Low-temperature scanning electron microscopy of particle-exposed mouse lung

Inflated frozen mouse lungs were examined using low-temperature scanning electron microscopy (LTSEM) following bulk fracture under vacuum. Various aspects of pulmonary architecture were identified and correlated with structures revealed by SEM following conventional fixation and preparation techniques. Surface etching of selected samples was performed by radiant heating, revealing characteristic cytoplasmic, nuclear and extracellular lattice patterns resulting from ice crystal formation during freezing. These patterns aided in distinguishing between intra- and extracellular spaces. Pulmonary fluids such as mucus and surfactant were identified. Iron oxide particles were introduced into the lungs of some animals by intratracheal instillation and were subsequently identified in frozen-hydrated lung tissue using characteristic X-ray identification and mapping techniques. Particles were observed both intra-and extracellularly and were commonly found in large deposits. These observations confirm the utility of LTSEM techniques for examination of particles within pulmonary tissue. Particle exposure by intratracheal instillation was found to result in a non-uniform distributional pattern.     

氧化铝模板法制备掺杂稀土镧的TiO_2纳米管及其表征

以多孔有序阳极氧化铝(AAO)为模板,采用溶胶-凝胶法制备了掺杂稀土镧的TiO2纳米管;用透射电镜、场发射扫描电子显微镜和X射线衍射仪对AAO模板和纳米管进行了表征,在此基础上分析了纳米管的形成机理.结果表明:模板法制备得到的掺杂稀土镧的TiO2纳米管管径均匀,尺寸在80～120 nm之间.     

Supported metal model catalyst surfaces examined by scanning tunnelling microscopy

Topographic and/or barrier-height images of ultrafine Pt and Au metal particles supported on a vacuum-deposited carbon film or titanium oxide thin films grown on titanium metal sheets were obtained. The topographic images of colloidal Au particles (5-nm diameter) adsorbed on a titanium oxide thin film showed a structure elongated in the direction normal to the x scan, indicating their weak interaction with the support surface. The topographic images of Pt vacuum-deposited on a carbon film showed c. 4-nm diameter particles, larger than those observed in electron microscopy. The problems inherent to the STM observation of such dispersed metal systems are identified. In the case of Pt particles vacuum-deposited on titanium oxide film, its barrier-height image gave better indication of different phases on the surface than its topographic image. The significance of obtaining barrier-height images along with topographic images for such sample systems is demonstrated.     

Determination of the mean caliper diameter of lung nuclei by a method which is independent of shape assumptions

When determining the number of nuclei (therefore cells) present in a known volume of tissue it is necessary to determine the overall mean caliper diameter of nuclei for each cell type studied. Most previous methods for determining the mean caliper diameters (D?) of cell nuclei were strongly dependent upon assumptions of the shape of the particles in question (Greeley et al., 1978). A computer program has now been designed to calculate D? from three-dimensional reconstructions of nuclei in a manner that is independent of all shape assumptions. The D?s of ten capillary endothelial cell nuclei from normal rat lungs have been determined by this shape-independent method. The resulting overall mean caliper diameter for this group of ten nuclei varied only slightly from that previously estimated for them by a method which assumes them to be triaxial ellipsoids. In a similar comparison, the D?s for ten normal human lung endothelial cell nuclei were determined by both methods. The overall mean caliper diameter determined by the shape-independent method was 10% larger than that estimated by the shape-dependent method. This suggests that human lung endothelial nuclei vary significantly from the shape assumption (triaxial ellipsoid) employed in the shape-dependent method, and the shape-independent method was considered to yield a more accurate measurement of D?.     

HREM image simulations for small particle catalysts on crystalline supports

The imaging conditions for electron microscope studies of supported ultrafine particle catalysts have been investigated by multislice simulations. Images of Pt and ReO₄ particles ranging from 0·4 to 2·3 nm in size were simulated in both plan view and profile view with a rutile (TiO₂) support. It was shown that particle visibility varied greatly with the objective lens defocus. Optimum defocus was not favourable for supported particles in plan view since the ultrafine supported particles were least visible at this defocus. Underfocusing, especially at defoci corresponding to half-spacing fringes in the TiO₂ support, led to improved visibility and resolution of the supported particles. Although the structure and shape of supported ultrafine particles should be resolved better with a 400-kV high-resolution electron microscope, their detectability is poorer than with a 200-kV instrument. An ReO₄ cluster should be detectable at 200 kV on TiO₂ supports up to 5 nm in thickness, whereas it is only likely to be detectable at 400 kV on supports up to 3 nm in thickness. The simulations confirmed that optimum defocus is most favourable for imaging supported particles in profile view. Atomic information for particles as small as a 13-atom Pt cuboctahedral cluster should be resolvable with a 400-kV instrument. The crystalline Ti monolayer observed on surfaces of Pt particles, which could explain the mechanism known as SMSI, was simulated as an example of profile imaging.     

Morphological aspects of particle uptake by lung phagocytes

Macrophages residing on the inner epithelial surfaces of airways and alveoli are the only lung phagocytes exposed directly to the environment. Their phagocytic and microbicidal activities are essential for maintaining this organ in a clean and sterile state. The morphology of these phagocytes can be investigated in situ only after implementing special techniques, which involve intravascular triple-perfusion of aqueous fixatives or instillation of nonpolar ones. Such studies have revealed the engulfment of particles by these cells to be rapid, the process being essentially complete within a day. Particles are entrapped within phagosomes and the host cells eventually transported out of the lungs by mucociliary action, macrophages with higher loads being more rapidly eliminated than those with lower ones. Very small particles or those persisting on the epithelial surfaces may be taken up by the eponymous cells. Translocation of particles into the underlying connective tissue and their subsequent phagocytosis by interstitial macrophages prolongs their retention time in the lungs. The still poorly studied pleural macrophages might be involved in cell-mediated immune responses within the pleural space. Intravascular pulmonary macrophages figure largely in the phagocytosis of circulating particles. The role played by dendritic cells in particle uptake by the lungs is not well understood. Airway and alveolar macrophages are the primary phagocytes of the lung. In nonoverload situations and for particles >1 microm, a small proportion of those recruited suffices to remove material from the epithelial surface before other phagocytes, with an apparently greater immunological potential, gain access to it.     

An Experimental Study on the Concentration and Shape of Dents Caused by Spherical Metallic Particles in EHL Contacts©

An experimental study of metallic contaminant effects on surface indentation in EHL contacts is presented. Particles are initially spherical and are composed of M50 high-carbon steel powder. Their diameter ranges from 32 to 40 μm. An original lubrication system with a controlled level of contamination was built. The contaminant distribution and concentration are measured on-line by an automatic particle counter. Tests are conducted on a two-disk machine with different operating conditions. Particles may travel through the EHL contact only one time, the lubricant flow being used only once. The oil is a synthetic one qualified under the MIL-L-23699 specification. An optical profilometer is used to describe the indent topography and a CCD video camera to count the number of dents.

The test bench is described and the experimental procedure is presented. Specific tests were performed to quality the contamination bench. The combined effects of particles concentration and test duration on dent distribution were studied. Some results on the shape and concentration of indents versus operating conditions are presented. It is shown that over the range of test conditions considered, the number of indents on the raceways can be estimated from the particle concentration in the oil bulk. This leads to the conclusion that the particle entry ratio is close to one, i.e., the concentration of particles inside the EHL contact is close to those in the bulk.     

A study on the pressure loss,heat transfer enhancement and fouling control in a vertical particulate flow

In this study, the pressure loss, the heat transfer rate and the fouling characteristics of a particulate flow were investigated. Particles used were the glass beads of 3.0 mm diameter with 2.54 specific gravity. The particles augmented the heat transfer at the flow velocities lower than 1.0 m/s. In this range, the heat transfer coefficient slighly increased as the particle volume fraction increased, and was almost independent of the flow velocity. The particles also increased the pressure loss at the flow velocities lower than 1.0 m/s. Above 1.0 m/s, however, the heat transfer coefficient and the pressure loss were essentially the same as those of flow with pure water. Through the flow visualization study, the collision frequency on the wall by particles is shown to be closely related with the heat transfer enhancement. The particles effectively controlled fouling. Fouling tests using ferric oxide revealed that the particles effectively removed the pre-exsisting deposit as well as they prevented the deposit buildup.     

Nanogrinding of soft–brittle monocrystalline mercury cadmium telluride using a ceramic bond ultrafine diamond grinding wheel

Nanogrinding experiments on soft–brittle monocrystalline mercury cadmium telluride (HgCdTe, MCT) were conducted using a novel developed ceramic bond ultrafine diamond grinding wheel. The experimental results showed that the ultrafine grinding wheel exhibited excellent grinding performance on HgCdTe wafers. Surface roughness Ra 1.4?nm, rms 1.7?nm, and PV 10.9?nm were respectively achieved under nanogrinding using this diamond grinding wheel. All the ground surfaces of MCT wafers exhibited ductile mode character, free of cracking and burn damage. The nanogrinding results were discussed in terms of the ceramic bond, as well as maximum undeformed chip thickness.     

HREM image contrast from supported small metal particles

HREM, image calculations and small probe diffraction/AEM have been used to characterize structure and contrast of supported small metal particles of ≤5 nm diameter. Such small particles are thought to be active species in industrial applications such as in heterogeneous catalysis where, in general, the particles employed as catalysts are supported. Image calculations (HREM and diffraction contrast) carried out at both 200 keV and 400 keV at various defoci and support thicknesses have shown that in HREM, particle images are obscured by the support contrast with the loss of edge definition and particles appear to be smaller than they actually are. The particle visibility is better at 400 keV. The calculations have also indicated that particle shape varies as a function of support thickness and defocus. The results have clear implications for identification and interpretation of surface structure of the supported small particles accurately by HREM if not performed under controlled conditions and for determining their size and shape.     

毛细管进样-激光解吸电离气溶胶飞行时间质谱仪检测超细纳米颗粒物化学成分

采用毛细管大气压进样接口,结合激光多光子解吸、电离等技术,自行研制了毛细管进样-激光解吸电离气溶胶飞行时间质谱仪,用于在线测量超细纳米颗粒物的化学成分。应用商品化的气溶胶发生器和自制的离子诱导成核反应器,在实验室内分别产生了KCl、NaCl、NaI/NaBr混合物和Air/H₂O/SO₂混合气体成核反应的粒径小于100 nm的超细纳米颗粒物,并通过质谱仪获得了它们的化学成分信息。结果表明,相对于具有较大粒径的颗粒物,超细纳米颗粒物在激光多光子电离过程中更容易完全原子化电离,但通过改善激光的聚焦条件可以获得超细纳米颗粒物成分的分子信息。实验测量了毛细管大气压进样接口传输超细纳米颗粒物的效率,为0.33%,与国际同行采用类似大气压进样接口传输气体分子的效率一致。     

Effect of processing methods for transmission electron microscopy on corneal collagen fibrils diameter and spacing

Introduction: The corneal tissue was processed in fixatives and embedded in resin for transmission electron microscopy to observe the ultrastructure of the collagen fibrils (CFs). The effect of these processing methods on the CF diameter and the interfibrillar spacing was studied. Methods: Four normal human corneal buttons were used for this study. A part of each cornea was fixed in 2.5% glutaraldehyde containing cuprolinic blue in sodium acetate buffer and embedded in spurr's resin (SpurrCB). A second part of each cornea was fixed in 2.5% glutaraldehyde + osmium tetroxide and embedded spurr's resin (SpurrOsm). The third part of each cornea was fixed in paraformaldehyde (4%) and embedded in LR White at 4°C (LRWhite). Ultrathin sections were stained with uranyl acetate and lead citrate. Results: In the tissue, fixed in SpurrCB, the diameter was 38.4 ± 5.9 nm and spacing between CF was 52.5 ± 5.3 nm. In the tissue fixed in SpurrOsm, the diameter was 28.37 ± 5.84 nm and spacing between CF was 45 ± 4.57 nm. In the tissue fixed in LR White, the CF diameter was 24 ± 2.3 nm and spacing between CF was 39.0 ± 4.2 nm. The diameters and interfibrillar spacing of the tissue processed by SpurrCB, SpurrOsm, and LRWhite were significantly different (P < 0.001) from one another. Conclusion: Our study shows that there is a variation in the CF diameter and spacing depending on the method of fixation and embedding resins used. This needs to be considered when comparative studies using different methods are done. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Characterization of ultrafine coal fly ash particles by energy-filtered TEM

In this study, energy-filtered transmission electron microscopy is demonstrated to be a valuable tool for characterizing ultrafine coal fly ash particles, especially those particles encapsulated in or associated with carbon. By examining a series of elemental maps (K-edge maps of C and O, and L-edge maps of Si, Al, Ti and Fe) recorded using the three-window method, considerable numbers of titanium and iron species with sizes from several nanometres to submicrometre were shown to be present, typically as oxides dispersed in the carbonaceous matrix. Crystalline phases, such as rutile and iron-rich oxide spinel, were also identified from electron diffraction patterns and high-resolution TEM images. Information about these ultrafine coal fly ash particles regarding their size, morphology, elemental composition and distribution, and crystalline phases, which has not been available previously in conventional ash studies, should be useful in toxicological studies and related environmental fields.     

Measurement of electron probe beam diameter by digital image processing

The present report illustrates a computerized method for precise measurement of the diameter of an electron beam. The value of this measurement extends beyond simply providing an accurate estimate of resolution. Other salient areas which will benefit include quantitative X-ray microanalysis, energy loss spectroscopy, diffraction studies, and electron beam lithography. The biological sciences as well as the material sciences will gain enormously from improved accuracy in measurement (control) of beam diameter. It is anticipated that most or all of the mathematical manipulations outlined in this paper will be incorporated into digital electronic packages which will perform the functions automatically for setting the electron beam diameter to the scientist's choice. The purpose of the present report is to indicate some of the principles involved so that as electron microscopy becomes more computerized and automated, the user will have some understanding of what the electronics are doing rather than simply depressing a button or two and ignoring the power of what resides within the walls of the instrument. The performance of a scanning electron microscope (SEM) and a scanning transmission electron microscope (STEM) is roughly determined by the incident electron probe beam size (diameter) involving a sufficient electron current. In the present paper, the diameter of an ultrafine electron beam is measured indirectly from the information given by the blurring of an edge in a STEM or a SEM image of a crystalline specimen with fine, sharp edges. The obtained data were processed by digital image processing methods which give an accurate value of the beam diameter. For confirming the validity of this method, a suitable simulation based on the convolution theorem was performed. By using this measurement, we could measure the diameter of an ultrafine electron beam down to 2 nm, which could not be measured easily by previous techniques.     

Photocatalytic deposition of a gold nanoparticle onto the top of a SiN cantilever tip

We propose a new technique for depositing a gold nanoparticle onto the tip of a dielectric support. We employed the photocatalytic effect of titanium dioxide for the deposition. When the titanium dioxide immersed in a solution including gold ions is subject to optical exposure, the excited electrons in the conduction band reduce gold ions into gold metal. Illumination by an evanescent wave generated with a total reflection configuration limits the deposition region to the very tip. In experiments we obtained 100–300 nm gold particles on SiN cantilever tips for atomic force microscopes. The contrast of evanescent interference fringes measured by a near-field scanning optical microscope with this gold nanoparticle probe has proved to be higher than that with a non-deposited SiN probe by a factor of 1.5.     

退火温度对二氧化钛薄膜的性能影响

为了获得性能优良的二氧化钛薄膜,采用电子束蒸发沉积方法制备二氧化钛薄膜,并分别在300、600、900℃空气中对样品进行退火处理以改善所制备二氧化钛薄膜的性能。分别采用X射线衍射(XRD)、原子力显微镜(AFM)以及分光光度计研究了退火温度对二氧化钛薄膜结构和光学性能的影响。结果表明,退火处理可以使二氧化钛薄膜由非晶态薄膜转换为金红石型薄膜,且金红石晶型成分随退火温度的加大而增大,同时退火处理可以改善二氧化钛薄膜在300~1 200nm光谱范围的总吸光率以及增大二氧化钛薄膜的应用范围。     

A method of direct particle deposition on a carbon planchet to study mineral dust in human lung by scanning electron microscopy

Following Na-hypochlorite digestion of lung tissue, mineral particles extracted in the chloroform layer were deposited directly on a pre-smoothed carbon planchet for combined scanning electron microscopy and X-ray energy dispersive spectrometry (SEM and XEDS). Total mineral particle counts were obtained, and detailed physical characteristics of the fibrous particles were documented at 600, 1,500, 4,500 and 9,000 x in three lungs without, and one lung with, histories of occupational exposure. This preparation method was simple, collected more than 99% of identifiable mineral particles in the chloroform layer, gave excellent object to background contrast without heavy metal coatings, and was suitable for XEDS. Comparable fibrous particles from the chloroform layer could also be studied by selected-area electron diffraction to complement the results of XEDS. By this method, we found particles or fibers larger than 0.1 μm were readily counted and measured at 4,500 x. At 600 x, ferruginous bodies were found to be more than twice in number than when sought for by light microscopy. It was determined that 4,500 x is the most efficient magnification to examine and diagnose this type of specimen. The present study illustrates the importance of determining the most efficient magnification to be utilized in particle counts.     

表面活性剂含量对氧化铈/氧化硅复合磨料分散性的影响

以乙醇为溶剂及表面活性剂,以氨水为催化剂,利用正硅酸乙酯的水解得到氧化硅颗粒,并分析乙醇质量92%时制备的氧化硅颗粒呈球形,粒径分布均匀,表面光滑,呈单分散状态;乙醇质量分数为96%时制备的氧化硅颗粒粒径分布范围大,并且小颗粒团聚一体,聚集到大颗粒上.基于理想的氧化硅颗粒,利用化学沉淀法制备CeO2/SiO2复合磨料,并通过透射电子显微镜(TEM)及X射线衍射仪(XRD)对制备的样品进行表征.结果表明,制备的CeO 2/SiO2复合磨料为球形,粒径为150分数对制备的氧化硅颗粒以及氧化铈/氧化硅复合磨料分散性的影响.结果表明:水解体系中乙醇质量分数为71%时制备的氧化硅颗粒基本呈球形,粒径分布范围大,呈少量单分散状态;乙醇质量分数为~250 n m ,具有草莓状核壳的包覆结构,作为抛光磨料可以提高抛光表面质量.     

Evaluation of IgG molecules, Fab' fragments and IgG-horseradish peroxidase conjugates as surface labels for freeze-etched membranes.

Sheep red blood cell (SRBC) ghosts were incubated with preparations of anti-SRBC IgG, antigen-binding fragments of IgG (Fab') or IgG coupled to horseradish peroxidase (HRPO). Frozen samples of the labelled ghosts were deep-etched and replicated with platinum-carbon to visualize their surface features in the transmission electron microscope. The surfaces of control ghosts contain a very low number of 'background' particles (42 +/- 8 particles/micron 2) that vary in size from 4.5 to 25 nm. After labelling with whole IgG the density of surface particles (average diameter 12.3 nm) increases dramatically to 480 +/- 54 per micron 2. Fab'-labelled ghosts exhibited both significantly fewer (87 +/- 14 particles/micron 2) and smaller (average diameter 9.8 nm) surface particles. Ghosts labelled with IgG-HRPO conjugates possessed 590 +/- 45 particles/micron 2 with an average diameter of 15.3 nm. When these ghosts were incubated with diaminobenzidine and hydrogen peroxide the average size but not the density of the particles increased. Based on these and other observations we conclude that an organic surface marker for freeze-etched membranes has to have a diameter of greater than 15 nm if it is to be consistently seen over extended areas and against the background granularity of the surface of a red blood cell ghost. Somewhat better resolution may be expected if markers consisting of inorganic crystals with a distinct shape and coupled to Fab' fragments can be made.     

Heat transfer characteristics of liquid-solid suspension flow in a horizontal pipe

Particles in liquid-solid suspension flow might enhance or suppress the rate of heat transfer and turbulence depending on their size and concentration, The heat transfer characteristics of liquid-solid suspension in turbulent flow are not well understood due to the complexibility of interaction between solid particles and turbulence of the carrier fluid. In this study, the heat transfer coefficients of liquid-solid mixtures are investigated using a double pipe heat exchanger with suspension flows in the inner pipe. Experiments are carried out using spherical fly ash particles with mass median diameter ranging from 4 to 78 μm. The volume concentration of solids in the slurry ranged from 0 to 50% and Reynolds number ranged from 4,000 to 11,000. The heat transfer coefficient of liquid-solid suspension to water flow is found to increase with decreasing particle diameter. The heat transfer coefficient increases with particle volume concentration exhibiting the highest heat transfer enhancement at the 3% solid volume concentration and then gradually decreases. A correlation for heat transfer to liquid-solid flows in a horizontal pipe is presented.