摘要:

SummaryA very sensitive method is described to measure the local rise in the temperature of a metal specimen during investigation in the electron microscope. The method is based on the known temperature dependence of the climb rate of Frank dislocation loops in materials with relatively high stacking fault energy. The climb rate of loops subject to the influence of the condensed electron beam is compared to the corresponding rate for loops in an area of the same specimen which is remote from the observation spot. From the difference in the logarithms of these rates the amount of local beam heating is determined. For a typical Al‐1.5 wt% Mg specimen under typical normal working conditions an average local rise in temperature of approximately 6°C was determin

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03973.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryCathodoluminescence spectra of a selected group of organic substances have been obtained on cooled samples using a SEM‐spectrometer combination. Room temperature spectra were also recorded when possible. The emission intensity and the beam effect are favourably influenced at low temperatures. The main emission occurs in the 300–600 nm wavelength ra

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03974.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryInstrumental factors affecting the precision and accuracy of measurements with the Vickers M86 scanning and integrating microinterferometer were investigated. ‘Spot’ measurements of OPD (optical path difference) could be made to a precision better than 0.001 Λ (wavelengths); the coefficient of variation of scanning measurements of IOPD (integrated OPD) depended on the object, typical values being approximately ± 5% for a human erythrocyte in water, and ± 10% for a mouse sperm head in water. Repeated measurements enabled the dry mass of a specimen to be estimated to any desired precision.Instrumental calibration to give results in absolute units is described. Early prototypes required frequent calibration, but with production instruments the calibration varies little from day to day, and very similar results are obtained if a specimen is measured in different parts of the scanned field.A slight, approximately sinusoidal deviation from linearity was sometimes observed when the apparent OPD or IOPD was plotted against expected values. The error, which probably occurs with all instruments employing a Jamin double‐refracting interference system, was maximally about ± 0.02 Λ for a specimen of true OPD 0.25 Λ or 0.75 Λ, but was zero for a specimen of true OPD 0.5 Λ. The error could be minimized or eliminated by the correct choice of an interference fringe for ‘spreading’, careful adjustment of the condenser and background OPD, and especially by reduction of the condenser aperture.Scanning measurements of IOPD were shown experimentally and theoretically to be insensitive to changes in the measuring‐spot diameter or errors in focus. Valid measurements of dry mass can therefore be made even if the three‐dimensional specimen (e.g. a living cell or isolated nucleus) is considerably thicker than the depth of focus

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03975.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe construction of a microspectrofluorometer with automatic correction capabilities is given. The instrument uses a quantum counting system for correction of excitation spectra and an interpolating function generator for correction of emission spectra. An inexpensive analogue computer is an integral part of the electronic portion of the instrument and allows a number of mathematical manipulations to be performed on the sample and reference signals prior to recording or display. Under the conditions stated, the sensitivity of the instrument is in the 10−9M range for quinine sulphate irradiated at 365 nm. The linear response range for quinine sulphate is 10−3to 10−9M. The operational wavelength range of the machine is between 226 and 7

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03976.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe injection replication procedure has been modified for study of the thin and very delicate blood vessels of young embryos. Batson's corrosion compound (a polyester resin) modified for rapid polymerization (20:3.0:0.25, monomer: catalyst: promoter) was effective in replicating even very small blood vessels without excessive distension. Since injection of plastic induced violent heart spasms with eventual expulsion of plastic from the ventricular lumen, contractility of the heart was inhibited by injection of a 2% (w/v) aqueous solution of KNO3prior to injection with polyester resin. Following polymerization of the injected resin, the tissues were macerated and removed, leaving a solid three‐dimensional cast of the lumen of the circulatory system. The casts were photographed with the scanning electron microscope to produce accurate micrographs for study of the developmental anatomy of the circulatory syste

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03977.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryA study was made of ultraviolet polymerization of methacrylate, Vestopal and Epon embedding media. By placing thermocouples in the monomeric resin during UV irradiation, it was found that the temperature of the resins was 5–10°C above the ambient temperature recorded by mercury thermometers placed adjacent to the capsules. When the resins were maintained at room temperature (22–24°C), Epon could not be polymerized with UV irradiation, but methacrylate and Vestopal polymerized within 1–2 days. By using unilateral UV irradiation directed perpendicular to thin sheets of Vestopal‐infiltrated tissue specimens, the depth of polymerization in osmium‐blackened (fixed) tissues was determined to be 0

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03978.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryIn stereological work, component volume densities are estimated routinely by invoking the Delesse principle of areal analysis. This is true whether the morpho‐metric methods are based on the measurement of transectional areas, linear intercepts or point densities. Following our earlier consideration of the special case of a spherical component in a spherical containing volume, we here present a warning on the use of this fundamental principle. This report demonstrates that estimates of volume densities may be derived by application of two main formulations which are based on the areal analysis of ‘cubical’ and ‘spherical’ mathematical models. It is emphasized that these formulations of the Delesse relationship are not mathematically equivalent in all practical instances; failure to appreciate the correct practical circumstances in which each should be applied may lead therefore to the introduction of a statistical bias into the volume density data which are obtained. The conditions under which the formulations should be applied are stressed and clarified and some biological examples are provided. Whilst the problems are presented in a form which is aimed primarily at the biologist, they are also pertinent to the earth and materials scientists and to morphometrists i

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03979.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryA technique is described for the examination of frozen biological specimens on a modified stub, and a clamping device for examining freeze‐fractured specimen

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03980.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryAn apparatus to control the temperature of a specimen under observation in the light microscope is described. It consists of a Peltier element and its heat sink which are built into a standard rotating microscope stage. An electronic control unit regulates the temperature.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03981.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryA preliminary exploration has been made of the feasibility of using an electron microscope environmental chamber to study the earlier stages of water drop nucleation and condensation.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03982.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY