Abstract: In this study, we investigate the principle of the annular aperture and polarization gating methods for microscopic imaging through a turbid medium using images simulated by a modified Monte Carlo program. Significant improvement in image quality is shown when thin annular apertures are used in the illumination and detection paths of a microscopic imaging system. The polarization gating method is proven to be an efficient gating method for selecting ballistic photons that carry the information of an object embedded in a turbid medium. We also demonstrate that the combination of the annular aperture and polarization gating methods is highly efficient in suppressing the scattered light in microscopic imaging through a turbid medium. It is also revealed that a pinhole used in a confocal microscope plays an independent angle-gating role.

Abstract: Multiple linear least squares (MLLSQ) and sequential simplex spectral processing procedures were used in an electron probe energy-dispersive (EDS) analysis of a 2223 Bi-Sr-Ca-Cu-O (BSCCO) high Tc superconductor specimen. This phase is normally difficult to quantify by EDS at voltages below 25 kV because of the severe overlap of the BiM lines with the M lines from a small amount of Pb that is added to the phase for stability. Quantitative results from the MLLSQ spectral processing and ZAF matrix correction procedures agreed well with wavelength-dispersive analysis (WDS) of the same specimen.

Abstract: Quantitative X-ray microanalysis is used to obtain the elemental compositions of tissues and cells. Concentrations are calculated on the basis of volume (mmolL−1 of packed cells) and mass (mmolkg−1 dry weight). Elemental maps are obtained by using a computer to control the position of a beam in an electron microscope and to record the signals from the scanning transmission electron microscope (STEM) and energy dispersive X-ray spectrometer (EDS) X-ray detectors. These X-ray images provide better visualization of elemental distributions than ``spot'' mode analysis by analyzing thousands of spots sequentially. When concentrations are determined on the basis of volume, it is assumed that the section thickness created during cryosectioning, and shrinkage during freeze-drying of a frozen section, are uniform. These assumptions have been examined with a nucleated red blood cell model. Even distributions of cytoplasmic Fe and K, which we observed, can only occur if cryomicrotomy produces sections with smooth surfaces and uniform thickness. In addition, by using bone marrow cryosections we have found that the relative shrinkage between nucleated and non-nucleated cells is similar. Therefore, the assumptions made about volume calculations do appear to be reasonable under the conditions used in this study.

Abstract: A novel method for the synthesis of polypeptides using polystyrene/divinylbenzene copolymers as solid supports has drawn the attention of medicinal, pharmaceutical, and agricultural chemists because of its utility in combinatorial chemistry and parallel synthesis. In this method, arrays of solid-phase organic synthesis experiments are conducted simultaneously thereby enabling the preparation of large numbers of novel compounds over a short time period. The analysis of organic compounds attached to polymer supports presents unique challenges to chemists. This study presents some results of the application of energy-dispersive X-ray spectrometry (EDS) in the environmental scanning electron microscope (ESEM) to this problem. EDS in the ESEM has the advantages of minimal sample size, speed, and simplicity because the analyses are performed without special specimen preparation. The progress of a two-step synthetic transformation was followed using EDS-ESEM by the presence of a sulfur peak in the first synthetic step and by a bromine peak in the second step. The synthetic products were also evaluated by infrared spectroscopy and by elemental analysis (ion chromatography). The agreement of the qualitative analysis among all three techniques was good. Analysis by EDS-ESEM not only complements current analytical techniques in solid phase synthesis; it also provides insight into the details of the synthetic transformation.

Abstract: The traditional methods for studying polymer microstructure in the transmission electron microscope largely hinge on the use of differential heavy-element staining to induce amplitude contrast. However, adequate staining agents are not available for all polymer systems. Furthermore, nonlinearities in the distribution of stain, particularly at interfaces, degrade the achievable resolution. Spatially resolved electron energy loss spectroscopy (EELS), on the other hand, provides a new opportunity to study polymer microstructure by providing rich spectroscopic features and high spatial resolution. Translating this opportunity into practice is underpinned by three main factors: (1) the availability of spectral fingerprints distinguishing various polymers; (2) the limits of achievable resolution; and (3) the ultimate constraints imposed by electron irradiation. This study discusses these issues and demonstrates the use of spatially resolved EELS with examples from hydrocarbon homopolymer and homopolymer blends of polyphenylene sulfide (PPS) and polyethylene terephthalate (PET), nylon 6/high-density polyethylene (HDPE) and polystyrene/polyethylene (PS/PE).

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