Mössbauer spectroscopy and proton relaxometry study of magnetite nanoparticles designed for preparing diagnostic contrast media

Mössbauer spectroscopy, proton relaxometry, and transmission electron microscopy are used to study magnetite nanoparticles designed for creating diagnostic contrast media. Superparamagnetic magnetite nanoparticles with a size of 5–7 nm and blocking temperature of T _b = 50 K are examined as a component of diagnostic contrast media with relaxation times T ₁ and T ₂ capable of circulating in the bloodstream for a long time. Larger ferrimagnetic nanoparticles (30–40 nm) can be concentrated in pathological tissues by applying an external magnetic field, thereby providing a means for hyperthermia.     

Time-frequency analysis of the dispersive Rayleigh wave in stratified media

The dispersive characteristic of the Rayleigh wave propagating in a stratified media was analyzed by a time-frequency analysis method, the Reassignment of Smooth Pseudo-Wigner Ville Distribution (RSPWVD). Theoretical simulations and experiments were implemented for a homogeneous half-space and a two-layered half-space. It is indicated that the group velocity dispersion curves in different frequency ranges obtained by experimental result are all corresponding to the dominant modes in their surface displacement amplitudes. Such a mode identification of the multi-mode Rayleigh waves is required in inversing the medium parameters.     

Physicists probing active media: What is the measure of success?

I present a critical review of this issue integrating the aims of continuous and agent-based theories and experiment.     

Influences of tissue composition and structural features of biological media on the ultrasonic nonlinearity parameter

The Acoustic nonlinearity parameter is an important parameter innonlinear acoustics.In this article,the nonlinearity parameter B/A of normaland eight kinds of pathological porcine liver tissues were measured by finiteamplitude insert-substitution method.The mixture law for nonlinearityparameter is used to analyze and predict the volume fractions of the compo-nents in a given tissue.It was found that the nonlinearity parameter is sensitiveto the pathological forms of biological tissues and the values of B/A dependon the tissue composition and structural features.     

Revisit to the symmetry relations in diffusely backscattered polarization patterns of turbid media

As there exists an inconsistency in claiming the symmetrical relations in the 16 Mueller matrix elements used to describe a turbid medium, the author restudies the symmetrical relationships between diffusely backscattered polarization patterns in isotropic turbid media and simulates all two-dimensional elements of diffusely backscattered Mueller matrix in both cases of Rayleigh and Mie scatterings using the double-scattering approximation and the Monte Carlo algorithm, respectively. The previous experimental observations are compared with the numerically determined matrix elements, showing a good agreement in both double-scattering model and Monte Carlo simulation. The symmetrical relations between the Mueller matrix elements are clarified.     

Investigation of the passage of 100–1000-MeV/nucleon superheavy ions through homogeneous media

This work is a continuation of the experimental and theoretical investigations of the effect of the Z ₁ ³ correction to the stopping power of ions on the passage of heavy ions ⁴⁰Ar, ⁵⁶Fe, ¹⁹⁷Au, ¹³¹Xe, and ²³⁸U with energies of about 1 GeV/nucleon through a homogeneous medium. The previously observed systematic deviations of the calculations based on the first Born approximation to the scattering of a particle by the atomic electrons in the medium from the experimental values of the total ionization ranges of the nuclei and their stopping powers is confirmed. The discrepancy increases with the atomic number of the projectile nucleus. It is shown that the Z ₁ ³ correction in the form proposed by Jackson and McCarthy eliminates, especially for ions with Z ₁>50, the systematic discrepancy between the computed and experimental values. For the experimental energy range relativistic Mott scattering of a particle by the atomic electrons in the target makes the dominant contribution to the observed Z ₁ ³ effect. Zh. éksp. Teor. Fiz. 115, 404–415 (February 1999)     

Orthogonal transforms of the Lorenz- and Rössler-equation

It is shown that none of the proper or improper orthogonal transformations transforms the Lorenz-equation into a kinetic equation, i.e. into an equation representing reasonable chemistry. It is also shown that none of the proper orthogonal transformations transforms a model by Rössler into a kinetic model either. The importance of the presence of negative cross-effects is hereby emphasized.     

Voltage–current characteristics of needle-plate system with different media on the collection plate

The hybrid electrostatic precipitator and media filtration system are significantly more promising than traditional filtration methods. This paper investigated the electrostatic characteristics of different filter media types used in the hybrid filtration system. The voltage–current (V–I) characteristics of needle-plate system, the collection plate of which is covered by filter media, were measured. Seven types of filter media and collection plate including iron plate, iron grid and activated carbon layer were considered. The glass fiber and polyethylene media reduce approximately 20% of the current value. The bag filter increases the current value because of the back corona effect. Polyester and polyethylene terephthalate materials with activated carbon attached can increase the current value significantly. In addition, this paper studied the effects of cake thickness on V–I characteristics. The results show that the cake layer has little influence on the V–I character when its thickness is not very big.     

Explicit analytical solutions of the anisotropic Brinkman model for the natural convection in porous media (Ⅱ)

Natural convective heat transfer phenomena in porous media are very common in the energy conversion and energy utilization field. Study on these phenomena is an impor- tant branch of heat and mass transfer at the moment[1,2]. For theoretical analysis in early time, the Darcy model proposed many years ago was often used. However, great im- provements have been made to the Darcy model in recent years in order to more accu- rately describe and more widely reflect the objective reality[3―7]. The…     

Integral form of the time-dependent radiation transfer equation—II. Inhomogeneous spherical media

The integral form of the radiation transfer equation, with spherical symmetry for a non-isotropic, time-dependent, inhomogeneous, non-scattering medium is given for arbitrary initial and boundary conditions. The optical depth is generalized to an optical retardation and a separation parameter is introduced to separate boundary and initial conditions. The static solution is identical to the asymptotic form of the time-dependent solution.     

An average-magnetization analysis of R 1ρ relaxation outside of the fast exchange limit

Approximate expressions for the NMR spin relaxation rate constant in the rotating frame of reference R _1ρ are derived for two-site chemical exchange by consideration of the evolution of the average density operator using the stochastic Liouville equation. R _1ρ is obtained as a linearized approximation to the largest (least negative) eigenvalue of the matrix describing the evolution of the average density operator in the long-term limit. The expressions obtained are more accurate than existing expressions when exchange is not fast and the populations of the exchanging sites are close to equal. The new expressions for R _1ρ facilitate the interpretation of chemical exchange phenomena in proteins and other biological macromolecules.     

Polarization of Čerenkov radiation in anisotropic media

Using the method of Stokes parameters, we examine the polarization of erenkov radiation in anisotropic media. The study reveals that the radiation is totally polarized and that circular polarization is purely a quantum effect. We examine two cases: when the particle initially moves along the optical axis and when the particle initially moves perpendicular to the optical axis.     

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

In 1967, Coates discovered the electron channelling contrast of backscattered electrons (BSEs) in scanning electron microscopy, and by this the possibility to investigate arrangements of lattice defects in deformed microstructures of materials. Since that time, a straightforward development of the scanning electron microscopes as well as of the electron channelling contrast technique took place. Nowadays, the performance of scanning electron microscopes is high enough that the resolution of electron channelling contrast imaging (ECCI) micrographs is comparable with conventional bright field transmission electron microscopy (TEM) micrographs. In the first part of the present paper, a historical review on the development of the ECCI technique starting from its discovery more than 45 years ago up to the combination with other advanced methods of scanning electron microscopy like electron backscatter diffraction or high-resolution selected area channelling patterning in the last few years is given. Major important investigations using this technique for the visualization of individual lattice defects like stacking faults (SFs) and dislocations or dislocation arrangements are chronologically summarized. The second part demonstrates that nowadays, ECCI micrographs taken in high-resolution scanning electron microscopes can be called high-resolution ECCI (HR-ECCI). It is shown that the resolution of individual SFs and dislocations in the HR-ECCI micrographs is comparable to that of conventional TEM (about 15 nm defect image width). Furthermore, the paper is demonstrating that HR-ECCI micrographs can be obtained for various types of materials after different mechanical loadings and different grain sizes ranging from large grain size of 500 μm (cast steel) down to less than 2 μm (γ-TiAl).     

Representation of an interaction in the formalism of operator BRST quantization for the standard electroweak theory in the Rξ gauge

An operator BRST quantization of the spontaneously broken SU(2)×U(1) electroweak theory is carried out in the R gauge. A representation is found for the interaction.Leninist Communist Youth League, Tomsk Pedagogical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 79–83, July, 1992.     

Coherent phase contrast imaging of THz phonon–polariton tunneling

We report on coherent spatiotemporal imaging of single-cycle THz waves in frustrated total internal reflection geometry. Our technique yields images of the spatiotemporal electric field distribution before and after tunneling through an air gap in between two LiNbO₃ crystals. Measurements of the reflected and the transmitted THz waveforms for different tunnel distances allow for a direct comparison with results from a causal linear dispersion theory and excellent agreement is found.     

R andRτ ratios at the five-loop level of perturbative QCD

We study perturbative QCD at the five-loop level. In particular we considerR = _tot(e ⁺ e ^– hadrons)/(e ⁺ e ^{– + –}) andR = ( v+hadrons)/( ev). We use our method to estimate the five-loop coefficients. As a result, we obtain _s (M _z ) = 0.1186(11) and _s (34 GeV) = 0.1396(16), which are accurate at the 1% level. We also findR = 3.8350(18), which is consistent withR and is accurate to 0.05%.     

Measurements of air and noble-gas broadening and shift coefficients of the methane R3 triplet of the 2ν3 band

By using a tunable diode laser spectrometer with one absorption White cell for low pressure and one photoacoustic cell for high pressure, line shape parameters of the R3 triplet of the 2ν₃ band of methane at 1.65 μm were measured. The absorption line was recorded by using the wavelength modulation spectroscopy technique with first harmonic detection. The broadening and shift coefficients were obtained by fitting the first harmonic absorption signal while varying the pressure of different perturbing gases: air and noble gases (helium, neon, argon, krypton and xenon). We present here the results for the R3 triplet. The observed shift and broadening coefficients behaviors are discussed. Received: 17 November 2000 / Revised version: 19 February 2001 / Published online: 27 April 2001     

Theoretical analysis of backscattered polarization patterns of turbid media containing glucose

Single scattering model and Stokes-Mueller formalism are introduced to investigate the influence of glucose on backscattered polarization patterns in turbid media. Glucose molecules rotate the polarization plane and induce changes in backscattered Mueller matrix patterns. Some Mueller matrix elements present higher optical rotation as the concentration of glucose augments. Using image subtraction and integration, linear relationship between low glucose concentration in the physiological range and optical rotation degree can be derived.     

Measurements of charge density on powdery or granular media using the “open” Faraday's cage

Application of the measurements of a charge induced on the flat electrode placed at the bottom of a container, for the determination of total accumulated charge is discussed in the paper. The value of correction factor K_Q, important for the numerical linking of both (accumulated and induced) charges, was determined numerically and experimentally. The values of K_Q factors determined by various methods differ as 1:1.7, however application of the method of "open" Faraday cage in technological conditions is fully justified.