Confocal fluorescence microscopy using spectral and lifetime information to simultaneously record four fluorophores with high channel separation

We demonstrate the possibility to increase substantially the number of simultaneously detected fluorophores by utilizing both spectral and lifetime information. Using a two-detector confocal scanning laser microscope, experiments confirm that four different fluorophores can be detected with good channel separation. The signal-to-noise ratio (SNR) of the recorded images is investigated both theoretically and experimentally. It is found that in order to obtain a high SNR fluorophore lifetimes should differ by approximately an order of magnitude.     

Methods for large data volumes from confocal scanning laser microscopy of lung

Confocal scanning laser microscopy makes it possible to obtain series of optical sections in precise registration. Certain studies of lung parenchyma, however, require both the fine resolution obtainable with high-numerical-aperture (NA) objectives and the extensive fields of view that usually would be achieved only with low-NA objectives. This article presents a technique that resolves this conflict by using a sequence of operations: (i) to correct intensity variations on individual sections due to non-uniform illumination/detection characteristics of the microscope; (ii) to correct intensity variations between successive sections in a series due to, for example, depth-related absorption or step changes in detector sensitivity; (iii) to adjust adjacent, overlapping stacks of sections to a common intensity level; and (iv) to fuse a group of such overlapping stacks into a single series of larger sections. This resulting stack may contain, for example, a complete cross-section of an alveolar ductal unit about 500 μm or more in diameter at about 1-μm pixel resolution.     

FUZZY SYSTEMS: BASIS FOR A MODELING METHODOLOGY?

Modeling becomes a key methodological issue when we have to deal with large, complex and ill-structured problems. The traditional analytic approach to modeling aims at capturing the aggregate logic of a problematic situation, which is taken to represent the essence of the problem. The aggregate logic does not, and should not, describe the full complexity of the modeling situation, but should give a sufficient basis for finding an optimal solution to the problem. In recent criticism, however, it is pointed out that the analytic approach does not give an adequate basis for solving complex and ill-structured problems, and a systems approach is recommended. Checkland finds that the so-called hard systems thinking is no better than the analytic approach and introduces a soft systems methodology. In this paper a fuzzy systems approach is found to be more flexible than the analytic and the hard systems methods, but more precise and easier to validate than the soft systems approach.     

The Nature and Importance of Economic Competence

In this paper we define economic competence as the ability toidentify, expand and exploit business opportunities. Economiccompetence constitutes the means through which technologicalpossibilities are converted into economic activity. It consistsof four types of capabilities: (i) selective or strategic; (ii)organizational or coordinating; (iii) technical; and (iv) learningability. The purpose of the paper is (i) to survey the studyof economic competence as it appears in economic literature;(ii) to give a meaningful and operational definition of economiccompetence as one of the factors contributing to macroeconomicgrowth; and (iii) to suggest a methodology to generalize andlink economic competence, as defined at the micro (firm, individual)level, to macroeconomic growth, through simulation on the micro-basedmacroeconomic Model of the Swedish Economic System (MOSES).     

Mechanical Properties of Liquid-Phase-Bonded Copper-Ceramic Substrates

Liquid-phase bonding of copper foils to ceramic substrates is a very attractive technique for the fabrication of metallized substrates for hybrid power electronics applications. The design and reliability considerations of such substrates necessitate the knowledge of their mechanical properties. Therefore, stresses and strains in the copper and in the ceramic of bonded substrates were investigated. Theoretical calculations are presented to support the experimental results and to find the influence of stresses and strains in the fabrication of copper ceramic substrates using the liquid-phase-bonding technique.     

Supported metal sulphide nanoclusters studied by HAADF-STEM

The morphology of MoS₂ and WS₂ nanoclusters supported on high‐surface area graphitic carbon was investigated using high angular annular dark field scanning transmission electron microscopy (HAADF‐STEM). Most of the MoS₂ (WS₂) nanoclusters contain only a single S‐Mo‐S (S‐W‐S) layer and the most commonly encountered morphology is truncated triangular. This is in contrast to the hexagonal morphology of macroscopic MoS₂ (WS₂) crystals. When in addition to molybdenum (tungsten), nickel is also present, the regular nanoclusters are truncated to a larger extent, indicating that Ni has influenced the morphology by the formation of so‐called Ni‐Mo‐S (Ni‐W‐S) structures. For these structures, the additional truncations are observed to lead to dodecahedral‐like shapes.     

Simultaneous confocal recording of multiple fluorescent labels with improved channel separation

Confocal microscopes are often used to study specimens labelled with fluorophores. A commonly used method for simultaneous recording of the distribution of multiple fluorophores is to divide the fluorescent light emitted by the specimen into different wavelength regions using dichroic and bandpass filters. These different wavelength regions are then distributed to multiple detectors. However, the broad and overlapping spectra of commonly used fluorophores often result in considerable crosstalk between channels. A new technique, intensity-modulated multiple-beam scanning (IMS) microfluorometry, can be used to reduce this cross-talk substantially. The IMS technique is implemented with two laser beams of different wavelengths, intensity-modulated at different frequencies, which illuminate the specimen simultaneously. The two laser wavelengths predominantly excite one fluorophore each. Fluorescent light from the specimen is divided into two wavelength regions (red and green) which are detected by two photomultiplier tubes. The output signals from the photomultiplier tubes are connected to lock-in amplifiers. The effect of using modulated laser beams, in combination with lock-in amplifiers, is strongly to reduce cross-talk between the channels. The performance of the IMS technique using various types of specimen is compared with the results obtained using the conventional multi-detector method.     

Face/core interface fracture characterization of mixed mode bending sandwich specimens

Debonding of the core from the face sheets is a critical failure mode in sandwich structures. This paper presents an experimental study on face/core debond fracture of foam core sandwich specimens under a wide range of mixed mode loading conditions. Sandwich beams with E‐glass fibre face sheets and PVC H45, H100 and H250 foam core materials were evaluated. A methodology to perform precracking on fracture specimens in order to achieve a sharp and representative crack front is outlined. The mixed mode loading was controlled in the mixed mode bending (MMB) test rig by changing the loading application point (lever arm distance). Finite element analysis was performed to determine the mode‐mixity at the crack tip. The results showed that the face/core interface fracture toughness increased with increased mode II loading. Post failure analysis of the fractured specimens revealed that the crack path depends on the mode‐mixity at the crack tip, face sheet properties and core density.     

Effects of Inositol Tri-, Tetra-, Penta-, and Hexaphosphates on In Vitro Estimation of Iron Availability

The effects of inositol tri-, tetra-, penta-, and hexaphosphates on iron solubility were studied in vitro. Pure inositol phosphates (0.125–10 μmol) were added to 1g of freeze-dried wheat roll and digestion was performed simulating physiological conditions. Soluble iron was used as an index of iron bioavailability. The pure inositol phosphate fractions were prepared by hydrolysis of sodium phytate and separation on anion exchange resin. The inositol phosphates were identified and quantified by HPLC. Addition of 10 μmol inositol hexa- and pentaphpsphate reduced iron solubility from 39% (reference) to 0.2% and 6%, respectively, while the same amount of inositol tetra- and tri-phosphate slightly increased the iron solubility. Thus, degradation of inositol hexa- and pentaphosphates seemed to significantly reduce the inhibiting effect on iron availability.