Yezid Sayigh
- Published in print:
- 1999
- Published Online:
- October 2011
- ISBN:
- 9780198296430
- eISBN:
- 9780191685224
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198296430.003.0003
- Subject:
- Political Science, International Relations and Politics
Infiltration was a widespread phenomenon, as former mujahidin set up their own bands or operated on ‘contract’ for Arab military intelligence services, but neither they nor Husayni attempted to ...
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Infiltration was a widespread phenomenon, as former mujahidin set up their own bands or operated on ‘contract’ for Arab military intelligence services, but neither they nor Husayni attempted to construct modem political organizations on that basis. Egypt was the first country to conclude an armistice agreement with Israel, and, like Jordan, was anxious to avoid further conflict after 1949. The Egyptian command then placed a section of the police under another officer, ʻAbd-al-'Azim al-Saharti, to guard public installations in Gaza. Unlike the border police, the Saharti battalion, as it came to be known, was attached to the military governor's office. This caused considerable resentment among the Palestinian personnel, who took this to indicate a lower status. Palestinian anger at Israeli reprisals and Egyptian restrictions erupted in March, as demonstrators took to the streets of Gaza to demand conscription and the distribution of arms to the local population.Less
Infiltration was a widespread phenomenon, as former mujahidin set up their own bands or operated on ‘contract’ for Arab military intelligence services, but neither they nor Husayni attempted to construct modem political organizations on that basis. Egypt was the first country to conclude an armistice agreement with Israel, and, like Jordan, was anxious to avoid further conflict after 1949. The Egyptian command then placed a section of the police under another officer, ʻAbd-al-'Azim al-Saharti, to guard public installations in Gaza. Unlike the border police, the Saharti battalion, as it came to be known, was attached to the military governor's office. This caused considerable resentment among the Palestinian personnel, who took this to indicate a lower status. Palestinian anger at Israeli reprisals and Egyptian restrictions erupted in March, as demonstrators took to the streets of Gaza to demand conscription and the distribution of arms to the local population.
Burnett Bolloten
- Published in print:
- 2015
- Published Online:
- May 2016
- ISBN:
- 9781469624464
- eISBN:
- 9781469624488
- Item type:
- chapter
- Publisher:
- University of North Carolina Press
- DOI:
- 10.5149/northcarolina/9781469624464.003.0013
- Subject:
- History, European Modern History
This chapter focuses on Dr. Juan Negrín, the minister of finance, and Julio Alvarez del Vayo, the foreign minister, as the central figures in the Communists' influence over the government. Alvarez ...
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This chapter focuses on Dr. Juan Negrín, the minister of finance, and Julio Alvarez del Vayo, the foreign minister, as the central figures in the Communists' influence over the government. Alvarez del Vayo in particular was a trusted adviser to Largo Caballero during the early months of the Civil War. Alvarez del Vayo would later help the Communists implement their strategy of infiltration and domination in the early stages of the Civil War. Despite his contributions, however, the main instrument in bringing their plans to fruition in its final stages was Dr. Negrín, who even after fifty years remains the most controversial figure of the war.Less
This chapter focuses on Dr. Juan Negrín, the minister of finance, and Julio Alvarez del Vayo, the foreign minister, as the central figures in the Communists' influence over the government. Alvarez del Vayo in particular was a trusted adviser to Largo Caballero during the early months of the Civil War. Alvarez del Vayo would later help the Communists implement their strategy of infiltration and domination in the early stages of the Civil War. Despite his contributions, however, the main instrument in bringing their plans to fruition in its final stages was Dr. Negrín, who even after fifty years remains the most controversial figure of the war.
J.G. Meechan and G. Jackson
- Published in print:
- 2018
- Published Online:
- November 2020
- ISBN:
- 9780198789277
- eISBN:
- 9780191917103
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198789277.003.0014
- Subject:
- Clinical Medicine and Allied Health, Dentistry
A child’s future perceptions and expectations are likely to be conditioned by early experiences of dental treatment. Just under half of all children report low to ...
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A child’s future perceptions and expectations are likely to be conditioned by early experiences of dental treatment. Just under half of all children report low to moderate general dental anxiety, and 10–20% report high levels of dental anxiety. Montiero et al. (2014) indicate that the prevalence of needle phobia may be as high as 19% in 4- to 6-year-olds. Davidovich et al. (2015) reflected that, for general practitioners and specialists alike, Local anaesthetic (LA) injection for an anxious child was the most stressful procedure regardless of the operator’s age, gender, or years of professional experience. Despite impressive reductions in caries in children in recent years, there still exists a social gradient with inequalities in experience of dental disease, and there remains a significant cohort of children for whom extractions and restoration of teeth are necessary. Aside from emerging restorative strategies that do not require LA (e.g. atraumatic restorative technique or placement of preformed metal crowns using the Hall technique), effective and acceptable delivery of LA remains an important tool to enable successful operative dental treatment to be carried out comfortably for child patients. Effective surface anaesthesia prior to injection is very important as a child’s initial experience of LA techniques may influence their future perceptions and help in establishing trust. Cooling tissues prior to injection has been described but is rarely used, and surface anaesthesia is generally achieved with intra-oral topical agents. Although the main use of topical agents is as a pre-injection treatment, they have been used as the sole means of anaesthesia for some procedures including the extraction of mobile primary teeth. It is possible to achieve a depth of 2–3mm of anaesthesia if topical agents are used correctly: • the area of application should be dried • topical anaesthetic agent should be applied over a limited area • the anaesthetic agent should be applied for sufficient time. In the UK 5% lidocaine (lignocaine) and 18–20% (17.9%) benzocaine gels are the most commonly used agents. Benzocaine topical anaesthetic gel is not recommended for use on children under 2 years old because of an increased risk of methaemoglobinaemia.
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A child’s future perceptions and expectations are likely to be conditioned by early experiences of dental treatment. Just under half of all children report low to moderate general dental anxiety, and 10–20% report high levels of dental anxiety. Montiero et al. (2014) indicate that the prevalence of needle phobia may be as high as 19% in 4- to 6-year-olds. Davidovich et al. (2015) reflected that, for general practitioners and specialists alike, Local anaesthetic (LA) injection for an anxious child was the most stressful procedure regardless of the operator’s age, gender, or years of professional experience. Despite impressive reductions in caries in children in recent years, there still exists a social gradient with inequalities in experience of dental disease, and there remains a significant cohort of children for whom extractions and restoration of teeth are necessary. Aside from emerging restorative strategies that do not require LA (e.g. atraumatic restorative technique or placement of preformed metal crowns using the Hall technique), effective and acceptable delivery of LA remains an important tool to enable successful operative dental treatment to be carried out comfortably for child patients. Effective surface anaesthesia prior to injection is very important as a child’s initial experience of LA techniques may influence their future perceptions and help in establishing trust. Cooling tissues prior to injection has been described but is rarely used, and surface anaesthesia is generally achieved with intra-oral topical agents. Although the main use of topical agents is as a pre-injection treatment, they have been used as the sole means of anaesthesia for some procedures including the extraction of mobile primary teeth. It is possible to achieve a depth of 2–3mm of anaesthesia if topical agents are used correctly: • the area of application should be dried • topical anaesthetic agent should be applied over a limited area • the anaesthetic agent should be applied for sufficient time. In the UK 5% lidocaine (lignocaine) and 18–20% (17.9%) benzocaine gels are the most commonly used agents. Benzocaine topical anaesthetic gel is not recommended for use on children under 2 years old because of an increased risk of methaemoglobinaemia.
Peter B. Tinker and Peter Nye
- Published in print:
- 2000
- Published Online:
- November 2020
- ISBN:
- 9780195124927
- eISBN:
- 9780197561324
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195124927.003.0006
- Subject:
- Earth Sciences and Geography, Soil Science
Water is of central importance in the transport of solutes, whether by diffusion or mass flow, and whether in soils or plants (Lösch 1995). It is also extremely ...
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Water is of central importance in the transport of solutes, whether by diffusion or mass flow, and whether in soils or plants (Lösch 1995). It is also extremely important for the biota that live in the soil (Parr et al. 1981). Water is an unusual component of the environment, because its structure suggests it should be a gas at normal temperatures rather than a liquid, and it is the only common compound in the biosphere that occurs to a significant extent in the vapour, liquid and solid phases. We begin this chapter with a very brief statement of the thermodynamic approach to the study of water, which defines the water potential. Without an understanding of chemical potentials, it is difficult to deal with the relationships of ions and water in the soil and the plant. Therefore, in this chapter we give an introduction to this subject with special reference to water, which we then take further in chapters 4 and 5. A clear exposition of this is given in Nobel (1991). The concept of chemical potential is fundamental. It is a measure of the energy state of a particular compound in a particular system, and hence of the ability of a unit amount of the compound to perform work and thereby cause change. In particular, the difference in potential at different points in a system gives a measure of the tendency of the component to move from the region with the high potential to the region with the low potential. A component of a system can have various forms of potential energy in this sense, all of which contribute to the total chemical potential. Here, we exclude chemical reaction energy and kinetic energy. The main forms of energy that contribute to the chemical potential of a specified compound or material are due to its concentration (which may release energy on dilution), to its compression (which may perform work on expansion), to its position in an electrical field (which may release energy if the component is electrically charged and moves within the field), and to its position in the gravitational field (which may release energy as the component moves downwards).
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Water is of central importance in the transport of solutes, whether by diffusion or mass flow, and whether in soils or plants (Lösch 1995). It is also extremely important for the biota that live in the soil (Parr et al. 1981). Water is an unusual component of the environment, because its structure suggests it should be a gas at normal temperatures rather than a liquid, and it is the only common compound in the biosphere that occurs to a significant extent in the vapour, liquid and solid phases. We begin this chapter with a very brief statement of the thermodynamic approach to the study of water, which defines the water potential. Without an understanding of chemical potentials, it is difficult to deal with the relationships of ions and water in the soil and the plant. Therefore, in this chapter we give an introduction to this subject with special reference to water, which we then take further in chapters 4 and 5. A clear exposition of this is given in Nobel (1991). The concept of chemical potential is fundamental. It is a measure of the energy state of a particular compound in a particular system, and hence of the ability of a unit amount of the compound to perform work and thereby cause change. In particular, the difference in potential at different points in a system gives a measure of the tendency of the component to move from the region with the high potential to the region with the low potential. A component of a system can have various forms of potential energy in this sense, all of which contribute to the total chemical potential. Here, we exclude chemical reaction energy and kinetic energy. The main forms of energy that contribute to the chemical potential of a specified compound or material are due to its concentration (which may release energy on dilution), to its compression (which may perform work on expansion), to its position in an electrical field (which may release energy if the component is electrically charged and moves within the field), and to its position in the gravitational field (which may release energy as the component moves downwards).
Hillel Cohen
- Published in print:
- 2010
- Published Online:
- March 2012
- ISBN:
- 9780520257672
- eISBN:
- 9780520944886
- Item type:
- chapter
- Publisher:
- University of California Press
- DOI:
- 10.1525/california/9780520257672.003.0004
- Subject:
- History, Middle East History
Palestinian nationalists maintained that Arab refugees who were uprooted during the 1948 hostilities had the right to return to their homes. Infiltration was one of the most acute challenges faced by ...
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Palestinian nationalists maintained that Arab refugees who were uprooted during the 1948 hostilities had the right to return to their homes. Infiltration was one of the most acute challenges faced by the young state of Israel. Some infiltrators were out to kill and avenge as well as to act as spies. Others were motivated by destitution. Some of them lived by robbery and theft in the country that had arisen on the ruins of their villages, and others worked as smugglers. Arabs who crossed the border with the intention of remaining in the country jeopardized Israel's demographic balance, and smugglers undercut the country's sovereignty within its borders. It is hardly surprising, then, that the battle against infiltration, both defensive and offensive, was the focal point of Israel Defense Forces operations; the police force and military government also worked hard against it. There were collaborators with Arab intelligence organizations who conveyed information about Israel over the border, nationalists who sheltered infiltrators, and informers who turned them in.Less
Palestinian nationalists maintained that Arab refugees who were uprooted during the 1948 hostilities had the right to return to their homes. Infiltration was one of the most acute challenges faced by the young state of Israel. Some infiltrators were out to kill and avenge as well as to act as spies. Others were motivated by destitution. Some of them lived by robbery and theft in the country that had arisen on the ruins of their villages, and others worked as smugglers. Arabs who crossed the border with the intention of remaining in the country jeopardized Israel's demographic balance, and smugglers undercut the country's sovereignty within its borders. It is hardly surprising, then, that the battle against infiltration, both defensive and offensive, was the focal point of Israel Defense Forces operations; the police force and military government also worked hard against it. There were collaborators with Arab intelligence organizations who conveyed information about Israel over the border, nationalists who sheltered infiltrators, and informers who turned them in.
Abhijit Dasgupta
- Published in print:
- 2016
- Published Online:
- August 2016
- ISBN:
- 9780199461172
- eISBN:
- 9780199086986
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199461172.001.0001
- Subject:
- Sociology, Migration Studies (including Refugee Studies), Population and Demography
This volume highlights some emerging issues in the study of displaced persons in India, like the agency and voices of people who flee across an international border, the identities they forge for ...
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This volume highlights some emerging issues in the study of displaced persons in India, like the agency and voices of people who flee across an international border, the identities they forge for themselves, their relations with the hosts and their interactions with the state and non-governmental organizations. Three case studies included here are: (a) ‘Partition refugees’ from East Pakistan to West Bengal, (b) ‘Tamil refugees’ from Sri Lanka to India, and (c) ‘Bangladesh Liberation War refugees’ from East Pakistan to West Bengal. The reader will find that each case is in itself highly complex. The treatment meted out to the displaced people in India has not been consistent. The volume shows that the responses of the state to cross-border displacement have been varied over space and time.Less
This volume highlights some emerging issues in the study of displaced persons in India, like the agency and voices of people who flee across an international border, the identities they forge for themselves, their relations with the hosts and their interactions with the state and non-governmental organizations. Three case studies included here are: (a) ‘Partition refugees’ from East Pakistan to West Bengal, (b) ‘Tamil refugees’ from Sri Lanka to India, and (c) ‘Bangladesh Liberation War refugees’ from East Pakistan to West Bengal. The reader will find that each case is in itself highly complex. The treatment meted out to the displaced people in India has not been consistent. The volume shows that the responses of the state to cross-border displacement have been varied over space and time.
Dora P. Crouch
- Published in print:
- 1993
- Published Online:
- November 2020
- ISBN:
- 9780195072808
- eISBN:
- 9780197560266
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195072808.003.0016
- Subject:
- Archaeology, Greek and Roman Archaeology
A whole series of questions flows from Loy’s general understanding, such as: Was there a particular sort of land form associated with ancient Greek ...
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A whole series of questions flows from Loy’s general understanding, such as: Was there a particular sort of land form associated with ancient Greek settlements? Were settlements always located at springs, and did springs always have settlements? Why were there springs in some places and not in others, in what seemed to be the same sort of terrain? How much have the typography and the water resources changed since antiquity? How much did they change in the last 800 years B.C.? What can we tell about the water resources of antiquity from observing the modern situation? What were the relationships between ancient Greek settlements and the occurrence of karst phenomena? Was karst a geological form that had special relevance to water resource management in ancient Greece? Answers to some of these questions will become apparent as we discuss the geological aspects of ancient Greek urban history. Man-environment relations, in the ancient Greek world as elsewhere, were complex interactions of mode, duration, and intensity of human interference with the initial site conditions and with the climatic and biotic flux, affected by the resilience of the ecosystem. To understand these human communities in their physical setting, we need to study a range of features, many complex interactions, and man’s impact on the setting, realizing that our research goals and those of other experts may be widely divergent. Such complex interactions are called socionatural systems by J. W. Bennett (1976, 22). The condition of the watersheds of the hinterlands, in good times and bad, is directly pertinent to the ability of cities to extract water and transport it to municipal users. Hence the problems of erosion are not irrelevant to our topic—the management of water and the process of urbanization (Thrower and Bradbury, 1973, 59 –78; Aschmann, 1973, 362 –66). The thin, barren soil of these rocky peninsulas and islands is the result of climate not man. At the least, the currently observable extensive and permanent deforestation of uplands is locally a very recent phenomena (after the Younger Fill, to be discussed later) and therefore not a cause but a result of existing conditions.
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A whole series of questions flows from Loy’s general understanding, such as: Was there a particular sort of land form associated with ancient Greek settlements? Were settlements always located at springs, and did springs always have settlements? Why were there springs in some places and not in others, in what seemed to be the same sort of terrain? How much have the typography and the water resources changed since antiquity? How much did they change in the last 800 years B.C.? What can we tell about the water resources of antiquity from observing the modern situation? What were the relationships between ancient Greek settlements and the occurrence of karst phenomena? Was karst a geological form that had special relevance to water resource management in ancient Greece? Answers to some of these questions will become apparent as we discuss the geological aspects of ancient Greek urban history. Man-environment relations, in the ancient Greek world as elsewhere, were complex interactions of mode, duration, and intensity of human interference with the initial site conditions and with the climatic and biotic flux, affected by the resilience of the ecosystem. To understand these human communities in their physical setting, we need to study a range of features, many complex interactions, and man’s impact on the setting, realizing that our research goals and those of other experts may be widely divergent. Such complex interactions are called socionatural systems by J. W. Bennett (1976, 22). The condition of the watersheds of the hinterlands, in good times and bad, is directly pertinent to the ability of cities to extract water and transport it to municipal users. Hence the problems of erosion are not irrelevant to our topic—the management of water and the process of urbanization (Thrower and Bradbury, 1973, 59 –78; Aschmann, 1973, 362 –66). The thin, barren soil of these rocky peninsulas and islands is the result of climate not man. At the least, the currently observable extensive and permanent deforestation of uplands is locally a very recent phenomena (after the Younger Fill, to be discussed later) and therefore not a cause but a result of existing conditions.
Dora P. Crouch
- Published in print:
- 1993
- Published Online:
- November 2020
- ISBN:
- 9780195072808
- eISBN:
- 9780197560266
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195072808.003.0017
- Subject:
- Archaeology, Greek and Roman Archaeology
To get a sense of the relationship between karst geology and Greek settlement, we will look at examples from the Greek mainland, the islands of the Aegean, ...
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To get a sense of the relationship between karst geology and Greek settlement, we will look at examples from the Greek mainland, the islands of the Aegean, and Sicily. There is no attempt here to be comprehensive, as the necessary field work has not been done to make that possible, but rather these examples are selected to suggest the way that karst water potential played an important role in site selection and development. The major examples selected are Athens and Corinth for mainland Greece, Rhodes for the Aegean Islands, Assos and Priene for Ionia, and Syracuse and Akragas for Sicily. Other places will be cited briefly if the details from those sites are particularly illuminating. Karst phenomena, as we have seen, are found throughout the Greek world. Since Athens is perhaps the best documented Greek city, and has in addition a phenomenal karst system as its monumental focus, it receives here a section of its own, Chapter 18, The Well-Watered Acropolis. In Chapter 11, Planning Water Management, we discuss Corinth’s water system in comparison with that of her daughter city Syracuse. Here, however, we will consider the aspects of water at Corinth that derive from the karst geology of the area. This city is an excellent example of the adaptation of urban requirements to karst terrane, the siting of an ancient Greek city to take advantage of this natural resource. Ancient Corinth was built on gradually sloping terraces below the isolated protuberance of Acrocorinth, which acts as a reservoir, with the flow of waters through it resulting in springs (Fig. 8.1). That karst waters are to be found in perched nappes even at high altitudes accounts for the spring of Upper Peirene not far below the summit of Acrocorinth, as well as the two fountains half-way down the road from its citadel, and the fountain called Hadji Mustapha, at the immediate foot of the citadel (as reported by the late seventeenth century traveler, E. Celebi, cited in Mackay, 1967, 193–95.) The aquifers also supply the aqueduct (probably ancient) from Penteskouphia southwest of Acrocorinth.
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To get a sense of the relationship between karst geology and Greek settlement, we will look at examples from the Greek mainland, the islands of the Aegean, and Sicily. There is no attempt here to be comprehensive, as the necessary field work has not been done to make that possible, but rather these examples are selected to suggest the way that karst water potential played an important role in site selection and development. The major examples selected are Athens and Corinth for mainland Greece, Rhodes for the Aegean Islands, Assos and Priene for Ionia, and Syracuse and Akragas for Sicily. Other places will be cited briefly if the details from those sites are particularly illuminating. Karst phenomena, as we have seen, are found throughout the Greek world. Since Athens is perhaps the best documented Greek city, and has in addition a phenomenal karst system as its monumental focus, it receives here a section of its own, Chapter 18, The Well-Watered Acropolis. In Chapter 11, Planning Water Management, we discuss Corinth’s water system in comparison with that of her daughter city Syracuse. Here, however, we will consider the aspects of water at Corinth that derive from the karst geology of the area. This city is an excellent example of the adaptation of urban requirements to karst terrane, the siting of an ancient Greek city to take advantage of this natural resource. Ancient Corinth was built on gradually sloping terraces below the isolated protuberance of Acrocorinth, which acts as a reservoir, with the flow of waters through it resulting in springs (Fig. 8.1). That karst waters are to be found in perched nappes even at high altitudes accounts for the spring of Upper Peirene not far below the summit of Acrocorinth, as well as the two fountains half-way down the road from its citadel, and the fountain called Hadji Mustapha, at the immediate foot of the citadel (as reported by the late seventeenth century traveler, E. Celebi, cited in Mackay, 1967, 193–95.) The aquifers also supply the aqueduct (probably ancient) from Penteskouphia southwest of Acrocorinth.
Dora P. Crouch
- Published in print:
- 1993
- Published Online:
- November 2020
- ISBN:
- 9780195072808
- eISBN:
- 9780197560266
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195072808.003.0018
- Subject:
- Archaeology, Greek and Roman Archaeology
A city is the locus of both sociocultural and physical-technical elements in a society. To begin to understand the importance of both kinds of factors, ...
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A city is the locus of both sociocultural and physical-technical elements in a society. To begin to understand the importance of both kinds of factors, ancient cities are convenient examples to study, especially dead ones that do not “wiggle” under the microscope. By isolating one urban system (water management) we can begin to understand the complication and variability that characterize these early cities, and hence gain insight into the development of other urban systems, as well as the role that water management plays in the evolution of all cities. The received wisdom about the placement of cities usually rates defense as the primary factor, with access to arable land and concentration of trade activities being the other two important factors. A hill top, a protruding ridge, a peninsula or an isthmus between two rivers—all were sites easily defended by walls and hand weapons. Even a broad plain could be utilized if there were a slight rise that could be fortified, such as at the Mycenaean city of Tiryns in Greece. A city on a slight rise in the midst of broad fields of arable and irrigable soil was ideal. Such a formulation leaves out the possibility of deliberately choosing as a site a port city that tapped directly into grazing lands, or the importance of a balance of either fish or meat complementing cereals in the diet. It is more accurate to say that two kinds of food were necessary, either crops and fish or crops and meat. This concept broadens the number and kinds of “ideal” sites. Trade routes, the third factor, also are more complex in form and have more varied effects on urban location than early theories would admit. There are at least three kinds: 1. Overland routes (e.g., the Santa Fe Trail, with its two terminals at Independence, Mo., and Santa Fe., N.M., with Santa Fe being a crossroads where routes from Los Angeles and Mexico City also converged) 2. Land and water interchanges (the north-south land route through France crossing at Paris the east-west river route along the Seine) 3. Water-water interchanges such as New Orleans (Gulf of Mexico and Mississippi River) or Amsterdam (Rhine River and Atlantic Ocean)
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A city is the locus of both sociocultural and physical-technical elements in a society. To begin to understand the importance of both kinds of factors, ancient cities are convenient examples to study, especially dead ones that do not “wiggle” under the microscope. By isolating one urban system (water management) we can begin to understand the complication and variability that characterize these early cities, and hence gain insight into the development of other urban systems, as well as the role that water management plays in the evolution of all cities. The received wisdom about the placement of cities usually rates defense as the primary factor, with access to arable land and concentration of trade activities being the other two important factors. A hill top, a protruding ridge, a peninsula or an isthmus between two rivers—all were sites easily defended by walls and hand weapons. Even a broad plain could be utilized if there were a slight rise that could be fortified, such as at the Mycenaean city of Tiryns in Greece. A city on a slight rise in the midst of broad fields of arable and irrigable soil was ideal. Such a formulation leaves out the possibility of deliberately choosing as a site a port city that tapped directly into grazing lands, or the importance of a balance of either fish or meat complementing cereals in the diet. It is more accurate to say that two kinds of food were necessary, either crops and fish or crops and meat. This concept broadens the number and kinds of “ideal” sites. Trade routes, the third factor, also are more complex in form and have more varied effects on urban location than early theories would admit. There are at least three kinds: 1. Overland routes (e.g., the Santa Fe Trail, with its two terminals at Independence, Mo., and Santa Fe., N.M., with Santa Fe being a crossroads where routes from Los Angeles and Mexico City also converged) 2. Land and water interchanges (the north-south land route through France crossing at Paris the east-west river route along the Seine) 3. Water-water interchanges such as New Orleans (Gulf of Mexico and Mississippi River) or Amsterdam (Rhine River and Atlantic Ocean)
Dora P. Crouch
- Published in print:
- 1993
- Published Online:
- November 2020
- ISBN:
- 9780195072808
- eISBN:
- 9780197560266
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195072808.003.0031
- Subject:
- Archaeology, Greek and Roman Archaeology
Persons with some knowledge of the Athenian acropolis are likely to be aware of the very early Mycenaean spring in the north-northwest quadrant, and of the ...
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Persons with some knowledge of the Athenian acropolis are likely to be aware of the very early Mycenaean spring in the north-northwest quadrant, and of the still flowing Klepsydra Spring at the northwest corner, as well as remember stories about Poseidon’s salt spring adjacent to the Erechtheum. Yet to connect the presence of water on the Acropolis with the urban history of Athens has not been explicitly done to date, even though the Acropolis has been the focus of settlement from earliest times until today. It is the purpose of this section to set out what is known about water utilization at the Athenian Acropolis, thereby suggesting firm ecological reasons why settlement should have taken place on and near the Acropolis (Fig. 18.1). Travlos’ map series of the city of Athens (1960) centered on the Acropolis show us that this hill has always been the focus of settlement, a fact well known to the ancient Athenians themselves (Thucydides, 2:15.3– 6). I suggest that not only the defensive capabilities of the Acropolis but specifically its water supply made it the logical choice of location for groups who intended to live securely and to dominate the region. The number and diversity of water sources here is impressive. In each era it has been necessary to cope with the water that occurred naturally and to save for later use the rain and spring waters that drew settlers to this rocky outcropping. Let us note the locations of water on the Acropolis at several levels, with references to published accounts of some of the features and descriptions (based on surface reconnaissance and discussion with experts) of those for which I have not been able to find such accounts. Discussion of the geology of the Acropolis will be found with the paragraphs about the salt spring. After this topographical discussion, we will look briefly at the chronology of water on the Acropolis, followed by a concluding discussion of urban history. Immediately to the left of the Propylaea, inside the Acropolis wall, are rectangular cisterns dug into the rock of the surface, with rock-cut drainage channels leading to them from the central pathway.
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Persons with some knowledge of the Athenian acropolis are likely to be aware of the very early Mycenaean spring in the north-northwest quadrant, and of the still flowing Klepsydra Spring at the northwest corner, as well as remember stories about Poseidon’s salt spring adjacent to the Erechtheum. Yet to connect the presence of water on the Acropolis with the urban history of Athens has not been explicitly done to date, even though the Acropolis has been the focus of settlement from earliest times until today. It is the purpose of this section to set out what is known about water utilization at the Athenian Acropolis, thereby suggesting firm ecological reasons why settlement should have taken place on and near the Acropolis (Fig. 18.1). Travlos’ map series of the city of Athens (1960) centered on the Acropolis show us that this hill has always been the focus of settlement, a fact well known to the ancient Athenians themselves (Thucydides, 2:15.3– 6). I suggest that not only the defensive capabilities of the Acropolis but specifically its water supply made it the logical choice of location for groups who intended to live securely and to dominate the region. The number and diversity of water sources here is impressive. In each era it has been necessary to cope with the water that occurred naturally and to save for later use the rain and spring waters that drew settlers to this rocky outcropping. Let us note the locations of water on the Acropolis at several levels, with references to published accounts of some of the features and descriptions (based on surface reconnaissance and discussion with experts) of those for which I have not been able to find such accounts. Discussion of the geology of the Acropolis will be found with the paragraphs about the salt spring. After this topographical discussion, we will look briefly at the chronology of water on the Acropolis, followed by a concluding discussion of urban history. Immediately to the left of the Propylaea, inside the Acropolis wall, are rectangular cisterns dug into the rock of the surface, with rock-cut drainage channels leading to them from the central pathway.
Dora P. Crouch
- Published in print:
- 1993
- Published Online:
- November 2020
- ISBN:
- 9780195072808
- eISBN:
- 9780197560266
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195072808.003.0037
- Subject:
- Archaeology, Greek and Roman Archaeology
Looking back through twenty years of work on this topic, I can sum up what I have learned under two major categories: general truths and site-specific ...
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Looking back through twenty years of work on this topic, I can sum up what I have learned under two major categories: general truths and site-specific insights. Within each of these categories, I differentiate between items that were not known by me when I started and items that as far as I can tell were not known at all. First let us consider the findings that have general application. Primary are findings connected with the geological basis of Greek settlement. The ones in italics have not been known before at all, as far as I can tell. For each discovery, there is a brief discussion. 1. Relation of karst patterns to settlement in the ancient Greek world. In Part IV of this volume we have discussed this topic in a preliminary fashion. As is the case with so many details of the human situation, the relevant knowledge is in the hands of two disciplines that rarely perceive that they have any questions in common. Karst has been studied by hydrogeologists and ancient Greek settlements by classicists, with an impenetrable membrane separating the two fields of knowledge. Nevertheless, my study has conclusively demonstrated that one cannot understand either the choice of an ancient Greek site or the subsequent history of the settlement without factoring in the geological base and the water resources this base provided (Fig. 7.1). It is a pity that the lead of the noted classicist Judeich (1905 and 1931) was not followed sooner, since he illustrated his section on water supply with a geological map and section. 2. Utilization of karst in urban water systems. The work of modern engineers and geologists in such countries as Yugoslavia makes us aware that karst waters can be tapped or, to put it more strongly, harnessed for settlements. Many of their modern solutions are not dependent on advanced technology but rather on careful observation and clever manipulation. The ancient Greeks were fully capable of both. The famous pinecone experiment on the Tripoli plain of the sixth century B.C. is strong indication that the ancient engineers were examining data with an eye to manipulating karst for human purposes, and in fact we have a story, from the same area, of water being diverted down a sinkhole to drown out an unsuspecting enemy settlement.
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Looking back through twenty years of work on this topic, I can sum up what I have learned under two major categories: general truths and site-specific insights. Within each of these categories, I differentiate between items that were not known by me when I started and items that as far as I can tell were not known at all. First let us consider the findings that have general application. Primary are findings connected with the geological basis of Greek settlement. The ones in italics have not been known before at all, as far as I can tell. For each discovery, there is a brief discussion. 1. Relation of karst patterns to settlement in the ancient Greek world. In Part IV of this volume we have discussed this topic in a preliminary fashion. As is the case with so many details of the human situation, the relevant knowledge is in the hands of two disciplines that rarely perceive that they have any questions in common. Karst has been studied by hydrogeologists and ancient Greek settlements by classicists, with an impenetrable membrane separating the two fields of knowledge. Nevertheless, my study has conclusively demonstrated that one cannot understand either the choice of an ancient Greek site or the subsequent history of the settlement without factoring in the geological base and the water resources this base provided (Fig. 7.1). It is a pity that the lead of the noted classicist Judeich (1905 and 1931) was not followed sooner, since he illustrated his section on water supply with a geological map and section. 2. Utilization of karst in urban water systems. The work of modern engineers and geologists in such countries as Yugoslavia makes us aware that karst waters can be tapped or, to put it more strongly, harnessed for settlements. Many of their modern solutions are not dependent on advanced technology but rather on careful observation and clever manipulation. The ancient Greeks were fully capable of both. The famous pinecone experiment on the Tripoli plain of the sixth century B.C. is strong indication that the ancient engineers were examining data with an eye to manipulating karst for human purposes, and in fact we have a story, from the same area, of water being diverted down a sinkhole to drown out an unsuspecting enemy settlement.
Dan Furmedge and Ricky Sinharay
- Published in print:
- 2019
- Published Online:
- November 2020
- ISBN:
- 9780198812968
- eISBN:
- 9780191917226
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198812968.003.0013
- Subject:
- Clinical Medicine and Allied Health, Professional Development in Medicine
Tackling haematology is never easy. Revision can be a struggle, as it may not always be obvious which topic areas will be directly relevant to clinical practice. We ...
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Tackling haematology is never easy. Revision can be a struggle, as it may not always be obvious which topic areas will be directly relevant to clinical practice. We still, however, benefit from an understanding of these areas and an appreciation of how to do and interpret the basics and when more expertise is required. Sometimes the answers require a trip right back to the stem cell. A junior doctor’s most frequent contact with haematology is in interpreting a full blood count. In this task, the core skills of the chapter come to the fore— in response to an anaemia, we should be able to explore the possibilities of iron deficiency, vitamin deficiency, and haemolysis. On seeing a thrombocytopenia or an abnormal clotting profile, we should be able to make a clinical assessment and perform further appropriate tests, with a view to suggesting differential diagnoses. The questions in this chapter aim to build confidence in these tasks. There is a lot more to haematology, however, than a blood count. As a junior doctor, there will be regular practical challenges such as prescribing and altering anticoagulation therapy, overseeing the safe delivery of a blood transfusion, and managing acute situations such as sickle- cell crises. The way forward is to be able to master these basics and start to see the bigger picture. This means developing a feel for the more subtle symptoms and signs of haematological disease and becoming proactive in the face of abnormal blood results. As with all of the chapters in this book, it is a way of thinking that is crucial— one that allows confident management of common situations and recognition of potentially catastrophic conditions, but also one that encourages creativity and initiative. When faced with a clinical conundrum, we should have the knowledge and confidence to ask appropriately: ‘Is the answer in the blood?’
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Tackling haematology is never easy. Revision can be a struggle, as it may not always be obvious which topic areas will be directly relevant to clinical practice. We still, however, benefit from an understanding of these areas and an appreciation of how to do and interpret the basics and when more expertise is required. Sometimes the answers require a trip right back to the stem cell. A junior doctor’s most frequent contact with haematology is in interpreting a full blood count. In this task, the core skills of the chapter come to the fore— in response to an anaemia, we should be able to explore the possibilities of iron deficiency, vitamin deficiency, and haemolysis. On seeing a thrombocytopenia or an abnormal clotting profile, we should be able to make a clinical assessment and perform further appropriate tests, with a view to suggesting differential diagnoses. The questions in this chapter aim to build confidence in these tasks. There is a lot more to haematology, however, than a blood count. As a junior doctor, there will be regular practical challenges such as prescribing and altering anticoagulation therapy, overseeing the safe delivery of a blood transfusion, and managing acute situations such as sickle- cell crises. The way forward is to be able to master these basics and start to see the bigger picture. This means developing a feel for the more subtle symptoms and signs of haematological disease and becoming proactive in the face of abnormal blood results. As with all of the chapters in this book, it is a way of thinking that is crucial— one that allows confident management of common situations and recognition of potentially catastrophic conditions, but also one that encourages creativity and initiative. When faced with a clinical conundrum, we should have the knowledge and confidence to ask appropriately: ‘Is the answer in the blood?’
Sam H. Ahmedzai and Martin F. Muers
- Published in print:
- 2005
- Published Online:
- November 2011
- ISBN:
- 9780192631411
- eISBN:
- 9780191730160
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780192631411.003.0026
- Subject:
- Palliative Care, Patient Care and End-of-Life Decision Making, Pain Management and Palliative Pharmacology
This chapter examines the pathophysiological mechanisms of pain associated with respiratory disease, focusing on the chest wall, diaphragm, and mediastinal pain, and with brachial plexopathy. It ...
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This chapter examines the pathophysiological mechanisms of pain associated with respiratory disease, focusing on the chest wall, diaphragm, and mediastinal pain, and with brachial plexopathy. It explains that thoracic pain can be nociceptive, neuropathic, or mixed, and that pain may arise from the thoracic viscera, muscles, bony cage, or skin or nerve structures. Thoracic pains are mainly caused by tumour, trauma, infection, or inflammation and there are difficult pain syndromes that arise with postherpetic neuralgia, pleural involvement, mediastinal disease, and brachial plexus infiltration.Less
This chapter examines the pathophysiological mechanisms of pain associated with respiratory disease, focusing on the chest wall, diaphragm, and mediastinal pain, and with brachial plexopathy. It explains that thoracic pain can be nociceptive, neuropathic, or mixed, and that pain may arise from the thoracic viscera, muscles, bony cage, or skin or nerve structures. Thoracic pains are mainly caused by tumour, trauma, infection, or inflammation and there are difficult pain syndromes that arise with postherpetic neuralgia, pleural involvement, mediastinal disease, and brachial plexus infiltration.
Robert F. Keefer
- Published in print:
- 1999
- Published Online:
- November 2020
- ISBN:
- 9780195121025
- eISBN:
- 9780197561270
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195121025.003.0006
- Subject:
- Earth Sciences and Geography, Soil Science
Soil texture can be defined as the size and proportion of the soil particles—sand, silt, and clay—that are present in a soil. . . . Sand is the largest—from 0.05 to ...
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Soil texture can be defined as the size and proportion of the soil particles—sand, silt, and clay—that are present in a soil. . . . Sand is the largest—from 0.05 to 2mm—and considered coarse texture; consists of angular spheres or cubes. Silt is intermediate—from 0.002 to 0.05mm—and considered medium texture; consists of properties between sand and clay. Clay is the smallest, being less than 0.002mm, and considered fine texture; appears as plate-like or flakes. . . . Any individual soil can be placed on the soil textural diagram when relative amounts of sand, silt, and clay are specified. As a general rule, the type of soil can be determined by feel when squeezed between the fingers. If the soil feels harsh and gritty it would be classified as a sandy soil. One that feels smooth and not sticky or plastic would be a silt soil, and one that is sticky or plastic would be a clay. Another way to distinguish between soils is their ability to form a ribbon. Soils that will not form a ribbon are sands. Those that form a fragile ribbon are loams; those that easily form a thick ribbon are clay loams; and those that easily form a long, thin, flexible ribbon are clays. . . . To be classified a sand, the soil must have more than 45% sand. To be classified a clay, the soil must have more than 20% clay. Loam is a mixture of sand, silt, and clay in about equal proportions. It is considered “ideal” for growing plants. . . . Weight of the soil solids is called “particle density.” For most common mineral soils (soils in which organic matter is usually less than 20%), particle density is about 2.65 g/cm3. Organic soils (where organic matter is greater than 20%) are usually about half as heavy, with particle density between 1.1 to 1.4 g/cm3. This measurement would be an important factor to consider if much material was to be transported for topsoiling.
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Soil texture can be defined as the size and proportion of the soil particles—sand, silt, and clay—that are present in a soil. . . . Sand is the largest—from 0.05 to 2mm—and considered coarse texture; consists of angular spheres or cubes. Silt is intermediate—from 0.002 to 0.05mm—and considered medium texture; consists of properties between sand and clay. Clay is the smallest, being less than 0.002mm, and considered fine texture; appears as plate-like or flakes. . . . Any individual soil can be placed on the soil textural diagram when relative amounts of sand, silt, and clay are specified. As a general rule, the type of soil can be determined by feel when squeezed between the fingers. If the soil feels harsh and gritty it would be classified as a sandy soil. One that feels smooth and not sticky or plastic would be a silt soil, and one that is sticky or plastic would be a clay. Another way to distinguish between soils is their ability to form a ribbon. Soils that will not form a ribbon are sands. Those that form a fragile ribbon are loams; those that easily form a thick ribbon are clay loams; and those that easily form a long, thin, flexible ribbon are clays. . . . To be classified a sand, the soil must have more than 45% sand. To be classified a clay, the soil must have more than 20% clay. Loam is a mixture of sand, silt, and clay in about equal proportions. It is considered “ideal” for growing plants. . . . Weight of the soil solids is called “particle density.” For most common mineral soils (soils in which organic matter is usually less than 20%), particle density is about 2.65 g/cm3. Organic soils (where organic matter is greater than 20%) are usually about half as heavy, with particle density between 1.1 to 1.4 g/cm3. This measurement would be an important factor to consider if much material was to be transported for topsoiling.
Robert F. Keefer
- Published in print:
- 1999
- Published Online:
- November 2020
- ISBN:
- 9780195121025
- eISBN:
- 9780197561270
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195121025.003.0008
- Subject:
- Earth Sciences and Geography, Soil Science
Inherent properties of a soil determine the extent to which that soil will erode. These properties are soil texture, soil structure, soil permeability, and the amount ...
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Inherent properties of a soil determine the extent to which that soil will erode. These properties are soil texture, soil structure, soil permeability, and the amount of soil organic matter. Soil texture consists of a mixture of soil particle sizes of sand, silt, and clay. Soil texture is also related to water movement into the soil [infiltration] and water movement through a soil (permeability). Sand grains are large and difficult to move; however, they are easily detached. Clay particles often stick together and therefore are difficult to detach; however, once detached the clays remain suspended and are easily carried and separated from the original soil mass by water. Silt is intermediate in size between sand and clay, but silt is both easily detached and easily transported. Thus, any soil that has large amounts of silt will erode easily. Infiltration. Water moves into and within a soil through the large macropores and only a very limited amount in the small micropores. Sandy soils have many large pores allowing water to move into the soils by infiltration. Conversely, clay soils have many microspores through which water passes only very slowly. Therefore, during a moderate storm, runoff and erosion would be greater from a soil with more fine textured clays than from a soil where coarse texture dominates. Permeability. Once water enters a soil, it flows within the soil. The extent of internal movement of water in a soil is the permeability of that soil. A soil aggregate is a soil granule or soil crumb consisting of a number of soil grains, that is, silt or clay, held together by a cementing substance. Aggregation is the condition of a soil having many individual aggregates. Soils that have many large stable aggregate are more permeable and are difficult to detach and erode. An aggregate has stability when it is not broken easily by water. Soil aggregates help keep the soil receptive to rapid infiltration of water and keep water from moving over the soil and eroding it.
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Inherent properties of a soil determine the extent to which that soil will erode. These properties are soil texture, soil structure, soil permeability, and the amount of soil organic matter. Soil texture consists of a mixture of soil particle sizes of sand, silt, and clay. Soil texture is also related to water movement into the soil [infiltration] and water movement through a soil (permeability). Sand grains are large and difficult to move; however, they are easily detached. Clay particles often stick together and therefore are difficult to detach; however, once detached the clays remain suspended and are easily carried and separated from the original soil mass by water. Silt is intermediate in size between sand and clay, but silt is both easily detached and easily transported. Thus, any soil that has large amounts of silt will erode easily. Infiltration. Water moves into and within a soil through the large macropores and only a very limited amount in the small micropores. Sandy soils have many large pores allowing water to move into the soils by infiltration. Conversely, clay soils have many microspores through which water passes only very slowly. Therefore, during a moderate storm, runoff and erosion would be greater from a soil with more fine textured clays than from a soil where coarse texture dominates. Permeability. Once water enters a soil, it flows within the soil. The extent of internal movement of water in a soil is the permeability of that soil. A soil aggregate is a soil granule or soil crumb consisting of a number of soil grains, that is, silt or clay, held together by a cementing substance. Aggregation is the condition of a soil having many individual aggregates. Soils that have many large stable aggregate are more permeable and are difficult to detach and erode. An aggregate has stability when it is not broken easily by water. Soil aggregates help keep the soil receptive to rapid infiltration of water and keep water from moving over the soil and eroding it.
Robert F. Keefer
- Published in print:
- 1999
- Published Online:
- November 2020
- ISBN:
- 9780195121025
- eISBN:
- 9780197561270
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195121025.003.0009
- Subject:
- Earth Sciences and Geography, Soil Science
Erosion can be controlled by four main means, that is, improving soil structure, covering soil with plants, covering soil with mulch, and using special structures. ...
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Erosion can be controlled by four main means, that is, improving soil structure, covering soil with plants, covering soil with mulch, and using special structures. Soil structure is related to the soil tilth, or physical condition of a soil, with respect to ease of tillage or workability as shown by the fitness of a soil as a seedbed and the ease of root penetration. Other terms relating to soil structure improvement are soil aggregation and the formation of aggregates. Aggregates form when a cementing substance is present in a soil. The most important cementing substances in soil are soil polysaccharides and soil polyuronides produced as by-products from microorganisms during decomposition of organic matter. Other less important cementing substances in soil include clays, Ca, and Fe. Formation of aggregates results in improved water infiltration with reduction in erosion. Decomposition of organic matter in soils can be shown as an equation: . . . Plant and animal remains + O2 + soil microorganisms → CO2 + H2O + elements + humus + synthates + energy . . . The decomposition process has the following features: . . . 1. Oxygen is required; thus soil aeration is important. Anytime a soil is stirred or mixed by cultivation, spading, plowing, some organic matter decomposition occurs. 2. Readily available decomposable organic material is required for the microbes to work on. Green organic material, such as grass clippings, is an excellent substrate. 3. Many different types of soil microorganisms are involved in this process. Decomposition is more rapid in soils at pH 7 (neutral). 4. A product of organic decomposition is humus. Humus has many desirable features that improve a soil for plant growth. 5. Plant or animal remains are not effective in soil aggregation until they begin to decompose. 6. The more rapid the decomposition, the greater effect of soil aggregation. . . . Microbial synthates consist of polymers called “polysaccharides” and “polyuronides.” A polymer is a long-chain compound made up of single monomer units hooked together acting as a unit. The term “poly” means “many” and “saccharide” means “sugar.”
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Erosion can be controlled by four main means, that is, improving soil structure, covering soil with plants, covering soil with mulch, and using special structures. Soil structure is related to the soil tilth, or physical condition of a soil, with respect to ease of tillage or workability as shown by the fitness of a soil as a seedbed and the ease of root penetration. Other terms relating to soil structure improvement are soil aggregation and the formation of aggregates. Aggregates form when a cementing substance is present in a soil. The most important cementing substances in soil are soil polysaccharides and soil polyuronides produced as by-products from microorganisms during decomposition of organic matter. Other less important cementing substances in soil include clays, Ca, and Fe. Formation of aggregates results in improved water infiltration with reduction in erosion. Decomposition of organic matter in soils can be shown as an equation: . . . Plant and animal remains + O2 + soil microorganisms → CO2 + H2O + elements + humus + synthates + energy . . . The decomposition process has the following features: . . . 1. Oxygen is required; thus soil aeration is important. Anytime a soil is stirred or mixed by cultivation, spading, plowing, some organic matter decomposition occurs. 2. Readily available decomposable organic material is required for the microbes to work on. Green organic material, such as grass clippings, is an excellent substrate. 3. Many different types of soil microorganisms are involved in this process. Decomposition is more rapid in soils at pH 7 (neutral). 4. A product of organic decomposition is humus. Humus has many desirable features that improve a soil for plant growth. 5. Plant or animal remains are not effective in soil aggregation until they begin to decompose. 6. The more rapid the decomposition, the greater effect of soil aggregation. . . . Microbial synthates consist of polymers called “polysaccharides” and “polyuronides.” A polymer is a long-chain compound made up of single monomer units hooked together acting as a unit. The term “poly” means “many” and “saccharide” means “sugar.”
Larry D. Hinzman and Kevin C. Petrone
- Published in print:
- 2006
- Published Online:
- November 2020
- ISBN:
- 9780195154313
- eISBN:
- 9780197561928
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195154313.003.0023
- Subject:
- Earth Sciences and Geography, Environmental Geography
Hydrological processes exert strong control over biological and climatic processes in every ecosystem. They are particularly important in the boreal zone, ...
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Hydrological processes exert strong control over biological and climatic processes in every ecosystem. They are particularly important in the boreal zone, where the average annual temperatures of the air and soil are relatively near the phase-change temperature of water (Chapter 4). Boreal hydrology is strongly controlled by processes related to freezing and thawing, particularly the presence or absence of permafrost. Flow in watersheds underlain by extensive permafrost is limited to the near-surface active layer and to small springs that connect the surface with the subpermafrost groundwater. Ice-rich permafrost, near the soil surface, impedes infiltration, resulting in soils that vary in moisture content from wet to saturated. Interior Alaska has a continental climate with relatively low precipitation (Chapter 4). Soils are typically aeolian or alluvial (Chapter 3). Consequently, in the absence of permafrost, infiltration is relatively high, yielding dry surface soils. In this way, discontinuous permafrost distribution magnifies the differences in soil moisture that might normally occur along topographic gradients. Hydrological processes in the boreal forest are unique due to highly organic soils with a porous organic mat on the surface, short thaw season, and warm summer and cold winter temperatures. The surface organic layer tends to be much thicker on north-facing slopes and in valley bottoms than on south-facing slopes and ridges, reflecting primarily the distribution of permafrost. Soils are cooler and wetter above permafrost, which retards decomposition, resulting in organic matter accumulation (Chapter 15). The markedly different material properties of the soil layers also influence hydrology. The highly porous near-surface soils allow rapid infiltration and, on hillsides, downslope drainage. The organic layer also has a relatively low thermal conductivity, resulting in slow thaw below thick organic layers. The thick organic layer limits the depth of thaw each summer to about 50–100 cm above permafrost (i.e., the active layer). As the active layer thaws, the hydraulic properties change. For example, the moisture-holding capacity increases, and additional subsurface layers become available for lateral flow. The mosaic of Alaskan vegetation depends not only on disturbance history (Chapter 7) but also on hydrology (Chapter 6).
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Hydrological processes exert strong control over biological and climatic processes in every ecosystem. They are particularly important in the boreal zone, where the average annual temperatures of the air and soil are relatively near the phase-change temperature of water (Chapter 4). Boreal hydrology is strongly controlled by processes related to freezing and thawing, particularly the presence or absence of permafrost. Flow in watersheds underlain by extensive permafrost is limited to the near-surface active layer and to small springs that connect the surface with the subpermafrost groundwater. Ice-rich permafrost, near the soil surface, impedes infiltration, resulting in soils that vary in moisture content from wet to saturated. Interior Alaska has a continental climate with relatively low precipitation (Chapter 4). Soils are typically aeolian or alluvial (Chapter 3). Consequently, in the absence of permafrost, infiltration is relatively high, yielding dry surface soils. In this way, discontinuous permafrost distribution magnifies the differences in soil moisture that might normally occur along topographic gradients. Hydrological processes in the boreal forest are unique due to highly organic soils with a porous organic mat on the surface, short thaw season, and warm summer and cold winter temperatures. The surface organic layer tends to be much thicker on north-facing slopes and in valley bottoms than on south-facing slopes and ridges, reflecting primarily the distribution of permafrost. Soils are cooler and wetter above permafrost, which retards decomposition, resulting in organic matter accumulation (Chapter 15). The markedly different material properties of the soil layers also influence hydrology. The highly porous near-surface soils allow rapid infiltration and, on hillsides, downslope drainage. The organic layer also has a relatively low thermal conductivity, resulting in slow thaw below thick organic layers. The thick organic layer limits the depth of thaw each summer to about 50–100 cm above permafrost (i.e., the active layer). As the active layer thaws, the hydraulic properties change. For example, the moisture-holding capacity increases, and additional subsurface layers become available for lateral flow. The mosaic of Alaskan vegetation depends not only on disturbance history (Chapter 7) but also on hydrology (Chapter 6).
Yoram Rubin
- Published in print:
- 2003
- Published Online:
- November 2020
- ISBN:
- 9780195138047
- eISBN:
- 9780197561676
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195138047.003.0016
- Subject:
- Earth Sciences and Geography, Oceanography and Hydrology
Many of the principles guiding stochastic analysis of flow and transport processes in the vadose zone are those which we also employ in the saturated zone, and which ...
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Many of the principles guiding stochastic analysis of flow and transport processes in the vadose zone are those which we also employ in the saturated zone, and which we have explored in earlier chapters. However, there are important considerations and simplifications to be made, given the nature of the flow and of the governing equations, which we explore here and in chapter 12. The governing equation for water flow in variably saturated porous media at the smallest scale where Darcy’s law is applicable (i.e., no need for upscaling of parameters) is Richards’ equation (cf. Yeh, 1998)
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Many of the principles guiding stochastic analysis of flow and transport processes in the vadose zone are those which we also employ in the saturated zone, and which we have explored in earlier chapters. However, there are important considerations and simplifications to be made, given the nature of the flow and of the governing equations, which we explore here and in chapter 12. The governing equation for water flow in variably saturated porous media at the smallest scale where Darcy’s law is applicable (i.e., no need for upscaling of parameters) is Richards’ equation (cf. Yeh, 1998)
Yoram Rubin
- Published in print:
- 2003
- Published Online:
- November 2020
- ISBN:
- 9780195138047
- eISBN:
- 9780197561676
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195138047.003.0017
- Subject:
- Earth Sciences and Geography, Oceanography and Hydrology
This chapter is an extension of our discussion on transport in chapters 7 to 10. Our goal here is to explore a few aspects of the transport problem which are unique to ...
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This chapter is an extension of our discussion on transport in chapters 7 to 10. Our goal here is to explore a few aspects of the transport problem which are unique to variably saturated soils. The heterogeneity of soils affects transport of solutes in the vadose zone in different ways. It leads to irregular and hard-to-predict spreading of the solutes. The solutes may be channeled through highly conductive flow channels where diffusion plays only a minor role. This may lead to concentrations which are high and travel times which are fast compared to what one may anticipate by assuming that the medium is homogeneous. Evidence for such behavior was found in field experiments (cf. Wierenga et al., 1991; Ellsworth et al., 1991; Ritsema et al., 1998; Sassner et al., 1994) and in large-scale laboratory experiments (Dagan et al., 1991). Hence, the effects of heterogeneity must be recognized and modeled. The effects of heterogeneity can be modeled by employing the stochastic concepts discussed in earlier chapters. The approach for modeling contaminant transport which is the least restrictive in terms of assumptions introduced is the MC simulation. This approach will be reviewed briefly in section 12.1. Modeling of the mean concentration along our discussion in chapter 8 is computationally less demanding compared to MC simulations, yet is less informative since the concentration in the field can hardly be expected to be equal to its expected value. Applications along that line are limited since deriving the macrodispersion coefficients needed for such an undertaking is difficult. Nonetheless, we shall discussed this approach in section 12.2, for the insight into the transport processes it provides. A few simple models are available for gravitational flow through shallow depths. These methods are of course limited in applications, yet they are less demanding in terms of data requirements and the computational efforts involved. Such methods are the focus of the last section in this chapter. The concept of MC simulation was discussed in earlier chapters.
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This chapter is an extension of our discussion on transport in chapters 7 to 10. Our goal here is to explore a few aspects of the transport problem which are unique to variably saturated soils. The heterogeneity of soils affects transport of solutes in the vadose zone in different ways. It leads to irregular and hard-to-predict spreading of the solutes. The solutes may be channeled through highly conductive flow channels where diffusion plays only a minor role. This may lead to concentrations which are high and travel times which are fast compared to what one may anticipate by assuming that the medium is homogeneous. Evidence for such behavior was found in field experiments (cf. Wierenga et al., 1991; Ellsworth et al., 1991; Ritsema et al., 1998; Sassner et al., 1994) and in large-scale laboratory experiments (Dagan et al., 1991). Hence, the effects of heterogeneity must be recognized and modeled. The effects of heterogeneity can be modeled by employing the stochastic concepts discussed in earlier chapters. The approach for modeling contaminant transport which is the least restrictive in terms of assumptions introduced is the MC simulation. This approach will be reviewed briefly in section 12.1. Modeling of the mean concentration along our discussion in chapter 8 is computationally less demanding compared to MC simulations, yet is less informative since the concentration in the field can hardly be expected to be equal to its expected value. Applications along that line are limited since deriving the macrodispersion coefficients needed for such an undertaking is difficult. Nonetheless, we shall discussed this approach in section 12.2, for the insight into the transport processes it provides. A few simple models are available for gravitational flow through shallow depths. These methods are of course limited in applications, yet they are less demanding in terms of data requirements and the computational efforts involved. Such methods are the focus of the last section in this chapter. The concept of MC simulation was discussed in earlier chapters.
Thomas S. Bianchi
- Published in print:
- 2006
- Published Online:
- November 2020
- ISBN:
- 9780195160826
- eISBN:
- 9780197562048
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195160826.003.0009
- Subject:
- Earth Sciences and Geography, Geochemistry
The hydrologic cycle has received considerable attention in recent years with particular interest in the dynamics of land–atmosphere exchanges as it ...
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The hydrologic cycle has received considerable attention in recent years with particular interest in the dynamics of land–atmosphere exchanges as it relates to global climate change and the need for more accurate numbers in global circulation models (GCMs). Recent advance in remote sensing and operational weather forecasts have significantly improved the ability to monitor the hydrologic cycle over broad regions (Vörösmarty and Peterson, 2000). The application of hydrologic models in understanding interactions between the watersheds and estuaries is critical when examining seasonal changes in the biogeochemical cycles of estuaries. Water is the most abundant substance on the Earth’s surface with liquid water covering approximately 70% of the Earth. Most of the water (96%) in the reservoir on the Earth’s surface is in the global ocean. The remaining water, predominantly stored in the form of ice in polar regions, is distributed throughout the continents and atmosphere—estuaries represent a very small fraction of this total reservoir as a subcomponent of rivers. Water is moving continuously through these reservoirs. For example, there is a greater amount of evaporation than precipitation over the oceans; this imbalance is compensated by inputs from continental runoff. The most prolific surface runoff to the oceans is from rivers which discharge approximately 37,500 km3 y−1 (Shiklomanov and Sokolov, 1983). The 10 most significant rivers, in rank of water discharge, account for approximately 30% of the total discharge to the oceans (Milliman and Meade, 1983; Meade, 1996). The most significant source of evaporation to the global hydrologic cycle occurs over the oceans; this occurs nonuniformly and is well correlated with latitudinal gradients of incident radiation and temperature. The flow of water from the atmosphere to the ocean and continents occurs in the form of rain, snow, and ice. Average turnover times of water in these reservoirs can range from 2640 y in the oceans to 8.2 d (days) in the atmosphere (Henshaw et al., 2000; table 3.1). The aqueous constituents of organic materials, such as overall biomass, have an even shorter turnover time (5.3 d). These differences in turnover rate are critical in controlling rates of biogeochemical processes in aquatic systems.
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The hydrologic cycle has received considerable attention in recent years with particular interest in the dynamics of land–atmosphere exchanges as it relates to global climate change and the need for more accurate numbers in global circulation models (GCMs). Recent advance in remote sensing and operational weather forecasts have significantly improved the ability to monitor the hydrologic cycle over broad regions (Vörösmarty and Peterson, 2000). The application of hydrologic models in understanding interactions between the watersheds and estuaries is critical when examining seasonal changes in the biogeochemical cycles of estuaries. Water is the most abundant substance on the Earth’s surface with liquid water covering approximately 70% of the Earth. Most of the water (96%) in the reservoir on the Earth’s surface is in the global ocean. The remaining water, predominantly stored in the form of ice in polar regions, is distributed throughout the continents and atmosphere—estuaries represent a very small fraction of this total reservoir as a subcomponent of rivers. Water is moving continuously through these reservoirs. For example, there is a greater amount of evaporation than precipitation over the oceans; this imbalance is compensated by inputs from continental runoff. The most prolific surface runoff to the oceans is from rivers which discharge approximately 37,500 km3 y−1 (Shiklomanov and Sokolov, 1983). The 10 most significant rivers, in rank of water discharge, account for approximately 30% of the total discharge to the oceans (Milliman and Meade, 1983; Meade, 1996). The most significant source of evaporation to the global hydrologic cycle occurs over the oceans; this occurs nonuniformly and is well correlated with latitudinal gradients of incident radiation and temperature. The flow of water from the atmosphere to the ocean and continents occurs in the form of rain, snow, and ice. Average turnover times of water in these reservoirs can range from 2640 y in the oceans to 8.2 d (days) in the atmosphere (Henshaw et al., 2000; table 3.1). The aqueous constituents of organic materials, such as overall biomass, have an even shorter turnover time (5.3 d). These differences in turnover rate are critical in controlling rates of biogeochemical processes in aquatic systems.