A simple but precise method for quantitative measurement of the quality of the laser focus in a scanning optical microscope

We report a method for characterizing the focussing laser beam exiting the objective in a laser scanning microscope. This method provides the size of the optical focus, the divergence of the beam, the ellipticity and the astigmatism. We use a microscopic‐scale knife edge in the form of a simple transmission electron microscopy grid attached to a glass microscope slide, and a light‐collecting optical fibre and photodiode underneath the specimen. By scanning the laser spot from a reflective to a transmitting part of the grid, a beam profile in the form of an error function can be obtained and by repeating this with the knife edge at different axial positions relative to the beam waist, the divergence and astigmatism of the postobjective laser beam can be obtained. The measured divergence can be used to quantify how much of the full numerical aperture of the lens is used in practice. We present data of the beam radius, beam divergence, ellipticity and astigmatism obtained with low (0.15, 0.7) and high (1.3) numerical aperture lenses and lasers commonly used in confocal and multiphoton laser scanning microscopy. Our knife‐edge method has several advantages over alternative knife‐edge methods used in microscopy including that the knife edge is easy to prepare, that the beam can be characterized also directly under a cover slip, as necessary to reduce spherical aberrations for objectives designed to be used with a cover slip, and it is suitable for use with commercial laser scanning microscopes where access to the laser beam can be limited.     

IN-LINE MEASUREMENT OF THE REFINING EFFECT-AN IMPORTANT NEW TOOL FOR USE IN THE PULP AND PAPER INDUSTRY

ABSTRACT

In the production of paper, pulp fibers are put through a refining stage. This greatly enhances the fiber characteristics and the resulting quality and properties of the paper that is being produced.

This paper outlines the various detailed processes which occur during the refining stage and what the resulting effects are on paper quality. It discusses the measurements of 'freeness’ and 'drainage rate’, which are used today as the primary means of measuring the'refining effect’, and provides a brief evaluation of the effectiveness and limitations of these techniques.

With the Scanning Laser Microscope, one can now observe the 'refining effect’ on a microscopic basis by analyzing the structure of individual fibers. In particular one can measure the changes in the mean fiber diameter and the amount of fines that are produced. These changes are measured on a statistically significant basis in real time and provide valuable information for control of the refining process itself.

This paper reports actual test results and provides a preliminary analysis of the significance of these results and how the findings could best be implemented in an actual control strategy for operating a refiner.     

Different Sensitivities of Whitefish (Coregonus Lavaretus) and Northern Pike (Esox Lucius) Eleutheroembryos to Photoinduced Toxicity of Polycyclic Aromatic Hydrocarbons

The photoinduced toxicity of two polycyclic aromatic hydrocarbons (PAHs), retene (RET) and pyrene (PYR), to the eleutheroembryos of whitefish and northern pike was studied. Fish were exposed to three concentrations of RET and PYR, and irradiated with ultraviolet radiation (UVR) or visible light for 3 h on two consecutive days. UVR covered the absorption maxima of RET and PYR at UVB and UVA, the daily UVR doses were 30 and 28 kJ m^?2, respectively. After 72 h, mortality and behavioral abnormalities were observed. Survivors were analyzed for the proteins of CYP1A, CYP3A, Hsp70, and the activity of glutathione reductase (GR). While neither PAHs nor UVR on their own were lethal, simultaneous exposure caused mortality. The whitefish were more sensitive than the pike to the photoinduced toxicity, and PYR was much more phototoxic than RET. RET induced Hsp70 in both species, and PYR induced GR without UVR in pike.     

On one-leg methods for differential-algebraic equations

One-leg methods for general differential-algebraic equations are analyzed. Sufficient stability conditions are formulated for transferable differential-algebraic equations. A natural scaling is proposed to obtain matrices with uniformly bounded condition in the linear systems to be solved.     

The Aura of the Digital

The focus on computation in design is largely on technique, with designers everywhere now using the computer as a tool for aiding design and manufacture. Here, interactive media designer Jussi Ängeslevä shifts the emphasis on computation from design method to ‘meaning making’. He highlights how the work of his practice, Berlin-based ART+COM, transfers digital thinking in such a way as to express experience unfolding in space.     

Drying, Packaging, and Storage Effects on Quality of Basil, Marjoram and Wild Marjoram

Sorption isotherms, color and sensory qualities of basil (Ocimum basilicum L.) and marjoram (Origanum majorana L.) and sensory qualities of wild marjoram (Origanum vulgare L.) were used to determine effects of packaging, storage temperature and time on air-dried and freeze-dried herbs. Sorption isotherms showed herbs dried with different methods exhibited different sorption capacities. Both odor and taste of freeze-dried basil and the freeze-dried and air-dried marjorams were very sensitive to storage conditions. Processing and storage conditions had only moderate effects on flavor of wild marjoram. The study demonstrated that quality of dried basil, marjoram and wild marjoram could be maintained for 2 yr in air-tight packages at room temperature.