Nigel Daw
- Published in print:
- 2012
- Published Online:
- May 2012
- ISBN:
- 9780199751617
- eISBN:
- 9780199932375
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199751617.003.0001
- Subject:
- Psychology, Cognitive Neuroscience, Cognitive Psychology
The human visual system consists of a system for inspecting objects, starting with the fovea in the retina, and a system for noticing which objects should be inspected, and directing the eyes to look ...
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The human visual system consists of a system for inspecting objects, starting with the fovea in the retina, and a system for noticing which objects should be inspected, and directing the eyes to look at them. In daylight, the cones are the photoreceptors used, with three types, leading to trichromatic color vision. At night, the rods are active. As the eyes move, the world appears to be stationary, which is accomplished by noticing and carrying forward a limited number of objects from one snapshot to the next. Most aspects of vision are relative—the brightness, color, motion, and depth of an object are all seen relative to the background. Finally, absence of activity in the neurons of the visual system is interpreted as continuity with the rest of the scene, so that lesions in the brain may simply not be noticed.Less
The human visual system consists of a system for inspecting objects, starting with the fovea in the retina, and a system for noticing which objects should be inspected, and directing the eyes to look at them. In daylight, the cones are the photoreceptors used, with three types, leading to trichromatic color vision. At night, the rods are active. As the eyes move, the world appears to be stationary, which is accomplished by noticing and carrying forward a limited number of objects from one snapshot to the next. Most aspects of vision are relative—the brightness, color, motion, and depth of an object are all seen relative to the background. Finally, absence of activity in the neurons of the visual system is interpreted as continuity with the rest of the scene, so that lesions in the brain may simply not be noticed.
Stephen Mulhall
- Published in print:
- 2006
- Published Online:
- January 2007
- ISBN:
- 9780199208548
- eISBN:
- 9780191709067
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199208548.003.0005
- Subject:
- Philosophy, Philosophy of Language
This chapter examines the internal structure of the (interrupted) reflection on the status of the conclusions established in §246. Wittgenstein offers two pairs of propositions that he explicitly ...
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This chapter examines the internal structure of the (interrupted) reflection on the status of the conclusions established in §246. Wittgenstein offers two pairs of propositions that he explicitly claims (or implies) are comparable with each other: first, ‘Sensations are private’ and ‘One plays patience by oneself’, and then ‘Every rod has a length’ and ‘This body has extension’. Their comparability resides in their tendency to elicit the following kind of response from those to whom they are addressed: ‘I can't imagine the opposite’, or ‘What would it be like if it were otherwise?’ Wittgenstein suggests (call this the second level of his reflections) that this betrays an implicit awareness on the part of the respondents that these pairs of propositions are grammatical rather than empirical — by which he means that they do not represent a state of affairs that might have been otherwise, but would rather be advanced (to quote the preceding §247) ‘when one was explaining the meaning of the word [‘sensation’, or ‘patience’, or ‘rod’ or ‘body’] to him.Less
This chapter examines the internal structure of the (interrupted) reflection on the status of the conclusions established in §246. Wittgenstein offers two pairs of propositions that he explicitly claims (or implies) are comparable with each other: first, ‘Sensations are private’ and ‘One plays patience by oneself’, and then ‘Every rod has a length’ and ‘This body has extension’. Their comparability resides in their tendency to elicit the following kind of response from those to whom they are addressed: ‘I can't imagine the opposite’, or ‘What would it be like if it were otherwise?’ Wittgenstein suggests (call this the second level of his reflections) that this betrays an implicit awareness on the part of the respondents that these pairs of propositions are grammatical rather than empirical — by which he means that they do not represent a state of affairs that might have been otherwise, but would rather be advanced (to quote the preceding §247) ‘when one was explaining the meaning of the word [‘sensation’, or ‘patience’, or ‘rod’ or ‘body’] to him.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0016
- Subject:
- Physics, History of Physics
In 1983, K. James published two useful but rather complicated equations whose purpose was to help design the suspension spring. The equations show the effect that different spring lengths, widths, ...
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In 1983, K. James published two useful but rather complicated equations whose purpose was to help design the suspension spring. The equations show the effect that different spring lengths, widths, and thicknesses will have on the pendulum. The two equations are quite helpful, as the suspension spring is without doubt the most complicated part of a pendulum, despite its apparent physical simplicity. The first equation calculates the maximum stress in the spring, which occurs at the spring's top end at the maximum angle of swing. The second calculates how much the pendulum will speed up due to the inherent torque exerted by the suspension spring on the pendulum rod. In this chapter, the second equation is used to show that the suspension spring exerts a temperature effect on the pendulum's timing that is roughly as big as the thermal expansion of the pendulum rod. Anywhere from 16% to 84% of a pendulum's total temperature sensitivity is due to the suspension spring, with the actual amount depending on the spring's dimensions, modulus of elasticity, and suspended weight.Less
In 1983, K. James published two useful but rather complicated equations whose purpose was to help design the suspension spring. The equations show the effect that different spring lengths, widths, and thicknesses will have on the pendulum. The two equations are quite helpful, as the suspension spring is without doubt the most complicated part of a pendulum, despite its apparent physical simplicity. The first equation calculates the maximum stress in the spring, which occurs at the spring's top end at the maximum angle of swing. The second calculates how much the pendulum will speed up due to the inherent torque exerted by the suspension spring on the pendulum rod. In this chapter, the second equation is used to show that the suspension spring exerts a temperature effect on the pendulum's timing that is roughly as big as the thermal expansion of the pendulum rod. Anywhere from 16% to 84% of a pendulum's total temperature sensitivity is due to the suspension spring, with the actual amount depending on the spring's dimensions, modulus of elasticity, and suspended weight.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0021
- Subject:
- Physics, History of Physics
Over time, several different materials have been used for the pendulum rod such as steel, wood, and invar. The best material is quartz because of its proven stability and low thermal expansion. Steel ...
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Over time, several different materials have been used for the pendulum rod such as steel, wood, and invar. The best material is quartz because of its proven stability and low thermal expansion. Steel is used for the pendulum rod in simple ordinary clocks because it is cheap and has relatively low thermal expansion. Wood is sometimes recommended because of its low linear thermal expansion coefficient along the grain, but it is an inherently unstable material. It warps, splits, and exhibits a high mechanical creep under load. Worst of all, wood expands and contracts considerably with relative humidity. Invar is a mixture of 36% nickel and 63% iron. It is magnetic and rusts in a humid environment. A new material of interest for the pendulum rod is carbon fibre, but it may not work too well as a pendulum rod as the epoxy absorbs moisture, changing the rod's length and weight.Less
Over time, several different materials have been used for the pendulum rod such as steel, wood, and invar. The best material is quartz because of its proven stability and low thermal expansion. Steel is used for the pendulum rod in simple ordinary clocks because it is cheap and has relatively low thermal expansion. Wood is sometimes recommended because of its low linear thermal expansion coefficient along the grain, but it is an inherently unstable material. It warps, splits, and exhibits a high mechanical creep under load. Worst of all, wood expands and contracts considerably with relative humidity. Invar is a mixture of 36% nickel and 63% iron. It is magnetic and rusts in a humid environment. A new material of interest for the pendulum rod is carbon fibre, but it may not work too well as a pendulum rod as the epoxy absorbs moisture, changing the rod's length and weight.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0022
- Subject:
- Physics, History of Physics
Even though invar is the most common material used for the pendulum rod in a good clock, it is still a poor material for the purpose because of its relatively poor dimensional stability over time ...
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Even though invar is the most common material used for the pendulum rod in a good clock, it is still a poor material for the purpose because of its relatively poor dimensional stability over time compared with other materials such as quartz or platinum. Invar is usually considered for its low thermal expansion coefficient (tempco) rather than its dimensional stability. Quartz, however, is an ideal material for a pendulum rod, if you can get around the glass breakage problem. There are three types of invar available: regular invar, regular invar free machining, and super invar. Each has a different tempco and is dependent on heat treatment and any coldworking or machining that the part has received. What never gets mentioned and is not widely known is how big the changes from heat treating and machining really are.Less
Even though invar is the most common material used for the pendulum rod in a good clock, it is still a poor material for the purpose because of its relatively poor dimensional stability over time compared with other materials such as quartz or platinum. Invar is usually considered for its low thermal expansion coefficient (tempco) rather than its dimensional stability. Quartz, however, is an ideal material for a pendulum rod, if you can get around the glass breakage problem. There are three types of invar available: regular invar, regular invar free machining, and super invar. Each has a different tempco and is dependent on heat treatment and any coldworking or machining that the part has received. What never gets mentioned and is not widely known is how big the changes from heat treating and machining really are.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0023
- Subject:
- Physics, History of Physics
Almost since its invention in 1896, invar has been known to be a dimensionally unstable pendulum rod material. A few articles have been published over the years, trying to address the dimensional ...
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Almost since its invention in 1896, invar has been known to be a dimensionally unstable pendulum rod material. A few articles have been published over the years, trying to address the dimensional instability and eliminate it. Data published in 1927 showed a dimensional growth of 50 ppm over a 27-year interval. The growth was exponential, gradually slowing down with time. Invar's growth today still follows the same exponential pattern, although shrinkage is occasionally observed. In 1950, invar's instability was tied to the presence of impurities, especially carbon. The lower the level of impurities, the more stable the invar is. Invar's impurity level has been reduced over the years, so that today's invar, using the traditional furnace melt process, is more stable than it was 20 years ago. Today's regular invar has a dimensional stability of 2-27 ppm per year, at room temperature. There are three types of invar available today: regular invar, free machining invar, and super invar. Super invar's thermal expansion coefficient is three times smaller than that of regular invar.Less
Almost since its invention in 1896, invar has been known to be a dimensionally unstable pendulum rod material. A few articles have been published over the years, trying to address the dimensional instability and eliminate it. Data published in 1927 showed a dimensional growth of 50 ppm over a 27-year interval. The growth was exponential, gradually slowing down with time. Invar's growth today still follows the same exponential pattern, although shrinkage is occasionally observed. In 1950, invar's instability was tied to the presence of impurities, especially carbon. The lower the level of impurities, the more stable the invar is. Invar's impurity level has been reduced over the years, so that today's invar, using the traditional furnace melt process, is more stable than it was 20 years ago. Today's regular invar has a dimensional stability of 2-27 ppm per year, at room temperature. There are three types of invar available today: regular invar, free machining invar, and super invar. Super invar's thermal expansion coefficient is three times smaller than that of regular invar.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0024
- Subject:
- Physics, History of Physics
Every clock's pendulum needs a fine trim to adjust its rate to the desired value. This is frequently done by adding small weights to a weight pan, which is usually located about one-third of the way ...
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Every clock's pendulum needs a fine trim to adjust its rate to the desired value. This is frequently done by adding small weights to a weight pan, which is usually located about one-third of the way down the pendulum rod. The clock literature says that the effect of adding a small weight to a pendulum will vary, depending on the weight's location along the pendulum rod. The literature also says that the weight will have maximum effect on the pendulum's rate if placed halfway between the bob and the suspension spring, and will have zero effect if placed at the center of the bob or at the suspension spring. This chapter describes an experiment that was carried out to measure the position sensitivity of a pendulum rod by clamping a 24-gram weight on the pendulum rod at a given location and calculating the change in clock rate.Less
Every clock's pendulum needs a fine trim to adjust its rate to the desired value. This is frequently done by adding small weights to a weight pan, which is usually located about one-third of the way down the pendulum rod. The clock literature says that the effect of adding a small weight to a pendulum will vary, depending on the weight's location along the pendulum rod. The literature also says that the weight will have maximum effect on the pendulum's rate if placed halfway between the bob and the suspension spring, and will have zero effect if placed at the center of the bob or at the suspension spring. This chapter describes an experiment that was carried out to measure the position sensitivity of a pendulum rod by clamping a 24-gram weight on the pendulum rod at a given location and calculating the change in clock rate.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0026
- Subject:
- Physics, History of Physics
A pendulum rod's air drag has a significant effect on the pendulum's Q. Many years ago, an experiment was carried out to determine the effect of bob shape on a pendulum's Q. The results showed that a ...
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A pendulum rod's air drag has a significant effect on the pendulum's Q. Many years ago, an experiment was carried out to determine the effect of bob shape on a pendulum's Q. The results showed that a football-shaped bob, pointed horizontally in the direction of swing, had the highest Q (least air drag) of any bob shape tested. The highest Q shape had a 2:1 length-to-diameter ratio. Spherical bobs had a little lower Q and right circular cylinders, with their cylindrical axis parallel to the pendulum rod's axis, had even lower Q. This chapter describes an experiment to measure the effect of the pendulum rod on Q. The pertinent rod variable is the rod's diameter. The data show that the Q decreases as the rod's diameter increases, and that the pendulum's Q with a spherical bob is 6-20% better than with a cylindrical bob. Better Q means proportionately better timekeeping.Less
A pendulum rod's air drag has a significant effect on the pendulum's Q. Many years ago, an experiment was carried out to determine the effect of bob shape on a pendulum's Q. The results showed that a football-shaped bob, pointed horizontally in the direction of swing, had the highest Q (least air drag) of any bob shape tested. The highest Q shape had a 2:1 length-to-diameter ratio. Spherical bobs had a little lower Q and right circular cylinders, with their cylindrical axis parallel to the pendulum rod's axis, had even lower Q. This chapter describes an experiment to measure the effect of the pendulum rod on Q. The pertinent rod variable is the rod's diameter. The data show that the Q decreases as the rod's diameter increases, and that the pendulum's Q with a spherical bob is 6-20% better than with a cylindrical bob. Better Q means proportionately better timekeeping.
Harvey R. Brown
- Published in print:
- 2005
- Published Online:
- September 2006
- ISBN:
- 9780199275830
- eISBN:
- 9780191603914
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/0199275831.003.0002
- Subject:
- Philosophy, Philosophy of Science
This chapter discusses the physics of coordinate transformations. Topics covered include coordinatization of space-time, inertial coordinate systems, the linearity of inertial coordinate ...
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This chapter discusses the physics of coordinate transformations. Topics covered include coordinatization of space-time, inertial coordinate systems, the linearity of inertial coordinate transformations, and the rod and clock protocols.Less
This chapter discusses the physics of coordinate transformations. Topics covered include coordinatization of space-time, inertial coordinate systems, the linearity of inertial coordinate transformations, and the rod and clock protocols.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0001
- Subject:
- Physics, History of Physics
This chapter deals with simple pendulums and with several things that can be done to improve their accuracy. Most of the items have only a minor effect on accuracy, but they add up. The pendulum ...
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This chapter deals with simple pendulums and with several things that can be done to improve their accuracy. Most of the items have only a minor effect on accuracy, but they add up. The pendulum should be enclosed in a case to protect it from the air currents of an open room, which will push the pendulum around and give erratic timing. A metal pendulum rod is recommended over a wooden one. If the pendulum is not temperature compensated, a low thermal expansion metal like iron must be chosen for the pendulum rod. If the pendulum is not temperature compensated, the bob must be supported at its bottom edge rather than at its middle or top edge. Other tips: use a low drag bob shape, walls dose to the pendulum cause a problem with relative humidity; slide the top end of the suspension spring up and down through a narrow slot; keep the number of piece parts and mechanical joints in a pendulum to a minimum.Less
This chapter deals with simple pendulums and with several things that can be done to improve their accuracy. Most of the items have only a minor effect on accuracy, but they add up. The pendulum should be enclosed in a case to protect it from the air currents of an open room, which will push the pendulum around and give erratic timing. A metal pendulum rod is recommended over a wooden one. If the pendulum is not temperature compensated, a low thermal expansion metal like iron must be chosen for the pendulum rod. If the pendulum is not temperature compensated, the bob must be supported at its bottom edge rather than at its middle or top edge. Other tips: use a low drag bob shape, walls dose to the pendulum cause a problem with relative humidity; slide the top end of the suspension spring up and down through a narrow slot; keep the number of piece parts and mechanical joints in a pendulum to a minimum.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0004
- Subject:
- Physics, History of Physics
To determine a pendulum's axis of rotation, a small piece of paper is temporarily mounted on the front of the pendulum rod at the rod's top end, so that the paper extends up an inch or two past the ...
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To determine a pendulum's axis of rotation, a small piece of paper is temporarily mounted on the front of the pendulum rod at the rod's top end, so that the paper extends up an inch or two past the suspension spring. With the pendulum stopped, two small dots (A and B) are marked on the paper about an inch directly above and another inch directly below the top end of the free unclamped part of the suspension spring. Although the one-inch dimensions are not critical, they accurately measure the actual distance between the two dots (A and B). The pendulum must be set swinging at its normal swing amplitude, and an accurate ruler (a six-inch machinist's scale calibrated in decimal inches is ideal) is used to measure the horizontal motion of each dot. The location of the axis of rotation changes slightly with the pendulum's swing amplitude.Less
To determine a pendulum's axis of rotation, a small piece of paper is temporarily mounted on the front of the pendulum rod at the rod's top end, so that the paper extends up an inch or two past the suspension spring. With the pendulum stopped, two small dots (A and B) are marked on the paper about an inch directly above and another inch directly below the top end of the free unclamped part of the suspension spring. Although the one-inch dimensions are not critical, they accurately measure the actual distance between the two dots (A and B). The pendulum must be set swinging at its normal swing amplitude, and an accurate ruler (a six-inch machinist's scale calibrated in decimal inches is ideal) is used to measure the horizontal motion of each dot. The location of the axis of rotation changes slightly with the pendulum's swing amplitude.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0006
- Subject:
- Physics, History of Physics
The big attraction of quartz as a pendulum material is its good dimensional stability over time. Stability over time is the biggest and most needed characteristic in an accurate pendulum. In contrast ...
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The big attraction of quartz as a pendulum material is its good dimensional stability over time. Stability over time is the biggest and most needed characteristic in an accurate pendulum. In contrast to invar, which was known to be unstable almost from its beginning, quartz has a long history of being a stable material. Dimensional stability is not the same as low thermal expansion. If a pendulum is temperature compensated, as all accurate pendulums are, then it does not matter much what the thermal expansion coefficient is, so long as the compensation has been done accurately. The accuracy of temperature compensation is limited by factors other than the thermal expansion coefficient. Because of their low density, quartz pendulum rods do have one drawback: they have a much higher sensitivity to barometric pressure changes than invar.Less
The big attraction of quartz as a pendulum material is its good dimensional stability over time. Stability over time is the biggest and most needed characteristic in an accurate pendulum. In contrast to invar, which was known to be unstable almost from its beginning, quartz has a long history of being a stable material. Dimensional stability is not the same as low thermal expansion. If a pendulum is temperature compensated, as all accurate pendulums are, then it does not matter much what the thermal expansion coefficient is, so long as the compensation has been done accurately. The accuracy of temperature compensation is limited by factors other than the thermal expansion coefficient. Because of their low density, quartz pendulum rods do have one drawback: they have a much higher sensitivity to barometric pressure changes than invar.
Robert James Matthys
- Published in print:
- 2004
- Published Online:
- January 2010
- ISBN:
- 9780198529712
- eISBN:
- 9780191712791
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198529712.003.0009
- Subject:
- Physics, History of Physics
This chapter describes some transient temperature measurements made on a pendulum with a quartz pendulum rod. Time offset error occurs because different parts of the pendulum change temperature at ...
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This chapter describes some transient temperature measurements made on a pendulum with a quartz pendulum rod. Time offset error occurs because different parts of the pendulum change temperature at different rates. Before and after a temperature change, the pendulum is the right length (hopefully) and runs at the right rate. But during the temperature change, the pendulum is the wrong length, due to its different parts changing temperature at different rates, and it runs at the wrong rate during the temperature change interval. Experiments were carried out to measure the pendulum temperatures using small thermistors. The pyrex sleeve provides about one-third of the temperature compensation, while two thin-walled pyrex tubes located on opposite sides of the quartz pendulum rod provide the other two-third. The temperature data provide an interesting look into the thermodynamics of a pendulum. The suspension spring assembly changes temperature relatively slowly, whereas the bob, with its large thermal mass, changes temperature the slowest of any part of the pendulum.Less
This chapter describes some transient temperature measurements made on a pendulum with a quartz pendulum rod. Time offset error occurs because different parts of the pendulum change temperature at different rates. Before and after a temperature change, the pendulum is the right length (hopefully) and runs at the right rate. But during the temperature change, the pendulum is the wrong length, due to its different parts changing temperature at different rates, and it runs at the wrong rate during the temperature change interval. Experiments were carried out to measure the pendulum temperatures using small thermistors. The pyrex sleeve provides about one-third of the temperature compensation, while two thin-walled pyrex tubes located on opposite sides of the quartz pendulum rod provide the other two-third. The temperature data provide an interesting look into the thermodynamics of a pendulum. The suspension spring assembly changes temperature relatively slowly, whereas the bob, with its large thermal mass, changes temperature the slowest of any part of the pendulum.
Kathryn E. Slanski
- Published in print:
- 2007
- Published Online:
- January 2012
- ISBN:
- 9780197263907
- eISBN:
- 9780191734687
- Item type:
- chapter
- Publisher:
- British Academy
- DOI:
- 10.5871/bacad/9780197263907.003.0003
- Subject:
- Classical Studies, Asian and Middle Eastern History: BCE to 500CE
This chapter examines the so-called ‘rod and ring’, the identified symbol of the balance of power between the two premier institutions of ancient Mesopotamia, the palace and the temple. It proposes ...
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This chapter examines the so-called ‘rod and ring’, the identified symbol of the balance of power between the two premier institutions of ancient Mesopotamia, the palace and the temple. It proposes an identification of the ‘rod and ring’ that is rooted in the indigenous Mesopotamian conceptualization of justice. It suggests that the ‘rod and ring’ scene in royal monuments also signified righteous kingship sanctified by the gods and it communicated an aspect of the enduring relationship between the palace and the temple which served to secure the institutional continuity that endured throughout more than three millennia of regime change.Less
This chapter examines the so-called ‘rod and ring’, the identified symbol of the balance of power between the two premier institutions of ancient Mesopotamia, the palace and the temple. It proposes an identification of the ‘rod and ring’ that is rooted in the indigenous Mesopotamian conceptualization of justice. It suggests that the ‘rod and ring’ scene in royal monuments also signified righteous kingship sanctified by the gods and it communicated an aspect of the enduring relationship between the palace and the temple which served to secure the institutional continuity that endured throughout more than three millennia of regime change.
Anne Fulton, Ronald M. Hansen, Elizabeth Dorn, and Anita Hendrickson
- Published in print:
- 1996
- Published Online:
- March 2012
- ISBN:
- 9780198523161
- eISBN:
- 9780191724558
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198523161.003.0003
- Subject:
- Neuroscience, Sensory and Motor Systems
The rod-mediated sensitivity of infants is lower than that of adults while the scotopic sensitivity for full-field stimuli of infants approaches adult values earlier than those psychophysical ...
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The rod-mediated sensitivity of infants is lower than that of adults while the scotopic sensitivity for full-field stimuli of infants approaches adult values earlier than those psychophysical sensitivities that are mediated by rods at the posterior pole. For example, in ten-week-old infants, dark adapted scotopic sensitivity for full-field stimuli, whether assayed using an electroretinographic (ERG) or visually evoked potential procedures, is only about 0.5 log unit less than that of adults, while psychophysical sensitivities for test spots falling only on more central retina are at least a log unit below those of adults. This chapter examines the rod photoreceptors themselves for explanations of infants' low scotopic sensitivity. All across the retina, the structure of the rods of infants and adults differs. Moreover, developmental increases in rod outer segment (ROS) length and in content of the photosensitive compound, rhodopsin, have been documented. There appear to be regional variations in the rate of ROS maturation with both ROS and thresholds near the fovea. Thus it examines the physical and functional characteristics of infants' rods for possible relationships.Less
The rod-mediated sensitivity of infants is lower than that of adults while the scotopic sensitivity for full-field stimuli of infants approaches adult values earlier than those psychophysical sensitivities that are mediated by rods at the posterior pole. For example, in ten-week-old infants, dark adapted scotopic sensitivity for full-field stimuli, whether assayed using an electroretinographic (ERG) or visually evoked potential procedures, is only about 0.5 log unit less than that of adults, while psychophysical sensitivities for test spots falling only on more central retina are at least a log unit below those of adults. This chapter examines the rod photoreceptors themselves for explanations of infants' low scotopic sensitivity. All across the retina, the structure of the rods of infants and adults differs. Moreover, developmental increases in rod outer segment (ROS) length and in content of the photosensitive compound, rhodopsin, have been documented. There appear to be regional variations in the rate of ROS maturation with both ROS and thresholds near the fovea. Thus it examines the physical and functional characteristics of infants' rods for possible relationships.
Steven L. Buck and Roger Knight
- Published in print:
- 2003
- Published Online:
- April 2010
- ISBN:
- 9780198525301
- eISBN:
- 9780191584947
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198525301.003.0020
- Subject:
- Psychology, Cognitive Neuroscience
This chapter explores the effects of simultaneous rod and cone stimulation on rod hue influences. It shows that the balance among rod hue biases varies with test-stimulus duration. There appears to ...
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This chapter explores the effects of simultaneous rod and cone stimulation on rod hue influences. It shows that the balance among rod hue biases varies with test-stimulus duration. There appears to be little effect of prolonged cone stimulation on the balance of rod hue biases, which appears to be primarily controlled by the duration of rod stimulation. The ‘faster’ rod green bias is determined by a differential rod influence on M- versus L-cone pathways. The ‘slower’ red and blue hue biases could result from rod signals having the same sign of influence as S-cone signals in chromatic pathways.Less
This chapter explores the effects of simultaneous rod and cone stimulation on rod hue influences. It shows that the balance among rod hue biases varies with test-stimulus duration. There appears to be little effect of prolonged cone stimulation on the balance of rod hue biases, which appears to be primarily controlled by the duration of rod stimulation. The ‘faster’ rod green bias is determined by a differential rod influence on M- versus L-cone pathways. The ‘slower’ red and blue hue biases could result from rod signals having the same sign of influence as S-cone signals in chromatic pathways.
Peter Atkins
- Published in print:
- 2011
- Published Online:
- November 2020
- ISBN:
- 9780199695126
- eISBN:
- 9780191918445
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780199695126.003.0031
- Subject:
- Chemistry, Physical Chemistry
Now for that extraordinary and wonderful sense, vision. A lot of physics and physiology goes on between the object observed and the focus of its image on the retina of the eye, but the interface of ...
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Now for that extraordinary and wonderful sense, vision. A lot of physics and physiology goes on between the object observed and the focus of its image on the retina of the eye, but the interface of the image with the brain is photochemical. About 57 per cent of the photons that enter the eye reach the retina; the rest are scattered or absorbed by the ocular fluid, the fluid that fills the eye and helps to maintain its shape. You need to know that the ‘rods’ and ‘cones’, the physical receptors distributed over the retina, contain a molecule called retinal, 1, which is anchored to a protein, opsin, to give the aggregate known as rhodopsin. Here the primary act of vision takes place, in which that rhodopsin absorbs a photon. Rhodopsin is the primary receptor for light throughout the animal kingdom, which indicates that vision emerged very early in evolutionary history, no doubt because of its enormous value for survival. Incidentally, a retinal molecule resembles half a carotene molecule, one of the molecules that contribute to the colour of carrots, which is why there is an at least apocryphal connection between eating carrots and improving one’s vision. Let’s stand almost literally eye-to-eye and watch what happens when a retinal molecule in your eye absorbs a photon that might have bounced off this page as you read it. I have indicated the shape of the opsin molecule by ribbons which show in a general way where its numerous atoms lie. The photon passes through your pupil, negotiates the ocular fluid, and plunges into the retinal hotspot of rhodopsin. We see it stir up the electron cloud of the long chain of carbon atoms in the tail of the retinal molecule. That stirring briefly loosens the double bond character of the links between the atoms, and the molecule snaps into a new shape with the carbon tail now straight. The storm in the electron cloud subsides and all the bonds are restored, but now the retinal molecule is trapped in its new shape.
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Now for that extraordinary and wonderful sense, vision. A lot of physics and physiology goes on between the object observed and the focus of its image on the retina of the eye, but the interface of the image with the brain is photochemical. About 57 per cent of the photons that enter the eye reach the retina; the rest are scattered or absorbed by the ocular fluid, the fluid that fills the eye and helps to maintain its shape. You need to know that the ‘rods’ and ‘cones’, the physical receptors distributed over the retina, contain a molecule called retinal, 1, which is anchored to a protein, opsin, to give the aggregate known as rhodopsin. Here the primary act of vision takes place, in which that rhodopsin absorbs a photon. Rhodopsin is the primary receptor for light throughout the animal kingdom, which indicates that vision emerged very early in evolutionary history, no doubt because of its enormous value for survival. Incidentally, a retinal molecule resembles half a carotene molecule, one of the molecules that contribute to the colour of carrots, which is why there is an at least apocryphal connection between eating carrots and improving one’s vision. Let’s stand almost literally eye-to-eye and watch what happens when a retinal molecule in your eye absorbs a photon that might have bounced off this page as you read it. I have indicated the shape of the opsin molecule by ribbons which show in a general way where its numerous atoms lie. The photon passes through your pupil, negotiates the ocular fluid, and plunges into the retinal hotspot of rhodopsin. We see it stir up the electron cloud of the long chain of carbon atoms in the tail of the retinal molecule. That stirring briefly loosens the double bond character of the links between the atoms, and the molecule snaps into a new shape with the carbon tail now straight. The storm in the electron cloud subsides and all the bonds are restored, but now the retinal molecule is trapped in its new shape.
Edwin S. Gaustad
- Published in print:
- 2006
- Published Online:
- October 2011
- ISBN:
- 9780195305357
- eISBN:
- 9780199850662
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195305357.003.0003
- Subject:
- History, American History: early to 18th Century
In his Proposal for Promoting Useful Knowledge Among the British Plantations in America, Franklin laid out a vision for the society of grandeur and breadth. Knowledge, he thought, should be put to a ...
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In his Proposal for Promoting Useful Knowledge Among the British Plantations in America, Franklin laid out a vision for the society of grandeur and breadth. Knowledge, he thought, should be put to a practical, even pleasurable use. He put forth a new “Franklin stove” in the winter of 1740–41. He continued to give attention to Philadelphia and to ways of making it a more comfortable place in which to live. Together with Peter Collinson, he experimented on the relationship of lightning and electricity. In 1753, both Harvard and Yale awarded the honorary master of arts degree to the scientist who had never even finished high school. In 1761, he invented the glass harmonica, which consists of glass spheres of varying sizes. In 1785, he invented the “double spectacles ”, or what would be later known as bifocals.Less
In his Proposal for Promoting Useful Knowledge Among the British Plantations in America, Franklin laid out a vision for the society of grandeur and breadth. Knowledge, he thought, should be put to a practical, even pleasurable use. He put forth a new “Franklin stove” in the winter of 1740–41. He continued to give attention to Philadelphia and to ways of making it a more comfortable place in which to live. Together with Peter Collinson, he experimented on the relationship of lightning and electricity. In 1753, both Harvard and Yale awarded the honorary master of arts degree to the scientist who had never even finished high school. In 1761, he invented the glass harmonica, which consists of glass spheres of varying sizes. In 1785, he invented the “double spectacles ”, or what would be later known as bifocals.
Thomas Ryckman
- Published in print:
- 2005
- Published Online:
- April 2005
- ISBN:
- 9780195177176
- eISBN:
- 9780199835324
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/0195177177.003.0004
- Subject:
- Philosophy, Philosophy of Science
Hermann Weyl and Hans Reichenbach stood on opposite sides in a debate that ostensibly turned on whether rigid rods and ideal clocks do or should play an epistemologically fundamental role in GTR. ...
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Hermann Weyl and Hans Reichenbach stood on opposite sides in a debate that ostensibly turned on whether rigid rods and ideal clocks do or should play an epistemologically fundamental role in GTR. Weyl’s unification of gravitation and electromagnetism on the basis of an epistemological principle of “relativity of magnitude” is the first explicit example of a gauge theory. The Einstein-Pauli “prehistory” objection is considered. It is shown how Reichenbach’s “constructive axiomatization” of GTR based on rigid rods and clocks is expressly targeted on Weyl’s theory. Einstein’s epistemological objections to Weyl are belied by his own practice in pursuit of a unified field theory.Less
Hermann Weyl and Hans Reichenbach stood on opposite sides in a debate that ostensibly turned on whether rigid rods and ideal clocks do or should play an epistemologically fundamental role in GTR. Weyl’s unification of gravitation and electromagnetism on the basis of an epistemological principle of “relativity of magnitude” is the first explicit example of a gauge theory. The Einstein-Pauli “prehistory” objection is considered. It is shown how Reichenbach’s “constructive axiomatization” of GTR based on rigid rods and clocks is expressly targeted on Weyl’s theory. Einstein’s epistemological objections to Weyl are belied by his own practice in pursuit of a unified field theory.
Alf Hiltebeitel
- Published in print:
- 2011
- Published Online:
- September 2011
- ISBN:
- 9780195394238
- eISBN:
- 9780199897452
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195394238.003.0005
- Subject:
- Religion, Hinduism
Chapter 5 is about how Brahmanical authors seek to shape consensus in a post‐Vedic society affected by Buddhism and other nāstika traditions or “heterodoxies” by composing dharma texts in new genres, ...
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Chapter 5 is about how Brahmanical authors seek to shape consensus in a post‐Vedic society affected by Buddhism and other nāstika traditions or “heterodoxies” by composing dharma texts in new genres, beginning with the dharmasūtras, and soon including dharmaśāstra (headed by The Laws of Manu) and the two “epics”: the Mahābhārata and the Rāmāyaṇa. The chapter looks at how the dharmasūtras introduce consensus as one of the “sources of dharma” and underscore it practially by commending the householder life and the ”five great sacrifices” that a householder is to perform daily. It then looks at novel features of Manu, including its mixing of narrative and normative elements, and compares them with similar features of the epics. Unlike the dharmasūtras, Manu introduces a cosmological frame centered on the god Brahmā, and works in mini‐narratives about the king and the rod of punishment (daṇda) he should deploy in upholding dharma. The chapter unfolds the issues that classical Brahmanical dharma texts come to treat as basic, showing their development through them. These issues include varṇa (caste) and āśrama (life pattern or life‐stage); the theoretical origin of mixed classes; common portrayals of Śūdras and women; and increased attention to rājadharma or the dharma of kings.Less
Chapter 5 is about how Brahmanical authors seek to shape consensus in a post‐Vedic society affected by Buddhism and other nāstika traditions or “heterodoxies” by composing dharma texts in new genres, beginning with the dharmasūtras, and soon including dharmaśāstra (headed by The Laws of Manu) and the two “epics”: the Mahābhārata and the Rāmāyaṇa. The chapter looks at how the dharmasūtras introduce consensus as one of the “sources of dharma” and underscore it practially by commending the householder life and the ”five great sacrifices” that a householder is to perform daily. It then looks at novel features of Manu, including its mixing of narrative and normative elements, and compares them with similar features of the epics. Unlike the dharmasūtras, Manu introduces a cosmological frame centered on the god Brahmā, and works in mini‐narratives about the king and the rod of punishment (daṇda) he should deploy in upholding dharma. The chapter unfolds the issues that classical Brahmanical dharma texts come to treat as basic, showing their development through them. These issues include varṇa (caste) and āśrama (life pattern or life‐stage); the theoretical origin of mixed classes; common portrayals of Śūdras and women; and increased attention to rājadharma or the dharma of kings.
