摘要:

SUMMARYA mathematical model for the electron beam heating problem of thick specimens (thickness less than the electron range) in the cold stage of SEM/STEM is proposed, and an analytic solution for the problem is provided. The use of the model is demonstrated by calculating the maximum temperature rise in a red blood cell mounted on a metallized polymer film, for a large range of operating conditions. With a probe size of 20 nm and probe current of less than 10 nA the temperature rise was found to be on the order of 5 K. This temperature rise increases proportionally to the probe current if all other variables are kept constant. Although the amount of energy dissipated in thick specimens is large relative to thin films, temperature rise can be minimized by mounting the thick sample on a metal stub or on a metallized film thus providing large heat transfer area through a high thermal conductivity substrate. Of course our calculations only have meaning if the specimen is in good thermal contact with the underlying support.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00056.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe usefulness of hollow cone dark field imaging for the study of Pd catalyst particles on γ‐alumina substrates is investigated. By varying the depth of the specimen in the objective lens field, different Bragg reflections can be conveniently selected. Typically, about 70% of the particles appear in either the 111 or 200 Bragg reflections. Rather more particles can be visible in bright field because of other Bragg reflections as well as absorption effects. Size distributions in bright field and dark field are compar

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00057.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA direct approach to quantitative measurements of uniform regions in thin sections is described. Accelerating voltages around 80 kV and objective aperture angles of about 9·3 mrad will provide conditions where contrast is directly proportional to specimen mass thickness. An extensive treatment of electron scattering in Formvar films for wide ranges of electron microscopic operating conditions is summarized in a simple, empirical equation. The extent to which Formvar results may be generalized to other materials, both embedding media and structures within the thin section, is treated. Using these results, precise measurements of local section thickness and of specimen density and/or dry mass of regions which penetrate the entire section thickness are possible, with the accuracy dependent upon irradiation effects and specimen makeup

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00058.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYTwo different freeze‐fracture methods are explored for preparation of biological material for scanning electron microscopy. In the simpler method the tissues are first fixed and dehydrated. They are then frozen and fractured, and after thawing, critical‐point dried. This method has already been used in a number of studies of animal tissues (heart, liver, kidney). It is applied here to the examination of plant material (leaf mesophyll cells). In the second method tissues, or cells, are first infiltrated with cryoprotectant (dimethylsulphoxide) then frozen and fractured, and not fixed until after thawing. The fixed tissues are finally dehydrated and critical‐point dried. This method also has previously been used in the study of animal tissues, and is applied here to carrot protoplasts, chicken erythrocytes, and leaf mesophyll

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00059.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA method of mounting small fragile components in an optically clear medium has been developed which results in good edge retention on an undistorted specimen.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00060.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYPhotoelectron micrographs of fixed, unstained, uncoated chicken embryo fibroblasts and the absolute photoelectron quantum yields in the 180–230 nm wavelength band ofl‐fucose,d‐galactose,d‐glucose,n‐acetyl‐d‐glucosamine, and the sucrose polymer Ficoll are reported. The quantum yields of the saccharides are low compared to the reference dye, phthalocyanine, and fall in the same range as those previously measured for amino acids and membrane phospholipids. Photoelectron micrographs of the unstained and uncoated cells exhibit considerable surface detail. The photoelectron quantum yield data and the micrographs indicate that surface relief is the dominant sourc

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00061.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA description is given of a family of test‐frames for obtaining an unbiased estimate of the numerical density of arbitrary profiles on a section. The counting rule pertaining to the test‐frame is simple and requires no corrections based on other estimated quantit

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00062.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA simple illumination system is described that can be easily adapted to a laboratory stereomicroscope allowing for low power high contrast dark field surveying. The system uses commercially available fibre optic lamps, standard bright field objectives and produces a large, evenly illuminated field suitable for photography.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00063.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe cyanide method is highly recommended for the purposes of the removal of gold coatings from SEM specimens prior to (a) further treatment before further SEM, and (b) staining and mounting for LM.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00064.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYSerum from viral suspensions is precipitated by shaking with Freon 112, and after concentration the virus is observed by immune electron microscopy.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00065.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY