Horizontal incidence observation of magnetic field by scanning electron microscope.

AbstractAimMagnetotactic bacteria are gram-negative, prokaryotic organisms which align themselves according to the Earth’s geomagnetic field. They contain organelles called magnetosomes which produce nano-magnetites by the mechanism of biomineralization. These nano-magnetites are arranged in the form of well-ordered chain called magnetosome chain, which are held together by intermolecular forces. The growth of these bacteria is stringent to specific oxygen gradient regions, where there is oxic-anoxic transition zone. In this paper, we report the cultivation and characterisation of magnetotactic bacteria that was accomplished under laboratory conditions and scanning electron microscope respectively.MethodologyBacterial soil samples were collected and cultivated under laboratory conditions using a precise and cost-effective media formulation using coffee bean extract and ferric chloride, which were to provide sufficient iron under the influence of external magnetic field. Experiments were conducted using media, deficient with ferric chloride and coffee bean solution, as control. Pour plate method was carried out for the growth of bacteria under the influence of external magnetic field provided on one-end of the petri-plate.ResultWe observed the growth of the cultivated bacteria in the proximity of the magnetic field only in the presence of iron in media. This emphasises that the media formulated was appropriate for the growth of bacteria under laboratory conditions. Scanning electron microscope analysis confirmed the presence of magnetosome chains in magnetotactic bacteria.InterpretationIn this research, the bacteria were able to sustain in artificial oxygen-transition zones provided in the laboratory. The coffee bean solution contained quinic acid and succinic acid, which along with ferric chloride provided iron in the form of ferric quinate, and succinic acid which are the major sources of growth for the bacteria. Even though magnetosome research has shown promising advances, one of major limitations in its commercialization is its difficulty in cultivation under laboratory conditions.

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In-Lens Low-Loss Electron Detector for the Upper Specimen Stage in the Scanning Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100180665 ◽

1990 ◽

Vol 48 (1) ◽

pp. 382-383

Author(s):

Oliver C. Wells ◽

Françoise K. LeGoues ◽

Rodney T. Hodgson

Keyword(s):

Magnetic Field ◽

Electron Microscope ◽

Scanning Electron Microscope ◽

Chromatic Dispersion ◽

Incident Beam ◽

Objective Lens ◽

Low Loss ◽

Backscattered Electrons ◽

Energy Filtering ◽

Scanning Electron

For the best resolution in either the scanning electron microscope (SEM) or the transmission electron microscope (TEM) the sample must be mounted in the high-field region of a condenser-objective lens. Detectors for either the secondary electrons (SE) or the backscattered electrons (BSE) in the SEM must allow for the fact that both of these are strongly deflected by the focusing magnetic field of the lens. Typically the SE are collected above the lens, while the BSE are collected using either diode(s) or scintillator(s) between the polepieces.Low-loss electrons (LLE) are scattered from a solid target with an energy loss of less than a few percent of the incident beam energy. These can be collected from a steeply tilted sample from below the exit polepiece of a condenser-objective lens. A suggestion to use the second half of the lens field as an energy filter was shown to by Munro to be unlikely to work because the chromatic dispersion of this part of the lens field is insufficient.The magnetic field of a condenser-objective lens can provide energy filtering as follows.A flat sample is mounted at typically 25° to 30° from the horizontal at or near the center of the lens. Figure 1 shows the trajectories of the electrons scattered with no loss of energy as calculated by Munro. These electrons are confined within a “containment region” with a well-defined boundary beyond which they cannot go. If a suitable detector is placed just inside the surface of this region then it will collect LLE. The slower BSE are confined within a smaller region and so are not collected.

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Effects of Pulsed Magnetic Field on Crystallization Properties of Polyphenlene Sulfide

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.332-334.1627 ◽

2011 ◽

Vol 332-334 ◽

pp. 1627-1630

Author(s):

Xing Huang ◽

Jun Lu ◽

Ting Gao ◽

Chang Fa Xiao ◽

Li Liu

Keyword(s):

Magnetic Field ◽

Electron Microscope ◽

Scanning Electron Microscope ◽

Isothermal Crystallization ◽

Pulse Magnetic Field ◽

Polyphenylene Sulfide ◽

X Ray Diffraction ◽

X Ray ◽

Crystallization Properties ◽

Scanning Electron

Crystallization properties of polyphenylene sulfide (PPS) during the isothermal crystallization at 245°C in the pulse magnetic field is studied by using X-ray diffraction, polarization microscope(POM), scanning electron microscope(SEM) and differential scanning calorimeter (DSC). We came to the conclusions that crystallization properties of PPS are changed under the influence of magnetic field; magnetic field promotes the perfection of the crystalline structure but inhibits the crystallinity.

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