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Can a fish climb a ladder?  

Science.gov (United States)

How do fish swim upstream past a dam? This material, part of a series about the future of energy, introduces students to the fish ladder. Students read how large rivers with dams are made passable to fish migrating upstream and view both a photograph and diagram of a fish ladder. Copyright 2005 Eisenhower National Clearinghouse

Project, Iowa P.

2004-01-01

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New Concepts in Fish Ladder Design. Part 1. Summary. Final Project Report.  

Science.gov (United States)

The report looks at the most active periods of fishway research since 1938 as background for a project to apply fundamental fluid and bio-mechanics to fishway design, and develop more cost effective fish passage facilities with primary application to smal...

J. F. Orsborn

1985-01-01

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New Concepts in Fish Ladder Design, Volume III of IV, Assessment of Fishway Development and Design, 1982-1983 Final Report.  

Energy Technology Data Exchange (ETDEWEB)

This volume covers the broad, though relatively short, historical basis for this project. The historical developments of certain design features, criteria and research activities are traced. Current design practices are summarized based on the results of an international survey and interviews with agency personnel and consultants. The fluid mechanics and hydraulics of fishway systems are discussed. Fishways (or fishpasses) can be classified in two ways: (1) on the basis of the method of water control (chutes, steps (ladders), or slots); and (2) on the basis of the degree and type of water control. This degree of control ranges from a natural waterfall to a totally artificial environment at a hatchery. Systematic procedures for analyzing fishways based on their configuration, species, and hydraulics are presented. Discussions of fish capabilities, energy expenditure, attraction flow, stress and other factors are included.

Powers, Patrick D.; Orsborn, John F.

1985-08-01

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Selectivity of fish ladders: a bottleneck in Neotropical fish movement  

Directory of Open Access Journals (Sweden)

Full Text Available Although dozens of fish ladders have been constructed at dams of Brazilian reservoirs, there are few studies evaluating their efficiency as a tool for the conservation of Neotropical ichthyofauna, especially for migratory species. Therefore, the present study evaluated the selectivity of the species that entered and ascended the fish ladder located next to Lajeado Dam (Luis Eduardo Magalhães Hydroelectric Power Plant) on the Tocantins River. Samples were taken monthly from November, 2002 through October, 2003, in the resting pools of the ladder, using cast nets, and in the downstream stretch, using gillnets. The selectivity of the ladder in attracting fish was evaluated by comparing the occurrence, relative abundance, dominance and the congruence of abundance ranks of migratory and non-migratory species in the ladder and in the stretch of river immediately downstream. Species richness and fish abundance in the resting pools were used to evaluate selectivity along the ladder. The effects on selectivity by temporal variations in water level downriver and maximum flow velocity in the fish ladder were also analyzed. Out of the 130 species recorded downriver, 62.3% were caught in the ladder, and migratory species were clearly favored. However, more than 2/3 of the catch belonged to only three species (Rhaphiodon vulpinus, Psectrogaster amazonica and Oxydoras niger). Although the majority of the species that entered the ladder were able to reach its top, there was a sharp reduction in abundance of individuals towards the top. Temporal variations in the water level below the dam influenced richness and abundance of fish concentrated downstream and in the ladder, with lower values during periods of low water. In the ladder, a maximum flow velocity of 2.3 m/s, although also selective, proved to be more appropriate for fish ascension than a velocity of 2.8 m/s. It was concluded that the entry and ascension of the fish in the ladder were not congruent with their proportions in the downriver stretch: fish samples in the ladder were clearly dominated by a few species, including some that do not need to be translocated. Thus, selectivity constitutes an important bottleneck to initiatives for translocating fish aimed at conserving their stocks or biodiversity. It is urgent to review the decision-making process for the construction of fish passages and to evaluate the functioning of those already operating.Dezenas de escadas de peixes foram construídas em barragens de reservatórios brasileiros, mas são raros os estudos acerca de suas eficiências como instrumentos de conservação da ictiofauna Neotropical, em especial de espécies migradoras. Neste contexto, o presente estudo teve como objetivo avaliar a seletividade específica no ingresso e ascensão de peixes na escada localizada junto à barragem de Lajeado (UHE Luis Eduardo Magalhães, rio Tocantins). Amostragens foram realizadas mensalmente de novembro de 2002 a outubro de 2003 nos tanques de descanso da escada, utilizando tarrafas, e no trecho a jusante, utilizando redes de espera. A avaliação da seletividade no ingresso da escada foi realizada através da comparação da ocorrência, abundância relativa, dominância e congruência dos ranks de abundância de espécies migradoras e não migradoras na escada e no trecho imediatamente a jusante. A riqueza e abundância específica nos diferentes tanques de descanso foram utilizadas para avaliar a seletividade ao longo da escada. Os efeitos das variações temporais do nível hidrométrico de jusante e da velocidade de fluxo na seletividade foram também analisados. Das 130 espécies registradas a jusante, 63,2% foram capturadas na escada, com claro favorecimento das espécies migradoras. Entretanto, mais de 2/3 das capturas pertenceram a apenas três espécies (Rhaphiodon vulpinus, Psectrogaster amazonica e Oxydoras niger). Embora a maioria das espécies que ingressa na escada possa alcançar seu topo, constatou-se uma redução pronunciada na abundância. Variações temporais no nível da água a jusan

Carlos Sérgio Agostinho; Angelo Antônio Agostinho; Fernando Pelicice; Deusimar Augusto de Almeida; Elineide Eugênio Marques

2007-01-01

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Fish ladders: safe fish passage or hotspot for predation?  

Directory of Open Access Journals (Sweden)

Full Text Available Fish ladders are a strategy for conserving biodiversity, as they can provide connectivity between fragmented habitats and reduce predation on shoals that accumulate immediately below dams. Although the impact of predation downstream of reservoirs has been investigated, especially in juvenile salmonids during their downstream movements, nothing is known about predation on Neotropical fish in the attraction and containment areas commonly found in translocation facilities. This study analysed predation in a fish passage system at the Lajeado Dam on the Tocantins River in Brazil. The abundance, distribution, and the permanence (time spent) of large predatory fish along the ladder, the injuries imposed by piranhas during passage and the presence of other vertebrate predators were investigated. From December 2002 to October 2003, sampling was conducted in four regions (downstream, along the ladder, in the forebay, and upstream of the reservoir) using gillnets, cast nets and counts or visual observations. The captured fish were tagged with thread and beads, and any mutilations were registered. Fish, birds and dolphins were the main predator groups observed, with a predominance of the first two groups. The entrance to the ladder, in the downstream region, was the area with the highest number of large predators and was the only region with relevant non-fish vertebrates. The main predatory fish species were Rhaphiodon vulpinus, Hydrolycus armatus, and Serrasalmus rhombeus. Tagged individuals were detected predating along the ladder for up to 90 days. Mutilations caused by Serrasalmus attacks were noted in 36% of species and 4% of individuals at the top of the ladder. Our results suggested that the high density of fish in the restricted ladder environment, which is associated with injuries suffered along the ladder course and the presence of multiple predator groups with different predation strategies, transformed the fish corridor into a hotspot for predation.Passagens para peixes têm sido consideradas como estratégias para conservação da biodiversidade, visando além de assegurar os deslocamentos entre habitats fragmentados, atenuar a mortalidade por predação dos estratos populacionais que se concentram nos trechos imediatamente abaixo de barragens. Embora a mortalidade por predação no trecho a jusante de reservatórios tenha sido bem investigada, especialmente sobre os juvenis de salmonídeos em movimentos descendentes, nada se sabe acerca da predação de peixes neotropicais em áreas de atração e confinamento de peixes, eventos comuns a essas facilidades de transposição. Nesse estudo são analisados aspectos da predação em um sistema de transposição de peixes (barragem de Lajeado, rio Tocantins, Brasil), buscando avaliar a abundância, a distribuição e o tempo de permanência de grandes peixes predadores na escada, as injúrias impostas por piranhas durante a passagem e a ocorrência de outros vertebrados predadores. Para isso foram realizadas amostragens a jusante, ao longo da escada, no trecho imediatamente acima da barragem e a montante do reservatório, utilizando redes de espera, tarrafas e contagens ou registros visuais durante o período de um ano (Novembro de 2002 a Outubro de 2003). Marcações com linha e missanga e registro de mutilações foram também realizados em concomitância. Peixes, aves, quelônios e cetáceos foram os principais grupos de predadores observados, com predomínio dos dois primeiros. A área nas imediações da entrada da escada, a jusante, foi a região com maior número de grandes predadores, sendo a única de relevância para vertebrados não peixes. Indivíduos marcados permaneceram na escada exercendo a piscivoria por até 90 dias. Rhaphiodon vulpinus, Hydrolycus armatus e Serrasalmus rhombeus foram os principais peixes predadores. Mutilações por ataques de Serrasalmus atingiram 36% das espécies e alcançaram 4% dos indivíduos no topo da escada. Os resultados sugerem que a alta densidade de peixes no ambiente restrito da escada, associada às inj

Angelo Antonio Agostinho; Carlos Sergio Agostinho; Fernando Mayer Pelicice; Elineide Eugênio Marques

2012-01-01

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New Concepts in Fish Ladder Design, Part I of IV, Summary Report, 1982-1984 Final Project Report.  

Energy Technology Data Exchange (ETDEWEB)

The report looks at the most active periods of fishway research since 1938 as background for a project to apply fundamental fluid and bio-mechanics to fishway design, and develop more cost effective fish passage facilities with primary application to small scale hydropower facilities. Also discussed are new concepts in fishway design, an assessment of fishway development and design, and an analysis of barriers to upstream migration. (ACR)

Orsborn, John F.

1985-08-01

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Selectivity of fish ladders: a bottleneck in Neotropical fish movement  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Dezenas de escadas de peixes foram construídas em barragens de reservatórios brasileiros, mas são raros os estudos acerca de suas eficiências como instrumentos de conservação da ictiofauna Neotropical, em especial de espécies migradoras. Neste contexto, o presente estudo teve como objetivo avaliar a seletividade específica no ingresso e ascensão de peixes na escada localizada junto à barragem de Lajeado (UHE Luis Eduardo Magalhães, rio Tocantins). Amostragens f (more) oram realizadas mensalmente de novembro de 2002 a outubro de 2003 nos tanques de descanso da escada, utilizando tarrafas, e no trecho a jusante, utilizando redes de espera. A avaliação da seletividade no ingresso da escada foi realizada através da comparação da ocorrência, abundância relativa, dominância e congruência dos ranks de abundância de espécies migradoras e não migradoras na escada e no trecho imediatamente a jusante. A riqueza e abundância específica nos diferentes tanques de descanso foram utilizadas para avaliar a seletividade ao longo da escada. Os efeitos das variações temporais do nível hidrométrico de jusante e da velocidade de fluxo na seletividade foram também analisados. Das 130 espécies registradas a jusante, 63,2% foram capturadas na escada, com claro favorecimento das espécies migradoras. Entretanto, mais de 2/3 das capturas pertenceram a apenas três espécies (Rhaphiodon vulpinus, Psectrogaster amazonica e Oxydoras niger). Embora a maioria das espécies que ingressa na escada possa alcançar seu topo, constatou-se uma redução pronunciada na abundância. Variações temporais no nível da água a jusante da barragem influenciaram a riqueza e a abundância de peixes que se concentram na entrada e dentro da escada, com redução nos valores durante períodos de níveis baixos. Já na escada, a velocidade de fluxo de 2,3 m.s-1, embora também seletiva, mostrou-se mais adequada à ascensão de peixes em relação a de 2,8 m.s-1. Conclui-se, portanto, que o ingresso e a ascensão de peixes na escada não são congruentes com a composição e relações de abundância das espécies no trecho a jusante. O conjunto de espécies que efetivamente ascende a escada é dominado por poucas espécies, podendo incluir entre as dominantes aquelas que não necessitam ser transpostas. Dessa maneira, a seletividade se constitui num importante gargalo nas iniciativas de transposição de peixes visando a conservação dos estoques ou da biodiversidade, sendo urgente a revisão do processo decisório sobre a construção destes dispositivos e a avaliação acerca do funcionamento daquelas já construídas. Abstract in english Although dozens of fish ladders have been constructed at dams of Brazilian reservoirs, there are few studies evaluating their efficiency as a tool for the conservation of Neotropical ichthyofauna, especially for migratory species. Therefore, the present study evaluated the selectivity of the species that entered and ascended the fish ladder located next to Lajeado Dam (Luis Eduardo Magalhães Hydroelectric Power Plant) on the Tocantins River. Samples were taken monthly fr (more) om November, 2002 through October, 2003, in the resting pools of the ladder, using cast nets, and in the downstream stretch, using gillnets. The selectivity of the ladder in attracting fish was evaluated by comparing the occurrence, relative abundance, dominance and the congruence of abundance ranks of migratory and non-migratory species in the ladder and in the stretch of river immediately downstream. Species richness and fish abundance in the resting pools were used to evaluate selectivity along the ladder. The effects on selectivity by temporal variations in water level downriver and maximum flow velocity in the fish ladder were also analyzed. Out of the 130 species recorded downriver, 62.3% were caught in the ladder, and migratory species were clearly favored. However, more than 2/3 of the catch belonged to only three species (Rhaphiodon vulpinus, Psectrogaster amazonica and Oxydo

Agostinho, Carlos Sérgio; Agostinho, Angelo Antônio; Pelicice, Fernando; Almeida, Deusimar Augusto de; Marques, Elineide Eugênio

2007-01-01

8

Fish ladders: safe fish passage or hotspot for predation?  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Passagens para peixes têm sido consideradas como estratégias para conservação da biodiversidade, visando além de assegurar os deslocamentos entre habitats fragmentados, atenuar a mortalidade por predação dos estratos populacionais que se concentram nos trechos imediatamente abaixo de barragens. Embora a mortalidade por predação no trecho a jusante de reservatórios tenha sido bem investigada, especialmente sobre os juvenis de salmonídeos em movimentos descendent (more) es, nada se sabe acerca da predação de peixes neotropicais em áreas de atração e confinamento de peixes, eventos comuns a essas facilidades de transposição. Nesse estudo são analisados aspectos da predação em um sistema de transposição de peixes (barragem de Lajeado, rio Tocantins, Brasil), buscando avaliar a abundância, a distribuição e o tempo de permanência de grandes peixes predadores na escada, as injúrias impostas por piranhas durante a passagem e a ocorrência de outros vertebrados predadores. Para isso foram realizadas amostragens a jusante, ao longo da escada, no trecho imediatamente acima da barragem e a montante do reservatório, utilizando redes de espera, tarrafas e contagens ou registros visuais durante o período de um ano (Novembro de 2002 a Outubro de 2003). Marcações com linha e missanga e registro de mutilações foram também realizados em concomitância. Peixes, aves, quelônios e cetáceos foram os principais grupos de predadores observados, com predomínio dos dois primeiros. A área nas imediações da entrada da escada, a jusante, foi a região com maior número de grandes predadores, sendo a única de relevância para vertebrados não peixes. Indivíduos marcados permaneceram na escada exercendo a piscivoria por até 90 dias. Rhaphiodon vulpinus, Hydrolycus armatus e Serrasalmus rhombeus foram os principais peixes predadores. Mutilações por ataques de Serrasalmus atingiram 36% das espécies e alcançaram 4% dos indivíduos no topo da escada. Os resultados sugerem que a alta densidade de peixes no ambiente restrito da escada, associada às injúrias sofridas no percurso e a presença de múltiplos predadores dotados de estratégias de predação variadas, transforme o corredor para passagem de peixes em um "hotspot" de predação Abstract in english Fish ladders are a strategy for conserving biodiversity, as they can provide connectivity between fragmented habitats and reduce predation on shoals that accumulate immediately below dams. Although the impact of predation downstream of reservoirs has been investigated, especially in juvenile salmonids during their downstream movements, nothing is known about predation on Neotropical fish in the attraction and containment areas commonly found in translocation facilities. T (more) his study analysed predation in a fish passage system at the Lajeado Dam on the Tocantins River in Brazil. The abundance, distribution, and the permanence (time spent) of large predatory fish along the ladder, the injuries imposed by piranhas during passage and the presence of other vertebrate predators were investigated. From December 2002 to October 2003, sampling was conducted in four regions (downstream, along the ladder, in the forebay, and upstream of the reservoir) using gillnets, cast nets and counts or visual observations. The captured fish were tagged with thread and beads, and any mutilations were registered. Fish, birds and dolphins were the main predator groups observed, with a predominance of the first two groups. The entrance to the ladder, in the downstream region, was the area with the highest number of large predators and was the only region with relevant non-fish vertebrates. The main predatory fish species were Rhaphiodon vulpinus, Hydrolycus armatus, and Serrasalmus rhombeus. Tagged individuals were detected predating along the ladder for up to 90 days. Mutilations caused by Serrasalmus attacks were noted in 36% of species and 4% of individuals at the top of the ladder. Our results suggested that the high density of fi

Agostinho, Angelo Antonio; Agostinho, Carlos Sergio; Pelicice, Fernando Mayer; Marques, Elineide Eugênio

2012-10-01

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Movements of adult Atlantic salmon in relation to a hydroelectric dam and fish ladder  

Energy Technology Data Exchange (ETDEWEB)

The movements of adult Atlantic salmon were recorded as they approached, entered and ascended the pool-and-orifice fish ladder at Pitlochry Dam, Scotland. Thirty-nine returning salmon were captured in the River Tummel by rod-and-line angling, radio-tagged and released near where they were caught. The subsequent movements of each fish were then monitored. An electronic fish counter collected additional data on movements of untagged fish past a fixed point in the ladder. Of the 39 fish that were radio-tagged, 29 individuals were recorded approaching and ascending the ladder. The remaining fish either did not approach the dam (three fish), approached the dam after detailed tracking had ended (two fish), were recaptured by anglers (three fish), or the radio tags failed (two fish). Salmon released earlier in the year delayed longer before first approaching the dam. Delays between first approaching the dam and ascent of the ladder were greater for fish that approached the dam earlier. The majority of salmon visited the ladder entrance more than once (maximum 10 visits) before ascending. Having entered, all but four salmon ascended the fish ladder successfully on their first attempt. The four individuals that failed to do so succeeded on their second attempt. The rate at which salmon ascended the ladder was related directly to temperature. The shortest ascent time of a radio-tagged salmon was 5.25 h. Movements of eight of 11 tagged fish through the ladder ceased with the onset of darkness but continued on the following morning. No radio-tagged fish entered the ladder at temperatures below 9{sup o}C. Similarly, few untagged fish were recorded ascending the ladder by the electronic fish counter at water temperatures below 8.5{sup o}C. Records from the fish counter indicated that 92% of upstream movements were made during daylight. (author)

Gowans, A.R.D. [Freshwater Fisheries Laboratory, Pitlochry (United Kingdom)]|[Aberdeen University (United Kingdom). Dept. of Zoology; Armstrong, J.D. [Freshwater Fisheries Laboratory, Pitlochry (United Kingdom); Priede, I.G. [Aberdeen University (United Kingdom). Dept. of Zoology

1999-04-01

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New Concepts in Fish Ladder Design: Analysis of Barriers to Upstream Fish Migration, Volume IV of IV, Investigation of the Physical and Biological Conditions Affecting Fish Passage Success at Culverts and Waterfalls, 1982-1984 Final Report.  

Energy Technology Data Exchange (ETDEWEB)

A synopsis of the project components was prepared to provide an overview for persons who are not fisheries scientists or engineers. This short report can be used also by technical persons who are interested in the scope of the project, and as a summary of the three main reports. The contents includes an historical perspective on fishway design which provides the basis for this project. The major project accomplishments and significant additions to the body of knowledge about the analysis and design of fishways are discussed. In the next section the research project organization, objectives and components are presented to familiarize the reader with the scope of this project. The summary report concludes with recommendations for assisting in the enhancement and restoration of fisheries resources from the perspective of fish passage problems and their solution. Promising research topics are included.

Powers, Patrick D.; Orsborn, John F.

1985-08-01

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Selection of an experimental fish ladder located at the dam of the Itaipu Binacional, Paraná River, Brazil  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese A seleção específica de uma escada de peixes do tipo seqüência de tanques, com passagem de fundo (tipo weir and orifice), na barragem da hidrelétrica de Itaipu (rio Paraná), foi avaliada através de amostragens no rio a jusante (amostragem trimestral em 1997) e em dois pontos ao longo da escada (10 e 27m de altura; nov/94 a jan/97 e nov/94 a fev/97, respectivamente). Das 65 espécies registradas no rio imediatamente a jusante da barragem, 27 foram capturadas na esc (more) ada. As espécies com maior densidade na escada, em sua maioria migradoras, tiveram abundância moderada ou baixa a jusante. Entre as mais abundantes a jusante, apenas uma, não migradora, foi registrada na escada. A escada apresentou seleção negativa aos grandes pimelodídeos migradores que pode ser superada com a ampliação na escala do projeto. As amostragens evidenciaram baixa seletividade específica ao longo da escada, sendo seu modelo hidráulico satisfatório na atração e eficiente na ascensão de peixes. Abstract in english The specific selection of a weir and orifice type experimental fish ladder in the dam of the Itaipu Reservoir (Paraná River) was evaluated by samplings in the river downstream and at two points along the ladder (at heights of 10 m and 27 m) during 28 months. Among the 65 species recorded in the river (immediate downstream of the dam), 27 were captured on the ladder. The species that showed highest density on the ladder, the majority migratory, were moderately, or only sl (more) ightly, abundant downstream. Among the most abundant species downstream, only one, non-migratory, was recorded in the ladder. The structure presented a negative selection in relation to large migratory pimelodids that might be overcome by enlarging the scale of its design. The sampling demonstrated a moderate selection of species along the ladder and its hydraulic model proved satisfactory regarding the attraction and efficient ascent of the fishes.

Fernandez, Domingo Rodriguez; Agostinho, Angelo Antônio; Bini, Luis Mauricio

2004-08-01

12

Selection of an experimental fish ladder located at the dam of the Itaipu Binacional, Paraná River, Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available The specific selection of a weir and orifice type experimental fish ladder in the dam of the Itaipu Reservoir (Paraná River) was evaluated by samplings in the river downstream and at two points along the ladder (at heights of 10 m and 27 m) during 28 months. Among the 65 species recorded in the river (immediate downstream of the dam), 27 were captured on the ladder. The species that showed highest density on the ladder, the majority migratory, were moderately, or only slightly, abundant downstream. Among the most abundant species downstream, only one, non-migratory, was recorded in the ladder. The structure presented a negative selection in relation to large migratory pimelodids that might be overcome by enlarging the scale of its design. The sampling demonstrated a moderate selection of species along the ladder and its hydraulic model proved satisfactory regarding the attraction and efficient ascent of the fishes.A seleção específica de uma escada de peixes do tipo seqüência de tanques, com passagem de fundo (tipo weir and orifice), na barragem da hidrelétrica de Itaipu (rio Paraná), foi avaliada através de amostragens no rio a jusante (amostragem trimestral em 1997) e em dois pontos ao longo da escada (10 e 27m de altura; nov/94 a jan/97 e nov/94 a fev/97, respectivamente). Das 65 espécies registradas no rio imediatamente a jusante da barragem, 27 foram capturadas na escada. As espécies com maior densidade na escada, em sua maioria migradoras, tiveram abundância moderada ou baixa a jusante. Entre as mais abundantes a jusante, apenas uma, não migradora, foi registrada na escada. A escada apresentou seleção negativa aos grandes pimelodídeos migradores que pode ser superada com a ampliação na escala do projeto. As amostragens evidenciaram baixa seletividade específica ao longo da escada, sendo seu modelo hidráulico satisfatório na atração e eficiente na ascensão de peixes.

Domingo Rodriguez Fernandez; Angelo Antônio Agostinho; Luis Mauricio Bini

2004-01-01

13

Utilization of the fish ladder at the Engenheiro Sergio Motta Dam, Brazil, by long distance migrating potamodromous species  

Directory of Open Access Journals (Sweden)

Full Text Available Utilization of the fish ladder installed at the Engenheiro Sergio Motta Dam (also known as Porto Primavera) on the Paraná River, Southern Brazil, by long-distance migrating potamodromous species (sampling Protocol I), and ascending and descending movements (Protocol II) were evaluated. Three pools along the fish ladder (designated as lower, middle, and upper) were sampled monthly between December, 2004 and March, 2005 to determine the abundance of species in the ladder. The ascending and descending movements of the species in the ladder were also analyzed in the same period. In the samples for both protocols, 37 species representing 17 families and 5 orders (Characiformes, Siluriformes, Perciformes, Gymnotiformes, and Myliobatiformes) were recorded. Characiformes were represented by 21 species. Long- distance migratory species (11 species) predominated in the ladder (60% of the total number of individuals), with high abundance of Rhinelepis aspera (5645 individuals). For protocol I, mean abundance varied greatly among the months and pools, with lowest values in December and March for all pools, and highest in January for the lower pool due to high capture of R. aspera. Fish abundance declined from the lower to the upper pool, especially for R. aspera and Rhaphiodon vulpinus. For Protocol II, 17 species were recorded ascending the ladder, where Astyanax altiparanae and Leporinus friderici were the most abundant species (684 and 111 individuals, respectively). However, 18 species showed descending movements, with high captures of Metynnis maculatus and A. altiparanae (339 and 319 individuals, respectively). Twelve species (52%) moved in both directions, and among the seven migratory species sampled, four were recorded ascending and descending, and three species only ascending the ladder. The fish ladder appears to selectively favor species with high swimming capabilities. A discussion is presented on the requirements for future research on attraction to the fish ladder entrance, downstream movements, fish utilization of the ladder, and impacts on spawning and rearing habitat both upstream and downstream of the dam.A utilização da escada para peixes instalada na barragem Engenheiro Sergio Motta (também conhecida como Porto Primavera) no rio Paraná, no sudeste do Brasil, por espécies potamódromas de longa distância (protocolo I) e os movimentos ascendentes e descendentes (protocolo II) foram avaliados. Três tanques ao longo da escada para peixes (denominados como foz, meio e tomada) foram amostrados mensalmente entre dezembro de 2004 a março de 2005 para avaliar a abundância de espécies na escada. Os movimentos ascendentes e descendentes das espécies na escada foram analisados no mesmo período. Nas amostragens relativas aos protocolo I e II, foram capturadas 37 espécies representando 17 famílias e cinco ordens (Characiformes, Siluriformes, Perciformes, Gymnotiformes e Myliobatiformes). Os Characiformes foram representados por 21 espécies. Espécies migradoras de longa distância (11 espécies) predominaram (60% do total), com maior abundância de Rhinelepis aspera (5645 indivíduos). A abundância média variou entre os meses e tanques para o protocolo I, com menores valores em dezembro e março para todos os tanques, e maiores em janeiro no tanque foz, devido a maior captura de R. aspera. A abundância de peixes diminuiu do tanque foz para o tanque tomada, especialmente para R. aspera e Rhaphiodon vulpinus. Nas capturas relativas ao protocolo II, foram capturadas 17 espécies ascendendo a escada: Astyanax altiparanae e Leporinus friderici foram as mais abundantes (com 684 e 111 indivíduos, respectivamente). Entretanto, 18 espécies apresentaram movimentos descendentes, com elevadas capturas de Metynnis maculatus e A. altiparanae (339 e 319 indivíduos, respectivamente). Doze espécies apresentaram movimentos ascendentes e descendentes na escada, e das sete espécies migradoras amostradas, quatro apresentaram movimentos para cima e para baixo, e três espécies somente subiram. Esta esca

Sérgio Makrakis; Maristela Cavicchioli Makrakis; Ricardo Luiz Wagner; João Henrique Pinheiro Dias; Luiz Carlos Gomes

2007-01-01

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Fish passage post-construction issues: analysis of distribution, attraction and passage efficiency metrics at the Baguari Dam fish ladder to approach the problem  

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Full Text Available Fish passages are considered the oldest management tool used to minimize the impact of blocking fish migratory routes by hydroelectric power plants. However, fish passages are being installed without specific criteria in Brazil, with severe consequences to the conservation of the local fish fauna. Therefore, basic data gathered for fish passages already constructed could contribute to define operational rules, in addition to offer subsidies to decision-making and design of future facilities. Thus, the fish ladder of Baguari Dam was evaluated regarding temporal distribution, attraction, and ascension of the local fish fauna. A total of 20 fish samples were conducted immediately downstream of the dam and inside the fish ladder, from January 2010 to June 2011. Seasonal variation in fish abundance and richness was registered below the dam and inside the passage, with higher number of migratory fish in the reproductive season (Kruskall-Wallis, p = 0.04 and p = 0.05). Furthermore, higher concentration of migratory allochthonous and non-migratory species was registered for the spill bay (Wilcoxon, p = 0.009 and p = 0.006) compared to the tailrace, where the fish ladder entrance is located. This result suggests low efficiency of the attraction system of the mechanism during the reproductive period. Once entering the fish ladder, migratory species apparently ascend the facility due to the similar distribution throughout different stretches. Generally, the results showed that an operational rule for the Baguari Dam fish ladder should consider running the facility only during the reproductive period, unless the objectives of the passage are well defined. The attraction system must be more precisely evaluated, using technologies such as radiotelemetry. Similarly, fish ascension also should be better analyzed to evaluate the time spent to ascend and its influence in the reproductive biology of the species using the ladder. Pit-tag system could be used to approach this analysis. It is expected that the discussion of these results would be useful for companies of the energy sector and for environmental agencies in Brazil, subsidizing decisions related to the management of fish passages already installed and to the construction of new facilities in the country.As passagens ou sistemas de transposição de peixes são uma das ferramentas de manejo mais antigas utilizadas para minimizar o impacto do bloqueio de rota migratória de peixes pela implantação de barragens. Todavia, sua implantação tem sido realizada sem muito critério no Brasil, trazendo consequências muitas vezes graves à conservação da ictiofauna local. Por essa razão, dados básicos obtidos para as passagens de peixes em funcionamento podem contribuir para definição de sua regra operativa, além de subsidiar tomada de decisões e o design de futuros sistemas. Assim, a escada de peixes da UHE Baguari foi avaliada quanto à distribuição temporal, atração e subida da ictiofauna local. Foram realizadas 20 amostragens a jusante da barragem e no interior da escada de peixes entre janeiro de 2010 a junho de 2011. Observou-se variação sazonal na distribuição e riqueza de espécies de peixes a jusante da barragem e dentro da escada, sendo que as espécies migradoras foram registradas em maior abundância durante o período reprodutivo (Kruskall-Wallis, p = 0,04 e p = 0,05). Além disso, nesse mesmo período, maior concentração das espécies migradoras alóctones e não migradoras foi registrada para a bacia de dissipação da barragem (Wilcoxon, p = 0,009 e p = 0,006) quando comparado ao canal de fuga, local onde se encontra a entrada da escada. Isso sugere que a eficiência do sistema de atração do mecanismo não seja a esperada nesse período. Uma vez dentro da escada, aparentemente as espécies migradoras percorrem todo o mecanismo, distribuindo-se de forma similar ao longo de sua extensão. Em geral, os resultados obtidos demonstram que, aparentemente, a regra operativa da escada deva indicar seu funcionamento apenas no período reprod

Luiz Gustavo Martins da Silva; Lorena Bettinelli Nogueira; Bruno Pereira Maia; Lucas Borges de Resende

2012-01-01

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Deficient downstream passage through fish ladders: the case of Peixe Angical Dam, Tocantins River, Brazil  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese A passagem descendente de peixes em mecanismos de transposição permanece pouco investigada na América do Sul. Inspirado nessa falha, o presente estudo monitorou a escada de peixes instalada na barragem da UHE Peixe Angical, alto rio Tocantins, entre setembro de 2009 e agosto de 2010. Para investigar a extensão da passagem rio abaixo, a fauna de peixes foi amostrada mensalmente em (i) locais acima e abaixo da barragem, e (ii) dentro da escada. Para identificar corretam (more) ente movimentos ascendentes e descendentes dentro da escada, o mecanismo permaneceu aberto (fluxo permanente de água), mas uma tela impediu a passagem completa dos peixes em ambas as direções. Os resultados indicam que a escada é restritiva ao movimento dos peixes em ambos os sentidos, considerando que poucas espécies tiveram acesso ao mecanismo (de um total de 119 espécies na área, apenas 31 ocorreram na escada). O monitoramento revelou, entretanto, que a passagem descendente é consideravelmente mais limitada; apenas 18 espécies foram registradas descendo o mecanismo. Além disso, poucos peixes tentaram descer a escada ao longo do ano; de todos os peixes capturados na escada (n = 17,335), apenas 4% desempenhava movimentos descendentes. Espécies executando apenas movimentos descendentes tiveram baixa abundância ou foram infrequentes, e apenas quatro somaram quase toda captura. Enfatizamos que diversas espécies executaram movimentos exclusivos rio acima, ou apresentaram elevado fluxo de indivíduos subindo a escada. Consequentemente, a razão entre o número de peixes subindo e descendo o mecanismo (peixes/m²) apresentou valores positivos e elevados ao longo do ano (644:1 em média, considerando todas as espécies); espécies migradoras apresentaram valores ainda maiores (1069:1). A escada é, portanto, criticamente deficiente para a descida de peixes migradores e não-migradores, facultando apenas movimentos unilaterais rio acima. Concluímos que a escada de Peixe Angical não desempenha papel conservacionista, com risco de causar impactos sobre populações de peixes e complicar esforços alternativos de conservação. Abstract in english Downstream passage through fish ladders and other facilities remains largely uninvestigated in South America. In view of this concern, we monitored ascending and descending fish movements through the fish ladder at Peixe Angical Dam, upper Tocantins River, Brazil, between September 2009 and August 2010. To investigate the extent of downstream passage, the fish fauna was sampled monthly (i) at sites upstream and downstream from the dam and (ii) inside the ladder. To distin (more) guish between ascending and descending movements, the fish ladder remained open (permanent water flow), but a screen blocked the complete passage of fish in both directions. The results of the study indicated that the ladder restricts fish movements in both directions. Few species were found to use the ladder (31 out of 119 species recorded in the area). Moreover, monitoring revealed that downstream passage is even more limited. Only 18 species were recorded moving downstream. In addition, few fish attempted to move downstream during the year; of all fish captured in the ladder (n = 17,335), only 4% were descending. Species performing exclusive downstream movements were numerically rare or infrequent. Most downstream captures involved only four species. We emphasize that several species performed one-way upstream movements or showed a high density of ascending fish. Consequently, the numerical ratio between ascending and descending fish (ind./m²) showed high positive values throughout the year (644:1 on average, considering all species); migratory species showed higher ratios (1069:1). The results of the study show that the facility fails to support the downstream passage of migratory and non-migratory fishes. We conclude that the fish ladder at Peixe Angical Dam does not play a conservation role and may complicate alternative conservation efforts.

Pelicice, Fernando Mayer; Agostinho, Carlos Sérgio

2012-10-01

16

Deficient downstream passage through fish ladders: the case of Peixe Angical Dam, Tocantins River, Brazil  

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Full Text Available Downstream passage through fish ladders and other facilities remains largely uninvestigated in South America. In view of this concern, we monitored ascending and descending fish movements through the fish ladder at Peixe Angical Dam, upper Tocantins River, Brazil, between September 2009 and August 2010. To investigate the extent of downstream passage, the fish fauna was sampled monthly (i) at sites upstream and downstream from the dam and (ii) inside the ladder. To distinguish between ascending and descending movements, the fish ladder remained open (permanent water flow), but a screen blocked the complete passage of fish in both directions. The results of the study indicated that the ladder restricts fish movements in both directions. Few species were found to use the ladder (31 out of 119 species recorded in the area). Moreover, monitoring revealed that downstream passage is even more limited. Only 18 species were recorded moving downstream. In addition, few fish attempted to move downstream during the year; of all fish captured in the ladder (n = 17,335), only 4% were descending. Species performing exclusive downstream movements were numerically rare or infrequent. Most downstream captures involved only four species. We emphasize that several species performed one-way upstream movements or showed a high density of ascending fish. Consequently, the numerical ratio between ascending and descending fish (ind./m²) showed high positive values throughout the year (644:1 on average, considering all species); migratory species showed higher ratios (1069:1). The results of the study show that the facility fails to support the downstream passage of migratory and non-migratory fishes. We conclude that the fish ladder at Peixe Angical Dam does not play a conservation role and may complicate alternative conservation efforts.A passagem descendente de peixes em mecanismos de transposição permanece pouco investigada na América do Sul. Inspirado nessa falha, o presente estudo monitorou a escada de peixes instalada na barragem da UHE Peixe Angical, alto rio Tocantins, entre setembro de 2009 e agosto de 2010. Para investigar a extensão da passagem rio abaixo, a fauna de peixes foi amostrada mensalmente em (i) locais acima e abaixo da barragem, e (ii) dentro da escada. Para identificar corretamente movimentos ascendentes e descendentes dentro da escada, o mecanismo permaneceu aberto (fluxo permanente de água), mas uma tela impediu a passagem completa dos peixes em ambas as direções. Os resultados indicam que a escada é restritiva ao movimento dos peixes em ambos os sentidos, considerando que poucas espécies tiveram acesso ao mecanismo (de um total de 119 espécies na área, apenas 31 ocorreram na escada). O monitoramento revelou, entretanto, que a passagem descendente é consideravelmente mais limitada; apenas 18 espécies foram registradas descendo o mecanismo. Além disso, poucos peixes tentaram descer a escada ao longo do ano; de todos os peixes capturados na escada (n = 17,335), apenas 4% desempenhava movimentos descendentes. Espécies executando apenas movimentos descendentes tiveram baixa abundância ou foram infrequentes, e apenas quatro somaram quase toda captura. Enfatizamos que diversas espécies executaram movimentos exclusivos rio acima, ou apresentaram elevado fluxo de indivíduos subindo a escada. Consequentemente, a razão entre o número de peixes subindo e descendo o mecanismo (peixes/m²) apresentou valores positivos e elevados ao longo do ano (644:1 em média, considerando todas as espécies); espécies migradoras apresentaram valores ainda maiores (1069:1). A escada é, portanto, criticamente deficiente para a descida de peixes migradores e não-migradores, facultando apenas movimentos unilaterais rio acima. Concluímos que a escada de Peixe Angical não desempenha papel conservacionista, com risco de causar impactos sobre populações de peixes e complicar esforços alternativos de conservação.

Fernando Mayer Pelicice; Carlos Sérgio Agostinho

2012-01-01

17

Influence of seasonal, diel, lunar, and other environmental factors on upstream fish passage in the igarapava fish ladder, Brazil  

Science.gov (United States)

Upstream fish passage was evaluated during 12 months in the vertical-slot Igarapava Fish Ladder constructed around Igarapava Dam, in the heavily dammed Grande River, Southeast Brazil. A video monitoring system was used to observe 61,621 fish that passed the ladder, of which 93.5% were identified to 15 taxa. Among the migratory species, the most abundant were Pimelodus maculatus (33.6% of all fish), Leporinus octofasciatus (31.4%), Leporinus friderici (4.5%), and Prochilodus lineatus (3.1%). Seven taxa were classified as nonmigratory, and of these taxa, the small Bryconamericus stramineus was the most abundant (12.7%) of all fishes. Passage of the 'nonmigratory' taxa upstream in the ladder shows they are migratory in this system and have a strong behavioural drive to move to upstream habitat. Passage of most taxa had a strong seasonal pattern. While some species passed primarily during the day, others showed a distinct nocturnal pattern. Lunar phase and water temperature also strongly affected passage of some taxa. Rainfall and dam discharge had a small or null influence on most taxa; perhaps due to the fairly small catchment area of the reservoir and the highly regulated discharge at Igarapava Dam. ?? 2009 John Wiley & Sons A/S.

Bizzotto, P. M.; Godinho, A. L.; Vono, V.; Kynard, B.; Godinho, H. P.

2009-01-01

18

Fish ladder of Lajeado Dam: migrations on one-way routes?  

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Full Text Available Fish ladders are generally conceived to reestablish connectivity among critical habitats for migratory species, thus mitigating the impacts of the blockage of migration routes by dams. If this management tool is to be meaningful for conserving fish species, it must provide a fully permeable connection and assure both upward and downward movements. However, because reservoirs have very different hydrodynamics than the original river, it is expected that, at least in the inner area, they may constitute an additional barrier to this movement, especially for descending fish. Thus, the present study sought to determine if migratory fish and their offspring disperse downstream from the dam after ascending a ladder and spawning in the upper reaches of a basin. To achieve this purpose, we evaluated the limitation imposed by lentic areas to the descent of eggs, larvae and adults of migratory species; we also determined the abundance and composition of larvae present in the plankton near the dam, and compared the intensity of the upward and downward movements of adult fish. Samples of ichthyoplankton were taken upriver, inside the reservoir, in the river downstream from the dam, and in the forebay of the Lajeado Dam on the Tocantins River (Luis Eduardo Magalhães Hydroelectric Plant), from October, 1999 through September, 2004. The densities of fish ascending and descending the ladder were determined experimentally on eight occasions, from June, 2004 to March, 2005. Due to difficulties in identifying the true fish origin (up or down) in the environments connected by the fish passage system, the evaluation of the distribution of migratory fish in reservoirs was based on the landings of the commercial fishery conducted along the Itaipu Reservoir during the four years preceding (2001 through 2003) the construction of the lateral channel (fish-passage mechanism). Fish eggs and larvae drifting down the Tocantins River did not appear in samples taken in the lower half of the reservoir; those found in water flowing through the spillways, turbines or fish ladder of Lajeado Dam belonged essentially to non-migratory clupeids that spawn in the inner part of the reservoir. In addition, results showed that in a reservoir with no fish-passage mechanism, migrants select habitats that still maintain riverine characteristics, in the upper parts of the impounded area. The downward movements are negligible compared to those upward, in the experiments conducted in the fish ladder. It is concluded, therefore, that the Lajeado fish ladder, and possibly those at other dams, is essentially a one-way route that promotes upstream movements of migrants, without the necessary return of adults or their offspring. Thus, the low permeability of the connections provided by these management tools can drastically increase the level of environmental impact that they were actually intended to reduce.Escadas de peixes são geralmente concebidas para restabelecer a conectividade entre habitats críticos de espécies migradoras, atenuando os impactos da interceptação de rotas de migração por barragens. Para que esse instrumento de manejo tenha significado na conservação das espécies é necessário que a permeabilidade dessa conexão seja ampla e que os movimentos ascendentes e descendentes sejam assegurados. Entretanto, como os reservatórios têm uma hidrodinâmica muito distinta do rio original, postula-se que, pelo menos em sua área mais interna ele possa se constituir em uma barreira adicional a esses movimentos, especialmente os descendentes. Assim, esse trabalho busca avaliar se peixes migradores e sua prole dispersam para os trechos abaixo da barragem após a transporem e desovar nos trechos altos da bacia. Com esse propósito, foi avaliado o grau de restrição oferecido pelas áreas lênticas de reservatórios aos deslocamentos descendentes de ovos, larvas e adultos de espécies migradoras, identificada a abundância e composição das larvas presentes no plâncton das imediações da barragem e comparada a intensidade dos movimento

Angelo Antônio Agostinho; Elineide Eugênio Marques; Carlos Sérgio Agostinho; Deusimar Augusto de Almeida; Rafael José de Oliveira; Jussiclene Rodrigues Bezerra de Melo

2007-01-01

19

Movements through a fish ladder: temporal patterns and motivations to move upstream  

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Full Text Available Fish passages are constructed with the aim of reestablishing connectivity between critical habitats, in order to sustain those species that move over a large area during their lives. The upstream movements of most of the known migratory species are made for purposes of reproduction (adults) or dispersal (juveniles). The present study was conducted at the ladder constructed at Lajeado Dam (Luis Eduardo Magalhães Hydroelectric Power), on the Tocantins River. The objective was to assess whether there is a temporal pattern in the abundance of fish below the dam and in the ladder, that correlates with their breeding seasons. Additionally, it was examined whether reproduction is the predominant motivation of the shoals of fish that ascend the ladder. Samples were taken monthly from November, 2002 through October, 2003, downriver from the dam with gillnets, and in the resting pools of the fish ladder with cast nets. The analysis of seasonality in the aggregation of the shoals was based on the temporal variations in abundance and species richness. The possibility of a reproductive motivation for ascending the ladder was inferred from the frequency of the stages of gonadal development. However, during the entire study period we observed a high frequency of individuals with gonads in the pre-vitellogenic stage for all analyzed species, both downriver from the dam (97%) and in the fish ladder (98%). These findings suggest that there was no reproductive motivation for the aggregation of the fish downstream and for their entry into the ladder. On the other hand, the dominance of these stages downriver suggests that the spawning habitats are distant, and that the upstream movements occur for other reasons such as dispersal and search for more appropriate habitats for feeding and growth. The entrance into the ladder resulted more from rheophilic behavior, which is more pronounced in migratory species, than from an endogenous motivation linked to reproductive migration.Os mecanismos de transposição de peixes em barragens visam restabelecer a conectividade entre habitats críticos à manutenção para as espécies que tenham uma ampla área de vida. Os movimentos ascendentes da maioria das espécies migradoras conhecidas são realizados por motivação reprodutiva (adultos) ou dispersiva (juvenis). Neste contexto, o presente estudo tem como objetivo avaliar se existe um padrão temporal na abundância de peixes a jusante da barragem e na escada da UHE Lajeado (UHE Luis Eduardo Magalhães, rio Tocantins) que segue a sazonalidade reprodutiva. Adicionalmente, busca avaliar se reprodução é a motivação predominante dos cardumes que ascendem a escada. Para isto, as amostragens foram realizadas mensalmente de novembro de 2002 a outubro de 2003 a jusante da barragem, com o uso de redes de espera, e nos tanques de descanso da escada, com tarrafas. A análise da sazonalidade na agregação dos cardumes foi baseada nas variações temporais de abundância e riqueza de espécies, enquanto a motivação reprodutiva para a ascensão foi inferida a partir da freqüência dos estádios de maturação gonadal. Entretanto, durante todo o período foi constatada uma elevada freqüência de indivíduos com gônadas em fase pré-vitelogênica em todas as espécies analisadas, tanto a jusante da barragem (97%) como na escada (98%), sugerindo a inexistência de motivação reprodutiva para a agregação dos peixes a jusante e seus ingressos na escada. Por outro lado, o fato destes estádios dominarem as capturas também a jusante sugere que os locais de desova estão distantes, e que os deslocamentos ascendentes ocorrem por outras razões, como dispersão natural e busca de habitats mais apropriados para alimentação e crescimento. Assim, o ingresso na escada decorreu mais do comportamento reofílico, exacerbado nas espécies migradoras, que de uma motivação endógena ligada à migração reprodutiva.

Carlos Sérgio Agostinho; Celiana Ribeiro Pereira; Rafael José de Oliveira; Iriene Siqueira Freitas; Elineide Eugênio Marques

2007-01-01

20

Movements through a fish ladder: temporal patterns and motivations to move upstream  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Os mecanismos de transposição de peixes em barragens visam restabelecer a conectividade entre habitats críticos à manutenção para as espécies que tenham uma ampla área de vida. Os movimentos ascendentes da maioria das espécies migradoras conhecidas são realizados por motivação reprodutiva (adultos) ou dispersiva (juvenis). Neste contexto, o presente estudo tem como objetivo avaliar se existe um padrão temporal na abundância de peixes a jusante da barragem e (more) na escada da UHE Lajeado (UHE Luis Eduardo Magalhães, rio Tocantins) que segue a sazonalidade reprodutiva. Adicionalmente, busca avaliar se reprodução é a motivação predominante dos cardumes que ascendem a escada. Para isto, as amostragens foram realizadas mensalmente de novembro de 2002 a outubro de 2003 a jusante da barragem, com o uso de redes de espera, e nos tanques de descanso da escada, com tarrafas. A análise da sazonalidade na agregação dos cardumes foi baseada nas variações temporais de abundância e riqueza de espécies, enquanto a motivação reprodutiva para a ascensão foi inferida a partir da freqüência dos estádios de maturação gonadal. Entretanto, durante todo o período foi constatada uma elevada freqüência de indivíduos com gônadas em fase pré-vitelogênica em todas as espécies analisadas, tanto a jusante da barragem (97%) como na escada (98%), sugerindo a inexistência de motivação reprodutiva para a agregação dos peixes a jusante e seus ingressos na escada. Por outro lado, o fato destes estádios dominarem as capturas também a jusante sugere que os locais de desova estão distantes, e que os deslocamentos ascendentes ocorrem por outras razões, como dispersão natural e busca de habitats mais apropriados para alimentação e crescimento. Assim, o ingresso na escada decorreu mais do comportamento reofílico, exacerbado nas espécies migradoras, que de uma motivação endógena ligada à migração reprodutiva. Abstract in english Fish passages are constructed with the aim of reestablishing connectivity between critical habitats, in order to sustain those species that move over a large area during their lives. The upstream movements of most of the known migratory species are made for purposes of reproduction (adults) or dispersal (juveniles). The present study was conducted at the ladder constructed at Lajeado Dam (Luis Eduardo Magalhães Hydroelectric Power), on the Tocantins River. The objective (more) was to assess whether there is a temporal pattern in the abundance of fish below the dam and in the ladder, that correlates with their breeding seasons. Additionally, it was examined whether reproduction is the predominant motivation of the shoals of fish that ascend the ladder. Samples were taken monthly from November, 2002 through October, 2003, downriver from the dam with gillnets, and in the resting pools of the fish ladder with cast nets. The analysis of seasonality in the aggregation of the shoals was based on the temporal variations in abundance and species richness. The possibility of a reproductive motivation for ascending the ladder was inferred from the frequency of the stages of gonadal development. However, during the entire study period we observed a high frequency of individuals with gonads in the pre-vitellogenic stage for all analyzed species, both downriver from the dam (97%) and in the fish ladder (98%). These findings suggest that there was no reproductive motivation for the aggregation of the fish downstream and for their entry into the ladder. On the other hand, the dominance of these stages downriver suggests that the spawning habitats are distant, and that the upstream movements occur for other reasons such as dispersal and search for more appropriate habitats for feeding and growth. The entrance into the ladder resulted more from rheophilic behavior, which is more pronounced in migratory species, than from an endogenous motivation linked to reproductive migration.

Agostinho, Carlos Sérgio; Pereira, Celiana Ribeiro; Oliveira, Rafael José de; Freitas, Iriene Siqueira; Marques, Elineide Eugênio

2007-01-01

 
 
 
 
21

Design of Dual Bandpass and Bandreject LC Ladder Filters  

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Full Text Available This paper deals with the design of two-passband bandpass and two-stopband bandreject LC ladder filters. The design method is based on the special dual frequency transformation that transforms normalized lowpass to either bandpass with two passbands or to bandreject with two stopbands that are specified by four cutoff frequencies. The paper shows analytical solution relating these four cutoff frequencies to parameters of dual frequency transformation. It enables a direct computation of dual band LC filter elements from a normalized lowpass filter by means of simple relations. These relations have been implemented in the mathematical program Maple (TM) as new user functions. They are supposed to be used as an enhancement of Syntfil package which is intended for analog filter design in program Maple. Specific application is shown on an example of the two-passband bandpass LC filter design.

J. Bicak; J. Hospodka

2006-01-01

22

Fish passage post-construction issues: analysis of distribution, attraction and passage efficiency metrics at the Baguari Dam fish ladder to approach the problem  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese As passagens ou sistemas de transposição de peixes são uma das ferramentas de manejo mais antigas utilizadas para minimizar o impacto do bloqueio de rota migratória de peixes pela implantação de barragens. Todavia, sua implantação tem sido realizada sem muito critério no Brasil, trazendo consequências muitas vezes graves à conservação da ictiofauna local. Por essa razão, dados básicos obtidos para as passagens de peixes em funcionamento podem contribuir par (more) a definição de sua regra operativa, além de subsidiar tomada de decisões e o design de futuros sistemas. Assim, a escada de peixes da UHE Baguari foi avaliada quanto à distribuição temporal, atração e subida da ictiofauna local. Foram realizadas 20 amostragens a jusante da barragem e no interior da escada de peixes entre janeiro de 2010 a junho de 2011. Observou-se variação sazonal na distribuição e riqueza de espécies de peixes a jusante da barragem e dentro da escada, sendo que as espécies migradoras foram registradas em maior abundância durante o período reprodutivo (Kruskall-Wallis, p = 0,04 e p = 0,05). Além disso, nesse mesmo período, maior concentração das espécies migradoras alóctones e não migradoras foi registrada para a bacia de dissipação da barragem (Wilcoxon, p = 0,009 e p = 0,006) quando comparado ao canal de fuga, local onde se encontra a entrada da escada. Isso sugere que a eficiência do sistema de atração do mecanismo não seja a esperada nesse período. Uma vez dentro da escada, aparentemente as espécies migradoras percorrem todo o mecanismo, distribuindo-se de forma similar ao longo de sua extensão. Em geral, os resultados obtidos demonstram que, aparentemente, a regra operativa da escada deva indicar seu funcionamento apenas no período reprodutivo, ao menos até que os objetivos da transposição de peixes na UHE Baguari sejam de fato definidos. Já o sistema de atração da escada deverá ser avaliado de forma mais precisa, utilizando-se tecnologias como radiotelemetria. Da mesma forma, a subida dos peixes pela escada deve ser melhor analisada para se avaliar o tempo gasto e a influência desse período sobre a biologia reprodutiva dos peixes. O sistema de Pit-tag pode ser utilizado para realizar essa análise. Espera-se que a discussão das informações obtidas no presente trabalho possa ser utilizada pelas empresas do setor elétrico e órgãos ambientais para subsidiar decisões relacionadas ao manejo de sistemas de transposição de peixes já em funcionamento e à construção de novos empreendimentos. Abstract in english Fish passages are considered the oldest management tool used to minimize the impact of blocking fish migratory routes by hydroelectric power plants. However, fish passages are being installed without specific criteria in Brazil, with severe consequences to the conservation of the local fish fauna. Therefore, basic data gathered for fish passages already constructed could contribute to define operational rules, in addition to offer subsidies to decision-making and design o (more) f future facilities. Thus, the fish ladder of Baguari Dam was evaluated regarding temporal distribution, attraction, and ascension of the local fish fauna. A total of 20 fish samples were conducted immediately downstream of the dam and inside the fish ladder, from January 2010 to June 2011. Seasonal variation in fish abundance and richness was registered below the dam and inside the passage, with higher number of migratory fish in the reproductive season (Kruskall-Wallis, p = 0.04 and p = 0.05). Furthermore, higher concentration of migratory allochthonous and non-migratory species was registered for the spill bay (Wilcoxon, p = 0.009 and p = 0.006) compared to the tailrace, where the fish ladder entrance is located. This result suggests low efficiency of the attraction system of the mechanism during the reproductive period. Once entering the fish ladder, migratory species apparently ascend the facility due to the similar distribution throughout differen

Silva, Luiz Gustavo Martins da; Nogueira, Lorena Bettinelli; Maia, Bruno Pereira; Resende, Lucas Borges de

2012-10-01

23

Effect of an ice harbor type fish ladder for salmon running upward in a river; Ice harbor gata gyodo no sake no sojo koka  

Energy Technology Data Exchange (ETDEWEB)

An ice harbor type fish ladder is constructed at a water intake dam for Hokkaido Electric Power Co.`s Ran-etu Power Station, to facilitate salmon to run upward in the river. It is characterized by the partition wall with increased height at the center to prevent overflow there, and a large bore provided at the bottom of each of the overflow sections across the wall. This design is to stabilize flow conditions in the ladder, providing salmon with a still section in the ladder pool downstream of the non-overflow section, even when water flow conditions greatly change. Salmon can move against the flow, jumping over the overflow section or passing through the bore, depending on its ability. Salmon runs against flow in the ladder in daytime, from 12 to 18, mostly jumping over the overflow section into the upstream pool. Salmon takes a rest at intervals of 6 to 8 stages, when the ladder is sloped at around 1/8, and the pool at each stage provides a good resting place. Depth of overflow is adequate at around 15m. The bore provides a better resting place in the pool, when provided at the center of the overflow section. 10 refs., 13 figs., 5 tabs.

Onodera, O.; Misawa, H.; Kamifuji, K. [Hokkaido Electric Power Co. Inc., Sapporo (Japan)

1998-07-05

24

Utilization of the fish ladder at the Engenheiro Sergio Motta Dam, Brazil, by long distance migrating potamodromous species  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese A utilização da escada para peixes instalada na barragem Engenheiro Sergio Motta (também conhecida como Porto Primavera) no rio Paraná, no sudeste do Brasil, por espécies potamódromas de longa distância (protocolo I) e os movimentos ascendentes e descendentes (protocolo II) foram avaliados. Três tanques ao longo da escada para peixes (denominados como foz, meio e tomada) foram amostrados mensalmente entre dezembro de 2004 a março de 2005 para avaliar a abundânci (more) a de espécies na escada. Os movimentos ascendentes e descendentes das espécies na escada foram analisados no mesmo período. Nas amostragens relativas aos protocolo I e II, foram capturadas 37 espécies representando 17 famílias e cinco ordens (Characiformes, Siluriformes, Perciformes, Gymnotiformes e Myliobatiformes). Os Characiformes foram representados por 21 espécies. Espécies migradoras de longa distância (11 espécies) predominaram (60% do total), com maior abundância de Rhinelepis aspera (5645 indivíduos). A abundância média variou entre os meses e tanques para o protocolo I, com menores valores em dezembro e março para todos os tanques, e maiores em janeiro no tanque foz, devido a maior captura de R. aspera. A abundância de peixes diminuiu do tanque foz para o tanque tomada, especialmente para R. aspera e Rhaphiodon vulpinus. Nas capturas relativas ao protocolo II, foram capturadas 17 espécies ascendendo a escada: Astyanax altiparanae e Leporinus friderici foram as mais abundantes (com 684 e 111 indivíduos, respectivamente). Entretanto, 18 espécies apresentaram movimentos descendentes, com elevadas capturas de Metynnis maculatus e A. altiparanae (339 e 319 indivíduos, respectivamente). Doze espécies apresentaram movimentos ascendentes e descendentes na escada, e das sete espécies migradoras amostradas, quatro apresentaram movimentos para cima e para baixo, e três espécies somente subiram. Esta escada para peixes parece favorecer seletivamente espécies com elevada capacidade de natação. As necessidades de pesquisas futuras para elucidar sobre a atratividade da escada, movimentos descendentes, utilização da escada pelos peixes e os impactos sobre as áreas de reprodução e criadouros, ambos a montante e jusante da barragem, são discutidos. Abstract in english Utilization of the fish ladder installed at the Engenheiro Sergio Motta Dam (also known as Porto Primavera) on the Paraná River, Southern Brazil, by long-distance migrating potamodromous species (sampling Protocol I), and ascending and descending movements (Protocol II) were evaluated. Three pools along the fish ladder (designated as lower, middle, and upper) were sampled monthly between December, 2004 and March, 2005 to determine the abundance of species in the ladder. (more) The ascending and descending movements of the species in the ladder were also analyzed in the same period. In the samples for both protocols, 37 species representing 17 families and 5 orders (Characiformes, Siluriformes, Perciformes, Gymnotiformes, and Myliobatiformes) were recorded. Characiformes were represented by 21 species. Long- distance migratory species (11 species) predominated in the ladder (60% of the total number of individuals), with high abundance of Rhinelepis aspera (5645 individuals). For protocol I, mean abundance varied greatly among the months and pools, with lowest values in December and March for all pools, and highest in January for the lower pool due to high capture of R. aspera. Fish abundance declined from the lower to the upper pool, especially for R. aspera and Rhaphiodon vulpinus. For Protocol II, 17 species were recorded ascending the ladder, where Astyanax altiparanae and Leporinus friderici were the most abundant species (684 and 111 individuals, respectively). However, 18 species showed descending movements, with high captures of Metynnis maculatus and A. altiparanae (339 and 319 individuals, respectively). Twelve species (52%) moved in both directions, and among the seven migratory species sampled, four were r

Makrakis, Sérgio; Makrakis, Maristela Cavicchioli; Wagner, Ricardo Luiz; Dias, João Henrique Pinheiro; Gomes, Luiz Carlos

2007-01-01

25

Design Equations for Silicon Detector Ladders with Heat Generated by Damage Induced Leakage Current  

UK PubMed Central (United Kingdom)

We find approximate analytical solutions to the problem of cooling a silicon detector ladder which isinternally heated by leakage current caused by radiation damage. The heat generation term has anapproximately exponential temperature dependence. Heat is removed by convection and / or conduction to aheat sink. Design equations are derived which prevent thermal runaway, and a wide range of parameter spacefor those equations is explored.1. IntroductionTemperature dependent leakage current induced by radiation damage can cause catastrophic thermalrunaway in silicon detector ladders; however, a suitable choice of ladder length and operating temperature willprevent thermal runaway during the useful detector lifetime. Radiation damage leads to both electrical failureand thermal runaway. If possible, a detector designer wants to choose ladder and cooling parameters so thedamage induced detector failure mechanism is electrical, not thermal. If the ladder length between coolingchann...

J. A. Hanlon; H. J. Ziock

26

Diel variation in the ascent of fishes up an experimental fish ladder at Itaipu Reservoir: fish size, reproductive stage and taxonomic group influences  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we evaluated the fish ascent in the experimental ladder at Itaipu Reservoir (Paraná State, Brazil), in relation to diel variation, fish size, reproductive stages and species composition. The study was carried out from October, 1995 to February, 1996 and from November, 1996 to January, 1997 at two points on the ladder (boxes at heights of 10 and 27 m). Twenty-two species were recorded, and Prochilodus lineatus, Pimelodus maculatus, Leporinus obtusidens, Schizodon borellii and Leporinus friderici accounted for 86.6 % of the total catch. Fish length did not differ between diel periods and boxes. On the other hand, fish abundance of the main species was significantly influenced by box position, reproductive stage and diel period. The higher box showed lower abundance, suggesting some selectivity in ascension. The ability to ascend the ladder did not show any relationship with reproductive migration, since non-reproductive adults comprised most of the catch. An interesting finding is that the major taxonomic groups showed specific diel preferences in ascending the ladder: Characiformes ascended the ladder predominantly during daylight, whereas Siluriformes migrated at night. These results emphasize how complex ladders are as management tools, and stress the need to acquire information on several aspects as a condition to achieve conservation goals.Nesse estudo, a transposição de peixes na escada experimental do reservatório de Itaipu (Paraná, Brasil) foi avaliada em relação à variação diária, tamanho dos peixes, estágios reprodutivos e a composição das espécies. O estudo foi conduzido de Outubro de 1995 a Fevereiro de 1996, e de Novembro de 1996 a Janeiro de 1997, em dois trechos da escada (caixas a 10 e 27 m de altura). Vinte e duas espécies foram registradas, e Prochilodus lineatus, Pimelodus maculatus, Leporinus obtusidens, Schizodon borellii e Leporinus friderici compuseram 86,6% das capturas. O tamanho dos peixes não diferiu entre os períodos do dia e caixas. Por outro lado, a abundância das principais espécies foi significativamente influenciada pela posição das caixas, estágio de reprodução e período do dia. A caixa superior tendeu a apresentar menor abundância de peixes, sugerindo certa seletividade na subida. A habilidade em ascender a escada não esteve relacionada com a migração reprodutiva, visto que adultos não-reprodutivos compuseram a maior parte das capturas. Um padrão interessante foi a preferência, apresentada pelos grandes grupos taxonômicos, por períodos específicos do dia na ascensão da escada: os Characiformes subiram a escada predominantemente durante o dia, enquanto os Siluriformes durante a noite. Esses resultados enfatizam o quão complexas são as escadas como ferramentas de manejo, e realçam a necessidade de ampliar o nível de informações sobre diversos aspectos como condição chave para que metas conservacionistas sejam alcançadas.

Domingo Rodriguez Fernandez; Angelo Antonio Agostinho; Luis Mauricio Bini; Fernando Mayer Pelicice

2007-01-01

27

Evaluation of fish passage through the Igarapé Dam fish ladder (rio Paraopeba, Brazil), using marking and recapture  

Directory of Open Access Journals (Sweden)

Full Text Available Rio Paraopeba, a tributary of rio São Francisco, has a six-meter high dam, built in 1978 to divert water to the Igarapé Thermal Power Plant. In 1994, a fish ladder was built at this dam. The results of a marking and recapture program carried out along rio Paraopeba between 1997 and 2001 are described, using information from fish community studies conducted at ten sampling stations between 1994 and 1997. These investigations showed the presence of at least 91 species in the river. During four rainy seasons between 1997 and 2000, fish were caught downstream of the dam, marked with external plastic tags, and immediately released at the same site. The objective was to evaluate fish passage through the ladder, based on recapture information from artisanal and sport fishermen. A total of 3,642 specimens were marked, adding up to a biomass of approximately 1.33 tons. Twenty-six species were used, representing 28.5% of the total recorded richness (91 species). Maximum recorded tag retention time was 10 months. Total recapture rate was 4.37% in four years, reaching 5.75% in the last period (2000-2001). Of all recaptured specimens, 14.0% were caught upstream of the dam, evidencing passage through the ladder. The specimens recaptured upstream of the dam belonged to three species: piau-verdadeiro (Leporinus obtusidens), mandi-amarelo (Pimelodus maculatus) and curimatá-pioa (Prochilodus costatus). These species showed linear home ranges of 15.4, 81.5 and 232.0 km, respectively. Most recaptures occurred immediately downstream of the dam, one of the most intensely fished stretches of rio Paraopeba.Desde 1978, o rio Paraopeba, um afluente do rio São Francisco, tem uma barragem de 6 metros de altura para desvio de água para a Usina Térmica de Igarapé. Em 1994, uma escada para peixes foi construída nessa barragem. Os resultados de um programa de marcação e recaptura realizado entre 1997 e 2001 são descritos, utilizando dados prévios de estudos das comunidades de peixes conduzidos em dez estações de amostragem entre 1994 e 1997. Estes estudos demonstraram a presença de pelo menos 91 espécies no rio Paraopeba. Durante quatro estações chuvosas entre 1997 e 2000, peixes foram capturados abaixo da barragem, marcados com marcas externas, e imediatamente soltos no mesmo ponto. O objetivo desse trabalho foi avaliar a passagem pela escada, com base nas recapturas informadas por pescadores artesanais e esportivos. No total foram marcados 3.642 indivíduos, atingindo aproximadamente 1,33 tonelada em biomassa. Vinte e seis espécies foram utilizadas, representando 28.5% da riqueza total registrada (91 espécies). O tempo máximo verificado de retenção da marca foi de 10 meses. A taxa de retorno total foi de 4,37% em quatro anos, atingindo 5,75% no último período (2000-2001). Do total recapturado, 14% ocorreram a montante da escada. As espécies recapturadas a montante foram o piau-verdadeiro (Leporinus obtusidens), mandi-amarelo (Pimelodus maculatus) e curimatá-pioa (Prochilodus costatus). Essas espécies apresentaram área de vida de 15,4, 81,5 e 232,0 km, respectivamente. O maior número de recapturas ocorreu imediatamente a jusante da barragem da UTE Igarapé, um dos locais de pesca mais intensa em todo o rio.

Carlos Bernardo Mascarenhas Alves

2007-01-01

28

Evaluation of fish passage through the Igarapé Dam fish ladder (rio Paraopeba, Brazil), using marking and recapture  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Desde 1978, o rio Paraopeba, um afluente do rio São Francisco, tem uma barragem de 6 metros de altura para desvio de água para a Usina Térmica de Igarapé. Em 1994, uma escada para peixes foi construída nessa barragem. Os resultados de um programa de marcação e recaptura realizado entre 1997 e 2001 são descritos, utilizando dados prévios de estudos das comunidades de peixes conduzidos em dez estações de amostragem entre 1994 e 1997. Estes estudos demonstraram a (more) presença de pelo menos 91 espécies no rio Paraopeba. Durante quatro estações chuvosas entre 1997 e 2000, peixes foram capturados abaixo da barragem, marcados com marcas externas, e imediatamente soltos no mesmo ponto. O objetivo desse trabalho foi avaliar a passagem pela escada, com base nas recapturas informadas por pescadores artesanais e esportivos. No total foram marcados 3.642 indivíduos, atingindo aproximadamente 1,33 tonelada em biomassa. Vinte e seis espécies foram utilizadas, representando 28.5% da riqueza total registrada (91 espécies). O tempo máximo verificado de retenção da marca foi de 10 meses. A taxa de retorno total foi de 4,37% em quatro anos, atingindo 5,75% no último período (2000-2001). Do total recapturado, 14% ocorreram a montante da escada. As espécies recapturadas a montante foram o piau-verdadeiro (Leporinus obtusidens), mandi-amarelo (Pimelodus maculatus) e curimatá-pioa (Prochilodus costatus). Essas espécies apresentaram área de vida de 15,4, 81,5 e 232,0 km, respectivamente. O maior número de recapturas ocorreu imediatamente a jusante da barragem da UTE Igarapé, um dos locais de pesca mais intensa em todo o rio. Abstract in english Rio Paraopeba, a tributary of rio São Francisco, has a six-meter high dam, built in 1978 to divert water to the Igarapé Thermal Power Plant. In 1994, a fish ladder was built at this dam. The results of a marking and recapture program carried out along rio Paraopeba between 1997 and 2001 are described, using information from fish community studies conducted at ten sampling stations between 1994 and 1997. These investigations showed the presence of at least 91 species in (more) the river. During four rainy seasons between 1997 and 2000, fish were caught downstream of the dam, marked with external plastic tags, and immediately released at the same site. The objective was to evaluate fish passage through the ladder, based on recapture information from artisanal and sport fishermen. A total of 3,642 specimens were marked, adding up to a biomass of approximately 1.33 tons. Twenty-six species were used, representing 28.5% of the total recorded richness (91 species). Maximum recorded tag retention time was 10 months. Total recapture rate was 4.37% in four years, reaching 5.75% in the last period (2000-2001). Of all recaptured specimens, 14.0% were caught upstream of the dam, evidencing passage through the ladder. The specimens recaptured upstream of the dam belonged to three species: piau-verdadeiro (Leporinus obtusidens), mandi-amarelo (Pimelodus maculatus) and curimatá-pioa (Prochilodus costatus). These species showed linear home ranges of 15.4, 81.5 and 232.0 km, respectively. Most recaptures occurred immediately downstream of the dam, one of the most intensely fished stretches of rio Paraopeba.

Alves, Carlos Bernardo Mascarenhas

2007-01-01

29

Diel variation in the ascent of fishes up an experimental fish ladder at Itaipu Reservoir: fish size, reproductive stage and taxonomic group influences  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Nesse estudo, a transposição de peixes na escada experimental do reservatório de Itaipu (Paraná, Brasil) foi avaliada em relação à variação diária, tamanho dos peixes, estágios reprodutivos e a composição das espécies. O estudo foi conduzido de Outubro de 1995 a Fevereiro de 1996, e de Novembro de 1996 a Janeiro de 1997, em dois trechos da escada (caixas a 10 e 27 m de altura). Vinte e duas espécies foram registradas, e Prochilodus lineatus, Pimelodus macul (more) atus, Leporinus obtusidens, Schizodon borellii e Leporinus friderici compuseram 86,6% das capturas. O tamanho dos peixes não diferiu entre os períodos do dia e caixas. Por outro lado, a abundância das principais espécies foi significativamente influenciada pela posição das caixas, estágio de reprodução e período do dia. A caixa superior tendeu a apresentar menor abundância de peixes, sugerindo certa seletividade na subida. A habilidade em ascender a escada não esteve relacionada com a migração reprodutiva, visto que adultos não-reprodutivos compuseram a maior parte das capturas. Um padrão interessante foi a preferência, apresentada pelos grandes grupos taxonômicos, por períodos específicos do dia na ascensão da escada: os Characiformes subiram a escada predominantemente durante o dia, enquanto os Siluriformes durante a noite. Esses resultados enfatizam o quão complexas são as escadas como ferramentas de manejo, e realçam a necessidade de ampliar o nível de informações sobre diversos aspectos como condição chave para que metas conservacionistas sejam alcançadas. Abstract in english In this study, we evaluated the fish ascent in the experimental ladder at Itaipu Reservoir (Paraná State, Brazil), in relation to diel variation, fish size, reproductive stages and species composition. The study was carried out from October, 1995 to February, 1996 and from November, 1996 to January, 1997 at two points on the ladder (boxes at heights of 10 and 27 m). Twenty-two species were recorded, and Prochilodus lineatus, Pimelodus maculatus, Leporinus obtusidens, Sch (more) izodon borellii and Leporinus friderici accounted for 86.6 % of the total catch. Fish length did not differ between diel periods and boxes. On the other hand, fish abundance of the main species was significantly influenced by box position, reproductive stage and diel period. The higher box showed lower abundance, suggesting some selectivity in ascension. The ability to ascend the ladder did not show any relationship with reproductive migration, since non-reproductive adults comprised most of the catch. An interesting finding is that the major taxonomic groups showed specific diel preferences in ascending the ladder: Characiformes ascended the ladder predominantly during daylight, whereas Siluriformes migrated at night. These results emphasize how complex ladders are as management tools, and stress the need to acquire information on several aspects as a condition to achieve conservation goals.

Fernandez, Domingo Rodriguez; Agostinho, Angelo Antonio; Bini, Luis Mauricio; Pelicice, Fernando Mayer

2007-01-01

30

Fish ladder of Lajeado Dam: migrations on one-way routes?  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Escadas de peixes são geralmente concebidas para restabelecer a conectividade entre habitats críticos de espécies migradoras, atenuando os impactos da interceptação de rotas de migração por barragens. Para que esse instrumento de manejo tenha significado na conservação das espécies é necessário que a permeabilidade dessa conexão seja ampla e que os movimentos ascendentes e descendentes sejam assegurados. Entretanto, como os reservatórios têm uma hidrodinâm (more) ica muito distinta do rio original, postula-se que, pelo menos em sua área mais interna ele possa se constituir em uma barreira adicional a esses movimentos, especialmente os descendentes. Assim, esse trabalho busca avaliar se peixes migradores e sua prole dispersam para os trechos abaixo da barragem após a transporem e desovar nos trechos altos da bacia. Com esse propósito, foi avaliado o grau de restrição oferecido pelas áreas lênticas de reservatórios aos deslocamentos descendentes de ovos, larvas e adultos de espécies migradoras, identificada a abundância e composição das larvas presentes no plâncton das imediações da barragem e comparada a intensidade dos movimentos ascendentes e descendentes de peixes. Foram realizadas amostragens de ictioplâncton a montante, no reservatório e em seu trecho a jusante, bem como nas imediações da barragem de Lajeado (rio Tocantins; UHE Luis Eduardo Magalhães) durante o período de outubro de 1999 a setembro de 2004 e determinado, experimentalmente, em oito ocasiões durante o período de junho de 2004 e março de 2005, a densidade de peixes em movimentos ascendentes e descendentes na escada de peixes desse reservatório. Já a avaliação na distribuição de peixes migradores em reservatórios foi baseada no acompanhamento dos desembarques da pesca comercial praticada ao longo do reservatório de Itaipu durante os quatro anos que precederam a construção do mecanismo de transposição atualmente existente (2001 a 2003). Os resultados obtidos demonstraram que os ovos e larvas de peixes em deriva, pelo rio Tocantins, desaparecem das amostras na metade inferior do reservatório e aqueles encontrados na água vertida ou turbinada pela barragem de Lajeado e na escada de peixes pertencem, essencialmente, a clupeídeos não migradores, com desovas nas áreas internas do reservatório. Revelam ainda que, em reservatório sem mecanismo de transposição, os peixes migradores selecionam habitats que ainda mantém características fluviais, nos segmentos superiores da área represada. Os experimentos realizados na escada revelam que os movimentos descendentes são irrelevantes quando comparados aos ascendentes. Conclui-se, portanto, que a escada de peixes de Lajeado, e possivelmente de várias outras barragens, é essencialmente uma via de mão única que promove subidas massivas de migrantes sem o almejado retorno de adultos ou de sua prole. Assim, a baixa permeabilidade das conexões proporcionadas por esses instrumentos de manejo pode aumentar drasticamente o nível do impacto ambiental para cuja atenuação ele foi concebido. Abstract in english Fish ladders are generally conceived to reestablish connectivity among critical habitats for migratory species, thus mitigating the impacts of the blockage of migration routes by dams. If this management tool is to be meaningful for conserving fish species, it must provide a fully permeable connection and assure both upward and downward movements. However, because reservoirs have very different hydrodynamics than the original river, it is expected that, at least in the in (more) ner area, they may constitute an additional barrier to this movement, especially for descending fish. Thus, the present study sought to determine if migratory fish and their offspring disperse downstream from the dam after ascending a ladder and spawning in the upper reaches of a basin. To achieve this purpose, we evaluated the limitation imposed by lentic areas to the descent of eggs, larvae and adults of migratory species; we also det

Agostinho, Angelo Antônio; Marques, Elineide Eugênio; Agostinho, Carlos Sérgio; Almeida, Deusimar Augusto de; Oliveira, Rafael José de; Melo, Jussiclene Rodrigues Bezerra de

2007-01-01

31

Comparing on site human and video counts at Igarapava fish ladder, south eastern Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available On site human observations and video images were collected and compared at the window of the Igarapava Dam fish ladder (IDFL), rio Grande , Southeastern Brazil, between March 1st and June 30th, 2004. We conducted four experiments with two humans (Observer 1 and Observer 2) observing fish passage in the IDFL window while a Sony 3CCD video camera (Observer 3) recorded fish passage at the same time. Experiments, each one hour in length, were distributed throughout the diel cycle using full spectrum lights. We identified fish species, the number of individuals for each species, and the real time that they passed. Counts from each human observer were compared to the video counts. The fish species most commonly observed in the window were - curimba (Prochilodus lineatus), mandi-amarelo (Pimelodus maculatus), piau-três-pintas (Leporinus friderici) and ferreirinha (Leporinus octofasciatus). The number of species and individuals were indistinguishable for the three observers. But, the number of species and individuals were significantly different among experiments. Thus, the three observers register the same number of species and count the same number of individuals even when these two response variables differ significantly among experiments. Based on these results, we concluded that the video count was an accurate method to assess fish passage at the IDFL.Observações in loco e vídeo filmagens foram coletadas na janela da escada de peixes da UHE Igarapava (EPUG), rio Grande, sudeste do Brasil, entre 1º de março e 30 junho de 2004. Realizaram-se quatro experimentos com dois observadores humanos (Observador 1 e Observador 2) que observaram a passagem de peixes na janela da EPUG enquanto uma vídeo câmera Sony 3CCD (Observador 3) registrou simultaneamente a passagem de peixes. Os dois observadores humanos registraram in situ a passagem de peixes no visor da escada enquanto a câmera os filmava ao mesmo tempo. Os experimentos, cada um com uma hora de duração, foram realizados durante o ciclo diário, utilizando-se iluminação de espectro completo. Registraram-se as espécies, o número de indivíduos e o horário de passagem. Os registros de cada observador humano in situ foram comparados com os dos vídeos. Consideraram-se curimba (Prochilodus lineatus), mandi-amarelo (Pimelodus maculatus), piau-três-pintas (Leporinus friderici) e ferreirinha (Leporinus octofasciatus) como espécies alvo, tendo em vista sua alta freqüência de ocorrência na escada de peixes da UHE Igarapava. O número de espécies e o número de indivíduos não foram estatisticamente diferentes entre observadores. Por outro lado, o número de espécies e o número de indivíduos que passaram pelo visor foram estatisticamente diferentes entre experimentos. Assim, demonstrou-se que os três observadores registraram o mesmo número de espécies e contaram o mesmo número de indivíduos, mesmo quando as duas variáveis diferiram significativamente entre experimentos. Concluiu-se que o sistema de vídeo imagem constitui um método eficaz para avaliação da passagem de peixes na escada de peixes de Igarapava.

Mark D. Bowen; Simone Marques; Luiz G. M. Silva; Volney Vono; Hugo P. Godinho

2006-01-01

32

Comparing on site human and video counts at Igarapava fish ladder, south eastern Brazil  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Observações in loco e vídeo filmagens foram coletadas na janela da escada de peixes da UHE Igarapava (EPUG), rio Grande, sudeste do Brasil, entre 1º de março e 30 junho de 2004. Realizaram-se quatro experimentos com dois observadores humanos (Observador 1 e Observador 2) que observaram a passagem de peixes na janela da EPUG enquanto uma vídeo câmera Sony 3CCD (Observador 3) registrou simultaneamente a passagem de peixes. Os dois observadores humanos registraram in (more) situ a passagem de peixes no visor da escada enquanto a câmera os filmava ao mesmo tempo. Os experimentos, cada um com uma hora de duração, foram realizados durante o ciclo diário, utilizando-se iluminação de espectro completo. Registraram-se as espécies, o número de indivíduos e o horário de passagem. Os registros de cada observador humano in situ foram comparados com os dos vídeos. Consideraram-se curimba (Prochilodus lineatus), mandi-amarelo (Pimelodus maculatus), piau-três-pintas (Leporinus friderici) e ferreirinha (Leporinus octofasciatus) como espécies alvo, tendo em vista sua alta freqüência de ocorrência na escada de peixes da UHE Igarapava. O número de espécies e o número de indivíduos não foram estatisticamente diferentes entre observadores. Por outro lado, o número de espécies e o número de indivíduos que passaram pelo visor foram estatisticamente diferentes entre experimentos. Assim, demonstrou-se que os três observadores registraram o mesmo número de espécies e contaram o mesmo número de indivíduos, mesmo quando as duas variáveis diferiram significativamente entre experimentos. Concluiu-se que o sistema de vídeo imagem constitui um método eficaz para avaliação da passagem de peixes na escada de peixes de Igarapava. Abstract in english On site human observations and video images were collected and compared at the window of the Igarapava Dam fish ladder (IDFL), rio Grande , Southeastern Brazil, between March 1st and June 30th, 2004. We conducted four experiments with two humans (Observer 1 and Observer 2) observing fish passage in the IDFL window while a Sony 3CCD video camera (Observer 3) recorded fish passage at the same time. Experiments, each one hour in length, were distributed throughout the diel c (more) ycle using full spectrum lights. We identified fish species, the number of individuals for each species, and the real time that they passed. Counts from each human observer were compared to the video counts. The fish species most commonly observed in the window were - curimba (Prochilodus lineatus), mandi-amarelo (Pimelodus maculatus), piau-três-pintas (Leporinus friderici) and ferreirinha (Leporinus octofasciatus). The number of species and individuals were indistinguishable for the three observers. But, the number of species and individuals were significantly different among experiments. Thus, the three observers register the same number of species and count the same number of individuals even when these two response variables differ significantly among experiments. Based on these results, we concluded that the video count was an accurate method to assess fish passage at the IDFL.

Bowen, Mark D.; Marques, Simone; Silva, Luiz G. M.; Vono, Volney; Godinho, Hugo P.

2006-06-01

33

Correspondence - Design of ladder-type SAW/BAW.  

Science.gov (United States)

This paper describes the design of RF SAW/ BAW filters with constant group delay. The band-pass LC filter is designed based on the traditional Bessel filter design. Then, LC resonators in the filter are replaced by SAW/BAW resonators with finite capacitance ratio ?. Finite ? generates passband ripples in the group delay. However, it is shown the ripples can be suppressed by optimal design of the SAW/BAW resonators. Norton's first transform is also applied to the designed filter to reduce variation of resonator shunt capacitances. Finally, extremely flat group delay with deviation of 4 ns over the frequency range of ±20 MHz at the center frequency of 1 GHz is theoretically demonstrated. PMID:23221231

Wang, Hualei; Chen, Jing; Shi, Yu; Omori, Tatsuya; Ahn, Changjun; Hashimoto, Ken-ya

2012-12-01

34

Environmental factors related to entry into and ascent of fish in the experimental ladder located close to Itaipu Dam  

Directory of Open Access Journals (Sweden)

Full Text Available We evaluated the seasonality of the ascent of fish in an experimental ladder located close to Itaipu Dam, and its relationships to reproduction, temperature, river level and discharge. Samplings of fish and measurements of abiotic factors were performed from February, 1995 through January, 1997, in two resting pools of the ladder. Pool A was located 10 m above the mean level of the Paraná River; Pool B was located at the upper end of the ladder, at a height of 27 m. Autoregressive models were used to remove the temporal dependence between observations. Residuals of the models were used to relate, using Pearson's correlation coefficient, the densities of fish to the environmental variables. Clear patterns of seasonality were observed for temperature. River level, turbine discharge and spillway discharge, although they showed no clear seasonal dynamics, were time-dependent, because the autocorrelation coefficients for different k values were significant. In the samples of larger-sized fish, 23 species were recorded during the two years of study. Most of the individuals were in a non reproductive state, and about 90% of the individuals belonged to only six species. The temporal variability in total abundance, considering all species, indicated a pattern of seasonal variation; high abundances occurred from October through February (75%) and in Pool A (61% of the 1343 individuals sampled). Low abundances were recorded during winter, with the correlogram of total density confirming this tendency. In the samples of smaller-sized species, six species were recorded, with all six present in both pools, but more frequent in the first pool (64%). Bryconamericus stramineus comprised 99% of the total numbers of smaller fish in the samples. The total abundance of small species showed different temporal patterns of seasonal variation in the two years of study.O presente estudo avalia a sazonalidade da ascensão de peixes na escada experimental localizada junto à barragem da hidrelétrica de Itaipu e as relações com a reprodução, temperatura, nível do rio e suas vazões. As amostragens de peixes e de fatores abióticos foram obtidas de fevereiro de 1995 a janeiro de 1997, em dois tanques de descanso, aqui denominados Caixas, sendo o primeiro, Caixa A, localizado na altura de 10 m da cota média do rio Paraná, e o segundo, Caixa B, ao final da escada, a 27 m de altura. Modelos autoregressivos foram empregados com o objetivo de remover a dependência temporal entre as observações. Posteriormente, os resíduos dos modelos foram utilizados para relacionar, através do coeficiente de correlação de Pearson, as densidades de peixes com as variáveis ambientais. Padrões claros de sazonalidade foram observados para a variável temperatura. As variáveis cota, vazão turbinada e vazão vertida, embora não tenham apresentado dinâmicas sazonais claras, foram temporalmente dependentes, tendo em vista que os coeficientes de autocorrelação, para diferentes k, foram significativos. Na amostragem de peixes de maior porte foram registradas 23 espécies ao longo dos dois anos de estudo, sendo que a maior parte dos indivíduos não se encontrava em reprodução e cerca de 90% dos indivíduos amostrados pertenciam a apenas seis espécies. A variabilidade temporal da abundância total, considerando o conjunto das espécies, indicou um padrão de variação sazonal, permitindo evidenciar que os maiores valores de abundância foram observados sistematicamente nos meses de outubro a fevereiro (75%) e na caixa A (61% dos 1343 indivíduos amostrados). Os menores valores foram registrados nos meses de inverno. O correlograma da densidade total confirma essa tendência. Nas amostragens destinadas às espécies de pequeno porte, foram registradas seis espécies, todas presentes em ambas as caixas, sendo mais freqüentes na primeira (64%). Entre essas espécies, Bryconamericus stramineus contribuiu com 99% do total amostrado. A variabilidade temporal da abundância total das espécies de pequeno porte indicou um padrão distinto de

Domingo Rodrigues Fernandez; Angelo Antonio Agostinho; Luis Maurício Bini; Luiz Carlos Gomes

2007-01-01

35

Design theory in offshore fish cage designing  

UK PubMed Central (United Kingdom)

Population increase, food security, employment, stresses on the fresh water resources and uncertainty associated with wild fish stocks are key parameters driving the demand for aquaculture expansion. Limitation in adequate waters in the coastal and near-shore sites for aquaculture development and the interactions within and from other coastal services forces the fish farming industry to move further offshore. Impact on the environment is an increasing concern that has to be considered in any aquaculture system designing. Moving further offshore could provide a better return on investment through various factors such as reduced mortality, better growth rates, less diseases and net fouling. However, moving offshore comes with a new set of challenges in withstanding severe weather conditions and safe and economic functioning of the aquaculture systems. Currently, the offshore fish cage design concepts are in their infancy and there is a race towards an optimum cage design for the offshore environment. Hence, in the aim of deriving an optimum cage design concept, this paper attempts to apply a holistic and theoretical approach to fish cage designing. By the application of theory of design, but different from the traditional engineering designing process, the paper proposes a conceptual framework and a cage design concept for offshore fish cage designing.

Shainee M; Ellingsen H; Leira BJ; Fredheim A

2013-05-01

36

Ladder Logic  

Science.gov (United States)

Created by Tony R. Kuphaldt, with help from contributor Roger Hollingsworth, this chapter of All About Circuit's fourth volume on Digital circuits describes the logic behind them. The chapter is divided into six sections: "Ladder" diagrams, Digital logic functions, Permissive and interlock circuits, Motor control circuits, Fail-safe design, and Programmable logic controllers. Each section has clear illustrations and a concise, bulleted review of what was covered at the end. There is also a link to the All About Circuits forums, where contributors and other visitors discuss the material presented. This is an excellent resource for educators in physics and electronic engineering classrooms to introduce lessons or units on digital circuits.

Kuphaldt, Tony R.

2008-07-17

37

Pelton Ladder Master Plan.  

Energy Technology Data Exchange (ETDEWEB)

Rearing additional fish in Pelton Ladder provides fishery managers with a low-cost alternative to making major financial investments in new formal hatchery facilities. Adult chinook returning from this rearing program will help bolster the dwindling runs of upriver spring chinook, thus assisting the Council's goal for increased production of this species. The Deschutes River Subbasin Plan envisions need for additional return of hatchery-produced spring chinook in order to meet goals for increased harvest opportunity. Spring chinook released from Pelton Ladder will contribute little to offshore fisheries, as we can account for only about 1 percent of the RBH contribution in offshore fisheries. Based on past performance, we expect 6 percent of the adults produced will be caught in sport, commercial, and tribal subsistence fisheries in the Columbia River. Most benefits of the extra adults produced will be realized in the Deschutes River in the form of increased sport and tribal harvests and increased returns to RBH. Adults collected at Pelton Ladder above production needs will be provided to the CTWS. Return of more adults to the Deschutes River will continue the trend of increased abundance of spring chinook noted since 1985. Rearing of fish in the ladder under the proposed program will provide ODFW and CTWS co-management opportunity, and the associated monitoring and evaluation studies will refine ODFW's ability to effectively manage the RBWPelton Ladder rearing program and will provide inferences about the ability to further employ the fish-rearing potential of unused sections of the fish ladder.

Smith, Max

1991-07-01

38

Design and Implementation for Ladder Diagram in Hydropower Simulation System Based on All Paths Searching Algorithm  

Directory of Open Access Journals (Sweden)

Full Text Available An approach to design and implement the control function of LD (Ladder Diagram) in the hydropower simulation system based on all paths searching algorithm is proposed in this paper. LD is widely used as a programming language for PLC (Programmable Logic Controller), but it doesn’t be executed automatically in the hydropower simulation system which is a software system, and there is no compiler or interpretation for LD in it. The approach in this paper is not only to present a graphical interface to design LD, but also implement its control function through transforming it to a corresponding undigraph, in which, all paths be-tween two vertexes (live wire and null line) are searched by the proposed algorithm. An application example is presented to verify the validity of the algorithm and shows that the algorithm is correct and practicable. In addition, how to implement the control function based on object-oriented thought is introduced. The running time is shown at last, which proves that the system with the algorithm can meet the real-time request in the hydropower simulation system.

Bo LI; Hai ZHAO; Chun-He SONG; Hui LI; Jun AI

2009-01-01

39

Designing and constructing an 100 bp DNA Ladder by combining PCR and enzyme digestion methods  

Directory of Open Access Journals (Sweden)

Full Text Available "n Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;} Background: Molecular DNA markers are one of the most important tools in molecular biology labs. The size of DNA molecules is determined by comparing them with known bands of markers during gel electrophoresis. There are many different protocols to produce these kinds of molecular markers. In this study we have suggested an efficient strategy to produce molecular weight markers in industrial proportions."n"nMethods : To achieve the desired sizes of DNA fragments, a combination of two previously known methods, restriction enzyme digestion and polymerase chain reaction (PCR), were used. The enzymatic digestion process was based on designing and constructing plasmids which equaled in size with the desired length of DNA fragments and produced the desired DNA fragment upon linearization. In the PCR method, the desired length of DNA fragments were cloned in multiple cloning sites of pTZ57R plasmid and in a PCR reaction, the new constructed plasmid was used as a template to produce the final fragment."n"nResults : Upon application of this strategy, 2000 and 3000 bp DNA fragments were produced by enzymatic digestion of plasmids of the same size. Moreover, 100 to 1500 bp fragments were produced during PCR using only a set of forward and reverse primers at the flanking region of pTZ57R multiple cloning site."n"nConclusion: The highest advantage of this cost-benefit approach is to produce different types of molecular weight markers by using an effective and short protocol."n"nKeywords: DNA markers, DNA Ladder, agarose gel electrophoresis, molecular weight.

Saidijam M; Khanahmad Shahreza H; Rikhtegaran Tehrani Z; Karimizare S; Shabab N; Behdani M

2011-01-01

40

Voegelin's Ladder  

Directory of Open Access Journals (Sweden)

Full Text Available Leadership has non-logical aspects. One of these is spirituality. Voegelin’s Ladder provides a context for studying spirituality as a part of leadership. What it reveals is that spirituality arises at the intersection of the human with the divine. Spirituality expresses itself as purpose and aspiration, which a leader embodies.

Nathan Harter

2006-01-01

 
 
 
 
41

Ladder Safety Guide  

Science.gov (United States)

... Resources Copyright 2012 American Academy of Orthopaedic Surgeons Ladder Safety Guide Ladders are useful tools. Nearly everyone uses them to ... and to clean gutters or hang holiday lights. Ladders also are potentially dangerous, causing more than 164, ...

42

Ejs TPT Ladder Demonstration Model  

Science.gov (United States)

The Ejs TPT Ladder Demonstration model displays the statics and dynamics of a ladder leaning against a wall. The standard (textbook) statement of this problem assumes that there is no frictional force between the wall and the ladder, but a frictional force between the ground and the ladder. In the simulation you can set the initial lean angle and the coefficients of static and kinetic friction between the floor and the ladder. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs TPT Ladder Demonstration model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_tpt_ladder_demo.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Belloni, Mario

2008-08-17

43

Understanding the Behaviour of Infinite Ladder Circuits  

Science.gov (United States)

Infinite ladder circuits are often encountered in undergraduate electrical engineering and physics curricula when dealing with series and parallel combination of impedances, as a part of filter design or wave propagation on transmission lines. The input impedance of such infinite ladder circuits is derived by assuming that the input impedance does…

Ucak, C.; Yegin, K.

2008-01-01

44

Hood River and Pelton Ladder Monitoring and Evaluation Project and Hood River Fish Habitat Project : Annual Progress Report 1999-2000.  

Energy Technology Data Exchange (ETDEWEB)

The Hood River subbasin is home to four species of anadromous salmonids: chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), steelhead (Oncorhynchus mykiss), and sea run cutthroat trout (Salmo clarki). Indigenous spring chinook salmon were extirpated during the late 1960's. The naturally spawning spring chinook salmon currently present in the subbasin are progeny of Deschutes stock. Historically, the Hood River subbasin hatchery steelhead program utilized out-of-basin stocks for many years. Indigenous stocks of summer and winter steelhead were listed in March 1998 by National Marine Fisheries Service (NMFS) under the Endangered Species Act (ESA) as a ''Threatened'' Species along with similar genetically similar steelhead in the Lower Columbia Basin. This annual report summarizes work for two consecutive contract periods: the fiscal year (FY) 1999 contract period was 1 October, 1998 through 30 September, 1999 and 1 October, 1999 through 30 September, 2000 for FY 2000. Work implemented during FY 1999 and FY 2000 included (1) acclimation of hatchery spring chinook salmon and hatchery summer and winter steelhead smolts, (2) spring chinook salmon spawning ground surveys on the West Fork Hood River (3) genetic analysis of steelhead and cutthroat [contractual service with the ODFW], (4) Hood River water temperature studies, (5) Oak Springs Hatchery (OSH) and Round Butte Hatchery (RBH) coded-wire tagging and clipping evaluation, (6) preparation of the Hood River Watershed Assessment (Coccoli et al., December 1999) and the Fish Habitat Protection, Restoration, and Monitoring Plan (Coccoli et al., February 2000), (7) project implementation of early action habitat protection and restoration projects, (8) Pelton Ladder evaluation studies, (9) management oversight and guidance to BPA and ODFW engineering on HRPP facilities, and (10) preparation of an annual report summarizing project objectives for FY 1999 and FY 2000.

Lambert, Michael B.; McCanna, Joseph P.; Jennings, Mick

2001-02-01

45

The Design and Implementation of a Biomimetic Robot Fish  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, a novel design of a biomimetic robot fish is presented. Based on the propulsion and maneuvering mechanisms of real fishes, a tail mechanical structure with cams and connecting rods for fitting carangiform fish body wave is designed, which provides the main propulsion. Two pectoral fin...

Chao Zhou; Min Tan; Nong Gu; Zhiqiang Cao; Shuo Wang; Long Wang

46

Fish passage system in an irrigation dam (Pilcomayo River basin ): when engineering designs do not match ecohydraulic criteria  

Directory of Open Access Journals (Sweden)

Full Text Available The Route 28 Dam has the potential to block fish movements from La Estrella marsh to the Pilcomayo River. In addition, the many fish that concentrate immediately downstream of the dam may suffer high mortality when they are stranded during low water periods. The goals of this study are to determine if fish are able to pass the spillway and to assess if the design of the installed ladders (pool and weir type) effectively supports upstream migration of Prochilodus lineatus (sábalo). Results showed that only fish longer than 39 cm should be able to ascend the spillway chute, but when water levels on the spillway crest are over 0.4 m. Fish are also unable to jump from spillway toe to spillway crest because the downstream dissipation pool does not meet the minimum depth criterion for fish to accelerate to sufficient velocity. Fish ladders have insufficient number of pools and some pool dimensions and designs depart from accepted standard designs. Volumetric dissipation power in the upper pool of each fish ladder is too low for fish to rest. Also, attraction flows relative to total spillway discharge at the entrance to each fishway are insufficient. Fish passage failures of both the spillway and pool and weir systems in La Estrella marsh can be traced to the "salmon-centric" concept used by the designers. We conclude that the Route 28 Dam design including its fish passage systems, do not follow criteria to cope with the strong hydrological variability and bioecological characteristics of fish inhabiting pulsatile systems such as La Estrella marsh.La represa dela ruta 28 posee el potencial de bloquear el desplazamiento del sábalo (Prochilodus lineatus) desde el bañado La Estrella hacia el río Pilcomayo. Adicionalmente los numerosos peces que se concentran aguas abajo de la represa pueden sufrir una alta mortalidad cuando quedan atrapados durante el período de aguas bajas. Los objetivos de este estudio es determinar si los peces son capaces de superar el vertedero y evaluar si el diseño de los pasos para peces del tipo tanque-escalón ya instalados esadecuado para facilitar la migración hacia aguas arriba. Los resultados muestran que solo aquellos peces mayores a 39 cm de longitud total son capaces de ascender la pendiente del vertedero, pero únicamente cuando el nivel del agua en la cresta del mismo alcanza o supera los 40 cm. Los peces son incapaces de saltar desde el pie del vertedero hasta la cresta debido a que la pileta de disipación no sigue los criterios de mínima profundidad requeridos para alcanzar la suficiente velocidad y altura. Asimismo, los pasos para peces no poseen el número suficiente de tanques y algunas de sus dimensiones y su diseño se apartan de los estándares aceptados. La potencia de disipación volumétrica en el tanque superior de cada paso es inadecuada para que los peces puedan descansar, mientras que los flujos de atracción relativos a la descarga del vertedero resultan insuficientes. La baja eficiencia del vertedero y de los sistemas de pasos para peces pueden ser adjudicados a un concepto de construcción orientado a salmónidos. Concluimos que la represa de la ruta 28, incluyendo sus sistemas de pasaje para peces, no siguen los criterios adecuados para hacer frente a alta variabilidad hidrológica y las características bioecológica de los peces que habitan en bañados pulsátiles como La Estrella.

Claudio R. M. Baigún; John M. Nestler; Priscilla Minotti; Norberto Oldani

2012-01-01

47

Experimental evidence of variable-order behavior of ladders and nested ladders  

CERN Multimedia

The experimental study of two kinds of electrical circuits, a domino ladder and a nested ladder, is presented. While the domino ladder is known and already appeared in the theory of fractional-order systems, the nested ladder circuit is presented in this article for the first time. For fitting the measured data, a new approach is suggested, which is based on using the Mittag-Leffler function and which means that the data are fitted by a solution of an initial-value problem for a two-term fractional differential equation. The experiment showed that in the frequency domain the domino ladder behaves as a system of order 0.5 and the nested ladder as a system of order 0.25, which is in perfect agreement with the theory developed for their design. In the time domain, however, the order of the domino ladder is changing from roughly 0.5 to almost 1, and the order of the nested ladder is changing in a similar manner, from roughly 0.25 to almost 1; in both cases, the order 1 is never reached, and both systems remain th...

Sierociuk, Dominik; Petras, Ivo

2011-01-01

48

Allelic ladder loci  

UK PubMed Central (United Kingdom)

Disclosed are rare short tandem repeat (STR) alleles within the D10S1248 and D12S391 loci in humans. Provided are representative allelic ladders for each locus, methods and assays using these alleles and kits containing allelic ladders comprising these alleles for accurate genotyping and identification of a wide range of individuals.

GREEN ROBERT; MULERO JULIO; HENNESSY LORI; LAGACE ROBERT; CHANG CHIEN-WEI

49

ALLELIC LADDER LOCI  

UK PubMed Central (United Kingdom)

Disclosed are rare short tandem repeat (STR) alleles within the D10S1248 and D12S391 loci in humans. Provided are representative allelic ladders for each locus, methods and assays using these alleles and kits containing allelic ladders comprising these alleles for accurate genotyping and identification of a wide range of individuals.

GREEN ROBERT; MULERO JULIO; HENNESSY LORI; LAGACE ROBERT; CHANG CHIEN-WEI

50

The Design and Implementation of a Biomimetic Robot Fish  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a novel design of a biomimetic robot fish is presented. Based on the propulsion and maneuvering mechanisms of real fishes, a tail mechanical structure with cams and connecting rods for fitting carangiform fish body wave is designed, which provides the main propulsion. Two pectoral fins are mounted, and each pectoral fin can flap separately and rotate freely. Coordinating the movements of the tail and pectoral fins, the robot fish can simulate the movements of fishes in water. In order to obtain the necessary environmental information, several kinds of sensors (video, infrared, temperature, pressure and PH value sensors) were mounted. Finally, the realization of the robot fish is presented.

Chao Zhou; Min Tan; Nong Gu; Zhiqiang Cao; Shuo Wang; Long Wang

2008-01-01

51

Understanding the behaviour of infinite ladder circuits  

International Nuclear Information System (INIS)

Infinite ladder circuits are often encountered in undergraduate electrical engineering and physics curricula when dealing with series and parallel combination of impedances, as a part of filter design or wave propagation on transmission lines. The input impedance of such infinite ladder circuits is derived by assuming that the input impedance does not change when a new block of impedance is added. However, the impedance derived from this assumption may lead to incorrect conclusions if it is not treated carefully. Sometimes, in the literature, the input impedance behaviour of infinite ladder circuits is referred to as a paradox, leaving students and educators in doubt. This study intends to clarify this confusion and help to better comprehend the behaviour of the input impedance of infinite ladder circuits.

2008-01-01

52

Understanding the behaviour of infinite ladder circuits  

Energy Technology Data Exchange (ETDEWEB)

Infinite ladder circuits are often encountered in undergraduate electrical engineering and physics curricula when dealing with series and parallel combination of impedances, as a part of filter design or wave propagation on transmission lines. The input impedance of such infinite ladder circuits is derived by assuming that the input impedance does not change when a new block of impedance is added. However, the impedance derived from this assumption may lead to incorrect conclusions if it is not treated carefully. Sometimes, in the literature, the input impedance behaviour of infinite ladder circuits is referred to as a paradox, leaving students and educators in doubt. This study intends to clarify this confusion and help to better comprehend the behaviour of the input impedance of infinite ladder circuits.

Ucak, C; Yegin, K [Department of Electrical and Electronics Engineering, Yeditepe University, Istanbul (Turkey)], E-mail: canbolat@yeditepe.edu.tr

2008-11-15

53

Deflector designs for fish habitat restoration.  

UK PubMed Central (United Kingdom)

Paired current deflectors are structures that are installed on each bank of a river to locally reduce the width of the channel, thereby creating flow acceleration and promoting scouring. These instream habitat structures have been used extensively in restoration projects to create pool habitat for fish, but there are many discrepancies in deflector design recommendations in terms of orientation, height, and length. Our objectives were to (1) examine how the angle, height, and length of paired deflectors affect scour hole dimensions and potential for bank erosion; and (2) test the applicability to paired deflectors of existing equations for scour hole depth and volume. Three deflector angles (45 degrees, 90 degrees, and 135 degrees), two deflector heights (with flow under and over the deflector height), and two lengths (reducing the width by 25% and 50%) were investigated using uniform sand in a laboratory flume. Results showed a 26-30% smaller scour depth resulting from 45 degrees deflectors than from 90 degrees deflectors and a 5-10% smaller scour depth for 135 degrees deflectors compared to 90 degrees deflectors. The volume of scour and the potential for bank erosion were greater when flow was under the height of the deflectors rather than overtopping and when the length of deflector was increased. When flow was under the deflector height, 135 degrees deflectors had the highest amount of bank erosion; whereas during overtopping flow conditions, 90 degrees deflectors had the greatest bank erosion potential. Values predicted by the model of Kuhnle and others were closest to observed scour depth and volume measurements. The assumption that upstream-oriented deflectors always generate the largest scour should be revised.

Biron PM; Robson C; Lapointe MF; Gaskin SJ

2004-01-01

54

Ladder attachment platform  

Science.gov (United States)

A ladder attachment platform is provided that includes a base for attachment to a ladder that has first and second side rails and a plurality of rungs that extend between in a lateral direction. Also included is a user platform for having a user stand thereon that is carried by the base. The user platform may be positioned with respect to the ladder so that it is not located between a first plane that extends through the first side rail and is perpendicular to the lateral direction and a second plane that extends through the second side rail and is perpendicular to the lateral direction.

Swygert,; Richard, W [Springfield, SC

2012-08-28

55

Six-degree-of-freedom Sensor Fish design and instrumentation  

Energy Technology Data Exchange (ETDEWEB)

Fish passing through dams may be injured or killed despite advances in turbine design, project operations and other fish bypass systems. The Six-degree-of-freedom (6DOF) Sensor Fish device is an autonomous sensor package designed to characterize the physical conditions and physical stresses fish are exposed to when they pass through complex hydraulic environments. It has been used to identify the locations and operations where conditions are severe enough to injure or kill fish. During the design process, a set of governing equations of motion for the device was derived and simulated in order to understand the design implications of instrument selection and placement within the body of the device. The sensor package includes three rotation sensors, three acceleration sensors, a pressure sensor, and a temperature sensor with a sampling frequency of 2,000 Hz. Its housing is constructed of clear polycarbonate plastic. It is 24.5 mm in diameter and 90 mm in length, weighs about 43 grams, similar to the size and density of a yearling salmon smolt. The relative errors of both the linear acceleration and angular velocity measurements were determined to be less than 5% from laboratory acceptance tests. Since its development in 2005, the 6DOF Sensor Fish device has been successfully deployed at many major dams in the United States.

Deng, Zhiqun; Carlson, Thomas J.; Duncan, Joanne P.; Richmond, Marshall C.

2007-12-19

56

Bisdithiazolyl radical spin ladders.  

UK PubMed Central (United Kingdom)

A series of four bisdithiazolyl radicals 1a-d (R(1) = Pr, Bu, Pn, Hx; R(2) = F) has been prepared and characterized by X-ray crystallography. The crystal structure of 1a (R(1) = Pr) belongs to the tetragonal space group P42(1)m and consists of slipped ?-stack arrays of undimerized radicals packed about 4 centers running along the z-direction, an arrangement identical to that found for 1 (R(1) = Et; R(2) = F). With increasing chain length of the R(1) substituent, an isomorphous set 1b-d is generated. All three compounds crystallize in the P2(1)/c space group and consist of pairs of radical ?-stacks locked together by strong intermolecular F···S' bridges to create spin ladder arrays. The slipped ?-stack alignment of radicals produces close S···S' interactions which serve as the "rungs" of a spin ladder, and the long chain alkyl substituents (R(1)) serve as buffers which separate the ladders from each other laterally. Variable temperature magnetic susceptibility measurements indicate that 1a behaves as an antiferromagnetically coupled Curie-Weiss paramagnet, the behavior of which may be modeled as a weakly coupled AFM chain. Stronger antiferromagnetic coupling is observed in 1b-d, such that the Curie-Weiss fit is no longer applicable. Analysis of the full data range (T = 2-300 K) is consistent with the Johnston strong-leg spin ladder model. The origin of the magnetic behavior across the series has been explored with broken-symmetry Density Functional Theory (DFT) calculations of individual pairwise exchange energies. These confirm that strong antiferromagnetic interactions are present within the ladder "legs" and "rungs", with only very weak magnetic exchange between the ladders.

Lekin K; Wong JW; Winter SM; Mailman A; Dube PA; Oakley RT

2013-02-01

57

Staggered ladder spectra.  

UK PubMed Central (United Kingdom)

We exactly solve a Fokker-Planck equation by determining its eigenvalues and eigenfunctions: we construct nonlinear second-order differential operators which act as raising and lowering operators, generating ladder spectra for the odd- and even-parity states. The ladders are staggered: the odd-even separation differs from even-odd. The Fokker-Planck equation corresponds, in the limit of weak damping, to a generalized Ornstein-Uhlenbeck process where the random force depends upon position as well as time. The process describes damped stochastic acceleration, and exhibits anomalous diffusion at short times and a stationary non-Maxwellian momentum distribution.

Arvedson E; Wilkinson M; Mehlig B; Nakamura K

2006-01-01

58

Staggered ladder spectra.  

Science.gov (United States)

We exactly solve a Fokker-Planck equation by determining its eigenvalues and eigenfunctions: we construct nonlinear second-order differential operators which act as raising and lowering operators, generating ladder spectra for the odd- and even-parity states. The ladders are staggered: the odd-even separation differs from even-odd. The Fokker-Planck equation corresponds, in the limit of weak damping, to a generalized Ornstein-Uhlenbeck process where the random force depends upon position as well as time. The process describes damped stochastic acceleration, and exhibits anomalous diffusion at short times and a stationary non-Maxwellian momentum distribution. PMID:16486675

Arvedson, E; Wilkinson, M; Mehlig, B; Nakamura, K

2006-01-25

59

Six-Degree-of-Freedom Sensor Fish Design and Instrumentation  

Directory of Open Access Journals (Sweden)

Full Text Available Fish passing through dams may be injured or killed despite advances in turbinedesign, project operations and other fish bypass systems. The six-degree-of-freedom (6DOF)Sensor Fish device is an autonomous sensor package that characterizes the physical conditionsand physical stresses to which fish are exposed when they pass through complex hydraulicenvironments. It has been used to identify the locations and operations where conditions aresevere enough to injure or kill fish. During the design process, a set of governing equationsof motion for the Sensor Fish was derived and simulated to understand the design implica-tions of instrument selection and placement within the body of the device. The Sensor Fishpackage includes three rotation sensors, three acceleration sensors, a pressure sensor, and atemperature sensor with a sampling frequency of 2,000 Hz. Its housing is constructed of clearpolycarbonate plastic. It is 24.5 mm in diameter and 90 mm in length and weighs about 43 g,similar to the size and density of a yearling salmon smolt. The accuracy of the pressure sensorwas determined to be within 0.2 psi. In laboratory acceptance tests, the relative errors of boththe linear acceleration and angular velocity measurements were determined to be less than5%. An exposure is defined as a significant event when the acceleration reaches predefinedthresholds. Based on the different characteristic of acceleration and rotation velocities, theexposure event is categorized as either a collision between the Sensor Fish and a solid struc-ture or shear caused by turbulence. Since its development in 2005, the 6DOF Sensor Fish hasbeen deployed successfully at many major dams in the United States.

Zhiqun Deng; Thomas J. Carlson; Joanne P.; Marshall C. Richmond

2007-01-01

60

Electronic Structure of Ladder Cuprates  

CERN Multimedia

We study the electronic structure of the ladder compounds (SrCa)CuO 14-24-41 and SrCuO 123. LDA calculations for both give similar Cu 3d-bands near the Fermi energy. The hopping parameters estimated by fitting LDA energy bands show a strong anisotropy between the t_perp t_par intra-ladder hopping and small inter-ladder hopping. A downfolding method shows that this anisotropy arises from the ladder structure.The conductivity perpendicular to the ladders is computed assuming incoherent tunneling giving a value close to experiment.

Müller, T F A; Rice, T M; Das-Gupta, I; Saha-Dasgupta, T

1998-01-01

 
 
 
 
61

Fish swarm optimization algorithm applied to engineering system design  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Nowadays, optimization techniques based on the analogy with swarming principles and collective activities of social species in nature have been used in the development of methodologies for solving a variety of real-world optimization problems. In this context, the social behavior of fish colonies has been recently explored to develop a novel algorithm, the so-called Fish Swarm Optimization Algorithm (FSOA), based on the behavior of fish swarm in search for food. In this p (more) aper, the FSOA is applied to four engineering systems, involving typical structural design and distillation column design. The results obtained are then compared with those obtained from other classical evolutionary approaches.

Lobato, Fran Sérgio; Steffen Jr., Valder

62

The Truck and Ladder  

Science.gov (United States)

The representation depicts the continued motion of a ladder placed on the roof of a truck as the truck comes to a stop. This demonstration of an object's continued motion in the absence of unbalanced forces is illustrated by an animated GIF and described by accompanying text.

63

Climbing Bloom's Ladder  

Science.gov (United States)

This article discusses the author's observation that in his thirty-plus years in academics, many students who, by natural ability, interest, and work ethic, should have performed well in the sciences, but performed poorly. Many of these students are operating at the bottom rungs of Bloom's taxonomy (ladder), while college professors and industrial…

Warner, Isiah M.

2004-01-01

64

Beyond the ladder  

International Nuclear Information System (INIS)

The authors study chiral symmetry breaking for vanishing ?-function and with ultraviolet cutoff ?, beyond the ladder approximation. They are able to deduce enough about the Schwinger-Dyson equation to obtain properties of the self-energy ?(?). In particular in the limit ?/? implies ? (? ? ?(?)) the authors obtain the relation between ?/? and a function of the coupling ?. And in this limit they obtain an explicit expression for ?(?) which is good over most of the range ?

1988-01-01

65

Anderson localization in Hubbard ladders  

CERN Document Server

The effect of a weak random potential on two-leg Hubbard ladders is investigated. The random potential is shown to induce Anderson localization except for attractive enough interactions, supressing completely d-wave superconductivity. These localization effects remain very strong even for many ladders coupled by Josephson coupling. Both dc and ac conductivities and localization lengths are obtained. Consequences for the superconducting ladder compound Sr$_x$Ca$_{14-x}$Cu$_{24}$O$_{41+\\delta}$ are discussed.

Orignac, E

1999-01-01

66

Bending continuous structures with SMAs: a novel robotic fish design.  

Science.gov (United States)

In this paper, we describe our research on bio-inspired locomotion systems using deformable structures and smart materials, concretely shape memory alloys (SMAs). These types of materials allow us to explore the possibility of building motor-less and gear-less robots. A swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature of the body. This type of structural arrangement is inspired by fish red muscles, which are mainly recruited during steady swimming for the bending of a flexible but nearly incompressible structure such as the fishbone. This paper reviews the design process of these bio-inspired structures, from the motivations and physiological inspiration to the mechatronics design, control and simulations, leading to actual experimental trials and results. The focus of this work is to present the mechanisms by which standard swimming patterns can be reproduced with the proposed design. Moreover, the performance of the SMA-based actuators' control in terms of actuation speed and position accuracy is also addressed. PMID:22126900

Rossi, C; Colorado, J; Coral, W; Barrientos, A

2011-11-29

67

Bending continuous structures with SMAs: a novel robotic fish design  

International Nuclear Information System (INIS)

In this paper, we describe our research on bio-inspired locomotion systems using deformable structures and smart materials, concretely shape memory alloys (SMAs). These types of materials allow us to explore the possibility of building motor-less and gear-less robots. A swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature of the body. This type of structural arrangement is inspired by fish red muscles, which are mainly recruited during steady swimming for the bending of a flexible but nearly incompressible structure such as the fishbone. This paper reviews the design process of these bio-inspired structures, from the motivations and physiological inspiration to the mechatronics design, control and simulations, leading to actual experimental trials and results. The focus of this work is to present the mechanisms by which standard swimming patterns can be reproduced with the proposed design. Moreover, the performance of the SMA-based actuators' control in terms of actuation speed and position accuracy is also addressed.

2011-01-01

68

Theon's Ladder for Any Root  

Science.gov (United States)

Theon's ladder is an ancient algorithm for calculating rational approximations for the square root of 2. It features two columns of integers (called a ladder), in which the ratio of the two numbers in each row is an approximation to the square root of 2. It is remarkable for its simplicity. This algorithm can easily be generalized to find rational…

Osler, Thomas J.; Wright, Marcus; Orchard, Michael

2005-01-01

69

Method for designing and optimizing fish reef on basis of quantizing factor of trapping effect of artificial fish reef  

UK PubMed Central (United Kingdom)

The invention discloses a method for designing and optimizing a fish reef on basis of quantizing factor of trapping effect of an artificial fish reef. The method comprises the following steps: carrying out analysis on characteristic of a reef body and index decomposition on influence factor, selecting a testing object for validation, analyzing and comparing the testing result, introducing the feature factor of the reef body, subsequently comparing the feature factors affecting the trapping effect of the fish reef testing object, screening the sequence of the fish reef feature factors in affecting the fish reef trapping effect, and finally putting forward betterment comment on the reef body design and structure optimization. In the invention, the method bases on the structural features of the fish reef and evaluates the influence of the artificial fish reef feature factor on the fish reef trapping effect, thus eliminating the disadvantageous factor on the design of the artificial reef and sufficiently plays the trapping effect of the artificial fish reef on the biology.

SHUO ZHANG

70

Fish  

Science.gov (United States)

In this project you will learn about different types of fish. In your science journal write what you know about fish. Draw a picture of a common fish you might see where you live. On the handout record the information you learn during this unit. Click here to see the Angel Fish. Record information on Handout #1. Now go to the Clown Fish. ...

Hunter, Ms.

2009-07-07

71

Undergraduate design projects for assistive technology needs: assisted fishing.  

UK PubMed Central (United Kingdom)

In 2010 the University of Wyoming, College of Engineering and Applied Science was funded for a five year increment of the National Science Foundation?s Research to Aid Persons with Disabilities. This program provides a vital link between challenged individuals who require custom assistive technology devices with senior capstone design students who require challenging, meaningful projects. The program also provides education for our next generation of engineers on the needs of all individuals. In this paper we describe the program organization including project partners in the College and Wyoming Institute for Disabilities (WIND). We also provide a case study of a recently completed project for an assistive fishing device.

Borrego N; Bilan K; Gebes TJ; Barrett SF; Morton SA

2012-01-01

72

Six-Degree-of-Freedom Sensor Fish Design and Instrumentation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Fish passing through dams may be injured or killed despite advances in turbinedesign, project operations and other fish bypass systems. The six-degree-of-freedom (6DOF)Sensor Fish device is an autonomous sensor package that characterizes the physical conditionsand physical stresses to which fish are...

Zhiqun Deng; Thomas J. Carlson; Joanne P.; Marshall C. Richmond

73

Variations of the Sliding Ladder Problem  

Science.gov (United States)

This article takes another look at the sliding ladder problem that students meet in the study of related rates in calculus. Physically realistic situations with both constrained and understrained ladders are explored.

Kapranidis, Stelios; Koo, Reginald

2008-01-01

74

LTU Physlet: Ladder Leaning Against a Wall  

Science.gov (United States)

This Java Applet simulates the well-known "leaning ladder" physics problem. It consists of a ladder leaning against a wall and a person standing on the ladder (represented by a blue ball). The user can adjust mass of ladder, mass of person, distance person stands from base of ladder, coefficient of static friction underneath ladder, and the theta angle. Force vectors and values are shown for the lateral force and force of static friction on the base of the ladder. The ladder will fall if the lateral is greater than the frictional force. This is part of a larger collection of Physlet-based tutorials developed at Lawrence Technological University to support instruction of introductory physics.

Schneider, Scott

2011-09-02

75

Semiclassical description of spin ladders  

CERN Document Server

The Heisenberg spin ladder is studied in the semiclassical limit, via a mapping to the nonlinear \\sigma model. Different treatments are needed if the inter-chain coupling K is small, intermediate or large. For intermediate coupling a single nonlinear \\sigma model is used for the ladder. Its predicts a spin gap for all nonzero values of K if the sum s+\\tilde s of the spins of the two chains is an integer, and no gap otherwise. For small K, a better treatment proceeds by coupling two nonlinear sigma models, one for each chain. For integer s=\\tilde s, the saddle-point approximation predicts a sharp drop in the gap as K increases from zero. A Monte-Carlo simulation of a spin 1 ladder is presented which supports the analytical results.

Sénéchal, D

1995-01-01

76

Transformations of triangle ladder diagrams  

CERN Multimedia

It is shown how dual space diagrammatic representation of momentum integrals corresponding to triangle ladder diagrams with an arbitrary number of rungs can be transformed to half-diamonds. Acting in the way described in this paper we do not need to use diamond (four-point) diagrams as an intermediate step in deriving relations of arXiv:0803.3420 [hep-th]. In that paper the half-diamonds were related by conformal integral substitution to the diamonds. As is known, the diamonds represent the dual space image of four-point ladder integrals in the four-dimensional momentum space.

Kondrashuk, Igor

2009-01-01

77

Laddering em pesquisa de marketing Laddering in marketing research  

Directory of Open Access Journals (Sweden)

Full Text Available O artigo discute a técnica de pesquisa laddering em marketing, considerando a proposta de renovação de conhecimentos sobre metodologia na área. Para isso investiga diversos estudos, artigos e pesquisas que tratam do assunto em nível nacional e internacional. O conceito de cadeias meios-fins é abordado pela estrutura teórica que fundamenta a técnica, ligando atributos, conseqüências percebidas do consumo e valores pessoais relativos a um produto. O artigo segue com a explicação dos procedimentos de campo, como a entrevista e a análise dos dados. A laddering é um instrumento de pesquisa qualitativa bastante útil e poderoso, mas ainda pouco utilizado tanto por acadêmicos como por profissionais de mercado, no Brasil, provavelmente por desconhecimento e pouca divulgação. Cabe, portanto, uma maior disseminação de seu uso.The objective of this paper is to discuss laddering technique in marketing, considering the proposal of renewing knowledge on research methodology. It investigates national and international studies, articles, and researches that approach the subject. The means-end theory that grounds the technique, linking attributes, consequences and values related to a product, is presented in the article. Common practices in the field research are presented as well, emphasizing data collection and analysis. Although very powerful, laddering is still underutilized for both academics and practitioners, probably for lacking of knowledge and dissemination. It is important to propagate the use of this technique in academic and market researches.

Tânia Modesto Veludo-de-Oliveira; Ana Akemi Ikeda

2008-01-01

78

Laddering em pesquisa de marketing/ Laddering in marketing research  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese O artigo discute a técnica de pesquisa laddering em marketing, considerando a proposta de renovação de conhecimentos sobre metodologia na área. Para isso investiga diversos estudos, artigos e pesquisas que tratam do assunto em nível nacional e internacional. O conceito de cadeias meios-fins é abordado pela estrutura teórica que fundamenta a técnica, ligando atributos, conseqüências percebidas do consumo e valores pessoais relativos a um produto. O artigo segue c (more) om a explicação dos procedimentos de campo, como a entrevista e a análise dos dados. A laddering é um instrumento de pesquisa qualitativa bastante útil e poderoso, mas ainda pouco utilizado tanto por acadêmicos como por profissionais de mercado, no Brasil, provavelmente por desconhecimento e pouca divulgação. Cabe, portanto, uma maior disseminação de seu uso. Abstract in english The objective of this paper is to discuss laddering technique in marketing, considering the proposal of renewing knowledge on research methodology. It investigates national and international studies, articles, and researches that approach the subject. The means-end theory that grounds the technique, linking attributes, consequences and values related to a product, is presented in the article. Common practices in the field research are presented as well, emphasizing data c (more) ollection and analysis. Although very powerful, laddering is still underutilized for both academics and practitioners, probably for lacking of knowledge and dissemination. It is important to propagate the use of this technique in academic and market researches.

Veludo-de-Oliveira, Tânia Modesto; Ikeda, Ana Akemi

2008-03-01

79

Technological innovation in railway structure system with ladder sleeper; Ladder makuragi no kaihatsu to senro kozobutsu no system change  

Energy Technology Data Exchange (ETDEWEB)

The ladder sleeper developed by Railway Technical Research Institute is a next-generation rail supporting component of the longitudinal sleeper type. The concrete-made longitudinal left-side and right-side beams, parallelly arranged, are connected with each other by steel-made joining pipes, and consequently assume a ladder-like external appearance. Since the concrete-made longitudinal beams are so designed as to support and restrain the rails continuously, it may be said that the result is a `composite rail` with a superior load carrying capacity and high lateral track stability. The ballasted ladder tracks are expected to suffer less from deterioration to be caused by worn ballast. The floating ladder tracks will be a technological breakthrough in the field of non-ballasted tracks, to eventually replace the conventional slab tracks. The floating ladder tracks will enable the construction of innovative type viaducts excellent in cost performance, friendliness towards environments, and resistance to earthquake. It is expected that the new system upon adoption will bring about a great progress in the railway business. 35 refs., 24 figs.

Wakui, H. [Railway Technical Research Institute, Tokyo (Japan)

1998-05-01

80

Absolute feeding design, a realistic way for fish nutrients requirements determination Methodology for determination of nutrient requirements in fish  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Feeding experiment is designed on the basis of food allowance rather than feed formulation. Food allowances are fixed in the attempt to provide the desired amount of nutricients per body mass of fish per day (in terms of g.kg-1.d-1 or J.kg-1.d-1). By this way, previous determination of optimum feedi...

Moreau, Yann; Cissé, A.; Luquet, Pierre

 
 
 
 
81

Shaft door with folding ladder  

International Nuclear Information System (INIS)

[en] A shaft door is patented with a folding ladder which may easily be opened from the top and bottom of the shaft. It excludes the opening of the door by falling objects which improves work safety. This door is suitable for access shafts to biological protective cabins for repairs and maintenance inside nuclear reactors and for other purposes. (Ha)

1979-06-16

82

Ladder-Type Circuits Revisited  

Science.gov (United States)

Ladder-type circuits where a given unit is repeated infinitely many times are dealt with in many textbooks on electromagnetism as examples of filter circuits. Determining the impedance of such circuits seems to be regarded as simple, which may be due to the fact that the invariance of the infinite system under the operation of adding one more unit…

Yoon, Sung Hyun

2007-01-01

83

[Factors of influence on willingness to participate in the N3 nursing clinical ladder program].  

UK PubMed Central (United Kingdom)

BACKGROUND: The professional nursing clinical ladder program can effectively enhance the professional morale of nursing staff and help retain the best senior nurses in clinical settings. Hence, it is important to explore factors that influence nurse staff intentions to participate in the clinical ladder. PURPOSE: This study examined factors that affect nurse staff intention to participate in the N3 nurse clinical ladder program. METHODS: We used a cross sectional study design and a structured questionnaire survey. We employed purposive sampling to recruit 389 nurse staffs qualified for promotion to the N3 level from a medical center in southern Taiwan. RESULTS: Findings showed: (1) Nearly two-thirds (233, 59.9%) of participants intended to participate in clinical ladder; (2) The factors of age, years of nursing experience, years in current position, project/research experience, promotion experience, and intention all significantly affected intent to participate in the ladder; (3) A significant difference between willingness to participate in the ladder program and each of the following variables--motivation, satisfaction, professional capacity, and sense of achievement; (4) Logistic regression analysis identified only motivation as a valid predictor of willingness to participate the ladder program (95% CI: 1.21-3.78). CONCLUSION/IMPLICATIONS FOR PRACTICE: Results provide a useful reference to nursing administrators for planning on-the-job training and increasing nurse staff participation in the ladder. The authors hope results can help promote better human resource management and achievements.

Li YH; Lin LD; Tsai CC; Chou MC; Lin MH

2012-02-01

84

Stakeholder participation in research design and decisions: scientists, fishers, and mercury in saltwater fish.  

UK PubMed Central (United Kingdom)

Individuals who fish and eat self-caught fish make decisions about where to fish, the type to eat, and the quantity to eat. Federal and state agencies often issue consumption advisories for some fish with high mercury (Hg) concentrations, but seldom provide either the actual metal levels to the general public, or identify the fish that have low contaminant levels. Community participatory research is of growing importance in defining, studying, and resolving complex exposure and risk issues, and this paper is at the intersection of traditional stakeholder approaches and community-based participatory research. The objective of this paper is to describe the process whereby stakeholders (fishers), were involved in directing and refining research questions to address their particular informational needs about mercury levels in fish, potential risks, and methods to maintain health, by balancing the risks and benefits of fish consumption. A range of stakeholders, mainly individual fishers, fishing organizations, and other scientists, were involved at nearly every stage. Community participants influenced many aspects of the design and implementation of the research, in the determination of which fish species to sample, in the collection of the samples, and in the final analyses and synthesis, as well as the communication of results and implications of the research through their fishing club publications, talks and gatherings. By involving the most interested and affected communities, the data and conclusions are relevant to their needs because the fish examined were those they ate and wanted information about, and directly address concerns about the risk from consuming self-caught fish. Although mercury levels in fish presumed to be high in mercury are known, little information was available to the fishermen on mercury levels in fish that were low and thus provided little risk to their families. While community participatory research is more time-consuming and expensive than traditional scientific research, both the process and results are better scientifically in terms of community relevance.

Burger J; Gochfeld M; Fote T

2013-03-01

85

D0 Silicon Upgrade: Thermally Induced Bowing in a 3-CHIP Ladder  

Energy Technology Data Exchange (ETDEWEB)

The end of the 3 chip ladder, shown below, consists of silicon mounted on a piece of beryllium which is adhered to the cooling channel. Outboard of the cooling channel is a region of ladder composed primarily of silicon/beryllium. Operation and cooling of the ladder results in a change in temperature from the assembly temperature, which will result in deflections due to the difference in expansion coefficients of the two materials, otherwise known as 'bi-metal' bowing. The goal of this note is to present a design of the beryllium plate on the underside of the ladder which reduces the thermally induced bow to a reasonable deflection. This region of ladder will see a fairly large temperature gradient during detector operation due to the heat load of the transceivers on the ladder end. Expected temperatures range between 22 C on the ladder end to 9.5 C near the cooling channel for a coolant temperature of 5 C. The coolant temperature may be as low as -5 C, so we may estimate a lower limit on the ladder temperatures to be 10 C cooler, ranging from 12 C on the ladder end to -0.5 C near the bulkhead (assumes negligible convection from the ladder surface). With a ladder assembly temperature of 23 C we may estimate the end deflection of the ladder based on the assumed temperatures during operation by applying Roark equation 6a. Equation 6a describes end deflection for a cantilever beam under application of a uniform temperature change. The equation is modified to account for a uniform temperature gradient along the bi-metal region. The equation is differentiated twice, the assumed temperature dependence is plugged, and the equation is re-integrated twice. deflection = C*{Delta}T*L{sup 2}. The constant C is a function of material thicknesses and moduli. The composite region (beryllium and silicon 'bi-metal' region) is between 21.0 and 25.0 mm in length (the HDI design is still in progress) plus the additional 1.975 mm shown in the ladder drawing below. Hence, the composite region is assumed to extend 27 mm beyond the bulkhead ledge. The silicon extends 4 mm beyond the composite region. Deflection of the ladder end, the silicon, is calculated.

Ratzmann, Paul; /Fermilab

1994-08-22

86

Convergent validation study of the Contemplation Ladder for application via telephone in tobacco users Estudo da validação convergente da Escala de Contemplação Ladder aplicada por telefone em tabagistas  

Directory of Open Access Journals (Sweden)

Full Text Available OBJECTIVE: This work was designed to validate the Portuguese version of the Contemplation Ladder, whose purpose is to assess the motivational phase to quit smoking among tobacco users using a telephone service. METHOD: A cross-sectional study was conducted in a nationwide drug use information hotline. In order to assess the convergent validation, the correlation between the Contemplation Ladder and the URICA Scale was calculated, which was previously validated. RESULTS: The study included 271 tobacco users. Statistically significant correlations were found between the Contemplation Ladder scores and the scores of the URICA precontemplation (r=-0.16; pOBJETIVO: Este estudo teve como objetivo validar a versão em português da Escala de Contemplação Ladder, que visa verificar o estágio motivacional para parar de fumar em tabagistas, em um serviço de atendimento telefônico. MÉTODO: Um estudo transversal foi conduzido em um serviço de âmbito nacional de informação sobre uso de drogas por telefone. Para avaliação da validação convergente foi calculada a correlação entre a Escala de Contemplação Ladder e a Escala URICA, a qual já foi validada anteriormente. RESULTADOS: O estudo incluiu 271 tabagistas. Foram encontradas correlações estatisticamente significativas entre os escores da Escala de Contemplação Ladder e os escores das subescalas de pré-contemplação (r=-0,16; p<0,01), ação (r=0,15; p<0,01) e manutenção (r=0,18; p<0,01) da URICA. A correlação entre o escore composto da Escala URICA e a Escala de Contemplação Ladder também foi significativa (r=0,31; p<0,01). CONCLUSÃO: Os resultados do nosso estudo sugerem que a Escala de Contemplação Ladder pode ser uma alternativa para a Escala URICA (cuja aplicação dura no máximo 20 minutos), sem se impor uma carga maior de perguntas ao entrevistado. O estudo mostrou evidências de validade convergente da Escala de Contemplação Ladder, quando aplicada por telefone, em usuários de tabaco.

Mauro Barbosa Terra; Dartiu Xavier da Silveira; Taís de Campos Moreira; Maristela Ferigolo; Claudia Mazoni; Fernanda Xavier Arena; Helena Maria Tannhauser Barros

2009-01-01

87

Sampling designs and methods for estimating fish-impingement losses at cooling-water intakes  

International Nuclear Information System (INIS)

Several systems for estimating fish impingement at power plant cooling-water intakes are compared to determine the most statistically efficient sampling designs and methods. Compared to a simple random sampling scheme the stratified systematic random sampling scheme, the systematic random sampling scheme, and the stratified random sampling scheme yield higher efficiencies and better estimators for the parameters in two models of fish impingement as a time-series process. Mathematical results and illustrative examples of the applications of the sampling schemes to simulated and real data are given. Some sampling designs applicable to fish-impingement studies are presented in appendixes

1977-01-01

88

Optical absorption of spin ladders  

CERN Document Server

We present a theory of phonon-assisted optical two-magnon absorption in two-leg spin-ladders. Based on the strong intra-rung-coupling limit we show that collective excitations of total spin S=0, 1 and 2 exist outside of the two-magnon continuum. It is demonstrated that the singlet collective state has a clear signature in the optical spectrum.

Jurecka, C

1999-01-01

89

Design complexity in termite-fishing tools of chimpanzees (Pan troglodytes).  

UK PubMed Central (United Kingdom)

Adopting the approach taken with New Caledonian crows (Corvus moneduloides), we present evidence of design complexity in one of the termite-fishing tools of chimpanzees (Pan troglodytes) in the Goualougo Triangle, Republic of Congo. Prior to termite fishing, chimpanzees applied a set of deliberate, distinguishable actions to modify herb stems to fashion a brush-tipped probe, which is different from the form of fishing tools used by chimpanzees in East and West Africa. This means that 'brush-tipped fishing probes', unlike 'brush sticks', are not a by-product of use but a deliberate design feature absent in other chimpanzee populations. The specialized modifications to prepare the tool for termite fishing, measures taken to repair non-functional brushes and appropriate orientation of the modified end suggest that these wild chimpanzees are attentive to tool modifications. We also conducted experimental trials that showed that a brush-tipped probe is more effective in gathering insects than an unmodified fishing probe. Based on these findings, we suggest that chimpanzees in the Congo Basin have developed an improved fishing probe design.

Sanz C; Call J; Morgan D

2009-06-01

90

Exactly solvable quantum spin tubes and ladders  

CERN Document Server

We find families of integrable n-leg spin-1/2 ladders and tubes with general isotropic exchange interactions between spins. These models are equivalent to su(N) spin chains with N=2^n. Arbitrary rung interactions in the spin tubes and ladders induce chemical potentials in the equivalent spin chains. The potentials are n-dependent and differ for the tube and ladder models. The models are solvable by means of nested Bethe Ansatz.

Batchelor, M T

1999-01-01

91

The reconstructive microsurgery ladder in orthopaedics.  

UK PubMed Central (United Kingdom)

Since the advent of the operating microscope by Julius Jacobson in 1960, reconstructive microsurgery has become an integral part of extremity reconstruction and orthopaedics. During World War I, with the influx of severe extremity trauma Harold Gillies introduced the concept of the reconstructive ladder for wound closure. The concept of the reconstructive ladder goes from simple to complex means of attaining wound closure. Over the last half century microsurgery has continued to evolve and progress. We now have a microsurgical reconstructive ladder. The microsurgical reconstruction ladder is based upon the early work on revascularization and replantation extending through the procedures that are described in this article.

Tintle SM; Levin LS

2013-01-01

92

Design of LED fish lighting attractors using horizontal/vertical LIDC mapping method.  

Science.gov (United States)

This study employs a sub-module concept to develop high-brightness light-emitting diode (HB-LED) fishing light arrays to replace traditional fishing light attractors. The horizontal/vertical (H/V) plane light intensity distribution curve (LIDC) of a LED light source are mapped to assist in the design of a non-axisymmetric lens with a fish-attracting light pattern that illuminates sufficiently large areas and alternates between bright and dark. These LED fishing light attractors are capable of attracting schools of fish toward the perimeter of the luminous zone surrounding fishing boats. Three CT2 boats (10 to 20 ton capacity) were recruited to conduct a field test for 1 y on the sea off the southwestern coast of Taiwan. Field tests show that HB-LED fishing light array installed 5 m above the boat deck illuminated a sea surface of 5 × 12 m and achieved an illuminance of 2000 lx. The test results show that the HB-LED fishing light arrays increased the mean catch of the three boats by 5% to 27%. In addition, the experimental boats consumed 15% to 17% less fuel than their counterparts. PMID:23187469

Shen, S C; Huang, H J

2012-11-19

93

Design of LED fish lighting attractors using horizontal/vertical LIDC mapping method.  

UK PubMed Central (United Kingdom)

This study employs a sub-module concept to develop high-brightness light-emitting diode (HB-LED) fishing light arrays to replace traditional fishing light attractors. The horizontal/vertical (H/V) plane light intensity distribution curve (LIDC) of a LED light source are mapped to assist in the design of a non-axisymmetric lens with a fish-attracting light pattern that illuminates sufficiently large areas and alternates between bright and dark. These LED fishing light attractors are capable of attracting schools of fish toward the perimeter of the luminous zone surrounding fishing boats. Three CT2 boats (10 to 20 ton capacity) were recruited to conduct a field test for 1 y on the sea off the southwestern coast of Taiwan. Field tests show that HB-LED fishing light array installed 5 m above the boat deck illuminated a sea surface of 5 × 12 m and achieved an illuminance of 2000 lx. The test results show that the HB-LED fishing light arrays increased the mean catch of the three boats by 5% to 27%. In addition, the experimental boats consumed 15% to 17% less fuel than their counterparts.

Shen SC; Huang HJ

2012-11-01

94

A Ladder of Thinking  

Science.gov (United States)

Introducing students to metacognition, or thinking about one's thinking, allows them to discover the value of reflection. Courses related to thinking theory are often included in the curriculum for high-achieving students, but these methods can also be used effectively to enhance the learning of average or below-average students. This article presents a lesson on top-down and bottom-up processing, two of the main ways in which people handle information. It is designed to help students understand why they should proceed slowly and deliberately when making observations in a science lab or when answering questions on a test.

Lovrich, Deborah

2004-04-01

95

Convergent validation study of the Contemplation Ladder for application via telephone in tobacco users/ Estudo da validação convergente da Escala de Contemplação Ladder aplicada por telefone em tabagistas  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese OBJETIVO: Este estudo teve como objetivo validar a versão em português da Escala de Contemplação Ladder, que visa verificar o estágio motivacional para parar de fumar em tabagistas, em um serviço de atendimento telefônico. MÉTODO: Um estudo transversal foi conduzido em um serviço de âmbito nacional de informação sobre uso de drogas por telefone. Para avaliação da validação convergente foi calculada a correlação entre a Escala de Contemplação Ladder e a (more) Escala URICA, a qual já foi validada anteriormente. RESULTADOS: O estudo incluiu 271 tabagistas. Foram encontradas correlações estatisticamente significativas entre os escores da Escala de Contemplação Ladder e os escores das subescalas de pré-contemplação (r=-0,16; p Abstract in english OBJECTIVE: This work was designed to validate the Portuguese version of the Contemplation Ladder, whose purpose is to assess the motivational phase to quit smoking among tobacco users using a telephone service. METHOD: A cross-sectional study was conducted in a nationwide drug use information hotline. In order to assess the convergent validation, the correlation between the Contemplation Ladder and the URICA Scale was calculated, which was previously validated. RESULTS: T (more) he study included 271 tobacco users. Statistically significant correlations were found between the Contemplation Ladder scores and the scores of the URICA precontemplation (r=-0.16; p

Terra, Mauro Barbosa; Silveira, Dartiu Xavier da; Moreira, Taís de Campos; Ferigolo, Maristela; Mazoni, Claudia; Arena, Fernanda Xavier; Barros, Helena Maria Tannhauser

2009-01-01

96

Cutting and dismantling of the South West ladder of the Atucha I nuclear power plant  

International Nuclear Information System (INIS)

The metallic ladder built in stainless steel was used originally to check the welding of the reactor pressure vessel. It was located between the thermal insulation and reactor pressure vessel. Because of a failure in the mechanism, which let the ladder runs around the vessel, it had to be removed. A special tool remotely operated was designed to make different cuts in the bottom of the structure in a very high radioactive location.

2006-01-01

97

Revisiting the Ladder on a Wall Problem  

Science.gov (United States)

The problem of a ladder leaning on a wall has been a staple of introductory physics for years. It is discussed in numerous physics textbooks and in journals. Now, it even has an Internet presence. Postings from students seek help for "ladder on a wall" problems. A quick review of those postings would show that they all deal with frictionless…

Salu, Yehuda

2011-01-01

98

Elementary systems with partial finite ladder spectra  

International Nuclear Information System (INIS)

It is shown that a subset of the kth-order supersymmetric partners of the harmonic oscillator admits third-order ladder operators, and provides a realization of second-order polynomial Heisenberg algebras. The corresponding spectra are composed of an infinite ladder of equally spaced energy levels and a finite one with k levels.

2004-04-12

99

Perspective on rainbow-ladder truncation  

International Nuclear Information System (INIS)

Prima facie the systematic implementation of corrections to the rainbow-ladder truncation of QCD's Dyson-Schwinger equations will uniformly reduce in magnitude those calculated mass-dimensioned results for pseudoscalar and vector meson properties that are not tightly constrained by symmetries. The aim and interpretation of studies employing rainbow-ladder truncation are reconsidered in this light.

2008-01-01

100

Nonlinear delocalization on disordered Stark ladder  

CERN Document Server

We study effects of weak nonlineary on localization of waves in disordered Stark ladder corresponding to propagation in presence of disorder and a static field. Our numerical results show that nonlinearity leads to delocalization with subdiffusive spreading along the ladder. The exponent of spreading remains close to its value in absence of the static field.

Garcia-Mata, Ignacio

2009-01-01

 
 
 
 
101

Make a Human Scale Ladder  

Science.gov (United States)

In this quick activity about size and scale (on page 2 of the PDF), each learner will be given an image of an object and communicate with other members of the group to arrange the objects they are holding in order of size (largest objects on one end and smallest on the other). Scale ladders help kids recognize the order of magnitude of some benchmark objects and correctly arrange them in order of size. This exercise also increases familiarity with the metric system, the universal language used by scientists, and some common prefixes such as "micro" and "nano." Also relates to linked video, DragonflyTV Nano: What's Nano?

Twin Cities Public Television, Inc.

2008-01-01

102

Design and Development of Wireless Sensor Network System to Monitor Parameters Influencing Freshwater Fishes  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we have designed, developed and proposed a prototype Wireless Sensor Network (WSN) System to monitor the Fish Farm. Salinity of the fresh water is a prominent parameter and isresponsible for the difference in environment from marine conditions. Salt is an effective ingredient for fishes in fighting disease, parasites and chemical poisoning. The pH is equally a key parameter which influences the environment where fishes live. Generally, the fishes can live in pH ranges from 6.0 to 9.0, but their quality of life is best between pH 7.0 to 8.0. The change in the value of pH even by a small amount will be more stressful for fish. The temperature is other parameter which decides the value of pHand in turn affects the fishes. The developed prototype WSN system monitors these three parameters affecting the fresh water fishes. The open source technology-ARDUINO (open electronics prototype andopen source) is used to develop the system.

Santoshkumar; Vishal Hiremath

2012-01-01

103

Failure of the ladder approximation to QCD  

Energy Technology Data Exchange (ETDEWEB)

The proof of the failure of the ladder approximation to QCD is given in manifestly gauge-invariant way. This proof is valid for the full gluon propagator and for all types of quarks. The summation of the ladder diagrams within the Schwinger-Dyson integral equation for the quark-gluon vertex, on account of the corresponding Slavnov-Taylor identity, provides an additional constraint on the quark Schwinger-Dyson equation itself in the ladder approximation. It requires that there is neither running nor current quark masses in the ladder approximation. Thus, all the results based on the nontrivial (analytical or numerical) solutions to the quark Schwinger-Dyson equation in the ladder approximation should be reconsidered, and its use in the whole energy/momentum range should be abandoned.

Gogohia, V. [HAS, CRIP, RMKI, Department of Theoretical Physics, PO Box 49, H-1525 Budapest 114 (Hungary)]. E-mail: gogohia@rmki.kfki.hu

2005-03-31

104

Development of Ladder Climbing Robot LCR-1  

International Nuclear Information System (INIS)

A new mobile robot has been developed, which is capable of ascending and descending vertical ladders such as those used in nuclear power plants and other facilities. The Ladder Climbing Robot releases personnel from dangerous and hard work at high places. The body of the robot has four grippers which grip each rung of the ladder as it ascends or descends. Each gripper is able to move up, down, forward or backward, and has two kinds of sensors to detect a rung: one photoelectric-switch and the other limit-switch. This robot can operate automatically or be remote controlled. Three of the grippers are continuously in contact with the ladder rungs to prevent falling. As a result of experiment, it has been confirmed that the prototype model LCR-1 for trial can ascend and descend automatically the actual vertical ladder with a micro-computer on the body. (author).

1985-01-01

105

Wheel shield and ladder for a spray vehicle  

UK PubMed Central (United Kingdom)

A combination wheel shield and ladder for an agricultural vehicle such as a sprayer includes a deformable plastic body with a profile designed to control the path of deflection and to return the body to original shape after deflection. The shield is mounted on a steel framework also designed to help control deflection and assure return to the original shape. A bail limits maximum shield deflection and increases the strength of the framework. A ladder is incorporated into a plastic wheel shield extension A combination handle-step structure located above the wheel and special platform structure located on the drop axle provide convenient access to the operator's station for all adjusted positions of the drop axle.

ZAUN RICHARD D; PEARSON MICHAEL L

106

Fish schooling as a basis for wind farm design  

Science.gov (United States)

It is known that horizontal axis wind turbines (HAWT) suffer from reduced aerodynamic efficiency when in close proximity to neighboring turbines. In contrast, recent work has shown that closely spaced vertical axis wind turbines (VAWT) may benefit from enhanced performance, reducing the associated land use for VAWT wind farm installations. A potential flow model of VAWT interactions is developed to determine configurations that optimize the power output of the array. A geometric arrangement based on fish schooling has been shown to significantly increase the array performance as measured by an Array Power Coefficient, which compares the average performance of turbines in the array to an isolated turbine. The results suggest that significant gains may be obtained through careful arrangement of VAWTs, showing up to a two order of magnitude decrease in land use (equivalently, a two order of magnitude increase in power density) compared to HAWTs.

Whittlesey, Robert; Dabiri, John

2009-11-01

107

Exactly solvable su(N) mixed spin ladders  

CERN Multimedia

It is shown that solvable mixed spin ladder models can be constructed from su(N) permutators. Heisenberg rung interactions appear as chemical potential terms in the Bethe Ansatz solution. Explicit examples given are a mixed spin-1/2 spin-1 ladder, a mixed spin-1/2 spin-3/2 ladder and a spin-1 ladder with biquadratic interactions.

Batchelor, M T; Maslen, M

2000-01-01

108

Polaron delocalization in ladder macromolecular systems.  

UK PubMed Central (United Kingdom)

Organic macromolecules with conjugated building blocks have been the focus of extensive research that is motivated, in part, by the potential to create optical and electronic devices. We have shown that palladium-catalyzed amination can assemble triarylamine ladder materials with extended structures. Two ladder macromolecules have been prepared in high yields by a series of twelve or sixteen C-N coupling reactions. Studies of the electronic and optical properties of neutral and oxidized forms of the ladder structures were conducted. The optical and electronic properties of the ladder systems are compared to those of the linear tetra-phenyl-p-phenylenediamine as well as the tetra-p-anisyl-p-tetraazacyclophane. The electrochemistry of the ladder systems consists of a multiwave voltammogram with a relatively low first oxidation potential. Electron paramagnetic resonance spectroscopy of the ladder systems suggests the presence of a large density of delocalized polarons. Linear absorption measurements of the chemically oxidized ladders revealed both polaron and intervalence absorption bands. Steady-state and time-resolved fluorescence measurements were also carried out to characterize the dynamics in these novel systems.

Yan XZ; Pawlas J; Goodson T 3rd; Hartwig JF

2005-06-01

109

Polaron delocalization in ladder macromolecular systems.  

Science.gov (United States)

Organic macromolecules with conjugated building blocks have been the focus of extensive research that is motivated, in part, by the potential to create optical and electronic devices. We have shown that palladium-catalyzed amination can assemble triarylamine ladder materials with extended structures. Two ladder macromolecules have been prepared in high yields by a series of twelve or sixteen C-N coupling reactions. Studies of the electronic and optical properties of neutral and oxidized forms of the ladder structures were conducted. The optical and electronic properties of the ladder systems are compared to those of the linear tetra-phenyl-p-phenylenediamine as well as the tetra-p-anisyl-p-tetraazacyclophane. The electrochemistry of the ladder systems consists of a multiwave voltammogram with a relatively low first oxidation potential. Electron paramagnetic resonance spectroscopy of the ladder systems suggests the presence of a large density of delocalized polarons. Linear absorption measurements of the chemically oxidized ladders revealed both polaron and intervalence absorption bands. Steady-state and time-resolved fluorescence measurements were also carried out to characterize the dynamics in these novel systems. PMID:15969589

Yan, X Z; Pawlas, J; Goodson, T; Hartwig, J F

2005-06-29

110

Random sequential adsorption on a ladder  

Energy Technology Data Exchange (ETDEWEB)

The authors study the asymptotic coverage of a lattice to which particles are randomly and irreversibly attached, under the constraint of nearest neighbor exclusion. After reviewing the case of a one-dimensional lattice, they extend the treatment first to a triangular ladder and then to a square ladder. The former maps onto a previously solved one-dimensional case, the latter does not. They also determine the time-dependent coverage of the square ladder. Implications as to the process on a full 2-dimensional square lattice are discussed.

Fan, Y.; Percus, J.K. (New York Univ., New York (United States))

1992-01-01

111

Centipede ladder at quarter filling  

CERN Multimedia

We study the ground state and excitation spectrum of a quasi one-dimensional nanostructure consisting of a pole and rungs oriented in the opposite directions ("centipede ladder", CL) at quarter filling. The spin and charge excitation spectra are found in the limits of small and large longitudinal hopping $t_\\|$ compared to the on-rung hopping rate $t_\\perp$ and exchange coupling $I_\\perp$. At small $t_\\|$ the system with ferromagnetic on-rung exchange demonstrates instability against dimerization. Coherent propagation of charge transfer excitons is possible in this limit. At large $t_\\|$ CL behaves like two-orbital Hubbard chain, but the gap opens in the charge excitation spectrum thus reducing the symmetry from SU(4) to SU(2). The spin excitations are always gapless and their dispersion changes from quadratic magnon-like for ferromagnetic on-rung exchange to linear spinon-like for antiferromagnetic on-rung exchange in weak longitudinal hopping limit.

Aristov, D N; Kikoin, K

2007-01-01

112

Salmon jumping: behavior, kinematics and optimal conditions, with possible implications for fish passageway design  

International Nuclear Information System (INIS)

[en] Behavioral and kinematic properties and capacities of wild migratory salmonid fishes swimming upstream and jumping up waterfalls generally have played only minor roles in the design and construction of passageways intended to help these fishes get past dams and other human-made obstacles blocking their movements. This paper reports the results of an experimental study of relevant behavioral and kinematic properties of adult kokanee salmon (Oncorhynchus nerka) jumping up waterfalls as they migrate upstream. We used a portable, adjustable apparatus to study in the field fish responding to artificial waterfalls under a range of flow conditions. We observed fish under conditions of varying water flow rates, pool depths, fall heights and fall angles. We analyzed digital video recordings of their behaviors. Kokanee salmon spontaneously jump up waterfalls within a relatively narrow range of conditions, including low flow speeds, near vertical angles and pool depth to fall height ratios near 1.0. Preferred values for each parameter are, to some extent, dependent on other parameters. In contrast to previous misconceptions, jumping behavior is initiated by running S-start accelerations from beneath the boils formed in the plunge pools below waterfalls, as opposed to C-start standing jumps from the surface. S-starts are immediately followed by burst swimming to the point of takeoff at the surface. These results can contribute to an improved basis for developing designs of fish passageways that may ultimately make them more effective and efficient.

2010-01-01

113

Magnetic order in ferromagnetically coupled spin ladders  

CERN Multimedia

A model of coupled antiferromagnetic spin-1/2 Heisenberg ladders is studied with numerical techniques. In the case of ferromagnetic interladder coupling we find that the dynamic and static structure factor has a peak at $(\\pi,\\pi/2)$ where the first (second) direction is along (transversal) to the ladders. Besides, we suggest that the intensity of this peak and the spin-spin correlation at the maximum distance along the ladder direction remain finite in the bulk limit for strong enough interladder coupling. We discuss the relevance of these results for magnetic compounds containing ladders coupled in a trellis lattice and for the stripe scenario in high-T$_c$ superconducting cuprates.

Dalosto, S D

1999-01-01

114

Hilbert Functions Of Ladder Determinantal Varieties  

UK PubMed Central (United Kingdom)

We consider algebraic varieties defined by the vanishing of all minors of a fixed size of a rectangular matrix with indeterminate entries such that the indeterminates in these minors are restricted to lie in a ladder shaped region of the rectangular array. Explicit formulae for the Hilbert function of such varieties are known in (i) the rectangular case [Abhyankar, 1984], and (ii) the case of 2 × 2 minors in one-sided ladders [Kulkarni, 1985]. More recently, Krattenthaler and Prohaska (1999) have proved a `remarkable formula', conjectured by Conca and Herzog (1994) for the Hilbert series in the case of arbitrary sized minors in one-sided ladders. We describe here an explicit, albeit complicated, formula for the Hilbert function and the Hilbert series in the case of arbitrary sized minors in two-sided ladders. From a combinatorial viewpoint, this is equivalent to the enumeration of certain sets of `indexed monomials'.

Sudhir R. Ghorpade

115

Ladder operators for the associated Laguerre functions  

International Nuclear Information System (INIS)

Introducing the associated Laguerre functions in terms of two non-negative integers, we obtain simultaneously and separately realization of the laddering equations with respect to each of the integers by means of two pairs of ladder operators. Besides, two different types of shape-invariance symmetries are realized. This approach leads to a derivation of shape-invariance equations of third type which are realized by two simultaneous raising and lowering operators of two parameters.

1939-01-00

116

Design and Development of an Innovative Mobile Fish Vending Unit for Retailers  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this study was to design and develop a low cost mobile fish vending unit in urban/municipality areas with proper waste disposal. The prototype model was designed and fabricated using locally available materials at a cost of Rs.52780/-. The main feature of this prototype is that its100 and 70 L insulated chilled crates; utility box; Cutting and processing area; storage of water and waste disposal. Necessary effort has been made to maintain the possible market quality of fish and fish products in the form of raw and semi-processed/processed chilled products. Test trial of ergonomics evaluation indicated that the working heart rate (HR work) of the male operator ranged from 123.8 to 134 beats/min with a mean value of 131.9 ± 1.6 beats/min. The corresponding values with women were 119.0 to 149.6 and 131.2 ± 1.0 beats/min, respectively. The heart rate was lower with male as compared to the female. The forces on the pedal are 161.84 N and 377.6 N in case of first and second condition. The calculated mechanical advantages for first and second condition are 0.278 and 0.276, respectively. The design of mobile fish vending unit is stable. The operators both male and female have found the unit to be conducive both in terms of ergonomically as well as operationally.

Bikash Sarkar; B.B.Sahu; B.C.Mohapatra; N.K.Barik,; D.Majhi; P. Jayasankar,; P.R.Bhatnagar

2013-01-01

117

Evaluation of Juvenile Fish Bypass and Adult Fish Facilities at Water Diversions in the Umatilla River; 1992 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

We report on our progress from October 1991 through September 1992 in evaluating juvenile fish bypass facilities at Three Mile Falls and Westland dams on the Umatilla River. We also report on our progress from October 1991 through June 1992 in evaluating adult fish passage in the lower Umatilla River and adult fish passage facilities at Three Mile Falls Dam. The study is a cooperative effort by the Oregon Department of Fish and Wildlife (ODFW) and the Confederated Tribes of the Umatilla Indian Reservation (CTUIR). These are the study objectives addressed by ODFW and CTUIR: (1) Report A (ODFW): To evaluate the juvenile fish bypass facility in the West Extension Irrigation District Canal at Three Mile Falls Dam and document juvenile salmonid passage through the juvenile fish bypass facility and east-bank adult fish ladder. To measure velocity and develop trap designs at Westland Dam. (2) Report B (CTUIR): To examine the passage of adult salmonids at Three Mile Falls Dam. The study is part of a program to rehabilitate anadromous fish stocks in the Umatilla River Basin, including restoration of coho salmon (Oncorhynchus kisutch) and chinook salmon (Oncorhynchus tshawytscha), as well as enhancement of summer steelhead (Oncorhynchus mykiss).

Knapp, Suzanne M.

1993-03-01

118

Walla Walla River Fish Passage Operations Program, 2004-2005 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

In the late 1990s, the Confederated Tribes of the Umatilla Indian Reservation, Oregon Department of Fish and Wildlife, and Washington Department of Fish and Wildlife, along with many other agencies, began implementing fisheries restoration activities in the Walla Walla Basin. An integral part of these efforts is to alleviate the inadequate fish migration conditions in the basin. The migration concerns are being addressed by removing diversion structures, constructing fish passage facilities, implementing minimum instream flow requirements, and providing trap and haul efforts when needed. The objective of the Walla Walla River Fish Passage Operations Project is to increase the survival of migrating adult and juvenile salmonids in the Walla Walla River basin. The project is responsible for coordinating operation and maintenance of ladders, screen sites, bypasses, trap facilities, and transportation equipment. In addition, the project provides technical input on passage criteria and passage and trapping facility design and operation. Operation of the various passage facilities and passage criteria guidelines are outlined in an annual operations plan that the project develops. During the 2004-2005 project year, there were 590 adult summer steelhead, 31 summer steelhead kelts (Oncorhynchus mykiss), 70 adult bull trout (Salvelinus confluentus); 80 adult and 1 jack spring Chinook (O. tshawytscha) enumerated at the Nursery Bridge Dam fishway video counting window between December 13, 2004, and June 16, 2005. Summer steelhead and spring chinook were observed moving upstream while bull trout were observed moving both upstream and downstream of the facility. In addition, the old ladder trap was operated by ODFW in order to enumerate fish passage. Of the total, 143 adult summer steelhead and 15 summer steelhead kelts were enumerated at the west ladder at Nursery Bridge Dam during the video efforts between February 4 and May 23, 2005. Operation of the Little Walla Walla River juvenile trap for trap and haul purposes was not necessary this year.

Bronson, James P. (Confederated Tribes of the Umatilla Indian Reservation, Department of Natural Resources, Pendleton, OR); Duke, Bill B. (Oregon Department of Fish and Wildlife, Pendleton, OR)

2006-02-01

119

Stability estimation of vietnamese small – sized fishing vessels at early stages of their designing  

Directory of Open Access Journals (Sweden)

Full Text Available A new method of stability estimation of Vietnamese small-sized fishing vessels at early stages of designing is presented in the paper. A general mathe-matical model of critical elevations of center gravity (CG) of a vessel for all crite-ria is based on stability recommendations of the international marine organiza-tion (IMO) (1968) and Rules of the Russian marine navigation register (2005) (for small vessels). After the processing of statistical data on Vietnamese small-sized fishing vessels, regression models of critical elevations of CG according to different criteria of stability are developed. It is shown that the derived regression models are of sufficient accuracy. Using these models and factual CG it is possi-ble to formulate a sufficient condition for stability in the equation system of de-sign. The solution of this equation system allows to obtain geometrical character-istics of a vessel, which meet stability requirements.

Mai Quoc Truong

2009-01-01

120

Study of fish oil bleaching using the sodium bentonite through a factorial design  

Directory of Open Access Journals (Sweden)

Full Text Available This work was a experimental design in order to optimize the process of bleaching of fish oil, using the sodium bentonite as adsorbent, from the influence of variables such as weight of sodium bentonite, the temperature process, thermal activation of sodium bentonite and time of agitation. It was then possible to fit a mathematical model with the influence of each variable in the process of bleaching of the oil. The response variable was the absorbance at 444 nm.

Caio Guilherme Secco Souza; Reinaldo Aparecido Bariccatti; Marcia Regina Simões; José Dilson Silva de Oliveira

2011-01-01

 
 
 
 
121

Constructing a DNA ladder Range for Lambda Phage by multiplex PCR  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Objectives: DNA ladder contains DNA fragments of different length but with known size, used to determine the size of unknown DNA molecules. Different DNA ladders are available for expected DNA length. Conserved sequences were selected for design of primers to generate DNA fragments of known specific size."nMaterials and Methods: In this study, we describe a method by which DNA ladder was prepared based on multiplex PCR technique. Different lengths of DNA fragments were amplified using the primers designed according to the 1216-2136 sequence extent of lambda phage DNA. Target DNA fragments were amplified using multiplex PCR and extracted."nResults: The results showed an amplified lambda phage DNA at particular target sites by using 1 forward and 6 different reverse primers (for 100, 200, 400, 600, 800, 1000bp) for the successful amplification."nConclusion: This method would be more cost effective than commercial DNA molecular weight markers.

R Gopalakrishnan; S Joseph; S Sellappa

2010-01-01

122

Doped spin ladders under magnetic field  

International Nuclear Information System (INIS)

This thesis deals with the physics of doped two-leg ladders which are a quasi one-dimensional and unconventional superconductor. We particularly focus on the properties under magnetic field. Models for strongly correlated electrons on ladders are studied using exact diagonalization and density-matrix renormalization group (DMRG). Results are also enlightened by using the bosonization technique. Taking into account a ring exchange it highlights the relation between the pairing of holes and the spin gap. Its influence on the dynamics of the magnetic fluctuations is also tackled. Afterwards, these excitations are probed by the magnetic field by coupling it to the spin degree of freedom of the electrons through Zeeman effect. We show the existence of doping-dependent magnetization plateaus and also the presence of an inhomogeneous superconducting phase (FFLO phase) associated with an exceeding of the Pauli limit. When a flux passes through the ladder, the magnetic field couples to the charge degree of freedom of the electrons via orbital effect. The diamagnetic response of the doped ladder probes the commensurate phases of the t-J model at low J/t. Algebraic transverse current fluctuations are also found once the field is turned on. Lastly, we report numerical evidences of a molecular superfluid phase in the 3/2-spin attractive Hubbard model: at a density low enough, bound states of four fermions, called quartets, acquire dominant superfluid fluctuations. The observed competition between the superfluid and density fluctuations is connected to the physics of doped ladders. (author)

2007-01-01

123

The non-linear sigma model and spin ladders  

CERN Document Server

The well known Haldane map from spin chains into the O(3) non linear sigma model is generalized to the case of spin ladders. This map allows us to explain the different qualitative behaviour between even and odd ladders, exactly in the same way it explains the difference between integer and half-integer spin chains. Namely, for even ladders the topological term in the sigma model action is absent, while for odd ladders the \\theta parameter, which multiplies the topological term, is equal to 2 \\pi S, where S is the spin of the ladder. Hence even ladders should have a dynamically generated spin gap, while odd ladders with half-integer spin should stay gapless, and physically equivalent to a perturbed SU(2)_1 Wess-Zumino -Witten model in the infrared regime. We also derive some consequences from the dependence of the sigma model coupling constant on the ladder Heisenberg couplings constants.

Sierra, G

1995-01-01

124

Determination of basic elements and features of medium fishing trawlers on initial stages of designing  

Directory of Open Access Journals (Sweden)

Full Text Available Over hundred of projects of medium fishing vessels, designed in Russia (including USSR), Europe, Japan and Vietnam have been examined. The analysis of their basic design characteristics is made. The purpose of the investigation is to define general principles of changes in width B, board height H, freight draft T, greater displacement and load-carrying capacity according to effective vessel length L^^. The effective dependences which allow to define the greatest width, board height, freight draft, relative values (L^^/B, ?/?, ?/?), full displacement and load-carrying capacity of a vessel depending on its effective length.

Dyatchenko Sergey Vasilyevich; Lyong Hung Ngoc

2009-01-01

125

The Static Ladder Problem with Two Sources of Friction  

Science.gov (United States)

The problem of a ladder leaning against a wall in static equilibrium is a classic example encountered in introductory mechanics texts. Most discussions of this problem assume that the static frictional force between the ladder and wall can be ignored. A few authors consider the case where the static friction coefficients between ladder/wall…

Bennett, Jonathan; Mauney, Alex

2011-01-01

126

Dzyaloshinski-Moriya Interaction in S = 1/2 Ladder  

International Nuclear Information System (INIS)

Using a Majorana fermion representation, we discuss the influence of Dzyaloshinski-Moriy a interaction on the magnetic properties of a spin-1/2 ladder. We calculate the spin-echo decay rate and analyze the modifications with respect to the isotropic ladder. Implications of our calculations for experiments on ladder systems are discussed. (author)

2003-01-01

127

Structurally perfect ladder polymers: Shape and conversion  

Energy Technology Data Exchange (ETDEWEB)

After a short excursion into the strategy of the synthesis of structurally perfect ladder polymers, models of the spatial shape of two different ladder polymers will be introduced. It will be seen that the molecular structure has considerable influence upon the polymer`s shape which can even go so far as to form two-dimensional coils from relatively short segments. The second half of the presentation describes how one can unfold these polymers with a chemical transformation and even possibly obtain fully aromatic, so-called graphitic ribbons.

Loeffler, M.; Schlueter, A.D. [Freie Universitaet, Berlin (Germany)

1993-12-31

128

Calculating f? in the consistent ladder approximation  

International Nuclear Information System (INIS)

We recalculate the pion decay constant f? and the vacuum expectation value in a new ladder approximation scheme to the Schwinger-Dyson and Bethe-Salpeter equations which is consistent both with the axial Ward-Takahashi identity and Z2=1 condition (or the vector Ward identity in the abelian case). We find that our previous numerical results remain qualitatively unchanged: In particular, the Pagels-Stokar formula is a good approximation to f? which agrees with the ladder-exact value to within 5%-30%. (orig.).

1992-01-01

129

Generalized Binomial States Ladder Operator Approach  

CERN Document Server

We show that the binomial states (BS) of Stoler {\\it et al.} admit the ladder and displacement operator formalism. By generalizing the ladder operator formalism we propose an eigenvalue equation which possesses the number and the squeezed states as its limiting solutions. The explicit forms of the solutions, to be referred to as the {\\it generalized binomial states} (GBS), are given. Corresponding to the wide range of the eigenvalue spectrum these GBS have as widely different properties. Their limits to number and {\\it squeezed} states are investigated in detail. The time evolution of BS is obtained as a special case of the approach.

Fu, H C; Fu, Hong-Chen; Sasaki, Ryu

1996-01-01

130

Calculated Investigation of Gravitational Sagging of ITS Outer Layer Model Ladder for ALICE and Optimization of Parameters of Ladder  

CERN Document Server

The report presents results of stiffness' calculations of the about 1.1 m length lightweight model ladder and some of its modifications for Inner Tracking System Abstract: for ALICE. As a result, dependences of the ladder's stiffness and mass Abstract: Abstract: characteristics on its geometrical parameters are investigated and an optimum structure of the ladder Abstract: (carbon fibre space frame) is determined.

Gloukhov, N P; CERN. Geneva

1996-01-01

131

Scale modelling and hydro biology: the design of fish passes; La modelisation physique en hydrobiologie: conception des ouvrages de franchissement pour poissons migrateurs  

Energy Technology Data Exchange (ETDEWEB)

Scale models are used for designing fish pass. They are necessary to fit the project to real site environment, to verify the attractiveness of the pass and the suitability of flow conditions for fish. They have allowed the application of a new concept: the rip rap fish pass. Nevertheless, its remains difficult to efficiently translate fish behaviours criteria into simple hydraulic conditions. This point requires a real multidisciplinary approach of the design work, associating hydraulic engineers and biologists. (author)

Bouchard, J.P. [Electricite de France (EDF/LNHE), 78 - Chatou (France)

2004-07-01

132

Electrostatic precipatator construction having ladder bar spacers  

Energy Technology Data Exchange (ETDEWEB)

The present invention relates to an improved construction for an electrostatic precipitator having ladder bar spacers. The electrostatic precipitator collects solid particles carried by a flue gas from a source of combustion. The precipitator includes a plurality of spaced plates for collecting solid particles from the flue gas by electrostatic attraction of the solid particles to the plates. A second plurality of elongated electrodes is positioned among the plates. Each of the electrodes is mounted between a pair of adjacent plates. Each of the electrodes is parallel to the other electrodes and is parallel to the plates. A third plurality of ladder bars is positioned between adjacent plates to hold the plates in a flat attitude and to maintain adjacent surfaces of adjacent plates substantially equidistantly spaced from one another. Each of the ladder bars has a connector bar secured to one of the pair of adjacent surfaces. Each of the ladder bars has a fourth plurality of holder bars. Each of the holder bars having one end connected to its respective connector bar and extending outwardly from the connector bar toward the other of the pair of adjacent surfaces. A contact on the other end of each holder bar engages the other of the pair of adjacent surfaces to hold the pair of adjacent surfaces apart.

Jonelis, J.A.

1984-10-30

133

Missouri's Teacher Career Ladder Program. Research Brief  

Science.gov (United States)

Although Missouri has had a career ladder program for teachers since 1987, there has been little research examining the program's effects. This paper examines the program's effect on student achievement using longitudinal data on district math and reading scores for 524 Missouri school districts over a nine-year period. Our primary specification…

Booker, Kevin; Glazerman, Steven

2008-01-01

134

Multiinstanton ladders in baryon number violating processes  

CERN Document Server

We estimate the contribution of a class of multiinstanton ladder graphs to baryon and lepton number violating processes in the standard model. We find that this contribution is negligible and does not alter the high energy behavior of the leading semiclassical approximation.

Lazarides, G

1995-01-01

135

Laddering in Initial Public Offering Allocations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Tying Initial Public Offering (IPO) allocations of common stock to after-listing purchases in the IPO shares, a process referred to as IPO laddering, has resulted in large-scale investigations of the major investment banks by the SEC and the National Association of Securities Dealers (NASD). This pr...

Fjesme, Sturla Lyngnes

136

Twisted Order Parameter applied to Dimerized Ladders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

6 pages.-- Revtex4 file, color figures.-- PACS numbers: 75.10.Jm 75.10.-b 74.20.Mn. , We apply the twisted order parameter (TOP) for dimerized quantum spin ladders to locate the critical phases that separate gapped phases representing quantum spin liquids of various types. Using the DMRG, method we fin...

Almeida, Javier; Martín-Delgado, Miguel Ángel; Sierra, Germán

137

Spin gaps in coupled t-J ladders  

CERN Document Server

Spin gaps in coupled t-J ladders are investigated by exact diagonalization of small clusters up to 4\\times8 sites. At half-filling, the numerical results for the triplet excitation spectrum are in very good agreement with a second order perturbation expansion in term of small inter-ladder and intra-ladder exchange couplings between rungs (J/J^\\prime<0.25). The band of local triplet excitations moving coherently along the ladder (with momenta close to \\pi) is split by the inter-ladder coupling. For intermediate couplings finite size scaling is used to estimate the spin gap. In the isotropic infinite 4-chain system (two coupled ladders) we find a spin gap of 0.245 J, roughly half of the single ladder spin gap. When the system is hole doped, bonding and anti-bonding bound pairs of holes can propagate coherently along the chains and the spin gap remains finite.

Poilblanc, D; Rice, T M

1994-01-01

138

Designing a mathematical model of management techniques (TQM, BPR) in Zahedan , weave fishing net industries  

Directory of Open Access Journals (Sweden)

Full Text Available Currently reengineering and Total Quality Management (TQM) techniques known improvement in organizations. in this research initially a Mathematical model was designed to find out the main factors in relative reengineering and TQM. Based on finding factors of Model, a 40 element questionary formed and the questionnaire distributed among the staff of fishing net factory in a random order, finding by using of SPSS, the data analyzed and concluding Remark shows the installation and acceptance of TQM by using reengineering is possible to the factory.

Dr.Baqer Kord, Dr. Habibollah Salarzehi, Hamed Aramesh, Somayeh Mousavi

2010-01-01

139

Spin-1 ladder: A bosonization study  

International Nuclear Information System (INIS)

We construct a field-theoretic description of two coupled spin-1 Heisenberg chains, starting with the known representation of a single spin-1 chain in terms of Majorana fermions (or Ising models). After reexamining the bosonization rules for two Ising models, taking particular care of order and disorder operators, we obtain a bosonic description of the spin-1 ladder. From renormalization-group and mean-field arguments, we conclude that, for a small interchain coupling, the spin-1 ladder is approximately described by three decoupled, two-frequency sine-Gordon models. We then predict that, starting with decoupled chains, the spin gap decreases linearly with interchain coupling, in both the ferromagnetic and antiferromagnetic directions. Finally, we discuss the possibility of an incommensurate phase in the spin-1 zigzag chain.

2000-05-01

140

Triviality of the ladder approximation to QCD  

International Nuclear Information System (INIS)

The validity of the ladder approximation (LA) in QCD in the context of the corresponding Schwinger-Dyson (SD) and Stavnov-Taylor (ST) equations is investigated. In contrast to QED, in QCD because of color degrees of freedom the summation of the ladder diagrams within the Bethe-Salpeter integral equation for the quark-gluon vertex at zero momentum transfer on the account of the corresponding ST identity does provide an addition constraint on the quark SD equation itself. Moreover, the solution of the constraint equation requires the full quark propagator should be almost trivial (free-type) one, i.e., only trivial quark propagator is allowed in the LA to QCD

1999-10-06

 
 
 
 
141

Ising Model on an Infinite Ladder Lattice  

International Nuclear Information System (INIS)

In this paper we propose an Ising model on an infinite ladder lattice, which is made of two infinite Ising spin chains with interactions. It is essentially a quasi-one-dimensional Ising model because the length of the ladder lattice is infinite, while its width is finite. We investigate the phase transition and dynamic behavior of Ising model on this quasi-one-dimensional system. We use the generalized transfer matrix method to investigate the phase transition of the system. It is found that there is no nonzero temperature phase transition in this system. At the same time, we are interested in Glauber dynamics. Based on that, we obtain the time evolution of the local spin magnetization by exactly solving a set of master equations.

2007-09-15

142

Boundary defect in a spin ladder  

Energy Technology Data Exchange (ETDEWEB)

The integrable su(1{vert_bar}3)-invariant spin-ladder model with boundary defect is studied using the Bethe ansatz method. The exact phase diagram for the ground state is obtained and the boundary quantum critical behavior is discussed. It consists of a gapped phase in which the rungs of the ladder form singlet states and a gapless Luttinger liquid phase. Depending on the boundary potential of the first rung a boundary bound state may occur. If populated at low temperatures this bound state represents a localized magnetic moment of spin one. In the Luttinger liquid phase the local moment is screened at low temperatures in analogy to the Kondo effect. {copyright} 2001 American Institute of Physics.

Wang, Yupeng; Schlottmann, P.

2001-06-01

143

The spin-1 ladder A bosonization study  

CERN Multimedia

We construct a field-theoretic description of two coupled spin-1 Heisenberg chains, starting with the known representation of a single spin-1 chain in terms of Majorana fermions (or Ising models). After reexamining the bosonization rules for two Ising models, taking particular care of order and disorder operators, we obtain a bosonic description of the spin-1 ladder. From renormalization-group and mean-field arguments, we conclude that, for a small interchain coupling, the spin-1 ladder is approximately described by three decoupled, two-frequency sine-Gordon models. We then predict that, starting with decoupled chains, the spin gap decreases linearly with interchain coupling, both in the ferromagnetic and antiferromagnetic directions. Finally, we discuss the possibility of an incommensurate phase in the spin-1 zigzag chain.

Allen, D

2000-01-01

144

Ladders for Wilson Loops Beyond Leading Order  

CERN Document Server

We set up a general scheme to resum ladder diagrams for the quark-anti-quark potential in N=4 super-Yang-Mills theory, and do explicit calculations at the next-to-leading order. The results perfectly agree with string theory in AdS(5)xS(5) when continued to strong coupling, in spite of a potential order-of-limits problem.

Bykov, D

2012-01-01

145

D0 Silicon Upgrade: Ladder Assembly Sequences  

International Nuclear Information System (INIS)

This is an abridged version of the assembly sequence described by the DO assembly subgroup of Cooper, Hrycyk, Kowalski, Rapidis, and Ratzmann. This primarily is used to indicate major steps during the sequence and to list fixturing requirements. Assembly - (1) Place support rails in (1) 3 Chip Ladder Construction fixture. The two rails get held under vacuum. (2) Apply adhesive to the region where contact will be made with the beryllium substrates. (3) Place underside beryllium pieces (active and dummy ends) into the (1) 3 Chip Ladder Construction fixture. These pieces get placed in the fixture against the appropriate pins to mimic final positioning in the bulkhead. Apply vacuum to the beryllium pieces. Allow to cure? (4) Align silicon in (1) 3 Chip Ladder Construction fixture. Reference features on the fixture will be parameterized. Holes in the fixture near the silicon center line will be targeted to set the silicon axis relative to the beryllium slot edge. Z positioning of the detectors will be achieved by shimming between the detectors and butting up the end of the silicon against the fixture. (5) Remove silicon detectors and apply adhesive to the rails and upper surfaces of the beryllium. (6) Replace silicon and check final position of the detectors. (7) Release vacuum on the rails so they cure in a stress-free state. Allow adhesive to cure. (8) Apply adhesive and align HDI to the silicon using (2) 3 Chip HDI Gluing fixture. The HDI will have tabs which are held by the fixture for location relative to the detectors. Allow adhesive to cure. (9) Move ladder to (3) 3 Chip Wirebonding Fixture. Transfer fixture to the wirebonder and bond chip-silicon and silicon-silicon.

1994-01-01

146

Nonlinear dynamics of ladder and lambda STIRAP  

International Nuclear Information System (INIS)

[en] We have studied the exact nonlinear dynamics underlying stimulated Raman adiabatic passage (STIRAP) for a particle in a multi-level anharmonic system (the infinite square-well) driven by two sequential laser pulses, each with constant carrier frequency. We compare two basic processes, ladder and lambda. We have found that the coherent population transfer for both cases is dependent on the nature of the Floquet eigenphase avoided crossings created by an underlying transition to chaos

2005-01-01

147

Hilbert Functions of Ladder Determinantal Varieties  

UK PubMed Central (United Kingdom)

We consider algebraic varieties de#ned bythvanish,fofall minors ofa #xed size ofarectangularmatrixwithindeterminateentriessuch thh thindeterminates inth9K minors arerestricted to lie in a ladder shder region of th rectangular array. Explicit formulae for thHilbert functionofsuchvarieties are obtained in (i) th rectangular casebyAbhKT`Lf(Rend.Sem. Mat. Univers. Politecn. Torino 42 (1984) 65), and(ii)thcase of22 minors in one-sidedladders by Kulkarni (Semigroup ofordinary multiple point, analysisofstraighL8`fEformulaand countingmonomials,Phno ThnomiPurdue University, West Lafayette, USA, 1985). Morerecently,KrattenthKUKandProhL9` (Trans. Amer. Math Soc. 351 (1999)1015)h15proved a`remarkable formula', conjectured by Conca and Herzog (Adv. Math 132 (1997) 120) for thHilbert series in th case ofarbitrary sized minors in one-sided ladders. Wedescribehscanexplicit, albeit complicated, formula for th Hilbert function and th Hilbert series in th case ofarbitrary sized minors in two-sided ladders. From a combinatorialviewpoint,theis equivalentto th enumeration ofcertain sets of`indexed monomials'. c2002 Elsevier Science B.V. Allrigh8 reserved.MSC: Primary 05A15; 13C40; 13D40; 14M12; Secondary 05A19; 05E10; 14M15Keywords: Hilbert functions; Hilbert series; Determinantal varieties; Ladder determinantal ideals;Indexed monomials0.I9363Dg1404Let K be a #eld and X =(X ij )beanm(1)m(2)matrixwhrientries are variablesover K . Given a subset Yofth integral rectangle[1;m(2)] ={(i;j):16 i 6m(1) and 1 6 j 6m(2)};# A partofthP work was supportedbyresearchgrant No. 93-106=RG=MATHS=ASfromthThmf WorldAcademy ofSciences, Italy.Currently,th autheis partially supported by a `Career Award' grant fromAICTE, NewDelh and an IRCC gran...

Sudh R. Ght-p Departmentof

148

D0 Silicon Upgrade: Ladder Assembly Sequences  

Energy Technology Data Exchange (ETDEWEB)

This is an abridged version of the assembly sequence described by the DO assembly subgroup of Cooper, Hrycyk, Kowalski, Rapidis, and Ratzmann. This primarily is used to indicate major steps during the sequence and to list fixturing requirements. Assembly - (1) Place support rails in (1) 3 Chip Ladder Construction fixture. The two rails get held under vacuum. (2) Apply adhesive to the region where contact will be made with the beryllium substrates. (3) Place underside beryllium pieces (active and dummy ends) into the (1) 3 Chip Ladder Construction fixture. These pieces get placed in the fixture against the appropriate pins to mimic final positioning in the bulkhead. Apply vacuum to the beryllium pieces. Allow to cure? (4) Align silicon in (1) 3 Chip Ladder Construction fixture. Reference features on the fixture will be parameterized. Holes in the fixture near the silicon center line will be targeted to set the silicon axis relative to the beryllium slot edge. Z positioning of the detectors will be achieved by shimming between the detectors and butting up the end of the silicon against the fixture. (5) Remove silicon detectors and apply adhesive to the rails and upper surfaces of the beryllium. (6) Replace silicon and check final position of the detectors. (7) Release vacuum on the rails so they cure in a stress-free state. Allow adhesive to cure. (8) Apply adhesive and align HDI to the silicon using (2) 3 Chip HDI Gluing fixture. The HDI will have tabs which are held by the fixture for location relative to the detectors. Allow adhesive to cure. (9) Move ladder to (3) 3 Chip Wirebonding Fixture. Transfer fixture to the wirebonder and bond chip-silicon and silicon-silicon.

Ratzmann, Paul; /Fermilab

1994-08-17

149

Local limit theorems for ladder epochs  

CERN Document Server

Let {S_n, n=0,1,2,...} be a random walk generated by a sequence of i.i.d. random variables X_1, X_2,... and let tau be the first descending ladder epoch. Assuming that the distribution of X_1 belongs to the domain of attraction of an alpha-stable law, we study the asymptotic behavior of P(tau=n).

Vatutin, V; Vatutin, Vladimir; Wachtel, Vitali

2007-01-01

150

Magnetization plateaux in dimerized spin ladder arrays  

CERN Multimedia

We investigate the ground state magnetization plateaux appearing in spin 1/2 two-leg ladders built up from dimerized antiferromagnetic Heisenberg chains and dimerized zig-zag interchain couplings. Using both Abelian bosonization and Lanczos methods we find that the system yields rather unusual plateaux and exhibits massive and massless phases for specific choices or ``tuning'' of exchange interactions. The relevance of this behavior in the study of NH_4CuCl_3 is discussed.

Cabra, D C

1999-01-01

151

Box ladders in non-integer dimension  

CERN Multimedia

We construct a class of triangle-ladder diagrams which can be calculated by making a use of Belokurov-Usyukina loop reduction technique in d = 4 -2e dimensions. The main idea of the approach consists in generalization of this loop reduction technique existing in d = 4 dimensions. The recursive formula relating L-loop result for any triangle ladder of that class and (L-1)-loop result for another triangle ladder of the same class is derived. Since the method proposed in the present paper combines analytic and dimensional regularizations, at the end of the calculation we have to remove the analytic regularization by taking the limit in which the parameters of the analytic regularization are vanishing. In this limit on the left hand side of the recursive relations we obtain in the position space the diagram in which the indices of the rungs are 1 and all the other indices are 1-e. Fourier transforms of this type of diagrams are the momentum space diagrams which have indices of the rungs equal to 1-e and all the o...

Gonzalez, Ivan

2012-01-01

152

Exciton Stark ladder in semiconductor superlattices  

Science.gov (United States)

We present a method for calculating the 1s exciton states of type-I and type-II superlattices in an applied static electric field. Our approach is based upon choosing localized exciton wave functions as the basis in which to expand the exciton eigenstates. We calculate the excitonic optical-absorption spectra of a number of very different type-I GaAs/Ga1-xAlxAs superlattices, as a function of electric field, and find our results for the 65-Å superlattice of Agulló-Rueda, Mendez, and Hong [Phys. Rev. B 40, 1357 (1989)] to be in good agreement with the experimental photocurrent spectra over the full range of field strengths. In addition, we explain many of the low-field effects generally seen, such as the ladder absorption asymmetry, oscillations in the absorption of individual levels, and the nonlinear dependence of the exciton-Stark-ladder energy levels on the field strength. Finally, we discuss the electric-field range for which a modified single-particle picture provides an adequate picture of the qualitative features of the exciton Stark ladder.

Dignam, M. M.; Sipe, J. E.

1991-02-01

153

D0 Silicon Upgrade: Thermal Analysis of the D0 3 CHIP Single Sided Ladder  

International Nuclear Information System (INIS)

The design of the D0 single sided 3 chip ladder is shown in figures 1-3. The SVX II chips are mounted directly opposite the cooling channel so that they are most efficiently cooled. Outboard of the cooling channel on the ladder top side is mounted a flex hybrid of copper/kapton. which is adhered to a beryllium substrate using a two part epoxy. The beryllium substrate. aside from providing a solid mounting structure for the flex circuit. provides a thermal conduction path between the components on the hybrid which dissipate heat and the cooling channel. The thickness of the top and bottom beryllium substrates is selected based on the (expected) channel temperature. the power dissipation of the SVX II chips, the power dissipation of the hybrid passive components, and the maximum acceptable silicon temperature within the ladder. The thermal conductivity of the various materials within the ladder must be known to a fair degree of confidence in order to accurately simulate the ladder steady state cooling performance. The thermal conductivity of a number of ladder epoxy candidates was measured using a device at Lab D at Fermilab. Preliminary measurements at Lab D, using a similar setup. have been performed in order to measure the thermal conductivity of beryllium. silicon, aluminum, and other ladder materials. In order to simulate the cooling performance with confidence. prototype ladders were constructed using aluminum substrates (in place of beryllium), blank silicon, and nonfunctional prototype flex hybrid circuits. SVX II heat loads were simulated using 350 ohm strain gages which were adhered to the flex hybrid using a thin layer of epoxy. Temperatures were measured on the prototype ladders using a hand-held IR temperature probe, which has a laser focusing beam enabling simple optical focal length determination. The IR probe allows a correction to account for the surface emissivity of the material being measured. Preliminary measurements at Lab D indicate that the alloy used to construct the ladder models has a conductivity of 237 W/m-K. The assumed conductivity of the blank silicon is 149 W/m-K. Ladder prototypes with aluminum substrates were constructed using the prototype 3 chip assembly fixture at Lab D. A two dimensional cooling simulation program was written using a simultaneous equation solver. The simulation is written by dividing the 2D model into small dx and dy elements and performing an energy balance on each element based on the thermal resistance between the individual elements and their neighbors. It is otherwise known as the finite difference method. The steady state solution is obtained by solving the array of energy balance equations as a DC circuit Convective boundaries can be added on exposed elements using appropriate equations. Following is a schematic which shows the energy balance terms in each element.

1996-01-01

154

D0 Silicon Upgrade: Thermal Analysis of the D0 3 CHIP Single Sided Ladder  

Energy Technology Data Exchange (ETDEWEB)

The design of the D0 single sided 3 chip ladder is shown in figures 1-3. The SVX II chips are mounted directly opposite the cooling channel so that they are most efficiently cooled. Outboard of the cooling channel on the ladder top side is mounted a flex hybrid of copper/kapton. which is adhered to a beryllium substrate using a two part epoxy. The beryllium substrate. aside from providing a solid mounting structure for the flex circuit. provides a thermal conduction path between the components on the hybrid which dissipate heat and the cooling channel. The thickness of the top and bottom beryllium substrates is selected based on the [expected] channel temperature. the power dissipation of the SVX II chips, the power dissipation of the hybrid passive components, and the maximum acceptable silicon temperature within the ladder. The thermal conductivity of the various materials within the ladder must be known to a fair degree of confidence in order to accurately simulate the ladder steady state cooling performance. The thermal conductivity of a number of ladder epoxy candidates was measured using a device at Lab D at Fermilab. Preliminary measurements at Lab D, using a similar setup. have been performed in order to measure the thermal conductivity of beryllium. silicon, aluminum, and other ladder materials. In order to simulate the cooling performance with confidence. prototype ladders were constructed using aluminum substrates (in place of beryllium), blank silicon, and nonfunctional prototype flex hybrid circuits. SVX II heat loads were simulated using 350 ohm strain gages which were adhered to the flex hybrid using a thin layer of epoxy. Temperatures were measured on the prototype ladders using a hand-held IR temperature probe, which has a laser focusing beam enabling simple optical focal length determination. The IR probe allows a correction to account for the surface emissivity of the material being measured. Preliminary measurements at Lab D indicate that the alloy used to construct the ladder models has a conductivity of 237 W/m-K. The assumed conductivity of the blank silicon is 149 W/m-K. Ladder prototypes with aluminum substrates were constructed using the prototype 3 chip assembly fixture at Lab D. A two dimensional cooling simulation program was written using a simultaneous equation solver. The simulation is written by dividing the 2D model into small dx and dy elements and performing an energy balance on each element based on the thermal resistance between the individual elements and their neighbors. It is otherwise known as the finite difference method. The steady state solution is obtained by solving the array of energy balance equations as a DC circuit Convective boundaries can be added on exposed elements using appropriate equations. Following is a schematic which shows the energy balance terms in each element.

Ratzmann, Paul M.; /Fermilab

1996-06-18

155

A mean field theory for the spin ladder system  

CERN Multimedia

In the present paper, we propose a mean field approach for spin ladders based upon the Jordan-Wigner transformation along an elaborately ordered path. We show on the mean field level that ladders with even number legs open a energy gap in their low energy excitation with a magnitude close to the corresponding experimental values, whereas the low energy excitation of the odd-number-leg ladders are gapless. It supports the validity of our approach. We then calculate the gap size and the excitation spectra of 2-leg-ladder system. Our result is in good agreement with both the experimental data and the numerical results.

Dai, X; Dai, Xi; Su, Zhao-bin

1998-01-01

156

Li Induced Spin and Charge Excitations in a Spin Ladder  

CERN Multimedia

A lithium dopant in a cuprate spin ladder acts as a vacant (non-magnetic) site accompanied by an extra hole bound by a Coulomb potential. We find that, although the undoped ladder spin gap is not essentially altered by Li doping, a dopant-magnon bound state appears within the gap. Contrary to the case of Zn-doped ladders, we predict that, in the Li-doped ladder, the spin liquid character is very robust against antiferromagnetism. We also predict the spatial dependence of the density of states in the vicinity of the dopant which could be measured by local spectroscopic probes.

Laeuchli, A; White, S R; Laeuchli, Andreas; Poilblanc, Didier

2001-01-01

157

D0 Silicon Upgrade: Ladder Removal Stress Analysis  

Energy Technology Data Exchange (ETDEWEB)

Two different methods will be used to affix ladders to the active bulkhead. Layer 1 and layer 3 ladders will be attached to the active bulkhead using pins. To provide a highly conductive thermal path between these ladders and the cooling channel in the active bulkhead, a small amount of thermally conductive grease will be applied to the bulkhead just prior to ladder installation. Layer 2 and layer 4 ladders will be attached using the same method with the exception that thermally conductive epoxy will be used in lieu of grease. The epoxy is necessary in the outer two layers to maintain barrel rigidity. One major point of concern is the removal of the epoxied ladders. If removal of one of these ladders becomes necessary, it is unclear if the epoxy bond can be broken without damaging the silicon. This report is an attempt to estimate the amount of force necessary to remove a ladder, and the resulting stress that force produces in the silicon. The force necessary to remove an epoxied ladder from a bulkhead is calculated. The resulting silicon stress is also calculated.

Pawlak, John; /Fermilab

1994-10-24

158

Effects of uniaxial pressure in cuprate ladder compound  

International Nuclear Information System (INIS)

Strain and resistivity measurements were performed under uniaxial pressure on single crystals of Sr2.5Ca11.5Cu24O41 (superconductive under isotropic pressure over 2GPa) to clarify the role of pressure in the ladder superconductivity. Compressibility along the uniaxial pressure is the largest in the layer-stacking direction. By increasing the compression of the layer-spacing, the ladder planes are expanded and the resistive component both along and across the ladders are found to decrease monotonically. This indicates that a charge transfer from the CuO2-chain planes to the Cu2O3-ladder planes is promoted by the layer compression.

2005-04-30

159

A Dream or Jacob's Ladder  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Geddes spent the majority of her childhood in Belfast where she was later educated as an illustrator and graphic designer at the Belfast School of Art. In 1910 she began attending William Orpen's classes at the Dublin Metropolitan School and exhibiting at the Arts and Crafts Society. She also exhibi...

Geddes, Wilhelmina Margaret (Irish glass painter, illustrator, decorative artist, 1887-1955)

160

Ladder-type SAW filters using thinned density of randomly distributed "hot" electrodes.  

Science.gov (United States)

A new method for the design of relatively narrowband ladder-type SAW filters is proposed. It consists of the thinning procedure and consecutive randomization of positions of the remaining transductive periods inside the IDT to suppress undesirable additional passbands. A 0.9% fractional bandwidth filter on LiTaO(3) 42°-cut was designed and manufactured using the proposed approach. PMID:21041145

Kim, Che-Uk; Balashov, Sergey M; Plessky, Victor P; Nam, Chang-Woo; Lee, Kyu-Chul

2010-11-01

 
 
 
 
161

Using ergonomics digital human modeling in evaluation of workplaces design and prevention of occupational hazards onboard fishing vessel  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper seeks to present methods for improving the occupational health and safety of Spanish fishermen, and for redesigning the workplace onboard small fishing vessels. To achieve its objective, the research project was designed in four steps: First, the equipment and procedures for catching, han...

Zhang, Bing; Álvarez Casado, Enrique; Tello Sandoval, Sonia; Rodríguez Mondelo, Pedro Manuel

162

Effects of the Missouri Career Ladder Program on Teacher Mobility  

Science.gov (United States)

One goal of Missouri's Career Ladder program (CL) is to help school districts that have difficulty retaining teachers, particularly those that are small and rural, by offering their teachers opportunities to earn extra pay for extra work and professional development. This report seeks to estimate the effect Career Ladder Program has had on…

Booker, Kevin; Glazerman, Steven

2009-01-01

163

Ladder operators for subtle hidden shape-invariant potentials  

International Nuclear Information System (INIS)

Ladder operators can be constructed for all potentials that present the integrability condition known as shape invariance, satisfied by most of the exactly solvable potentials. Using the superalgebra of supersymmetric quantum mechanics, we construct the ladder operators for two exactly solvable potentials that present a subtle hidden shape invariance.

2004-10-29

164

Exactly soluble isotropic spin-1/2 ladder models  

Energy Technology Data Exchange (ETDEWEB)

The undeformed limit of the dilute two-colour braid-monoid algebra gives a natural basis for the description of spin-1/2 ladder models, and allows different Baxterization ansaetze. Based on this observation we find the complete classification of exactly soluble generalized isotropic spin-1/2 ladder models.

Gritsev, V; Baeriswyl, D [Departement de Physique, Universite de Fribourg, Perolles, CH-1700 Fribourg (Switzerland)

2003-12-12

165

Optical properties of ladder type single crystals  

Energy Technology Data Exchange (ETDEWEB)

The optical properties of (M{sub 2}Cu{sub 2}O{sub 3}){sub m}(CuO{sub 2}){sub n} (M = Ca, Sr, Y, Bi) crystals containing the ladder-type plane Cu{sub 2}O{sub 3} were investigated by spectroscopic ellipsometry method in the range 0.5--5.0 eV. The experimental data were analyzed in order to reveal the difference in the microstructure between superconducting (SC) and non-superconducting (NSC) single crystals. The contributions to the optical response due to the electronic excitations of free and bound carriers were analyzed.

Babonas, G.J.; Leonyuk, L.; Reza, A.; Dapkus, L.; Szymczak, R.

1999-12-01

166

Phase diagram of an asymmetric spin ladder  

CERN Multimedia

We investigate an asymmetric zig-zag spin ladder with different exchange integrals on both legs using bosonization and renormalization group. When the leg exchange integrals and frustration both are sufficiently small, renormalization group analysis shows that the Heisenberg critical point flows to an intermediate-coupling fixed point with gapless excitations and a vanishing spin velocity. When they are large, a spin gap opens and a dimer liquid is realized. Here, we find a continuous manifold of Hamiltonians with dimer product ground states, interpolating between the Majumdar-Ghosh and sawtooth spin-chain model.

Chen, S; Voit, J; Chen, Shu

2001-01-01

167

Evaluation of swimming capability and potential velocity barrier problems for fish. Part A: Swimming performance of selected warm and cold water fish species relative to fish passage and fishway design  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study was to provide information about the swimming capability of several widely distributed, economically or recreationally important fish species, for use in mitigating potential velocity barrier problems associated with hydroelectric power facilities. Swimming capability of anadromous and landlocked Atlantic salmon, brook trout, brown trout, lake sturgeon, and walleye, collected from various locations throughout Canada, were investigated to develop criteria for sustained, prolonged, burst swimming performance characteristics of the study species, fish physiology, life history and migration distance on swimming performance. Swimming performance characteristics in the wild, especially the use of physiological telemetry, as well as development of new methodology for the measurement of burst speed was also central to the study. Models were derived to describe swimming capabilities for each study species/life stage in relation to fish length, water velocity, water temperature, and other significant environmental factors. The data will form the basis of guideline development and decision making to improve design and evaluation of fish passage facilities. A series of annotated bibliographies resulting from the study are described in Appendix B. 74 refs., 8 tabs., figs., 2 appendices.

Scruton, D. A.; Goosney, R. G. [Fisheries and Oceans Canada, Science Branch, St. John`s, NF (Canada); McKinley, R. S.; Booth, R. K.; Peake, S. [Waterloo Univ., Biotelemetry Institute, Waterloo, ON (Canada)

1998-08-01

168

Evaluation of swimming capability and potential velocity barrier problems for fish. Part A: Swimming performance of selected warm and cold water fish species relative to fish passage and fishway design  

International Nuclear Information System (INIS)

[en] The objective of this study was to provide information about the swimming capability of several widely distributed, economically or recreationally important fish species, for use in mitigating potential velocity barrier problems associated with hydroelectric power facilities. Swimming capability of anadromous and landlocked Atlantic salmon, brook trout, brown trout, lake sturgeon, and walleye, collected from various locations throughout Canada, were investigated to develop criteria for sustained, prolonged, burst swimming performance characteristics of the study species, fish physiology, life history and migration distance on swimming performance. Swimming performance characteristics in the wild, especially the use of physiological telemetry, as well as development of new methodology for the measurement of burst speed was also central to the study. Models were derived to describe swimming capabilities for each study species/life stage in relation to fish length, water velocity, water temperature, and other significant environmental factors. The data will form the basis of guideline development and decision making to improve design and evaluation of fish passage facilities. A series of annotated bibliographies resulting from the study are described in Appendix B. 74 refs., 8 tabs., figs., 2 appendices

1998-01-01

169

Design and Analysis of an Underwater White LED Fish-Attracting Lamp and Its Light Propagation  

Directory of Open Access Journals (Sweden)

Full Text Available Light emitting diodes (LED) are a new source for replacing traditional light sources including under water illumination. As traditional underwater light sources operate under a radiative transfer model, the luminous intensity is dispersed evenly at each emission angle, with the scattering factors included in the attenuation coefficient. By contrast, LED light sources are characterized by being highly directional, causing underwater luminous energy to vary with different emission angles. Thus, the traditional theory of underwater optical transfer becomes inapplicable when an underwater LED lighting module is designed. Therefore, to construct an underwater transfer model for LED light sources, this study employed the average cosine of the underwater light field, the method for light scattering probability, the LED luminous intensity distribution curve (LIDC) and axial luminous intensity. Afterwards, an underwater LED fish?attracting lamp was designed. Experimental results showed that, compared with the simulation values, the luminous intensity of the underwater LED lighting module at all emission angles had a percentage error of less than 10%.

Sheng Chih Shen; Cheng Yuan Kuo; Ming-Chung Fang

2013-01-01

170

Staff nurses revitalize a clinical ladder program through shared governance.  

UK PubMed Central (United Kingdom)

After 20 years of a static clinical ladder program at our institution, the clinical ladder program was completely redesigned using a staff nurse-led shared governance structure to re-envision the program as an innovative, staff leadership model to meet our organizational nursing mission and vision strategic plans around retention and professional development. The literature demonstrated a lack of outcome-driven findings on the sustainability of hospital-based clinical ladder programs. The authors cover the rationale for our clinical ladder model, the process used for revision, the implementation strategies, and the specific outcomes tracked regarding nurse satisfaction, affiliation, retention, and participation of staff nurses advancing to the optional upper levels of the ladder.

Winslow SA; Fickley S; Knight D; Richards K; Rosson J; Rumbley N

2011-01-01

171

Fixed-location hydroacoustic monitoring designs for estimating fish passage using stratified random and systematic sampling  

International Nuclear Information System (INIS)

Five alternate sampling designs are compared using 15 d of 24-h continuous hydroacoustic data to identify the most favorable approach to fixed-location hydroacoustic monitoring of salmonid outmigrants. Four alternative aproaches to systematic sampling are compared among themselves and with stratified random sampling (STRS). Stratifying systematic sampling (STSYS) on a daily basis is found to reduce sampling error in multiday monitoring studies. Although sampling precision was predictable with varying levels of effort in STRS, neither magnitude nor direction of change in precision was predictable when effort was varied in systematic sampling (SYS). Furthermore, modifying systematic sampling to include replicated (e.g., nested) sampling (RSYS) is further shown to provide unbiased point and variance estimates as does STRS. Numerous short sampling intervals (e.g., 12 samples of 1-min duration per hour) must be monitored hourly using RSYS to provide efficient, unbiased point and interval estimates. For equal levels of effort, STRS outperformed all variations of SYS examined. Parametric approaches to confidence interval estimates are found to be superior to nonparametric interval estimates (i.e., bootstrap and jackknife) in estimating total fish passage. 10 refs., 1 fig., 8 tabs

1993-01-01

172

Novel Ladder Polymers for Use as High Temperature Stable Resins or Coatings.  

Science.gov (United States)

An object of the invention is to synthesize a new class of ladder and partial ladder polymers. In accordance with the invention, the new class of ladder and partial ladder polymers are synthesized by polymerizing a bis-dienophile with a bis-diene. Another...

M. A. Meador

1988-01-01

173

Installaton of a fish migration channel for spawning at Itaipu  

International Nuclear Information System (INIS)

[en] The objective of installing a fish migration channel for spawning at the Itaipu hydroelectric station on the Parana river between Brazil and Paraguay is to improve fish recovery downstream from the dam. Preliminary data from the first phase has proved the efficiency of an experimental project, with the entry and ascendancy of fish in a migration channel ladder. These data now provide the technical basis for implementation of the complementary spawning channel stage. (author)

1993-01-01

174

Analysis of environmental issues related to small scale hydroelectric development. II. Design considerations for passing fish upstream around dams. Environmental Sciences Division Publication No. 1567  

Energy Technology Data Exchange (ETDEWEB)

The possible requirement of facilities to move migrating fish upstream around dams may be a factor in determining the feasibility of retrofitting small dams for hydroelectric generation. Basic design considerations are reported that should be evaluated on a site-specific basis if upstream fish passage facilities are being considered for a small scale hydroelectric project (defined as an existing dam that can be retrofitted to generate 25 MW or less). Information on general life history and geographic distribution of fish species that may require passage is presented. Biological factors important in the design of upstream passage facilities are discussed: gas bubble disease, fish swimming speed, oxygen consumption by fish, and diel and photo behavior. Three general types of facilities (fishways, fish locks, and fish lifts) appropriate for upstream fish passage at small scale hydroelectric projects are described, and size dimensions are presented. General design criteria for these facilities (including fish swimming ability and behavior) and general location of facilities at a site are discussed. Basic cost considerations for each type of passage facility, including unit cost, operation and maintenance costs, and costs for supplying attraction water, are indicated.

Hildebrand, S.G. (ed.)

1980-08-01

175

A tunable split-ladder photonic crystal cavity by nanoelectromechanical actuator  

Science.gov (United States)

In this paper, we demonstrate a novel split-ladder photonic crystal cavity, which can be tuned across a very large wavelength range by an on-chip integrated nano-electromechanical actuator. The nano-electromechanical actuator is used to control the cavity's central gap. When the cavity gap is widened, the resonance wavelength is blue-shifted correspondingly. The dimensions of the proposed split-ladder cavity are designed by 3D Finite-difference time-domain (FDTD) calculations. We fabricated and tested the devices. Experimental results show that the optomechanical coupling coefficient of the second order resonance mode is about 80 GHz/nm. In addition, there is a relatively linear relationship between the resonance shift and the gap change. The maximum measured resonance wavelength shift is about 17 nm, corresponding to a cavity central gap increase of 26 nm.

Tian, Feng; Zhou, Guangya; Chau, Fook Siong; Deng, Jie; Akkipeddi, Ramam; Tang, Xiaosong; Teo, Siew Lang; Loke, Yee Cheong

2013-03-01

176

The cyclic cystine ladder in ?-defensins is important for structure and stability, but not antibacterial activity.  

UK PubMed Central (United Kingdom)

?-Defensins are ribosomally synthesized cyclic peptides found in the leukocytes of some primate species and have promising applications as antimicrobial agents and scaffolds for peptide drugs. The cyclic cystine ladder motif, comprising a cyclic peptide backbone and three parallel disulfide bonds, is characteristic of ?-defensins. In this study, we explore the role of the cyclic peptide backbone and cystine ladder in the structure, stability, and activity of ?-defensins. ?-Defensin analogues with different numbers and combinations of disulfide bonds were synthesized and characterized in terms of their NMR solution structures, serum and thermal stabilities, and their antibacterial and membrane-binding activities. Whereas the structures and stabilities of the peptides were primarily dependent on the number and position of the disulfide bonds, their antibacterial and membrane-binding properties were dependent on the cyclic backbone. The results provide insights into the mechanism of action of ?-defensins and illustrate the potential of ?-defensin analogues as scaffolds for peptide drug design.

Conibear AC; Rosengren KJ; Daly NL; Henriques ST; Craik DJ

2013-04-01

177

Thévenin equivalents for inhomogeneous ladder networks of generators  

Science.gov (United States)

We find general formulas for Thévenin equivalents (equivalent voltage and equivalent impedance) for inhomogeneous ladder networks of generators defined as a voltage source and an impedance in series. In the projective matrix representation, this is accomplished by adopting a special decomposition of a 3 × 3 transfer matrix which transforms a product of transfer matrices to a product of diagonal matrices up to a prefactor and a postfactor. In particular, we calculate Thévenin equivalents in a closed form for two ladder networks of generators with a periodic transfer matrix of period 1 (tapered ladder network) and period 2.

Hong, Seok-In; Choi, Je-Young

2013-05-01

178

Superconductivity in doped two-leg ladder cuprates  

CERN Document Server

Within the t-J ladder model, superconductivity with a modified d-wave symmetry in doped two-leg ladder cuprates is investigated based on the kinetic energy driven superconducting mechanism. It is shown that the spin-liquid ground-state at the half-filling evolves into the superconducting ground-state upon doping. In analogy to the doping dependence of the superconducting transition temperature in the planar cuprate superconductors, the superconducting transition temperature in doped two-leg ladder cuprates increases with increasing doping in the underdoped regime, and reaches a maximum in the optimal doping, then decreases in the overdoped regime.

Qin, J; Feng, S; Qin, Jihong; Yuan, Feng; Feng, Shiping

2006-01-01

179

Optical conductivity of a t-J ladder  

CERN Document Server

The optical conductivity \\sigma(\\omega ) of a doped two-leg t--J ladder is calculated for an electric field polarized parallel to the legs of the ladder. The conductivity has a Drude weight proportional to the hole doping and an apparent threshold for absorption (a pseudo gap) which may be associated with the energy to break a pair. This pseudogap in \\sigma (\\omega ) is present even though the pairs have a modified d_{x^2-y^2}-like wave function because the geometry of the ladder leads to quasi-particle states which probe the gap along an antinode.

Hayward, C A; Scalapino, D J

1995-01-01

180

Quantum phase transitions in trimerized zig-zag spin ladders  

CERN Multimedia

We analyze the effects of a trimerized modulation in a quantum spin $S=\\frac12$ zig-zag ladder at the magnetization plateau $M=1/3$. Such periodicity is argued to be stemmed from lattice deformations by phonons. The interplay between frustration and exchange modulation is well described by an effective triple sine-Gordon field theory close to the homogeneous ladder and by block-spin perturbation theory in the weakly coupled trimers regime. The characteristic triple degeneracy of the ground state for homogeneous ladders gives place to modulation driven quantum phase transitions, leading to a rich phase diagram including up-up-down, quantum plateau and gapless plateau states.

Rosales, H D; Grynberg, M D; Rossini, G L; Vekua, T

2006-01-01

 
 
 
 
181

From theory to practice ... a career ladder that works.  

UK PubMed Central (United Kingdom)

Frustrated with an increasing turnover rate and role ambiguity, nursing leaders at The University Hospitals sought to implement a program to enhance recruitment and retention efforts. Nursing administration members thought that a career ladder would foster continued development of the novice as well as the expert practitioner. The collaborative efforts of representatives from The University Hospitals, which is made up of Oklahoma Memorial Hospital, Children's Hospital of Oklahoma, and O'Donoghue Rehabilitation Institute, resulted in an eight-tier, four-track career ladder. After 2 years, The University Hospitals Career Ladder continues to be an effective tool for recruiting and retaining nurses.

Monarch K

1994-07-01

182

Ising phases of Heisenberg ladders in a magnetic field  

CERN Multimedia

We examine the influence of weak anisotropic interactions on the T=0 phase diagram of the frustrated two-leg Heisenberg ladder, a well-studied spin model exhibiting integer and fractional magnetization plateaux separated by gapless incommensurate states. We find that the Dzyaloshinskii--Moriya coupling may substantially modify the phase diagram so that the half-integer plateau and the surrounding gapless phases merge into a single Ising-ordered phase breaking the translational symmetry of the lattice. A different Ising order is found for a weakly frustrated ladder. Implications for experimental ladder and dimer systems are discussed.

Penc, K; Miyahara, S; Tchernyshyov, O; Mila, F; Penc, Karlo; Fouet, Jean-Baptiste; Miyahara, Shin; Tchernyshyov, Oleg; Mila, Frederic

2007-01-01

183

Walla Walla River Fish Passage Operations Project : Annual Progress Report October 2007 - September 2008.  

Energy Technology Data Exchange (ETDEWEB)

In the late 1990s, the Confederated Tribes of the Umatilla Indian Reservation, Oregon Department of Fish and Wildlife, and Washington Department of Fish and Wildlife, along with many other agencies, began implementing fisheries restoration activities in the Walla Walla Basin. An integral part of these efforts is to alleviate the inadequate fish migration conditions in the basin. Migration concerns are being addressed by removing diversion structures, constructing fish passage facilities, implementing minimum instream flow requirements, and providing trap and haul efforts when needed. The objective of the Walla Walla River Fish Passage Operations Project is to increase the survival of migrating adult and juvenile salmonids in the Walla Walla River basin. The project is responsible for coordinating operation and maintenance of ladders, screen sites, bypasses, trap facilities, and transportation equipment. In addition, the project provides technical input on passage and trapping facility design, operation, and criteria. Operation of the various passage facilities and passage criteria guidelines are outlined in an annual operations plan that the project develops. Beginning in March of 2007, two work elements from the Walla Walla Fish Passage Operations Project were transferred to other projects. The work element Enumeration of Adult Migration at Nursery Bridge Dam is now conducted under the Walla Walla Basin Natural Production Monitoring and Evaluation Project and the work element Provide Transportation Assistance is conducted under the Umatilla Satellite Facilities Operation and Maintenance Project. Details of these activities can be found in those project's respective annual reports.

Bronson, James P.; Duke, Bill; Loffink, Ken

2008-12-30

184

[Identification of fish species based on ribosomal DNA ITS2 locus].  

Science.gov (United States)

To prevent illegal fishing and sale, the most difficult problem is identification of marketed fish species, especially the parts that are difficult to be differentiated with morphological method (e.g., larval, eggs, scales, meat, products etc. To assist conservation and management of fishery resources, this paper reported a molecular genetic approach based on ribosomal internal transcribed spacer 2 locus. The method includes two steps: (1) the order general primers were designed according to the conservative nature of 5.8SrRAN and 28SrRNA genes within an order, and the DNA ribosomal internal transcribed spacer 2 locus fragment were then amplified and sequenced. (2) The species-specific ladders and the species-specific primers for each species were designed according to the sequencing results. The map of molecular taxonomy was constructed. This approach employs multiplex PCR that is formatted for fish species identification. We tested 210 single-species samples and 40 mix-species samples from different regions of China. The approach distinguished accurately and sensitively samples from each of the five species. This genetic and molecular approach will be useful for fish conservation, assessment, management and exploitation, strengthen in law enforcement of fishery manager, combat rare and endangered fish smuggling, and prevent commercial fraud and biological invasion by harmful nonnative species. PMID:20423891

Yuan, Wan-An

2010-04-01

185

[Identification of fish species based on ribosomal DNA ITS2 locus].  

UK PubMed Central (United Kingdom)

To prevent illegal fishing and sale, the most difficult problem is identification of marketed fish species, especially the parts that are difficult to be differentiated with morphological method (e.g., larval, eggs, scales, meat, products etc. To assist conservation and management of fishery resources, this paper reported a molecular genetic approach based on ribosomal internal transcribed spacer 2 locus. The method includes two steps: (1) the order general primers were designed according to the conservative nature of 5.8SrRAN and 28SrRNA genes within an order, and the DNA ribosomal internal transcribed spacer 2 locus fragment were then amplified and sequenced. (2) The species-specific ladders and the species-specific primers for each species were designed according to the sequencing results. The map of molecular taxonomy was constructed. This approach employs multiplex PCR that is formatted for fish species identification. We tested 210 single-species samples and 40 mix-species samples from different regions of China. The approach distinguished accurately and sensitively samples from each of the five species. This genetic and molecular approach will be useful for fish conservation, assessment, management and exploitation, strengthen in law enforcement of fishery manager, combat rare and endangered fish smuggling, and prevent commercial fraud and biological invasion by harmful nonnative species.

Yuan WA

2010-04-01

186

E3: Education, Experience, Employment The Economic Ladder to Success  

Energy Technology Data Exchange (ETDEWEB)

Science, Technology, Engineering, and Math (STEM) literate citizenry is critical for Idaho's economy to effectively compete and grow in today's global marketplace and enhance Idaho workforce capabilities. Idaho's blueprint presents a collaboration design developed by a group of Idaho stakeholders including state level (STEM) educators, state and federal government, other agencies, and industry across the state. The purpose the Idaho Learn and Earn Blueprint Design is to describe a comprehensive plan for improving STEM education in Idaho through a collaborative partnerships and a series of grant supported projects underpinning this strategic design process building pathways to overcome hurdles in today's economy, and moving communities and families up their economic ladder. The Idaho Learn and Earn Blueprint Design focuses on three industry sectors; energy, advanced manufacturing, and health care. All are important in Idaho and have room for job growth potential among both displaced workers and graduates. Representatives from each sector are members of the design team and assist in developing grants and implementing the actions outlined in the design as the program goes forward. Idaho's current programs are generally institution specific. Each of the state's two-year colleges, along with regional groups and employers, are already working towards improving STEM education across the state. A key aspect of this design is to bring these groups together to focus on four unique goals: (1) Providing industry driven curriculum directly tied to skill based career needs; (2) Enhancing collaboration among stakeholders; (3) Providing access to learn and earn programs; and (4) Improving public and student awareness and interest in targeted industry sector career and educational opportunities.

Anne L Seifert

2011-10-01

187

Hall constant of strongly correlated electrons on a ladder  

CERN Multimedia

The Hall constant R_H in a tight-binding model of correlated electrons on a ladder at T=0 is expressed in terms of derivatives of the ground state energy with respect to external magnetic and electric fields. This novel method is used for the analysis of the t-J model on finite size ladders. It is found that for a single hole R_H is hole-like and close to the semiclassical value, while for two holes it can vary with ladder geometry. In odd-leg ladders, R_H behaves quite regularly changing sign as a function of doping, the variation being quantitatively close to experimental results in cuprates.

Prelovsek, P; Markez, T; Zotos, X

1999-01-01

188

Critical fields and devil's staircase in superconducting ladders  

CERN Multimedia

We have determined the ground state for both a ladder array of Josephson junctions and a ladder of thin superconducting wires. We find that the repulsive interaction between vortices falls off exponentially with separation. The fact that the interaction is short-range leads to novel phenomena. The ground state vortex density exhibits a complete devil's staircase as the applied magnetic field is increased, each step producing a pair of metal-insulator transitions. The critical fields in the staircase are all calculated analytically and depend only on the connectivity of the ladder and the area of the elementary plaquette. In particular the normal square ladder contains no vortices at all until the flux per plaquette reaches 0.5/sqrt{3} flux quanta.

Giles, R T; Giles, Richard T; Kusmartsev, Feodor V

1999-01-01

189

A note on failure of the ladder approximation to QCD  

International Nuclear Information System (INIS)

In this Letter we show that the claim made in [V. Gogohia, Phys. Lett. B 611 (2005) 129] that the ladder approximation to QCD is internally inconsistent is incorrect. The incorrect conclusion in [V. Gogohia, Phys. Lett. B 611 (2005) 129] is based on the incorrect use of a QED-type Ward-Takahashi relation, which does not hold in the ladder approximation to QCD. We give a proof for this fact.

2006-09-14

190

Cancellation of ladder graphs in an effective expansion  

Energy Technology Data Exchange (ETDEWEB)

A resummation of ladder graphs is important in cases where infrared, collinear, or light-cone singularities render the loop expansion invalid, especially at high temperature where these effects are often enhanced. It has been noted in some recent examples of this resummation that the ladder graphs are canceled by other types of terms. In this paper we show that this cancellation is quite general, and for the most part algebraic. {copyright} {ital 1998} {ital The American Physical Society}

Carrington, M.E. [Department of Physics, University of Winnipeg, Winnipeg, Manitoba, R3B2E9 (CANADA); Kobes, R. [Department of Physics, University of Winnipeg, Winnipeg, Manitoba, R3B2E9 (CANADA); Petitgirard, E. [Department of Physics, University of Winnipeg, Winnipeg, Manitoba, R3B2E9 (CANADA)]|[Department of Physics, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

1998-02-01

191

dx2-y2 Pairing correlations in the Hubbard ladder  

International Nuclear Information System (INIS)

We study the strength and the temperature scale of the dx2-y2 pairing correlations in the two-leg Hubbard ladder using quantum Monte Carlo (QMC) simulations. In particular, we present QMC results on the solution of the Bethe-Salpeter equation for the dx2-y2-wave BCS channel. These data show that, at sufficiently low temperatures, there are strong dx2-y2 pairing correlations in the Hubbard ladder.

2007-09-01

192

Cancellation of ladder graphs in an effective expansion  

International Nuclear Information System (INIS)

A resummation of ladder graphs is important in cases where infrared, collinear, or light-cone singularities render the loop expansion invalid, especially at high temperature where these effects are often enhanced. It has been noted in some recent examples of this resummation that the ladder graphs are canceled by other types of terms. In this paper we show that this cancellation is quite general, and for the most part algebraic. copyright 1998 The American Physical Society.

1998-01-01

193

The chiral Ward-Takahashi identity in the ladder approximation  

Energy Technology Data Exchange (ETDEWEB)

We show that the ladder approximation to the Schwinger-Dyson and Bethe-Salpeter equations preserves the Ward-Takahashi identity for the axial vector vertex if and only if we use the gluon momentum as the argument of the running coupling constant. However, in the usual Landau gauge this is inconsistent with the vector Ward identity. We propose a new method for making the ladder approximation scheme consistent with both vector and axial vector Ward identities. (orig.).

Kugo, Taichiro; Mitchard, M.G. (Dept. of Physics, Kyoto Univ. (Japan))

1992-05-21

194

Piezoelectric biosensor with a ladder polymer substrate coating  

Energy Technology Data Exchange (ETDEWEB)

A piezoelectric biosensor substrate useful for immobilizing biomolecules in an oriented manner on the surface of a piezoelectric sensor has a ladder polymer of polyacrylonitrile. To make the substrate, a solution of an organic polymer, preferably polyacrylonitrile, is applied to the surface of a piezoelectric sensor. The organic polymer is modifying by heating the polymer in a controlled fashion in air such that a ladder polymer is produced which, in turn, forms the attachment point for the biomolecules comprising the piezoelectric biosensor.

Renschler, Clifford L. (Tijeras, NM); White, Christine A. (Albuquerque, NM); Carter, Robert M. (New Orleans, LA)

1998-01-01

195

The chiral Ward-Takahashi identity in the ladder approximation  

International Nuclear Information System (INIS)

We show that the ladder approximation to the Schwinger-Dyson and Bethe-Salpeter equations preserves the Ward-Takahashi identity for the axial vector vertex if and only if we use the gluon momentum as the argument of the running coupling constant. However, in the usual Landau gauge this is inconsistent with the vector Ward identity. We propose a new method for making the ladder approximation scheme consistent with both vector and axial vector Ward identities. (orig.)

1992-05-21

196

NEW DESIGN FOR AIRLIFT PUMP USED IN FISH CULTURE TANKS WITH THE ENDANGERED RIO GRANDE SILVERY MINNOW (Hybognathus amarus)  

Directory of Open Access Journals (Sweden)

Full Text Available This article describes an airlift pump used to produce a circular flow in a fish culture tank that does not attach to the tank. The design produces an airlift pump that does not swing back and forth or float upwards while in use. It is easy to build, inexpensive, and can be quickly installed and removed so that it does not interfere with sampling or harvest. The airlift pump was evaluated during a 30-d survival trial with the endangered Rio Grande silvery minnow (Hybognathus amarus) in 2.44-m-diameter circular tanks (3,666 l). Because the fish is endangered, all new culture units must be evaluated in a survival trial. To be able to use a new 15-tank system, survival had to be evaluated in a random representation of three tanks. U.S. Fish and Wildlife Service, which regulates all activities with this endangered species, decided that permitted take (maximum permitted mortality) was 60% for the survival trial; consequently, survival >40% in each tank would be considered successful. Two airlift pumps were placed in each tank. The two airlift pumps moved a mean±SD of 33.697±5.563 l/min; this produced total tank turnovers through the airlift pumps of 110.65±16.93 min. Water velocities were measured at nine locations in the tanks. Water velocities were 0.0-0.04 m/sec. Dissolved oxygen concentration never went below 6.30 mg/l. The airlift pumps operated flawlessly and required no maintenance. They produced water velocities preferred by the fish and helped keep dissolved oxygen concentration above the permitted minimum (5 mg/l). The airlift pumps will be used in future fish culture activities in these and other tanks. Survival in the three tanks was 78%, 94% and 96%; overall survival was 89.3%. Because take (10.7%) was under the permitted level (60%), the trial was successful.

Douglas Tave; Lawrence Valenzuela; Louie Toya; Alison M. Hutson

2012-01-01

197

Outcomes of buttonhole and rope-ladder cannulation techniques in a tropical renal service.  

UK PubMed Central (United Kingdom)

BACKGROUND: Buttonhole cannulation was introduced into this Queensland Renal Service in 2005. Contrary to published literature, a local review of cannulation outcomes found no greater likelihood of infections with the buttonhole technique. OBJECTIVES: To compare the outcomes of buttonhole and rope-ladder cannulation techniques. DESIGN: Prospective cohort. PARTICIPANTS: Consenting patients attending for haemodialysis via an existing arteriovenous fistula (n?=?104). MEASUREMENTS: Cannulation sites were assessed at every dialysis session for 12 weeks; fear and pain were scored by participants weekly. RESULTS: No statistically significant differences in infection, haematoma formation, pain or fear between the techniques. Occurrence of aneurysm was higher (p?ladder group. More patients in buttonhole group required multiple cannulation attempts (p?ladder group failed to attend their scheduled dialysis sessions (p?

Smyth W; Hartig V; Manickam V

2013-09-01

198

The matrix product approach to quantum spin ladders  

International Nuclear Information System (INIS)

We present a manifestly rotational invariant formulation of the matrix product method valid for spin chains and ladders. We apply it to two-legged spin ladders with spins 1/2, 1 and 3/2 and different magnetic structures labelled by the exchange coupling constants, which can be ferromagnetic or antiferromagnetic along the legs and the rungs of the ladder. We compute ground-state energy densities, correlation lengths and string order parameters. We present numerical evidence of the duality properties of the three different nonferromagnetic spin 1/2 ladders. We show that the long-range topological order characteristic of isolated spin 1 chains is broken by the interchain coupling. The string order correlation function decays exponentially with a finite correlation length that we compute. A physical picture of the spin 1 ladder is given in terms of a collection of resonating spin 1 chains. Finally, for ladders with spin equal to or greater than 3/2 we define a class of AKLT states whose matrix product coefficients are given by 9-j symbols. (author)

1998-12-04

199

Quantum Monte Carlo Study of Weakly Coupled Spin Ladders  

CERN Multimedia

We report a quantum Monte Carlo study of the thermodynamic properties of arrays of spin ladders with various widths ($n$), coupled via a weak inter-ladder exchange coupling $\\alpha J$, where $J$ is the intra-ladder coupling both along and between the chains. This coupled ladder system serves as a simplified model for the magnetism of presumed ordered spin and charge stripes in the two-dimensional CuO$_2$ planes of hole-doped copper oxides. Our results for $n=3$ with weak inter-ladder coupling $\\alpha=0.05$, estimated from the $t-t'-t''-J$ model, show good agreement with the ordering temperature of the recently observed spin density wave condensation in La$_2$CuO$_{4+y}$. We show that there exists a quantum critical point at $\\alpha_c \\simeq 0.07$ for $n=4$, and determine the phase diagram. Our data at this quantum critical point agree quantitatively with the universal scaling predicted by the quantum nonlinear $\\sigma$ model. We also report results on random mixtures of $n=2$ and $n=3$ ladders, which correspo...

Kim, Y J; Kastner, M A; Lee, Y S; Endoh, Y; Shirane, G; Yamada, K

1999-01-01

200

Hood River production program monitoring and evaluation. Report A: Hood River and Pelton Ladder evaluation studies. Annual report for 1996  

International Nuclear Information System (INIS)

In 1992, the Northwest Power Planning Council approved the Hood River and Pelton Ladder master plans within the framework of the Columbia River Basin Fish and Wildlife Program. The master plans define an approach for implementing a hatchery supplementation program in the Hood River subbasin. The hatchery program, as defined in the master plans, is called the Hood River Production Program (HRPP). The HRPP will be implemented at a reduced hatchery production level until (1) the construction of all proposed hatchery facilities has been completed and (2) numbers of returning wild jack and adult fish are sufficient to meet broodstock collection goals. It is anticipated that construction on the hatchery production facilities will be completed by the spring of 1998. The HRPP is jointly implemented by the Oregon Department of Fish and Wildlife (ODFW) and the Confederated Tribes of the Warm Springs (CTWS) Reservation.

1996-01-01

 
 
 
 
201

Walla Walla River Fish Passage Operations Program, 2003-2004 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

In the late 1990s, the Confederated Tribes of the Umatilla Indian Reservation, Oregon Department of Fish and Wildlife, and Washington Department of Fish and Wildlife, along with many other agencies, began implementing fisheries restoration activities in the Walla Walla Basin. An integral part of these efforts is to alleviate the inadequate fish migration conditions in the basin. The migration concerns are being addressed by removing diversion structures, constructing fish passage facilities, implementing minimum instream flow requirements, and providing trap and haul efforts when needed. The objective of the Walla Walla River Fish Passage Operations Project is to increase the survival of migrating adult and juvenile salmonids in the Walla Walla River basin. The project is responsible for coordinating operation and maintenance of ladders, screen sites, bypasses, trap facilities, and transportation equipment. In addition, the project provides technical input on passage criteria and passage and trapping facility design and operation. Operation of the various passage facilities and passage criteria guidelines are outlined in an annual operations plan that the project develops. During the 2003-2004 project year, there were 379 adult summer steelhead (Oncorhynchus mykiss), 36 adult bull trout (Salvelinus confluentus); 108 adult and 3 jack spring chinook (O. tshawytscha) enumerated at the Nursery Bridge Dam fishway video counting window between December 21, 2003, and June 30, 2004. Summer steelhead and spring chinook were observed moving upstream while bull trout were observed moving both upstream and downstream of the facility. In addition, the old ladder trap was operated by the WWBNPME project in order to radio tag spring chinook adults. A total of 2 adult summer steelhead, 4 bull trout, and 23 adult spring chinook were enumerated at the west ladder at Nursery Bridge Dam during the trapping operations between May 6 and May 23, 2004. Operation of the Little Walla Walla River juvenile trap for trap and haul purposes was not necessary this year. The project transported adult spring chinook from Threemile Dam to the South Fork Walla Walla Brood Holding Facility. A total of 239 spring chinook were outplanted in August for natural spawning in the basin.

Bronson, James P. (Confederated Tribes of the Umatilla Indian Reservation, Department of Natural Resources, Pendleton, OR)

2004-12-01

202

Stark ladder resonances for small electric fields  

International Nuclear Information System (INIS)

We prove the existence of resonances in the semi-classical regime of small h for Stark ladder Hamiltonians H(h, F)=-.h2 d2/dx2 +?+Fx in one-dimension. The potential ? is a real periodic function with period ? which is the restriction to R of a function analytic in a strip about R. The electric field strength F satisfies the bounds parallel?'parallel?>F>0. In general, the imaginary part of the resonances are bounded above by cesup(k?Th-1), for some 0Th-1 is the single barrier tunneling distance in the Agmon metric for ?+Fx. In the regime where the distance between resonant wells is O(F-1), we prove that there is at least one resonance whose width is bounded above by ce-?/F, for some ?, c>0 independent of h and F for .h sufficiently small. This is an extension of the Oppenheimer formula for the Stark effect to the case of periodic potentials. (orig.).

1991-01-01

203

Economic integration in the quality ladder model  

Directory of Open Access Journals (Sweden)

Full Text Available Here we perform the same kind of "integration experiments" as in Rivera-Batiz and Romer (1991), this time in the context of a "quality ladder model", where international trade integration is not enough to prevent redundancy of R&D efforts. Thus a further kind of integration is analysed: "financial market integration". We adopt as a setup the Simple Schumpeterian Model in Aghion and Howitt (2005), whose innovation technology differs sharply from the ones conceived by Rivera-Batiz and Romer in that it displays decreasing returns to scale.Realizamos aqui o mesmo tipo de "experimentos de integração" que em Rivera-Batiz e Romer (1991), desta vez no contexto de um modelo de "escada de qualidade", onde integração via comércio internacional não é suficiente para impedir redundância de esforços de P&D. Daí que um tipo adicional de integração seja analisada: "integração financeira". Adotamos como arcabouço o "modelo Schumpeteriano Simples" de Aghion e Howitt (2005), cuja tecnologia de inovação difere claramente daquelas concebidas em Rivera-Batiz e Romer (1991) por exibir retornos decrescentes de escala.

Eduardo Correia de Souza

2008-01-01

204

Ladder Operators for Lamé Spheroconal Harmonic Polynomials  

Directory of Open Access Journals (Sweden)

Full Text Available Three sets of ladder operators in spheroconal coordinates and their respective actions on Lamé spheroconal harmonic polynomials are presented in this article. The polynomials are common eigenfunctions of the square of the angular momentum operator and of the asymmetry distribution Hamiltonian for the rotations of asymmetric molecules, in the body-fixed frame with principal axes. The first set of operators for Lamé polynomials of a given species and a fixed value of the square of the angular momentum raise and lower and lower and raise in complementary ways the quantum numbers $n_1$ and $n_2$ counting the respective nodal elliptical cones. The second set of operators consisting of the cartesian components $hat L_x$, $hat L_y$, $hat L_z$ of the angular momentum connect pairs of the four species of polynomials of a chosen kind and angular momentum. The third set of operators, the cartesian components $hat p_x$, $hat p_y$, $hat p_z$ of the linear momentum, connect pairs of the polynomials differing in one unit in their angular momentum and in their parities. Relationships among spheroconal harmonics at the levels of the three sets of operators are illustrated.

Ricardo Méndez-Fragoso; Eugenio Ley-Koo

2012-01-01

205

Economic integration in the quality ladder model  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Realizamos aqui o mesmo tipo de "experimentos de integração" que em Rivera-Batiz e Romer (1991), desta vez no contexto de um modelo de "escada de qualidade", onde integração via comércio internacional não é suficiente para impedir redundância de esforços de P&D. Daí que um tipo adicional de integração seja analisada: "integração financeira". Adotamos como arcabouço o "modelo Schumpeteriano Simples" de Aghion e Howitt (2005), cuja tecnologia de inovação di (more) fere claramente daquelas concebidas em Rivera-Batiz e Romer (1991) por exibir retornos decrescentes de escala. Abstract in english Here we perform the same kind of "integration experiments" as in Rivera-Batiz and Romer (1991), this time in the context of a "quality ladder model", where international trade integration is not enough to prevent redundancy of R&D efforts. Thus a further kind of integration is analysed: "financial market integration". We adopt as a setup the Simple Schumpeterian Model in Aghion and Howitt (2005), whose innovation technology differs sharply from the ones conceived by Rivera-Batiz and Romer in that it displays decreasing returns to scale.

Souza, Eduardo Correia de

2008-12-01

206

The fish fauna in the fish passage at the Ourinhos Dam, Paranapanema River  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese A composição e abundância da ictiofauna da escada de peixes da barragem de Ourinhos, a mais nova hidrelétrica (fechada em 2005) na sequência de barragens construídas no rio Paranapanema, foram avaliadas três vezes em um ciclo diário, em três períodos de coleta, dois no verão e um no inverno de 2008-2009. A escada foi fechada e esvaziada e os peixes coletados e identificados, antes da devolução da maior parte deles a jusante. A ictiofauna da escada foi compara (more) da à do reservatório de Ourinhos, coletada na mesma época. Vinte e sete espécies e 4862 indivíduos foram coletados na escada. Pimelodus maculatus foi a única espécie migradora coletada, mas em número baixo na escada, onde predominaram espécies sedentárias pequenas. As espécies mais abundantes foram as sedentárias Apareiodon affinis, Bryconamericus stramineus, Astyanax fasciatus e Parodon nasus. Observações feitas na janela da escada revelaram que os peixes realizavam movimentos ascendentes e descendentes. A escada de peixes é um microhabitat habitado por uma abundante associação de organismos bentônicos que é provavelmente usada como recurso alimentar pela ictiofauna na escada. A similaridade entre a ictiofauna no reservatório de Ourinhos e na escada é baixa (26%). A riqueza de espécies migradoras no trecho entre os reservatórios a montante (Chavantes) e a jusante (Salto Grande), antes do fechamento da barragem de Ourinhos (23 espécies) foi reduzida para 16 e 12 espécies, respectivamente em Salto Grande e Ourinhos, depois do fechamento da barragem, e a apenas uma espécie na escada Abstract in english The composition and abundance of the fish assemblage were evaluated in the fish ladder of Ourinhos Dam, the newest dam (closed in 2005) in the cascade of dams constructed on the Paranapanema River. Samplings were carried out three times on a diel cycle, in three sampling periods, two in the warm season and one in the cold season of 2008 - 2009. The ladder was closed and emptied and the entire fish assemblage was sampled and identified. Most individuals were released alive (more) downstream of the dam. The assemblage found in the ladder was compared with the fish fauna sampled in the reservoir and in downstream sites, in the same period. Twenty seven species and a total of 4682 individuals were caught in the ladder. Pimelodus maculatus was the only migratory species, which was caught in low number in the ladder (0.04% of the total captured), where small sedentary species predominated. The most abundant species were the non-migratory Apareiodon affinis, Bryconamericus stramineus, Astyanax fasciatus and Parodon nasus. Individuals observed in the ladder's window were moving up- and down the passage. The fish ladder is a microhabitat inhabited by an abundant association of benthic organisms that is probably used as a food resource for the fish assemblage in the ladder. The similarity between the fish fauna in the ladder and that of the Ourinhos Reservoir was low (26%). The species richness of migrants in the stretch between the uspstream reservoir (Chavantes) and the downstream one (Salto Grande), before the Ourinhos dam closure (23 species) was reduced to 16 and 12 species in Salto Grande and Ourinhos reservoirs, respectively, after the dam closure, and to a single species in the ladder.

Arcifa, Marlene Sofia; Esguícero, André Luiz Henríques

2012-10-01

207

The fish fauna in the fish passage at the Ourinhos Dam, Paranapanema River  

Directory of Open Access Journals (Sweden)

Full Text Available The composition and abundance of the fish assemblage were evaluated in the fish ladder of Ourinhos Dam, the newest dam (closed in 2005) in the cascade of dams constructed on the Paranapanema River. Samplings were carried out three times on a diel cycle, in three sampling periods, two in the warm season and one in the cold season of 2008 - 2009. The ladder was closed and emptied and the entire fish assemblage was sampled and identified. Most individuals were released alive downstream of the dam. The assemblage found in the ladder was compared with the fish fauna sampled in the reservoir and in downstream sites, in the same period. Twenty seven species and a total of 4682 individuals were caught in the ladder. Pimelodus maculatus was the only migratory species, which was caught in low number in the ladder (0.04% of the total captured), where small sedentary species predominated. The most abundant species were the non-migratory Apareiodon affinis, Bryconamericus stramineus, Astyanax fasciatus and Parodon nasus. Individuals observed in the ladder's window were moving up- and down the passage. The fish ladder is a microhabitat inhabited by an abundant association of benthic organisms that is probably used as a food resource for the fish assemblage in the ladder. The similarity between the fish fauna in the ladder and that of the Ourinhos Reservoir was low (26%). The species richness of migrants in the stretch between the uspstream reservoir (Chavantes) and the downstream one (Salto Grande), before the Ourinhos dam closure (23 species) was reduced to 16 and 12 species in Salto Grande and Ourinhos reservoirs, respectively, after the dam closure, and to a single species in the ladder.A composição e abundância da ictiofauna da escada de peixes da barragem de Ourinhos, a mais nova hidrelétrica (fechada em 2005) na sequência de barragens construídas no rio Paranapanema, foram avaliadas três vezes em um ciclo diário, em três períodos de coleta, dois no verão e um no inverno de 2008-2009. A escada foi fechada e esvaziada e os peixes coletados e identificados, antes da devolução da maior parte deles a jusante. A ictiofauna da escada foi comparada à do reservatório de Ourinhos, coletada na mesma época. Vinte e sete espécies e 4862 indivíduos foram coletados na escada. Pimelodus maculatus foi a única espécie migradora coletada, mas em número baixo na escada, onde predominaram espécies sedentárias pequenas. As espécies mais abundantes foram as sedentárias Apareiodon affinis, Bryconamericus stramineus, Astyanax fasciatus e Parodon nasus. Observações feitas na janela da escada revelaram que os peixes realizavam movimentos ascendentes e descendentes. A escada de peixes é um microhabitat habitado por uma abundante associação de organismos bentônicos que é provavelmente usada como recurso alimentar pela ictiofauna na escada. A similaridade entre a ictiofauna no reservatório de Ourinhos e na escada é baixa (26%). A riqueza de espécies migradoras no trecho entre os reservatórios a montante (Chavantes) e a jusante (Salto Grande), antes do fechamento da barragem de Ourinhos (23 espécies) foi reduzida para 16 e 12 espécies, respectivamente em Salto Grande e Ourinhos, depois do fechamento da barragem, e a apenas uma espécie na escada

Marlene Sofia Arcifa; André Luiz Henríques Esguícero

2012-01-01

208

Prediction of stream fish assemblages from land use characteristics: implications for cost-effective design of monitoring programmes.  

UK PubMed Central (United Kingdom)

Increasing human impact on stream ecosystems has resulted in a growing need for tools helping managers to develop conservations strategies, and environmental monitoring is crucial for this development. This paper describes the development of models predicting the presence of fish assemblages in lowland streams using solely cost-effective GIS-derived land use variables. Three hundred thirty-five stream sites were separated into two groups based on size. Within each group, fish abundance data and cluster analysis were used to determine the composition of fish assemblages. The occurrence of assemblages was predicted using a dataset containing land use variables at three spatial scales (50 m riparian corridor, 500 m riparian corridor and the entire catchment) supplemented by a dataset on in-stream variables. The overall classification success varied between 66.1-81.1% and was only marginally better when using in-stream variables than when applying only GIS variables. Also, the prediction power of a model combining GIS and in-stream variables was only slightly better than prediction based solely on GIS variables. The possibility of obtaining precise predictions without using costly in-stream variables offers great potential in the design of monitoring programmes as the distribution of monitoring sites along a gradient in ecological quality can be done at a low cost.

Kristensen EA; Baattrup-Pedersen A; Andersen HE

2012-03-01

209

Evaluation of Fish Passage Sites in the Walla Walla River Basin, 2008  

Energy Technology Data Exchange (ETDEWEB)

In 2008, Pacific Northwest National Laboratory evaluated the Hofer Dam fish screen and provided technical assistance at two other fish passage sites as requested by the Bonneville Power Administration, the Walla Walla Watershed Council, or the Confederated Tribes of the Umatilla Indian Reservation. Evaluation of new sites such as Hofer Dam focuses on their design, construction, operation, and maintenance to determine if they effectively provide juvenile salmonids with safe passage through irrigation diversions. There were two requests for technical assistance in 2008. In the first, the Confederated Tribes of the Umatilla Indian Reservation requested an evaluation of the Nursery Bridge fish screens associated with the fish ladder on the east side of the Walla Walla River. One set of brushes that clean the screens was broken for an extended period. Underwater videography and water velocity measurements were used to determine there were no potential adverse effects on juvenile salmonids when the west set of screens was clean enough to pass water normally. A second request, received from the National Marine Fisheries Service and the Walla Walla Watershed Council, asked for evaluation of water velocities through relatively new head gates above and adjacent to the Eastside Ditch fish screens on the Walla Walla River. Water moving through the head gates and not taken for irrigation is diverted to provide water for the Nursery Bridge fish ladder on the east side of the river. Elevations used in the design of the head gates were incorrect, causing excessive flow through the head gates that closely approached or exceeded the maximum swimming burst speed of juvenile salmonids. Hofer Dam was evaluated in June 2008. PNNL researchers found that conditions at Hofer Dam will not cause impingement or entrainment of juvenile salmonids but may provide habitat for predators and lack strong sweeping flows to encourage juvenile salmonid passage downstream. Further evaluation of velocities at the Eastside Ditch and wasteway gates should occur as changes are made to compensate for the design problems. These evaluations will help determine whether further changes are required. Hofer Dam also should be evaluated again under more normal operating conditions when the river levels are typical of those when fish are emigrating and the metal plate is not affecting flows.

Chamness, Mickie A. [Pacific Northwest National Laboratory

2008-08-29

210

DESIGN AND EVALUATION OF ONE PROTOTYPE OF FISH CULTURE SYSTEM IN SAN CLEMENTE DE TERAPA, MOCTEZUMA, SONORA  

Directory of Open Access Journals (Sweden)

Full Text Available This research will help to design a system of Oreochromis niloticus intensive fish farming in the community San Clemente de Térapa, Moctezuma, Sonora, México, using thermal water from a perennial spring in circular ponds during 12 weeks. Production of O. niloticus is a common practice in aquaculture to local consume, because this specie has an adequate growth rate and feed conversion, also resist critical environmental conditions like temperature, anoxia, and tolerance to water hardness and high organic matter content. This design was according to quality and quantity of water. Body growth and survive was measured, also the farming viability under the particular conditions of the prototype design. Two circular ponds of 4.5 m and 3 m in diameter were installed, where were introduced 800 and 400 masculinized “young fish”, whit an average weight of 0.84 and 0.54 g respectively. Biometrics measured and physicochemical parameters of water were assessment (temperature, dissolved oxygen and pH). At the end of the culture was obtained a survive rate of 98.5% and 98.25 % en each pond respectively, an excellent adaptation of the organisms and an acceptable body mass. This study shows is possible to get positive results under these conditions.

Diana Vázquez-Soto; Hugo Silva-Kurumiya; Uriel Angulo-Corrales; María de la Paz Montañez-Armenta

2011-01-01

211

Walla Walla River Basin Fish Screens Evaluations, 2006 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

Pacific Northwest National Laboratory evaluated Gardena Farms, Little Walla Walla, and Garden City/Lowden II Phase II fish screen facilities and provided underwater videography beneath a leaking rubber dam in the Walla Walla River basin in 2006. Evaluations of the fish screen facilities took place in early May 2006, when juvenile salmonids are generally outmigrating. At the Gardena Farms site, extended high river levels caused accumulations of debris and sediment in the forebay. This debris covered parts of the bottom drum seals, which could lead to early deterioration of the seals and drum screen. Approach velocities were excessive at the upstream corners of most of the drums, leading to 14% of the total approach velocities exceeding 0.4 feet per second (ft/s). Consequently, the approach velocities did not meet National Marine Fisheries Service (NMFS) design criteria guidelines for juvenile fish screens. The Little Walla Walla site was found to be in good condition, with all approach, sweep, and bypass velocities within NMFS criteria. Sediment buildup was minor and did not affect the effectiveness of the screens. At Garden City/Lowden II, 94% of approach velocities met NMFS criteria of 0.4 ft/s at any time. Sweep velocities increased toward the fish ladder. The air-burst mechanism appears to keep large debris off the screens, although it does not prevent algae and periphyton from growing on the screen face, especially near the bottom of the screens. In August 2006, the Gardena Farm Irrigation District personnel requested that we look for a leak beneath the inflatable rubber dam at the Garden City/Lowden II site that was preventing water movement through the fish ladder. Using our underwater video equipment, we were able to find a gap in the sheet piling beneath the dam. Erosion of the riverbed was occurring around this gap, allowing water and cobbles to move beneath the dam. The construction engineers and irrigation district staff were able to use the video footage to resolve the problem within a couple weeks. We had hoped to also evaluate the effectiveness of modifications to louvers behind the Nursery Bridge screens when flows were higher than 350 cubic feet per second, (cfs) but were unable to do so. Based on the one measurement made in early 2006 after the modified louvers were set, it appears the modified louvers may help reduce approach velocities. The auxiliary supply water system gates also control water through the screens. Evaluating the effect of different combinations of gate and louver positions on approach velocities through the screens may help identify optimum settings for both at different river discharges.

Chamness, Mickie; Abernethy, Scott; Tunnicliffe, Cherylyn [Pacific Northwest National Laboratory

2007-01-01

212

Device for treating urinary ladder channel tissue diseases  

UK PubMed Central (United Kingdom)

The utility model relates to a device for treating urinary ladder channel tissue diseases which is used for treating the urinary ladder channel tissue diseases through percutaneously introducing traditional Chinese medicine into the body. The device consists of a barrel for discharging foreign matters, a barrel for introducing the medicine, an auxiliary barrel, an ozone generator, an ultrasonic generator for discharging foreign matters, an ultrasonic medicine oscillator, an ultrasonic generator for introducing the medicine and a special traditional Chinese medicine prescription for treating the urinary ladder channel tissue diseases, wherein the ozone generator, the ultrasonic generator for discharging the foreign matters, the ultrasonic medicine oscillator and the barrel for introducing the medicine are arranged aside the barrel for discharging the foreign matters the ozone generator is communicated with the barrel for discharging the foreign matters, and the barrel for introducing the medicine and the auxiliary barrel through air tubes purified water and traditional Chinese medicinal soup which is used for treating the urinary ladder channel tissue diseases and is prepared in the ultrasonic medicine oscillator are placed in the barrel for introducing the medicine and the ultrasonic generator for introducing the medicine and the auxiliary barrel are further arranged aside the barrel for introducing the medicine. The Chinese medicine molecules of the device are not decomposed, and the device can eliminate dirt in vivo, can treat the urinary ladder channel tissue diseases, and is applicable to the clinical field.

JIANYOU WANG

213

Polysomatic series and superconductivity in complex cuprates with ladder-type structure  

International Nuclear Information System (INIS)

The structure of ladder-type cuprates was considered in polysomatic model. The possibility of the manifestation of superconductivity was estimated considering the structural stability of various cuprates with the ladder-type structure

1998-12-20

214

77 FR 15839 - Culturally Significant Objects Imported for Exhibition Determinations: “Joan Miró: the Ladder of...  

Science.gov (United States)

...for Exhibition Determinations: ``Joan Mir[oacute]: the Ladder of Escape'' SUMMARY: Notice is hereby given of the following...be included in the exhibition ``Joan Mir[oacute]: the Ladder of Escape,'' imported from abroad for temporary...

2012-03-16

215

Polysomatic series and superconductivity in complex cuprates with ladder-type structure  

Energy Technology Data Exchange (ETDEWEB)

The structure of ladder-type cuprates was considered in polysomatic model. The possibility of the manifestation of superconductivity was estimated considering the structural stability of various cuprates with the ladder-type structure.

Leonyuk, L.; Maltsev, V. (Moscow State Univ. (Russian Federation)); Babonas, G.J.; Reza, A. (Semiconductor Physics Inst., Vilnius (Lithuania)); Szymczak, R. (Inst. of Physics, Warsaw (Poland))

1998-12-20

216

Solid-state structural transformations and photoreactivity of 1D-ladder coordination polymers of Pb(II).  

UK PubMed Central (United Kingdom)

An attempt has been made to design double-stranded ladder-like coordination polymers (CPs) of hemidirected Pb(II) . Four CPs, [Pb(?-bpe)(O2 C-C6 H5 )2 ]?2H2 O (1), [Pb2 (?-bpe)2 (?-O2 C-C6 H5 )2 (O2 C-C6 H5 )2 ] (2), [Pb2 (?-bpe)2 (?-O2 C-p-Tol)2 (O2 C-p-Tol)2 ]? 1.5?H2 O (3) and [Pb2 (?-bpe)2 (?-O2 C-m-Tol)2 (O2 C-m-Tol)2 ] (4) (bpe=1,2-bis(4'-pyridyl)ethylene), have been synthesised and investigated for their solid-state photoreactivity. CPs 2-4, having a parallel orientation of bpe molecules in their ladder structures and being bridged by carboxylates, were found to be photoreactive, whereas CP 1 is a linear one-dimensional (1D) CP with guest water molecules aggregating to form a hydrogen-bonded 1D structure. The linear strands of 1 were found to pair up upon eliminating lattice water molecules by heating, which led to the solid-state structural transformation of photostable linear 1D CP 1 into photoreactive ladder CP 2. In the construction of the double-stranded ladder-like structures, the parallel alignment of C?C bonds in 2-4 is dictated by the chelating and ?2 -?(2) :?(1) bridging modes of the benzoate and toluate ligands. The role of solvents in the formation of such double-stranded ladder-like structures has also been investigated. A single-crystal-to-single-crystal transformation occurred when 4 was irradiated under UV light to form [Pb2 (rctt-tpcb)(?-O2 C-m-Tol)2 (O2 C-m-Tol)2 ] (5).

Kole GK; Peedikakkal AM; Toh BM; Vittal JJ

2013-03-01

217

From the Hubbard to the SO(5) Ladder A Numerical Study  

CERN Multimedia

The Hubbard Hamiltonian on a two-chain ladder is studied numerically using quantum Monte Carlo and Exact Diagonalization techniques. A rung interaction, $V$, is turned on such that the resulting model has an exact SO(5) symmetry when $V=-U$. The evolution of the low energy excitation spectrum is presented from the pure Hubbard ladder to the SO(5) ladder. It is shown that the low energy excitations in the pure Hubbard ladder have an approximate SO(5) symmetry.

Duffy, D; Kim, E; Duffy, Daniel; Haas, Stephan; Kim, Eugene

1999-01-01

218

A Monte Carlo study of correlations in quantum spin ladders  

CERN Document Server

We study antiferromagnetic spin--1/2 Heisenberg ladders, comprised of n_c chains (2 \\leq n_c \\leq 6) with ratio J_{\\bot}/J_{\\|} of inter-- to intra--chain couplings. From measurements of the correlation function we deduce the correlation length \\xi(T). For even n_c, the static structure factor exhibits a peak at a temperature below the corresponding spin gap. Results for isotropically coupled ladders (J_{\\bot}/J_{\\|} = 1) are compared to those for the single chain and the square lattice. For J_{\\bot}/J_{\\|} \\leq 0.5, the correlation function of the two--chain ladder is in excellent agreement with analytic results from conformal field theory, and \\xi(T) exhibits simple scaling behavior.

Greven, M; Wiese, U J

1996-01-01

219

Synthesis of DNA Ladder by Polymerase Chain Reaction and Optimization of Yield Using Response Surface Methodology  

Directory of Open Access Journals (Sweden)

Full Text Available A factorial design approach was applied to optimize the PCR yield of 2 kb fragment involved in preparing DNA ladder. On applying response surface methodology, the effect of six independent variables was studied. From this study we concluded that three fold increase was obatainable upon optimization under the following conditions: primer concentration, 10 pmole; number of cycles, 24; Taq concentration, 2.75 U; Mg+2 concentration, 1.97 mM; annealing temperature, 57°C and extension time, 72 sec. A verification of the predicted model revealed a 91.5% accuracy level.

Yasser R. Abdel-Fattah; Ahmed A. Gaballa

2006-01-01

220

Nonlinear sigma model of a spin ladder containing a static single hole  

CERN Multimedia

In this letter we extend the nonlinear sigma model describing pure spin ladders with an arbitrary number of legs to the case of ladders containing a single static hole. A simple immediate application of this approach to classical ladders is worked out.

Rodrigues-Pereira, A; Pires, A S T

2007-01-01

 
 
 
 
221

Corrosion Control Specialist Career Ladder AFSC 53530, 53550, 53570, and 53690. Occupational Survey Report.  

Science.gov (United States)

The report describes the results of a detailed occupational survey of the corrosion control career ladder. Responses to a 457-task, time rating inventory from 1,015 personnel (representing 64 percent of the career field) were analyzed to produce seven specific findings and the career ladder structure. The career ladder includes a variety of jobs…

Air Force Occupational Measurement Center, Lackland AFB, TX.

222

Photochemical synthesis of a ladder diborole: a new boron-containing conjugate material.  

UK PubMed Central (United Kingdom)

Climbing the ladder: Reductive cyclization of alkynyl haloboranes lead to the bis-benzocycloborabutylidene rather than the expected ladder diborole, despite the former being much less thermodynamically favored. Photochemical conversion to the ladder diborole was, however, quite facile upon irradiation at 254 nm.

Araneda JF; Neue B; Piers WE; Parvez M

2012-08-01

223

Ladder operators and differential equations for multiple orthogonal polynomials  

Science.gov (United States)

In this paper, we obtain the ladder operators and associated compatibility conditions for types I and II multiple orthogonal polynomials. These ladder equations extend known results for orthogonal polynomials and can be used to derive the differential equations satisfied by multiple orthogonal polynomials. Our approach is based on Riemann–Hilbert problems and the Christoffel–Darboux formula for multiple orthogonal polynomials, and the nearest-neighbor recurrence relations. As an illustration, we give several explicit examples involving multiple Hermite and Laguerre polynomials, and multiple orthogonal polynomials with exponential weights and cubic potentials.

Filipuk, Galina; Van Assche, Walter; Zhang, Lun

2013-05-01

224

Recent developments of the block-modified ladder theory  

Energy Technology Data Exchange (ETDEWEB)

One of the possible theoretical approaches for describing the physics of electron-positron pairs in the inhomogeneous electron gas is the so-called `quasi-free` Bloch-modified ladder theory. Despite the success of this approach, it contains two very serious deficiencies, namely the complete neglect of the Bloch character of the electron and positron scattering states and of the electron-positron interaction potential. In this contribution, the importance of these Bloch effects for the Bloch modified ladder theory results, especially for the momentum dependence of the positron enhancement in d-band metals, is demonstrated for the first time. (author). 12 refs, 7 figs.

Sormann, H. [Technische Univ., Graz (Austria). Inst. fuer Kernphysik

1993-03-01

225

Crystal growth conditions and structural features of ladder type superconductors  

International Nuclear Information System (INIS)

The single crystals (M2Cu2O3)m(CuO2)n (M = Ca, Sr, Y, Bi) containing the ladder-type plane Cu2O3 were obtained by the flux method using Bi- and Ba-cuprates as fluxes. The single crystals with m/n-values 5/7 and 1/1 were found to be superconducting (SC) with the onset of the transition at 80 K. The regularities of the SC crystals with the ladder-type structure were discussed from the viewpoint of the crystal chemistry.

1999-08-02

226

Efficient infrared upconversion via a ladder-type atomic configuration  

CERN Document Server

We experimentally demonstrate an infrared light at 1529.4nm can be converted into the visible at 780nm with 54% efficiency through a ladder-type atomic configuration in Rb85. In particular, theoretically, we analyze the high efficiency is due to the large nonlinear dispersion of the index of refraction from the off-resonant enhancement in four-wave mixing process. The high efficiency using a ladder-type configuration in hot Rb85 atoms is an important advance in nonlinear optics and quantum information fields.

Ding, Dong-Sheng; Shi, Bao-Sen; Zou, Xu-Bo; Guo, Guang-Can

2012-01-01

227

Piezoelectric biosensor with a ladder polymer substrate coating  

Energy Technology Data Exchange (ETDEWEB)

A piezoelectric biosensor substrate useful for immobilizing biomolecules in an oriented manner on the surface of a piezoelectric sensor has a ladder polymer of polyacrylonitrile. To make the substrate, a solution of an organic polymer, preferably polyacrylonitrile, is applied to the surface of a piezoelectric sensor. The organic polymer is modifying by heating the polymer in a controlled fashion in air such that a ladder polymer is produced which, in turn, forms the attachment point for the biomolecules comprising the piezoelectric biosensor. 3 figs.

Renschler, C.L.; White, C.A.; Carter, R.M.

1998-09-29

228

Notebook Positioning by Perceptual Map and Laddering Method  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this applied paper is to determine positioning of laptops by perceptual map and laddering method. Data collection method was survey using questionnaire. First by using the views of computer experts of selected brands, including Sony, Acer, Asus, Dell and Msi, 5 among 20 attributes, which were considered more important, were selected through application of factor analysis technique. Then, after classification of these features by laddering technique, they were analyzed by using another questionnaire to determine the position of each brand in the perceptual map. We try to show factors and laptop brands position with regard two factors of price and quality in the resulted perceptual map.

Mehdi Zaribaf; Noura Shameli

2012-01-01

229

The ladder problem: Painleve integrability and explicit solution  

Energy Technology Data Exchange (ETDEWEB)

We consider the n-dimensional ladder system, that is the homogeneous quadratic system of first-order differential equations of the form x-dot{sub i} x{sub i}{sigma}{sub j=1}{sup n}a{sub ij}x{sub j},i = 1,n, where (a{sub ij}) = (i + 1 - j), i, j = 1, n, introduced by Imai and Hirata (2002 Preprint nlin.SI/0212007 v1 3). The ladder system is found to be integrable for all n in terms of the Painleve analysis and its solution is explicitly given.

Andriopoulos, K [GEODYSYC, Department of Mathematics, University of the Aegean, 83 200 Karlovassi (Greece); Leach, P G L [GEODYSYC, Department of Mathematics, University of the Aegean, 83 200 Karlovassi (Greece); Nucci, M C [Dipartimento di Matematica e Informatica, Universita di Perugia, 06123 Perugia (Italy)

2003-11-07

230

Crystal growth conditions and structural features of ladder type superconductors  

Energy Technology Data Exchange (ETDEWEB)

The single crystals (M{sub 2}Cu{sub 2}O{sub 3}){sub m}(CuO{sub 2}){sub n} (M = Ca, Sr, Y, Bi) containing the ladder-type plane Cu{sub 2}O{sub 3} were obtained by the flux method using Bi- and Ba-cuprates as fluxes. The single crystals with m/n-values 5/7 and 1/1 were found to be superconducting (SC) with the onset of the transition at 80 K. The regularities of the SC crystals with the ladder-type structure were discussed from the viewpoint of the crystal chemistry.

Leonyuk, L.; Szymczak, R.; Szymczak, H.; Baran, M.; Babonas, G.J.; Maltsev, V.; Shvanskaya, L.; Reza, A.

1999-12-01

231

Open ocean fish farm  

UK PubMed Central (United Kingdom)

An open ocean fish farm based around existing offshore facilities A such as oil or gas rigs which may be active or otherwise. The system contains farmed fish using a bubble curtain and acoustic transponders D, E which also serve to keep out predators. The fish are fed by algae which are grown on site F, G. The system is designed as a whole to have minimal environmental impact, and to substantially reduce, or even eliminate net CO2 emissions from the production of farmed fish, and to substantially increase the availability of fish over and above that which can be harvested using traditional fishing methods.

CHAMBERS MICHAEL

232

Open ocean fish farm  

UK PubMed Central (United Kingdom)

An open ocean fish farm based around the C-Dragon floating wave energy converter system M. The system contains farmed fish using a bubble curtain and acoustic transponders D,E which also serve to keep out predators. The fish are fed by algae which are grown on site F, G. The system is designed as a whole to have minimal environmental impact, and to substantially reduce, or even eliminate net CO2 emissions from the production of farmed fish, and to substantially increase the availability of fish over and above that which can be harvested using traditional fishing methods.

CHAMBERS MICHAEL; CHEASLEY ALAN

233

Fish oil  

Science.gov (United States)

Fish oil can be obtained from eating fish or by taking supplements. Fish that are especially rich in ... acids in about 3.5 ounces of fish. Fish oil supplements are usually made from mackerel, herring, tuna, ...

234

Fish Allergy  

Science.gov (United States)

About Fish Allergy A fish allergy is not exactly the same as a seafood allergy. Seafood includes both fish ( ... medical alert bracelet. Continue What Happens in a Fish Allergy When someone is allergic to fish, the ...

235

New Design of Crypto-Based Pseudo random number generator (CBPRNG) using BLOW FISH cipher  

Directory of Open Access Journals (Sweden)

Full Text Available Random Number Generators (RNGs) are an important building block for algorithms and protocols in cryptography. Random number generation is used in a wide variety of cryptographic operations, such as key generation and challenge/response protocols. A random number generator outputs a sequence of 0s and 1s such that at any position, the next bit cannot be expected on the previous bits. However, true random number produces non- deterministic output since if the same random generator is run twice, identical results are not received. Thus we go for pseudo random number generator that is deterministic device because if this random number generator is run twice or more, it gives same results. Our paper presents new crypto based pseudorandom number generator. It uses BLOW FISH ciphers and the Cipher-Block chaining (CBC) mode that uses three stages of the block chaining. The plain text for each stage comes from the output of the first BLOW FISH, which uses the 64-Bit date and time as the plain text. CBPRNG creates three 64-bit random numbers, the first and the second are concatenated to create a 128-random number and the third is used as next initial vector (IV) for CBPRNG. Our Crypto-Based Pseudo-random Number Generator produces a sequence of bits that has arandom looking distribution. This new generator helps to develop huge range cryptographic applications to increase the system security. A number of applications such as financial security applications and Pretty Good Privacy (PGP) use this technique.

T.Chalama Reddy; Dr.R.Seshadri

2013-01-01

236

Combining a clinical ladder and performance appraisal system as a reward strategy: the EXCEL clinical ladder program.  

UK PubMed Central (United Kingdom)

In response to the dramatic changes occurring in health care today and a desire to reward professional nurses for clinical behaviors that would be valued in the future, Bergan Mercy Medical Center (BMMC) has developed an innovative clinical ladder/performance appraisal system. The BMMC EXCEL Clinical Ladder program, which is based on the developmental model of Patricia Benner, is a competency-based system that uniquely combines a clinical ladder and performance appraisal system. The program is clinically focused and contains optional components in which registered nurses (RNs) can receive additional credit for participation in professional growth and leadership activities. Nurses document examples of their practice through nursing narratives that describe actual clinical situations. The development and implementation processes, challenges encountered, and recommendations for alternative approaches to the implementation of such a unique system are discussed.

Moe JK; Lonowski LR; Yancer DA

1994-09-01

237

Combining a clinical ladder and performance appraisal system as a reward strategy: the EXCEL clinical ladder program.  

Science.gov (United States)

In response to the dramatic changes occurring in health care today and a desire to reward professional nurses for clinical behaviors that would be valued in the future, Bergan Mercy Medical Center (BMMC) has developed an innovative clinical ladder/performance appraisal system. The BMMC EXCEL Clinical Ladder program, which is based on the developmental model of Patricia Benner, is a competency-based system that uniquely combines a clinical ladder and performance appraisal system. The program is clinically focused and contains optional components in which registered nurses (RNs) can receive additional credit for participation in professional growth and leadership activities. Nurses document examples of their practice through nursing narratives that describe actual clinical situations. The development and implementation processes, challenges encountered, and recommendations for alternative approaches to the implementation of such a unique system are discussed. PMID:7922675

Moe, J K; Lonowski, L R; Yancer, D A

1994-09-01

238

Reynolds shear-stress and velocity: positive biological response of neotropical fishes to hydraulic parameters in a vertical slot fishway  

Directory of Open Access Journals (Sweden)

Full Text Available The barriers created by dams can cause negative impacts to aquatic communities, and migratory fish species are directly affected. Fishways have been developed to allow the upstream passage of fishes through dams. In Brazil, after the implementation of environmental laws, these structures have been built based on European and American fishway designs. Studies have shown selectivity for different neotropical fishes in some Brazilian fishways, and the main challenge has been to promote upstream passage of a large number of diverse fish species. The patterns of flow circulation within the fish ladder may explain fish selectivity although few studies detail the fish response to hydraulic characteristics of fish ladder flow. This paper presents a laboratory study, where a vertical slot fishway was built in a hydraulic flume and the behavior of two neotropical fish species (Leporinus reinhardti and Pimelodus maculatus) were analyzed. The structure of flow was expressed in terms of mean velocity, Reynolds shear-stress and velocity fluctuation fields. The individuals of Leporinus reinhardti had higher passage success than Pimelodus maculatus in the laboratory flume. Both species preferred areas of low to zero Reynolds shear-stress values. In addition, different preferences were observed for these species concerning the horizontal components of velocity fluctuation.Interrupções em rios, como as causadas por barragens, provocam impactos negativos sobre as comunidades aquáticas e as espécies migratórias de peixes são diretamente afetadas. A fim de permitir a passagem de peixes, mecanismos de transposição são construídos junto a barramentos. No Brasil, após a implantação de leis ambientais, estas estruturas passaram a ser amplamente construídas e foram baseadas em projetos desenvolvidos na Europa e na América do Norte. Análises de mecanismos já construídos têm mostrado grande seletividade para espécies neotropicais e as demandas da diversa fauna de peixes neotropical são apresentadas como principal desafio ao projeto de passagens para peixes. Os padrões de escoamento dentro de escadas para peixes podem explicar a seletividade destes mecanismos, mas poucos estudos detalham a resposta dos peixes às características hidráulicas encontradas dentro das escadas. Este estudo apresenta uma análise realizada em um laboratório onde foi construída uma escada do tipo ranhura vertical e analisados os comportamentos de duas espécies neotropicais (Leporinus reinhardti e Pimelodus maculatus). O escoamento foi estudado considerando os campos de velocidade média, tensão cisalhante de Reynolds e flutuações de velocidades. Os indivíduos da espécie Leporinus reinhardti apresentaram maior sucesso de passagem do que os da espécie Pimelodus maculatus. Ambas as espécies preferiram áreas de tensão de Reynolds igual a zero. Além disso, diferentes preferências foram observadas para cada espécie em relação às componentes horizontais da flutuação da velocidade.

Bernardo Alan de Freitas Duarte; Isabella Cristina Resende Ramos; Hersília de Andrade e Santos

2012-01-01

239

Reynolds shear-stress and velocity: positive biological response of neotropical fishes to hydraulic parameters in a vertical slot fishway  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Interrupções em rios, como as causadas por barragens, provocam impactos negativos sobre as comunidades aquáticas e as espécies migratórias de peixes são diretamente afetadas. A fim de permitir a passagem de peixes, mecanismos de transposição são construídos junto a barramentos. No Brasil, após a implantação de leis ambientais, estas estruturas passaram a ser amplamente construídas e foram baseadas em projetos desenvolvidos na Europa e na América do Norte. A (more) nálises de mecanismos já construídos têm mostrado grande seletividade para espécies neotropicais e as demandas da diversa fauna de peixes neotropical são apresentadas como principal desafio ao projeto de passagens para peixes. Os padrões de escoamento dentro de escadas para peixes podem explicar a seletividade destes mecanismos, mas poucos estudos detalham a resposta dos peixes às características hidráulicas encontradas dentro das escadas. Este estudo apresenta uma análise realizada em um laboratório onde foi construída uma escada do tipo ranhura vertical e analisados os comportamentos de duas espécies neotropicais (Leporinus reinhardti e Pimelodus maculatus). O escoamento foi estudado considerando os campos de velocidade média, tensão cisalhante de Reynolds e flutuações de velocidades. Os indivíduos da espécie Leporinus reinhardti apresentaram maior sucesso de passagem do que os da espécie Pimelodus maculatus. Ambas as espécies preferiram áreas de tensão de Reynolds igual a zero. Além disso, diferentes preferências foram observadas para cada espécie em relação às componentes horizontais da flutuação da velocidade. Abstract in english The barriers created by dams can cause negative impacts to aquatic communities, and migratory fish species are directly affected. Fishways have been developed to allow the upstream passage of fishes through dams. In Brazil, after the implementation of environmental laws, these structures have been built based on European and American fishway designs. Studies have shown selectivity for different neotropical fishes in some Brazilian fishways, and the main challenge has been (more) to promote upstream passage of a large number of diverse fish species. The patterns of flow circulation within the fish ladder may explain fish selectivity although few studies detail the fish response to hydraulic characteristics of fish ladder flow. This paper presents a laboratory study, where a vertical slot fishway was built in a hydraulic flume and the behavior of two neotropical fish species (Leporinus reinhardti and Pimelodus maculatus) were analyzed. The structure of flow was expressed in terms of mean velocity, Reynolds shear-stress and velocity fluctuation fields. The individuals of Leporinus reinhardti had higher passage success than Pimelodus maculatus in the laboratory flume. Both species preferred areas of low to zero Reynolds shear-stress values. In addition, different preferences were observed for these species concerning the horizontal components of velocity fluctuation.

Duarte, Bernardo Alan de Freitas; Ramos, Isabella Cristina Resende; Santos, Hersília de Andrade e

2012-10-01

240

Nonperturbative Study of Generalized Ladder Graphs in a {var_phi}{sup 2}{chi} Theory  

Energy Technology Data Exchange (ETDEWEB)

The Feynman-Schwinger representation is used to construct scalar-scalar bound states for the set of all ladder and crossed-ladder graphs in a {var_phi}{sup 2}{chi} theory in 3+1 dimensions. The results are compared to those of the usual Bethe-Salpeter equation in the ladder approximation and of several quasipotential equations. Particularly for large couplings, the ladder predictions are seen to underestimate the binding energy significantly as compared to the generalized ladder case, whereas the solutions of the quasipotential equations provide a better correspondence. Results for the calculated bound state wave functions are also presented. {copyright} {ital 1996 The American Physical Society.}

Nieuwenhuis, T.; Tjon, J.A. [Institute for Theoretical Physics, University of Utrecht, Princetonplein 5, P.O. Box 80.006, 3508 TA, Utrecht (The Netherlands)

1996-07-01

 
 
 
 
241

Nonperturbative Study of Generalized Ladder Graphs in a var-phi 2? Theory  

International Nuclear Information System (INIS)

The Feynman-Schwinger representation is used to construct scalar-scalar bound states for the set of all ladder and crossed-ladder graphs in a var-phi 2? theory in 3+1 dimensions. The results are compared to those of the usual Bethe-Salpeter equation in the ladder approximation and of several quasipotential equations. Particularly for large couplings, the ladder predictions are seen to underestimate the binding energy significantly as compared to the generalized ladder case, whereas the solutions of the quasipotential equations provide a better correspondence. Results for the calculated bound state wave functions are also presented. copyright 1996 The American Physical Society.

1996-01-01

242

Chiral symmetry breaking in quantum chromodynamics: The ladder approximation  

Energy Technology Data Exchange (ETDEWEB)

We reexamine the problem of dynamical breaking of chiral symmetry in Quantum Chromodynamics, with the infrared singular gluon propagator, in the ladder approximation. We show that the Dyson-Schwinger equation leads to a singular integral equation which has no nontrivial solutions. It is argued that both ultraviolet and infrared cutoffs must be introduced in order to make the approximate theory viable. (orig.).

Acharya, R. (Physics Dept., Arizona State Univ., Tempe (USA)); Narayana Swamy, P. (Physics Dept., Southern Illinois Univ., Edwardsville (USA))

1990-08-01

243

Does the Missouri Teacher Career Ladder Program Raise Student Achievement?  

Science.gov (United States)

Although Missouri has had a Career Ladder program for teachers since 1987, very little research has been carried out to measure the program's effects and what has been studied has not been comprehensive. This paper examines the program's effect on student achievement across the state, using longitudinal data on district math and reading scores for…

Booker, Kevin; Glazerman, Steven

2009-01-01

244

Undergraduate Education: An Essential Rung on the Rehabilitation Career Ladder  

Science.gov (United States)

This article presents the historical pertinence of undergraduate education to developing a career ladder within the field of vocational rehabilitation. Support for the relevance is presented through the results of an investigation of baccalaureate-level competence and preparation as perceived by graduates of rehabilitation services programs. Job…

Evenson, Tom; Holloway, Linda

2007-01-01

245

Ladder Ising spin configurations. Pt. 1. Heat capacity  

International Nuclear Information System (INIS)

We consider a ladder Ising spin model (with two coupled Ising spin chains), characterized by two couplings (interchain and intrachain couplings), to study in detail, in an analytical way, its thermal behaviour and particularly the variation of the specific heat versus temperature, the ratio of interaction constants, and the magnetic field. It is interesting that when the competition between interchain and intrachain interactions is strong the specific heat exhibits a double peak and when the competition is not so strong the specific heat has a single peak. Further, without entering into details, we give, in a numerical way, some similar results for more complicated ladder configurations (with more than two linear Ising chains). The spin-1/2 ladders or systems of spin chains may be realized in nature by vanadyl pyrophosphate ((VO)2P2O7) or similar materials. All these intermediate systems are today important to gain further insight into the physics of one-dimensional spin chains and two-dimensional high-Tc spin systems, both of which have shown interesting and unusual magnetic and superconducting properties. It is plausible that experimental and theoretical studies of ladders may lead to other interesting physical phenomena. (orig.).

1996-01-01

246

Career Ladder Policy for Teachers: The Case of Ghana  

Science.gov (United States)

In 1984 the Ministry of Education in Ghana introduced a career ladder policy for teachers. While reformers believe that this has improved the condition of the teaching profession, the net gains of the policy remain deceptive. There has even been a reduction in some of the benefits that teachers used to enjoy in the single salary scheme in the…

Osei, George M.

2008-01-01

247

Dynamic fractional Stark ladders in dc-ac fields  

CERN Multimedia

A single band in a spatially periodic system splits into a series of quasienergy subbands under the action of DC-AC fields. These dynamic fractional Stark ladders should be observable in an investigation of optical absorption. PACS: 72.10.Bg, 73.20.Dx

Zhao, X G; Niu, Q; Robert Jahnke; Qian Niu

1993-01-01

248

Antiferromagnetic Ising model saturation field entropies: ladders and kagome lattice  

CERN Document Server

Saturation field entropies of antiferromagnetic Ising models on quasi one-dimensional lattices (ladders) and the kagome lattice are calculated. The former is evaluated exactly by constructing the corresponding transfer matrices, while the latter calculation uses Binder's algorithm for efficiently and exactly computing the partition function of over 1300 spins to give S/k_B = 0.393589(6).

Varma, Vipin Kerala

2013-01-01

249

Jacob's ladders and some new consequences from A. Selberg's formula  

CERN Multimedia

It is proved in this paper that the Jacob's ladders together with the A. Selberg's classical formula (1942) lead to a new kind of formulae for some short trigonometric sums. These formulae cannot be obtained in the classical theory of A. Selberg, and all the less, in the theories of Balasubramanian, Heath-Brown and Ivic.

Moser, Jan

2010-01-01

250

Superconductivity and magnetic properties of spin-ladder compounds  

International Nuclear Information System (INIS)

[en] A review is given of the structural, magnetic and transport studies on two-leg spin-ladder (M2Cu2O3)m(CuO2)n systems (where M are divalent or/and trivalent cations). The crystals belonging to these systems consist of two interpenetrated subsystems. The first subsystem [M2Cu2O3] is composed of (Cu2O3) two-leg ladder planes and M ions coordinated to them. The second subsystem consists of CuO2 1D-chains. In these materials, the superconductivity was discovered for m/n = 1/1, 5/7, 7/10. The intrinsic and extrinsic superconducting properties of spin-ladder systems are presented and discussed in detail. The important role played by the hole transfer from CuO2 planes to the spin-ladder planes is stressed. It is shown that the superconductivity in this new family of high-temperature superconductors should be described as an extreme type II limit. (orig.)

2000-01-01

251

30 CFR 57.11007 - Wooden components of ladders.  

Science.gov (United States)

30 Ç Mineral Resources Ç 1 Ç 2010-07-01 Ç 2010-07-01 Ç false Ç Wooden components of ladders. Ç 57.11007 Ç Section 57.11007 Ç Mineral Resources Ç MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR Ç METAL AND NONMETAL MINE SAFETY AND HEALTH Ç SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL...

2010-07-01

252

30 CFR 56.11007 - Wooden components of ladders.  

Science.gov (United States)

30 Ç Mineral Resources Ç 1 Ç 2010-07-01 Ç 2010-07-01 Ç false Ç Wooden components of ladders. Ç 56.11007 Ç Section 56.11007 Ç Mineral Resources Ç MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR Ç METAL AND NONMETAL MINE SAFETY AND HEALTH Ç SAFETY AND HEALTH STANDARDS-SURFACE METAL...

2010-07-01

253

Gevrey formal power series of Wannier-Stark ladders  

International Nuclear Information System (INIS)

We consider time-independent Schroedinger equations in one dimension with both periodic and Stark potentials. By means of an iterative procedure we obtain a formal power series for the Wannier-Stark ladders. In the case of strongly singular periodic potentials we prove that such a formal power series is of Gevrey type.

2004-02-13

254

D0 Silicon Upgrade: 3 Chip Ladder Heat Transfer  

International Nuclear Information System (INIS)

The Silicon Mechanical group has submitted a 3 chip ladder drawing to the Fermilab Analysis Group (Zhijing Tang) to determine the temperature distribution in the ladder during detector operation. Heat transfer by convection and radiation is assumed negligible and two dimensional PEA conduction solutions were performed. The heat flux at the SVX IT chip region is assumed to be 8.359 mW/mm2 which corresponds to roughly 0.48 W per SVX II chip. The heat flux in the region of the transceiver is assumed 8.801 mW/mm2, corresponding to 1.6 W in this region. Total heat load of the 3 chip ladder is assumed to be 3.04 W. The 3 chip ladder submitted for analysis is shown in the figure below. The multichip module (MCM) is mounted on beryllium plate which serves to carry the heat load of the chips and the transceiver to the cooling channel. Adhesive thermal conductivity is 1.6 W/m-K, based on the published value of the selected adhesive. Actual measurements of thermally conductive adhesives indicate that the assumed 1.6 W/m-K is high. Experience gained in measuring adhesive thermal conductivity indicates 0.9-1.2 W/m-K as a more reasonable number to use. The effect of the uncertainty of the adhesive thermal conductivity on silicon temperature is discussed.

1994-01-01

255

D0 Silicon Upgrade: 3 Chip Ladder Heat Transfer  

Energy Technology Data Exchange (ETDEWEB)

The Silicon Mechanical group has submitted a 3 chip ladder drawing to the Fermilab Analysis Group (Zhijing Tang) to determine the temperature distribution in the ladder during detector operation. Heat transfer by convection and radiation is assumed negligible and two dimensional PEA conduction solutions were performed. The heat flux at the SVX IT chip region is assumed to be 8.359 mW/mm{sup 2} which corresponds to roughly 0.48 W per SVX II chip. The heat flux in the region of the transceiver is assumed 8.801 mW/mm{sup 2}, corresponding to 1.6 W in this region. Total heat load of the 3 chip ladder is assumed to be 3.04 W. The 3 chip ladder submitted for analysis is shown in the figure below. The multichip module (MCM) is mounted on beryllium plate which serves to carry the heat load of the chips and the transceiver to the cooling channel. Adhesive thermal conductivity is 1.6 W/m-K, based on the published value of the selected adhesive. Actual measurements of thermally conductive adhesives indicate that the assumed 1.6 W/m-K is high. Experience gained in measuring adhesive thermal conductivity indicates 0.9-1.2 W/m-K as a more reasonable number to use. The effect of the uncertainty of the adhesive thermal conductivity on silicon temperature is discussed.

Ratzmann, Paul; /Fermilab

1994-09-19

256

Direct Observation of Magnon Fractionalization in the Quantum Spin Ladder  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We measure by inelastic neutron scattering the spin excitation spectra as a function of applied magnetic field in the quantum spin-ladder material (C5H12N)(2)CuBr4. Discrete magnon modes at low fields in the quantum disordered phase and at high fields in the saturated phase contrast sharply with a s...

Thielemann, B; Ruegg, C; Ronnow, H M; Lauchli, A M; Caux, J S; Normand, B; Biner, D; Kramer, K W; Gudel, H U

257

Evolution of the low-energy excitation spectrum from the pure Hubbard ladder to the SO(5) ladder: A numerical study  

Energy Technology Data Exchange (ETDEWEB)

The Hubbard Hamiltonian on a two-leg ladder is studied numerically using quantum Monte Carlo and exact diagonalization techniques. A rung interaction, V, is turned on such that the resulting model has an exact SO(5) symmetry when V={minus}U. The evolution of the low-energy excitation spectrum is presented from the pure Hubbard ladder to the SO(5) ladder. It is shown that the low-energy excitations in the pure Hubbard ladder have an approximate SO(5) symmetry. {copyright} {ital 1998} {ital The American Physical Society}

Duffy, D. [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Haas, S. [Theoretische Physik, ETH-Hoenggerberg, CH-8093 Zurich (Switzerland); Kim, E. [Department of Physics, University of California, Santa Barbara, California 93106 (United States)

1998-09-01

258

Dissipation, voltage profile and Levy dragon in a special ladder network  

Energy Technology Data Exchange (ETDEWEB)

A ladder network constructed by an elementary two-terminal network consisting of a parallel resistor-inductor block in series with a parallel resistor-capacitor block sometimes is said to have a non-dispersive dissipative response. This special ladder network is created iteratively by replacing the elementary two-terminal network in place of the resistors. In this paper, it will be demonstrated that, in fact, non-dispersive dissipative response conclusion of this special ladder network is not accurate for steady-state condition. Furthermore, the voltage profile of this special ladder network exhibits a fractal form called the Levy C curve or Levy dragon in a certain condition. Therefore, this special ladder network may be called the Levy ladder network. This ladder network might be interesting for physics and electrical engineering students and they may encounter when dealing with this network series and parallel combinations of impedances.

Ucak, C [Department of Electrical and Electronics Engineering, Yeditepe University, Istanbul (Turkey)], E-mail: canbolat@yeditepe.edu.tr

2009-09-15

259

Frustrated Hubbard ladders and superconductivity in $\\kappa$-BEDT-TTF organic compounds  

CERN Multimedia

Half-filled two-leg Hubbard ladders have spin-gapped short-range antiferromagnetic correlations while three-leg ladders have power law antoferromagnetic correlations, and both systems have d_{x^2-y^2}-power law pairing correlations when they are doped. Thus these ladders exhibit some of the phenomenology seen in the layered cuprates. Here we report results for half-filled frustrated Hubbard ladders, based upon ladder segments taken from a tight-binding model of kappa-BEDT-TTF. Although these ladders are half-filled, varying the degree of frustration can drive them across an insulator-metal transition. We suggest that the spin, charge and pairing correlations of these frustrated ladders near the insulator-metal transition provide support for the notion that kappa-BEDT-TTF is a strongly correlated superconductor.

Daul, S

1999-01-01

260

Means – End Chain Theory and Laddering Technique: Applications in Consumer Behavior Research  

Directory of Open Access Journals (Sweden)

Full Text Available Means – end chain (MEC) theory and laddering technique uncovers the decision making process of consumers related to marketing offerings such as goods, services and experiences in a cognitive approach from a consumer perspective view which are popularly used approaches in marketing context. The purpose of the study is to discusss and present the laddering techique to Turkish literature, which is a frequently used qualitative research method in consumer behavior, both with related theoretical structure and practice. With this purpose, the overview of the literature within the frame of means – end chain theory, practices in consumer behavior, laddering technique, data collection, data analyze and interperation steps, limits of the laddering technique and alternatives of soft laddering (hard laddering) is discussed. Laddering technique among with alternative data collection tools are anticipated Turkish researchers’ interest.

Ayca Kangal

2013-01-01

 
 
 
 
261

Design and application of two oligonucleotide probes for the identification of Geodermatophilaceae strains using fluorescence in situ hybridization (FISH).  

UK PubMed Central (United Kingdom)

Bacteria of the family of Geodermatophilaceae are actively involved in the decay processes [Urzì, C. and Realini, M. (1998) Int Biodeterior Biodegrad 42: 45-54; Urzì, C., Salamone, P., Schumann, P., and Stackebrandt, E. (2000) Int J Syst Evol Microbiol 50: 529-536] of stone monuments. Characterization of isolates includes phenotypic, chemotaxonomic and genetic analysis often requiring long-term procedures. The use of specific probes for members of Geodermatophilaceae family could be useful for the easy detection of those strains colonizing rock surfaces and involved in the biodeterioration. Two 16S rRNA-targeted oligonucleotide probes were designed for the specific detection of members of the family Geodermatophilaceae using fluorescence in situ hybridization (FISH); one probe specific for members of the two genera Geodermatophilus/Blastococcus and the second for members of the genus Modestobacter.

Urzì C; La Cono V; Stackebrandt E

2004-07-01

262

Modeling of radiation heat transport in complex ladder-like structures placed in rectangular enclosures  

International Nuclear Information System (INIS)

Complex ladder-like structures recently have been considered as the target design for accelerator applications. The decay heat, during a postulated beyond design-basis loss-of-coolant accident in the target where all normal and emergency cooling fails, is removed mainly by radiation heat transfer. Modeling of the radiation transport in complex ladder-like structures has several challenges and limitations when the standard net-radiation model is used. This paper proposes a simplified lumped, or 'hot-rung' model, that considers the worst elements and utilizes the standard net-radiation method. The net-radiation model would under-predict structure temperatures if surfaces were subject to non-uniform radiosity. The proposed model was assessed to suggest corrections to account for the non-uniform radiosity. The non-uniform radiosity effect causes the proposed hot-rung model to under-predict the center-rung temperatures by ?4-74 C when all parametrics, including temperatures up to 1500 C, were considered. These temperatures are small. The proposed model predicted that an important effect of decreasing the emissivity was smoothing of non-isothermal effects. The radiosity effects are more pronounced when there are strong temperature gradients. Uniform rung temperatures tend to decrease the radiosity effects. We concluded that a relatively simple model that is conservative with respect to radiosity effects could be developed. (orig.)

1999-01-01

263

Geometric Summary of the 9 Chip Ladder for the D0 Silicon Tracker  

Energy Technology Data Exchange (ETDEWEB)

Two hybrids types are required to accomodate the flipping of ladders within each bulkhead layer, in order to account for the pigtail routing. Left and right versions are shown below, following the definitions laid out by Mike Matulik. These drawings are not to proper scale in the sketches below. The dimensionally correct versions of the 9 chip hybrids are stored in DCS under drawing number 3823.112-MD-317803 for the lefthanded version, and 3823.112-MD-317804 for the right handed version. Handedness of the hybrids are designated as shown in the figures and table below. There are long and short versions of both the left and the right, for four total 9 chip hdi designs. The pigtail lengths of the long and short are shown in a table in the hybrid drawings which reside in DCS. The chamfer in the hybrid corners (N side) is placed in order to enable the hybrid to be glued to the beryllium substrate, whereas the rectangular cuttout on the same side is to allow direct gluing of a temperature sensor to the substrate metal. The oblong shape on the N side of both hybrids is a 'stay-clear' region (defined in the final drawings) where pressure will be applied to the hybrid during the second stage of ladder construction.

Ratzmann, P.; Cooper, W.; Goloskie, D.; Kowalski, J.; Lipton, R.; Rapidis, P.; Serritella, C.; /Fermilab

1997-11-18

264

Geometric Summary of the 9 Chip Ladder for the D0 Silicon Tracker  

International Nuclear Information System (INIS)

Two hybrids types are required to accomodate the flipping of ladders within each bulkhead layer, in order to account for the pigtail routing. Left and right versions are shown below, following the definitions laid out by Mike Matulik. These drawings are not to proper scale in the sketches below. The dimensionally correct versions of the 9 chip hybrids are stored in DCS under drawing number 3823.112-MD-317803 for the lefthanded version, and 3823.112-MD-317804 for the right handed version. Handedness of the hybrids are designated as shown in the figures and table below. There are long and short versions of both the left and the right, for four total 9 chip hdi designs. The pigtail lengths of the long and short are shown in a table in the hybrid drawings which reside in DCS. The chamfer in the hybrid corners (N side) is placed in order to enable the hybrid to be glued to the beryllium substrate, whereas the rectangular cuttout on the same side is to allow direct gluing of a temperature sensor to the substrate metal. The oblong shape on the N side of both hybrids is a 'stay-clear' region (defined in the final drawings) where pressure will be applied to the hybrid during the second stage of ladder construction.

1997-01-01

265

Modeling of radiation heat transport in complex ladder-like structures placed in rectangular enclosures  

Energy Technology Data Exchange (ETDEWEB)

Complex ladder-like structures recently have been considered as the target design for accelerator applications. The decay heat, during a postulated beyond design-basis loss-of-coolant accident in the target where all normal and emergency cooling fails, is removed mainly by radiation heat transfer. Modeling of the radiation transport in complex ladder-like structures has several challenges and limitations when the standard net-radiation model is used. This paper proposes a simplified lumped, or 'hot-rung' model, that considers the worst elements and utilizes the standard net-radiation method. The net-radiation model would under-predict structure temperatures if surfaces were subject to non-uniform radiosity. The proposed model was assessed to suggest corrections to account for the non-uniform radiosity. The non-uniform radiosity effect causes the proposed hot-rung model to under-predict the center-rung temperatures by {approx}4-74 C when all parametrics, including temperatures up to 1500 C, were considered. These temperatures are small. The proposed model predicted that an important effect of decreasing the emissivity was smoothing of non-isothermal effects. The radiosity effects are more pronounced when there are strong temperature gradients. Uniform rung temperatures tend to decrease the radiosity effects. We concluded that a relatively simple model that is conservative with respect to radiosity effects could be developed. (orig.)

Unal, C.; Bohl, W.R.; Pasamehmetoglu, K.O. [Los Alamos Nat. Lab., NM (United States). Technol. and Safety Assessment Div.

1999-09-01

266

Fish schooling as a basis for vertical axis wind turbine farm design.  

UK PubMed Central (United Kingdom)

Most wind farms consist of horizontal axis wind turbines (HAWTs) due to the high power coefficient (mechanical power output divided by the power of the free-stream air through the turbine cross-sectional area) of an isolated turbine. However when in close proximity to neighboring turbines, HAWTs suffer from a reduced power coefficient. In contrast, previous research on vertical axis wind turbines (VAWTs) suggests that closely spaced VAWTs may experience only small decreases (or even increases) in an individual turbine's power coefficient when placed in close proximity to neighbors, thus yielding much higher power outputs for a given area of land. A potential flow model of inter-VAWT interactions is developed to investigate the effect of changes in VAWT spatial arrangement on the array performance coefficient, which compares the expected average power coefficient of turbines in an array to a spatially isolated turbine. A geometric arrangement based on the configuration of shed vortices in the wake of schooling fish is shown to significantly increase the array performance coefficient based upon an array of 16 x 16 wind turbines. The results suggest increases in power output of over one order of magnitude for a given area of land as compared to HAWTs.

Whittlesey RW; Liska S; Dabiri JO

2010-09-01

267

Fish schooling as a basis for vertical axis wind turbine farm design.  

Science.gov (United States)

Most wind farms consist of horizontal axis wind turbines (HAWTs) due to the high power coefficient (mechanical power output divided by the power of the free-stream air through the turbine cross-sectional area) of an isolated turbine. However when in close proximity to neighboring turbines, HAWTs suffer from a reduced power coefficient. In contrast, previous research on vertical axis wind turbines (VAWTs) suggests that closely spaced VAWTs may experience only small decreases (or even increases) in an individual turbine's power coefficient when placed in close proximity to neighbors, thus yielding much higher power outputs for a given area of land. A potential flow model of inter-VAWT interactions is developed to investigate the effect of changes in VAWT spatial arrangement on the array performance coefficient, which compares the expected average power coefficient of turbines in an array to a spatially isolated turbine. A geometric arrangement based on the configuration of shed vortices in the wake of schooling fish is shown to significantly increase the array performance coefficient based upon an array of 16 x 16 wind turbines. The results suggest increases in power output of over one order of magnitude for a given area of land as compared to HAWTs. PMID:20729568

Whittlesey, Robert W; Liska, Sebastian; Dabiri, John O

2010-08-20

268

Fish schooling as a basis for vertical axis wind turbine farm design  

Energy Technology Data Exchange (ETDEWEB)

Most wind farms consist of horizontal axis wind turbines (HAWTs) due to the high power coefficient (mechanical power output divided by the power of the free-stream air through the turbine cross-sectional area) of an isolated turbine. However when in close proximity to neighboring turbines, HAWTs suffer from a reduced power coefficient. In contrast, previous research on vertical axis wind turbines (VAWTs) suggests that closely spaced VAWTs may experience only small decreases (or even increases) in an individual turbine's power coefficient when placed in close proximity to neighbors, thus yielding much higher power outputs for a given area of land. A potential flow model of inter-VAWT interactions is developed to investigate the effect of changes in VAWT spatial arrangement on the array performance coefficient, which compares the expected average power coefficient of turbines in an array to a spatially isolated turbine. A geometric arrangement based on the configuration of shed vortices in the wake of schooling fish is shown to significantly increase the array performance coefficient based upon an array of 16 x 16 wind turbines. The results suggest increases in power output of over one order of magnitude for a given area of land as compared to HAWTs.

Whittlesey, Robert W; Liska, Sebastian; Dabiri, John O, E-mail: robertw@caltech.ed, E-mail: jodabiri@caltech.ed [Graduate Aeronautical Laboratories, California Institute of Technology, 1200 E California Blvd, MC 205-45, Pasadena, CA 91125 (United States)

2010-09-15

269

Downstream fish passage on Black River system  

International Nuclear Information System (INIS)

[en] Downstream fish passage of juvenile alewife at the Black River hydroelectric system has traditionally been directed by a major screen assembly to a route avoiding altogether four out of five small hydroelectric power plants. This system includes retention of larvae/juveniles in a lake until mid July, diversion of fish via a major screen assembly and by-passing of a station using a fish ladder. However, difficulties with the arrangement have resulted in increasing numbers of fish passing by all five stations. A second option which reduces labour and maintenance activities and promotes increased growth of fish as they pass from reservoir to reservoir involves use of simple fishways coupled with fish pulsers to deflect fish from the station intakes. The fish pulsers use 100 Hz frequency at 20 pulses per minute placed directly in front of the station intake at a depth of 3 m. Both strategies have contributed to increased fish production and migration such that the present run is 5 million to 8 million fish. 4 refs., 4 figs

1989-01-01

270

Personal Fish Sack Carrier  

UK PubMed Central (United Kingdom)

The invention is a fish transport sack specifically designed to transport larger fish such as salmon or steelhead by wading or pedestrian fisherman. The salmon is a large fish approximately 10 to 30 pounds in weight and lengths sometimes exceeding 30 inches. A fish of this size is cumbersome to carry by hand in the traditional method with a stringer, particularly when long distances need to be traversed across rugged terrain such as steep hills and fallen trees. The dangling of the fish on the stringer causes considerable strain on the fisherman's hands, wrist, arms, and shoulders. The discomfort is compounded when several large fish need to be carried simultaneously. The fish sack carrier (10) is of an oblong fish-like shape in order to position the fish in a vertical position with its head downward.; This position reduces strain on the fisherman by evenly distributing the weight on their back and shoulder. A unique suspension system (14) design stabilizes and balances the fish in a comfortable position high upon the fisherman's back, and provides for additional fish sacks (58) to be easily connected to a common shoulder strap and carried simultaneously. The fish sack carrier (10) is constructed of lightweight and durable materials, is washable after use, and can be folded into a small packet for pocket storage.

BERGERS JEFFREY LAWRENCE

271

Study design considerations for assessing the health of fish populations impacted by agriculture in developing countries: a Sri Lankan case study.  

UK PubMed Central (United Kingdom)

Studies on the use of indigenous or endemic fish species for the assessment of agricultural impacts on fish populations are lacking in tropical South and Southeast Asia. This paper describes the steps involved in developing an agricultural impacts assessment program focused on river health, using recent studies on wild fish in Sri Lanka. The assessment methodology includes the selection of fish species for monitoring, and development of a strategy for sample timing, sample size requirements, and selection of appropriate reference site(s). Preliminary fish sampling data from several tributaries of the Uma-oya and the Amban-ganga (Knuckles streams) from the Mahaweli River basin were evaluated and temporal patterns of gonadal recruitment were investigated for three common species: Garra ceylonensis, Devario malabaricus, and Rasbora daniconius. The data on reproductive development were statistically incorporated to evaluate appropriate sample timing and sample size requirements. For this study, we proposed a cluster gradient design with a range of assessment endpoints and suitable statistical methods; an alternate assessment in different agricultural catchments would facilitate verification. The review and preliminary data support provide a template for study design considerations for agricultural impact assessments in South and SE Asian countries.

Sumith JA; Munkittrick KR

2011-08-01

272

One- and Two-Triplon Spectra of a Cuprate Ladder  

CERN Document Server

We have performed inelastic neutron scattering on the near ideal spin-ladder compound La4Sr10Cu24O41, which will serve as a model system for the investigation of doped ladders. A key feature in the analysis was the separation of one-triplon and two-triplon scattering contributions due to an antiphase rung modulation. This enabled extraction of the one-triplon dispersion which has a spin gap of 26.4+/-0.3 meV, and for the first time two-triplon scattering is clearly observed. The exchange constants are determined by fitting the data to be Jleg=186 meV and Jrung=124 meV along the leg and the rung respectively. In addition to the surprisingly large difference between Jleg and Jrung a substantial ring exchange of Jcyc=31 meV was confirmed.

Notbohm, S; Lake, B; Tennant, D A; Schmidt, K P; Uhrig, G S; Hess, C; Klingeler, R; Behr, G; Büchner, B; Reehuis, M; Bewley, R I; Frost, C D; Manuel, P; Eccleston, R S

2006-01-01

273

Superconductivity in two-leg ladder iron selenides  

Science.gov (United States)

Recently, evidence of superconductivity has been discovered in the single-layer potassium-doped iron selenide that consists of weakly coupled two-leg iron ladders (Wei Li et al., arXiv:1210.4619). Using a self-consistent mean-field approximation, we analyze the pairing symmetry and structure of the multi-orbital t-J model defined in these two-leg ladder systems. Similar to the case of the iron pnictides, a modified s-wave pairing state is stabilized by the next-nearest-neighbor superexchange J2. The presence of competing states will be discussed. Our result demonstrates the potential importance of the local magnetic couplings in iron-based superconductors.

Lv, Weicheng; Dagotto, Elbio; Martins, George

2013-03-01

274

Dynamics of an underdamped Josephson-junction ladder  

International Nuclear Information System (INIS)

We show analytically that the dynamical equations for an underdamped ladder of coupled small Josephson junctions can be approximately reduced to the discrete sine-Gordon equation. As numerical confirmation, we solve the coupled Josephson equations for such a ladder in a magnetic field. We obtain discrete-sine-Gordon-like IV characteristics, including a flux flow and a open-quote open-quote whirling close-quote close-quote regime at low and high currents, and voltage steps that represent a lock-in between the vortex motion and linear open-quote open-quote phasons,close-quote close-quote and which are quantitatively predicted by a simple formula. At sufficiently high anisotropy, the fluxons on the steps propagate ballistically. copyright 1996 The American Physical Society.

1996-01-01

275

Blinded Montgomery Powering Ladder Protected Against the Jacobi Symbol Attack  

Directory of Open Access Journals (Sweden)

Full Text Available Recently, many physical attack types (e.g., timing attacks, power consumption attacks, faultattacks) have been developed against cryptosystems, specifically against the modularexponentiation that is the core operation of many security systems. Indeed, there is a real need toeliminate the vulnerabilities of cryptosystems, such as RSA or the Elliptic Curve Cryptosystem,that make them susceptible to such attacks. In 2006, Boreale described a new type of physicalattack based in the Jacobi symbol concept, and later, Schmidt used the same concept as Borealeto break the security of the blinded Montgomery powering ladder. In this paper, a countermeasureagainst Schmidt's attack is presented to make the blinded Montgomery powering ladder resistantto the Jacobi symbol attack.

David Tinoco Varela

2012-01-01

276

Bethe–Salpeter studies of mesons beyond rainbow-ladder  

Directory of Open Access Journals (Sweden)

Full Text Available We investigate the masses of light mesons from a coupled system of Dyson–Schwinger and Bethe– Salpeter equations. We explicitly take into account dominant non-Abelian and sub-leading Abelian contributions to the dressed quark-gluon vertex. We also include unquenching e?ects in the form of hadronic resonance contributions via the back-reaction of pions. We construct the corresponding Bethe–Salpeter kernel that satis?es the axial-vector Ward-Takahashi identity. Our numerical treatment fully includes all momentum dependencies with all equations solved completely in the complex plane. This approach goes well beyond the rainbow-ladder approximation and permits us to investigate the relative impact of di?erent corrections beyond rainbow-ladder on the properties of mesons. We ?nd that sub-leading Abelian corrections are further dynamically suppressed, and that our results supersede early qualitative predictions with signi?cantly simpler truncation schemes.

Williams R.

2010-01-01

277

Design, simulation and performance of a waste heat driven adsorption ice maker for fishing boat  

Energy Technology Data Exchange (ETDEWEB)

An activated carbon-methanol adsorption refrigeration system is tested, in which the performances of a granular bed and a solidified bed are compared. Results are presented and the effects of heat and mass transfer are analyzed. It is proved that the coefficient of performance of refrigeration (COP) is increased by 60% if heat and mass recovery is used for a two-granular-bed system. It is also shown that the heat transfer in a solidified bed is much better than that in a granular bed, but the mass transfer in a solidified bed is critical. Two new adsorbers are designed after analyzing the influence of mass transfer on the performance of the solidified bed, and the arrangement of mass transfer channels is fully taken into account. The simulation of this new designed ice maker shows that the optimal cycle time is about 35 min, and the corresponding specific cooling power (SCP) is SCP=35 W/kg at -10{sup o}C evaporating temperature. The new designed system (two adsorbers, each containing 60 kg activated carbon) is set up and tested; its evaporating temperature is as low as about -15{sup o}C, and its optimal ice production is about 20 kg/h. (author)

Wang, L.W.; Wang, R.Z.; Wu, J.Y.; Xu, Y.X.; Wang, S.G. [Shanghai Jiao Tong University (China). School of Mechanical Engineering

2006-03-01

278

Chirping a two-photon transition in a multistate ladder  

International Nuclear Information System (INIS)

[en] We consider a two-photon transition in a specific ladder system driven by a chirped laser pulse. In the weak field limit, we find that the excited state probability amplitude arises due to interference of multiple quantum paths which are weighted by quadratic phase factors. The excited state population has the form of a Gauss sum which plays a prominent role in number theory

2007-01-01

279

Meson properties from the ladder Bethe-Salpeter equation  

International Nuclear Information System (INIS)

Working in the improved ladder approximation to QCD, we calculate the two point correlation functions for the composite operators anti ?M?. From these we extract mass values and decay constants for the lowest lying scalar, vector and axial vector mesons. Considering the naivety of the approximation used, and that we have no free parameters once the QCD scale is set, the results are surprisingly good. (orig.).

1991-01-01

280

Electronic structure of ladder polysilane and related compounds  

Energy Technology Data Exchange (ETDEWEB)

Electronic structures in the optimized geometries of polycyclotetrasilane, polycyclotetragermane and their alternating copolymer are studied theoretically using the one-dimensional tight-binding self-consistent-field crystal orbital (SCF-CO) method. These polymers have anti and syn ladder structures. The results show that anti-configurations are energetically favorable for these polymers and that anti-conformers have smaller bandgap values and greater [sigma]-conjugation than syn-conformers. (orig.)

Yamaguchi, Yoichi (Sumitomo Electric Industries Ltd., Osaka (Japan). New Chemistry R and D Labs.); Shioya, Jun (Sumitomo Electric Industries Ltd., Osaka (Japan). New Chemistry R and D Labs.)

1993-06-01

 
 
 
 
281

Recurrent variational approach to the two-leg Hubbard ladder  

Energy Technology Data Exchange (ETDEWEB)

We applied the recurrent variational approach to the two-leg Hubbard ladder. At half filling, our variational ansatz was a generalization of the resonating valence-bond state. At finite doping, hole pairs were allowed to move in the resonating valence-bond background. The results obtained by the recurrent variational approach were compared with results from density matrix renormalization group. {copyright} {ital 1999} {ital The American Physical Society}

Kim, E.H. [Department of Physics, University of California, Santa Barbara, California 93106-9530 (United States); Sierra, G. [Instituto de Matematicas y Fisica Fundamental, C.S.I.C., 28006 Madrid (Spain); Duffy, D. [Department of Physics, University of California, Santa Barbara, California 93106-9530 (United States)

1999-08-01

282

Recurrent variational approach to the two-leg Hubbard ladder  

International Nuclear Information System (INIS)

We applied the recurrent variational approach to the two-leg Hubbard ladder. At half filling, our variational ansatz was a generalization of the resonating valence-bond state. At finite doping, hole pairs were allowed to move in the resonating valence-bond background. The results obtained by the recurrent variational approach were compared with results from density matrix renormalization group. copyright 1999 The American Physical Society

1999-01-01

283

Generalized Ladder Operators for Shape-invariant Potentials  

CERN Document Server

A general form for ladder operators is used to construct a method to solve bound-state Schr\\"odinger equations. The characteristics of supersymmetry and shape invariance of the system are the start point of the approach. To show the elegance and the utility of the method we use it to obtain energy spectra and eigenfunctions for the one-dimensional harmonic oscillator and Morse potentials and for the radial harmonic oscillator and Coulomb potentials.

Filho, E D; Filho, Elso Drigo

2001-01-01

284

Magnetic properties of a spin-1 ladder under pressure  

International Nuclear Information System (INIS)

Magnetic properties of an organic spin-1 ladder, BIP-TENO [=3,3',5,5'-tetrakis(N-tert-butylaminoxyl)biphenyl], are presented. Susceptibility measurements at ambient pressure were reexamined and approximate values of the exchange couplings were obtained. A small structural change at around 100 K is suggested, which is suppressed under pressure. The shoulder structure in the susceptibility is retained under pressure.

2007-01-01

285

Slow-speed, reciprocating type high-altitude escape ladder  

UK PubMed Central (United Kingdom)

The utility model discloses a slow reciprocating high altitude escape ladder for solving the problems of realizing high altitude continuous salvations of a plurality of people and controlling the slip velocity of a life-saving rope. The solution is as follows: supporting plates (3) arranged on two sides of a main machine frame of the high altitude escape ladder are provided with movable swinging arms (14), and connecting holes (18) on the movable swinging arms (14) are matched with a main machine connector (36) which supports a fixed supporting part and a main machine body is clamped and in transmission connection with an N-shaped life-saving rope (6) on a load bearing part through a pair of mirror symmetrical driving mechanisms on a positive pressure plate and a negative pressure plate of a controlling part, and a slow lock (7) is arranged on the extending parts of the two ends of the N-shaped life-saving rope (6) respectively and the driving mechanisms on the controlling part are provided with speed regulation parts. The slow reciprocating high altitude escape ladder has the advantages of small volume, light weight, economy and practicality, convenient installation, simplicity and easy operation. The slow reciprocating high altitude escape ladder is applicable to the continuous escape of a plurality of people when fires or dangerous cases happen in a high rise building, and is capable of sending saved people to the ground safely and quickly from windows so that the saved people can evacuate from a danger area quickly.

YAOKUN JIANG

286

Electronic transport through a ladder nanostructure in the presence of network defects  

Directory of Open Access Journals (Sweden)

Full Text Available  The present research studied the electronic transport of an ideal infinite ladder nanostructure in the presence/absence of network defects by using Green’s function method at the tight-binding approximation. The network defects can be simulated by considering a finite ladder which is connected via two contacts to two similar infinite ladders. The results showed that the hopping energy of rungs determines the overlapping region of the ladder conductance channels. By increasing hopping energy of rungs, the allowed energy region of the ladder increases, while the overlapping region shrinks and eventually vanishes. Creation of branched bonds in the center ladder leads, through the system, to a harder electron tunneling. Moreover, the closer electron energy to the system gap edges leads to a better tunneling.

M Mardaani; H Rabani; A Mazloom Shahraki

2012-01-01

287

Electronic transport through a ladder nano structure in the presence of network defects  

International Nuclear Information System (INIS)

[en] The present research studied the electronic transport of an ideal infinite ladder nano structure in the presence/absence of network defects by using Green's function method at the tight-binding approximation. The network defects can be simulated by considering a finite ladder which is connected via two contacts to two similar infinite ladders. The results showed that the hopping energy of rungs determines the overlapping region of the ladder conductance channels. By increasing hopping energy of rungs, the allowed energy region of the ladder increases, while the overlapping region shrinks and eventually vanishes. Creation of branched bonds in the center ladder leads, through the system, to a harder electron tunneling. Moreover, the closer electron energy to the system gap edges leads to a better tunneling.

2012-01-01

288

"Why caipirinha?"- the online via chat laddering technique CAN answer  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english As customers are becoming increasingly connected to the internet, this means that they are available for online interviews, thus opening up a space for investigating research methods, especially qualitative research, in an attempt to identify how to adapt data collecting instruments to the so-called "connected customer era". In this context, the focus of this article is on the application viability analysis of the laddering technique used online and in real-time chat by a (more) sking the following question: "Why caipirinha?". Conducting online in-depth interviews through the MSN Messenger and Skype (the most commonly used chat tools in Brazil), 23 attributes, 22 consequences and 13 values were identified, resulting in 133 ladders, 71 of which reached the value level. Along with friends/mates, Integration, Entertainment and Fun, in addition to Alcohol, Insouciance/ relaxation and Pleasure constitute the most frequent ladders. Concerning the application itself, the participants gave positive feedback, even though some of them did not feel satisfied because they became tired. Convenience, objectivity, disinhibition, easy scheduling and flexibility were identified. The viability of online in-depth interviewing via real-time chats was confirmed, raising the question of the possibility of it achieving other qualitative research techniques.

Bordeaux-Rego, Bruno; Nedwed-Machado, Fernanda; Oliveira, Marta Olivia Rovedder de; Alves, Denise Avancini; Slongo, Luiz Antonio

2011-06-01

289

Magnetization plateau and cusp in S=1 spin ladder  

International Nuclear Information System (INIS)

Recently, the organic compound biphenyl (BIP-TENO) was synthesized and found to be the first S=1 spin ladder. The present high-field measurement up to 70 T indicates that a plateau appears in the magnetization curve at M=Ms/4, where Ms is the saturation magnetization. We propose possible mechanisms of the M=Ms/4 plateau in BIP-TENO. The frustration in the first, second and third neighbor antiferromagnetic exchange interactions in the S=1 ladder yields the M=Ms/4 plateau, with a spontaneous breaking of the translational symmetry. This can be known by use of the degenerate perturbation theory from the strong rung coupling limit. By use of the numerical diagonalization method, we revealed that the most realistic mechanism of the M=Ms/4 plateau in BIP-TENO is due to the third neighbor interaction. Further theoretical analyses suggest the present mechanism should also lead to a cusp in the magnetization curve. The cusp-like anomaly in the experimental magnetization curve is a considerable evidence for our mechanism. We also discuss the Ms/2 plateau problem. We show that a small rung coupling cannot yield the Ms/2 plateau, which is quite different from the M=0 plateau problem of the S=1/2 ladder.

2004-04-30

290

Calculation of tensor susceptibility beyond rainbow-ladder approximation  

International Nuclear Information System (INIS)

In this paper, we extend the calculation of tensor vacuum susceptibility in the rainbow-ladder approximation of the Dyson-Schwinger (DS) approach in Shi et al. (Phys Lett B 639:248, 2006) to that of employing the Ball-Chiu (BC) vertex. The dressing effect of the quark-gluon vertex on the tensor vacuum susceptibility is investigated. Our results show that compared with its rainbow-ladder approximation value, the tensor vacuum susceptibility obtained in the BC vertex approximation is reduced by about 10%. This shows that the dressing effect of the quark-gluon vertex is not large in the calculation of the tensor vacuum susceptibility in the DS approach. In this paper we also demonstrate that the tensor vacuum susceptibility can be used to demarcate the domain of coupling strength within a theory upon which chiral symmetry is dynamically broken. For couplings below the associated critical value and in the absence of confinement, the tensor vacuum susceptibility remains zero. This situation changes until the interaction strength is larger than a critical point. It is found that the critical point in the rainbow-ladder approximation is larger than that in the BC vertex approximation. This is easy to understand, because the effect of the BC vertex itself amounts to enhancing the interaction strength. (author)

2010-01-01

291

Lyapunov exponent in two-leg ladder model  

International Nuclear Information System (INIS)

Lyapunov exponent is one of the properties to study localization-delocalization transition in disordered systems. Perfect as well as disordered two-leg ladder is studied in tight-binding description. In perfectly two-leg ladder two bands are obtained due to symmetric and antisymmetric wave functions. But, the analytical expression of Lyapunov exponent indicates the presence of extended states at the overlapping region of two bands. Beyond this region of energy states are localized. Two models of disordered ladder network are studied here numerically. These studies show that the Lyapunov exponent indicates the presence of extended states provided both the even and odd modes are extended in transmission analysis. If the transmission coefficient shows the localization behavior for one of the modes the Lyapunov exponent also indicates the localization of those states. The behavior of first Lyapunov exponent is consistent with that of the Lyapunov exponent. on the other hand, the study of second Lyapunov exponent is consistent with the transmission analysis.

2010-09-15

292

Task specific adaptations in rat locomotion: runway versus horizontal ladder.  

Science.gov (United States)

In walking quadrupeds the alternating activity pattern of antagonistic leg muscles and the coordination between legs is orchestrated by central pattern generating networks within the spinal cord. These networks are activated by tonic input from the reticular formation in the brainstem. Under more challenging conditions, such as walking on a horizontal ladder, successful locomotion relies upon additional context dependent input from pathways such as the cortico- and rubro-spinal tracts. In this study we used electromyographic and kinematic approaches to characterize the adaptations in the walking pattern in adult uninjured rats crossing a horizontal ladder. We found that the placement of a hind limb on a rung precisely followed the placement of the ipsilateral fore limb. This is different to normal walking where the hind limb is placed behind the position of the ipsilateral fore limb. The increased reach of the hind limbs is achieved by increased flexion of the hip and rotation of the pelvis during the swing phase. Electromyographic observations showed decreased burst duration in Tibialis anterior an ankle flexor muscle. Further changes in the muscle activity pattern were likely due to the reduced stepping frequency during ladder walking. Following a lesion of the dorsal column, containing major parts of the corticospinal tract, we found an increased number of stepping errors and changes in the stepping strategy. The step length of the fore limbs was reduced and the hind limbs were frequently positioned on rungs other than those occupied by the fore limb. PMID:16406145

Bolton, David A E; Tse, Arthur D Y; Ballermann, Mark; Misiaszek, John E; Fouad, Karim

2006-01-10

293

Task specific adaptations in rat locomotion: runway versus horizontal ladder.  

UK PubMed Central (United Kingdom)

In walking quadrupeds the alternating activity pattern of antagonistic leg muscles and the coordination between legs is orchestrated by central pattern generating networks within the spinal cord. These networks are activated by tonic input from the reticular formation in the brainstem. Under more challenging conditions, such as walking on a horizontal ladder, successful locomotion relies upon additional context dependent input from pathways such as the cortico- and rubro-spinal tracts. In this study we used electromyographic and kinematic approaches to characterize the adaptations in the walking pattern in adult uninjured rats crossing a horizontal ladder. We found that the placement of a hind limb on a rung precisely followed the placement of the ipsilateral fore limb. This is different to normal walking where the hind limb is placed behind the position of the ipsilateral fore limb. The increased reach of the hind limbs is achieved by increased flexion of the hip and rotation of the pelvis during the swing phase. Electromyographic observations showed decreased burst duration in Tibialis anterior an ankle flexor muscle. Further changes in the muscle activity pattern were likely due to the reduced stepping frequency during ladder walking. Following a lesion of the dorsal column, containing major parts of the corticospinal tract, we found an increased number of stepping errors and changes in the stepping strategy. The step length of the fore limbs was reduced and the hind limbs were frequently positioned on rungs other than those occupied by the fore limb.

Bolton DA; Tse AD; Ballermann M; Misiaszek JE; Fouad K

2006-04-01

294

Novel organic-inorganic layered oxide with spin ladder structure  

CERN Multimedia

Structural analysis of a layered manganese tungstate diaminoalkane hybrid series suggests that this compound forms a spin-5/2 spin-ladder structure. We use X-ray diffraction, electron microscopy and x-ray absorption spectroscopy results to infer the structure. DC magnetization of the manganese compound and a possible copper analogue appear to show that the manganese system behaves like 1-dimensional antiferromagnetic Heisenberg chains (i.e. $J_{\\parallel} \\gg J_{\\perp})$ while the copper system is fitted well by a $S = {1/2}$ spin ladder model, giving the parameters $g = 1.920 \\pm 0.008$, $J_{\\parallel}/k_B = -0.3 \\pm 1.4$K; $J_{\\perp}/k_B = 213.6 \\pm 1.1$K. The ability to tune adjacent inorganic layers of the hybrid materials by altering the length of the organic `spacer' molecules gives enormous promise for the use of these materials, especially when doped, to provide a greater understanding of spin ladder systems.

Ingham, B; Chong, S V; Liu, R S; Jang, L Y

2005-01-01

295

Correlations and Néel Order of Randomly Diluted Quantum Spin Ladders  

CERN Multimedia

We present a Monte Carlo study of the correlation length $\\xi$ of randomly diluted antiferromagnetic Heisenberg ladders, composed of two spin--1/2 chains. For weak and intermediate inter--chain couplings, $J_{\\bot}/J \\leq 1$, we find an enhancement of correlations that is strongest for a fraction $z^* \\approx J_{\\bot}/(8J)$ of dilutants. We are able to access the experimentally relevant low--temperature regime, $T/J \\approx 1/500$, and find that the recently inferred Néel temperature of $Sr(Cu_{1-z}Zn_z)_2O_3$ corresponds to a curve of constant correlation length $\\xi \\approx 18$ of the single diluted ladder with $J_{\\bot}/J \\alt 1/2$. The primary reason for the Néel ordering is argued to be a strong enhancement of two--dimensional correlations due to a Cu--Sr--Cu exchange coupling of $\\approx 10 meV$ in the stacking direction of the ladders.

Greven, M

1998-01-01

296

Air pollution and the energy ladder in Asian cities  

Energy Technology Data Exchange (ETDEWEB)

Household fuel switching from lower to higher quality fuels, i.e. movements up the ''energy ladder,'' generally leads to substantially lower emissions of health-damaging pollutants. The extent to which human exposures are reduced is difficult to predict, however, because of interactions due to penetration of outdoor pollutants into homes and vice versa. In order to help answer the question of how much exposures might be reduced by movement up the energy ladder, a three-city household air pollution study covering particulates (PM10), nitrogen dioxide (NO[sub 2]), and carbon monoxide (CO) was conducted in and near households spanning the most important current steps in each city's energy ladder. Steps examined were biomass-kerosene-gas in Pune, India; coal-gas in Beijing, China; and charcoal-gas in Bangkok, Thailand. In most instances, 24-hour sampling was conducted and some personal monitoring was undertaken during cooking periods. Preliminary calculations of the exposure and health implications of fuel switching are presented. (Author)

Smith, K.R. (East-West Center, Honolulu, HI (United States)); Apte, M.G. (Lawrence Berkeley Lab., CA (United States)); Ma Yuqing (Tsinghua Univ., Beijing (China)); Wongsekiarttirat, Wathana (Chulalongkorn Univ., Bangkok (Thailand)); Kulkarni, Ashwini (Systems Research Inst., Pune (India))

1994-05-01

297

Cross-ladder effects in Bethe-Salpeter and light-front equations  

Energy Technology Data Exchange (ETDEWEB)

The Bethe-Salpeter (BS) equation in Minkowski space for scalar particles is solved for a kernel given by a sum of ladder and cross-ladder exchanges. The solution of corresponding light-front (LF) equation, where we add the time-ordered stretched boxes, is also obtained. Cross-ladder contributions are found to be very large and attractive, whereas the influence of stretched boxes is negligible. Both approaches -BS and LF- give very close results. (orig.)

Carbonell, J. [Laboratoire de Physique Subatomique et Cosmologie, Grenoble (France); Karmanov, V.A. [Lebedev Physical Institute, Moscow (Russian Federation)

2006-01-15

298

Non-ladder extended renormalization group analysis of the dynamical chiral symmetry breaking  

Energy Technology Data Exchange (ETDEWEB)

The order parameters of dynamical chiral symmetry breaking in QCD, the dynamical mass of quarks and the chiral condensates, are evaluated by numerically solving the non-perturbative renormalization group (NPRG) equations. We employ an approximation scheme beyond 'the ladder', that is, beyond the (improved) ladder Schwinger-Dyson equations. The chiral condensates are enhanced in comparison with the ladder approximation, which is phenomenologically favorable. The gauge dependence of the order parameters is reduced significantly in this scheme. (author)

Aoki, Ken-Ichi; Takagi, Kaoru; Terao, Haruhiko; Tomoyose, Masashi [Kanazawa Univ., Inst. for Theoretical Physics, Kanazawa, Ishikawa (Japan)

2000-04-01

299

Solutions of Bethe-Salpeter and Light-Front equations with cross-ladder kernel  

CERN Multimedia

By method developed in our previous paper we solve the Bethe-Salpeter (BS) equation for the kernel given by sum of ladder and cross-ladder exchanges. We solve also corresponding equation in light-front dynamics (LFD), where we add the time-ordered stretched boxes. Cross-ladder contribution is large and attractive, whereas the influence of stretched boxes is negligible. Both approaches -- BS and LFD -- give very close results.

Carbonell, J

2005-01-01

300

Charge Excitations in Two-Leg Ladders: A tDMRG Approach  

Energy Technology Data Exchange (ETDEWEB)

Abstract We study the dynamics of holon doublon pairs in two-leg Hubbard ladders with the time-dependent Density Matrix Renormalization-Group approach. Benchmark results show that the Krylov algorithm is well suited to calculate the time dependence of observables in these systems. Furthermore, we show that the dynamics of the holon doublon depend strongly on the coupling asymmetry within the ladder, indicating that the ladder geometry plays a role in the decay of these elementary charge excitations.

Dias da Silva, Luis [University of Sao Paulo, BRAZIL; Alvarez, Gonzalo [ORNL; Summers, Michael Stuart [ORNL; Dagotto, Elbio R [ORNL

2013-01-01

 
 
 
 
301

Fish FAQ  

Science.gov (United States)

Northeast Fisheries Science Center answers your question regarding all things fish. Hundreds of fish and other marine fauna questions are answered in the FAQ section. Site also links to several external fish FAQs, as well as other internal and external resources, including kids sites, fish images, species synopses, how to age a fish. The site also features a glossary of fish terms and insight into the different ways fish are caught.

302

Drop Traffic in Microfluidic Ladder Networks with Fore-Aft Structural Asymmetry  

CERN Document Server

We investigate the dynamics of pairs of drops in microfluidic ladder networks with slanted bypasses, which break the fore-aft structural symmetry. Our analytical results indicate that unlike symmetric ladder networks, structural asymmetry introduced by a single slanted bypass can be used to modulate the relative drop spacing, enabling them to contract, synchronize, expand, or even flip at the ladder exit. Our experiments confirm all these behaviors predicted by theory. Numerical analysis further shows that while ladder networks containing several identical bypasses are limited to nearly linear transformation of input delay between drops, mixed combination of bypasses can cause significant non-linear transformation enabling coding and decoding of input delays.

Maddala, Jeevan; Vanapalli, Siva A; Rengaswamy, Raghunathan

2011-01-01

303

Two experimental fish aggregating systems (fads) in the Aegean sea: their design and application  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Duas bóias de aço spar foram construídas e ancoradas em 50 e 100 m de profundidade nas águas do Mar Egeu para dar apoio à pesca recreativa. O primeiro FAD foi implantado nas coordenadas 38°01'48''N 26°58'02''E, a uma distância de 3 milhas náuticas da costa. O outro ficou ancorado a 1,1 milha náutica da costa nas coordenadas 38°03'11''N; 26°59'01''E. Uma âncora (1.2x1.2x0.8 m3), pesando aproximadamente 2,76 toneladas, feita de concreto armado, foi usada para p (more) render um FAD de peso aproximado de 1,5 toneladas. Foram realizados cálculos para determinação das conexões dos FADs, dos cabos e da ancoragem. A interação entre as forças de ondas e correntes com os FADs foi também investigada. No experimento, todas as forças (força de arrasto, força de empuxo, etc) atuantes sobre os FADs foram calculadas. É proposto que para a construção dos FADs deverão ser levados em consideração os seguintes fatores: ondas e correntes, forças relacionadas com os FADs, profundidade de implantação, sistema computacional dos moorings e cordas de amarração. Esse conhecimento proporcionará referência importante para os interessados em realizar projetos que visem aumentar o desempenho e a vida útil dos FADs. Abstract in english Two steel spar buoys were constructed and moored in 50 and 100 m deep of water in the Aegean Sea to support recreational fisheries. The first FAD was deployed at coordinates 38°01´48´´N 26°58´02´´E and at a distance of 3 nautical miles from the shoreline. The other FAD was moored at 1.1 nautical miles from the shoreline at coordinates 38°03´11´´N; 26°59´01´´E. An anchor (1.2x1.2x0.8 m3) weighing approximate 2.76 metric ton, made of reinforced concrete, was (more) used to hold a FAD weighing approximate 1.5 metric ton. Hardware and connections of FADs, ropes, mooring calculation and anchor design were made. The interaction between the forces of wave and current and FADs in those waters was investigated. In the experiment, all forces (drag force, buoyancy force etc.) acting on FADs were calculated. It is proposed that the construction of the FADs should take the following design criteria into consideration: wave and current, forces related to the FADs, deployment depth, mooring hardware and ropes. This knowledge provides an important reference for stakeholders performing projects aiming to increase the performance and service life FADs.

Özgül, Aytaç; Lök, Altan; Düzbastilar, F. Ozan

2011-01-01

304

Two experimental fish aggregating systems (fads) in the Aegean sea: their design and application  

Directory of Open Access Journals (Sweden)

Full Text Available Two steel spar buoys were constructed and moored in 50 and 100 m deep of water in the Aegean Sea to support recreational fisheries. The first FAD was deployed at coordinates 38°01´48´´N 26°58´02´´E and at a distance of 3 nautical miles from the shoreline. The other FAD was moored at 1.1 nautical miles from the shoreline at coordinates 38°03´11´´N; 26°59´01´´E. An anchor (1.2x1.2x0.8 m3) weighing approximate 2.76 metric ton, made of reinforced concrete, was used to hold a FAD weighing approximate 1.5 metric ton. Hardware and connections of FADs, ropes, mooring calculation and anchor design were made. The interaction between the forces of wave and current and FADs in those waters was investigated. In the experiment, all forces (drag force, buoyancy force etc.) acting on FADs were calculated. It is proposed that the construction of the FADs should take the following design criteria into consideration: wave and current, forces related to the FADs, deployment depth, mooring hardware and ropes. This knowledge provides an important reference for stakeholders performing projects aiming to increase the performance and service life FADs.Duas bóias de aço spar foram construídas e ancoradas em 50 e 100 m de profundidade nas águas do Mar Egeu para dar apoio à pesca recreativa. O primeiro FAD foi implantado nas coordenadas 38°01'48''N 26°58'02''E, a uma distância de 3 milhas náuticas da costa. O outro ficou ancorado a 1,1 milha náutica da costa nas coordenadas 38°03'11''N; 26°59'01''E. Uma âncora (1.2x1.2x0.8 m3), pesando aproximadamente 2,76 toneladas, feita de concreto armado, foi usada para prender um FAD de peso aproximado de 1,5 toneladas. Foram realizados cálculos para determinação das conexões dos FADs, dos cabos e da ancoragem. A interação entre as forças de ondas e correntes com os FADs foi também investigada. No experimento, todas as forças (força de arrasto, força de empuxo, etc) atuantes sobre os FADs foram calculadas. É proposto que para a construção dos FADs deverão ser levados em consideração os seguintes fatores: ondas e correntes, forças relacionadas com os FADs, profundidade de implantação, sistema computacional dos moorings e cordas de amarração. Esse conhecimento proporcionará referência importante para os interessados em realizar projetos que visem aumentar o desempenho e a vida útil dos FADs.

Aytaç Özgül; Altan Lök; F. Ozan Düzbastilar

2011-01-01

305

Build-a-Fish  

Science.gov (United States)

In this online interactive game, learners design a fish with the right adaptations to survive in its habitat. Learners select different combinations of adaptations including fish body, mouth, and pattern (color) and then put their selections to the test as they use keyboard arrows to steer and "swim" their fish on the reef. Learners must eat to increase their energy level and avoid predators who will diminish their energy levels.

Aquarium, Shedd; Educational Web Adventures (Eduweb)

2006-01-01

306

Science Career Ladder at the NY Hall of Science: Youth Facilitators as Agents of Inquiry  

Science.gov (United States)

The New York Hall of Science is New York City's hands-on science and technology center, with more than 400 interactive exhibits exploring physics, chemistry, and biology. The Hall also creates and presents demonstrations and programs for students and families, and is the leading provider of professional development in the physical sciences for New York City teachers. The Hall is located in Queens, the most ethnically diverse county in the country. Therefore, a centerpiece of the Hall's efforts to build and support diversity is its Science Career Ladder (SCL): a program that engages young people in a hierarchy of paid experiences in the museum, designed to cultivate interest in science and science education as possible career paths.

Siegel, Eric; Gupta, Preeti

2008-01-01

307

The World Health Organisation analgesic ladder: its place in modern Irish medical practice.  

UK PubMed Central (United Kingdom)

Pain is the single most common reason why patients seek medical care. Worldwide, there are 10 million new cases of cancer each year, with 6 million deaths annually. The World Health Organisation (WHO) first published Cancer Pain Relief in 1986, designed to be a simple, intuitive and accessible guide to the management of cancer pain that would be applicable and useful whatever the language, culture, economy, country and clinical setting. In Ireland today, we have ready access to many different opioids, and the WHO guidelines may seem inadequate and outdated. This article describes the evolution and use of the WHO guidelines, as viewed from the global perspective of its 193 member nations. The WHO ladder still remains valid today in Ireland, even as we await the imminent publication of new evidence-based national cancer pain guidelines this year.

Balding L

2013-04-01

308

Fish tapeworm  

Science.gov (United States)

Fish tapeworm is an infection with a parasite found in fish. ... The fish tapeworm ( Diphyllobothrium latum ), is the largest parasite that infects humans. Humans become infected when they eat raw ...

309

Bio-inspired particle separator design based on the food retention mechanism by suspension-feeding fish  

International Nuclear Information System (INIS)

A new particle separator is designed using a crossflow filtration mechanism inspired by suspension-feeding fish in this study. To construct the model of the bio-inspired particle separator, computational fluid dynamics techniques are used, and parameters related to?separator shape, fluid flow and particle properties that might affect the performance in removing particles from the flow, are varied and tested. The goal is to induce a flow rotation which enhances the separation of particles from the flow, reduce the particle-laden flow that exits via a collection zone at the lower/posterior end of the separator, while at the same time increase the concentration of particles in that flow. Based on preliminary particle removal efficiency tests, an exiting flow through the collection zone of about 8% of the influent flow rate is selected for all the performance tests of the separator including trials with particles carried by air flow instead of water. Under this condition, the simulation results yield similar particle removal efficiencies in water and air but with different particle properties. Particle removal efficiencies (percentage of influent particles that exit through the collection zone) were determined for particles ranging in size from 1 to 1500 µm with a density between 1000 and 1150 kg m?3 in water and 2 and 19 mm and 68 and 2150 kg m?3 in air. As an example, removal efficiencies are 66% and 64% for 707 µm diameter particles with a density of 1040 kg?m?3 in water and for 2 mm particles with a density of 68 kg m?3 in air, respectively. No significant performance difference is found by geometrically scaling the inlet diameter of the separator up or down in the range from 2.5 to 10 cm. (paper)

2012-01-01

310

Walla Walla River Fish Passage Operations Program, 2000-2001 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

In the late 1990's, the Confederated Tribes of the Umatilla Indian Reservation, Oregon Department of Fish and Wildlife, and Washington Department of Fish and Wildlife, along with many other agencies, began implementing fisheries restoration activities in the Walla Walla Basin. An integral part of these efforts is to alleviate the inadequate migration conditions in the basin. The migration concerns are being addressed by removing diversion structures, constructing fish passage facilities, implementing minimum instream flow measures, and initiating trap and haul efforts. The objective of the Walla Walla River Fish Passage Operations Project is to increase the survival of migrating adult and juvenile salmonids in the basin. The project is responsible for coordinating operation and maintenance of ladders, screen sites, bypasses, trap facilities, and transportation equipment. In addition, the project provides technical input on passage criteria and passage and trapping facility design and operation. Operation of the various passage facilities and passage criteria guidelines are outlined in an annual operations plan that the project develops. During the 2000-2001 project year, there were 624 summer steelhead (Oncorhynchus mykiss), 24 bull trout (Salvelinus confluentus), and 47 spring chinook (O. tshawytscha) counted at the Nursery Bridge Dam adult trap between December 27, 2000 and June 7, 2001. The Little Walla Walla River juvenile trap was not operated this year. The project transported 1600 adult spring chinook from Ringold Springs Hatchery to the South Fork Walla Walla Brood Holding Facility and outplanted 1156 for natural spawning in the basin. The project also provided equipment for transportation of juveniles captured during the construction fish salvage at Nursery Bridge Dam.

Zimmerman, Brian C. (Confederated Tribes of the Umatilla Indian Reservation, Department of Natural Resources, Pendleton, OR); Duke, Bill B. (Oregon Department of Fish and Wildlife, Pendleton, OR)

2004-02-01

311

Walla Walla River Fish Passage Operations Program, 2002-2003 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

In the late 1990's, the Confederated Tribes of the Umatilla Indian Reservation, Oregon Department of Fish and Wildlife, and Washington Department of Fish and Wildlife, along with many other agencies, began implementing fisheries restoration activities in the Walla Walla Basin. An integral part of these efforts is to alleviate the inadequate fish migration conditions in the basin. The migration concerns are being addressed by removing diversion structures, constructing fish passage facilities, implementing minimum instream flow requirements, and initiating trap and haul efforts. The objective of the Walla Walla River Fish Passage Operations Project is to increase the survival of migrating adult and juvenile salmonids in the Walla Walla River basin. The project is responsible for coordinating operation and maintenance of ladders, screen sites, bypasses, trap facilities, and transportation equipment. In addition, the project provides technical input on passage criteria and passage and trapping facility design and operation. Operation of the various passage facilities and passage criteria guidelines are outlined in an annual operations plan that the project develops. During the 2002-2003 project year, there were 545 adult summer steelhead (Oncorhynchus mykiss), 29 adult bull trout (Salvelinus confluentus); 1 adult and 1 jack spring chinook (O. tshawytscha) enumerated at the Nursery Bridge Dam fishway adult trap between January 1 and June 23, 2003. Summer steelhead and spring chinook were observed moving upstream while bull trout were observed moving both upstream and downstream of the facility. Operation of the Little Walla Walla River juvenile trap for trap and haul purposes was not necessary this year. The project transported 21 adult spring chinook from Ringold Springs Hatchery and 281 from Threemile Dam to the South Fork Walla Walla Brood Holding Facility. Of these, 290 were outplanted in August for natural spawning in the basin.

Bronson, James P. (Confederated Tribes of the Umatilla Indian Reservation, Department of Natural Resources, Pendleton, OR); Duke, Bill B. (Oregon Department of Fish and Wildlife, Pendleton, OR)

2004-03-01

312

The Washington State Early Childhood Education Career Development Ladder. Policy Brief.  

Science.gov (United States)

This policy brief discusses the Early Childhood Education Career Development Ladder being implemented in Washington State. The initiative institutionalizes a career ladder with wage increments based on experience, job responsibility, and relevant education with a unique mix of public and private funding. The brief builds a case for the career…

Burbank, John R.; Wiefek, Nancy

313

Dissipation, Voltage Profile and Levy Dragon in a Special Ladder Network  

Science.gov (United States)

A ladder network constructed by an elementary two-terminal network consisting of a parallel resistor-inductor block in series with a parallel resistor-capacitor block sometimes is said to have a non-dispersive dissipative response. This special ladder network is created iteratively by replacing the elementary two-terminal network in place of the…

Ucak, C.

2009-01-01

314

The effect of doping a molecular spin ladder with non-magnetic impurities.  

Science.gov (United States)

Since carrier doping of two-leg spin ladders can theoretically induce a superconductive state, investigation of such systems is of great use in the study of superconductivity. In this paper, we report the successful creation of a non-magnetic impurity doped into a two-leg molecular spin ladder and the characterization of its magnetic properties. PMID:24030585

Nishihara, Sadafumi; Zhang, Xiao; Kunishio, Kazuhisa; Inoue, Katsuya; Ren, Xiao-Ming; Akutagawa, Tomoyuki; Kishine, Jun-Ichiro; Fujisawa, Masashi; Asakura, Atsushi; Okubo, Susumu; Ohta, Hitoshi; Nakamura, Takayoshi

2013-10-15

315

The effect of doping a molecular spin ladder with non-magnetic impurities.  

UK PubMed Central (United Kingdom)

Since carrier doping of two-leg spin ladders can theoretically induce a superconductive state, investigation of such systems is of great use in the study of superconductivity. In this paper, we report the successful creation of a non-magnetic impurity doped into a two-leg molecular spin ladder and the characterization of its magnetic properties.

Nishihara S; Zhang X; Kunishio K; Inoue K; Ren XM; Akutagawa T; Kishine JI; Fujisawa M; Asakura A; Okubo S; Ohta H; Nakamura T

2013-09-01

316

Ladder operators and coherent states for nonlinear potentials  

International Nuclear Information System (INIS)

In this work, we make use of deformed operators to construct the coherent states of some nonlinear systems by generalization of two definitions: (i) as eigenstates of a deformed annihilation operator and (ii) by application of a deformed displacement operator to the vacuum state. We also construct the coherent states for the same systems using the ladder operators obtained by traditional methods with the knowledge of the eigenfunctions and eigenvalues of the corresponding Schroedinger equation. We show that both methods yield coherent states with identical algebraic structure. (paper)

2011-10-28

317

The phonon and thermal properties of a ladder nanostructure  

Directory of Open Access Journals (Sweden)

Full Text Available  In this paper, we study the phonon thermal properties of a ladder nanostructure in harmonic approximation. We present a model consisting of two infinite chains with different masses. Then, we investigate the effect of different masses on the phonon spectrum. Moreover, as a specific case, in the absence of the second neighbor interaction, we calculate the phonon density of states/modes. Finally, we consider the thermal conductivity of the system. The results show that the phonon spectrum shifts down to the lower frequencies by increasing the masses. Furthermore, a frequency gap appears in the phonon spectrum. By increasing the springs constants, the thermal conductance decreases.

M Mardaani; H Rabani; M Keshavarz

2011-01-01

318

Orbital coupled dipolar fermions in an asymmetric optical ladder  

Science.gov (United States)

We study a quantum ladder of interacting fermions with coupled s and p orbitals. Such a model describes dipolar molecules or atoms loaded into a double-well optical lattice, dipole moments being aligned by an external field. The two orbital components have distinct hoppings. The tunneling between them is equivalent to a partial Rashba spin-orbital coupling when the orbital space (s, p) is identified as spanned by pseudospin 1/2 states. A rich phase diagram, including incommensurate orbital density wave, pair density wave, and other exotic superconducting phases, is proposed with bosonization analysis. In particular, superconductivity is found in the repulsive regime.

Li, Xiaopeng; Liu, W. Vincent

2013-06-01

319

Quantum spin ladder systems associated with SU(2|2)  

Energy Technology Data Exchange (ETDEWEB)

Two integrable quantum spin ladder systems will be introduced associated with the fundamental SU 92/20 solution of the Yang-baxter equation. The first model is a generalized quantum Ising system with Ising rung interactions. In the second model the addition of extra interactions allows us to impose Heisenberg rung interactions without violating integrability. The existence of a Bethe ansatz solution for both models allows us to investigate the elementary excitations for antiferromagnetic rung couplings. We find that the first model does not show a gap whilst in the second case there is a gap for all positive values of the rung coupling. (author)

Foerster, A. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica]. E-mail: angela@if.ufrgs.br; Hibberd, K.E. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]. E-mail: keh@cbpf.br; Links, J.R. [Queensland Univ., St. Lucia, QLD (Australia). Centre for Mathematical Physics, Dept. of Mathematics]. E-mail: jrl@maths.uq.edu.au; Roditi, I. [State Univ. of New York, Stony Brook (United States). C.N. Yang Inst. for Theoretical Physics]. E-mail: roditi@cbpf.br

2000-12-01

320

Azygos ladder and looped thoracic duct – a case report  

Directory of Open Access Journals (Sweden)

Full Text Available Knowledge of variations in the posterior mediastinum close to the vertebral column is important for cardiothoracic surgeons, radiologists and orthopedic surgeons. We report variations of azygos veins and thoracic duct. The azygos system of veins showed a ladder pattern. The hemiazygos and accessory hemiazygos veins communicated with the azygos vein through six transverse channels across the vertebral column. The accessory hemiazygos and hemiazygos veins joined to form a common channel which opened into the azygos vein. The thoracic duct gave two branches in the posterior mediastinum and these branches joined to form a loop.

Kumar N; Nayak SB; Shetty S; Somayaji SN

2011-01-01

 
 
 
 
321

Evidence for a superfluid density in t-J ladders  

CERN Document Server

Applying three independent techniques, we give numerical evidence for a finite superfluid density in isotropic hole-doped t--J ladders: We show the existence of anomalous flux quantization, emphasising the contrasting behaviour to that found in the `Luttinger liquid' regime stabilised at low electron densities; We consider the nature of the low-lying excitation modes, finding the 1-D analog of the superconducting state; And using a density matrix renormalization group approach, we find long range pairing correlations and exponentially decaying spin-spin correlations.

Hayward, C A; Scalapino, D J; Hanke, W; Hayward, C A; Poilblanc, D; Scalapino, D J; Hanke, W

1995-01-01

322

Ladder operators and recursion relations for the associated Bessel polynomials  

International Nuclear Information System (INIS)

[en] Introducing the associated Bessel polynomials in terms of two non-negative integers, and under an integrability condition we simultaneously factorize their corresponding differential equation into a product of the ladder operators by four different ways as shape invariance symmetry equations. This procedure gives four different pairs of recursion relations on the associated Bessel polynomials. In spite of description of Bessel and Laguerre polynomials in terms of each other, we show that the associated Bessel differential equation is factorized in four different ways whereas for Laguerre one we have three different ways

1939-01-00

323

Ladder operators and recursion relations for the associated Bessel polynomials  

Energy Technology Data Exchange (ETDEWEB)

Introducing the associated Bessel polynomials in terms of two non-negative integers, and under an integrability condition we simultaneously factorize their corresponding differential equation into a product of the ladder operators by four different ways as shape invariance symmetry equations. This procedure gives four different pairs of recursion relations on the associated Bessel polynomials. In spite of description of Bessel and Laguerre polynomials in terms of each other, we show that the associated Bessel differential equation is factorized in four different ways whereas for Laguerre one we have three different ways.

Fakhri, H. [Institute for Studies in Theoretical Physics and Mathematics (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of) and Department of Theoretical Physics and Astrophysics, Physics Faculty, Tabriz University, PO Box 51666-16471, Tabriz (Iran, Islamic Republic of)]. E-mail: hfakhri@ipm.ir; Chenaghlou, A. [Institute for Studies in Theoretical Physics and Mathematics (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of) and Physics Department, Faculty of Science, Sahand University of Technology, PO Box 51335-1996, Tabriz (Iran, Islamic Republic of)]. E-mail: a.chenaghlou@sut.ac.ir

2006-10-30

324

The QCD gluon ladders and HERA structure function  

CERN Document Server

We report on the extension of the data fitting considering the QCD inspired model based on the summation of gluon ladders applied to the $ep$ scattering. In lines of a two Pomeron approach, the structure function $F_2$ has a hard piece given by the model and the remaining soft contribution: a soft Pomeron and non-singlet content. In this contribution, we carefully estimate the relative role of the hard and the soft pieces from a global fit in a large span of $x$ and $Q^2$.

Lengyel, A I

2002-01-01

325

Ladder-QCD at finite isospin chemical potential  

Energy Technology Data Exchange (ETDEWEB)

We use an effective QCD model (ladder-QCD) to explore the phase diagram for chiral symmetry breaking and restoration at finite temperature with different u,d quark chemical potentials. In agreement with a recent investigation based on the Nambu-Jona-Lasinio model, we find that a finite pion condensate shows up for high enough isospin chemical potential {mu}{sub I}=({mu}{sub u}-{mu}{sub d})/2. For small {mu}{sub I} the phase diagram in the ({mu}{sub B},T) plane shows two first order transition lines and two critical ending points.

Barducci, A.; Pettini, G.; Ravagli, L.; Casalbuoni, R

2003-07-10

326

Ladder-QCD at finite isospin chemical potential  

International Nuclear Information System (INIS)

We use an effective QCD model (ladder-QCD) to explore the phase diagram for chiral symmetry breaking and restoration at finite temperature with different u,d quark chemical potentials. In agreement with a recent investigation based on the Nambu-Jona-Lasinio model, we find that a finite pion condensate shows up for high enough isospin chemical potential ?I=(?u-?d)/2. For small ?I the phase diagram in the (?B,T) plane shows two first order transition lines and two critical ending points.

2003-07-10

327

Optical Spectra of the Jaynes-Cummings Ladder  

International Nuclear Information System (INIS)

We explore how the Jaynes-Cummings ladder transpires in the emitted spectra of a two-level system in strong coupling with a single mode of light. We focus on the case of very strong coupling, that would be achieved with systems of exceedingly good quality (very long lifetimes for both the emitter and the cavity). We focus on the incoherent regime of excitation, that is realized with semiconductors quantum dots in microcavities, and discuss how reasonable is the understanding of the systems in terms of transitions between dressed states of the Jaynes-Cummings Hamiltonian.

2009-06-29

328

Gluon ladders in pp (pp-bar) collisions  

Energy Technology Data Exchange (ETDEWEB)

Full text follows: We study the contribution of a finite sum of gluon ladders to the hadronic processes showing that a reliable description is obtained using two order on perturbation theory. The pp(pp-bar) total cross sections are described with good agreement, consistent with unitarity bound. We also calculate the elastic scattering amplitude at non zero momentum transfer t, introducing two distinct Ansatz for the proton impact factor. As a by product the elastic differential cross section is obtained at small t approximation and compared with the data. (author)

Machado, Magno Valerio Trindade; Ducati, Maria Beatriz Gay [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)

2000-07-01

329

Gluon ladders in pp (pp-bar) collisions  

International Nuclear Information System (INIS)

Full text follows: We study the contribution of a finite sum of gluon ladders to the hadronic processes showing that a reliable description is obtained using two order on perturbation theory. The pp(pp-bar) total cross sections are described with good agreement, consistent with unitarity bound. We also calculate the elastic scattering amplitude at non zero momentum transfer t, introducing two distinct Ansatz for the proton impact factor. As a by product the elastic differential cross section is obtained at small t approximation and compared with the data. (author)

2000-01-01

330

Spectrum of a Magnetized Strong-Leg Quantum Spin Ladder  

Science.gov (United States)

Inelastic neutron scattering is used to measure the spin excitation spectrum of the Heisenberg S=1/2 ladder material (C7H10N)2CuBr4 in its entirety, both in the gapped spin liquid and the magnetic field-induced Tomonaga-Luttinger spin liquid regimes. A fundamental change of the spin dynamics is observed between these two regimes. Density matrix renormalization group calculations quantitatively reproduce and help understand the observed commensurate and incommensurate excitations. The results validate long-standing quantum field-theoretical predictions but also test the limits of that approach.

Schmidiger, D.; Bouillot, P.; Guidi, T.; Bewley, R.; Kollath, C.; Giamarchi, T.; Zheludev, A.

2013-09-01

331

Andreev scattering in the asymmetric ladder with preformed pairs  

CERN Document Server

We discuss the phase coherence which emanates from the ladder-like proximity effect between a ``weak superconductor'' with preformed bosonic pairs (here, a single-chain Luther-Emery liquid with superconducting correlations that decay approximately as $x^{-1}$) and a Fermi gas with unpaired fermions. Carefully studying tunneling mechanism(s), we show that the boson-mediated Cooper pairing between remaining unpaired electrons results in a quasi long-range superconductivity: Superconducting correlations decay very slowly as $x^{-\\eta}$ with $\\eta\\approx 1/2$. This process is reminiscent of the coupling of fermions to preformed bosonic pairs introduced in the context of high-$T_c$ cuprates.

Le Hur, K

2001-01-01

332

Exact solutions and ladder operators for a new anharmonic oscillator  

Energy Technology Data Exchange (ETDEWEB)

In this Letter, we propose a new anharmonic oscillator and present the exact solutions of the Schrodinger equation with this oscillator. The ladder operators are established directly from the normalized radial wave functions and used to evaluate the closed expressions of matrix elements for some related functions. Some comments are made on the general calculation formula and recurrence relation for off-diagonal matrix elements. Finally, we show that this anharmonic oscillator possesses a hidden symmetry between E(r) and E(ir) by substituting r->ir.

Dong Shihai [Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Lazaro Cardenas 152, 07730 Mexico DF (Mexico)]. E-mail: dongsh2@yahoo.com; Sun Guohua [Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas, UNAM, A.P. 20-726, Del. Alvaro Obregon, 01000 Mexico DF (Mexico); Lozada-Cassou, M. [Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Lazaro Cardenas 152, 07730 Mexico DF (Mexico)

2005-06-06

333

Ladders in a magnetic field a strong coupling approach  

CERN Multimedia

We show that non-frustrated and frustrated ladders in a magnetic field can be systematically mapped onto an XXZ Heisenberg model in a longitudinal magnetic field in the limit where the rung coupling is the dominant one. This mapping is valid in the critical region where the magnetization goes from zero to saturation. It allows one to relate the properties of the critical phase ($H_c^1$, $H_c^2$, the critical exponents) to the exchange integrals and provide quantitative estimates of the frustration needed to create a plateau at half the saturation value for different models of frustration.

Mila, F

1998-01-01

334

Improving fish survival through turbines  

International Nuclear Information System (INIS)

[en] Much of what is known about fish passage through hydroturbines has been developed by studying migratory species of fish passing through large Kaplan turbine units. A review of the literature on previous fish passage research presented in the accompanying story illustrates that studies have focused on determining mortality levels, rather than identifying the causal mechanism involved. There is a need for understanding how turbine designs could be altered to improve fish passage conditions, how to retrofit existing units, and how proposed hydro plant operational changes may affect fish survival. The US Army Corps of Engineers has developed a research program to define biologically based engineering criteria for improving fish passage conditions. Turbine designs incorporating these criteria can be evaluated for their effects on fish survival, engineering issues, costs, and power production. The research program has the following objectives: To gain a thorough knowledge of the mechanisms of fish mortality; To define the biological sensitivities of key fish species to these mechanisms of mortality; To develop new turbine design criteria to reduce fish mortality; To construct prototype turbine designs, and to test these designs for fish passage, hydro-mechanical operation, and power production; and To identify construction and power costs associated with new turbine designs

1993-01-01

335

Assembly procedure for the silicon pixel ladder for PHENIX silicon vertex tracker  

International Nuclear Information System (INIS)

The silicon vertex tracker (VTX) will be installed in the summer of 2010 to enhance the physics capabilities of the Pioneering High Energy Nuclear Interaction eXperiment (PHENIX) experiment at Brookhaven National Laboratory. The VTX consists of two types of silicon detectors: a pixel detector and a strip detector. The pixel detector consists of 30 pixel ladders placed on the two inner cylindrical layers of the VTX. The ladders are required to be assembled with high precision, however, they should be assembled in both cost and time efficient manner. We have developed an assembly bench for the ladder with several assembly fixtures and a quality assurance (Q/A) system using a 3D measurement machine. We have also developed an assembly procedure for the ladder, including a method for dispensing adhesive uniformly and encapsulation of bonding wires. The developed procedures were adopted in the assembly of the first pixel ladder and satisfy the requirements.

2009-07-21

336

Multicriteria assessment in restoring migratory fish stocks in the river Iijoki; Monitavoitearviointi Iijoen vaelluskalakantojen palauttamisen tukena  

Energy Technology Data Exchange (ETDEWEB)

The Iijoki is one of Finland's most important former salmon rivers. Construction of multiple main stem dams on the river in the 1960s effectively blocked the migration corridors of migratory fish. Suitable spawning and nursery habitats above the dams span an estimated 600-800 hectares. With riverside residents are very much in favour of the return of migratory fish, watershed planning for this has been set as a target. Such measures are rendered urgent by the fact that there is still a possibility of replenishing the Iijoki's own salmon stock, thereby restoring the fishes' natural lifecycle and natural selection. This report has been completed as part of the project 'The return of migratory fish to the River Iijoki (2008-2010)', where the main object was reconciling the target of enhancing the natural life cycle of migratory fish with the continued generation of hydropower. Under a multicriteria assessment, various alternatives and measures for improving migratory fish stocks were clarified and their desirability, costs and benefits systematically and transparently evaluated. Furthermore, interest groups' views of the three options and their effects (as distinct from the expert evaluation) were clarified with the help of computer aided interviews. The alternatives were transferring salmon above the main stem dams and two fish-ladder options. The multicriteria assessment viewed the construction of fish ladders, alongside other large-scale support measures, as the best option. Based on all of the criteria applied in a cost-benefit analysis, the stock transfer alternative was the most economically viable, because its net product value was positive in all cases. The fish ladder options were the most expensive due to the construction costs involved, but they also provided the greatest benefits. Above all, fish ladder construction is supported by the fact that it would return migratory fish to their natural lifecycle and attain the EU's watershed planning objectives. In addition, its effects on local identity, fishing tourism and the attractiveness of the area speak in its favour. With respect to the return of migratory fish, the greatest uncertainties lie in developments in the state of the Baltic Sea and the regulation of fishing. A multicriteria assessment helped the respondents and stakeholders achieve a better overall understanding of the planning situation and the various parties' objectives and views. This assisted in creating common ground in building a co-management model to establish further measures for the return of migrant fish. (orig.)

Karjalainen, T.P.; Rytkoenen, A.-M.; Marttunen, M.; Maeki-Petaeys, A.; Autti, O.

2011-05-15

337

Perspectives on fish impingement  

International Nuclear Information System (INIS)

Data on fish impingement and related parameters are being gathered at a large number of power stations throughout the country at substantial monetary and manpower costs. A national survey of fish impingement at power plants was conducted and much of the information compiled in a standardized format--an effort that we think will aid in planning improvements in the design, siting, and operation of the cooling-water intakes. This paper examines the objectives of the fish impingement studies, monitoring programs, variables affecting fish impingement, siting and design criteria, state-of-the-art of screening systems, and suggestions for meeting 316(b) requirements. It also discusses where the emphasis should be placed in future fish-impingement related activities

1977-12-07

338

The Doped t-J Ladder via series expansions  

International Nuclear Information System (INIS)

Full text: We have developed a new series expansion approach for calculating the zero-temperature properties of lattice electron models for arbitrary finite doping. This is done by introducing particle fluctuation terms in the Hamiltonian, within perturbation theory. The method is demonstrated by application to the 2-chain t-J ladder. This model has been extensively studied, in connection with materials such as SrCu2O3. There is evidence that some of these systems become superconducting upon doping. Results will be presented for the ground state energy, chemical potential, and spin excitations. Comparisons with previous work will be given. We have also recently developed a series expansion method for calculating precisely the spectra of two-particle bound states, and here we apply this new technique to study the dynamic properties of 2-holes doped into the t-J ladder. The overall 2-hole spectrum is much richer than that obtained in previous studies. Several singlet and triplet bound/antibound states are found. The number of bound states depends on the coupling constants as well as the wavevector

2002-01-01

339

Renormalization group calculations with kparallel dependent couplings in a ladder  

International Nuclear Information System (INIS)

We investigate the phase diagram of a ladder system (two chains, with a Hubbard interaction U and an interband coupling tperpendicular). It is already known [M. Fabrizio, Phys. Rev. B 48 (1993) 15838] that backward interband scattering (gb) plays a particular role in this system. Moreover, some authors (for instance [H.J. Schulz, Phys. Rev. B 53 (1996) R2959]) have early pointed out that, because of this coupling gb, parallel momentum (kparallel) dependence could not be neglected. So we have introduced an original method to include kparallel dependence of couplings, in a RG calculation using the one particle irreducible (OPI) scheme. We calculate different susceptibilities, which are classified according to their symmetries. Our results depend on whether we include kparallel dependence or not. When we include this dependence, we observe a region with large antiferromagnetic fluctuations, in the vicinity of small tperpendicular, followed by a superconducting region with a simultaneous divergence of the spin density waves channel. The region with only spin density wave fluctuations disappears, when kparallel dependence is neglected. Altogether, our results prove that k-bar is an influential variable in the renormalization group flow, for a ladder.

2006-05-01

340

Feasibility study and preliminary design for fishing (TUNA) vessel fuel storage and distribution. Final report. Export trade information  

Energy Technology Data Exchange (ETDEWEB)

The report is divided into the following sections: (1) Introduction; (2) Conclusions and Recommendations; (3) Existing Conditions and Facilities for a Fuel Distribution Center; (4) Pacific Ocean Regional Tuna Fisheries and Resources; (5) Fishing Effort in the FSMEEZ 1992-1994; (6) Current Transshipping Operations in the Western Pacific Ocean; (7) Current and Probale Bunkering Practices of United States, Japanese, Koren, and Taiwanese Offshore-Based Vessels Operating in FSM and Adjacent Waters; (8) Shore-Based Fish-Handling/Processing; (9) Fuels Forecast; (10) Fuel Supply, Storage and Distribution; (11) Cost Estimates; (12) Economic Evaluation of Fuel Supply, Storage and Distribution.

NONE

1995-07-01

 
 
 
 
341

Fishing pole  

UK PubMed Central (United Kingdom)

The utility model discloses a fishing rod which belongs to the technical field of the fishing rod and overcomes the defects of the fishing rod without safety and electric shock in the prior art. The fishing rod comprises a fishing line, a fishing main rod, a fishhook and an insulated handle, and is characterized in that the insulated handle is made of non-conductive rubber, the insulated handle is handheld in use, the fishing line and the fishhook on the fishing main rod are placed in water, in case people touch a high voltage wire when pulling the fishing main rod because a fish rise to a bait, the insulated handle plays the insulation and safety function. The utility model has the advantages of simpler structure, lower manufacture cost and stronger practicability.

QINGPING WANG

342

Fish skinner  

UK PubMed Central (United Kingdom)

A fish skinner for removing the skin from a fish filet that includes a cutting block in connection with a pivoting cover plate wherein the cutting block has a recess for receiving the skin of the fish filet and the pivoting cover plate is used to hold the fish filet in place while a filet knife is drawn across the top edge of the cutting block to cut the filet free from the fish skin.

FILIPPINI JOSEPH D

343

FISH SKINNER  

UK PubMed Central (United Kingdom)

A process and apparatus for descaling tuna fish and the like wherein the fish is at least partially cooked and then cooled to a backbone temperature of about 70 DEG to 100 DEG F. The fish is placed on a conveyor and passed through horizontally and vertically disposed brushes. Jets of water are sprayed on the fish at the point of contact of the fish and the brushes to thereby wash away the scales and skin as removed by the brushes.

ORLANDO FRANKLIN P; FRANCO THOMAS

344

Fish skinner  

UK PubMed Central (United Kingdom)

A process and apparatus for skinning fish, particularly tuna fish, which comprises passing a precooked and cooled fish along conveyor belt means and the like while a series of rotating brushes above one side of and adjacent to the belly and back of the fish scrape the skin from those parts of the fish, passing the fish on the conveyor belt to a wheel around which the belt passes while a second belt contacts the opposite side of the fish and also passes around the wheel to hold the fish intact on the wheel until the fish is half way around the wheel and is turned over, depositing the turned over fish onto a third conveyor belt that receives the fish with the unscraped side thereof in the upper position, subjecting the unscraped side of the fish, and optionally, the belly and back thereof, to the rotating brushes to remove substantially all of the skin from the fish, and simultaneously spraying streams of water on the fish passing thereunder and the belts while removing skin from the fish and reducing deposit of the debris therefrom on the abrading apparatus.

ORLANDO FRANKLIN P; FRANCO THOMAAS; PARKER MARK P; THOMPSON ALLEN C

345

Formation of a series of chimney-ladder compounds in the Ru-Re-Si system  

Energy Technology Data Exchange (ETDEWEB)

Rhenium-alloyed ruthenium sesquisilicide alloys have been prepared over the wide composition range Ru{sub 1-{delta}}Re {sub {delta}}Si{sub 1.5}, 0 {<=} {delta} {<=} 0.85. The phase relationships of these alloys have been investigated using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Alloys with {delta} {>=} 0.03 are multi-phase, composed of a series of (Ru,Re)Si {sub y} chimney-ladder phases with compositions of Ru{sub 1-x}Re {sub x}Si{sub 1.5386+0.1783x} (0.14 {<=} x {<=} 0.76) and B20-type monosilicide (Ru,Re)Si as a secondary phase. These chimney-ladder structures are considered to form to stabilize the high-temperature Ru{sub 2}Si{sub 3} chimney-ladder phase through the substitution of Ru with Re. The solubility limit of Re in a series of chimney-ladder phases is as large as 76% Re (x = 0.76) and the Si/(Ru + Re) ratio of the chimney-ladder phases increases with increasing Re content. The observed deviation of the chimney-ladder structure from the idealized composition and the possibility of adjusting the semiconducting properties of these chimney-ladder structures are discussed in terms of the valence electron concentration per metal atom.

Simkin, B.A. [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Ishida, A. [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Okamoto, N.L. [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Kishida, K. [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan)]. E-mail: k.kishida@materials.mbox.media.kyoto-u.ac.jp; Tanaka, K. [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Inui, H. [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan)

2006-06-15

346

Formation of a series of chimney-ladder compounds in the Ru-Re-Si system  

International Nuclear Information System (INIS)

Rhenium-alloyed ruthenium sesquisilicide alloys have been prepared over the wide composition range Ru1-?Re ?Si1.5, 0 ? ? ? 0.85. The phase relationships of these alloys have been investigated using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Alloys with ? ? 0.03 are multi-phase, composed of a series of (Ru,Re)Si y chimney-ladder phases with compositions of Ru1-xRe xSi1.5386+0.1783x (0.14 ? x ? 0.76) and B20-type monosilicide (Ru,Re)Si as a secondary phase. These chimney-ladder structures are considered to form to stabilize the high-temperature Ru2Si3 chimney-ladder phase through the substitution of Ru with Re. The solubility limit of Re in a series of chimney-ladder phases is as large as 76% Re (x = 0.76) and the Si/(Ru + Re) ratio of the chimney-ladder phases increases with increasing Re content. The observed deviation of the chimney-ladder structure from the idealized composition and the possibility of adjusting the semiconducting properties of these chimney-ladder structures are discussed in terms of the valence electron concentration per metal atom.

2006-01-01

347

Heisenberg S=1/2 Spin Ladders: New Molecular-Based Examples  

Science.gov (United States)

Heisenberg spin ladders have a cooperative spin singlet ground state and two critical fields. The ratios of the two fields depend on the ratio of the interaction strengths along the rungs and along the rails of the ladder. Coordination polymers provide examples of spin ladders with exchange strengths small enough to induce critical fields that are less than 60 tesla. To date these molecular-based compounds consist either of lattices of CuBr4 dianions packed into ladders by large organic molecules [1,2] or neutral Cu2X4 dimers (X = Cl, Br) linked into ladders by bridging diazine molecules such as quinoxaline [3]. We present the structures and results of magnetic measurements of three new spin ladders, (quinolinium)2CuBr4, Cu(methylpyrazine)Cl2, and Cu(2,3-dimethylpyrazine)Cl2. The susceptibility of each of the compounds possesses a characteristic rounded maximum near 20 K, with a rapid decrease at lower temperatures. Comparison of the data for Cu(2,3-dimethylpyrazine)Cl2 to a spin ladder model reveals the rung and rail exchange constants to be 29.0 K and 17.2 K, respectively. [1] C. P. Landee et al, Phys. Rev. B 63, R100402 (2001). [2] R D. Willett et al, Inorganic Chemistry 43, 3804-3811 2004). [3] C. P. Landee et al, Polyhedron 22, 2325-2329 (2003).

Landee, Christopher; Shapira, A.

2005-03-01

348

Inelastic neutron scattering from the spin ladder compound (VO)2P2O7  

CERN Document Server

We present results from an inelastic neutron scattering experiment on the candidate Heisenberg spin ladder vanadyl pyrophosphate, (VO)2P2O7. We find evidence for a spin-wave excitation gap of E_{gap} = 3.7\\pm 0.2 meV, at a band minimum near Q=0.8 A^{-1}. This is consistent with expectations for triplet spin waves in (VO)2P2O7 in the spin-ladder model, and is to our knowledge the first confirmation in nature of a Heisenberg antiferromagnetic spin ladder.

Eccleston, R S; Brody, J P; Johnson, J W

1994-01-01

349

Nested Bethe Ansatz for Spin Ladder Model with Open Boundary Conditions  

International Nuclear Information System (INIS)

The nested Bethe ansatz (BA) method is applied to find the eigenvalues and the eigenvectors of the transfer matrix for spin-ladder model with open boundary conditions. Based on the reflection equation, we find the general diagonal solution, which determines the general boundary interaction in the Hamiltonian. We introduce the spin-ladder model with open boundary conditions. By finding the solution K± of the reflection equation which determines the nontrivial boundary terms in the Hamiltonian, we diagonalize the transfer matrix of the spin-ladder model with open boundary conditions in the framework of nested BA.

2005-04-15

350

Fish Mouths  

Science.gov (United States)

This activity (page 2 of the PDF) is a full inquiry investigation into environmental adaptation. Groups of learners will observe fish at a zoo, aquarium, or fish store and categorize which way the mouth of each identified fish faces. Based on observations made while the fish are fed and additional research, conclusions should be developed about how the fish fits into its environment. This activity can be used to teach learners about the importance of writing good notes while making observations. Relates to linked video, DragonflyTV GPS: California Fish.

Twin Cities Public Television, Inc.

2006-01-01

351

Etude de quelques facteurs de sélectivité de passes à anguilles Study of some selectivity factors in eel ladders  

Directory of Open Access Journals (Sweden)

Full Text Available Une étude des facteurs de sélectivité des passes à anguilles a été menée au pied d'un obstacle à la migration anadrome de l'anguille sur la Dordogne. Le dispositif expérimental a permis la capture de 6 276 anguilles en 180,5 heures de fonctionnement. La taille des anguilles évolue entre 120 et 395 mm avec une taille moyenne de 223 mm. Elles sont significativement inférieures à celles des anguilles capturées dans une passe à poissons située à proximité. Ces données semblent traduire la sélectivité des passes à poissons traditionnelles sur les anguilles. Les différentes configurations testées ont permis de caractériser certains facteurs de sélectivité : à pente équivalente, la longueur des animaux en reptation varie avec le substrat, les substrats les plus denses sélectionnent les plus petits individus, mais la sélectivité évolue également avec l'inclinaison des rampes. Les facteurs pente et substrat influencent également l'efficacité. Les pentes les plus faibles entre 15 et 30° devraient donc être préconisées pour les passes à anguilles ; le substrat devrait, quant à lui, être adapté à la distribution des tailles des anguilles en migration. Selectivity factors of eel ladders were studied just below an obstacle to eel anadromous migration in Dordogne river. An experimental device caught 6 276 eels for 180,5 hours. The range size of eels varied from 120 to 395 mm (mean length : 223 mm) which is smaller than range size of eels caught by a neighbouring fish ladder. This result seems to show the selectivity of usual fishways. Various configurations of the experimental device allowed to test some selectivity factors. Slope and substrate factors seem to influence the efficiency. For a given slope, the eel size distribution depends on the substrate, more dense brushes involve a smaller average length of migrants. Selectivity also changes according to gradients. Slight slopes (15-30°) should be recommended for such devices and the substrate should be adapted to size distribution of eels in migration.

LEGAULT A.

2008-01-01

352

Vacuum-assisted ladder closure: an innovative prospect.  

UK PubMed Central (United Kingdom)

Negative pressure wound therapy (NPWT) has gained great recognition for its positive effects on enhancing the complex wound healing process. The aim of this limited presentation was to introduce the vacuum-assisted ladder closure (VALC) method as a novel wound care modality used in conjunction with NPWT that reduces wound closure time in complex wounds. Two patients with complex abdominal wounds were identified for this prospective study from August 2011 through October 2011. As this presentation shows, the use of the VALC method appears to reduce complex wound closure times significantly, as compared with the use of NPWT alone. As a result, there may be decreased risk for potential complications such as infection, disfiguration, scar tissue formation, and needless pain and suffering. Through the positive results represented in this limited presentation, the VALC method of wound care used in complex wounds validates the need for further research.

Miller A

2013-01-01

353

Vacuum-assisted ladder closure: an innovative prospect.  

Science.gov (United States)

Negative pressure wound therapy (NPWT) has gained great recognition for its positive effects on enhancing the complex wound healing process. The aim of this limited presentation was to introduce the vacuum-assisted ladder closure (VALC) method as a novel wound care modality used in conjunction with NPWT that reduces wound closure time in complex wounds. Two patients with complex abdominal wounds were identified for this prospective study from August 2011 through October 2011. As this presentation shows, the use of the VALC method appears to reduce complex wound closure times significantly, as compared with the use of NPWT alone. As a result, there may be decreased risk for potential complications such as infection, disfiguration, scar tissue formation, and needless pain and suffering. Through the positive results represented in this limited presentation, the VALC method of wound care used in complex wounds validates the need for further research. PMID:23446511

Miller, Amy

2013-01-01

354

Optical properties and Raman scattering of vanadium ladder compounds  

CERN Multimedia

We investigate electronic and optical properties of the V-based ladder compounds NaV2O5, the iso-structural CaV2O5, as well as MgV2O5, which differs from NaV2O5 and CaV2O5 in the c axis stacking. We calculate ab initio the A_g phonon modes in these compounds as a basis for the investigation of the electron-phonon and spin-phonon coupling. The phonon modes together with the dielectric tensors as a function of the corresponding ion displacements are the starting point for the calculation of the A_g Raman scattering.

Spitaler, J; Ambrosch-Draxl, C; Evertz, H G

2004-01-01

355

Supersymmetric QCD chiral symmetry breaking in the ladder approximation  

International Nuclear Information System (INIS)

Chiral symmetry breaking in supersymmetric QCD with matter fields in a large Casimir representation is analyzed in detail. The effective action for the fermion and scalar propagators and the corresponding Dyson-Schwinger equations are derived in the ladder approximation. A stability analysis in the non-running limit shows that dynamical mass generation for both matter fermions and scalars is energetically favourable. It is found that chiral symmetry breaking takes place essentially in the same way as in ordinary QCD, and that the critical coupling of supersymmetric QCD is 3/2 times the QCD one. Fermion condensation induces a non-zero scalar mass, thus eliminating the perturbatively flat directions of the scalar potential and stabilizing the broken symmetry phase. The relevance of our results to supersymmetry breaking as well as their generalization beyond the non-running limit (in particular to slowly running theories) are discussed. (orig.).

1991-01-01

356

Properties of localized condensation on a ladder superconducting network  

International Nuclear Information System (INIS)

The properties of the localized condensation on a ladder superconducting network are studied using the theory of de Gennes and Alexander. With the use of the analytic Green's functions obtained in the preceding paper, the phase boundary, wave function, and current vortex structure of the localized condensation are studied exactly for various kinds of impurities. In some cases, the fine structure appears in the phase boundary. The locations of the fine structure depend mainly on the flux in the loop formed by the impurities. In general, two regions are defined and there are two types of the current structures, depending on in which region the localized condensation occurs. For various reasons, it is also found that in some situations that depend on the impurity condition and magnetic field strength the localized condensation cannot occur. The implications of the results of this work for the properties of the localized condensation in a two-dimensional network are discussed.

1989-01-01

357

Formalism for fuzzy automation Petri Nets to Ladder Logic Diagrams  

Directory of Open Access Journals (Sweden)

Full Text Available Process automation has been the default standard for industries since processors are prominently figured in the scheme of production. The significant characteristic of Process automation is clarity in the definition of tasks, sequence of operation and concurrency. Programmable Logic Controllers are a set of this morphing of processors prominently favored in the Process Automation due to its ease of use, ruggedness and low cost. PLC, as it is abbreviated is preferred also because of most important reason - ease of programming. Programming of PLC was started with Ladder Logic Diagrams and in spite of other developed high level languages plays a prominent role even today. This problem however is recognized and programming for DES is suggested via a modified approach called Grafcet. In this paper, a fuzzy formalism is introduced into the modeling system as Fuzzy Automation Petri Nets (FAPN) and formal method for conversion of this FAPN into LLD is suggested.

P. R.Venkateswaran; Jayadev Bhat; S. Meenatchisundaram

2009-01-01

358

Ward Identity Constraints on Ladder Kernels in Transport Coefficient Calculations  

Energy Technology Data Exchange (ETDEWEB)

Using diagrammatic methods, we show how the Ward identity can be used to constrain the ladder kernel in transport coefficients calculations. More specifically, we use the Ward identity to determine the necessary diagrams that must be resummed (using the usual integral equation). Our main result is an equation relating the kernel of the integral equation with functional derivatives of the full (imaginary) self-energy; it is similar to what is obtained with 2PI effective action methods. However, since we use the Ward identity as our starting point, gauge invariance is preserved. Using power counting arguments, we also show which self-energies must be included in the resummation at leading order, including 2 to 2 scatterings and 1 to 2 collinear scatterings with the Landau-Pomeranchuk-Migdal (LPM) effect. In this study we restrict our discussion to electrical conductivity and shear viscosity in QED, but our method can in principles be generalized to other transport coefficients and other theories.

Gagnon, J.-S. [Department of Physics, McGill University, 3600 University Street, Montreal, H3A 2T8 (Canada); Jeon, S. [Department of Physics, McGill University, 3600 University Street, Montreal, H3A 2T8 (Canada)

2007-03-15

359

Quantum phase diagram of an exactly solved mixed spin ladder  

CERN Multimedia

We investigate the quantum phase diagram of the exactly solved mixed spin-(1/2,1) ladder via the thermodynamic Bethe ansatz (TBA). In the absence of a magnetic field the model exhibits three quantum phases associated with su(2), su(4) and su(6) symmetries. In the presence of a strong magnetic field, there is a third and full saturation magnetization plateaux within the strong antiferromagnetic rung coupling regime. Gapless and gapped phases appear in turn as the magnetic field increases. For weak rung coupling, the fractional magnetization plateau vanishs and exhibits new quantum phase transitions. However, in the ferromagnetic coupling regime, the system does not have a third saturation magnetization plat eau. The critical behaviour in the vicinity of the critical points is also derived systematically using the TBA.

Batchelor, M T; Oelkers, N; Ying, Z J

2004-01-01

360

Transport coefficients and ladder summation in hot gauge theories  

International Nuclear Information System (INIS)

We show how to compute transport coefficients in gauge theories by considering the expansion of the Kubo formulas in terms of ladder diagrams in the imaginary time formalism. All summations over Matsubara frequencies are performed and the analytical continuation to get the retarded correlators is done. As an illustration of the procedure, we present a derivation of the transport equation for the shear viscosity in the scalar theory. Assuming the hard thermal loop approximation for the screening of distant collisions of the hard particles in the plasma, we derive two integral equations for the effective vertices which, to logarithmic accuracy, are shown to be identical to the linearized Boltzmann equations previously found by Arnold, Moore, and Yaffe.

2002-08-15

 
 
 
 
361

Modeling of droplet traffic in interconnected microfluidic ladder devices.  

UK PubMed Central (United Kingdom)

The problem of controlling the droplet motion in multiphase flows on the microscale has gained increasing attention because the droplet-based microfluidic devices provide great potentials for chemical and biological applications. It is critical to understand the relevant physics on droplet hydrodynamics and thus control the generation, motion, splitting, and coalescence of droplets in complex microfluidic networks. Numerical simulations using the volume of fluid algorithm are conducted to investigate the time-dependent dynamics of droplets in gas-liquid multiphase devices. An analytical model based on the electronic-hydraulic analogy is developed to describe the hydrodynamic behavior of the droplets in interconnected microfluidic ladder devices. It is found that the pressure drop caused by the droplets plays a critical role in the droplet synchronization. A fitted formula for pressure drops in the presence of surfactant is achieved by using numerical simulations. Both the numerical and the theoretical results agree well with the corresponding experimental results.

Song K; Zhang L; Hu G

2012-02-01

362

Topological phases of the two-leg Kitaev ladder  

Science.gov (United States)

We study the phase diagram of the two-leg Kitaev model. Different topological phases can be characterized by either the number of Majorana modes for a deformed chain of the open ladder, or by a winding number related to the 'h-loop' in the momentum space. By adding a three-spin interaction term to break the time-reversal symmetry, two originally different phases are glued together, so that the number of Majorana modes reduce to 0 or 1, namely, the topological invariant collapses to Z2 from an integer Z. These observations are consistent with a recent general study [S. Tewari, J.D. Sau, arXiv:1111.6592v2].

Wu, Ning

2012-10-01

363

Quantum Walks of SU(2)_k Anyons on a Ladder  

CERN Multimedia

We study the effects of braiding interactions on single anyon dynamics using a quantum walk model on a quasi-1-dimensional ladder filled with stationary anyons. The model includes loss of information of the coin and nonlocal fusion degrees of freedom on every second time step, such that the entanglement between the position states and the exponentially growing auxiliary degrees of freedom is lost. The computational complexity of numerical calculations reduces drastically from the fully coherent anyonic quantum walk model, allowing for relatively long simulations for anyons which are spin-1/2 irreps of SU(2)_k Chern-Simons theory. We find that for Abelian anyons, the walk retains the ballistic spreading velocity just like particles with trivial braiding statistics. For non-Abelian anyons, the numerical results indicate that the spreading velocity is linearly dependent on the number of time steps. By approximating the Kraus generators of the time evolution map by circulant matrices, it is shown that the spatial...

Lehman, L; Brennen, G K

2012-01-01

364

Breathers in Josephson junction ladders: Resonances and electromagnetic wave spectroscopy  

DEFF Research Database (Denmark)

We present a theoretical study of the resonant interaction between dynamical localized states (discrete breathers) and linear electromagnetic excitations (EE's) in Josephson junction ladders. By making use of direct numerical simulations we find that such an interaction manifests itself by resonant steps and various sharp switchings (voltage jumps) in the current-voltage characteristics. Moreover, the power of ac oscillations away from the breather center (the breather tail) displays singularities as the externally applied dc bias decreases. All these features may be mapped to the spectrum of EE's that has been derived analytically and numerically. Using an improved analysis of the breather tail, a spectroscopy of the EE's is developed, The nature of breather instability driven by localized EE's is established.

Miroshnichenko, A. E.; Flach, S.

2001-01-01

365

Upper Critical Fields of Moleular-Based Spin Ladders  

Science.gov (United States)

The upper critical (saturation) fields of several spin ladders was found using a high field, short pulse magnet at LANL. These compounds include Cu(Quinoxaline)Cl2, Cu(Quinoxaline)Br2, Cu(2,3 dimethylpyrazine)Cl2, Cu(2,3 dimethylpyrazine)Br2, Cu(methylpyrazine)Br2, and Cu(methylpyrazine)Cl2. The data were taken at temperatures as low as 460 mK with a pulsed field strength as high as 57 tesla. The upper critical fields were estimated by considerations of overcoming the exchange energies associated with all the compounds. These energies were extracted from model fits to the susceptibility data. These estimations agree reasonably well with the experimentally observed upper critical fields. We report on these results and compare the data to simulations of the magnetization as a function of field as a further check to confirm that these compounds obey the associated model systems.

Keith, Brian; Landee, Chris; Turnbull, Mark; Harrison, Neil

2010-03-01

366

Competing ground states of metal-halide ladders  

CERN Document Server

Based on a symmetry argument, we investigate the ground-state properties of newly synthesized metal-halide ladder compounds (C_8_H_6_N_4_)[Pt(C_2_H_8_N_2_)X]_2_(ClO_4_)_4_ 2H_2_O (X=Cl, Br, I). Employing a fully dressed two-band Peierls-Hubbard model, we systematically reveal possible charge- or spin-ordered states. Numerical phase diagrams demonstrate a variety of competing Peierls and Mott insulators with particular emphasis on the transition between two types of mixed-valent state of Pt^II^ and Pt^IV^ driven by varying interchain hopping integrals and Coulomb interactions.

Funase, K; Funase, Kei-ichi; Yamamoto, Shoji

2006-01-01

367

Performance of Long Ladders for the LHCb Silicon Tracker  

CERN Multimedia

The LHCb Silicon Tracker uses detector ladders with readout strips with an effective length of up to 36,cm. Kapton interconnect cables of up to 54,cm in length are employed in between silicon sensors and front-end readout hybrids. Fast front-end readout electronics with a shaping time of around 25,ns are employed to avoid pile-up of events from consecutive LHC bunch crossings. An extensive measurement program as well as simulations have been carried out to study the expected noise performance of these detectors. Presented at the 14th International Workshop on Vertex Detectors, Chuzenji Lake, Nikko, Japan, November 7-11, 2005 Proceedings submitted for publication in Nucl. Instr. and Meth. A

Agari, M; Blouw, J; Hofmann, W; Knöpfle, K T; Löchner, S; Maciuc, F; Schmelling, M; Smale, N J; Schwingenheuer, B; Voss, H; Pugatch, V; Pylypchenko, Y; Bay, A; Bettler, M O; Carron, B; Fauland, P; Frei, R; Jiménez-Otero, S; Nicolas, L; Perrin, A; Schneider, O; Tran, MT; Van Hunen, J J; Vervink, K; Vollhardt, A; Adeva, B; Esperante-Pereira, D; Lois, C; Pérez-Trigo, E; Pló-Casasus, M; Vázquez, P; Bernhard, R P; Bernet, R; Gassner, J; Köstner, S; Lehner, F; Needham, M; Sakhelashvili, T M; Steiner, S; Steinkamp, O; Straumann, U; Volyanskyy, D; Wenger, A

2005-01-01

368

Quantum Monte Carlo study of the Hubbard ladder  

CERN Multimedia

We present quantum Monte Carlo results for the Hubbard model on a ladder using the re-structuring method which employ eigenstates of two-site system on a rung to construct a complete set. From technical reasons we concentrate on the case in which the hopping along the leg is much less than the hopping on the rung. We observe the ground state of the half-filled system is made of singlet-like states described in this paper and its first excited state contains one triplet rung. When the system is lightly doped states composed of an electron and a hole appear on some rungs. We find very few hole-pairing on the rung upon doping up to the quarter-filled case.

Munehisa, Y

1995-01-01

369

Ward Identity Constraints on Ladder Kernels in Transport Coefficient Calculations  

International Nuclear Information System (INIS)

Using diagrammatic methods, we show how the Ward identity can be used to constrain the ladder kernel in transport coefficients calculations. More specifically, we use the Ward identity to determine the necessary diagrams that must be resummed (using the usual integral equation). Our main result is an equation relating the kernel of the integral equation with functional derivatives of the full (imaginary) self-energy; it is similar to what is obtained with 2PI effective action methods. However, since we use the Ward identity as our starting point, gauge invariance is preserved. Using power counting arguments, we also show which self-energies must be included in the resummation at leading order, including 2 to 2 scatterings and 1 to 2 collinear scatterings with the Landau-Pomeranchuk-Migdal (LPM) effect. In this study we restrict our discussion to electrical conductivity and shear viscosity in QED, but our method can in principles be generalized to other transport coefficients and other theories

2007-03-15

370

Condensation of magnons and spinons in a frustrated ladder  

CERN Multimedia

Motivated by the ever increasing experimental effort devoted to the properties of frustrated quantum magnets in a magnetic field, we present a careful and detailed theoretical analysis of a one-dimensional version of this problem, a frustrated ladder with a magnetization plateau at m=1/2. We show that even for purely isotropic Heisenberg interactions, the magnetization curve exhibits a rather complex behavior that can be fully accounted for in terms of simple elementary excitations. The introduction of anisotropic interactions (e.g., Dzyaloshinskii-Moriya interactions) modifies significantly the picture and reveals an essential difference between integer and fractional plateaux. In particular, anisotropic interactions generically open a gap in the region between the plateaux, but we show that this gap closes upon entering fractional plateaux. All of these conclusions, based on analytical arguments, are supported by extensive Density Matrix Renormalization Group calculations.

Fouet, J B; Clarke, D; Youk, H; Tchernyshyov, O; Fendley, P; Noack, R M

2006-01-01

371

Evaluate effects of hydraulic turbulence on the survival of migratory fish: design and construction of experimental apparatus to study the potential effects of turbulence on fish; TOPICAL  

International Nuclear Information System (INIS)

[en] This report presents the completed design and construction process, and working details, of the test apparatus for the turbulence project. As mentioned in the first progress report, this type of experiment has not been attempted previously. In addition, turbulence data in the tailrace of a power plant are not available for reference. We plan to generate turbulence intensities and scale based on representative flow velocities downstream of draft tubes as well as visual observations of flow conditions in a typical tailrace area. Various combinations of nozzles will be used to generate mixing inside a large tank cavity, referred to herein as the turbulence chamber. The turbulence chamber was made with steel frame and clear acrylic sides and bottom. The clear sides and bottom will facilitate viewing and videotaping from outside. Nozzle velocities and water surface profiles will be accurately monitored with calibrated flow measurement devices to insure repeatability of the hydraulic conditions during biological testing

2001-01-01

372

Evaluate Effects of Hydraulic Turbulence on the Survival of Migratory Fish : Design and Construction of Experimental Apparatus to Study the Potential Effects of Turbulence on Fish.  

Energy Technology Data Exchange (ETDEWEB)

This report presents the completed design and construction process, and working details, of the test apparatus for the turbulence project. As mentioned in the first progress report, this type of experiment has not been attempted previously. In addition, turbulence data in the tailrace of a power plant are not available for reference. We plan to generate turbulence intensities and scale based on representative flow velocities downstream of draft tubes as well as visual observations of flow conditions in a typical tailrace area. Various combinations of nozzles will be used to generate mixing inside a large tank cavity, referred to herein as the turbulence chamber. The turbulence chamber was made with steel frame and clear acrylic sides and bottom. The clear sides and bottom will facilitate viewing and videotaping from outside. Nozzle velocities and water surface profiles will be accurately monitored with calibrated flow measurement devices to insure repeatability of the hydraulic conditions during biological testing.

Odeh, Mufeed

2001-05-01

373

Fishing bait  

UK PubMed Central (United Kingdom)

In a fishing lure in the form of a troll, in particular for fishing swordfish or the like, it is provided, with a view to improved efficiency, that a plurality of very fine plastic fibers are fixed to the lure.

SOLDAN FELIX H; ROWER JOHANN

374

Fish Facts  

Science.gov (United States)

... 1 serving) per week. • Do not eat these fish, which are high in mercury: • Swordfish • Tilefish • King mackerel • Shark • Check before eating fish caught in local waters. State health departments have ...

375

Resonant two-magnon Raman scattering in two-dimensional and ladder-type Mott insulators  

International Nuclear Information System (INIS)

We investigate the resonant two-magnon Raman scattering in the two-dimensional (2D) and ladder-type Mott insulators by using a half-filled Hubbard model in the strong coupling limit. By performing numerical diagonalization calculations for small clusters, we find that the model can reproduce the experimental features in the 2D that the Raman intensity is enhanced when the incoming photon energy is not near the absorption edge but well above it. In the ladder-type Mott insulators, the Raman intensity is found to resonate with absorption spectrum in contrast to the 2D system. The difference between 2D and the ladder systems is explained by taking into account the fact that the ground state in 2D is a spin-ordered state while that in ladder is a spin-gapped one.

2003-01-01

376

Convergence and periodic solutions for the input impedance of a standard ladder network  

Energy Technology Data Exchange (ETDEWEB)

The input impedance of an infinite ladder network is computed by using the recursive relation and by assuming that the input impedance does not change when a new block is added to the network. However, this assumption is not true in general and standard textbooks do not always treat these networks correctly. This paper develops a general solution to obtain the input impedance of a standard ladder network of impedances and admittances for any number of blocks. Then, this result is used to provide the convergence condition for the infinite ladder network. The conditions which lead to periodic input impedance are exploited. It is shown that there are infinite numbers of periodic points and no paradoxical behaviour exists in the standard ladder network.

Ucak, C; Acar, C [Department of Electrical and Electronics Engineering, Yeditepe University, Istanbul (Turkey)

2007-03-15

377

Resonant two-magnon Raman scattering in two-dimensional and ladder-type Mott insulators  

Energy Technology Data Exchange (ETDEWEB)

We investigate the resonant two-magnon Raman scattering in the two-dimensional (2D) and ladder-type Mott insulators by using a half-filled Hubbard model in the strong coupling limit. By performing numerical diagonalization calculations for small clusters, we find that the model can reproduce the experimental features in the 2D that the Raman intensity is enhanced when the incoming photon energy is not near the absorption edge but well above it. In the ladder-type Mott insulators, the Raman intensity is found to resonate with absorption spectrum in contrast to the 2D system. The difference between 2D and the ladder systems is explained by taking into account the fact that the ground state in 2D is a spin-ordered state while that in ladder is a spin-gapped one.

Onodera, Hiroaki; Tohyama, Takami; Maekawa, Sadamichi

2003-10-15

378

Incommensurate nodes in the energy spectrum of weakly coupled antiferromagnetic Heisenberg ladders  

CERN Document Server

Heisenberg ladders are investigated using the bond-mean-field theory [M.Azzouz, Phys. Rev. B 48, 6136 (1993)]. The zero inter-ladder coupling energy gap, the uniform spin susceptibility and the nuclear magnetic resonance spin-relaxation rate are calculated as a function of temperature and magnetic field. For weakly coupled ladders, the energy spectrum vanishes at incommensurate wavevectors giving rise to nodes. As a consequence, the spin susceptibility becomes linear at low temperature. Our results for the single ladder successfully compare to experiments on SrCu_2O_3 and (VO)_2P_2O_7 materials and new predictions concerning the coupling to the magnetic field are made.

Azzouz, M; Benyoussef, A

1997-01-01

379

A Remarkable Formula for Counting Nonintersecting Lattice Paths in a Ladder With Respect to Turns  

UK PubMed Central (United Kingdom)

We prove a formula, conjectured by Conca and Herzog, for the number of allfamilies of nonintersecting lattice paths with certain starting and end points in a region thatis bounded by an upper ladder. Thus we are able to compute explicitly the Hilbert series forcertain one-sided ladder determinantal rings.1. Introduction. Recent work of Abhyankar and Kulkarni [1, 2, 18, 19], Bruns, Conca,Herzog, and Trung [3, 5, 6, 10] showed that the computation of the Hilbert series forladder determinantal rings (see section 3 for the definition) boils down to counting familiesof n nonintersecting lattice paths with a given total number of turns in a certain laddershapedregion. For one-sided ladders, Conca and Herzog [6, last paragraph] conjectured aremarkable formula that reduces the problem to counting the number of all single latticepaths with a given number of turns in the ladder region. We state this conjecture insection 2 (our Theorem 1), and prove it in section 4. The crucial i...

C. Krattenthaler

380

Petri Nets and Ladder Logic for Fully-Automating and Programmable Logic Control of Semi-Automatic Machines and Systems  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: Automating semi-automatic dynamic machines and complex systems, where some functionalities are already automated but the machine doesn?t run fully in automatic mode, represents another challenge to automating dynamic and manual complex systems. This study deals with a special case of this general problem, where the system?s semi-automatic and automatic functionalities run separately in a sequence with either automatic and/or semi-automatic functionality running at any point of time, but not both. Approach: Petri-nets can successfully represent the operations of both the semi-automated and fully-automated functionalities of such dynamic systems. Three roles for the programmable logic controllers were suggested: (a) Ignoring the presence of the semi-automatic part, (b) simulating the semi-automatic part and recognizing discrepancies and(c) simulating the semi-automatic functionalities and supporting it, where the last choice was most costly and most reliable. Results: This study presents a case study for a PVC mixing dynamic process to illustrate the three suggested controller design possibilities, where a Petri net model and related ladder logic program were developed to show these three controller design options. In this respect, the semiautomatic functionality is an intermediate step between the two automated functionalities, within which an important decision should be made to end the previous automatic step and to begin the next automatic step. Conclusion/Recommendations: The automation method that was introduced in this study is applicable to a large number of machines within industrial and mechanical systems that were built using older semi-automatic control systems. Various decision analyses {DA1, DA2, DA3} were shown to produce basic choices for such types of applications. Petri-nets and ladder logic in this respect can successfully represent the operations of both the semi-automated and fully-automated functionalities, where a Petri net model and the consequent ladder logic program, used to program the utilized programmable logic controller, are developed to show three possible controller designs, where the choice between three designs depend on the designers objective of cost, reliability and fault tolerance.

Mahmoud A. Barghash; Osama M. Abuzeid; Anas N. Al-Rabadi; Ahmad M. Jaradat

2011-01-01

 
 
 
 
381

Ladder Dyson-Schwinger calculation of the anomalous ?-3? form factor  

International Nuclear Information System (INIS)

The anomalous processes ??3? and ????? are investigated within the Dyson-Schwinger framework using the rainbow-ladder approximation. Calculations reveal that a complete set of ladder diagrams beyond the impulse approximation are necessary to reproduce the fundamental low-energy theorem for the anomalous form factor. Higher momentum calculations also agree with the limited form factor data and exhibit the same resonance behavior as the phenomenological vector meson dominance model.

2003-08-01

382

Phase diagram of the frustrated spin ladder with the next nearest intrachain couplings  

International Nuclear Information System (INIS)

By the density matrix renormalization group method, the phase diagram of the frustrated spin-1/2 ladder with the next nearest intrachain and ferromagnetic interchain couplings is obtained. According to our results, the two-rung entanglement is shown to be more sensitive than order parameters for determining phase boundary in such a frustrated spin ladder model. Furthermore, the additional next nearest intrachain coupling is found to enhance the intermediate columnar dimerized phase evidently.

2012-06-15

383

Ladder operator formalisms and generally deformed oscillator algebraic structures of quantum states in Fock space  

CERN Multimedia

We show that various kinds of one-photon quantum states studied in the field of quantum optics admit ladder operator formalism and bear generally deformed oscillator algebraic structure. The two-photon case is also considered. We obtain the ladder operator formalisms of two general states defined in the even/odd Fock space. The two-photon states also bear generally deformed oscillator algebraic structure. Some interesting examples of one-photon and two-photon quantum states are given.

Wang, X G

2000-01-01

384

Persistent currents in a Möbius ladder A test of interchain coherence of interacting electrons  

CERN Multimedia

Persistent currents in a Moebius ladder are shown to be very sensitive to the effects of intrachain interactions on the hopping of electrons between chains. Their periodicity as a function of flux is doubled for strong enough repulsive interactions because electrons cannot hop coherently between the chains and have to travel along the full edge of the Moebius ladder, thus encircling the flux twice. Mesoscopic devices that should enable one to observe these effects are proposed.

Mila, F; Capponi, S; Mila, Frederic; Stafford, Charles; Capponi, Sylvain

1998-01-01

385

The Short Call Ladder strategy and its application in trading and hedging  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents a new approach to the formation of Short Call Ladder (SCL) strategy based on the functions of profit. Anoptimal algorithm for the use of this strategy in trading is introduced as well. Furthermore, this paper is focused on the applicationof Short Call Ladder strategy in hedging against a price rise of the underlying asset. In the end, the results are compared with theresults of hedging obtained by Short Combo and Vertical Ratio Call Back Spread option strategy.

Omer Faraj S. Amaitiek; Tomáš Bálint; Marcel Rešovský

2010-01-01

386

Boyer's model of scholarship applied to a career ladder for nontenured nursing faculty.  

UK PubMed Central (United Kingdom)

This article presents a career ladder for the reappointment and promotion of nontenured clinical faculty, based on Boyer's model of the scholarship of teaching, application, discovery, and integration and on his four principles and six standards. Titles, lengths of appointments, criteria, obligations, and professional development are defined for four levels of clinical faculty. Guide questions modeled on Boyer's dimensions of scholarship, principles, and standards that were used to guide the development of the career ladder are included.

Wood SO; Biordi DL; Miller BA; Poncar P; Snelson CM; Banks MJ; Hemminger SA

1998-05-01

387

Boyer's model of scholarship applied to a career ladder for nontenured nursing faculty.  

Science.gov (United States)

This article presents a career ladder for the reappointment and promotion of nontenured clinical faculty, based on Boyer's model of the scholarship of teaching, application, discovery, and integration and on his four principles and six standards. Titles, lengths of appointments, criteria, obligations, and professional development are defined for four levels of clinical faculty. Guide questions modeled on Boyer's dimensions of scholarship, principles, and standards that were used to guide the development of the career ladder are included. PMID:9653213

Wood, S O; Biordi, D L; Miller, B A; Poncar, P; Snelson, C M; Banks, M J; Hemminger, S A

388

Dispersive collective charge modes in a spin 1/2 cuprate ladder  

International Nuclear Information System (INIS)

We present the momentum evolution of collective charge modes in Sr14Cu24O41 over the complete Brillouin zone using inelastic resonant X-ray scattering. The observed spectrum is found to be dispersive with periodicity corresponding to the ladder sublattice for momentum transfers along the ladder 'leg' direction, and nondispersive along the 'rung'. Details of the spectrum, including dispersion and linewidth, fall between characteristic charge spectra of single chain quasi-1D Mott insulators and quasi-2D cuprates.

2008-04-01

389

(?-DT-TTF)2[Au(mnt)2]: a weakly disordered molecular spin-ladder system.  

UK PubMed Central (United Kingdom)

The synthesis and characterization of (?-DT-TTF)2[Au(mnt)2] is reported. The magnetic properties of this new salt show that it is still a rare example of an organic spin-ladder. (?-DT-TTF)2[Au(mnt)2] shares the same ladder structure of the DT-TTF and ETT-TTF analogues, and its room temperature conductivity is ?2 S/cm. Despite the observed donor orientation disorder associated with the thiophenic sulfur atoms, the intermolecular interactions between donor units, calculated using the extended Hückel approximation and a double-? basis set, show that the interaction values do not depend on the configuration of the sulfur atom on the thiophenic ring. The insensitivity of the spin-ladder magnetic properties to the donor molecular disorder in (?-DT-TTF)2[Au(mnt)2] is a direct consequence of the negligible contribution of the disordered thiophenic sulfur atom to the HOMO. In the related donor ETT-TTF, this contribution is significant and destroys the magnetic interactions, and no spin-ladder is observed. This compound not only enlarges the number of organic spin-ladder systems in this series of closely related compounds but also provides an interesting example of weakly disordered molecular spin-ladder system.

Silva RA; Neves AI; Lopes EB; Santos IC; Coutinho JT; Pereira LC; Rovira C; Almeida M; Belo D

2013-05-01

390

New approaches to all carbon ladder polymers: Cyclization reactions of acetylenes  

Energy Technology Data Exchange (ETDEWEB)

All-carbon conjugated ladder polymers promise to exhibit attractive electrical and optical properties. While a few very elegant synthesis of all-carbon ladder polymers (and oligomers) have been reported, it can be said that present synthetic procedures are insufficient to realize the true potential of this important class of material. The limited state of synthetic procedures stems from the inherent insolubility of ladder polymers which precludes standard synthetic methods. This paper reports herein the authors` investigations towards new synthetic routes to all-carbon ladder polymers with novel architectures by cyclization reactions of poly(1,2-denthynyl-phenylenes) and solid state polymerization of macrocyclic diacetylenes. High molecular weight (53,000-170,000) poly(1,2-diethynyl-phenylenes) have been synthesized by palladium catalyzed cross-coupling reactions. It is proposed that these materials may be converted to all-carbon ladder polymers by a zipper version of the Bergman cyclization reaction. A strained macrocylic diacetylene is reported which appears to undergo cyclo-polymerization in the solid state. This reaction also is being investigated as a route to all-carbon ladder polymers.

Zhou, Q.; Swager, T.M. [Univ. of Pennsylvania, Philadelphia, PA (United States)

1993-12-31

391

Fish immunostimulants  

Directory of Open Access Journals (Sweden)

Full Text Available Fish immunostimulants are important substances useful to control infectious fish diseases and aresubstantially beneficial to the aquaculture business and environment.This literature review covers the results of using fish immune modulators, including bacteria and bacterial derivatives, adjuvants, chitin, glucan, vitamin, and other synthetic materials. These immunostimulants enhance the activities of phagocytotic cells, stimulate the immunological cells to create more lysozymes and more antibodies, enhance the complement efficiency in fish and eventually increase the abilities to prevent bacterial infection. These responses are able to prevent fish from succumbing to various infectious diseases.

Chitmanat, C.

2002-01-01

392

Fish Prints  

Science.gov (United States)

In this hands-on art activity, learners will study and identify features of the external anatomy of a fish. They will have the opportunity to learn the different functions of fish anatomy along with new vocabulary terms while handling a real fish in their art project. Also, a discussion may take place about the different kinds of fish and how different shapes are more beneficial for certain environments. As a wrap up, learners can become familiar about issues related to the conservation of fish, such as overfishing, habitat destruction, and invasive species. This activity is standards-based.

Sciences, California A.

2008-01-01

393

FISH SKINNER  

UK PubMed Central (United Kingdom)

A process and apparatus for descaling and skinning tuna fish and the like wherein the fish is at least partially cooked and then cooled to a backbone temperature of about 70 to 100 °F. The fish is placed on a conveyor (c) and passed through horizontally (24, 26) and vertically (22) disposed brushes. Jets of water are sprayed on the fish at the point of contact of the fish and the brushes to thereby wash away the scales and skin as removed by the brushes.

ORLANDO Franklin P.; FRANCO Thomas

394

Fishing lure  

UK PubMed Central (United Kingdom)

A fishing lure for spraying water droplets fore and aft of the fishing lure. The fishing lure has a monolithic fishing lure body extending along an axis from a head end to a tail end of the fishing lure body. A first substantially planar surface is formed at the head end of the fishing lure body such that the first substantially planar surface forms a first angle with respect to the axis. A second substantially planar surface is formed at the head end of the fishing lure body such that the second substantially planar surface forms a second angle with respect to the axis. A third angle is formed with respect to the first and second substantially planar surfaces such that the third angle is the sum of the first angle and the second angle. A crotch is defined by the intersection of the first substantially planar surface and the second substantially planar surface. The crotch extends through and substantially transverse to the axis, wherein the crotch and the axis cooperate to define a plane that defines the fishing lure body into an upper portion and a lower portion adjacent to the first substantially planar surface and the second substantially planar surface, respectively. A hook tie eyelet for pivotally attaching a fishing hook thereto is connected to a central portion of the lower portion of the fishing lure body, and a line tie eyelet is connected to the head end of the fishing lure body.

SAYERS JOE

395

Fishing system  

UK PubMed Central (United Kingdom)

An improved fishing system that records ambient conditions existing at or around the time a fish is caught. The fishing system includes a lure which records ambient conditions, including time, date, depth, temperature, ambient light, an underwater picture of a hooked fish and water quality. After catching a fish, the recorded data is transmitted from the lure to a handheld control unit. The handheld control unit is also capable of recording location (via GPS), fish weight, water quality, and an out-of-water picture of the fish. The data stored by the handheld control unit is transmitted (via a wireless or wired network) and recorded in an Internet database. The lure can also be controlled to release a hook that becomes irretrievably stuck in an underwater obstruction. The path of the lure in the water can also be controlled.

DAVIDSON KENT G

396

Fish tank convenient for weighing  

UK PubMed Central (United Kingdom)

The utility model relates to a fish tank capable of weighing fish conveniently, which solves the problem that the fish can be weighed in time and conveniently. The technical scheme is that a water gauge is added on the fish tank, wherein, the water gauge can be designed in various forms such as a transparent tube, a transparent plate and a scale plate the added water gauge can display and reflect the heightening value of the liquid level after the fish is put in the tank then the weight of the fish can be obtained according to the heightening value of the liquid level. The fish tank has the advantages of simple structure, and convenient, in-time and obvious display.

JIANQING ZHANG

397

An Evaluation of the Selectivity Characteristics of Different Juvenile Fish Escape Panel Designs for the Demersal Trap Fishery of Abu Dhabi, United Arab Emirates  

Directory of Open Access Journals (Sweden)

Full Text Available The selectivity characteristics of 4 juvenile fish escape panel designs and their utility for the regulation of a multi-species demersal trap fishery were evaluated using a suite of objective socio-economic and biological criteria. The panel designs consisted of a control (type A) which had a hexagonal mesh size which was the same as that of the body of the trap (3.5 cm), a rectangular mesh (type B) which was representative of the current regulation (5.0 x 7.6 cm) and 2 escape panels with square meshes of 7.5 x 7.5 cm (type C) and 10.0 x 10.0 cm (type D). The results demonstrated that there was only a limited reduction in the proportion of juvenile fish and by-catch retained for the existing juvenile escape panel design (type B). Furthermore, as the selectivity characteristics for the key species (Epinephelus coioides and Diagramma pictum) were similar to the control type, the predicted increases in yields, revenues and spawning stock biomass were small by comparison. The escape panel with the largest mesh size (type D) retained the least un-utilized and discarded by-catch. Whilst simulations predicted the highest spawner biomass per recruit, long term yields and revenues for the key species, its use was associated with a dramatic short-term decline in revenues which were 23.3% of the value of the control type. Traps fitted with the type C which had a square mesh of 7.5 x 7.5 cm had the lowest juvenile retention and the highest overall score for all the assessment criteria combined. The study provides an empirical basis for gear regulations for the demersal trap fishery of the Emirate of Abu Dhabi and the wider Arabian Gulf region.

Edwin Mark Grandcourt; Thabit Zahran Al Abdessalaam; Stanley Alexander Hartmann; Ahmed Tarish Al Shamsi; Franklin Francis

2011-01-01

398

Magnetic States of the Two-Leg Ladder Iron Selenides  

Science.gov (United States)

Neutron scattering experiments have unveiled a dominant spin arrangement in the two-leg ladder selenide compound BaFe2Se3, involving ferromagnetically ordered 2x2 iron-superblocks, that are antiferromagnetically coupled among them (the ``block-AFM'' state). Our numerical study of the electronic five-orbital Hubbard model, within the Hartree-Fock approximation and using first principles techniques for the hopping amplitudes, has shown that the exotic block-AFM state is indeed stable at realistic electronic densities n ˜6.0. Another state with wavevector (,) becomes stable in other portions of the phase diagrams, including n ˜5.5, as found experimentally in KFe2Se3. In addition, our study unveils several competing magnetic phases that could be experimentally stabilized varying either n chemically or the electronic bandwidth by pressure. Similar results were obtained using two-orbital models, studied here via Lanczos and DMRG techniques [1]. [1] Qinlong Luo, et al, arXiv: 1205.3239, and references therein.

Luo, Qinlong; Nicholson, Andrew; Rincon, Julian; Liang, Shuhua; Moreo, Adriana; Dagotto, Elbio; Riera, Jose; Alvarez, Gonzalo; Wang, Limin; Ku, Wei

2013-03-01

399

A ladder polysilane as a template for folding palladium nanosheets.  

UK PubMed Central (United Kingdom)

Although discrete nano-sized compounds consisting of a monolayer sheet of multiple atoms have attracted much attention, monolayer transition metal nanosheets are difficult to access. Here we report a template synthesis of the folding metal nanosheet (2) consisting of 11 palladium atoms by treatment of a ladder polysilane, decaisopropylbicyclo[2.2.0]hexasilane (1), with Pd(CN(t)Bu)2. Crystallographic analysis reveals that the compound is composed of two monolayer Pd7 sheets sharing three palladium atoms at the junction. Each Pd atom is stabilized by Pd-Si ?-bonds, Pd-Pd bonds and coordination of isocyanides. Ligand exchange of 2 from CN(t)Bu to CN(2,4,6-Me3-C6H2) is accompanied by structural rearrangement, leading to the formation of another folding Pd11 nanosheet (3) consisting of two edge-sharing Pd7 sheets. The shapes of the Pd7 sheets as well as the dihedral angle between the two Pd7 sheets are dependent on the substituent of the isocyanide ligand.

Sunada Y; Haige R; Otsuka K; Kyushin S; Nagashima H

2013-01-01

400

Field-induced incommensurate order in frustrated spin ladder  

Energy Technology Data Exchange (ETDEWEB)

In the magnetization process of the S = 1/2 spin ladder system there are two critical magnetic fields H{sub c1} and H{sub c2}. The spin gap vanishes at H{sub c1} and the magnetization is saturated at H{sub c2}. Usually the commensurate antiferromagnetic spin correlation perpendicular to the external field H is dominant and the canted Neel order would be stabilized by interladder interaction for H{sub c1}{eta}{sup x} to {eta}{sup z}<{eta}{sup x}, where {eta}{sup z} and {eta}{sup x} are the critical exponents of the parallel and perpendicular spin correlation functions, respectively. Some phase diagrams including the {eta}-inversion and the magnetization plateau are presented.

Sakai, Toru [Japan Atomic Energy Agency (JAEA), Spring-8, Hyogo 679-5148 (Japan); Okamoto, Kiyomi [Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551 (Japan)

2007-04-11

 
 
 
 
401

Field-induced incommensurate order in frustrated spin ladder  

International Nuclear Information System (INIS)

In the magnetization process of the S = 1/2 spin ladder system there are two critical magnetic fields Hc1 and Hc2. The spin gap vanishes at Hc1 and the magnetization is saturated at Hc2. Usually the commensurate antiferromagnetic spin correlation perpendicular to the external field H is dominant and the canted Neel order would be stabilized by interladder interaction for Hc1c2. The present theoretical study based on numerical diagonalization indicated the following interesting results. In the presence of the next-nearest-neighbour interaction, the incommensurate spin correlation parallel to H would be possibly stronger than the commensurate one for some intermediate external field. As a result, with interladder interaction, another field-induced transition would occur from the usual canted Neel order to the incommensurate one. The new field-induced transition is based on the so-called ?-inversion, namely a change from ?z>?x to ?zx, where ?z and ?x are the critical exponents of the parallel and perpendicular spin correlation functions, respectively. Some phase diagrams including the ?-inversion and the magnetization plateau are presented.