶3) ,显色反应的灵敏度和稳定性提高。该方法用于铝合金中镍的测定 ,获得满意结果。     

The Physical Nature of Mesoscopic Inhomogeneities in Highly Diluted Aqueous Suspensions of Protein Particles

The dispersed composition of water samples prepared by the multiple-dilution technique has been investigated opto-physically using two laser diagnostics methods: dynamic light scattering and laser phase microscopy. We studied suspensions of antibodies (Ab) to the human interferon-gamma (IFNγ) in water with an initial concentration of 0.125 mg ml^?1 (5×10¹⁴ mol cm^?3), which were subjected to 12 successive 100-multiple volume dilutions (C12) in water. Individual antibodies and particles of about 300 nm in size, which can be considered as aggregates of individual antibodies, have been found in the initial suspensions. It turned out that some mesoparticles with a concentration on the order of 10³ cm^?3 exist also in suspensions subjected to C12 dilution. These particles have a refractive index close to typical values of protein refractive indices. A possible explanation of the origin of particles with sizes on the order of several hundreds of nanometers, revealed in highly diluted suspensions, is proposed. On the one hand, some of these particles may be aggregates of antibodies from the initial suspension, which remained (due to the flotation effect) in the bulk of the liquid after dilutions. On the other hand, the appearance of solid contaminant particles at the same mesoscopic scale (i.e., on the order of several hundreds of nanometers) cannot be excluded in the dilution process.

     

Characterisation of Ripening and Pressure-Induced Changes in Tomato Pericarp Using NMR Relaxometry

A combination of two-dimensional nuclear magnetic resonance (NMR) relaxometry and optical microscopy is used to investigate the effects of ripening and high-pressure treatment on tomato pericarp tissue. It is shown that the relaxation times of the vacuolar water increase during the early stages of ripening even when there is no visible change and that this could be the basis of a useful on-line sensor for sorting tomatoes. The membrane rupturing and biopolymer denaturation associated with high-pressure treatments are also reflected in the NMR relaxation spectra.     

基于互相关的气泡速度的测量方法研究

通过对比互相关技术和多普勒技术的差别，从一个新的角度把互相关技术应用于尾流测速的研究中.实验中利用高速CCD相机拍摄模拟尾流图像.利用快速傅里叶变换实现互相关算法，为提高计算准确度采用高斯曲线拟合互相关函数的峰值并给出拟合公式，得到了亚像素级的运动速度.为标定互相关算法的准确度，文中采用图像平移的方法验证算法的可行性和可靠性.最后把算法应用于模拟尾流的实验中.该方法有望在舰船尾流速度信息的实时获取上起到重要的应用价值.