Study of the circumstance influence on the elemental distribution in ancient animal bone using μ-XRF

Elemental analysis of archaeological bone plays an important role in the study of the dietary habits of ancient animals. The elemental characteristic of diagenetic skeletons depends on the surrounding circum-stance. The study of environmental influence on the elemental concentration of ancient bone is significant. In this paper, the diagenetic influence on archaeological skeletons is analyzed by microbeam X-ray fluorescence (μ-XRF). The results show that the enamel is an excellent barrier to the diagenesis and the element Sr in bone isn’t susceptible to contamination from the buried environment.     

Magnetic characterization of human blood in the atherosclerotic process in coronary arteries

In the last decades there has been an increasing interest in biomagnetism—a field of biophysics concerned with the magnetic properties of living organisms. Biomagnetism focuses on the measurement of magnetic properties of biological samples in the clinical environment. Progress in this field can provide new data for the understanding of the pathomechanism of atherosclerosis and support the diagnostic options for the evaluation and treatment of atherothrombotic complications. Lyophilized human blood samples from patients with atherosclerotic lesions (calcium scoring (CS) CS>0) and without atherosclerotic lesions (CS=0) were magnetically investigated. Magnetic measurements (performed in room and low temperature) indicated significant magnetic differences between these two groups of patients. Atherosclerotic blood samples are characterized by higher concentration of ferrimagnetic particles (magnetite and/or maghemite) and significant changes in the superparamagnetic behaviour. This research presents that magnetometry, in combination with medical research can lead to a better understanding of iron physiology in the atherosclerotic process.     

Influence of near-edge processes in the elemental analysis using X-ray emission-based techniques

The near-edge processes, such as X-ray absorption fine structure (XAFS) and resonant Raman scattering (RRS), are not incorporated in the available theoretical attenuation coefficients, which are known to be reliable at energies away from the shell/subshell ionization thresholds of the attenuator element. Theoretical coefficients are generally used to estimate matrix corrections in routine quantitative elemental analysis based on various X-ray emission techniques. A tabulation of characteristic X-ray energies across the periodic table is provided where those X-rays are expected to alter the attenuation coefficients due to XAFS from a particular shell/subshell of the attenuator element. The influence of XAFS to the attenuation coefficient depends upon the atomic environment and the photoelectron wave vector, i.e., difference in energies of incident X-ray and the shell/subshell ionization threshold of the attenuator element. Further, the XAFS at a shell/subshell will significantly alter the total attenuation coefficient if the jump ratio at that shell/subshell is large, e.g., the K shell, L₃ subshell and M₅ subshell. The tabulations can be considered as guidelines so as to know what can be expected due to XAFS in typical photon-induced X-ray emission spectrometry.     

Analysis of the impact degree distribution in metabolic networks using branching process approximation

Theoretical frameworks to estimate the tolerance of metabolic networks to various failures are important to evaluate the robustness of biological complex systems in systems biology. In this paper, we focus on a measure for robustness in metabolic networks, namely, the impact degree, and propose an approximation method to predict the probability distribution of impact degrees from metabolic network structures using the theory of branching process. We demonstrate the relevance of this method by testing it on real-world metabolic networks. Although the approximation method possesses a few limitations, it may be a powerful tool for evaluating metabolic robustness.     

Analysis of the 3-dimensional electron distribution in silicon using directional Compton profile measurements

A method of reconstructing the electron momentum density (p), and its Fourier transform,B(t), from a series of directional Compton profiles is described. It is based on a double Fourier inversion technique and an expansion in lattice harmonic functions. The effect of random errors has been analysed, and the implications for the data collection discussed. We have used the reconstruction technique to obtain (p) andB(t) for silicon from six directional Compton profiles measured with 412 KeV gamma-radiation. The experimental result is in good agreement with earlier measurements and with available solid state theories. A recent Wannier function calculation for silicon using orthogonalised bond orbitals provides a useful tool for identifying the physical origins of the observed anisotropies. A comparison between the information presented in position and momentum space shows that the ease of interpretation depends upon the degree to which the various interactions give rise to localised features in each representation.     

Magnetic resonance imaging of coronary arteries and heart valves in a living mouse: techniques and preliminary results

New investigations in MRI of a mouse heart showed high-contrast cardiac images and thereby the possibility of doing functional cardiac studies of in vivo mice. But is MRI, in addition, capable of visualizing microstructures such as the coronary arteries and the heart valves of a living mouse? To answer this question, 2D and 3D gradient echo sequences with and without flow compensation were used to image the coronary arteries. To increase signal-to-noise ratio, a birdcage resonator was optimized for mouse heart imaging. Contrast between blood and myocardium was achieved through the inflow effect. A segmented three-dimensional FLASH sequence acquired with a multiple overlap thin slab technique showed the best results. With this technique an isotropic resolution of 100 microm was achieved. The left coronary artery could be visualized up to the apex of the heart. This is demonstrated with short axis views and 3D surface reconstructions of the mouse heart. The four cardiac valves were also visible with the 3D method.     

Energy distribution of the universe in the Bianchi type II cosmological models

Using the energy‐momentum complexes of Tolman, Papapetrou and Weinberg, the total energy of the universe in Locally Rotationally Symmetric (LRS) Bianchi type II models is calculated. The total energy is found to be zero due to the matter plus field. This result supports the viewpoint of Tryon, Rosen and Albrow.     

Effects of the orientational distribution of cracks in solids

We derive a theory for the elastic characterization of multicracked solids based on a homogenization technique. We consider a material containing a two-dimensional arbitrary distribution of parallel slit cracks which is elastically equivalent to a crystal with orthorhombic symmetry. We obtain explicit expressions for the macroscopic elastic stiffness tensor which is found to depend upon both the density of cracks and their angular distribution, here described by a suitable order parameter. For the isotropic case, we find that the degradation depends exponentially on the crack density. In addition, we show an unusual elastic behavior of a multicracked medium in the plane strain condition: for a negative Poisson ratio, we obtain an effective Young modulus greater than the actual value of the host matrix.     

Analysis of the distribution of diffusion coefficients in cat brain at 9.4 T using the inverse Laplace transformation

In this work, the usefulness of the inverse Laplace transformation (ILT) in the characterization of diffusion processes in the brain has been investigated. The method has been implemented on both phantom and in vivo cat brain data acquired at high resolution at 9.4 T. The results were compared with monoexponential and biexponential analyses of the same data. It is shown that in the case of diffusion restricted by white matter axonal tracts, the resulting diffusograms are in good agreement with the biexponential model. In gray matter, however, the non-monoexponential decay does not lead to a bimodal distribution in the ILT, even though the data can be fitted to a biexponential. This finding suggests the possibility of a distribution of diffusion coefficients rather than a discrete biexponential behavior. It is shown that this distribution is sensitive, for example, to experimental parameters such as the diffusion time. Thus, the ILT offers the possibility of implementing a unique tool for the analysis of heterogeneous diffusion, that is, the analysis of the diffusion coefficient distribution, which has the yet unexplored potential of being a valuable parameter in the characterization of tissue structure.     

Analysis of thermal distribution in two end pumping Nd:YAG laser rod using bacterial foraging optimization algorithm

There is a strong need for the optimized management of the thermal problem in Nd:YAG laser rod and for a powerful, fast, and accurate modelling tool capable of treating the heat source distribution very close to what it actually is. In this paper, a new optimization algorithm called bacterial foraging optimization algorithm (BFOA) is proposed for simulation of the radial heat distribution. A BFOA discloses a simulation method which delivers the exact temperature distribution in a circularly cylindrical structure with a circularly symmetrical, longitudinally, and transversally non-uniform heat source distribution and circularly symmetrical cooling means. The output power is obtained and compared with previously published experimental measurements for different pump power and a good agreement has been found.     

用傅里叶变换红外光谱研究增强UV-B辐射对PSⅡ蛋白结构的影响

运用傅里叶变换红外光谱技术研究了增强紫外线-B(UV-B)辐射对植物光系统Ⅱ(PSⅡ)中膜蛋白结构的影响.结果显示在增强的UV-B辐射条件下,PSⅡ中蛋白的α-螺旋、β-折叠强度增加,而β-转角的强度下降了近一倍,并且这些结构与周围的耦合减弱.此外,UV-B辐射使酪氨酸残基苯酚环的结构发生改变,并使其微极性降低.UV-...     

Quantum-mechanical calculations of the intensity distribution in spectra of adenine tautomers: II. Two-photon absorption spectra

We have performed quantum-mechanical calculations of the two-photon absorption spectra of three tautomeric forms of adenine in the gas phase and of four forms in the aqueous solution. Based on a comparison of the results of these calculations with experimental data, the occurrence of three structures, Ade-N₉,N₁H⁺, Ade-N₉H (am), and Ade-N₇H(am), in aqueous solution of adenine has been confirmed.     

Studying the elemental composition and manganese distribution in Zn1 − x Mn x Te and Zn1 − x Mn x S films using the μ-PIXE and EDAX methods

The methods of proton-induced X-ray emission (μ-PIXE) and energy-dispersive X-ray analysis (EDAX) are used to study the elemental composition and areal distribution of manganese in Zn_{1 ? x} Mn _x Te and Zn_{1 ? x} Mn _x S films. The μ-PIXE technique is implemented using a nuclear scanning microprobe with a proton-beam energy of 1.5 MeV and cross-sectional dimensions of 4 × 4 μm. The semimagnetic solid solution films are obtained under different operating modes of thermal vapor deposition in the quasiclosed volume of a manganese-containing blend.     

Analysis of the spectator-angular distribution in the light-nuclei reactions

Angular distributions of spectator particles in dp and ⁴Hep reactions in the region of a few GeV have been studied. Significant asymmetries of the spectator particle distributions have been observed for reactions where π-mesons are produced in the final state. Results of calculations in the framework of a spectator model taking into account the nuclear wave function, flux factor and the energy dependence of the NN elementary cross-sections, have been compared to experimental data. A good agreement has been observed for the fragments momenta, where the one-pole mechanism dominates. Received: 11 February 2000 / Accepted: 29 June 2000     

Structural characteristics of the tendinous cord–papillary muscle junction in healthy and hypertensive rats

Although the myotendinous junction (MTJ) of skeletal striated muscle is well known, more detailed studies regarding the structure of the cardiac MTJ are scarce. The objective of the present study was to investigate the morphological characteristics of the MTJ in hearts of healthy and hypertensive (SHR) female rats using histological, ultrastructural and three-dimensional (SEM) methods, as well as to evaluate the expression of vinculin by immunofluorescence. In the two groups, light microscopy showed branching tendinous cords and collagen bundles penetrating the apex of the finger-like projections of the papillary muscle. SEM analysis revealed an enlarged apex of the papillary muscle in SHR which was not observed in healthy animals. The loss of force transmission appears to be compensated by the amplified connection between the papillary muscle and valvular collagen. A large number of intercalated disks close to the fiber apex, small amounts of an amorphous intercellular substance and numerous vesicles were observed in SHR. In these animals, the expression of vinculin was more marked showing a regular distribution and a pattern of transverse striations along the sarcolemma. The presence of this protein in transverse bands suggests that vinculin surrounds myofibrils in the region of the Z band. Vinculin staining was also more marked in the region of the tendinous cord–papillary muscle junctions of SHR compared to control animals. Vinculin was quantified by electrophoresis and higher amounts of this protein were observed in SHR compared to control animals.     

Quantitative XPS: I. Analysis of X-ray photoelectron intensities from elemental data in a digital photoelectron database

An analysis of the correlation of theoretical predictions for photoelectron intensities is made with experimental data from an XPS digital database for 46 solid elements measured using a spectrometer with calibrated intensity and energy scales. This analysis covers single element samples measured for Al and Mg K X-rays. The spectral data are for widescans at 1 eV energy intervals with kinetic energies from 200 to 1506 eV using Al X-rays and to 1273 eV using Mg X-rays. In addition are narrow scans around the photoelectron peaks at 0.1 eV energy intervals. All spectra have the instrument intensity/energy response function removed so that the peak areas are proportional to the number of electrons emitted per steradian per incident K photon. Correlations are made for the ionisation cross sections of Scofield and the inelastic mean free paths given by the TPP-2M formula. The correlations are excellent, apart from a factor which may be associated with the background removal arising from the use of the Tougaard Universal cross section. These correlations lead directly to pure element relative sensitivity factors suitable for quantitative analysis. General equations are also provided to extract values for a new form of relative sensitivity factor for an average matrix. These average matrix relative sensitivity factors lead to simpler equations involving matrix factors that are effectively unity instead of the traditional values in the range 0.3 to 3.0.     

Separation of arteries and veins using flow-induced phase effects in contrast-enhanced MRA of the lower extremities

In 3-D contrast-enhanced magnetic resonance (MR) angiography of the lower extremities the goal is most often to enhance arterial structures while keeping veins and surrounding tissue unenhanced. Imaging during steady-state concentration of a blood pool agent or during poor timing of an extra-cellular contrast medium may result in simultaneous venous enhancement, making interpretation of the angiogram difficult. The aim of this study was to develop a post-processing method to separate the arteries from the veins in standard contrast-enhanced MR angiograms. The method was based on the different accumulation of flow-induced phase in the arteries and veins of the lower extremities. The method was tested in both phantom experiments and volunteers undergoing 3-D contrast-enhanced MR angiography using both an extra-cellular contrast medium and a blood pool agent. In the phantom studies, opposite directional flow was successfully separated at mean flow velocities as low as 9 cm/s. In the volunteer studies, the larger veins were successfully extinguished while the larger arteries were left unaffected. In smaller vessels with low flow velocities the separation was less successful. This was most apparent in vessels not oriented superior-inferior. The method developed here is promising for separating arteries from veins in contrast-enhanced MR angiography although the results could be further improved by either a different pulse sequence design or combining this method with other segmentation methods.     

Effects of spatial distribution of the electron density functional in crystals

The variational principle was used within the concept of quasiparticles to determine one-electron states, taking into account effects of nonlocality of the electron density functional in electromagnetic fields.