A scanning and transmission electron microscopic study of the development of the surface structure of neuroepithelial bodies in the mouse lung

Neuroepithelial bodies (NEBs) are groups of neuroepithelial (NE) cells that are localized on mounds on the bronchiolar epithelium of the lung. The present study examined NEBs in mice ranging in age from 2 days before birth to 80 days after birth. The position and surface architecture of NEBs was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In foetal mice, 2 days before birth, NEBs were distinguished from the rest of the bronchiolar epithelium by a slight elevation of non-ciliated Clara-like cells arranged in a cobbestone-like pattern. The exposed surface of the NEB was identified by small protrusions with regular microvilli intermittenly located at the base of deep clefts between the Clara-like cells. The surface of the Clara-like cells had fewer and smaller microvilli and could be easily distinguished from the apical surface of the NEB. Before birth, the surface of all of the apical cells was covered by regularly placed microville, however after birth some of the more prominently positional apical cells revealed a bare patch at the centre of the portion of apical cell exposed to the lumen of the lung. As the mice aged there was an increase in the number of apical cell protusions observed with centrally positioned bare patches. These two morphologically distinct surfaces of apical cells may have separate specialized functions. The exposed surfaces of apical cells were often observed in pairs and this feature has been observed in various sensory organs providing support for chemoreceptive function. However small bright spheres resembling vesicles were frequently observed on the lumenal surface of apical cells of the centrally placed bare patch. Transmission electron microscopy confirmed the presence of vesicles on the surface of apical cells and due to their location these vesicles were thought to contain a substance secreted into the lumen of the lung by apical cells. The significance of the bare region on the apical cells is not clear in terms of the proposed chemoreceptive function usually attributed to NEBs. It may be possible that the morphological changes observed in apical cells after birth are more appropriate for secretion of than for chemoreception. This is supported by the observation in the present study of vesicles lying on the lumenal surface of the bare region of the apical cell, however the mechanism for secretion of whoel vesicles is not clear and requires further investigation.     

On the dynamic structure factor for the electron gas

In this paper the well-known electron gas model is expressed as a path integral, and then its dynamic structure factor (DSF) is studied systematically. The study shows that q_c defined in the random phase approximation (RPA) not only is the threshold for a bare plasmon, but also in general is the threshold for any number of renormalized plasmons. The paper focuses on the large momentum transfer case (q > q_c). The conclusion that the self-energy correction appearing in the pertinent Green functions of the DSF vanishes has been reached. An explanation for the first peak in DSF observed in experiments, namely the strong correlation between the single-pair and multi-pair excitations involving only a few pairs, is suggested. An approximate, but nevertheless closed, formula for adding up a set of screened ladder diagrams, which describe the strongest correlation between the single pair and a few (two) pairs, is presented.     

Study of the grain-boundary structure in submicrocrystalline niobium after equal-channel angular pressing

The method of Mössbauer emission spectroscopy on ^119m Sn nuclei was used to study grain boundaries in submicrocrystalline Nb produced by the method of equal-channel angular pressing (ECAP) of poly-crystalline Nb (99.9%). ECAP included 16 passes at room temperature.     

An explanation of the structure in the dynamic structure factor of an electron liquid

We explain the recently observed interesting structure in the dynamic structure factor S(k, ω) of various metallic systems by considering processes that involve single-particle and multi-particle excitations.     

Self-energy contributions to the dynamic structure factor of an electron liquid

It is demonstrated that the experimentally observed two-peak structure in the dynamic structure factor of an electron liquid cannot be explained by the finite life-times of the quasiparticles in the way proposed by Mukhopadhyay et al. The two-peak structure obtained by them disappears if the frequency dependence of the one-particle self-energy is taken into account.     

Collective modes and dynamic structure factor of a two-dimensional electron fluid

The electrons bound to the surface of liquid dielectrics by image forces are described as a two-dimensional, classical, one-component plasma with inverse distance interactions. Exact expressions for the collective modes and the dynamic structure factor are obtained from first principles in the limit of long wavelengths. The differences and analogies with uncharged particle fluids and with the three-dimensional one-component plasma are explicitly displayed. The previously used mean-field approximation is shown not to describe weakly coupled systems and to be inadequate in the long-wavelength region.     

The effects of dynamic exchange on the electron resonance line shapes of octahedral copper complexes

Theoretical electron resonance line shapes have been calculated for dynamically distorting octahedral copper complexes. Comparison with published experimental data leads to an estimate of the activation energy for such processes.     

A structure study of copper oxide for monolayer dispersion of anatase supported

The monolayer dispersion of copper oxide on the surface of anatase and its effect on the properties have been studied by X-ray photoelectron spectroscopy(XPS) and X-ray extended absorption fine structure(EXAFS).XPS results give an utmost dispersion capacity of 7.2mg/gTiO2.Strong interactions between copper oxide and anatase can be seen from EXAFS results.The structure of the supported CuO species is strongly dependent on the amount of CuO loading.When the content of CuO loading is below the utmost dispersion capacity,the surface of CuO/TiO2 is dominated by the highly dispersed CuO species having no-Cu-O-Cu-chains,The copper ion is located in an octahedral coordination environment,and the Cu－O-coordination distance is much longer than that in pure crystalline CuO,when CuO loading is exceeds the utmost dispersion capacity,crystalline CuO is formed on the surface of CuO/TiO2,From the result of the sturcture study,it is Cu-O octahedral Coordination and coordination distance change in comparation with pure crystalline Cuo on the surface CuO/TiO2 that have catalytic activity.     

Hypokinetic stress and neuronal porosome complex in the rat brain: the electron microscopic study

Porosomes are the universal secretory machinery in cells, where membrane-bound secretory vesicles transiently dock and fuse to release intravesicular contents to the outside of the cell during cell secretion. Studies using atomic force microscopy, electron microscopy, electron density and 3D contour mapping, provided rich nanoscale information on the structure and assembly of proteins within the neuronal porosome complex in normal brain. However it remains uncertain whether pathological conditions that alter process of neurotransmission, provoke alterations in the porosome structure also. To determine if porosomes are altered in disease states, the current study was undertaken for first time using high resolution electron microscope. One of pathologies that produce subtle alteration at the presynaptic terminals has been demonstrated to be hypokinetic stress. The central nucleus of amygdale is the brain region, where such alterations are mostly expressed. We have examined the width and depth of the neuronal porosome complex and their alterations provoked by chronic hypokinetic stress in above mentioned limbic region. Specifically, we have demonstrated that despite alterations in the presynaptic terminals and synaptic transmission provoked by this pathological condition in this region, the final step/structure in neurosecretion--the porosome--remains unaffected: the morphometric analysis of the depth and diameter of this cup-shaped structure at the presynaptic membrane point out to the heterogeneity of porosome dimensions, but with unchanged fluctuation in norm and pathology.     

Spectrochemical study of the electron transfer reaction in the tetraazamacrocyclic copper complex series

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 1, pp. 70–75, January, 1989.     

A study of the orientation dependence of the electron energy loss spectra for single crystal films of copper and silver

Apart from two peaks caused by bulk and surface plasmons, four or five peaks (depending on the crystal type) of electron energy losses due to inter- and intraband electron transitions are observed in the investigation of the electron energy loss spectra for metals (Cu, Ag). A comparative analysis of the spectra for Cu or Ag films reveals a shift of bulk plasmon loss peaks to higher values for polycrystals, as in the case of transition metals and semiconductors. In a study concerning the orientation dependence of the energy loss spectra (ELS) for electrons scattered from the copper and silver surface, the anisotropy of the bulk plasmon peak is found when the incident beam’s polar angle or the sample’s azimuthal angle are altered. The anisotropy of the primary electron energy loss for plasmon excitation is also observed, depending on the sample orientation relative to the direction incident electrons. The energy losses are found to increase with an increasing atomic packing density of planes and crystal transparency relative to the incident beam.     

强激光加载铝材料动态损伤特性及其微介观结构观测

在神光-Ⅱ装置上利用强激光加载铝材料进行高应变率(高于106s-1)层裂实验,研究不同初始温度下高纯铝材料的动态损伤特性。采用任意反射面速度干涉仪测量样品自由面速度剖面,由自由面速度剖面计算纯铝样品层裂强度与屈服应力。结果表明:随着温度升高,材料层裂强度减小,屈服应力增大。对激光加载前后样品进行金相分析,观察不同初始温度下纯铝材料的微介观结构变化及其损伤特性。结果表明:随着温度升高,样品晶粒尺度缓慢增大,但在873K(近熔点)时晶粒尺度急剧增加;层裂面附近小孔洞数目较多,孔洞尺寸也较大,而远离层裂面处,孔洞数目相对较少,且尺寸也较小;材料的断裂方式随温度升高由沿晶断裂为主逐渐变为穿晶断裂为主。     

Localization of plastic flow at dynamic channel angular pressing

The effect of plastic flow localization, which is significant for obtaining ultra-fine-grain metals by intense high-rate plastic straining, is studied numerically. Large-scale localization of plastic flow, which is determined by the geometry of the problem, as well as microscopic localization appearing due to instability of plastic strain during the passage of a shock wave through the material, is detected. This effect is proposed for explaining the formation of nanocrystal-size grains obtained in experiments on dynamic channel-angular pressing.     

Copper NQR study of the La 214 system from an aspect of microscopic environment of copper

The nuclear quadrupole resonance (NQR) has been investigated for Cu in La_2–x A _x CuO _y (A=Sr and Ba). Three Cu NQR lines, A, B and C, have been observed, which correspond to three different Cu sites. From the analysis of these NQR intensities, site assignments are possibly as follows. These lines A, B and C are attributed to CuO₆ octahedral, CuO₅ pyramidal and CuO₄ planar sites, respectively. The apical oxygen O(2) is induced to transfer to the interstitial O(3) site between LaO planes when two or more Sr²⁺ ions are located in its neighboring La sites. The excess holes doped into the CuO₂ plane are provided mainly by O(3) as well as the unpaired Sr²⁺ ion.     

Comparison of the electronic structure of a thermoelectric skutterudite before and after adding rattlers: an electron energy loss study

Skutterudites, with rattler atoms introduced in voids in the crystal unit cell, are promising thermoelectric materials. We modify the binary skutterudite with atomic content Co(8)P(24) in the cubic crystal unit cell by adding La as rattlers in all available voids and replacing Co by Fe to maintain charge balance, resulting in La(2)Fe(8)P(24). The intention is to leave the electronic structure unaltered while decreasing the thermal conductivity due to the presence of the rattlers. We compare the electronic structure of these two compounds by studying the L-edges of P and of the transition elements Co and Fe using electron energy loss spectroscopy (EELS). Our studies of the transition metal white lines show that the 3d electron count is similar for Co and Fe in these compounds. As elemental Fe has one electron less than Co, this supports the notion that each La atom donates three electrons. The L-edges of P in these two skutterudites are quite similar, signalling only minor differences in electronic structure. This is in reasonable agreement with density functional theory (DFT) calculations, and with our multiple scattering FEFF calculations of the near edge structure. However, our experimental plasmon energies and dielectric functions deviate considerably from predictions based on DFT calculations.