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Vacuum requirements of the β-ray spectrometer
Vacuum,
Vet. I V
April, 1954
No. 2
]References i NAIDOO~ D. and PRATT~ O. E.~ J. Neurol. Neurosurg. Psychiat.~ I4, 1951, 287. ' The Localisation of Some Acid Phosphatases in Brain Tissue.' * NAIDOO~D. and PRATT, O. E.s Enzymolegia, I7, I954, I. ' T h e Validity of Histochemical Observation Post-Mortem on Phosphatases in Brain Tissue '. a PRATT, O. E., Biochem. J., 55, 1953, 14o. ' T h e Proportion of Phosphatase Activity Demonstrable in Brain by Histological Techniques '.
Vacuum Requirements of the fl-Ray Spectrometer Sommaire Fig. 5. Showing acid phosphatase sites in a cerebral astrocytoma.
cortex and Fig. 5 shows acid phosphatase sites in a cerebral astrocytoma. The rate of freezing of the tissue appears to be rapid enough to avoid any ice crystal artefact detectable with the high power magnification of the ordinary microscope but at lower freezing temperatures mechanical distortion and fissuring of the tissue are troublesome. The working pressure is between 2 and 0.02 mm. Hg. It is important that slices should be of uniform thickness and that cooling should be continued until all free water is removed. A detailed account of the course of drying will be presented later. A number of slices of brain tissue large enough for histological work can be dried separately and independently. It is quite easy to renew the phosphorus pentoxide in the trap during the run after dosing all six isolation valves. Enzyme activity in the sections has been found to be of the same order as that in fresh tissue, for five of six enzymes investigated. 3 As histochemical techniques are developed, freeze drying seems likely to provide an important means of studying the histological localisation of those enzymes in tissues which survive drying and treatment with non-polar solvents. D. NAIDOO. O.
E.
PRATT.
Department of Neuropathology, Institute of Psychiatry, Maudsley Hospital, University of London, Denmark Hill, London, S.E.5. 15th January 1956.
197
ON DISCUTELES probl6mes de technique du vide qu'entra~nent la construction et la manipulation de spectrom~tres/~ rayons--~. Dans ce cas particulier, la chambre ~ vide de l'appareil est faite en aluminium, et des vannes ' ~ tiroir ' sent pr6vues pour isoler respectivement la source et le compteur. THE STUDYOF the spectral distribution of the fi-rays emitted by radioactive substances, is of great interest. Actually, the hypothesis of neutrino facilitates an explanation of the non-monochromaticity of the fi-emission and permits the formulation of a law for the distribution of the emitted electrons as a function of their energy. However, the experimental results often differ from the theoretical answers. Normally, in order to obtain the r-spectrum of a radio-active element, a spectrometer is used. The part played by the vacuum technique in thc operation of an apparatus of this kind is very important as can be seen from the following remarks. The apparatus discussed here is a r-spectrometer fitted with a thin magnetic lens. It works in conjunction with a scintillation counter. Essentially, it consists of a source emitting r-rays in all directions; an annular diaphragm placed between the source and the lens permits the passage of only those electrons which are emitted within a given angle. After having passed the diaphragm, a further selection takes place. All electrons of a certain fixed energy value are forced to converge on a point of the a x i s where the counter is installed. This effect depends on the strength of the magnetic field constituting the lens. By changing the strength of the field, i.e. by altering the current through the lens, all electrons of another energy level can be forced to .
Vet. I V
April, 1954
No. 2
]References i NAIDOO~ D. and PRATT~ O. E.~ J. Neurol. Neurosurg. Psychiat.~ I4, 1951, 287. ' The Localisation of Some Acid Phosphatases in Brain Tissue.' * NAIDOO~D. and PRATT, O. E.s Enzymolegia, I7, I954, I. ' T h e Validity of Histochemical Observation Post-Mortem on Phosphatases in Brain Tissue '. a PRATT, O. E., Biochem. J., 55, 1953, 14o. ' T h e Proportion of Phosphatase Activity Demonstrable in Brain by Histological Techniques '.
Vacuum Requirements of the fl-Ray Spectrometer Sommaire Fig. 5. Showing acid phosphatase sites in a cerebral astrocytoma.
cortex and Fig. 5 shows acid phosphatase sites in a cerebral astrocytoma. The rate of freezing of the tissue appears to be rapid enough to avoid any ice crystal artefact detectable with the high power magnification of the ordinary microscope but at lower freezing temperatures mechanical distortion and fissuring of the tissue are troublesome. The working pressure is between 2 and 0.02 mm. Hg. It is important that slices should be of uniform thickness and that cooling should be continued until all free water is removed. A detailed account of the course of drying will be presented later. A number of slices of brain tissue large enough for histological work can be dried separately and independently. It is quite easy to renew the phosphorus pentoxide in the trap during the run after dosing all six isolation valves. Enzyme activity in the sections has been found to be of the same order as that in fresh tissue, for five of six enzymes investigated. 3 As histochemical techniques are developed, freeze drying seems likely to provide an important means of studying the histological localisation of those enzymes in tissues which survive drying and treatment with non-polar solvents. D. NAIDOO. O.
E.
PRATT.
Department of Neuropathology, Institute of Psychiatry, Maudsley Hospital, University of London, Denmark Hill, London, S.E.5. 15th January 1956.
197
ON DISCUTELES probl6mes de technique du vide qu'entra~nent la construction et la manipulation de spectrom~tres/~ rayons--~. Dans ce cas particulier, la chambre ~ vide de l'appareil est faite en aluminium, et des vannes ' ~ tiroir ' sent pr6vues pour isoler respectivement la source et le compteur. THE STUDYOF the spectral distribution of the fi-rays emitted by radioactive substances, is of great interest. Actually, the hypothesis of neutrino facilitates an explanation of the non-monochromaticity of the fi-emission and permits the formulation of a law for the distribution of the emitted electrons as a function of their energy. However, the experimental results often differ from the theoretical answers. Normally, in order to obtain the r-spectrum of a radio-active element, a spectrometer is used. The part played by the vacuum technique in thc operation of an apparatus of this kind is very important as can be seen from the following remarks. The apparatus discussed here is a r-spectrometer fitted with a thin magnetic lens. It works in conjunction with a scintillation counter. Essentially, it consists of a source emitting r-rays in all directions; an annular diaphragm placed between the source and the lens permits the passage of only those electrons which are emitted within a given angle. After having passed the diaphragm, a further selection takes place. All electrons of a certain fixed energy value are forced to converge on a point of the a x i s where the counter is installed. This effect depends on the strength of the magnetic field constituting the lens. By changing the strength of the field, i.e. by altering the current through the lens, all electrons of another energy level can be forced to .