50-nm-resolution full-field X-ray microscope without chromatic aberration using total-reflection imaging mirrors.

X-ray spectromicroscopy with a full-field imaging technique is a powerful method for chemical analysis of heterogeneous complex materials with a nano-scale spatial resolution. For imaging optics, an X-ray reflective optical system has excellent capabilities with highly efficient, achromatic, and long-working-distance properties. An advanced Kirkpatrick-Baez geometry that combines four independent mirrors with elliptic and hyperbolic shapes in both horizontal and vertical directions was developed for this purpose, although the complexity of the system has a limited applicable range. Here, we present an optical system consisting of two monolithic imaging mirrors. Elliptic and hyperbolic shapes were formed on a single substrate to achieve both high resolution and sufficient stability. The mirrors were finished with a ~1-nm shape accuracy using elastic emission machining. The performance was tested at SPring-8 with a photon energy of approximately 10 keV. We could clearly resolve 50-nm features in a Siemens star without chromatic aberration and with high stability over 20 h. We applied this system to X-ray absorption fine structure spectromicroscopy and identified elements and chemical states in specimens of zinc and tungsten micron-size particles.

Adjustable hollow-cone output x-ray beam from an ellipsoidal monocapillary with a pinhole and a beam stop.

A combined shading system (CSS) consisting of a beam stop and a pinhole is proposed to be used between an ellipsoidal monocapillary (EM) and a conventional laboratory x-ray source to obtain an adjustable hollow-cone output beam for different experiments with no need for changing the EM. The CSS can change the incident x-ray beam on the EM by adjusting the position of the beam stop and the pinhole, with the corresponding change of the output beam of the EM. In this study, the adjustable hollow-cone output x-ray beam of an 80-mm-long EM with a CSS was studied in detail with a laboratory Cu x-ray generator with a focal spot diameter of 50 µm. The adjustable range of the focal spot size of the EM was from 8.6 to 58.7 µm. The adjustable range of the gain of the focal spot of the EM was from 0 to 1350. The beam divergence of the hollow-cone output beam of the EM ranged from 6 to 16.75 mrad. The illumination angle of the hollow-cone output beam of the EM ranged from 0 to 5.95 mrad. In addition, the potential application of the proposed adjusting method in testing the performance of the EM is briefly discussed.

Approaches to single-nanoparticle catalysis.

Nanoparticles are among the most important industrial catalysts, with applications ranging from chemical manufacturing to energy conversion and storage. Heterogeneity is a general feature among these nanoparticles, with their individual differences in size, shape, and surface sites leading to variable, particle-specific catalytic activity. Assessing the activity of individual nanoparticles, preferably with subparticle resolution, is thus desired and vital to the development of efficient catalysts. It is challenging to measure the activity of single-nanoparticle catalysts, however. Several experimental approaches have been developed to monitor catalysis on single nanoparticles, including electrochemical methods, single-molecule fluorescence microscopy, surface plasmon resonance spectroscopy, X-ray microscopy, and surface-enhanced Raman spectroscopy. This review focuses on these experimental approaches, the associated methods and strategies, and selected applications in studying single-nanoparticle catalysis with chemical selectivity, sensitivity, or subparticle spatial resolution.

Elemental analysis of occupational and environmental lung diseases by electron probe microanalyzer with wavelength dispersive spectrometer.

Occupational and environmental lung diseases are a group of pulmonary disorders caused by inhalation of harmful particles, mists, vapors or gases. Mineralogical analysis is not generally required in the diagnosis of most cases of these diseases. Apart from minerals that are encountered rarely or only in specific occupations, small quantities of mineral dusts are present in the healthy lung. As such when mineralogical analysis is required, quantitative or semi-quantitative methods must be employed. An electron probe microanalyzer with wavelength dispersive spectrometer (EPMA-WDS) enables analysis of human lung tissue for deposits of elements by both qualitative and semi-quantitative methods. Since 1993, we have analyzed 162 cases of suspected occupational and environmental lung diseases using an EPMA-WDS. Our institute has been accepting online requests for elemental analysis of lung tissue samples by EPMA-WDS since January 2011. Hard metal lung disease is an occupational interstitial lung disease that primarily affects workers exposed to the dust of tungsten carbide. The characteristic pathological findings of the disease are giant cell interstitial pneumonia (GIP) with centrilobular fibrosis, surrounded by mild alveolitis with giant cells within the alveolar space. EPMA-WDS analysis of biopsied lung tissue from patients with GIP has demonstrated that tungsten and/or cobalt is distributed in the giant cells and centrilobular fibrosing lesion in GIP. Pneumoconiosis, caused by amorphous silica, and acute interstitial pneumonia, associated with the giant tsunami, were also elementally analyzed by EPMA-WDS. The results suggest that commonly found elements, such as silicon, aluminum, and iron, may cause occupational and environmental lung diseases.

X-ray microanalysis in the scanning electron microscope.

X-ray microanalysis conducted using the scanning electron microscope is a technique that allows the determination of chemical elements in bulk or semi-thick specimens. The lowest concentration of an element that can be detected is in the order of a few mmol/kg or a few hundred parts per million, and the smallest amount is in the order of 10(-18) g. The spatial resolution of the analysis depends on the thickness of the specimen. For biological specimen analysis, care must be taken to prevent displacement/loss of the element of interest (usually ions). Protocols are presented for the processing of frozen-hydrated and freeze-dried specimens, as well as for the analysis of small volumes of fluid, cell cultures, and other specimens. Aspects of qualitative and quantitative analysis are covered, including limitations of the technique.

Evaluation of the mechanical properties and porcelain bond strength of cobalt-chromium dental alloy fabricated by selective laser melting.

STATEMENT OF PROBLEM: Limited information is available regarding the microstructure and mechanical properties of dental alloy fabricated by selective laser melting (SLM). PURPOSE: The purpose of this study was to evaluate the mechanical properties of a cobalt-chromium (Co-Cr) dental alloy fabricated by SLM and to determine the correlation between its microstructure and mechanical properties and its porcelain bond strength. MATERIAL AND METHODS: Five metal specimens and 10 metal ceramic specimens were fabricated to evaluate the mechanical properties of SLM Co-Cr dental alloy (SLM alloy) with a tensile test and its porcelain bond strength with a 3-point bending test. The relevant properties of the SLM alloy were compared with those of the currently used Co-Cr dental alloy fabricated with conventional cast technology (cast alloy). The Student t test was used to compare the results of the SLM alloy and the cast alloy (α=.05). The microstructure of the SLM alloy was analyzed with a metallographic microscope; the metal ceramic interface of the SLM porcelain bonded alloy was studied with scanning electron microscopy, energy dispersive x-ray spectroscopy, and an electron probe microanalyzer. RESULTS: Both the mean (standard deviation) yield strength (884.37 ± 8.96 MPa) and tensile strength (1307.50 ±10.65 MPa) of the SLM alloy were notably higher than yield strength (568.10 ± 30.94 MPa) and tensile strength (758.73 ± 25.85 MPa) of the currently used cast alloy, and the differences were significant (P<.05). The porcelain bond strength of the SLM alloy was 55.78 ± 3.02 MPa, which was similar to that of the cast alloy, 54.17 ± 4.96 MPa (P>.05). Microstructure analysis suggested that the SLM alloy had a dense and obviously orientated microstructure, which led to excellent mechanical properties. Analysis from scanning electron microscopy, energy dispersive x-ray spectroscopy, and the electron probe microanalyzer indicated that the SLM alloy had an intermediate layer with elemental interpenetration between the alloy and the porcelain, which resulted in an improved bonding interface. CONCLUSIONS: Compared with the currently used cast alloy, SLM alloy possessed improved mechanical properties and similar porcelain bond strength.

Quantitative cryo-analytical scanning electron microscopy (CEDX): an important technique useful for cell-specific localization of salt.

Advances in the techniques required for the X-ray microanalysis of cryo-fixed, naturally hydrated plant tissues in the cryo-scanning electron microscope have reached the stage that accurate, cell-specific localization and quantification of the nutrient and toxic elements can be achieved. Advances are described in the successive processes of cryo-fixation, cryo-planing to produce flat surfaces, monitored minimal etching to reveal cell outlines, coating with aluminum, spectrum collection, and quantification by comparison with comparable frozen standard solutions of the elements.

Investigation of the distribution of elements in snail shell with the use of synchrotron-based, micro-beam X-ray fluorescence spectrometry.

In this study, synchrotron-based micro-beam was utilized for elemental mapping of a small animal shell. A thin X-ray spot of the order of approximately 10microm was focused on the sample. With this spatial resolution and high flux throughput, the X-ray fluorescent intensities for Ca, Mn, Fe, Ni, Zn, Cr and Cu were measured using a liquid-nitrogen-cooled 13-element energy-dispersive HpGe detector. The sample is scanned in a 'step-and-repeat' mode for fast elemental mapping and generated elemental maps at 8, 10 and 12keV. All images are of 10microm resolution and the measurement time was 1s per point. The accumulation of trace elements was investigated from the soft-tissue in small areas. Analysis of the small areas will be better suited to establish the physiology of metals in specific structures like small animal shell and the distribution of other trace elements.

A capacitive probe with shaped probe bias for ion flux measurements in depositing plasmas.

The application of a pulse shaped biasing method implemented to a capacitive probe is described. This approach delivers an accurate and simple way to determine ion fluxes in diverse plasma mixtures. To prove the reliability of the method, the ion probe was used in a different configuration, namely, a planar Langmuir probe. In this configuration, the ion current was directly determined from the I-V characteristic and compared with the ion current measured with the pulse shaped ion probe. The results from both measurements are in excellent agreement. It is demonstrated that the capacitive probe is able to perform spatially resolved ion flux measurements under high deposition rate conditions (2-20 nm/s) in a remote expanding thermal plasma in Ar/NH(3)/SiH(4) mixture.

Electron probe X-ray microanalysis for the study of cell physiology.

Of the analytical electron microscopy techniques available, electron probe X-ray microanalysis has been most widely used for the study of biological specimens. This technique is able to identify, localize, and quantify elements both at the whole cell and at the intracellular level. The use SEM or TEM to analyze individual whole cells gives a simple and rapid method to study changes in ion transport after stimulation, whereas the analysis of thin sections of cryoprepared cell sections, although technically more difficult, allows details about ionic content in intracellular compartments, such as mitochondria, ER, and lysosomes, to be obtained. In this chapter the principles underlying X-ray emission are briefly outlined, step-by-step methods for specimen preparation of whole cells and cell sections for microanalysis are given, as are the methods used for deriving quantitative information from spectra. Areas where problems might occur have been highlighted. The different areas in which X-ray microanalysis is being used in the study of cell physiology are briefly reviewed.

Quantitative phase imaging with a scanning transmission x-ray microscope.

We obtain quantitative phase reconstructions from differential phase contrast images obtained with a scanning transmission x-ray microscope and 2.5 keV x rays. The theoretical basis of the technique is presented along with measurements and their interpretation.

X-ray microanalysis in the scanning electron microscope.

X-ray microanalysis conducted using the scanning electron microscope is a technique that allows the determination of chemical elements in bulk or semithick specimens. The lowest concentration of an element that can be detected is in the order of a few mmol/kg or a few hundred parts per million, and the smallest amount is in the order of 10(-18) g. The spatial resolution of the analysis depends on the thickness of the specimen. For biological specimen analysis, care must be taken to prevent displacement/loss of the element of interest (usually ions). Protocols are presented for the processing of frozen-hydrated and freeze-dried specimens, as well as for the analysis of small volumes of fluid, cell cultures and other specimens. Aspects of qualitative and quantitative analysis are covered, including limitations of the technique.

Diagnosing pure-electron plasmas with internal particle flux probes.

Techniques for measuring local plasma potential, density, and temperature of pure-electron plasmas using emissive and Langmuir probes are described. The plasma potential is measured as the least negative potential at which a hot tungsten filament emits electrons. Temperature is measured, as is commonly done in quasineutral plasmas, through the interpretation of a Langmuir probe current-voltage characteristic. Due to the lack of ion-saturation current, the density must also be measured through the interpretation of this characteristic thereby greatly complicating the measurement. Measurements are further complicated by low densities, low cross field transport rates, and large flows typical of pure-electron plasmas. This article describes the use of these techniques on pure-electron plasmas in the Columbia Non-neutral Torus (CNT) stellarator. Measured values for present baseline experimental parameters in CNT are phi(p)=-200+/-2 V, T(e)=4+/-1 eV, and n(e) on the order of 10(12) m(-3) in the interior.

X-ray microanalysis of biological material in the frozen-hydrated state by PIXE.

Elemental microanalysis of biological material in the frozen-hydrated state using in-vacuum proton induced X-ray emission is described for the first time. For this purpose, a commercially available cryotransfer system was modified and coupled to the experimental chamber of the nuclear microprobe (NMP). The analyzed material was frozen in propane cooled by liquid nitrogen, fractured, carbon coated, and transferred onto the cold stage (100 K) of the nuclear microprobe chamber. Micro-PIXE and simultaneous proton backscattering was performed using a 3 MeV proton beam. Quantitative results were obtained by the standardless method, and tested using 20% gelatin standards. Monitoring of the gas composition inside the system by means of mass spectrometry performed before, during, and after proton bombardment showed good stability of the analyzed material for proton currents not exceeding 150 pA. Average concentrations of light elements (C, N, O, and indirectly H) were also obtained by the proton backscattering technique. No losses of elements measurable by particle-induced X-ray emission (PIXE) during proton irradiation were found during repetitive, short analyses of the same micro areas of gelatin standards. Measurements of thick sections of selected plant and animal material in the frozen-hydrated state-leaf sections of the plant Senecio anomalochrous Hilliard (Asteraceae) and larvae of Chysolina pardalina Fabricius (Chrysomelidae)-showed very good preservation of morphology and elemental distribution. Limits of detection of the order of a few micro g g(-1) were obtained for most elements.

Mineral concentration of natural human teeth by a commercial micro-CT.

This study aimed to evaluate a commercial micro-CT system (microCT 20) for quantitative analysis of mineral concentration in human enamel and dentin using different methodologies, and thereby compare the obtained results with established data from published literature. A micro-CT device set at 50 kVp (160 microA) was used to scan five whole molars (G1) and five molars ground to 6-mm thickness (G2), as well as evaluate the mineral concentration of the samples. Mean mineral contents for enamel and dentin were 2.57 (+/- 0.12) and 1.53 (+/- 0.12) g/cm3 for G1, and 2.76 (+/- 0.03) and 1.45 (+/- 0.02) g/cm3 for G2. Difference between the groups was significant for enamel. For dentin, there was a clear although not significant tendency towards higher values with G1. The equipment could identify and differentiate a higher mineral content of the tooth enamel and dentin from the external to the inner tissue. Further, the absolute mean values of mineral concentration were lower in whole tooth samples than in sectioned samples due to beam hardening. In conclusion, the equipment is well suited for quantifying the mineral content of teeth. However, it is necessary to consider the limited acceleration voltage of the microCT 20 system and to limit sample evaluation to 6-mm thickness.

The efficiency of X-ray microanalysis in low-vacuum scanning electron microscope: deposition of calcium on the surface of implanted hydrogel intraocular lens (IOL).

To examine the calcification of implanted hydrogel IOL by X-ray microanalysis, we compared conventional transmission electron microscopy (TEM) with low-vacuum scanning electron microscopy (SEM). We also compared metal coating with non metal coating in low-vacuum SEM. Calcification of IOL showed deposits which were located in the superficial substance of lens. In conventional TEM and X-ray microanalysis, calcium, phosphate and silicon were detected in the deposits. In low-vacuum SEM, the deposits detected in metal coating were calcium, phosphorus, sodium and magnesium, but not silicon. However, in non metal coating, the deposits contained not only calcium, phosphorus, silicon, sodium and magnesium, but also fluoride, aluminum and argentums. It was concluded that in conventional TEM where a specimen is fixed and dehydrated in ethanol, various elements leak out. On the other hand, when a specimen is coated with carbon and gold palladium for SEM, light elements might not be detected in X-ray microanalysis. Low-vacuum SEM preparation does not need metal coating and low-vacuum SEM appears to provide a highly efficient method for X-ray microanalysis.

First data from a commercial local electrode atom probe (LEAP).

The first dedicated local electrode atom probes (LEAP [a trademark of Imago Scientific Instruments Corporation]) have been built and tested as commercial prototypes. Several key performance parameters have been markedly improved relative to conventional three-dimensional atom probe (3DAP) designs. The Imago LEAP can operate at a sustained data collection rate of 1 million atoms/minute. This is some 600 times faster than the next fastest atom probe and large images can be collected in less than 1 h that otherwise would take many days. The field of view of the Imago LEAP is about 40 times larger than conventional 3DAPs. This makes it possible to analyze regions that are about 100 nm diameter by 100 nm deep containing on the order of 50 to 100 million atoms with this instrument. Several example applications that illustrate the advantages of the LEAP for materials analysis are presented.

An investigation of structural degradation of cerebrospinal fluid shunt valves performed using scanning electron microscopy and energy-dispersive x-ray microanalysis.

OBJECT: Surveys of cerebrospinal fluid (CSF) shunts that have been removed from patients have shown that even when the ventricular catheter is the cause of the obstruction, the valve may be obstructed or underperforming. The aim of this pilot study was to investigate the degradation of shunt valve structure over time due to the deposition of debris. The findings were compared with findings in unused valves. METHODS: Scanning electron microscopy was used to visualize the structures of the valves. The items that were examined included two unused and nine explanted cylindrical medium pressure valves, one unused and six explanted Delta 1.5 valves (PS Medical, Goleta, CA), and one explanted Medos Programmable valve (Codman Johnson & Johnson, LeLocle, Switzerland). The valves were cut open, disassembled, and coated in gold. The areas that were analyzed included the main valve chamber, the diaphragm unit, and the antisiphon device. For areas with abnormal deposits, energy-dispersive x-ray microanalysis was performed to establish the chemical composition of the deposits. The reference unused valves had smooth surfaces with no deposits in any areas. All explanted valves had extensive deposits in all surveyed areas. The deposits varied from small clusters of crystals to large areas that displayed a cobblestone appearance. In diaphragm valves the deposits extensively affected the surface of the diaphragm and the gap between the diaphragm and the surrounding case, where normally CSF flows; in the Medos valve the deposits affected in the spring and "staircase" unit. Deposits were present as early as 2 weeks after implantation. On some valves there was a complete film covering the entire outlet of the valve, which formed a cast inside the valve stretching from wall to wall. The deposits consisted mostly of sodium and chloride, but occasionally contained calcium. In all infected and some noninfected valves there was a significant peak of carbon, indicating the presence of protein deposits. CONCLUSIONS: It appears that the continuous flow of CSF through shunt valves causes surface deposits of sodium chloride and other crystals on all aspects of the valve, including the outlet pathways. The formation of deposits may be encouraged by the adhesive properties of the materials that constitute the valve parts.