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Direct carbon replicas from metal surfaces
VACUUM Classified A b s t r a c t s
II
--
Vacuum
Apparatus
and Auxiliaries
--
II
Contd.
Abstract No. and References
in position j u s t a b o v e t h e focal p o i n t of t h e microscope. A f t e r b r i n g i n g t h e selected a r e a u n d e r a grid s q u a r e t h e microscope c o l u m n is lowered so t h a t t h e grid is pressed a g a i n s t t h e s p e c i m e n b y t h e pins. T h e grid is a n c h o r e d in t h i s position b y a few d r o p s of 1-2~o B e d a c r y l a n d t h e grid is t h e n s e p a r a t e d from t h e metal. A t h i n l a y e r of c a r b o n is n e x t deposited on t h e s t r u c t u r e surface of t h e F o r m v a r a n d t h e l a t t e r is dissolved a w a y in chloroform l e a v i n g t h e c a r b o n film still a t t a c h e d to t h e grid a n d r e a d y for e x a m i n a t i o n in t h e electron microscope. If t h e s p e c i m e n is to be s h a d o w e d t h i s m u s t be done t h r o u g h t h e grid bars a n d this limits t h e angle of s h a d o w i n g to 3:1. A m o r e c o m p l i c a t e d m e t h o d is also described w h i c h o v e r c o m e s this difficulty a n d also gives b e t t e r r e s u l t s w i t h h e a v i l y - e t c h e d steel surfaces.
Paper by D. E. Bradley Brit. J. Appl. Phys. 5, Dec. 1955 430-432
Direct Carbon Replicas from Metal Surfaces United Kingdom. T w o m e t h o d s h a v e been developed for t h e r e m o v a l of c a r b o n replica films directly e v a p o r a t e d on to e t c h e d m e t a l surfaces. T h e s e i n v o l v e either electropolishing or chemically e t c h i n g a f t e r deposition of t h e carbon. T h e film r e m o v e d b y electropolishing gives a replica of h i g h resolution, whilst w i t h t h e e t c h i n g t e c h n i q u e e x t r a c t i o n replicas m a y be p r e p a r e d f r o m m u l t i - p h a s e alloys a n d t h e e x t r a c t e d p h a s e s identified b y electron diffraction. Some e x a m p l e s of t h e application of t h e t e c h n i q u e s to c a r b o n a n d alloy steels are given. (Authors)
Article by E. Smith & J. Nutting Brit. J. Appt. Phys. 7, June 1956 214-217
Use of Carbon Replicas in the Electron Microscopy of Yeast Bud Scars United Kingdom. T h e a u t h o r h a s u s e d his t w o - s t a g e F o r m v a r - c a r b o n t e c h n i q u e to o b t a i n s h a d o w e d c a r b o n replicas of y e a s t b u d d i n g scars. U l t r a v i o l e t p h o t o l y t i c m e t h o d s h a d s h o w n t h e existence of b u d d i n g scars of circular outline, a n d it h a s been claimed t h a t two f o r m s of scar exist. T h i s h a s been confirmed b y t h e p r e s e n t work a n d t w o t y p e s of scar c a n be v e r y readily distinguished. T h e cells are w a s h e d , m o u n t e d on F o r m v a r films, a n d a t h i n l a y e r of c a r b o n is deposited b y v a c u u m evaporation. A f t e r dissolution of t h e F o r m v a r a n d yeast, t h e c a r b o n replica is s h a d o w e d . T h e r e s u l t s d e m o n s t r a t e t h e potentialities of c a r b o n replica t e c h n i q u e s in t h e e x a m i n a t i o n of surfaces of b a c t e r i a a n d o t h e r organisms, a n d m o r e detailed s t u d y of y e a s t b u d scars is in progress.
Electron Microscope Observations of Periodicities in the Surface Structure of Tobacco Mosaic Virus United Kingdom. T h e surface s t r u c t u r e of tobacco mosaic v i r u s h a s been i n v e s t i g a t e d in a n electron microscope a t m a g n i f i c a t i o n s of × 40,000 a n d × 80,000 u s i n g t h e c a r b o n replica t e c h n i q u e . E v i d e n c e w a s f o u n d for a l o n g i t u d i n a l s t r u c t u r e r u n n i n g t h e full l e n g t h of t h e v i r u s rod. Some rods also showed a 'herring-bone' s t r u c t u r e ; m e a s u r e m e n t s f r o m p r i n t s enlarged to × 400,000 gave a m e a n v a l u e of 46/~ for t h e axial r e p e a t - d i s t a n c e of t h i s s t r u c t u r e , w h i c h is a l m o s t e x a c t l y double t h a t of t h e p i t c h of t h e helical s t r u c t u r e p r e v i o u s l y d e d u c e d f r o m x - r a y data. I n t h e few rods w h i c h s h o w e d evidence of helical s t r u c t u r e , t h e angle of a d v a n c e w a s f o u n d to be b e t w e e n 80 ° a n d 85 ° , as c o m p a r e d w i t h t h e v a l u e of 82.5 ° required b y t h e m o d e l proposed b y F r a n k l i n . T h e w i d t h of t h e r o d s w a s f o u n d to be 1505=5/~. I t w a s also f o u n d t h a t t h e rods h a v e a n a n g u l a r a p p e a r a n c e in cross-section, s u g g e s t i n g a h e x a g o n a l f o r m w i t h a groove a t t h e corners.
Fine Structure of Tobacco Mosaic Virus United States. T h i s s t u d y w a s directed a t increasing t h e visibility of m a c r o m o l e c u l e s in t h e electron microscope, in p a r t i c u l a r b y e v a p o r a t i n g h e a v y m e t a l s a t angles (with respect to t h e substrate) close to 0% A s u i t a b l y prep a r e d s a m p l e of t h e U1 s t r a i n of tobacco mosaic v i r u s w a s s p r a y e d on to t h e collodion-covered c o n v e x face of a p l a n e - c o n v e x lens of 250 m m . r a d i u s of c u r v a t u r e . T h o r i u m w a s e v a p o r a t e d f r o m a t u n g s t e n f i l a m e n t to give grazing incidence n e a r t h e pole of t h e lens. T h e collodion w a s t h e n s t r i p p e d f r o m t h e glass a n d m o u n t e d on copper grids; t h i s t e c h n i q u e gave a r a n g e of angles of incidence of t h e t h o r i u m a t o m s . I t was f o u n d t h a t rods l y i n g parallel to t h e i n c i d e n t b e a m , a t angles of incidence n e a r 0 °, showed a periodic d e n s i t y v a r i a t i o n a l o n g t h e l o n g i t u d i n a l axis; t h e period of t h e s e f l u c t u a t i o n s a v e r a g e d 136/~. T h e i n d i v i d u a l striations are n o t p e r p e n d i c u l a r to t h e long axis, a n d t h e n e t effect is t h a t of a r i g h t - h a n d e d helix. F r o m t h e v a r i a t i o n in c o n t r a s t as a f u n c t i o n of s h a d o w i n g angle, it c a n be d e d u c e d t h a t t h e slope of t h e d i s c o n t i n u i t y responsible for t h e s t r i a t i o n s m u s t be no m o r e t h a n a few degrees a n d t h a t t h e h e i g h t of t h e d i s c o n t i n u i t y is of t h e order of 15-30 ,~. Similar r e s u l t s h a v e been o b t a i n e d for t h e U2 s t r a i n of virus.
A Study of the Formvar Replica Process United Kingdom. A detailed s t u d y h a s been m a d e of F o r m v a r replicas of v a r i o u s d e p t h s of s t r u c t u r e . P l a i n replicas, s h a d o w e d replicas a n d replicas s h a d o w e d on t h e b a c k surface were p r e p a r e d f r o m t h e s a m e area of a m e t a l surface. I n order to m e a s u r e t h e h e i g h t of s t r u c t u r e w h i c h m a y h a v e p e n e t r a t e d t h e replica, m e a s u r e m e n t s were m a d e w i t h a reflection i n t e r f e r o m e t e r microscope in a d d i t i o n to t h e n o r m a l electron microscope m i c r o g r a p h . Details of t h e i n t e r f e r o m e t e r microscope m e a s u r i n g t e c h n i q u e are given. T h e p a r t i c u l a r i n s t r u m e n t h a d a resglution slightly b e t t e r t h a n t h a t g i v e n b y a n o r d i n a r y 4 m m . objective. M o n o c h r o m a t i c i l l u m i n a t i o n of 5,780 A w a s u s e d i n d i c a t i n g a h e i g h t difference of 1,930/k on t h e s p e c i m e n in a d i s p l a c e m e n t of t h e fringe s y s t e m b y one fringe width. I n view of t h e resolution of t h i s i n s t r u m e n t t h e s p e c i m e n s t r u c t u r e h a d to be c o m p a r a t i v e l y coarse. F o u r s p e c i m e n s of pearlitic steel were u s e d a n d prepared b y m e c h a n i c a l polishing a n d acid e t c h i n g alternately, u n t i l t h e flowed l a y e r w a s r e m o v e d , a n d were t h e n given final etches of 20, 10, 5 a n d 2 s respectively in 1 ~o nital. T h i s t r e a t m e n t resulted in h e a v y , normal, light a n d invisible e t c h e s respectively,
October, 1956
Vacuum Vol. VI
61]II
62/II
Letter by D. E. Bradley Research 8, Dec. 1955 $62-$63
63/II
Letter by R. E. F. Matthews, R. W. H o m e & E. M. Green Nature x78 , 22.9.1956 635-636
64/II
Letter by R. F. Baker Nature z78 , 22.9.1956 636-637
65/II
247
II
--
Vacuum
Apparatus
and Auxiliaries
--
II
Contd.
Abstract No. and References
in position j u s t a b o v e t h e focal p o i n t of t h e microscope. A f t e r b r i n g i n g t h e selected a r e a u n d e r a grid s q u a r e t h e microscope c o l u m n is lowered so t h a t t h e grid is pressed a g a i n s t t h e s p e c i m e n b y t h e pins. T h e grid is a n c h o r e d in t h i s position b y a few d r o p s of 1-2~o B e d a c r y l a n d t h e grid is t h e n s e p a r a t e d from t h e metal. A t h i n l a y e r of c a r b o n is n e x t deposited on t h e s t r u c t u r e surface of t h e F o r m v a r a n d t h e l a t t e r is dissolved a w a y in chloroform l e a v i n g t h e c a r b o n film still a t t a c h e d to t h e grid a n d r e a d y for e x a m i n a t i o n in t h e electron microscope. If t h e s p e c i m e n is to be s h a d o w e d t h i s m u s t be done t h r o u g h t h e grid bars a n d this limits t h e angle of s h a d o w i n g to 3:1. A m o r e c o m p l i c a t e d m e t h o d is also described w h i c h o v e r c o m e s this difficulty a n d also gives b e t t e r r e s u l t s w i t h h e a v i l y - e t c h e d steel surfaces.
Paper by D. E. Bradley Brit. J. Appl. Phys. 5, Dec. 1955 430-432
Direct Carbon Replicas from Metal Surfaces United Kingdom. T w o m e t h o d s h a v e been developed for t h e r e m o v a l of c a r b o n replica films directly e v a p o r a t e d on to e t c h e d m e t a l surfaces. T h e s e i n v o l v e either electropolishing or chemically e t c h i n g a f t e r deposition of t h e carbon. T h e film r e m o v e d b y electropolishing gives a replica of h i g h resolution, whilst w i t h t h e e t c h i n g t e c h n i q u e e x t r a c t i o n replicas m a y be p r e p a r e d f r o m m u l t i - p h a s e alloys a n d t h e e x t r a c t e d p h a s e s identified b y electron diffraction. Some e x a m p l e s of t h e application of t h e t e c h n i q u e s to c a r b o n a n d alloy steels are given. (Authors)
Article by E. Smith & J. Nutting Brit. J. Appt. Phys. 7, June 1956 214-217
Use of Carbon Replicas in the Electron Microscopy of Yeast Bud Scars United Kingdom. T h e a u t h o r h a s u s e d his t w o - s t a g e F o r m v a r - c a r b o n t e c h n i q u e to o b t a i n s h a d o w e d c a r b o n replicas of y e a s t b u d d i n g scars. U l t r a v i o l e t p h o t o l y t i c m e t h o d s h a d s h o w n t h e existence of b u d d i n g scars of circular outline, a n d it h a s been claimed t h a t two f o r m s of scar exist. T h i s h a s been confirmed b y t h e p r e s e n t work a n d t w o t y p e s of scar c a n be v e r y readily distinguished. T h e cells are w a s h e d , m o u n t e d on F o r m v a r films, a n d a t h i n l a y e r of c a r b o n is deposited b y v a c u u m evaporation. A f t e r dissolution of t h e F o r m v a r a n d yeast, t h e c a r b o n replica is s h a d o w e d . T h e r e s u l t s d e m o n s t r a t e t h e potentialities of c a r b o n replica t e c h n i q u e s in t h e e x a m i n a t i o n of surfaces of b a c t e r i a a n d o t h e r organisms, a n d m o r e detailed s t u d y of y e a s t b u d scars is in progress.
Electron Microscope Observations of Periodicities in the Surface Structure of Tobacco Mosaic Virus United Kingdom. T h e surface s t r u c t u r e of tobacco mosaic v i r u s h a s been i n v e s t i g a t e d in a n electron microscope a t m a g n i f i c a t i o n s of × 40,000 a n d × 80,000 u s i n g t h e c a r b o n replica t e c h n i q u e . E v i d e n c e w a s f o u n d for a l o n g i t u d i n a l s t r u c t u r e r u n n i n g t h e full l e n g t h of t h e v i r u s rod. Some rods also showed a 'herring-bone' s t r u c t u r e ; m e a s u r e m e n t s f r o m p r i n t s enlarged to × 400,000 gave a m e a n v a l u e of 46/~ for t h e axial r e p e a t - d i s t a n c e of t h i s s t r u c t u r e , w h i c h is a l m o s t e x a c t l y double t h a t of t h e p i t c h of t h e helical s t r u c t u r e p r e v i o u s l y d e d u c e d f r o m x - r a y data. I n t h e few rods w h i c h s h o w e d evidence of helical s t r u c t u r e , t h e angle of a d v a n c e w a s f o u n d to be b e t w e e n 80 ° a n d 85 ° , as c o m p a r e d w i t h t h e v a l u e of 82.5 ° required b y t h e m o d e l proposed b y F r a n k l i n . T h e w i d t h of t h e r o d s w a s f o u n d to be 1505=5/~. I t w a s also f o u n d t h a t t h e rods h a v e a n a n g u l a r a p p e a r a n c e in cross-section, s u g g e s t i n g a h e x a g o n a l f o r m w i t h a groove a t t h e corners.
Fine Structure of Tobacco Mosaic Virus United States. T h i s s t u d y w a s directed a t increasing t h e visibility of m a c r o m o l e c u l e s in t h e electron microscope, in p a r t i c u l a r b y e v a p o r a t i n g h e a v y m e t a l s a t angles (with respect to t h e substrate) close to 0% A s u i t a b l y prep a r e d s a m p l e of t h e U1 s t r a i n of tobacco mosaic v i r u s w a s s p r a y e d on to t h e collodion-covered c o n v e x face of a p l a n e - c o n v e x lens of 250 m m . r a d i u s of c u r v a t u r e . T h o r i u m w a s e v a p o r a t e d f r o m a t u n g s t e n f i l a m e n t to give grazing incidence n e a r t h e pole of t h e lens. T h e collodion w a s t h e n s t r i p p e d f r o m t h e glass a n d m o u n t e d on copper grids; t h i s t e c h n i q u e gave a r a n g e of angles of incidence of t h e t h o r i u m a t o m s . I t was f o u n d t h a t rods l y i n g parallel to t h e i n c i d e n t b e a m , a t angles of incidence n e a r 0 °, showed a periodic d e n s i t y v a r i a t i o n a l o n g t h e l o n g i t u d i n a l axis; t h e period of t h e s e f l u c t u a t i o n s a v e r a g e d 136/~. T h e i n d i v i d u a l striations are n o t p e r p e n d i c u l a r to t h e long axis, a n d t h e n e t effect is t h a t of a r i g h t - h a n d e d helix. F r o m t h e v a r i a t i o n in c o n t r a s t as a f u n c t i o n of s h a d o w i n g angle, it c a n be d e d u c e d t h a t t h e slope of t h e d i s c o n t i n u i t y responsible for t h e s t r i a t i o n s m u s t be no m o r e t h a n a few degrees a n d t h a t t h e h e i g h t of t h e d i s c o n t i n u i t y is of t h e order of 15-30 ,~. Similar r e s u l t s h a v e been o b t a i n e d for t h e U2 s t r a i n of virus.
A Study of the Formvar Replica Process United Kingdom. A detailed s t u d y h a s been m a d e of F o r m v a r replicas of v a r i o u s d e p t h s of s t r u c t u r e . P l a i n replicas, s h a d o w e d replicas a n d replicas s h a d o w e d on t h e b a c k surface were p r e p a r e d f r o m t h e s a m e area of a m e t a l surface. I n order to m e a s u r e t h e h e i g h t of s t r u c t u r e w h i c h m a y h a v e p e n e t r a t e d t h e replica, m e a s u r e m e n t s were m a d e w i t h a reflection i n t e r f e r o m e t e r microscope in a d d i t i o n to t h e n o r m a l electron microscope m i c r o g r a p h . Details of t h e i n t e r f e r o m e t e r microscope m e a s u r i n g t e c h n i q u e are given. T h e p a r t i c u l a r i n s t r u m e n t h a d a resglution slightly b e t t e r t h a n t h a t g i v e n b y a n o r d i n a r y 4 m m . objective. M o n o c h r o m a t i c i l l u m i n a t i o n of 5,780 A w a s u s e d i n d i c a t i n g a h e i g h t difference of 1,930/k on t h e s p e c i m e n in a d i s p l a c e m e n t of t h e fringe s y s t e m b y one fringe width. I n view of t h e resolution of t h i s i n s t r u m e n t t h e s p e c i m e n s t r u c t u r e h a d to be c o m p a r a t i v e l y coarse. F o u r s p e c i m e n s of pearlitic steel were u s e d a n d prepared b y m e c h a n i c a l polishing a n d acid e t c h i n g alternately, u n t i l t h e flowed l a y e r w a s r e m o v e d , a n d were t h e n given final etches of 20, 10, 5 a n d 2 s respectively in 1 ~o nital. T h i s t r e a t m e n t resulted in h e a v y , normal, light a n d invisible e t c h e s respectively,
October, 1956
Vacuum Vol. VI
61]II
62/II
Letter by D. E. Bradley Research 8, Dec. 1955 $62-$63
63/II
Letter by R. E. F. Matthews, R. W. H o m e & E. M. Green Nature x78 , 22.9.1956 635-636
64/II
Letter by R. F. Baker Nature z78 , 22.9.1956 636-637
65/II
247