Effects of Annular Pupils on Confocal Fluorescent Imaging

Abstract

For a confocal fluorescent microscope with annular lenses, the effects of varying the radii of central obstruction of the annular lenses on three, two and one-dimensional imaging have been investigated in terms of the optical transfer function. In particular, we consider the effects of the central obstruction on the signal strength for a system with either a point or finite-sized detector. The signal level as a function of the detector and the central obstruction sizes is presented for volume, planar and point objects, respectively.     

Three-dimensional Imaging in Confocal Fluorescent Microscopy with Annular Lenses

Abstract

Three-dimensional imaging properties in confocal fluorescent microscope systems with annular lenses are investigated in terms of the three-dimensional optical transfer function (OTF). Starting from the OTF, we also consider the optical sectioning property. The dependence of the OTF and the optical sectioning strength on the radius of the central obstruction of the lens is revealed. For the case of a finite-sized circular pinhole in front of the detector, both the OTF and the optical sectioning strength, together with the signal level, are calculated as a function of the radius of the pinhole. Investigations show that for a given finite size of the pinhole, the optical sectioning strength can be increased by altering the radius of the central obstruction of the lens to an optimum value, and that a higher signal level may be maintained by using an annular objective only.     

Imaging Performance of Confocal Fluorescence Microscopes with Finite-sized Source

Abstract

The role of the illumination system of the confocal microscope, and in particular the first pinhole, is discussed. The effects of a finite sized source on the imaging performance, including the three-dimensional optical transfer function, are investigated. Two forms of source are considered, either a coherent Gaussian beam of finite size or an incoherent disc of finite size. For a confocal microscope using optical fibres as source and detector, the optimum geometry is derived for maximizing signal strength.     

Catalytic Electrophilic Halogenation of Silyl‐Protected and Terminal Alkynes: Trapping Gold(I) Acetylides vs. a Brønsted Acid‐Promoted Reaction

In the presence of a cationic gold(I) catalyst and N‐halosuccinimide, both trimethylsilyl‐protected and terminal alkynes are converted into alkynyl halides. Further experiments showed that silyl‐protected alkynes undergo electrophilic iodination and bromination under Brønsted acid catalysis, whilst terminal alkynes require a cationic gold catalyst. The former reactions probably proceed via activation of the electrophile, whilst the latter reactions proceed via a gold(I) acetylide intermediate. Gold‐catalysed halogenation was further combined with gold‐catalysed hydration and subsequent annulation to provide convenient routes to iodomethyl ketones and five‐membered aromatic heterocycles.     

Turbulent burning rates of methane and methane-hydrogen mixtures

Methane and methane-hydrogen (10%, 20% and 50% hydrogen by volume) mixtures have been ignited in a fan stirred bomb in turbulence and filmed using high speed cine schlieren imaging. Measurements were performed at 0.1 MPa (absolute) and 360 K. A turbulent burning velocity was determined for a range of turbulence velocities and equivalence ratios. Experimental laminar burning velocities and Markstein numbers were also derived. For all fuels the turbulent burning velocity increased with turbulence velocity. The addition of hydrogen generally resulted in increased turbulent and laminar burning velocity and decreased Markstein number. Those flames that were less sensitive to stretch (lower Markstein number) burned faster under turbulent conditions, especially as the turbulence levels were increased, compared to stretch-sensitive (high Markstein number) flames.     

Guidance for crystal ball gazers: developing a code of ethics for landscape visualization

Computer visualization of landscapes in three or four dimensions constitutes a “crystal ball” capable of showing us views into the future. This paper discusses the risks of the growing but unstructured use of these landscape visualizations as a popular decision-making and public communications tool in planning. The author argues that we need to establish a framework for guidance and supporting resources for the use of landscape visualization, including accepted procedures, training, appropriate databases, and a communication network for users. In particular, it is argued that the preparers of visualizations — whom we can think of as the “crystal ball gazers” who conjure up and interpret the imagery — need to be governed by a code of ethics for defensible landscape visualization.Drawing on research on visualization effectiveness and validity, as well as anecdotal evidence from professional practice, the paper identifies potential problems associated with emerging visualization technologies, and reviews the needs for, progress toward, and potential benefits of a support infrastructure for visualization preparers and presenters. A framework for guidance and support of visualization practitioners is proposed, in the hope of improving the chances of ethical practice and scientific validity in the use of these systems. Pending more comprehensive findings from the considerable body of research which is needed on this subject, an interim code of ethics is presented, for consideration, testing, and amendment by other researchers and users. It is suggested that such a code include broad principles and guidance on ethical conduct in producing visualizations, presenting them to viewers, and analysing responses to them from users as feedback.Implications for future research and practice are provided, with an emphasis on the urgent need for researchers to monitor and evaluate the use and influence of landscape visualizations in practice.     

Comparison of the genomic short regions of a vaccine strain (SA-2) and a virulent strain (CSW-1) of infectious laryngotracheitis virus (Gallid herpesvirus 1)

Restriction enzyme linkage maps were produced for the genomic short region of the virulent infectious laryngotracheitis virus (CSW-1 strain). After comparison with the equivalent restriction enzyme linkage maps for the infectious laryngotracheitis virus SA-2 strain (a vaccine strain), it was determined that the maps for the short regions of the two strains were identical, apart from a single section in each of the inverted terminal repeats. Each inverted terminal repeat of the SA-2 strain was discovered to contain 467 base pairs more DNA than the CSW-1 strain's inverted terminal repeats. This extra DNA was more precisely mapped entirely within the EcoRI fragments D and d of SA-2, which were found to form part of the SmaI fragments U and P of SA-2 and Q and b of SA-2 and to contain one SmaI restriction enzyme site.     

FOrmation and reactivity of oxides and basic salts. I. Basic magnesium chlorides and sulphates

Reactions of lime and magnesia with magnesium chloride and sulphate have been studied in relation to industrial processes, namely, extraction of magnesium from sea-water and production of Sorel-type cements. Variations in phase composition, surface area and crystallite and aggregate sizes of the products have been correlated with experimental conditions. The solid limes react rapidly with the more dilute magnesium salt solutions, and the precipitated magnesium hydroxides are much more finely-divided. Basic magnesium salts initially formed are decomposed subsequently to hydroxide as the pH becomes stabilised at higher values. Greater concentrations of magnesium chloride give more extensive basic salt formation and prevent all of the lime going quickly into solution. Similar products are given with solid magnesium hydroxide and magnesium chloride and sulphate solutions. The Sorel-type cements obtained from magnesium oxide and the more concentrated chloride solutions set appreciably, even before loss of surface through final ageing. They show two distinct phases: (a) irregular grains of 10–50 μm diameter, and (b) acicular or tabular crystals up to 20μm long, mainly in radiating growths. By contrast, the magnesium oxysulphate crystals are not so elongated and the cements set with considerable loss of surface area, giving interlocking structures in which 20–50 μm-diameter grains are often ‘fused’ together as larger 400–500 μm aggregates.