摘要:

SUMMARYUranyl and europium ion‐doped fibres of 5–45 μm diameter were prepared which emit in the green and red spectral regions, respectively. Measurements were made of fluorescence flux as a function of fibre length, dopant concentration, slit shape and fibre diameter. The flux was found to be proportional to fibre length and fluorophor concentration and proportional to the square of the fibre radius. In addition, the fluorescence flux as a function of aperture size and shape and fibre position has been measured experimentally and compared to computer generated fluorescence flux envelopes. It is suggested that inorganic ion‐doped fibres are suitable for use as microspectrofluorimetric sta

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03986.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA low‐temperature freeze‐drying or freezing preparation chamber and specimen stage has been designed and constructed for use with an electron microscope. The system allows biological specimens to be prepared under conditions of temperature and pressure and their subsequent direct transfer to a cold stage maintained at — 175°C within the microscope. Attachment of both the chamber and stage is a simple procedure and does not interfere with the normal electrical and mechanical operation of the microscope.The stage is cooled with the aid of a liquid nitrogen reservoir system and can be maintained at — 175°C for about 80 min without the use of any continuous cooling system. Test specimens have shown that a resolution of about 1.0–1.5 nm can be maintained at — 175°C for 80 min once thermal equilibrium has be

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03987.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYSingle electrons of the energies used in transmission electron micrography can render developable one or more emulsion grains. From this fact the following deductions can be made.(a). Photographic contrast in an electron micrograph is a function of the mean density only.(b). The signal/noise ratio in an electron micrograph improves with increasing exposure, irrespective of the means adopted to enable an increased exposure to be used.(c). If the exposure of the specimen is limited to some maximum then the visibility of noise‐limited detail in prints representing a given total magnification is independent of the negative material used in the microscope.Experimental tests based largely on electron micrographs are presented which provide good support for these deductions. It is generally concluded that the behaviour patterns examined in this work should always be considered when limitations are being encountered in the image quality of electron micr

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03988.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARY1A method is described for counting nuclei in wax‐embedded histological sections of epithelium. The counts are independent of section thickness over a wide range (4–10 μm).2Counts of nuclei were made in villi and crypts of rat small intestine fixed either collapsed or distended by a hydrostatic pressure equivalent to 350 mm of water. There was no significant difference between the counts of nuclei in collapsed or distended gut.3Distension reduced the absolute height of villi, and increased their absolute width at the base.4The implications of these findings for studies of the morphological basis of intestinal adaptation are discu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03989.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYLet λ denote a rectifiable line in a plane for which the length per unit area is to be estimated by counting the intersections with random test lines dropped on the plane. The asymptotic distribution and variance of the number of intersections with a single test line is derived for a model which assumes λ to be the boundary of particles or random area. Numerical examples illustrate the applicability of the derived variance expressio

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03990.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYMethods have been developed for the estimation of section thickness, and of the mass‐thicknesses, and hence the masses, of material embedded in sections. They are based on the current densities measured with a Faraday‐cage or on a new approximation for the relationship between exposure and optical density (OD) of the electron microscopical plate, which is valid for OD<5. This relationship is quite distinct from the response to light, and also from an approximation for electrons which was only valid for OD<1.2, and which was the basis for an earlier method.The old methods and the two groups of new ones were tested, and also compared with the interference microscope. It was found that all but one of the new methods, in both groups, were homogeneous; the older methods and the interference microscope differed very significantly between themselves and with the homogeneous methods. The errors in the interference microscopical estimations were almost certainly due to the presence of embedded material in the sections, which could not be detected with the interference microscope because of its low resolution and the poor contrast in the thin sections. (A second set of experiments using only pure resin gave a good agreement between the homogeneous methods and the interference microscope.)The orders of accuracy of the methods are quite high. A measurement repeated twelve to thirty‐five times will yield a value which has a 95% chance of being within 5% of the true value, while a single observation has a 95% chance of being within ∼ 25% of the true value with most methods, while some place it within ∼ 10%. Simplified, but less accurate, applications of the methods are also

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03991.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe aims in a current study of dermis and scar tissue using the scanning electron microscope are:1to maintain the orientation of the specimen2to preserve thein vivoarchitecture, and3to expose a satisfactory surface.A technique which best fulfils these requirements involves glutaraldehyde fixation of a splinted specimen, freeze‐fracturing using a modified pair of pliers, freeze‐drying, incubation in a buffered saline solution of hyaluronidase and freeze‐drying again after washing.Consistently satisfactory specimens have been obtained, which provide information about fibre architecture and cell distrib

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03992.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA simple method is described for adapting the Leybold complementary replica device, which is equally useful for the examination of suspensions and tissue fragments, to the Balzers freeze‐etching unit. The only change necessary for using the device in the Balzers unit, is to unscrew the Balzers specimen table from the cold stage and replace it with an adapter. If prolonged etching is required, a contamination shield is mounted on the microtome arm in place of the razor blad

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03993.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe thickness of ultrathin tissue sections embedded in Epon‐Araldite and cut with a diamond knife was measured by re‐sectioning and electron microscopic examination of the section profiles. A secondary section mounted on a Formvar‐coated slot grid provided enough normally cut segments (seven to seventeen) for measurements giving a precise estimate of mean thickness, comparable to that obtainable by interference microscopy (±2.3% or less for grey to dark gold sections). The standard deviation of section thickness within sections was never more than 5 nm, corresponding to a coefficient of variation of 6.5% or less for sections more than 48 nm thick. This suggests that variation in section thickness, within sections, may be less than has been supposed, so that quantitative work may be based on thickness measurements made over a limited representative area. A silver interference colour was associated with sections 49–60

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03994.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA specimen holder has been designed specifically to contain small particulate matter, such as microorganisms, fibres or powders, during the fluid exchange cycle and final evaporation step of the critical point drying process. The mode of fluid exchange is positive displacement rather than diffusion. The holder can accommodate up to ten different samples without loss of material or cross‐contamination during the dehydration process. The samples are separated by silver membrane filters, and fluid exchange is accomplished in minimal time by only slight positive pressure. Experiments with soluble dyes have shown that any fluid can be displaced completely with another in less than 2 min, whereas diffusion requires more than 30 min. The holder and individual capsules have been tested with different materials and a standard water/ethyl alcohol/amyl acetate/carbon dioxide fluid sequence. This paper describes the design, production, and testing of the holder and capsules, and presents selected examples of result

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb03995.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY