摘要:

SYNOPSIS.A phase‐contrast microscope is described in which the properties of polarized light are employed in order to vary the relative amplitudes and phases of the direct and diffracted beams over a wide range. The two beams, which are plane polarized, have their vibration directions rendered orthogonal by passage through a quartz phase plate. Phase differences are introduced by means of a Soleil‐type compensator and a rotating analyser enables the relative amplitudes to be control

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04430.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SYNOPSIS.A special Cooke microscope was used to examine the principles of phase‐contrast applied to a series of simple objects. With transparent objects the image contrast with different methods depends on the phase change introduced by the object. Simple absorption of the direct light without phase change increases contrast of both phase and absorbing objects at first, but eventually produces central dark‐ground illumination. With objects of widely differing phase change optimum phase‐contrast is obtained with a quarter‐Nave phase‐plate. The exact degree of phase change required is not critical. Absorption of the direct light increases the sensitivity and it is suggested that 100 P.c., 20 p.c., and 6 p.c. transmission objectives would suit most requirements. Absorption of diffracted light is useful with objects of high phase change, but as these are already easy to see the scope of this method is limited. Phase‐contrast is maximal at the border of the image of a large object, but it extends further into the image than is generally realized. As a means of immersion refractometry phasecontrast is more sensitive than the microscopical methods commonly employed. Precautions to be observed in the use of the star test and Abbe test plate ar

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04431.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SYNOPSIS.A common group of optical artefacts is described in which regions of phase or amplitude change in the object appear in sharp outline in the image, where they may be misinterpreted and regarded as evidence of the presence of actual membranes. It is shown that these appearances are always encountered with dark‐ground illumination, of both types, oblique and central, provided the object is large enough to be resolved. Similar effects can also be obtained with bright‐ground illumination and various phase‐contrast methods.With phase‐retarding objects in positive phase‐contrast, the appearance of a black outline to image detail is seen when reversal of contrast occurs. This is seen when the object produces higher phase change than the optimum for the particular system. This optimum depends on the ratio of direct to diffracted light: the less direct light is transmitted, the lower is the optimum range of phase change in t

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04432.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SYNOPSIS.The precautions necessary in the use of immersion objectives are often not sufficiently observed. Immersion oils must be chosen for the particular make of objective used; if this is not done it is shown that considerable changes of tube length can take place.

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04433.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SYNOPSIS.New Foraminifera from the Lower Gault of Southern England are described. The new species areHormosina folkestonienais, Ammosphwoidina minuta, Nodosaria fontannesivar.flexocarinata, tristix gaultina, Vaginulina mariei, V. pseudodiscors, Ramulina fusiformis, Virgulina viscidus, Bolivina subcretacea, Valvulineria oveyi, V. parva, Ceratobulimina woodi. Certain new varieties are also described.

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04434.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SYNOPSIS.The use of a suitably chosen auxiliary glass lens for focusing a quartz monochromat objective in visible light is described. Focusing is performed with this lens above the objective and on removal the objective is then in focus for one ultraviolet wavelength. The method has been applied to the ultraviolet photomicrography of living tissue culture cells which requires rapid focusing without previous ultraviolet irradiation of the specimen.

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04435.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SYNOPSIS.By exploiting the property of polarization, the intensity of the light directly entering an objective can be controlled, so that the illumination of the specimen may be adjusted between critical bright and dark field conditions.The use of a suitable Polaroid substage stop in conjunction with an analyser is described, discussed, and also the conversion of an immersion paraboloid to this use. Bn&‐focal illuminating system of 0.86 N.A., suitable for this and a variety of other uses, is also describ

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04436.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SYNOPSIS.Polyvinyl alcohol has been successfully substituted for natural gums in water‐miscible mounting media of refractive index 1.38. Two gm. of polyvinyl alcohol is dispersed in 7 ml. of 70% acetone into which 5 ml. each of water, glycerine and lactic acid are then stirred. A further 5 ml. of water is added slowly and the whole is heated to transparency. The media dry rapidly to a hard pellicl

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04437.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04438.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1950.tb04439.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY