Michael Brady, Xiao-Bo Pan, Veit Schenk, Melissa Terras, Paul Robertson, and Nicholas Molton
- Published in print:
- 2005
- Published Online:
- January 2012
- ISBN:
- 9780197262962
- eISBN:
- 9780191734533
- Item type:
- chapter
- Publisher:
- British Academy
- DOI:
- 10.5871/bacad/9780197262962.003.0003
- Subject:
- Archaeology, Methodology and Techniques
It is agreed that stilus tablets are very important documentary sources, however they are the most difficult to decipher. The difficulties in deciphering them is due to the rough surface of the ...
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It is agreed that stilus tablets are very important documentary sources, however they are the most difficult to decipher. The difficulties in deciphering them is due to the rough surface of the tablets, the low brightness contrast of the incisions, the dense wood-grain lines, and the badly stained and pitted nature of the tablets. All of these posit a challenge for conventional two-dimensional (2D) image analysis. This chapter aims to provide a system that would aid the historian in interpreting stilus tablets by improving the legibility of the tablets. It provides novel ways of determining the texts incised on the tablets. One of these is the use of three-dimensional (3D) image analysis techniques. Such a technique is capable of detecting incisions, compared to the 2D image analysis, and is portable and inexpensive. Another method that can be used is the use of shadow stereo. This method employs low raking angle light close to the plane of the tablet at different elevations. The chapter also discusses the image formation process and the process of choosing elevations for each azimuth direction. The chapter also includes a discussion on realizing the shadow stereo algorithm.Less
It is agreed that stilus tablets are very important documentary sources, however they are the most difficult to decipher. The difficulties in deciphering them is due to the rough surface of the tablets, the low brightness contrast of the incisions, the dense wood-grain lines, and the badly stained and pitted nature of the tablets. All of these posit a challenge for conventional two-dimensional (2D) image analysis. This chapter aims to provide a system that would aid the historian in interpreting stilus tablets by improving the legibility of the tablets. It provides novel ways of determining the texts incised on the tablets. One of these is the use of three-dimensional (3D) image analysis techniques. Such a technique is capable of detecting incisions, compared to the 2D image analysis, and is portable and inexpensive. Another method that can be used is the use of shadow stereo. This method employs low raking angle light close to the plane of the tablet at different elevations. The chapter also discusses the image formation process and the process of choosing elevations for each azimuth direction. The chapter also includes a discussion on realizing the shadow stereo algorithm.
Ian P. Howard
- Published in print:
- 2012
- Published Online:
- May 2012
- ISBN:
- 9780199764143
- eISBN:
- 9780199949359
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199764143.003.0261
- Subject:
- Psychology, Vision, Cognitive Psychology
The quality of the retinal image depends on optical factors such as chromatic and spherical aberrations and on the spacing of the receptors. An account of these factors is followed by a description ...
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The quality of the retinal image depends on optical factors such as chromatic and spherical aberrations and on the spacing of the receptors. An account of these factors is followed by a description of mechanisms responsible for the accommodation of the lens. First, the machinery of accommodation and the three types of accommodation are described. These are tonic accommodation, proximal accommodation, and accommodation induced by image blur. Induction of accommodation by image blur depends on blur detection and detection of the attributes of blur that indicate the required direction of accommodation. The chapter ends with a discussion of anisometropia and aniseikonia.Less
The quality of the retinal image depends on optical factors such as chromatic and spherical aberrations and on the spacing of the receptors. An account of these factors is followed by a description of mechanisms responsible for the accommodation of the lens. First, the machinery of accommodation and the three types of accommodation are described. These are tonic accommodation, proximal accommodation, and accommodation induced by image blur. Induction of accommodation by image blur depends on blur detection and detection of the attributes of blur that indicate the required direction of accommodation. The chapter ends with a discussion of anisometropia and aniseikonia.
Michael F. Land and Dan-Eric Nilsson
- Published in print:
- 2012
- Published Online:
- December 2013
- ISBN:
- 9780199581139
- eISBN:
- 9780191774652
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199581139.001.0001
- Subject:
- Biology, Animal Biology
This book provides a comparative account of all the types of eye in the animal kingdom. It gives an outline of the structure and function of each kind of eye, with an emphasis on the nature of the ...
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This book provides a comparative account of all the types of eye in the animal kingdom. It gives an outline of the structure and function of each kind of eye, with an emphasis on the nature of the optical systems and the physical principles involved in image formation. The book also covers the evolution and taxonomic distribution of each type of eye, and their roles in the behaviour and ecology of the animals that possess them. In comparing the capabilities of eyes, it considers the factors that lead to good resolution of detail, and to the ability to function under a wide range of light conditions. The book also deals with movements of the eyes: how they sample the world in time as well as space.Less
This book provides a comparative account of all the types of eye in the animal kingdom. It gives an outline of the structure and function of each kind of eye, with an emphasis on the nature of the optical systems and the physical principles involved in image formation. The book also covers the evolution and taxonomic distribution of each type of eye, and their roles in the behaviour and ecology of the animals that possess them. In comparing the capabilities of eyes, it considers the factors that lead to good resolution of detail, and to the ability to function under a wide range of light conditions. The book also deals with movements of the eyes: how they sample the world in time as well as space.
Xiaodong Zou, Sven Hovmöller, and Peter Oleynikov
- Published in print:
- 2011
- Published Online:
- January 2012
- ISBN:
- 9780199580200
- eISBN:
- 9780191731211
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199580200.003.0006
- Subject:
- Physics, Crystallography
Phase contrast, the contrast transfer function (CTF), kinematical scattering and the weak-phase object approximation are central concepts for image formation. The physics is described in great detail ...
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Phase contrast, the contrast transfer function (CTF), kinematical scattering and the weak-phase object approximation are central concepts for image formation. The physics is described in great detail with one hundred formulas, leading up to the fundamental relation between electron wave phases and structure factor phases. Through-focus series are discussed as a means to collect all the information from a structure projection – some data may be lost in one HRTEM image because it falls on a node (= zero cross-over of the CTF) but this data can be obtained from another image taken at another defocus value. It is shown that singly and doubly scattered electron waves are transferred differently by the objective lens to the image. Thus, they can be separated in image processing, especially if a few images of different focus are combined.Less
Phase contrast, the contrast transfer function (CTF), kinematical scattering and the weak-phase object approximation are central concepts for image formation. The physics is described in great detail with one hundred formulas, leading up to the fundamental relation between electron wave phases and structure factor phases. Through-focus series are discussed as a means to collect all the information from a structure projection – some data may be lost in one HRTEM image because it falls on a node (= zero cross-over of the CTF) but this data can be obtained from another image taken at another defocus value. It is shown that singly and doubly scattered electron waves are transferred differently by the objective lens to the image. Thus, they can be separated in image processing, especially if a few images of different focus are combined.
Joachim Frank
- Published in print:
- 2006
- Published Online:
- April 2010
- ISBN:
- 9780195182187
- eISBN:
- 9780199893416
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195182187.001.0001
- Subject:
- Biology, Biochemistry / Molecular Biology
In this book, the mathematical principles and working methods of single-particle reconstruction are described; a method designed to retrieve three-dimensional structural information from electron ...
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In this book, the mathematical principles and working methods of single-particle reconstruction are described; a method designed to retrieve three-dimensional structural information from electron micrographs showing thousands of “copies” of biological molecules trapped in a thin layer of ice. This technique is uniquely suited to obtain three-dimensional images of molecular machines in different functional states, as it dispenses with the need for crystals. The book starts with an introduction of image formation in the electron microscope, which includes the definition of the contrast transfer function. Next, averaging techniques and tools for image alignment, multivariate data analysis, and classification are described. An introduction into the mathematical principles underlying reconstruction of an object from its projections is followed by detailed accounts on how projection angles are determined, and how reconstruction is done in practice. The book concludes with a chapter on interpretation of density maps reconstructed, including methods for segmentation as well as fitting and docking of atomic coordinates.Less
In this book, the mathematical principles and working methods of single-particle reconstruction are described; a method designed to retrieve three-dimensional structural information from electron micrographs showing thousands of “copies” of biological molecules trapped in a thin layer of ice. This technique is uniquely suited to obtain three-dimensional images of molecular machines in different functional states, as it dispenses with the need for crystals. The book starts with an introduction of image formation in the electron microscope, which includes the definition of the contrast transfer function. Next, averaging techniques and tools for image alignment, multivariate data analysis, and classification are described. An introduction into the mathematical principles underlying reconstruction of an object from its projections is followed by detailed accounts on how projection angles are determined, and how reconstruction is done in practice. The book concludes with a chapter on interpretation of density maps reconstructed, including methods for segmentation as well as fitting and docking of atomic coordinates.
Xiaodong Zou, Sven Hovmöller, and Peter Oleynikov
- Published in print:
- 2011
- Published Online:
- January 2012
- ISBN:
- 9780199580200
- eISBN:
- 9780191731211
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199580200.003.0004
- Subject:
- Physics, Crystallography
Fundamental transmission electron microscopy covers the topics of resolution, electron optics, image recording systems and image distortions and how they can be handled by hardware (Cs-correctors) ...
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Fundamental transmission electron microscopy covers the topics of resolution, electron optics, image recording systems and image distortions and how they can be handled by hardware (Cs-correctors) and software. The interaction of electrons with matter starts with the individual atom and the atomic scattering factor. Special emphasis is placed on elastically scattered electrons, since those are the ones used for forming images of the atomic structure. The use of inelastically scattered electrons is briefly mentioned, for example in HAADF – high-angle annular dark field imaging of atomic structure.Less
Fundamental transmission electron microscopy covers the topics of resolution, electron optics, image recording systems and image distortions and how they can be handled by hardware (Cs-correctors) and software. The interaction of electrons with matter starts with the individual atom and the atomic scattering factor. Special emphasis is placed on elastically scattered electrons, since those are the ones used for forming images of the atomic structure. The use of inelastically scattered electrons is briefly mentioned, for example in HAADF – high-angle annular dark field imaging of atomic structure.
Tadaaki Tani
- Published in print:
- 2015
- Published Online:
- September 2015
- ISBN:
- 9780198714606
- eISBN:
- 9780191782862
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198714606.003.0003
- Subject:
- Physics, Condensed Matter Physics / Materials
The preparation of metal nanoparticles for plasmonics according to the LaMer Diagram is described, and this knowledge is extended to single-crystalline nanoparticles with variations in crystal habit, ...
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The preparation of metal nanoparticles for plasmonics according to the LaMer Diagram is described, and this knowledge is extended to single-crystalline nanoparticles with variations in crystal habit, nanorods, and nanoplates. This is reinforced by knowledge of the preparation of photographic Ag and AgX nanoparticles. Formation mechanisms of reduction sensitization and latent image centres (Ag2 and Agn with n≥4) serve as nuclei for Ag nanoparticles. Photographic development provides knowledge of the growth of small Agn clusters in the presence of silver ions and reducing agents. Descriptions of the growth of AgX nanoparticles include protective colloids and apparatus for this. Mechanisms for preparing all the possible single-crystalline nanoparticles with fcc structure, tabular nanoparticles, core/shell, and epitaxial nanoparticles with different AgXs, together with methods of preparing nanoparticles with monodispersity and enhanced anisotropy in shape and arranging them, are also discussed.Less
The preparation of metal nanoparticles for plasmonics according to the LaMer Diagram is described, and this knowledge is extended to single-crystalline nanoparticles with variations in crystal habit, nanorods, and nanoplates. This is reinforced by knowledge of the preparation of photographic Ag and AgX nanoparticles. Formation mechanisms of reduction sensitization and latent image centres (Ag2 and Agn with n≥4) serve as nuclei for Ag nanoparticles. Photographic development provides knowledge of the growth of small Agn clusters in the presence of silver ions and reducing agents. Descriptions of the growth of AgX nanoparticles include protective colloids and apparatus for this. Mechanisms for preparing all the possible single-crystalline nanoparticles with fcc structure, tabular nanoparticles, core/shell, and epitaxial nanoparticles with different AgXs, together with methods of preparing nanoparticles with monodispersity and enhanced anisotropy in shape and arranging them, are also discussed.
Gordon M. Shepherd
- Published in print:
- 2013
- Published Online:
- November 2015
- ISBN:
- 9780231159111
- eISBN:
- 9780231530316
- Item type:
- chapter
- Publisher:
- Columbia University Press
- DOI:
- 10.7312/columbia/9780231159111.003.0007
- Subject:
- Neuroscience, Sensory and Motor Systems
This chapter examines how the brain represents our sensory world in order to serve as the basis for perception. It is hypothesized that by studying the neural mechanisms for setting up and processing ...
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This chapter examines how the brain represents our sensory world in order to serve as the basis for perception. It is hypothesized that by studying the neural mechanisms for setting up and processing a visual scene in the brain, we will learn principles that will apply to the neural mechanisms for setting up and processing a smell image in the brain. Confirming this hypothesis offers a new perspective on how smells are represented in our brains and how these representations contribute to the perception of flavor. The chapter discusses the following principles: the initial image representation in a two-dimensional sheet, lateral inhibition, contrast enhancement, temporal transients, center-surround inhibition, and feature extraction—all of which play essential roles in the formation of neural images in all sensory systems.Less
This chapter examines how the brain represents our sensory world in order to serve as the basis for perception. It is hypothesized that by studying the neural mechanisms for setting up and processing a visual scene in the brain, we will learn principles that will apply to the neural mechanisms for setting up and processing a smell image in the brain. Confirming this hypothesis offers a new perspective on how smells are represented in our brains and how these representations contribute to the perception of flavor. The chapter discusses the following principles: the initial image representation in a two-dimensional sheet, lateral inhibition, contrast enhancement, temporal transients, center-surround inhibition, and feature extraction—all of which play essential roles in the formation of neural images in all sensory systems.
Jill Lancaster and Barbara J. Downes
- Published in print:
- 2013
- Published Online:
- December 2013
- ISBN:
- 9780199573219
- eISBN:
- 9780191774850
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199573219.003.0006
- Subject:
- Biology, Aquatic Biology, Animal Biology
This chapter provides an overview of the structure and function of insect photoreceptors, highlighting some problems (and solutions) peculiar to aquatic insect taxa. The physical properties of light ...
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This chapter provides an overview of the structure and function of insect photoreceptors, highlighting some problems (and solutions) peculiar to aquatic insect taxa. The physical properties of light underwater are described and their potential restrictions considered throughout the subsequent discussions of visual function. First is a discussion of the basic structure and the different types of compound eye, and the basic optical units, the ommatidia. The structure of compound eyes influences how they function, including image formation, movement detection, resolution, sensitivity to light levels, and wavelength (e.g., colour vision and polarization sensitivity). The following sections consider the other eye types, ocelli and stemmata, which are less complex than compound eyes, but still provide important kinds of photosensory information to aquatic insects. The final section provides a brief discussion of bioluminescence, which a few aquatic insects use in communication.Less
This chapter provides an overview of the structure and function of insect photoreceptors, highlighting some problems (and solutions) peculiar to aquatic insect taxa. The physical properties of light underwater are described and their potential restrictions considered throughout the subsequent discussions of visual function. First is a discussion of the basic structure and the different types of compound eye, and the basic optical units, the ommatidia. The structure of compound eyes influences how they function, including image formation, movement detection, resolution, sensitivity to light levels, and wavelength (e.g., colour vision and polarization sensitivity). The following sections consider the other eye types, ocelli and stemmata, which are less complex than compound eyes, but still provide important kinds of photosensory information to aquatic insects. The final section provides a brief discussion of bioluminescence, which a few aquatic insects use in communication.
Peter B. Moore
- Published in print:
- 2012
- Published Online:
- May 2015
- ISBN:
- 9780199767090
- eISBN:
- 9780190267841
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:osobl/9780199767090.003.0010
- Subject:
- Biology, Biochemistry / Molecular Biology
This chapter begins by identifying various kinds of imaging techniques. It then examines the role played by the amount of light and presence of fluorophore in the imaging process. the latter part of ...
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This chapter begins by identifying various kinds of imaging techniques. It then examines the role played by the amount of light and presence of fluorophore in the imaging process. the latter part of the chapter identifies the features of confocal microscopy and stimulated emission depletion (STED) microscopy. Sample problems are also provided at the end of the chapter.Less
This chapter begins by identifying various kinds of imaging techniques. It then examines the role played by the amount of light and presence of fluorophore in the imaging process. the latter part of the chapter identifies the features of confocal microscopy and stimulated emission depletion (STED) microscopy. Sample problems are also provided at the end of the chapter.
A. Sjöströtm, M. Abrahamssom, E. Byhr, and j. Sjöstrand
- Published in print:
- 1996
- Published Online:
- March 2012
- ISBN:
- 9780198523161
- eISBN:
- 9780191724558
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198523161.003.0026
- Subject:
- Neuroscience, Sensory and Motor Systems
Visual−deprivation experiments on cats and monkeys have showed that complete unilateral eye occlusion of these animals until twelve weeks of age can produce a permanent amblyopia and a decrease in ...
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Visual−deprivation experiments on cats and monkeys have showed that complete unilateral eye occlusion of these animals until twelve weeks of age can produce a permanent amblyopia and a decrease in cell density along the geniculocortical pathway. Reversal of the amblyopia was possible if the occlusion was removed before eight weeks of age in monkeys. Although this critical age is established for animals, the exact critical period has not been determined for humans, partly because of the problem with assessment of infant vision. This chapter focuses on the relationship between visual development and age at surgery for patients with total congenital cataract. In patients with total congenital cataract, retinal image formation is severely degraded from birth until the lens is removed by surgery and the optics is restored by a contact lens.Less
Visual−deprivation experiments on cats and monkeys have showed that complete unilateral eye occlusion of these animals until twelve weeks of age can produce a permanent amblyopia and a decrease in cell density along the geniculocortical pathway. Reversal of the amblyopia was possible if the occlusion was removed before eight weeks of age in monkeys. Although this critical age is established for animals, the exact critical period has not been determined for humans, partly because of the problem with assessment of infant vision. This chapter focuses on the relationship between visual development and age at surgery for patients with total congenital cataract. In patients with total congenital cataract, retinal image formation is severely degraded from birth until the lens is removed by surgery and the optics is restored by a contact lens.
Walter D. Ward
- Published in print:
- 2014
- Published Online:
- May 2015
- ISBN:
- 9780520283770
- eISBN:
- 9780520959521
- Item type:
- book
- Publisher:
- University of California Press
- DOI:
- 10.1525/california/9780520283770.001.0001
- Subject:
- Classical Studies, Asian and Middle Eastern History: BCE to 500CE
The Mirage of the Saracen analyzes the growth of monasticism and Christian settlements in the Sinai Peninsula through the early seventh century CE. It uses a post-colonial lens to examine the ways ...
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The Mirage of the Saracen analyzes the growth of monasticism and Christian settlements in the Sinai Peninsula through the early seventh century CE. It uses a post-colonial lens to examine the ways that Christian monks justified occupying the Sinai through creating associations between Biblical narratives and Sinai sites and assigning uncivilized, negative, and oppositional traits to the indigenous nomadic population, whom the Christians pejoratively called “Saracens.” By writing edifying tales of hostile nomads and the ensuing martyrdom of the monks, not only did the Christians reinforce their claims to the spiritual benefits of asceticism, they also provoked the Roman authorities to enhance the defense of pilgrimage routes to the Sinai. Included in these defenses was the monastery now known as Saint Catherine’s. When Muslim armies later began conquering the Middle East, Christians also labelled these new conquerors as Saracens, connecting Muslims to these pre-Islamic representations. The main sources used in this work are the Sinai Martyr Narratives – Ammonius’s Relatio and Pseudo-Nilus’s Narrationes, though many other literary sources as well as archaeological and anthropological information is used extensively.Less
The Mirage of the Saracen analyzes the growth of monasticism and Christian settlements in the Sinai Peninsula through the early seventh century CE. It uses a post-colonial lens to examine the ways that Christian monks justified occupying the Sinai through creating associations between Biblical narratives and Sinai sites and assigning uncivilized, negative, and oppositional traits to the indigenous nomadic population, whom the Christians pejoratively called “Saracens.” By writing edifying tales of hostile nomads and the ensuing martyrdom of the monks, not only did the Christians reinforce their claims to the spiritual benefits of asceticism, they also provoked the Roman authorities to enhance the defense of pilgrimage routes to the Sinai. Included in these defenses was the monastery now known as Saint Catherine’s. When Muslim armies later began conquering the Middle East, Christians also labelled these new conquerors as Saracens, connecting Muslims to these pre-Islamic representations. The main sources used in this work are the Sinai Martyr Narratives – Ammonius’s Relatio and Pseudo-Nilus’s Narrationes, though many other literary sources as well as archaeological and anthropological information is used extensively.
Christopher Hammond
- Published in print:
- 2015
- Published Online:
- August 2015
- ISBN:
- 9780198738671
- eISBN:
- 9780191801938
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198738671.003.0011
- Subject:
- Physics, Crystallography, Condensed Matter Physics / Materials
This chapter starts by looking at wave-particle character of electrons. It also explains the Ewald reflecting sphere construction for electron diffraction and provides an analysis of electron ...
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This chapter starts by looking at wave-particle character of electrons. It also explains the Ewald reflecting sphere construction for electron diffraction and provides an analysis of electron diffraction patterns. It also illustrates the precession and rotation electron diffraction techniques, Shechtman's identification of quasiperiodic crystals, Kikuchi patterns in the electron microscope and electron backscattered (EBSD) patterns in the scanning electron microscope, and image formation and resolution in the electron microscope.Less
This chapter starts by looking at wave-particle character of electrons. It also explains the Ewald reflecting sphere construction for electron diffraction and provides an analysis of electron diffraction patterns. It also illustrates the precession and rotation electron diffraction techniques, Shechtman's identification of quasiperiodic crystals, Kikuchi patterns in the electron microscope and electron backscattered (EBSD) patterns in the scanning electron microscope, and image formation and resolution in the electron microscope.
Olivier Hekster
- Published in print:
- 2015
- Published Online:
- August 2015
- ISBN:
- 9780198736820
- eISBN:
- 9780191800429
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198736820.003.0003
- Subject:
- Classical Studies, Archaeology: Classical
This chapter takes central coin types as its starting point, and compares the trajectory of representations of imperial (grand) mothers on central coin types with those on other types of evidence in ...
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This chapter takes central coin types as its starting point, and compares the trajectory of representations of imperial (grand) mothers on central coin types with those on other types of evidence in selected cases, focusing expecially on the Julio-Claudian and Severan dynasties. It questions assumptions about the level of interaction between the different media, which differs from one reign to the next. Developments in the representation of (imperial) women in various sources, in certain regions of the Empire, and in the Empire as a whole form the wider discourses within which imperial image formation is placed. The chapter also traces the parallels between increasing visibility of imperial mothers and grandmothers in centralized media—especially in the Eastern parts of the Empire—and a similar process in local civic representations. Where central notions cohered with these local expectations, a ‘shared field of experience’ made reciprocal interaction possible.Less
This chapter takes central coin types as its starting point, and compares the trajectory of representations of imperial (grand) mothers on central coin types with those on other types of evidence in selected cases, focusing expecially on the Julio-Claudian and Severan dynasties. It questions assumptions about the level of interaction between the different media, which differs from one reign to the next. Developments in the representation of (imperial) women in various sources, in certain regions of the Empire, and in the Empire as a whole form the wider discourses within which imperial image formation is placed. The chapter also traces the parallels between increasing visibility of imperial mothers and grandmothers in centralized media—especially in the Eastern parts of the Empire—and a similar process in local civic representations. Where central notions cohered with these local expectations, a ‘shared field of experience’ made reciprocal interaction possible.
