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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 predaç??o 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

2012-10-01

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Selectivity of fish ladders: a bottleneck in Neotropical fish movement  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 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 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 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, Pse

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

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Fish ladders: safe fish passage or hotspot for predation?  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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. Embo [...] ra 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 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 salmoni [...] ds 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 sugge

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

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 des...

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

2007-01-01

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Passage and behaviour of cultured Lake Sturgeon in a prototype side-baffle fish ladder: I. Ladder hydraulics and fish ascent  

Science.gov (United States)

Research and development of a fish ladder for sturgeons requires understanding ladder hydraulics and sturgeon behaviour in the ladder to insure the ladder is safe and provides effective passage. After years of research and development, we designed and constructed a full-scale prototype side-baffle ladder inside a spiral flume (38.3m long??1m wide??1m high) on a 6% (1:16.5) slope with a 1.92-m rise in elevation (bottom to top) to test use by sturgeons. Twenty-eight triangular side baffles, each extending part way across the flume, alternated from inside wall to outside wall down the ladder creating two major flow habitats: a continuous, sinusoidal flow down the ladder through the vertical openings of side-baffles and an eddy below each side baffle. Ascent and behaviour was observed on 22 cultured Lake Sturgeon=LS (Acipenser fulvescens) repeatedly tested in groups as juveniles (as small as 105.1cm TL, mean) or as adults (mean TL, 118cm) during four periods (fall 2002 and 2003; spring 2003 and 2007). Percent of juveniles entering the ladder that ascended to the top was greater in spring (72.7%) than in fall (40.9-45.5%) and 90.9% of 11 adults, which ascended as juveniles, ascended to the top. Six LS (27.3%) never swam to the top and seven (31.8%) swam to the top in all tests, indicating great variability among individuals for ascent drive. Some LS swam directly to the top in <1min, but most rested in an eddy during ascent. Juveniles swimming through outside wall baffle slots (mean velocity, 1.2ms-1) swam at 1.8-2.2body lengthss-1 and 3.2-3.3tail beatss-1, either at or approaching prolonged swimming speed. The side-baffle ladder was stream-like and provided key factors for a sturgeon ladder: a continuous flow and no full cross-channel walls, abundant eddies for resting, an acceptable water depth, and a water velocity fish could ascend swimming 2bls-1. A side-baffle ladder passes LS and other moderate-swimming fishes. ?? 2011 Blackwell Verlag, Berlin.

Kynard, B.; Pugh, D.; Parker, T.

2011-01-01

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

International Nuclear Information System (INIS)

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 9oC. Similarly, few untagged fish were recorded ascending the ladder by the electronic fish counter at water temperatures below 8.5oC. Records from the fish counter indicated that 92% of upstream movements were made during daylight. (author)

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  

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

2004-08-01

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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 SciELO Brazil | Language: English 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 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. 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 rive [...] r (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.

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

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 L...

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

2007-01-01

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 co...

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

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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 SciELO Brazil | Language: English 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 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. 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 2 [...] 010. 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.

Fernando Mayer, Pelicice; Carlos Sérgio, Agostinho.

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New Concepts in Fish Ladder Design, Volume II of IV, Results of Laboratory and Field Research on New Concepts in Weir and Pool Fishways, 1982-1984 Final Project Report.  

Energy Technology Data Exchange (ETDEWEB)

A comprehensive review of fishway design practice led to new design concepts that had previously been untested. This concept was based on the observation that fish can be stimulated to leap when presented with certain hydraulic conditions. A laboratory test program was conducted to develop this concept into a new fishway configuration. Field testing revealed that components of the new design improved fish passage. Verification of the initial premise that fish can be stimulated to leap needs further study.

Aaserude, Robert G.; Orsborn, John F.

1985-08-01

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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

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 spect...

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

2006-01-01

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

Directory of Open Access Journals (Sweden)

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 movimentos as

Angelo Antônio Agostinho

2007-01-01

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2007-01-01

18

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 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 dispe [...] rsal (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.

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

19

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 fou...

Carlos Bernardo Mascarenhas Alves

2007-01-01

20

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 SciELO Brazil | Language: English 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 tan [...] ques 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 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 a [...] long 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 migra

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

 
 
 
 
21

Design and construction of double-sided silicon ladders for the L3 microvertex detector  

International Nuclear Information System (INIS)

The techniques used in the construction of the double-sided ladders for the L3 Silicon Microvertex Detector (SMD) are presented. The detector consists of two cylindrical layers, each of 12 ladders, with double-sided silicon detectors which provide r-phi and z coordinates measurements. This description includes ladder mechanical design and the assembly. A novel solution to readout the z-coordinates is presented. It optimizes very effectively the removal of heat generated by the readout electronics and minimizes the radiation length in the central region. Some results from the survey of the individual ladders are also discussed. (orig.)

1994-04-21

22

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

2007-01-01

23

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

24

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 SciELO Brazil | Language: English 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 s [...] ão 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. 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 describe [...] d, 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.

Carlos Bernardo Mascarenhas, Alves.

25

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 SciELO Brazil | Language: English 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 1 [...] 996 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. 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, 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.

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

26

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 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 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 connecti [...] on 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

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

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 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 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.

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

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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

2006-06-01

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 inte...

Li, Bo; Zhao, Hai; Song, Chun-he; Li, Hui; Ai, Jun

2009-01-01

30

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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 jan [...] eiro 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 variação sazonal entre dois períodos anuais analisados. Abstract in english 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

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

31

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 sh...

Baigu?n, Claudio R. M.; Nestler, John M.; Priscilla Minotti; Norberto Oldani

2012-01-01

32

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

33

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

2011-05-01

34

The potential for a fish ladder to mitigate against the loss of marine-estuarine-freshwater connectivity in a subtropical coastal lake  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english Increasing water demand in coastal regions has resulted in the construction of weirs and barrages in coastal freshwaters. These form barriers to migrations of estuarine and euryhaline marine fishes and crustaceans. This study assessed the impact of loss of marine-estuarine-freshwater connectivity ca [...] used by a weir at the outlet of Lake Mzingazi, a coastal lake on the subtropical east coast of South Africa. Facultative catadromous estuarine and euryhaline marine fishes were most affected by the weir, which blocked their upstream migration. These fishes were absent in the lake and were prevented from accessing potential nursery habitat. Crustaceans were less affected by the outlet weir. Salinity tolerances of most penaeid prawn species occurring in southern African estuaries prevent penetration into freshwater reaches of connected systems. Movements of palaemonid prawns which either spawn in or have larvae dependant on estuarine water, and the marine spawning brachyuran Varuna litterata, were not completely impeded by the weir. These species have larvae and juveniles that can climb over the weir in its present form. Historically, the lake served as an estuarine nursery and its physico-chemistry and habitats still offer viable and valuable habitat to estuarine species. There is therefore great potential value in installing a fish ladder at the lake outlet that can be used by juvenile fishes and crustaceans. Re-establishing marine-estuarine-freshwater connectivity here will reinstate a natural migration route that has been impeded for over 70 years and partially restore the ecosystem to its original state

SP, Weerts; CF, MacKay; DP, Cyrus.

35

Stennis acquires new ladder truck  

Science.gov (United States)

The Stennis Space Center Fire Department added to its fire-fighting capabilities with acquisition of a new emergency response vehicle, Ladder-1, for use on-site. The E-One HP78 Aerial Truck is a combination aerial ladder and fire suppression unit and is designed with the latest safety technology. Featuring a 78-foot ladder and a pumping capability of 1,500 gallons per minute, the new truck provides firefighters with a tremendous rescue and fire suppression tool, Stennis Fire Chief Clark Smith said.

2009-01-01

36

Detecting Cerebellar Phenotypes with the Erasmus Ladder  

Digital Repository Infrastructure Vision for European Research (DRIVER)

I designed, created and established a new motor behavioural task for mice, the Erasmus Ladder. It is now a quick and reliable behavioural task to determine if (mutant) mice could be a good model for a neurological disease.

Cupido, A.

2009-01-01

37

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in spanish 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 dura [...] nte 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. Abstract in english 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.

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

38

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

2012-10-01

39

Ladder/PLC's  

Science.gov (United States)

This is a webpage with many learning objects on Ladder/PLC's with over 15 lessons in: Basic PLC Software Programming, Relay Ladder Logic, Advanced PLC Software Programming and PLC Hardware/Addressing. Each lesson links to an interactive resource which helps to further illustrate the concepts related.

2012-12-28

40

Climbing the Density Functional Ladder: Non-Empirical Meta-Generalized Gradient Approximation Designed for Molecules and Solids  

CERN Document Server

The electron density, its gradient, and the Kohn-Sham orbital kinetic energy density are the local ingredients of a meta-generalized gradient approximation (meta-GGA). We construct a meta-GGA density functional for the exchange-correlation energy that satisfies exact constraints without empirical parameters. The exchange and correlation terms respect {\\it two} paradigms: one- or two-electron densities and slowly-varying densities, and so describe both molecules and solids with high accuracy, as shown by extensive numerical tests. This functional completes the third rung of ``Jacob's ladder'' of approximations, above the local spin density and GGA rungs.

Tao, J; Staroverov, V N; Scuseria, G E; Tao, Jianmin; Perdew, John P.; Staroverov, Viktor N.; Scuseria, Gustavo E.

2003-01-01

 
 
 
 
41

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

2008-11-01

42

Integrable Stochastic Ladder Models  

CERN Multimedia

A general way to construct ladder models with certain Lie algebraic or quantum Lie algebraic symmetries is presented. These symmetric models give rise to series of integrable systems. It is shown that corresponding to these SU(2) symmetric integrable ladder models there are exactly solvable stationary discrete-time (resp. continuous-time) Markov processes with transition matrices (resp. intensity matrices) having spectra which coincide with the ones of the corresponding integrable models.

Albeverio, Sergio A; Albeverio, Sergio; Fei, Shao-Ming

2001-01-01

43

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

Science.gov (United States)

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 that characterizes the physical conditions and physical stresses to which fish are exposed 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 Sensor Fish was derived and simulated to understand the design implications of instrument selection and placement within the body of the device. The Sensor Fish 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 and weighs about 43 g, similar to the size and density of a yearling salmon smolt. The accuracy of the pressure sensor was determined to be within 0.2 psi. In laboratory acceptance tests, the relative errors of both the linear acceleration and angular velocity measurements were determined to be less than 5%. An exposure is defined as a significant event when the acceleration reaches predefined thresholds. Based on the different characteristic of acceleration and rotation velocities, the exposure event is categorized as either a collision between the Sensor Fish and a solid structure or shear caused by turbulence. Since its development in 2005, the 6DOF Sensor Fish has been deployed successfully at many major dams in the United States.

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

2007-01-01

44

The cosmic distance ladder  

...The cosmic distance ladder Astronomers have identified the most distant quasar yet to be discovered. But how do they know how far away ...measures cryptography The cosmic distance ladder Astronomers have identified the most distant quasar yet to be discovered. But how do they know how ... Robert Gendler At the end of June, astronomers identified a quasar that is now believed to be the earliest and most distant known ...The quasar discovered in June has a redshift of 7.085, dating it to just 0.77 billion years after the big bang,...

45

Bioinspiration from fish for smart material design and function  

International Nuclear Information System (INIS)

Fish are a potentially rich source of inspiration for the design of smart materials. Fish exemplify the use of flexible materials to generate forces during locomotion, and a hallmark of fish functional design is the use of body and fin deformation to power propulsion and maneuvering. As a result of nearly 500 million years of evolutionary experimentation, fish design has a number of interesting features of note to materials engineers. In this paper we first provide a brief general overview of some key features of the mechanical design of fish, and then focus on two key properties of fish: the bilaminar mechanical design of bony fish fin rays that allows active muscular control of curvature, and the role of body flexibility in propulsion. After describing the anatomy of bony fish fin rays, we provide new data on their mechanical properties. Three-point bending tests and measurement of force inputs to and outputs from the fin rays show that these fin rays are effective displacement transducers. Fin rays in different regions of the fin differ considerably in their material properties, and in the curvature produced by displacement of one of the two fin ray halves. The mean modulus for the proximal (basal) region of the fin rays was 1.34 GPa, but this varied from 0.24 to 3.7 GPa for different fin rays. The distal fin region was less stiff, and moduli for the different fin rays measured varied from 0.11 to 0.67 GPa. These data are similar to those for human tendons (modulus around 0.5 GPa). Analysis of propulsion using flexible foils controlled using a robotic flapping device allows investigation of the effect of altering flexural stiffness on swimming speed. Flexible foils with the leading edge moved in a heave show a distinct peak in propulsive performance, while the addition of pitch input produces a broad plateau where the swimming speed is relatively unaffected by the flexural stiffness. Our understanding of the material design of fish and the control of tissue stiffness is still in its infancy, and the development of smart materials to assist in investigating the active control of stiffness and in the construction of robotic fish-like devices is a key challenge for the near future

2011-09-01

46

Bioinspiration from fish for smart material design and function  

Science.gov (United States)

Fish are a potentially rich source of inspiration for the design of smart materials. Fish exemplify the use of flexible materials to generate forces during locomotion, and a hallmark of fish functional design is the use of body and fin deformation to power propulsion and maneuvering. As a result of nearly 500 million years of evolutionary experimentation, fish design has a number of interesting features of note to materials engineers. In this paper we first provide a brief general overview of some key features of the mechanical design of fish, and then focus on two key properties of fish: the bilaminar mechanical design of bony fish fin rays that allows active muscular control of curvature, and the role of body flexibility in propulsion. After describing the anatomy of bony fish fin rays, we provide new data on their mechanical properties. Three-point bending tests and measurement of force inputs to and outputs from the fin rays show that these fin rays are effective displacement transducers. Fin rays in different regions of the fin differ considerably in their material properties, and in the curvature produced by displacement of one of the two fin ray halves. The mean modulus for the proximal (basal) region of the fin rays was 1.34 GPa, but this varied from 0.24 to 3.7 GPa for different fin rays. The distal fin region was less stiff, and moduli for the different fin rays measured varied from 0.11 to 0.67 GPa. These data are similar to those for human tendons (modulus around 0.5 GPa). Analysis of propulsion using flexible foils controlled using a robotic flapping device allows investigation of the effect of altering flexural stiffness on swimming speed. Flexible foils with the leading edge moved in a heave show a distinct peak in propulsive performance, while the addition of pitch input produces a broad plateau where the swimming speed is relatively unaffected by the flexural stiffness. Our understanding of the material design of fish and the control of tissue stiffness is still in its infancy, and the development of smart materials to assist in investigating the active control of stiffness and in the construction of robotic fish-like devices is a key challenge for the near future.

Lauder, G. V.; Madden, P. G. A.; Tangorra, J. L.; Anderson, E.; Baker, T. V.

2011-09-01

47

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.

48

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 (6DOFSensor 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.

Marshall C. Richmond

2007-11-01

49

Trion ladder diagrams  

CERN Document Server

We first derive a new ``commutation technique'' for an exciton interacting with electrons, inspired from the one we recently developed for excitons interacting with excitons. These techniques allow to take \\emph{exactly} into account the possible exchanges between carriers. We use it to get the $\\mathrm{X}^-$ trion creation operator in terms of exciton and free-electron creation operators. In a last part we generate the ladder diagrams associated to these trions. Although similar to the exciton ladder diagrams, with the hole replaced by an exciton, they are actually much more tricky : (i) Due to the composite nature of the exciton, one cannot identify an exciton-electron potential similar to the Coulomb potential between electron and hole ; (ii) the spins are unimportant for excitons while they are crucial for trions, singlet and triplet states having different energies.

Combescot, M

2002-01-01

50

FPGA Implementations of Ladder Diagrams  

Directory of Open Access Journals (Sweden)

Full Text Available The performance of programmable logic controllers is often constrained by the microprocessor and the real-time firmware of the controller. Field programmable gate arrays (FPGAs are an attractive potential implementation medium for high-speed control because of their fast and parallel execution and programmable nature. Ladder Diagrams are a standard graphical programming method for industrial controllers, but compilers from Ladder Diagrams to FPGA hardware do not yet exist. This paper explores the comparative speed of four different classes of FGPA implementation of Ladder Diagrams - Interpreted Software, Compiled Software, Interpreted Hardware and Compiled Hardware. It also explores parallel versus serial execution of Ladder Diagrams in hardware, and identifies timers as a major resource user in parallel implementations. Overall, a Shared Timer Serial Compiled Hardware system for FPGA implementation of Ladder Diagrams is recommended. Using comparable FPGA resources to other alternatives it provides a 20-600 times speed improvement over other solutions whilst maintaining correct Ladder Diagram semantics.

Neil William Bergmann

2013-02-01

51

Snakes and Ladders  

Science.gov (United States)

This interactive Flash applet simulates a traditional board game and helps children develop early number skills, such as subitizing and counting on, and familiarity with the sequence of numbers 1 to 100. It can be played alone or with another player. Players roll a virtual die and advance on a 100 grid, beginning at lower left and winding through rows that alternate direction. A ladder allows a player to skip ahead, while a snake sends the player backward. The first player to land exactly on 100 is the winner.

2011-01-18

52

Design and construction of an Electric Fish Finder  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Nós fornecemos o esquema e as instruções para a construção de um Detector de Peixes Elétricos - um amplificador portátil de banda larga utilizado para detectar os campos elétricos de peixes gymnotiformes. Este aparelho pode ser adaptado para encontrar peixes elétricos em diversos ambientes aquáticos [...] . É resistente, à prova d'água e energizado por baterias alcalinas. Esta contribuição faz parte de uma série de artigos técnicos que pretende encorajar estudantes de ictiologia neotropical a explorar a ecologia, sistemática e comunicação elétrica de peixes gymnotiformes. Abstract in english We provide notes on the design and construction of an Electric Fish Finder - a portable differential amplifier for detecting the electrostatic fields of gymnotiform knifefishes. The device can be adapted to locate electric fishes in any kind of aquatic environment. It is rugged, water resistant, and [...] powered by alkaline batteries. This contribution is part of a series of technical papers designed to encourage students of neotropical ichthyology to explore the ecology, systematics, and electric signaling of gymnotiform fishes.

William G. R., Crampton; Jonathan K., Wells; Charles, Smyth; Steven A., Walz.

53

Design and construction of an Electric Fish Finder  

Directory of Open Access Journals (Sweden)

Full Text Available We provide notes on the design and construction of an Electric Fish Finder - a portable differential amplifier for detecting the electrostatic fields of gymnotiform knifefishes. The device can be adapted to locate electric fishes in any kind of aquatic environment. It is rugged, water resistant, and powered by alkaline batteries. This contribution is part of a series of technical papers designed to encourage students of neotropical ichthyology to explore the ecology, systematics, and electric signaling of gymnotiform fishes.Nós fornecemos o esquema e as instruções para a construção de um Detector de Peixes Elétricos - um amplificador portátil de banda larga utilizado para detectar os campos elétricos de peixes gymnotiformes. Este aparelho pode ser adaptado para encontrar peixes elétricos em diversos ambientes aquáticos. É resistente, à prova d'água e energizado por baterias alcalinas. Esta contribuição faz parte de uma série de artigos técnicos que pretende encorajar estudantes de ictiologia neotropical a explorar a ecologia, sistemática e comunicação elétrica de peixes gymnotiformes.

William G. R. Crampton

2007-09-01

54

Microfluidic serial dilution ladder.  

Science.gov (United States)

Serial dilution is a fundamental procedure that is common to a large number of laboratory protocols. Automation of serial dilution is thus a valuable component for lab-on-a-chip systems. While a handful of different microfluidic strategies for serial dilution have been reported, approaches based on continuous flow mixing inherently consume larger amounts of sample volume and chip real estate. We employ valve-driven circulatory mixing to address these issues and also introduce a novel device structure to store each stage of the dilution process. The dilution strategy is based on sequentially mixing the rungs of a ladder structure. We demonstrate a 7-stage series of 1?:?1 dilutions with R(2) equal to 0.995 in an active device area of 1 cm(2). PMID:24231765

Ahrar, Siavash; Hwang, Michelle; Duncan, Philip N; Hui, Elliot E

2014-01-01

55

Superconducting ladders take breather  

International Nuclear Information System (INIS)

One of the more unusual phenomena predicted to occur in nonlinear media is the breather - a state in which energy is strongly localized in one place and does not diffuse to other regions of the system. Now experimental groups at the Massachusetts Institute of Technology and the University of Zaragoza in Spain (E Trias et al. Phys. Rev. Lett. 84 741) and at the University of Erlangen and the Max Planck Institute in Dresden (P Binder et al. Phys. Rev. Lett. 84 745) have observed a particular type of breather - known as a rotating discrete breather in a ''ladder'' of superconducting junctions. In this article the author presents the latest experimental research into nonlinear media. (UK)

2000-04-01

56

Can Fish Morphological Characteristics be Used to Re-design Hydroelectric Turbines?  

Energy Technology Data Exchange (ETDEWEB)

Safe fish passage affects not only migratory species, but also populations of resident fish by altering biomass, biodiversity, and gene flow. Consequently, it is important to estimate turbine passage survival of a wide range of susceptible fish. Although fish-friendly turbines show promise for reducing turbine passage mortality, experimental data on their beneficial effects are limited to only a few species, mainly salmon and trout. For thousands of untested species and sizes of fish, the particular causes of turbine passage mortality and the benefits of fish-friendly turbine designs remain unknown. It is not feasible to measure the turbine-passage survival of every species of fish in every hydroelectric turbine design. We are attempting to predict fish mortality based on an improved understanding of turbine-passage stresses (pressure, shear stress, turbulence, strike) and information about the morphological, behavioral, and physiological characteristics of different fish taxa that make them susceptible to the stresses. Computational fluid dynamics and blade strike models of the turbine environment are re-examined in light of laboratory and field studies of fish passage effects. Comparisons of model-predicted stresses to measured injuries and mortalities will help identify fish survival thresholds and the aspects of turbines that are most in need of re-design. The coupled model and fish morphology evaluations will enable us to make predictions of turbine-passage survival among untested fish species, for both conventional and advanced turbines, and to guide the design of hydroelectric turbines to improve fish passage survival.

Cada, G. F.; Richmond, Marshall C.

2011-07-19

57

Integral representations combining ladders and crossed-ladders  

CERN Document Server

We use the worldline formalism to derive integral representations for three classes of amplitudes in scalar field theory: (i) the scalar propagator exchanging N momenta with a scalar background field (ii) the "half-ladder" with N rungs in x - space (iii) the four-point ladder with N rungs in x - space as well as in (off-shell) momentum space. In each case we give a compact expression combining the N! Feynman diagrams contributing to the amplitude. As our main application, we reconsider the well-known case of two massive scalars interacting through the exchange of a massless scalar. Applying asymptotic estimates and a saddle-point approximation to the N-rung ladder plus crossed ladder diagrams, we derive a semi-analytic approximation formula for the lowest bound state mass in this model.

Bastianelli, F; Schubert, C; Thakur, R; Weber, A

2014-01-01

58

FPGA Implementations of Ladder Diagrams  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The performance of programmable logic controllers is often constrained by the microprocessor and the real-time firmware of the controller. Field programmable gate arrays (FPGAs) are an attractive potential implementation medium for high-speed control because of their fast and parallel execution and programmable nature. Ladder Diagrams are a standard graphical programming method for industrial controllers, but compilers from Ladder Diagrams to FPGA hardware do not yet exist. This pape...

2013-01-01

59

Spin ladders with nonmagnetic impurities  

CERN Document Server

We investigate antiferromagnetic spin ladders with nonmagnetic impurities by variational and numerical (Lanczos and DMRG) methods. The interaction between the two unpaired spins opposite to the impurities is described by an effective exchange interaction $J_{eff}$, the magnitude of which depends on the impurity distance. The magnitude of $J_{eff}$ is different for unpaired spins at the edges of an open ladder and in the bulk. This difference is related to the different distribution of the unpaired spin into the bulk of the ladder. The numerical results are interpreted using matrix product states. Using the DMRG we calculate the spectrum of low-lying energy levels for up to 6 impurities and find that these spectra can be reproduced assuming pair interactions with an accuracy of better than 10\\%. We discuss the filling of the ladder gap with impurity states and argue that in the thermodynamic limit the spin ladder with a finite concentration of impurities always shows a Curie susceptibility at low temperatures.

Mikeska, H J; Schollwöck, U

1996-01-01

60

Hubbard ladders in a magnetic field  

CERN Document Server

The behavior of a two leg Hubbard ladder in the presence of a magnetic field is studied by means of Abelian bosonization. We predict the appearance of a new (doping dependent) plateau in the magnetization curve of a doped 2-leg spin ladder in a wide range of couplings. We also discuss the extension to N-leg Hubbard ladders.

Cabra, D C; Pujol, P; Simon, P

2000-01-01

 
 
 
 
61

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

2008-03-01

62

Laddering em pesquisa de marketing / Laddering in marketing research  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese 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 aborda [...] do 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. 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 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.

63

The nonforward QCD ladder diagrams  

International Nuclear Information System (INIS)

We extend the standard analysis of the QCD planar ladder diagrams to the nonforward direction. Results are used for calculating exclusive and semiinclusive cross sections of diffractive photoproduction in the small-x region of ep-collisions. As an example we estimate the event rate for diffractive photoproduction of the neutral vector boson at Hera energies. (orig.)

1981-01-01

64

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Sanz, Crickette; Call, Josep; Morgan, David

2009-01-01

65

Mathematical model for definition of main design characteristics of average fishing trawlers  

Directory of Open Access Journals (Sweden)

Full Text Available The mathematical model is developed to define basic design characteris-tics of average fishing trawlers, allowing to increase their economic efficiency and to ensure the set parameters of vibration habitability. The model considers organization conditions of a fishing trade and results of statistical research for the ships of this type.

Lyong Hung Ngoc

2009-10-01

66

The t-Jz ladder  

CERN Document Server

The phase diagram of the two-leg t-Jz ladder is explored, using the density matrix renormalization group method. Results are obtained for energy gaps, electron density profiles and correlation functions for the half-filled and quarter-filled cases. The effective Lagrangian velocity parameter is shown to vanish at half-filling. The behaviour of the one-hole gap in the Nagaoka limit is investigated, and found to disagree with theoretical predictions. A tentative phase diagram is presented, which is quite similar to the full t-J ladder, but scaled up by a factor of about two in coupling. Near half-filling a Luther-Emery phase is found, which may be expected to show superconducting correlations, while near quarter-filling the system appears to be in a Tomonaga-Luttinger phase.

Weisse, A; Hamer, C J; Weihong, Z; Weihong, Zheng

2005-01-01

67

Six-Degree-of-Freedom Sensor Fish Design: Governing Equations and Motion Modeling  

Energy Technology Data Exchange (ETDEWEB)

The Sensor Fish device is being used at Northwest hydropower projects to better understand the conditions fish experience during passage through hydroturbines and other dam bypass alternatives. Since its initial development in 1997, the Sensor Fish has undergone numerous design changes to improve its function and extend the range of its use. The most recent Sensor Fish design, the three degree of freedom (3DOF) device, has been used successfully to characterize the environment fish experience when passing through turbines, in spill, or in engineered fish bypass facilities at dams. Pacific Northwest National Laboratory (PNNL) is in the process of redesigning the current 3DOF Sensor Fish device package to improve its field performance. Rate gyros will be added to the new six degree of freedom (6DOF) device so that it will be possible to observe the six linear and angular accelerations of the Sensor Fish as it passes the dam. Before the 6DOF Sensor Fish device can be developed and deployed, governing equations of motion must be developed in order to understand the design implications of instrument selection and placement within the body of the device. In this report, we describe a fairly general formulation for the coordinate systems, equations of motion, force and moment relationships necessary to simulate the 6DOF movement of an underwater body. Some simplifications are made by considering the Sensor Fish device to be a rigid, axisymmetric body. The equations of motion are written in the body-fixed frame of reference. Transformations between the body-fixed and interial reference frames are performed using a formulation based on quaternions. Force and moment relationships specific to the Sensor Fish body are currently not available. However, examples of the trajectory simulations using the 6DOF equations are presented using existing low and high-Reynolds number force and moment correlations. Animation files for the test cases are provided in an attached CD. The next phase of the work will focus on the refinement and application of the 6DOF simulator developed in this project. Experimental and computational studies are planned to develop a set of force and moment relationships that are specific to the Sensor Fish body over the range of Reynolds numbers that it experiences. Lab testing of prototype 6DOF Sensor Fish will also allow for refinement of the trajectory simulations through comparison with observations in test flumes. The 6DOF simulator will also be an essential component in tools to analyze field data measured using the next generation Sensor Fish. The 6DOF simulator will be embedded in a moving-machinery computational fluid dynamics (CFD) model for hydroturbines to numerically simulate the 6DOF Sensor Fish.

Deng, Zhiqun; Richmond, Marshall C.; Simmons, Carver S.; Carlson, Thomas J.

2004-08-19

68

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

69

Impact of Small Hydro-Power Plants on Salmonid Fishes Spawning Migrations Maž?j? hidroelektrini? ?taka lašišini? žuv? neršto migracijai  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In 2000 and 2005, fish ladders were built in Vilnia and Siesartis rivers providing fish access to another 10 and 25 km of the rivers respectively. The analysis of redd distribution and abundance in both rivers revealed that the construction of fish ladders significantly increased the number and share of redds above dams, however, a significant increase in redds above the dam occurred 2-4 years after fish ladders construction supporting homing behaviour as one of the most important fa...

Saulius Stak?nas; K?stutis Skrupskelis

2011-01-01

70

Walk-to-ladder Climb Transfer with Force Adjustment for a Multi-locomotion Robot  

Directory of Open Access Journals (Sweden)

Full Text Available This study presents a walk-to-ladder climb transfer for a Multi-locomotion Robot (MLR with force adjustment using a key joint method which has been developed originally for releasing the additional internal stress by changing a redundant position control joint to force control. Walk-to-ladder climb transfer is a multi-contact complicate robot motion with robot hands and feet cooperation. Three sub-motions were designed in this motion transfer: (1 Raise hands to catch the ladder’s rung, (2 Walk close to the ladder, (3 Climb on the ladder with legs. In order to compensate the position errors which always happened with position control, the key joint method has been studied in this study to improve the contact situations between the robot hand and the supporting rung. Experimental results show that this control method is effective for compensating the distance errors between hands and feet, thus the sliding of robot foot and the tumble problems has been prevented successfully. As a result, the MLR performs the walk-to-ladder climb transfer stably and smoothly.

Zhiguo Lu

2013-01-01

71

Exactly soluble isotropic spin-½ ladder models  

Science.gov (United States)

The undeformed limit of the dilute two-colour braid-monoid algebra gives a natural basis for the description of spin-½ ladder models, and allows different Baxterization ansätze. Based on this observation we find the complete classification of exactly soluble generalized isotropic spin-½ ladder models.

Gritsev, V.; Baeriswyl, D.

2003-12-01

72

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.1-4 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 walls. This is also how the situation is presented in most textbooks. One may get the impression that the friction between a ladder and a wall is always negligible, or that dealing with it is so difficult that it should be left out of the realm of introductory physics. The truth of the matter is that the magnitude of the friction coefficient between a ladder and a wall is not much different from that with the floor, and that friction with the wall is an important part of the conditions for having a static ladder. This paper derives a simple relationship between the friction coefficients of the ladder with the floor (?1) and with the wall (?2), when the ladder is in static equilibrium. Figure 1 shows the forces that act on a ladder that leans on a wall.

Salu, Yehuda

2011-05-01

73

Discrete Breathers in Josephson Ladders  

CERN Document Server

We present a study of nonlinear localized excitations called discrete breathers in a superconducting array. These localized solutions were recently observed in Josephson-junction ladder arrays by two different experimental groups. We review the experiments made by Trias et al. We report the detection of different single-site and multi-site breather states and study the dynamics when changing the array bias current. By changing the temperature we can control the value of the damping (the Stewart-McCumber parameter) in the array, thus allowing an experimental study at different array parameters. We propose a simple DC circuit model to understand most of the features of the detected states. We have also compared this model and the experiments with simulations of the dynamics of the array. We show that the study of the resonances in the ladder and the use of harmonic balance techniques allow for understanding of most of the numerical results. We have computed existence diagrams of breather solutions in our arrays...

Trias, E; Brinkman, A C; Orlando, T P

2001-01-01

74

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

2012-05-01

75

Exact solution for a quantum compass ladder  

Science.gov (United States)

We present a spin ladder with antiferromagnetic Ising ZZ interactions along the legs and interactions on the rungs which interpolate between the Ising ladder and the quantum compass ladder. We show that the entire energy spectrum of the ladder may be determined exactly for finite number of spins 2N by mapping to the quantum Ising chain and using Jordan-Wigner transformation in invariant subspaces. We also demonstrate that subspaces with spin defects lead to excited states using finite-size scaling, and the ground state corresponds to the quantum Ising model without defects. At the quantum phase transition to maximally frustrated interactions of the compass ladder, the ZZ spin-correlation function on the rungs collapses to zero and the ground-state degeneracy increases by two. We formulate a systematic method to calculate the partition function for a mesoscopic system and employ it to demonstrate that fragmentation of the compass ladder by kink defects increases with increasing temperature. The obtained heat capacity of a large compass ladder consisting of 2N=104 spins reveals two relevant energy scales and has a broad maximum due to dense energy spectrum. The present exact results elucidate the nature of the quantum phase transition from ordered to disordered ground state found in the compass model in two dimensions.

Brzezicki, Wojciech; Ole?, Andrzej M.

2009-07-01

76

Integrable impurity spin ladder systems  

International Nuclear Information System (INIS)

Two different types of integrable impurities in a spin ladder system are proposed. The impurities are introduced in such a way that the integrability of the models is not violated. The models are solved exactly with the Bethe ansatz equations as well as the energy eigenvalues obtained. We show for both models that a phase transition between gapped and gapless spin excitations occurs at a critical value of the rung coupling J. In addition, the dependence of the impurities on this phase transition is determined explicitly. In one of the models the spin gap decreases by increasing the impurity strength ?. Moreover, for a fixed ?, a reduction in the spin gap by increasing the impurity concentration is also observed

2003-01-17

77

Incorporation of recreational fishing effort into design of marine protected areas.  

Science.gov (United States)

Theoretical models of marine protected areas (MPAs) that explore benefits to fisheries or biodiversity conservation often assume a dynamic pool of fishing effort. For instance, effort is homogenously distributed over areas from which subsets of reserves are chosen. I tested this and other model assumptions with a case study of the multiple-use Jervis Bay Marine Park. Prior to zoning of the park I conducted 166 surveys of the park's recreational fisheries, plotting the location of 16,009 anglers. I converted these plots into diagrams of fishing effort and analyzed correlates between fishing and habitat and the effect of two reserve designs-the draft and final zoning plans of the park-on the 15 fisheries observed. Fisheries were strongly correlated with particular habitats and had negatively skewed and often bimodal spatial distribution. The second mode of intensely fished habitat could be 6 SD greater than the fishery's mean allocation of effort by area. In the draft-zoning plan, sanctuary zone (no-take) area and potential subduction of fishing effort were similar. In the final plan, which was altered in response to public comment, the area of sanctuary zone increased, and the impact on fishing effort decreased. In only one case was a fishery's most intensely targeted location closed to fishing. Because of the discriminating manner with which fishers target habitats, if simple percentage targets are used for planning, sanctuary location can be adjusted to avoid existing fishing effort. According to modeled outcomes, the implication of this may be diminished reserve effectiveness. To address this, reserve area should be implicitly linked to subducted fishing effort when promoting or modeling MPAs. PMID:17002764

Lynch, Tim P

2006-10-01

78

A Laplace ladder of discrete Laplace equations  

CERN Document Server

The notion of a Laplace ladder for a discrete analogue of the Laplace equation is presented. The adjoint of the discrete Moutard equation and a discrete counterpart of the nonlinear form of Goursat equation are introduced.

Nieszporski, M

2002-01-01

79

Ladder operators for the associated Laguerre functions  

Energy Technology Data Exchange (ETDEWEB)

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.

Fakhri, H [Institute for Studies in Theoretical Physics and Mathematics (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of); Chenaghlou, A [Institute for Studies in Theoretical Physics and Mathematics (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of)

2004-07-30

80

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

2004-07-30

 
 
 
 
81

Hood River and Pelton Ladder Evaluation Studies : Annual Report 1994.  

Energy Technology Data Exchange (ETDEWEB)

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 Hatchery Production Program (HRPP). The HRPP will be phased in over several years and will be jointly implemented by the Oregon Department of Fish and Wildlife (ODFW) and the Confederated Tribes of the Warm Springs (CTWS) Reservation. In December 1991, a monitoring and evaluation program was implemented in the Hood River subbasin to collect life history and production information on stocks of anadromous salmonids returning to the Hood River subbasin. The program was implemented to provide the baseline information needed to: (1) evaluate various management options for implementing the HRPP and (2) determine any post-project impacts the HRPP has on indigenous populations of resident fish. Information collected during the 1992-94 fiscal years will also be used to prepare an environmental impact statement (EIS) evaluating the program`s impact on the human environment. To begin construction on project facilities, it was proposed that the HRPP be implemented in two phases. Phase I would include work that would fall under a {open_quotes}categorical exclusion{close_quotes} from NEPA, and Phase II would include work requiring an EIS prior to implementation. This report summarizes the life history and escapement data collected in the Hood River subbasin and the status work of implemented under Phase I of the HR Life history and escapement data will be used to: (1) test the assumptions on which harvest and escapement goals for the Hood River and Pelton ladder master plans are based and (2) develop biologically based management recommendations for implementing the HRPP.

Olsen, Erik A.; French, Rod A.; Ritchey, Alan D.

1995-09-01

82

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

Energy Technology Data Exchange (ETDEWEB)

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.

Lauritzen, D V; Jordan, L K; Gordon, M S [Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095-1606 (United States); Hertel, F S, E-mail: dlauritz@ccsf.ed, E-mail: fritz.hertel@csun.ed, E-mail: msgordon@ucla.ed, E-mail: ljordan@ucla.ed [Department of Biology, California State University-Northridge, Northridge, CA 91330 (United States)

2010-09-15

83

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

International Nuclear Information System (INIS)

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.

2010-09-01

84

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

Science.gov (United States)

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. PMID:20729570

Lauritzen, D V; Hertel, F S; Jordan, L K; Gordon, M S

2010-09-01

85

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

86

Fish passes  

…data showed that the fish pass was working satisfactorily then final approval was given. In 1995 the responsibility for the approval of fish pass designs was passed to the Environment Agency from the Ministry of Agriculture Fisheries and Food. Designs for prospective fish passes are submitted via the local…

87

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

88

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

89

Dipoles on a Two-leg Ladder  

DEFF Research Database (Denmark)

We study polar molecules with long-range dipole-dipole interactions confined to move on a two-leg ladder for different orientations of the molecular dipole moments with respect to the ladder. Matrix product states are employed to calculate the many-body ground state of the system as function of lattice filling fractions, perpendicular hopping between the legs, and dipole interaction strength. We show that the system exhibits zig-zag ordering when the dipolar interactions are predominantly repulsive. As a function of dipole moment orientation with respect to the ladder, we find that there is a critical angle at which ordering disappears. This angle is slightly larger than the angle at which the dipoles are non-interacting along a single leg. This behavior should be observable using current experimental techniques.

Gammelmark, Søren; Zinner, Nikolaj Thomas

2013-01-01

90

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

2009-10-01

91

16 CFR 1207.5 - Design.  

Science.gov (United States)

... 2010-01-01 false Design. 1207.5 Section 1207...POOL SLIDES § 1207.5 Design. (a) Strength...structure in a tamper-proof fashion. (c) Ladders, steps...of the ladder. When tread design ladders are used, the...

2010-01-01

92

An Evaluation of the Utah Career Ladder System.  

Science.gov (United States)

The Utah Career Ladder System was evaluated, in an effort to provide policy options for Phase II of the Career Ladder implementation in Utah and present policy recommendations. Five major data collection efforts were made: (1) analysis of district career ladder plans from 1985-86 through 1987-88; (2) a telephone survey of Utah's 40 superintendents…

Amsler, Mary; And Others

93

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

2011-01-01

94

A portable bio-amplifier for electric fish research: design and construction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The weak electric organ discharges (EODs) of gymnotiform knife fishes can be readily amplified with a wideband amplifier connected to submerged electrodes. The output from such an amplifier can then be monitored with audio speakers or digitized for subsequent analysis. Commercially available devices are expensive and usually require mains electrical power. Here we provide design notes and instructions for the construction and calibration of a cheap, portable, battery-powered, AC-coupled wideb...

Wells, Jonathan K.; Crampton, William G. R.

2006-01-01

95

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 da...

Marlene Sofia Arcifa; André Luiz Henríques Esguícero

2012-01-01

96

Fish passes  

…construction process. Some submitted fish pass designs are unlikely to work satisfactorily because of incorrect depths of water or because of insufficient attention to siting of the structure. The fish pass group provides an opportunity to avoid these costly errors and to promote the use of best practice in fish

97

Development of Single- and Double-sided Ladders for the ILD Vertex Detectors  

CERN Document Server

We discuss two projects exploring the integration of thin CMOS pixel sensors in order to prototype ladders matching the geometry needed for the ILD vertex detector. The PLUME project has designed and fabricated full-size and fully functional double- sided layers which currently reach 0.6 % X0 and aim for 0.3 % X0 in mid-2012. Another approach, SERNWIETE, consists in wrapping the sensors in a polyimide-based micro-cable to obtain a supportless single-sided ladder with a material budget around 0.15 % X0. First promising samples have been produced and the full-size prototype is expected in spring 2012.

Baudot, Jerome; Chon-Sen, Nathalie; Dulinski, Wojciech; Hegner, Franziska; Gelin-Galibel, Marie; Gauld, Rhorry; Goffe, Mathieu; Goldstein, Joel; Gregor, Ingrid; Hu-Guo, Christine; Koetz, Ulrich; Nomerotski, Andrei; Winter, Marc

2012-01-01

98

Rope ladder routing: position-based multipath routing for wireless mesh networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we present a novel multipath structure called rope-ladder which combines the advantages of path, node and link protection schemes. We also propose a position-based multipath routing protocol in order to efficiently construct rope-ladders in wireless networks. By design, the paths which are constructed by our protocol are closely together which allows to quickly switch back and forth between them in cases of node or link failures. Hence, the size of loss gaps (i.e. the number of...

2010-01-01

99

Ladder structures for multidimensional linear-phase perfect reconstruction filter banks and wavelets  

Science.gov (United States)

The design of multidimensional filter banks and wavelets have been areas of active research for use in video and image communication systems. At the same time efficient structures for the implementation of such filters are of importance. In 1-D, the well known lattice structure and the recently introduced ladder structure are attractive. However, their extensions to higher dimensions (m-D) have been limited. In this paper we reintroduce the ladder structure, with the purpose of transforming the structure into m-D using the McClellan transform.

Kalker, A. A. C. M.; Shah, I. A.

1992-11-01

100

From quantum ladder climbing to classical autoresonance  

International Nuclear Information System (INIS)

The autoresonance phenomenon allows excitation of a classical, oscillatory nonlinear system to high energies by using a weak, chirped frequency forcing. Ladder climbing is its counterpart in quantum mechanics. Here, for the first time to our knowledge, conditions for the transition from the quantum to the classical regimes are outlined. The similarities and differences between the two approaches are presented

2004-01-01

 
 
 
 
101

Hadron structure in the ladder model  

International Nuclear Information System (INIS)

The (flavor non-singlet) Green's function to find a far-off-shell quark in a hadron is obtained in the renormalization group improved ladder model for QCD in the space-like axial gauge. Particular attention is paid to the role of the singularity in the gluon propagator. 4 figures

1979-01-01

102

P+ ion implantation of ladder polymer BBL  

International Nuclear Information System (INIS)

Ladder polymer poly(benzimidazobenzophenathroline) (BBL) was doped with P+ by ion implantation of 30 keV, 4 x 1016 P+ ions/cm2. The changes of spectroscopic characteristics (IR, UV-visible and ESR) and conductivity were observed. The BBL film doped by ICl was also studied as a contrast

1995-07-01

103

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

104

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.

Lyong Hung Ngoc

2009-04-01

105

A portable bio-amplifier for electric fish research: design and construction  

Directory of Open Access Journals (Sweden)

Full Text Available The weak electric organ discharges (EODs of gymnotiform knife fishes can be readily amplified with a wideband amplifier connected to submerged electrodes. The output from such an amplifier can then be monitored with audio speakers or digitized for subsequent analysis. Commercially available devices are expensive and usually require mains electrical power. Here we provide design notes and instructions for the construction and calibration of a cheap, portable, battery-powered, AC-coupled wideband bio-amplifier. This device was designed to allow electric fishes to be located in the field, and also to permit the relatively noise-free acquisition of EOD waveforms from specimens held in temporary captivity. This contribution is intended to encourage students of neotropical ichthyology to explore electric signaling in gymnotiform fishes.As fracas descargas dos órgãos elétricos (EODs dos gimnotiformes podem ser facilmente amplificadas com um amplificador de banda larga conectado a eletrodos submersos. A saída do amplificador pode ser monitorada com auto-falantes ou digitalizada para análise subsequente. Equipamentos disponíveis comercialmente são caros e requerem fontes elétricas potentes. Nós fornecemos aqui o esquema e as instruções para a construção e calibragem de um bio-amplificador barato, portátil, energizado à bateria recarregável. Este equipamento foi desenhado para permitir a localização de peixes elétricos no campo, além de permitir a aquisiçào relativamente sem ruídos de ondas de EODs de espécimes mantidos temporariamente em cativeiro. Esta contribuição pretende encorajar estudantes de Ictiologia Neotropical a explorar sinais elétricos em peixes gymnotiformes.

Jonathan K. Wells

2006-06-01

106

Design a light pattern of multiple concentric circles for LED fishing lamps using Fourier series and an energy mapping method.  

Science.gov (United States)

Fourier series and an energy mapping method were used in this study to design a lens that produces a light pattern of multiple concentric circles (LPMCC) for a light-emitting diode (LED) fishing lamp. Fourier series were used to represent the light intensity distribution curve (LIDC) of the LPMCC light pattern. Energy mapping involves performing angular energy mapping based on the LIDCs of an LED light source and LPMCC to design a freeform lens. Type I and Type II LPMCC lenses were designed according to the phototaxis behavior of fish to create a LPMCC light pattern of interleaving light-dark zones that attracts fish shoals to stay in an area for a long period. The experimental results indicated that, in comparing the LIDCs of the Type I and II lenses with the respective simulation values, the normalized cross-correlation (NCC) value reached 96%. According to a 24-hour observation of the phototaxis of Poecilia reticulata to evaluate the effectiveness of the proposed light pattern to attract fish, when a fish shoal was habituated to a light source that emitted constant illumination light, it gradually moved away from the intense light zone and hovered around the junction of the light and dark zones. In the future, the design used in this study can be applied to LED fishing lamps to replace traditional fishing lamps. PMID:24921540

Shen, S C; Li, J S; Huang, M C

2014-06-01

107

Yakima River Basin Fish Passage Phase II Fish Screen Construction, Project Completion Report.  

Energy Technology Data Exchange (ETDEWEB)

On December 5, 1980, Congress passed the Pacific Northwest Electric Power Planning and Conservation Act (Public Law 96-501). The Act created the Northwest Power Planning Council (now the Northwest Power and Conservation Council). The Council was charged with the responsibility to prepare a Regional Conservation and Electric Power Plan and to develop a program to protect, mitigate, and enhance fish and wildlife including related spawning grounds and habitat on the Columbia River and its tributaries. The Council adopted its Fish and Wildlife Program on November 15, 1982. Section 800 of the Program addresses measures in the Yakima River Basin. The Yakima measures were intended to help mitigate hydroelectric impacts in the basin and provide off-site mitigation to compensate for fish losses caused by hydroelectric project development and operations throughout the Columbia River Basin. The Bonneville Power Administration (BPA) was designated as a major source of funding for such off-site mitigation measures and was requested to initiate discussions with the appropriate Federal project operators and the Council to determine the most expeditious means for funding and implementing the program. The primary measures proposed for rapid implementation in the Yakima River basin were the installation of fish passage and protective facilities. Sec. 109 of The Hoover Power Plant Act of 1984, authorized the Secretary of the Interior to design, construct, operate, and maintain fish passage facilities within the Yakima River Basin. Under Phase I of the program, improvements to existing fish passage facilities and installation of new fish ladders and fish screens at 16 of the largest existing diversion dams and canals were begun in 1984 and were completed in 1990. The Yakima Phase II fish passage program is an extension of the Phase I program. In 1988, the Yakama Nation (YN) submitted an application to amend Sections 803(b) and 1403(4.5) of the Northwest Power and Conservation Council's Columbia River Basin Fish and Wildlife Program to begin preliminary design on the Phase II fish screen program. Based on citizen and agency endorsement, the Council approved the amendment in 1989. The Council authorized BPA to provide funding for Phase II screens through the Fish and Wildlife Program. BPA then asked the Bureau of Reclamation to provide engineering and design expertise to the Phase II projects.

Hudson, R. Dennis

2008-01-01

108

Fish passes  

…many cases significant cost savings can be made through using tried and tested designs and through the identification of design flaws at this stage of the fish pass construction process. Some submitted fish pass designs are unlikely to work satisfactorily because of incorrect depths of water or because…

109

The use of morphometric analysis to predict the swimming efficiency of two Neotropical long-distance migratory species in fish passage  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study investigated the external body morphology (based on morphometric data) and the swimming efficiency in fish passages (based on the ascent time in a fish ladder) of two Neotropical long-distance migratory species. The fish were collected in the fish ladder of the Porto Primavera Hydroelectric Power Plant (known as Engenheiro Sergio Motta), upper Paraná River, Brazil. The species differ in several morphometric ratios related to swimming performance. Prochilodus lineatus exhibited a h...

Lucileine de Assumpção; Maristela Cavicchioli Makrakis; Sergio Makrakis; Ricardo Luiz Wagner; Patrícia Sarai da Silva; Ariane Furtado de Lima; Elaine Antoniassi Luiz Kashiwaqui

2012-01-01

110

New ladder operators for the monopole harmonics  

International Nuclear Information System (INIS)

Using the ladder operators shifting the index m of the associated Jacobi functions, for a given n, the monopole harmonics and their corresponding angular momentum operators are, respectively, extracted as the irreducible representation space and generators of su(2) Lie algebra. The indices n and m play the role of principal and azimuthal quantum numbers. By introducing the ladder operators shifting the index n of the same associated Jacobi functions, we also get a new type of the raising and lowering relations which are realized by the operators shifting only the index n of the monopole harmonics. Moreover, other symmetries, including the transformation of the irreducible representation spaces into each other, are derived based on the operators that shift the indices n and m of the monopole harmonics simultaneously and agreeably as well as simultaneously and inversely. Our results are reduced to spherical harmonics by eliminating magnetic charge of the monopole

2007-02-01

111

Hood River and Pelton Ladder Evaluation Studies, Annual Report 2000-2001.  

Energy Technology Data Exchange (ETDEWEB)

The Bonneville Power Administration (BPA) funded the development of two master plans which outline the rationale, and general approach, for implementing a defined group of projects that are an integral part of a comprehensive watershed goal to 'Protect, enhance and restore wild and natural populations of anadromous and resident fish within the Hood River Subbasin'. The Hood River Production Master Plan and the Pelton Ladder Master Plan were completed in 1991 and subsequently approved by the Northwest Power Planning Council in 1992. Action items identified in the two master plans, as well as in a later document entitled 'Hood River/Pelton Ladder Master Agreement' (ODFW and CTWSRO Undated), are designed to achieve two biological fish objectives: (1) to increase production of wild summer and winter steelhead (Oncorhynchus mykiss) to levels commensurate with the subbasins current carrying capacity and (2) re-establishing a self-sustaining population of spring chinook salmon (Oncorhynchus tshawytscha). Numerical fish objectives for subbasin escapement, spawner escapement, and subbasin harvest are defined for each of these species in Coccoli (2000). Several projects are presently funded by the BPA to achieve the Hood River subbasin's numerical fish objectives for summer and winter steelhead and spring chinook salmon. They include BPA project numbers 1998-021-00 (Hood River Fish Habitat), 1998-053-03 (Hood River Production Program - CTWSRO: M&E), 1998-053-07 (Parkdale Fish Facility), 1998-053-08 (Powerdale/Oak Springs O&M), and 1998-053-12 (Hood River Steelhead Genetics Study). Collectively, they are implemented under the umbrella of what has come to be defined as the Hood River Production Program (HRPP). The HRPP is jointly implemented by the Oregon Department of Fish and Wildlife (ODFW) and The Confederated Tribes of the Warm Springs Reservation of Oregon (CTWSRO). Strategies for achieving the HRPP's biological fish objectives for the Hood River subbasin were initially devised based on various assumptions about (1) subbasin carrying capacity, (2) survival rates for selected life history stages, and (3) historic and current escapements of wild, natural, and hatchery stocks of anadromous salmonids to the Hood River subbasin. The Oregon Department of Fish and Wildlife began funding a monitoring and evaluation (M&E) project in December 1991 to collect the quantitative biological information needed to (1) more accurately assess the validity of these assumptions and (2) evaluate the proposed hatchery supplementation component of the HRPP. Bonneville Power Administration assumed funding of the M&E project in August 1992. The M&E project was initially confined to sampling anadromous salmonids escaping to an adult trapping facility operated at Powerdale Dam; which is located at River Mile (RM) 4.5 on the mainstem of the Hood River. Stock specific life history and biological data was collected to (1) monitor subbasin spawner escapements and (2) collect pre-implementation data critical to evaluating the newly proposed HRPP's potential biological impact on indigenous populations of resident fish. The scope of the M&E project was expanded in 1994 to collect the data needed to quantify (1) subbasin smolt production and carrying capacity, (2) smolt to adult survival rates, and (3) the spatial distribution of indigenous populations of summer and winter steelhead, spring and fall chinook salmon, and coho salmon. A creel was incorporated into the M&E project in December 1996 to evaluate the HRPP with respect to its defined subbasin and spawner escapement objectives for Hood River stocks of wild and hatchery summer and winter steelhead and for natural and Deschutes stock hatchery spring chinook salmon. In 1996, the M&E project also began monitoring streamflow at various locations in the Hood River subbasin. Streamflow data will be used to correlate subbasin smolt production with summer streamflows. Data collected from 1991-1999 is reported in the following annual progress report

Olsen, Erik

2009-09-01

112

Entanglement spectra of quantum Heisenberg ladders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Bipartite entanglement measures are fantastic tools to investigate quantum phases of correlated electrons. Here, I analyze the entanglement spectrum of **gapped** two-leg quantum Heisenberg ladders on a periodic ribbon partitioned into two identical periodic chains. Comparison of various entanglement entropies proposed in the literature is given. The entanglement spectrum is shown to closely reflect the low-energy gapless spectrum of each individual edge, for any sign of the...

Poilblanc, Didier

2010-01-01

113

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

114

Magnetization plateaux in dimerized spin ladder arrays  

CERN Document Server

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

115

Mixed spin ladders with exotic ground states  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the "mixed spin" isotropic ladder system having S=1 spins on one leg and S=1/2 spins on the other, with general-type exchange interactions between spins on neighboring rungs. A set of model Hamiltonians with exact ground states in the form of a certain matrix product wave function is obtained. We show that sufficiently strong frustration can lead to exotic singlet ground states with infinite (exponential) degeneracy. We also list a couple of rather simple models wit...

Kolezhuk, A. K.; Mikeska, H. -j

1997-01-01

116

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

117

Magnetic Properties of Zig-Zag Ladders  

CERN Document Server

We analyze the phase diagram of a system of spin-1/2 Heisenberg antiferromagnetic chains interacting through a zig-zag coupling, also called zig-zag ladders. Using bosonization techniques we study how a spin-gap or more generally plateaux in magnetization curves arise in different situations. While for coupled XXZ chains, one has to deal with a recently discovered chiral perturbation, the coupling term which is present for normal ladders is restored by an external magnetic field, dimerization or the presence of charge carriers. We then proceed with a numerical investigation of the phase diagram of two coupled Heisenberg chains in the presence of a magnetic field. Unusual behaviour is found for ferromagnetic coupled antiferromagnetic chains. Finally, for three (and more) legs one can choose different inequivalent types of coupling between the chains. We find that the three-leg ladder can exhibit a spin-gap and/or non-trivial plateaux in the magnetization curve whose appearance strongly depends on the choice of...

Cabra, D C; Pujol, P

2000-01-01

118

A portable bio-amplifier for electric fish research: design and construction  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese As fracas descargas dos órgãos elétricos (EODs) dos gimnotiformes podem ser facilmente amplificadas com um amplificador de banda larga conectado a eletrodos submersos. A saída do amplificador pode ser monitorada com auto-falantes ou digitalizada para análise subsequente. Equipamentos disponíveis com [...] ercialmente são caros e requerem fontes elétricas potentes. Nós fornecemos aqui o esquema e as instruções para a construção e calibragem de um bio-amplificador barato, portátil, energizado à bateria recarregável. Este equipamento foi desenhado para permitir a localização de peixes elétricos no campo, além de permitir a aquisiçào relativamente sem ruídos de ondas de EODs de espécimes mantidos temporariamente em cativeiro. Esta contribuição pretende encorajar estudantes de Ictiologia Neotropical a explorar sinais elétricos em peixes gymnotiformes. Abstract in english The weak electric organ discharges (EODs) of gymnotiform knife fishes can be readily amplified with a wideband amplifier connected to submerged electrodes. The output from such an amplifier can then be monitored with audio speakers or digitized for subsequent analysis. Commercially available devices [...] are expensive and usually require mains electrical power. Here we provide design notes and instructions for the construction and calibration of a cheap, portable, battery-powered, AC-coupled wideband bio-amplifier. This device was designed to allow electric fishes to be located in the field, and also to permit the relatively noise-free acquisition of EOD waveforms from specimens held in temporary captivity. This contribution is intended to encourage students of neotropical ichthyology to explore electric signaling in gymnotiform fishes.

Jonathan K., Wells; William G. R., Crampton.

119

D0 Silicon Upgrade: Ladder Removal Stress Analysis  

International Nuclear Information System (INIS)

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.

1994-01-01

120

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

 
 
 
 
121

Theoretical and experimental studies on 104 MHz ladder IH-RFQ accelerator  

Energy Technology Data Exchange (ETDEWEB)

To study feasibilities of RFQ-based ion implantation and accelerator mass spectroscopy (AMS), a 104 MHz ladder type IH radio-frequency quadrupole (Ladder IH-RFQ) accelerator has been developed. According to beam dynamics design, it is able to accelerate ions with mass-to-charge ratio up to 14 from 2.9 keV/u to 35.7 keV/u. As a specific feature, the output beam energy spread is as low as 0.6% realized by using internal discrete bunching method. A rod-type RFQ structure, i.e. ladder IH-RFQ is adopted, taking advantage of its mechanical stability and symmetric inter-electrode field. Power test shows that specific shunt impedance of the constructed cavity reaches 178 k? m. During the beam commissioning, 210 ?A {sup 4}He{sup +} beam has been obtained, and the transmission efficiency is better than 70% at current of several tens ?A. The ladder IH-RFQ is proved to be very suitable for operating frequency above 100 MHz for light ions.

Nie, Y.C., E-mail: ycnie@pku.edu.cn [State Key Lab of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); DESY, Hamburg 22607 (Germany); Lu, Y.R.; Gao, S.L.; Yan, X.Q.; Guo, Z.Y.; Chen, J.E. [State Key Lab of Nuclear Physics and Technology, Peking University, Beijing 100871 (China)

2014-02-11

122

Theoretical and experimental studies on 104 MHz ladder IH-RFQ accelerator  

International Nuclear Information System (INIS)

To study feasibilities of RFQ-based ion implantation and accelerator mass spectroscopy (AMS), a 104 MHz ladder type IH radio-frequency quadrupole (Ladder IH-RFQ) accelerator has been developed. According to beam dynamics design, it is able to accelerate ions with mass-to-charge ratio up to 14 from 2.9 keV/u to 35.7 keV/u. As a specific feature, the output beam energy spread is as low as 0.6% realized by using internal discrete bunching method. A rod-type RFQ structure, i.e. ladder IH-RFQ is adopted, taking advantage of its mechanical stability and symmetric inter-electrode field. Power test shows that specific shunt impedance of the constructed cavity reaches 178 k? m. During the beam commissioning, 210 ?A 4He+ beam has been obtained, and the transmission efficiency is better than 70% at current of several tens ?A. The ladder IH-RFQ is proved to be very suitable for operating frequency above 100 MHz for light ions

2014-02-11

123

Crossing-symmetric rings, ladders, and exchanges  

Energy Technology Data Exchange (ETDEWEB)

A new approach is used in the description of fermion and boson systems at zero or finite temperature. We generalize the familiar ladder and chaining operations to construct a crossing-symmetric approximation to the two-particle vertex from the bare interaction. The explicit rules for this construction are given in terms of Feynman propagators. The high level of symmetry of the vertex simplifies the theory. In one form, the structure appears as a generalization of parquet diagrams. The energy, self-energy, and vertex satisfy a number of consistency relations.

Lande, A.; Smith, R.A.

1983-11-17

124

Surface plasmon polariton Wannier-Stark ladder.  

Science.gov (United States)

The propagation of a surface plasmon polariton on a planar metal surface perturbed by N equally spaced rectangular grooves, each with the same width but with varying depths, is investigated by the finite-difference time-domain method. For a linear dependence of the depth of the nth groove on n, the transmissivity of the surface plasmon polariton and of the power radiated into the vacuum above the surface, as functions of its frequency, consist of N equally spaced dips and peaks, respectively. These are the signatures of the surface plasmon polariton analog of a Wannier-Stark ladder. PMID:24690851

Kuzmiak, V; Maradudin, A A; Méndez, E R

2014-03-15

125

Integrable anisotropic spin-ladder model  

International Nuclear Information System (INIS)

We present an integrable spin-ladder model, which possesses a free parameter besides the rung coupling J. Wang's system based on the SU(4) symmetry can be obtained as a special case. The model is exactly solvable by means of the Bethe ansatz method. We determine the dependence on the anisotropy parameter of the phase transition between gapped and gapless spin excitations and present the phase diagram. Finally, we show that the model is a special case of a more general Hamiltonian with three free parameters

2001-08-01

126

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

127

Exactly soluble isotropic spin-1/2 ladder models  

International Nuclear Information System (INIS)

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

2003-12-12

128

Quantifying Ladder Fuels: A New Approach Using LiDAR  

Directory of Open Access Journals (Sweden)

Full Text Available We investigated the relationship between LiDAR and ladder fuels in the northern Sierra Nevada, California USA. Ladder fuels are often targeted in hazardous fuel reduction treatments due to their role in propagating fire from the forest floor to tree crowns. Despite their importance, ladder fuels are difficult to quantify. One common approach is to calculate canopy base height, but this has many potential sources of error. LiDAR may be a way forward to better characterize ladder fuels, but has only been used to address this question peripherally and in only a few instances. After establishing that landscape fuel treatments reduced canopy and ladder fuels at our site, we tested which LiDAR-derived metrics best differentiated treated from untreated areas. The percent cover between 2 and 4 m had the most explanatory power to distinguish treated from untreated pixels across a range of spatial scales. When compared to independent plot-based measures of ladder fuel classes, this metric differentiated between high and low levels of ladder fuels. These findings point to several immediate applications for land managers and suggest new avenues of study that could lead to possible improvements in the way that we model wildfire behavior across forested landscapes in the US.

Heather A. Kramer

2014-06-01

129

Spreading Design of Radioactivity in Sea Water, Algae and Fish Samples inthe Coastal of Muria Peninsula Area  

International Nuclear Information System (INIS)

Spreading design of radioactivity in sea water, brown algae (phaeopyceae)and kerapu fish (epeniphelus) samples in the coastal of Muria peninsula areahas been studied. This research was carried out with designed beside to knowspreading each radioactivity but also spreading design in relation to thecontent of Pu-239 and Cs-137. Samples taken, preparation and analysis basedon the procedures of environmental radioactivity analysis. The instrumentused for the analysis radioactivity were alpha counter with detector ZnS, lowlevel beta counter modified P3TM-BATAN with detector GM and spectrometergamma with detector Ge(Li). Alpha radioactivity obtained of sea water, algaeand fish were the fluctuation form of the natural background. Radionuclide ofPu-239 in samples not detect, because its concentration/radioactivity stillbelow the maximum concentration detection value of Pu-239 for algae and fishwas that 1.10 Bq/g, whereas for sea water was that 0.07 Bq/mL. Result for theradioactivity which give the highest alpha radioactivity obtained on thekerapu fish was that 1.56 x 10-3 Bq/g, beta radioactivity on sea water wasthat 1.75 x 102 mBq/L, gamma radioactivity of K-40 on brown algae was that3.72 x 10-2 Bq/g and gamma radioactivity of Tl-208 on fish as mentionedabove was that 1.35 x 10-2 Bq/g. All the peak spectrum gamma energy ofCs-137 do not detect with gamma counter, so there are not the radionuclide ofCs-137 in the samples. Spreading design of radioactivity which occur in thecoastal of Muria peninsula area for alpha radioactivity was found on kerapufish, beta radioactivities on sea water and gamma radioactivity on brownalgae and kerapu fish. (author)

2000-07-25

130

Bound states in weakly disordered spin ladders  

Energy Technology Data Exchange (ETDEWEB)

We study the appearance of bound states in the spin gap of spin-12 ladders induced by weak bond disorder. Starting from the strong-coupling limit, i.e., the limit of weakly coupled dimers, we perform a projection on the single-triplet subspace and derive the position of bound states for the single impurity problem of one modified coupling as well as for small impurity clusters. The case of a finite concentration of impurities is treated with the coherent-potential approximation (CPA) in the strong-coupling limit and compared with numerical results. Further, we analyze the details in the structure of the density of states and relate their origin to the influence of impurity clusters.

Arlego, M. [Departamento de Fisica, Universidad Nacional de La Plata, CC 67 (1900) La Plata (Argentina)]. E-mail: arlego@venus.fisica.unlp.edu.ar; Brenig, W. [Institut fuer Theoretische Physik, Technische Universitaet Braunschweig (Germany); Cabra, D.C. [Laboratoire de Physique Theorique, Universite Louis Pasteur Strasbourg (France); Heidrich-Meisner, F. [Institut fuer Theoretische Physik, Technische Universitaet Braunschweig (Germany); Honecker, A. [Institut fuer Theoretische Physik, Technische Universitaet Braunschweig (Germany); Rossini, G. [Departamento de Fisica, Universidad Nacional de La Plata, CC 67 (1900) La Plata (Argentina)

2005-04-30

131

Bound states in weakly disordered spin ladders  

CERN Document Server

We study the appearance of bound states in the spin gap of spin-1/2 ladders induced by weak bond disorder. Starting from the strong-coupling limit, i.e., the limit of weakly coupled dimers, we perform a projection on the single-triplet subspace and derive the position of bound states for the single impurity problem of one modified coupling as well as for small impurity clusters. The case of a finite concentration of impurities is treated with the coherent-potential approximation in the strong-coupling limit and compared with numerical results. Furthermore, we analyze the details in the structure of the density of states and relate their origin to the influence of impurity clusters.

Arlego, M; Cabra, D C; Heidrich-Meisner, F; Honecker, A; Rossini, G

2005-01-01

132

Bound states in weakly disordered spin ladders  

International Nuclear Information System (INIS)

We study the appearance of bound states in the spin gap of spin-12 ladders induced by weak bond disorder. Starting from the strong-coupling limit, i.e., the limit of weakly coupled dimers, we perform a projection on the single-triplet subspace and derive the position of bound states for the single impurity problem of one modified coupling as well as for small impurity clusters. The case of a finite concentration of impurities is treated with the coherent-potential approximation (CPA) in the strong-coupling limit and compared with numerical results. Further, we analyze the details in the structure of the density of states and relate their origin to the influence of impurity clusters

2005-04-30

133

Integrable Renormalization I: the Ladder Case  

CERN Document Server

In recent years a Hopf algebraic structure underlying the process of renormalization in quantum field theory was found. It led to a Birkhoff factorization for (regularized) Hopf algebra characters, i.e. for Feynman rules. In this work we would like to show that this Birkhoff factorization finds its natural formulation in terms of a classical r-matrix, coming from a Rota-Baxter structure underlying the target space of the regularized Hopf algebra characters. Working in the rooted tree Hopf algebra, the simple case of the Hopf subalgebra of ladder trees is treated in detail. The extension to the general case, i.e. the full Hopf algebra of rooted trees or Feynman graphs is briefly outlined.

Ebrahimi-Fard, K; Kreimer, D; Ebrahimi-Fard, Kurusch; Guo, Li; Kreimer, Dirk

2004-01-01

134

Integrable renormalization I: The ladder case  

International Nuclear Information System (INIS)

In recent years a Hopf algebraic structure underlying the process of renormalization in quantum field theory was found. It led to a Birkhoff factorization for (regularized) Hopf algebra characters, i.e., for Feynman rules. In this work we would like to show that this Birkhoff factorization finds its natural formulation in terms of a classical r-matrix, coming from a Rota-Baxter structure underlying the target space of the regularized Hopf algebra characters. Working in the rooted tree Hopf algebra, the simple case of the Hopf subalgebra of ladder trees is treated in detail. The extension to the general case, i.e., the full Hopf algebra of rooted trees or Feynman graphs, is briefly outlined

2004-10-01

135

Thévenin equivalents for inhomogeneous ladder networks of generators  

International Nuclear Information System (INIS)

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. (paper)

2013-05-01

136

Quantum phase transitions in trimerized zig-zag spin ladders  

CERN Document Server

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

137

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

138

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

139

Inflight Refueling Operator Career Ladder, AFSCs 11230, 11250, 11270, 11290.  

Science.gov (United States)

This is a report of an occupational survey of the Inflight Refueling Operator career ladder (AFSCs 11230, 11250, 11270, 11290) completed by the Occupational Survey Branch, USAF Occupational Measurement Center in August 1978. This is the first occupational...

1978-01-01

140

Magnetization Curves of Antiferromagnetic Heisenberg Spin-1/2 Ladders  

CERN Document Server

Magnetization processes of spin-1/2 Heisenberg ladders are studied using strong-coupling expansions, numerical diagonalization of finite systems and a bosonization approach. We find that the magnetization exhibits plateaux as a function of the applied field at certain rational fractions of the saturation value. Our main focus are ladders with 3 legs where plateaux with magnetization one third of the saturation value are shown to exist.

Cabra, D C; Pujol, P

1997-01-01

 
 
 
 
141

Resonant plasmon scattering by discrete breathers in Josephson junction ladders  

CERN Multimedia

We study the resonant scattering of plasmons (linear waves) by discrete breather excitations in Josephson junction ladders. We predict the existence of Fano resonances, and find them by computing the resonant vanishing of the transmission coefficient. We propose an experimental setup of detecting these resonances, and conduct numerical simulations which demonstrate the possibility to observe Fano resonances in the plasmon scattering by discrete breathers in Josephson junction ladders.

Miroshnichenko, A E; Flach, S; Fistul, M V; Ustinov, A V

2004-01-01

142

Dynamics of an SO(5) symmetric ladder model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We discuss properties of an exactly SO(5) symmetric ladder model. In the strong coupling limit we demonstrate how the SO(3)-symmetric description of spin ladders in terms of bond Bosons can be upgraded to an SO(5)-symmetric bond-Boson model, which provides a particularly simple example for the concept of SO(5) symmetry. Based on this representation we show that antiferro- magnetism on one hand and superconductivity on the other hand can be understood as condensation of eithe...

Eder, R.; Dorneich, A.; Zacher, M. G.; Hanke, W.; Zhang, Shou-cheng

1998-01-01

143

Response of fish populations to natural channel design restoration in streams of the Catskill Mountains, New York  

Science.gov (United States)

Many streams and rivers throughout North America have been extensively straightened, widened, and hardened since the middle 1800s, but related effects on aquatic ecosystems have seldom been monitored, described, or published. Beginning in the early 1990s, reach-level restoration efforts began to base projects on natural channel design (NCD) techniques and Rosgen's (1994b, 1996) river classification system in an effort to duplicate or mimic stable reference reach geomorphology. Four reaches in three streams of the Catskill Mountains, New York, were restored from 2000 to 2002 using NCD techniques to decrease bed and bank erosion rates, decrease sediment loads, and improve water quality. The effects of restoration on the health of fish assemblages were assessed through a before-after, control-impact (BACI) study design to quantify the net changes in population and community indices at treatment reaches relative to index changes at unaltered reference reaches from 1999 to 2004. After restoration, community richness and biomass at treatment reaches increased by more than one-third. Changes in fish communities were caused mainly by shifts in dominant species populations; fish community biomass and total fish abundance were generally dominated by daces or daces and sculpins before restoration and by one or more salmonid species after restoration. Density and biomass of eastern blacknose dace Rhinichthys atratulus, longnose dace R. cataractae, and slimy sculpin Cottus cognatus did not change appreciably, whereas net salmonid density and biomass increased substantially after restoration. These changes were driven primarily by large increases in populations of brown trout Salmo trutta. The findings demonstrate that the structure, function, and ultimately the health of resident fish populations and communities can be improved, at least over the short term, through NCD restoration in perturbed streams of the Catskill Mountains. ?? Copyright by the American Fisheries Society 2008.

Baldigo, B. P.; Warren, D. R.; Ernst, A. G.; Mulvihill, C. I.

2008-01-01

144

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

2008-12-01

145

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.

Alison M. Hutson

2012-10-01

146

Estimación de reservas en una compañía aseguradora. Una aplicación en Excel del método Chain-Ladder y Bootstrap || Estimating the Reserves in Insurance Companies: An Excel Application of the Chain-Ladder Method and Bootstrap  

Directory of Open Access Journals (Sweden)

Full Text Available Las compañías aseguradoras deben calcular la cuantía de las reservas y la dotación de provisiones para hacer frente al pago de siniestros que o bien no han sido comunicados o bien no han sido cerrados. En este trabajo, se aplica el método Chain-Ladder para la estimación puntual de las reservas y, posteriormente, se recurre al bootstrap para obtener el error de muestreo y una estimación por intervalos. Dado que el cálculo de las reservas es un problema real al que se enfrentan las aseguradoras, su resolución es de gran interés para los estudiantes de Ciencias Actuariales. Para facilitar la comprensión y el seguimiento del proceso a desarrollar, los métodos Chain-Ladder y bootstrap se ejecutan paso a paso en una aplicación Excel diseñada ad hoc. || Insurance companies have to estimate reserves and provisions to cover the payment of either unreported claims or unsettled claims. In this paper, we apply the Chain-Ladder method to obtain a point estimate of reserves, and then we use the bootstrap technique to estimate the margin of error and the confidence interval of the reserves. Since estimating reserves is a real problem which insurance companies have to face, its solving has a special interest for students of Actuarial Sciences. To ease the understanding and monitoring the process, the Chain-Ladder method and bootstrap is run step by step by using an Excel application designed for that purpose.

Coll-Serrano, Vicente

2012-01-01

147

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

148

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

2012-10-01

149

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 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 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 sea [...] son 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.

Arcifa, Marlene Sofia; Esguícero, André Luiz Henríques.

150

Majorana states in helical Shiba chains and ladders  

Science.gov (United States)

Motivated by recent proposals to realize Majorana bound states in chains and arrays of magnetic atoms deposited on top of a superconductor, we study the topological properties of various chain structures, ladders, and two-dimensional arrangements exhibiting magnetic helices. We show that magnetic domain walls where the chirality of a magnetic helix is inverted support two protected Majorana states giving rise to a tunneling conductance peak twice the height of a single Majorana state. The topological properties of coupled chains exhibit nontrivial behavior as a function of the number of chains beyond the even-odd dichotomy expected from the simple Z2 nature of coupled Majorana states. In addition, it is possible that a ladder of two or more coupled chains exhibit Majorana edge states even when decoupled chains are trivial. We formulate a general criterion for the number of Majorana edge states in multichain ladders and discuss some experimental consequences of our findings.

Pöyhönen, Kim; Westström, Alex; Röntynen, Joel; Ojanen, Teemu

2014-03-01

151

Incommensurate dynamics of resonant breathers in Josephson junction ladders  

CERN Multimedia

We present theoretical and experimental studies of resonant localized resistive states in a Josephson junction ladder. These complex breather states are obtained by tuning the breather frequency into the upper band of linear electromagnetic oscillations of the ladder. Their prominent feature is the appearance of resonant steps in the current-voltage (I-V) characteristics. We have found the resonant breather-like states displaying incommensurate dynamics. Numerical simulations show that these incommensurate resonant breathers persist for very low values of damping. Qualitatively similar incommensurate breather states are observed in experiments performed with Nb-based Josephson ladders. We explain the appearance of these states with the help of resonance-induced hysteresis features in the I-V dependence.

Fistul, M V; Flach, S; Schuster, M; Ustinov, A V

2001-01-01

152

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

CERN Document Server

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

153

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.

María de la Paz Montañez-Armenta

2011-05-01

154

Determination of selenium in fish from designated critical habitat of the Gunnison River, Colorado, summer 2011  

Science.gov (United States)

This report presents results for the summer 2011 sampling of muscle plugs from common carps (Cyprinus Linnaeus), roundtail chub (Gila robusta), and bonytail chub (Gila elegans) inhabiting critical habitat in the Gunnison River in Western Colorado. Total selenium in fish muscle plugs was determined by instrumental neutron activation analysis. Total selenium concentrations (range and mean ± standard deviation) in micrograms per gram dry weight for each species were as follows: common carp: 8.5 to 35, 13 ± 7.8; roundtail chub: 5.5 to 11.2, 7.3 ± 1.6; bonytail chub: 0.8 to 8.6, 3.9 ± 4.2. Selenium concentrations in muscle plugs from 4 out of 15 roundtail chub, all 15 common carp, and 2 out of 5 bonytail chub exceeded the 8 micrograms per gram dry weight toxicity guideline for selenium in fish muscle tissue.

May, Thomas W.; Walther, Michael J.

2012-01-01

155

Magnetic properties and quantum entanglement on decorated zigzag ladder  

International Nuclear Information System (INIS)

Magnetic properties and quantum entanglement of Heisenberg model with two-, three- and four- site exchange interactions on zigzag ladder are studied. Magnetic properties and concurrence (measure of quantum entanglement) are analyzed by means of variational mean-field-like treatment based on the Gibbs-Bogoliubov inequality. The magnetization plateau and second-order phase transition were obtained. A comparison of the entanglement and magnetic behavior for zigzag ladder is made. We have found that in the antiferromagnetic region the behavior of the concurrence coincides with the magnetization one

2011-01-01

156

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

2012-01-01

157

A snakes and ladders representation of stock prices and returns  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Snakes and ladders is an ancient Indian game of chance that offers amusement as well as a metaphor for life’s many ups and downs. Games offer useful and fun ways of conveying ideas as well as solution techniques and this game has considerable mathematical tractability. This note shows how snakes and ladders can be used to represent the ups and downs of share ownership and solve for fair values of a multistage project that pays fixed dividends at uncertain completion times and has random ret...

2009-01-01

158

Ladder operators and differential equations for multiple orthogonal polynomials  

International Nuclear Information System (INIS)

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. (paper)

2013-05-24

159

Ladder operators and differential equations for multiple orthogonal polynomials  

CERN Document Server

In this paper, we obtain the ladder operators and associated compatibility conditions for the type I and the type 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; Zhang, Lun

2012-01-01

160

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

 
 
 
 
161

DUNDRUM Restriction-Intrusion of Liberty Ladders (DRILL) Audit Toolkit  

LENUS (Irish Health Repository)

This series of rating \\'ladders\\' is intended to allow a quantitative and qualitative analysis of the use of restrictive and intrusive interventions as part of the therapeutic management of violence and aggression in psychiatric hospital settings. This is an evolving handbook. The ladders are currently organised to facilitate a behavioural analysis. Context, antecedents, behaviour, interventions, consequences are conceptualised as a series of events organised in temporal sequence so that causes, interactions and effects can be considered. The complexity of analysis possible is limited by the statistical power of the numbers of cases and events available. \\r\

Kennedy, Harry

2011-09-01

162

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

2006-01-01

163

Impact of Small Hydro-Power Plants on Salmonid Fishes Spawning Migrations Maž?j? hidroelektrini? ?taka lašišini? žuv? neršto migracijai  

Directory of Open Access Journals (Sweden)

Full Text Available In 2000 and 2005, fish ladders were built in Vilnia and Siesartis rivers providing fish access to another 10 and 25 km of the rivers respectively. The analysis of redd distribution and abundance in both rivers revealed that the construction of fish ladders significantly increased the number and share of redds above dams, however, a significant increase in redds above the dam occurred 2-4 years after fish ladders construction supporting homing behaviour as one of the most important factors for the recolonization of the newly accessible habitats. The tracking of radio tagged salmon and sea trout revealed that statistically, significantly more time, fishes spent in the middle part of fish ladders. Assessed fish ladders efficiency for migrating salmonids made 66%. Minor construction defects and lack of protection were the main factors reducing fishway efficiency. Based on radio tracking data, recommendations are given for minor changes in fish ladders construction and operating schedule to increase the efficiency of fish ladders.Article in EnglishSiekiant sukurti palankias žuv? migracijos s?lygas ir atverti migracijos kelius ? upi? aukštupius Vilnios ir Siesarties up?se 2000 ir 2005 m. atitinkamai buvo pastatyti kaskadinio tipo žuvitakiai. Abiejose up?se atlikti lašišini? žuv? nerštavie?i? tyrimai parod?, kad ?rengti žuvitakiai padar? didel? ?tak? lizd? sklaidai up?je – j? labai padaug?jo pra?jus 2–4 metams po žuvitaki? ?rengimo aukš?iau patvankos. Tai gal?t? b?ti aiškinama „homingo“ ir nauj? nerštui tinkam? plot? atradimu. Valt?n? žuvitakio efektyvumo tyrimai, taikant radijo telemetrinius metodus, parod?, kad didži?j? dal? laiko, ?veikdamos žuvitak?, žuvys sugaišta vidurin?je jo dalyje. Nustatytas žuvitakio efektyvumas siek? 66 %. Straipsnyje pateikti pagrindiniai nustatyti žuvitaki? tr?kumai, kuri? esm? – nedideli techniniai statinio tr?kumai ir menka žuvitaki? apsauga žuv? migracijos metu. Pateiktos rekomendacijos žuvitaki? efektyvumui pagerinti. Straipsnis angl? kalba

K?stutis Skrupskelis

2009-04-01

164

Identification of repeat sequence heterogeneity at the polymorphic short tandem repeat locus HUMTH01[AATG]n and reassignment of alleles in population analysis by using a locus-specific allelic ladder.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An allelic ladder containing amplified sequences of seven alleles of the polymorphic human tyrosine hydroxylase locus, HUMTH01, was constructed and employed as a standard marker. Sequence analysis of each ladder component indicates that fragments differ by integral multiples of the AATG core repeat sequence characteristic of this locus. Individual alleles are designated "5" through "11," according to the number of complete reiterations of the core repeat contained within them. Comparison of t...

Puers, C.; Hammond, H. A.; Jin, L.; Caskey, C. T.; Schumm, J. W.

1993-01-01

165

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.

166

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 SciELO Brazil | Language: English 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 imp [...] lantação 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. 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 b [...] uilt 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.

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

167

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

2012-10-01

168

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

169

Competency-Based Nursing Career Ladder Model. Final Report.  

Science.gov (United States)

An open-entry/open-exit competency-based nursing career ladder model was developed to demonstrate the articulation process from high school through licensed vocational nursing (LVN), associate degree nursing (ADN), and baccalaureate degree-level nursing (BSN) programs. The model was based on data obtained from a review of the literature on (1)…

Wilson, Janie Menchaca; And Others

170

Towards flavored bound states beyond rainbows and ladders  

CERN Multimedia

We give a snapshot of recent progress in solving the Dyson-Schwinger equation with a beyond rainbow-ladder ansatz for the dressed quark-gluon vertex which includes ghost contributions. We discuss the motivations for this approach with regard to heavy-flavored bound states and form factors and briefly describe future steps to be taken.

El-Bennich, B; Paracha, M A; de Melo, J P B C

2013-01-01

171

Compass model on a ladder and square clusters  

Science.gov (United States)

We obtained exact specific heat of the quantum compass model on the square L × L clusters with L = 2, 3, 4, 5 using Kernel Polynomial Method and compare them with the specific heat of a large compass ladder. Intersite correlations found in the ground state for these systems demonstrate that the quantum compass model differs from its classical version.

Brzezicki, Wojciech; Ole?, Andrzej M.

2010-01-01

172

Compass model on a ladder and square clusters  

International Nuclear Information System (INIS)

We obtained exact specific heat of the quantum compass model on the square L x L clusters with L = 2, 3, 4, 5 using Kernel Polynomial Method and compare them with the specific heat of a large compass ladder. Intersite correlations found in the ground state for these systems demonstrate that the quantum compass model differs from its classical version.

2010-01-01

173

Compass model on a ladder and square clusters  

Energy Technology Data Exchange (ETDEWEB)

We obtained exact specific heat of the quantum compass model on the square L x L clusters with L = 2, 3, 4, 5 using Kernel Polynomial Method and compare them with the specific heat of a large compass ladder. Intersite correlations found in the ground state for these systems demonstrate that the quantum compass model differs from its classical version.

Brzezicki, Wojciech; Oles, Andrzej M, E-mail: w.brzezicki@gmail.co, E-mail: a.m.oles@fkf.mpg.d [Institute of Physics, Jagellonian University, Reymonta 4, PL-30059 Krakow (Poland)

2010-01-15

174

Gevrey formal power series of Wannier-Stark ladders  

Energy Technology Data Exchange (ETDEWEB)

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.

Maioli, Marco; Sacchetti, Andrea [Department of Mathematics, University of Modena and Reggio Emilia, Via Campi 213/B, 41100, Modena (Italy)

2004-02-13

175

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

176

Ladder Theorem for a Leray alpha model of turbulence  

CERN Document Server

In this paper, we study the Modified Leray alpha model with periodic boundary conditions. We show that when the initial data are infinitely differentiable then the unique solution are infinitely differentiable in space and time. Furthermore, this regular solution verifies a sequence of energy inequalities that is called "ladder inequalities".

Ali, Hani

2009-01-01

177

Exactly soluble isotropic spin-1/2 ladder models  

CERN Document Server

The undeformed limit of the dilute two-color braid-monoid algebra gives a natural basis for the description of spin-1/2 ladder models, and allows different Baxterization Ansatze. Based on this observation we find an entire class of exactly soluble generalized isotropic spin-1/2 lader models.

Gritsev, V

2003-01-01

178

Nonperturbative study of generalized ladder graphs in a $\\phi^{2}\\chi$ theory  

CERN Document Server

The Feynman-Schwinger representation is used to construct scalar-scalar bound states for the set of all ladder and crossed-ladder graphs in a \\phi^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 quasi-potential 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 quasi-potential equations provide a better correspondence. Results for the calculated bound state wave functions are also presented.

Nieuwenhuis, T; Nieuwenhuis, Taco

1996-01-01

179

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

2013-04-01

180

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

 
 
 
 
181

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

182

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

183

Spatially resolved fish population analysis for designing MPAs : influence on inside and neighbouring habitats  

DEFF Research Database (Denmark)

The sandeel population analysis model (SPAM) is presented as a simulation tool for exploring the efficiency of Marine Protected Areas (MPAs) for sandeel stocks. SPAM simulates spatially resolved sandeel population distributions, based on a high-resolution map of all fishery-established sandbank habitats for settled sandeels, combined with a life-cycle model for survival, growth, and reproduction, and a three-dimensional hydrodynamic model for describing larval transport between the network of habitats. SPAM couples stock dynamics to ecosystem and anthropogenic forcing via well-defined drivers. The SPAM framework was tested using ICES statistical rectangle 37F2 as an MPA, and the impact on sandeel populations within the MPA and neighbouring habitats was investigated. Increased larval spillover compensated for lost catches inside the MPA. The temporal and spatial scales of stock response to MPAs demonstrated that ecosystem self-regulation must be included when modelling the efficiency of MPAs, and for lesser sandeel, that self-regulation partially counteracts the benefits of a fishing sanctuary. The use of realistic habitat connectivity is critical for both qualitative and quantitative MPA assessment. The results confirm that the stock levels are more sensitive to changes in life conditions of larval stages than later parts of the life cycle.

Christensen, Asbjørn; Mosegaard, Henrik

2009-01-01

184

Phase diagram of frustrated ladder and 2D antiferromagnets  

Science.gov (United States)

We investigate the low energy properties of the frustrated two leg diagonal ladder exhibiting both intra- and inter-chain frustration. The renormalization group is used to obtain the phase diagram while varying the microscopic lattice parameters. We particularly emphasize the role of the in-chain marginal operators, which is tuned by the in-chain frustration and can promote a dimer phase in the system. Finally, the physics of the quasi one dimensional diagonal ladder is incorporated into a two dimensional square lattice since the former is used as the primary structure to build up the square lattice. Within the validity of our method, the classical phases---a Néel antiferromagnet and a collinear antiferromagnet---are predicted. The results are compared to numerical DMRG calculations.

Metavitsiadis, Alexandros; Sellmann, Daniel; Eggert, Sebastian

2013-03-01

185

Experimental Critical Current Patterns in Josephson Junction Ladders  

CERN Multimedia

We present an experimental and theoretical study of the magnetic field dependence of the critical current of Josephson junction ladders. At variance with the well-known case of a one-dimensional (1D) parallel array of Josephson junctions the magnetic field patterns display a single minimum even for very low values of the self-inductance parameter $\\beta_{\\rm L}$. Experiments performed changing both the geometrical value of the inductance and the critical current of the junctions show a good agreement with numerical simulations. We argue that the observed magnetic field patterns are due to a peculiar mapping between the isotropic Josephson ladder and the 1D parallel array with the self-inductance parameter $\\beta_{\\rm L}^{\\rm eff}=\\beta_{\\rm L}+2$.

Binder, P; Fistul, M V; Ustinov, A V; Filatrella, G

2000-01-01

186

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

Science.gov (United States)

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. PMID:21769414

Sumith, Jayakody A; Munkittrick, Kelly R

2011-08-01

187

Superconducting gap for a 2-leg t-J ladder  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Single-particle diagonal and off-diagonal Green's functions of a 2-leg t-J ladder at 1/8-doping are investigated by Exact Diagonalisations techniques. A numerically tractable expression for the superconducting gap is proposed and the frequency dependence of the real and imaginary parts of the gap are determined. The role of the low-energy gapped spin modes whose energies are computed by a (one-step) Contractor Renormalization procedure are discussed.

Poilblanc, Didier; Scalapino, D. J.; Capponi, Sylvain

2003-01-01

188

Climbing the job ladder: New evidence of gender inequity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An explanation for the gender wage gap is that women are less able or less willing to 'climb the job ladder.' However, the empirical evidence on gender differences in job mobility has been mixed. Focusing on a subsample of younger, university-educated workers from an Australian longitudinal survey, we find strong evidence that the dynamics of promotions and employer changes worsen women's labour market position.

Johnston, David W.; Lee, Wang-sheng

2011-01-01

189

Phase diagram of ferrimagnetic ladders with bond-alternation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the phase diagram of a 2-leg bond-alternation spin-(1/2, 1) ladder for two different configurations using a quantum renormalization group approach. Although d-dimensional ferrimagnets show gapless behavior, we will explicitly show that the effect of the spin mixing and the bond-alternation can open the possibility for observing an energy gap. We show that the gapless phases of such systems can be equivalent to the 1-dimensional half-integer antiferroamgnets, besides...

Langari, A.; Abolfath, M.; Martin-delgado, M. A.

1999-01-01

190

ELICITING AND LADDERING PROSPECTIVE LANGUAGE TEACHERS’ CLASSROOM-RELATED CONSTRUCTS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This article has a dual aim. First, the author reports on how two techniques were used from personal construct psychology, dyadic elicitation and laddering (Fransella, Bell & Bannister, 2004:27-34, 39-43) to raise a cohort of prospective teachers’ awareness of their classroom-related constructs (N = 21). Second, the process for elicitation of the constructs depended on the trainees’ ability to deal with the cognitive and the...

Wilfred Greyling

2012-01-01

191

“Why Caipirinha?”- The Online via Chat Laddering Technique CAN Answer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 asking the followi...

2011-01-01

192

Implicit ladder summation in the Hartree-Fock-Bogoliubov approach  

CERN Document Server

The fully variational Hartree Fock Bogoliubov approach for bosons is studied in the limit of zero range forces in two- and three-dimensions. The equation of state obtained in two-dimensions is expressed in a parametric form. It is shown that the $\\Lambda$ potential permits to perform an implicit summation of the ladder diagrams without leaving the variational scheme, restoring thus the consistency of this approximation.

Pricoupenko, Ludovic

2011-01-01

193

The search for competing charge orders in frustrated ladder systems  

International Nuclear Information System (INIS)

A recent study revealed the dynamics of the charge sector of a one-dimensional quarter- filled electronic system with extended Hubbard interactions to be that of an effective pseudospin transverse-field Ising model (TFIM) in the strong coupling limit. With the twin motivations of studying the co-existing charge and spin order found in strongly correlated chain systems and the effects of inter-chain couplings, we investigate the phase diagram of coupled effective (TFIM) systems. A bosonisation and RG analysis for a two-leg TFIM ladder yields a rich phase diagram showing Wigner/Peierls charge order and Neel/dimer spin order. In a broad parameter regime, the orbital antiferromagnetic phase is found to be stable. An intermediate gapless phase of finite width is found to lie in between two charge-ordered gapped phases. Kosterlitz-Thouless transitions are found to lead from the gapless phase to either of the charge-ordered phases. Low energy effective Hamiltonian analyses of a strongly coupled 2-chain ladder system confirm a phase diagram with in-chain CO, rung-dimer, and orbital antiferromagnetic ordered phases with varying interchain couplings as well as superconductivity upon hole-doping. Our work is potentially relevant for a unified description of a class of strongly correlated, quarter-filled chain and ladder systems. (autor)

2007-01-01

194

Novel organic-inorganic layered oxide with spin ladder structure  

CERN Document Server

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

195

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 asking 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.

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

196

“Why Caipirinha?”- The Online via Chat Laddering Technique CAN Answer  

Directory of Open Access Journals (Sweden)

Full Text Available 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 asking 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.

Bruno Bordeaux-Rego

2011-04-01

197

Magnetization plateau and cusp in S=1 spin ladder  

Energy Technology Data Exchange (ETDEWEB)

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=M{sub s}/4, where M{sub s} is the saturation magnetization. We propose possible mechanisms of the M=M{sub s}/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=M{sub s}/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=M{sub s}/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 M{sub s}/2 plateau problem. We show that a small rung coupling cannot yield the M{sub s}/2 plateau, which is quite different from the M=0 plateau problem of the S=1/2 ladder.

Sakai, T.; Okamoto, K.; Okunishi, K.; Kindo, K.; Narumi, Y.; Hosokoshi, Y.; Katoh, K.; Inoue, K.; Goto, T

2004-04-30

198

Functional Renormalization Group calculation of the Fermi surface of a spin-ladder  

CERN Document Server

We study non conventional superconductivity on a ladder, improving the predictions of the Hubbard model. The determination of the Fermi surface, in 2 or 3 dimensions, remains a very hard task, but it is exactly solvable for a single ladder. We use functional Renormalisation Group methods, which prove, here, scheme-dependant. In the superconducting phase, the binding/antibinding gap is stabilized, but in the antiferromagnetic phase, it shrinks and the ladder turns one-dimensional.

Abramovici, G; Abramovici, Gilles; H\\'{e}ritier, Michel

2007-01-01

199

Development of ultra-light pixelated ladders for an ILC vertex detector  

CERN Document Server

The development of ultra-light pixelated ladders is motivated by the requirements of the ILD vertex detector at ILC. This paper summarizes three projects related to system integration. The PLUME project tackles the issue of assembling double-sided ladders. The SERWIETE project deals with a more innovative concept and consists in making single-sided unsupported ladders embedded in an extra thin plastic enveloppe. AIDA, the last project, aims at building a framework reproducing the experimental running conditions where sets of ladders could be tested.

Chon-Sen, N; Claus, G; De Masi, R; Deveaux, M; Dulinski, W; Goffe, M; Goldstein, J; Gregor, I -M; Imhoff, Ch Hu-Guo M; Müntz, C; Nomerotski, A; Santos, C; Schrader, C; Specht, M; Stroth, J; Winter, M

2010-01-01

200

Majorana fermions qubit states and non-Abelian braiding statistics in quenched inhomogeneous spin ladders  

Science.gov (United States)

In studying Majorana fermions (MFs) in a spin ladder model, we numerically show that their qubit state can be read out by measuring fusion excitations in quenched inhomogeneous spin ladders. We construct an exactly solvable T-junction spin ladder model that can be used to implement MF braid operations. With braiding simulated numerically as nonequilibrium quench processes, we verify that the MFs in our spin ladder model obey non-Abelian braiding statistics. Our scheme provides a promising platform to study exotic properties of MFs and a broad range of applications in topological quantum computation.

He, Yin-Chen; Chen, Yan

2013-11-01

 
 
 
 
201

Fish passes  

…adequate fish do not usually leap. Large fish such as adult salmon can ascend structures where the water velocity may be over 5m/sec, since the maximum swimming speed and endurance of a fish normally increases with increasing length of the fish. Conversely, small fish such as first year returning sea trout…

202

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

203

Vitamin content of fish and fish products consumed in Portugal  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Portuguese Food Composition Table only includes values for vitamins A, B1, B2, PP determined before 1963. Most fish and fish products consumed in Portugal are not included in international food composition tables. Aims: To study vitamin content of fish and fish products consumed in Portugal. Design: Vitamins A, E, D, B1, B2, B6, B12, PP and Folate content was determined in fifty-six samples of raw and cooked fish and fish products, collected between October 1999 and February 2002....

Dias, M. Grac?a; Sa?nchez, M. V.; Ba?rtolo, H.; Oliveira, Lui?sa

2003-01-01

204

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

2011-01-01

205

Climbing the Jaynes-Cummings ladder by photon counting  

CERN Multimedia

We present a new method to observe direct experimental evidence of Jaynes--Cummings nonlinearities in a strongly dissipative cavity quantum electrodynamics system, where large losses compete with the strong light-matter interaction. This is a highly topical problem, particularly for quantum dots in microcavities where transitions from higher rungs of the Jaynes--Cummings ladder remain to be evidenced explicitly. We compare coherent and incoherent excitations of the system and find that resonant excitation of the detuned emitter make it possible to unambiguously evidence few photon quantum nonlinearities in currently available experimental systems.

Laussy, Fabrice P; Schrapp, Michael; Laucht, Arne; Finley, Jonathan J

2011-01-01

206

Ladder operators and recursion relations for the associated Bessel polynomials  

International Nuclear Information System (INIS)

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

2006-10-30

207

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

208

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

209

Crossing and anticrossing of resonances: The Wannier-Stark ladders  

International Nuclear Information System (INIS)

In the framework of regular perturbation theory we discuss the weak field crossing behavior of the resonances in double ladder (and double well) Stark problems. We get a precise condition for the anticrossing in terms of the Agmon length of the Zener barriers. This condition has a simple physical meaning: as a general rule we have anticrossing and beating effect if the lifetime of the system is larger than the beating period. Of course, we have full delocalization in the anticrossing case only. 32 refs., 4 figs

1995-08-01

210

Crossing and anticrossing of resonances: The Wannier-Stark ladders  

Energy Technology Data Exchange (ETDEWEB)

In the framework of regular perturbation theory we discuss the weak field crossing behavior of the resonances in double ladder (and double well) Stark problems. We get a precise condition for the anticrossing in terms of the Agmon length of the Zener barriers. This condition has a simple physical meaning: as a general rule we have anticrossing and beating effect if the lifetime of the system is larger than the beating period. Of course, we have full delocalization in the anticrossing case only. 32 refs., 4 figs.

Grecchi, V. [Universita di Bologna (Italy); Sacchetti, A. [Universita di Modena (Italy)

1995-08-01

211

Effective action and quantum mechanics. Validity of ladder approximation  

International Nuclear Information System (INIS)

The formalism of the effective action ?[?] is applied to the quantum mechanical system and the equations determining the energy eigenvalue of the excited levels as a zero of ordinary function are derived. Bethe-Salpeter type equation in the ladder approximation is shown to give the correct eigenvalue, if it is evaluated perturbatively, only when the self-energy type correction is included. Calculations show that the correct perturbative value is obtained if ?[?] is kept up to lowest order and no further approximation is allowed. (author)

1994-10-01

212

Twisted-order parameter applied to dimerized ladders  

Energy Technology Data Exchange (ETDEWEB)

We apply the twisted-order parameter (TOP) for dimerized quantum spin ladders to locate the critical points that separate gapped phases representing quantum spin liquids of various types. Using the density matrix renormalization group (DMRG), method, we find that the TOP is a good order parameter for these systems regardless of the number of legs. As a check, we reproduce with the DMRG and periodic boundary conditions the computations previously done with quantum Monte Carlo for one-dimensional S = 1/2, S = 1, S = 3/2 and S = 2 Heisenberg chains with alternating bonds.

Almeida, J; Martin-Delgado, M A [Departamento de Fisica Teorica I, Universidad Complutense, 28040 Madrid (Spain); Sierra, G [Instituto de Fisica Teorica, C.S.I.C.-U.A.M., Madrid (Spain)

2008-12-05

213

Twisted-order parameter applied to dimerized ladders  

International Nuclear Information System (INIS)

We apply the twisted-order parameter (TOP) for dimerized quantum spin ladders to locate the critical points that separate gapped phases representing quantum spin liquids of various types. Using the density matrix renormalization group (DMRG), method, we find that the TOP is a good order parameter for these systems regardless of the number of legs. As a check, we reproduce with the DMRG and periodic boundary conditions the computations previously done with quantum Monte Carlo for one-dimensional S = 1/2, S = 1, S = 3/2 and S = 2 Heisenberg chains with alternating bonds

2008-12-05

214

Period halving of Persistent Currents in Mesoscopic Mobius ladders  

CERN Document Server

We investigate the period halving of persistent currents(PCs) of non-interacting electrons in isolated mesoscopic M\\"{o}bius ladders without disorder, pierced by Aharonov-Bhom flux. The mechanisms of the period halving effect depend on the parity of the number of electrons as well as on the interchain hopping. Although the data of PCs in mesoscopic systems are sample-specific, some simple rules are found in the canonical ensemble average, such as all the odd harmonics of the PCs disappear, and the signals of even harmonics are non-negative. {PACS number(s): 73.23.Ra, 73.23.-b, 68.65.-k}

Wen Ji Deng; Ping, L I U; Wen-Ji, DENG; Ji-Huan, XU; Ping, LIU

2002-01-01

215

A quantum cable car for Wannier-Stark ladders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper studies the dynamics of transitions between the levels of a Wannier-Stark ladder induced by a resonant periodic driving. The analysis of the problem is done in terms of resonance quasienergy states, which take into account the metastable character of the Wannier-Stark states. It is shown that the periodic driving creates from a localized Wannier-Stark state an extended Bloch-like state with a spatial length varying in time as ~ t^1/2. Such a state can find applications in the field ...

Glu?ck, M.; Kolovsky, A. R.; Korsch, H. J.

2000-01-01

216

Beyond rainbow-ladder in bound state equations  

Science.gov (United States)

In this work we devise a new method to study quark-anti-quark interactions beyond simple ladder-exchange that yield massless pions in the chiral limit. The method is based on the requirement to have a representation of the quark-gluon vertex that is explicitly given in terms of quark dressings functions. We outline a general procedure to generate the Bethe-Salpeter kernel for a given vertex representation. Our method allows not only the identification of the mesons' masses but also the extraction of their Bethe-Salpeter wave functions exposing their internal structure. We exemplify our method with vertex models that are of phenomenological interest.

Heupel, Walter; Goecke, Tobias; Fischer, Christian S.

2014-05-01

217

Beyond Rainbow-Ladder in bound state equations  

CERN Document Server

In this work we devise a new method to study quark anti-quark interactions beyond simple ladder-exchange that yield massless pions in the chiral limit. The method is based on the requirement to have a representation of the quark-gluon vertex that is explicitly given in terms of quark dressings functions. We outline a general procedure to generate the Bethe-Salpeter kernel for a given vertex representation. Our method allows not only the identification of the mesons' masses but also the extraction of their Bethe-Salpeter wave functions exposing their internal structure. We exemplify our method with vertex models that are of phenomenological interest.

Heupel, Walter; Fischer, Christian S

2014-01-01

218

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

2011-04-01

219

Exact solutions and ladder operators for a new anharmonic oscillator  

International Nuclear Information System (INIS)

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

2005-06-06

220

nu. /sub 3/ vibrational ladder of SF/sub 6/  

Energy Technology Data Exchange (ETDEWEB)

From an analysis of the high-resolution spectrum of the 3..nu../sub 3/ manifold of SF/sub 6/, we have determined the anharmonicity constants to be (in reciprocal centimeters) X/sub 33/=-1.7426, G/sub 33/=0.9188, and T/sub 33/=-0.24635. By using these constants, one can for the first time to our knowledge accurately predict the energies of the lower-vibrational sublevels of the ..nu../sub 3/ ladder and determine the pathways for multiple-photon absorption.

Patterson, C.W.; Krohn, B.J.; Pine, A.S.

1981-01-01

 
 
 
 
221

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 spinon continuum at intermediate fields characteristic of the Luttinger-liquid phase. By tuning the magnetic field, we drive the fractionalization of magnons into spinons and, in this deconfined reg...

Thielemann, B.; Ruegg, C.; Ronnow, H. M.; Lauchli, A. M.; Caux, J. S.; Normand, B.; Biner, D.; Kramer, K. W.; Gudel, H. U.; Stahn, J.; Habicht, K.; Kiefer, K.; Boehm, M.; Mcmorrow, D. F.; Mesot, J.

2009-01-01

222

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

223

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

2011-12-01

224

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

225

The effect of instructions on potential slide-out failures during portable extension ladder angular positioning.  

Science.gov (United States)

Accidents involving portable ladders are a common cause of serious occupational and non-occupational injuries throughout the industrialized world. Many of these injuries could be prevented with better instruction on the proper usage of portable ladders. Research is reported that focused on both the human factors and engineering aspects of portable extension ladder usage based on common ladder setup procedures. Results of the human factors experiment revealed evidence of unsafe acts that could lead to catastrophic ladder slide-out accidents in real-life situations. Six different ladder setup methods were evaluated for safety and stability based on placement angles: the basic, 75 degree, stand-reach, L sticker, 4:1, and bubble level methods. Ideally, ladder users would set the ladder up at 75.5 degrees to achieve the consensus industry standard safest angle. Setup methods varied in complexity and nature of instruction. The level method produced the most accurate and the least variable results. The engineering analysis determined the coefficient of friction of a variety of clean and contaminated surfaces commonly used with ladders. This analysis determined the total number of slide-out failures that would likely have occurred in the data obtained in each of the ladder setup methods tested in the human factors experiment. Based on test participants' setup angles, the average calculated ladder slide-out failure rate was 8.7 percent for ladders positioned on a surface with the lowest measured coefficient of friction. When broken down by ladder setup method, the 4:1 method had a failure rate of 18.8 percent, the 75 degree method had a failure rate of 15.2 percent, and the basic method had a failure rate of 9.8 percent. The stand-reach and L sticker methods had identical failure rates at 3.3 percent and the level method was best at 1.1 percent. The level method provided the lowest error, least variability, and setup closest to the target angle of 75.5 degrees. Analysis of the overall results revealed the need for additional user training and clearer instructions affixed to ladders. This research is unique in that it combines an analysis and comparison of human factors and engineering in the same study. PMID:24594362

Campbell, Alan O; Pagano, Christopher C

2014-06-01

226

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

227

Absolutely continuous energy bands in the electronic spectrum of quasiperiodic ladder networks  

Science.gov (United States)

The energy spectra of quasi-one-dimensional quasiperiodic ladder networks are analyzed within a tight binding description. In particular, we show that if a selected set of sites in each strand of a ladder is tunnel-coupled to quantum dots attached from a side, absolutely continuous subbands can be generated in the spectrum if one tunes the dot potential and the dot-strand coupling appropriately. Typical cases with two and three strand Fibonacci ladders in the off-diagonal model are discussed in details. We also discuss the possibility of re-entrant insulator-metal transition for a general n-strand ladder network when n becomes large. The observations remain valid even in the case of a disordered ladder network with the same constituents. The results are analytically exact.

Pal, Biplab; Chakrabarti, Arunava

2014-06-01

228

Fish passes  

…increasing length of the fish. Conversely, small fish such as first year returning sea trout of only 0.3m in length may have difficulty in ascending jets of water at more than 3.5m/sec. Another factor which affects the ability of fish to ascend fish passes is the water temperature. Higher water temperatures…

229

Fish passes  

…downstream of the structure is greater than about 0.5m. Typically these sites can be identified by fish leaping clear of the water in an attempt to ascend the structure. Where fish passage is adequate fish do not usually leap. Large fish such as adult salmon can ascend structures where the water velocity…

230

Fish passes  

…out more about them. Fish Passes and Fish Pass Approval Salmon (Salmo salar L.) and sea trout (Salmo trutta L.) are migratory fish that are very important to the rural economy in England and Wales. Their complex life-cycle involves the migration of juvenile fish from freshwater to the sea and the migration…

231

A study of stark ladders via an evolution operator  

International Nuclear Information System (INIS)

Using an evolution operator reported earlier, the nature of energy spectrum of Bloch electrons in external electric field is studied and the circumstances under which stark ladders would exist are examined. At first a general expression for the energy spectrum is obtained. Then it is shown that the energy spectrum would correspond to an exact stark ladder provided the electric field is considered only upto first order. If the electric field is retained beyond first order, one obtains corrections to the stark levels corresponding to first order field. These correction terms are k- dependent and involve zener tunneling beyond first order. Small in magnitude, they produce a slight broadening of the first order stark levels. The exact forms of these correction terms are rather formidable; to exemplify, the form of 2nd order correction terms is shown. It is discussed briefly how the evolution operator of reference can be generalised to include the presence of optical field and thereby information regarding transitions depending on zener tunneling and optical absorption can be obtained. (author)

1980-08-01

232

Dimerized phase in the cross-coupled antiferromagnetic spin ladder  

Science.gov (United States)

We revisit the phase diagram of the frustrated s=1/2 spin ladder with antiferromagnetic rung and diagonal couplings. In particular, we reexamine the evidence for the columnar dimer phase, which has been predicted from analytic treatment of the model and has been claimed to be found in numerical calculations. By performing density-matrix renormalization-group (DMRG) calculations on long ladders, keeping a large number of states within the DMRG, and carrying out careful scaling in number of states kept and system size, we calculate the behavior of the dimer order parameter as a function of frustration strength. We find no positive numerical evidence for a finite dimer order parameter in the thermodynamic limit anywhere in the parameter regime in which the columnar dimer phase is expected to appear. Conservative error estimates in the scaling of our data place stringent limits on the maximum possible value of the dimer order parameter and the maximum possible extent of the parameter regime in which a sufficiently weak dimer phase could still exist.

Barcza, G.; Legeza, Ö.; Noack, R. M.; Sólyom, J.

2012-08-01

233

Two-step spin flop transition in quantum spin ladders  

Science.gov (United States)

It is well known that the antiferromagnet with easy-axis anisotropies exhibits a field-induced first-order phase transition, the so- called spin flop. In one-dimensional quantum spin systems, instead of it, a second-order phase transition occurs because of large quantum fluctuations[1]. Particularly the S=1 antiferromagnetic chain with the easy-axis single-ion anisotropy was revealed to exhibit two successive field-induced second-order transitions by our previous numerical analysis[2]. However, such transitions have not been obseved yet. Recently a two-step spin flop transition was observed in the spin ladder system IPA-CuCl3[3], which has ferromagnetic rung coupling. In order to clarify the mechanism of the two-step field-induced transition, we investigate the anisotropic spin ladder using the numerical diagonalization and the finite-size scaling analysis. As a result, we revealed that two different field-induced second-order quantum phase transitions possibly occur. Several phase diagrams are also presented. In addition we discuss on a possible two-step spin flop in other materials[4] and some frustrated systems. [1] C. N. Yang and C. P. Yang, Phys. Rev. 151 (1966) 258. [2] T. Sakai, Phys. Rev. B 58 (1998) 6268. [3] T. Masuda et al, Phys. Rev. Lett. 96 (2006) 047210. [4] H. Miyasaka et al, Inorg. Chem. 42 (2003) 8203.

Sakai, Toru; Okamoto, Kiyomi

2008-03-01

234

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

Science.gov (United States)

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. PMID:22820145

Hung, Tien-Chieh; Piedrahita, Raul H; Cheer, Angela

2012-12-01

235

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 squ...

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

2011-01-01

236

Computational flow simulation supporting the design of the Geesthacht fish pass; Numerische Modelluntersuchungen im Rahmen der Planung der Fischaufstiegsanlage Geesthacht  

Energy Technology Data Exchange (ETDEWEB)

In the year 2010 Europe's largest fish pass with basins at the Elbe-weir near Geesthacht was put into operation. Since then fish of many different kinds and sizes pass the building every day. The geometrical configuration of the facility, realized as a double slot pass, is based on extensive hydraulic model investigations. Thereby, apart from the flow characteristic within the building, also location-specific and operational aspects were to be analyzed and integrated into the planning concept. Due to the complex hydraulic boundary conditions as well as the high fish-ecological requirements a hybrid modeling approach with computational flow simulation in connection with physical model tests was employed, whereby substantial synergies as well as a good prognosis ability of the computer-aided simulation showed up. (orig.)

Oberle, Peter; Musall, Mark; Riesterer, Jochen; Nestmann, Franz [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (DE). Inst. fuer Wasser und Gewaesserentwicklung (IWG)

2012-07-01

237

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

2006-06-01

238

Nuclear Spin Relaxation in Hole Doped Two-Leg Ladders  

CERN Document Server

The nuclear spin-lattice relaxation rate ($1/T_{1}$) has been measured in the single crystals of hole doped two-leg ladder compounds Sr$_{14-x}$Ca$_{x}$Cu$_{24}$O$_{41}$ and in the undoped parent material La$_6$Ca$_8$Cu$_{24}$O$_{41}$. Comparison of $1/T_{1}$ at the Cu and the two distinct oxygen sites revealed that the major spectral weight of low frequency spin fluctuations is located near $q \\sim (\\pi, \\pi)$ for most of the temperature and doping ranges investigated. Remarkable difference in the temperature dependence of $1/T_1$ for the two oxygen sites in the heavily doped $x$=12 sample revealed reduction of singlet correlations between two legs in place of growing antiferromagnetic correlations along the leg direction with increasing temperature. Such behavior is most likely caused by the dissociation of bound hole pairs.

Fujiyama, S; Motoyama, N; Eisaki, H; Uchida, S I

2000-01-01

239

Phase sensitive quantum interference on forbidden transition in ladder scheme  

CERN Document Server

A three level ladder system is analyzed and the coherence of initially electric-dipole forbidden transition is calculated. Due to the presence of two laser fields the initially dipole forbidden transition becomes dynamically permitted due to ac Stark effect. It is shown that such transitions exhibit quantum-interference-related phenomena, such as electromagnetically induced transparency, gain without inversion and enhanced refractive index. Gain and dispersion characteristics of such transitions strongly depend upon the relative phase between the driving and the probe fields. Unlike allowed transitions, gain/absorption behavior of ac-Stark allowed transitions exhibit antisymmetric feature on the Rabi sidebands. It is found that absorption/gain spectra possess extremely narrow sub-natural resonances on these ac Stark allowed forbidden transitions. An interesting finding is simultaneous existence of gain and negative dispersion at Autler-Townes transition which may lead to both reduction of the group velocity a...

Koganov, Gennady A

2014-01-01

240

Attractive Tomonaga-Luttinger Liquid in a Quantum Spin Ladder  

Science.gov (United States)

We present NMR measurements of a strong-leg spin-1/2 Heisenberg antiferromagnetic ladder compound (C7H10N)2CuBr4 under magnetic fields up to 15 T in the temperature range from 1.2 K down to 50 mK. From the splitting of NMR lines, we determine the phase boundary and the order parameter of the low-temperature (three-dimensional) long-range-ordered phase. In the Tomonaga-Luttinger regime above the ordered phase, NMR relaxation reflects characteristic power-law decay of spin correlation functions as 1/T1?T1/2K-1, which allows us to determine the interaction parameter K as a function of field. We find that field-dependent K varies within the 1

Jeong, M.; Mayaffre, H.; Berthier, C.; Schmidiger, D.; Zheludev, A.; Horvati?, M.

2013-09-01

 
 
 
 
241

Consumers' perceptions of African wildlife meat : A laddering study  

DEFF Research Database (Denmark)

African wildlife meat offers South Africans' a healthy and novel red meat alternative, yet consumption is far less than that of beef and lamb. Laddering interviews with 40 respondents were employed to identify the consequences and values associated with the product's perceived attributes. Important attributes included low levels of fat, dryness, novelty, and special preparation requirements. Significant values included security, self-esteem, hedonism, tradition, and stimulation. Promoters of the product are advised to capitalize on consumers' interest in health and the health benefits of the meat in their advertising strategy. They can also address current barriers to consumption as indicated by negative, undesirable consequences (difficult and time-consuming to prepare) by promoting quick and easy ways of preparation, provision of ready-to-eat dishes and training.

Radder, Laetitia; Grunert, Klaus G.

2009-01-01

242

Crystalline fibers of metal-peptide double ladders.  

Science.gov (United States)

Despite remarkable progress in the field of MOFs, structures based on long-flexible organic linkers are scarce and the majority of such materials rely on rigid linkers. In this work, crystals of a new metal-organic double ladder (MODL) are obtained by linking a pentapeptide (NH2-Glu-pCO2Phe-pCO2Phe-Ala-Gly-OH) with cadmium acetate to produce a Cd(2-pyrrolidone-pCO2Phe-pCO2Phe-Ala-Gly)(H2O)3 framework. SEM and TEM analyses show the fibrous nature of the crystals and show that the infinite cadmium oxide rod secondary building units (SBUs) are aligned with the longitudinal axis of the nanofibers. PMID:24256366

Peri, Dani; Ciston, Jim; Gándara, Felipe; Zhao, Yingbo; Yaghi, Omar M

2013-12-16

243

Excitations in a perfect magnetized quantum spin ladder  

Science.gov (United States)

The strong-leg S=1/2 Heisenberg spin ladder system C7(D10N)2CuBr4 is investigated in applied magnetic fields using inelastic neutron scattering anf DMRG calculations. The spectrum in the high-field Tomonaga-Luttinger spin liquid phase is found to be qualitatively different from that in the low-field spin gap phase. In the former, numerous spectral featrures, including incommensurate excitations and multi-spinon continua are identified. In contrast, the latter is dominated by long-lived magnon excitations and two-magnon bound states [1]. An unprecedented quantitive agreement between experiment and numerical claculations is achieved.[4pt] [1] D. Schmidiger, P. Bouillot, S. Muhlbauer, S. Gvasaliya, C. Kollath, T. Giamarchi, A. Zheludev, Phys. Rev. Lett. 108, 167201 (2012).

Zheludev, Andrey; Schmidiger, David; Muehlbauer, Sebastian; Severian, Gvasaliya; Bouillot, Pierre; Kollath, Corinna; Giamarchi, Thierry; Guidi, Tatiana; Bewley, Robert; Ehlers, Georg

2013-03-01

244

Magnetization Plateaux in N-Leg Spin Ladders  

CERN Document Server

In this paper we continue and extend our earlier study [cond-mat/9707090] of plateaux in magnetization curves of antiferromagnetic Heisenberg spin-1/2 ladders. We first review a bosonic field-theoretical formulation of a single XXZ-chain in the presence of a magnetic field, which is then used for an Abelian bosonization analysis of N weakly coupled chains. Predictions for the universality classes of the phase transitions at the plateaux boundaries are obtained in addition to a quantization condition for the value of the magnetization on a plateau. These results are complemented by and checked against strong-coupling expansions. Finally, we analyze the strong-coupling effective Hamiltonian for an odd number N of cylindrically coupled chains numerically. For N = 3 we explicitly observe a spin-gap with a massive spinon-type fundamental excitation and obtain indications that this gap probably survives the limit N to infinity.

Cabra, D C; Pujol, P

1998-01-01

245

Performance of Long Ladders for the LHCb Silicon Tracker  

CERN Document Server

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

246

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

247

Breathers in Josephson junction ladders resonances and electromagnetic waves spectroscopy  

CERN Multimedia

We present a theoretical study of the resonant interaction between dynamical localized states (discrete breathers) and linear electromagnetic excitations (EEs) 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 can be mapped to the spectrum of EEs that has been derived analytically and numerically. Using an improved analysis of the breather tail, a spectroscopy of the EEs is developed. The nature of breather instability driven by localized EEs is established.

Miroshnichenko, A E; Fistul, M V; Zolotaryuk, Y; Page, J B

2001-01-01

248

A Study of the Gluon Ladder in Diffractive Processes  

CERN Document Server

The solution to the non-forward BFKL equation in the Leading Logarithmic approximation is expressed in terms of a sum of iterations of its kernel directly in transverse momentum and rapidity space. Several studies of the non-forward solution are performed both at the level of the gluon Green's function and for a toy cross-section, including an analysis of the diffusion properties as found in this approach. The method developed in this paper allows for a direct inspection of the momenta in the BFKL ladder, and can be applied to solving the non-forward BFKL equation to next-to-leading logarithmic accuracy, when the corresponding kernel is available.

Andersen, J R; Andersen, Jeppe R.; Vera, Agustin Sabio

2005-01-01

249

Inelastic Neutron Scattering from the Spin Ladder Compound (VO)2P2O7  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.; Barnes, T.; Brody, J.; Johnson, J. W.

1994-01-01

250

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

251

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.

2008-08-01

252

Fish passes  

…may be over 5m/sec, since the maximum swimming speed and endurance of a fish normally increases with increasing length of the fish. Conversely, small fish such as first year returning sea trout of only 0.3m in length may have difficulty in ascending jets of water at more than 3.5m/sec. Another factor…

253

Fish passes  

…water velocity may be over 5m/sec, since the maximum swimming speed and endurance of a fish normally increases with increasing length of the fish. Conversely, small fish such as first year returning sea trout of only 0.3m in length may have difficulty in ascending jets of water at more than 3.5m/sec. Another…

254

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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, Frederic; Stafford, Charles; Capponi, Sylvain

1997-01-01

255

Re-Entrant Quantum Phase Transitions in Antiferromagnetic Spin-1 Ladders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In response to recent chemical attempts to construct higher-spin ladder materials from organic polyradicals, we study the ground-state properties of a wide class of antiferromagnetic spin-1 ladders. Employing various numerical tools, we reveal the rich phase diagram and correct a preceding nonlinear-sigma-model prediction. A variational analysis well interprets the phase competition with particular emphasis on the {\\it re-entrant phase boundary} as a function of the rung int...

Yamamoto, Shoji; Sakai, Toru; Koga, Akihisa

2002-01-01

256

Adding rungs to the exporting ladder: plant-level exporting dynamics and total factor productivity growth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use panel data on Mexican manufacturing plants to study the dynamics of plant-level exporting activity at both the extensive and the intensive margins and the connection between exporting dynamics and plant-level total factor productivity growth. We find that exporting activity has a ladder structure. Most entries and exits take place at the bottom of the ladder and account for a small share of gross, industry-level changes in exports, employment, output, and productivity. The dynamics at ...

Voicu, Alexandru

2008-01-01

257

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

258

The Marijuana Ladder: Measuring motivation to change marijuana use in incarcerated adolescents  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The purpose of this study was to determine if a modified version of the Contemplation Ladder, a measure of motivation to change marijuana use among incarcerated adolescents (Marijuana Ladder; ML), was related to marijuana use and treatment engagement. Participants (N = 122) in this study were all incarcerated at a state juvenile correctional facility in the Northeast. Adolescents were assessed at the beginning of their incarceration, 2 months into their incarceration, and 3 months after their...

2006-01-01

259

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

260

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

 
 
 
 
261

Quasienergy resonance in a dynamic Wannier-Stark ladder  

Science.gov (United States)

We examine a continuum effect of a dynamic Wannier-Stark ladder (DWSL) driven by a cw laser—with Fac and ? as amplitude and frequency, respectively—by means of an excess density of states (DOS), ?(ex)(E), closely related to the more familiar DOS and proportional to the lifetime of a resonance state. It is mathematically shown that ?(ex)(E) is governed by three different physical mechanisms: the single-channel resonance mechanism, the multichannel nonresonance mechanism, and the multichannel resonance mechanism. The last mechanism becomes more important with the increase in Fac. The effect of the interchannel interaction is maximized when the ratio of a Bloch frequency to ?, represented as ?, equals unity. In the actual calculations based on the R-matrix Floquet theory, it is revealed that, in a large-Fac region, ?(ex)(E) for ?=1 shows a complicated spectral structure composed of a couple of newly growing peaks, in contrast to ?(ex)(E) for ?=3 which just shows a monotonic change of a single spectral peak. It is speculated that the pronounced feature of the former spectra is attributed to the Fano-like multichannel resonance mechanism, whereas the feature of the latter case is attributed to the multichannel nonresonance mechanism.

Nemoto, Yuya; Hino, Ken-ichi; Maeshima, Nobuya

2013-05-01

262

Strength and stiffness characteristics of steel ladder-type cable trays  

International Nuclear Information System (INIS)

Ladder-type cable trays identical with the as-built are generally tested to establish their strength and stiffness characteristics. Test data for systems in operating plants, however, may be either nonexistent, incomplete, not directly applicable to the as-built configuration, or cannot be acquired through addition testing due to discontinuation of the as-built hardware. In these instances, derivation of the stiffness and strength characteristics using analysis can provide time and cost savings. Most test lateral load-deformation curves exhibit small deviations from the corresponding initial ''tangent modulus'' curves over the load range for which the component is designed. Accordingly, linear Vierendeel truss models are applicable to their stiffness determination. The shear lag dependence of siderail stiffness values for the truss model are investigated in detail using finite element solutions. Equations are developed representing the Vierendeel truss as an equivalent shear-flexure beam to arrive at a theoretical load-deformation expression dependent on the system parameters. These results are compared with test data to verify the model

1984-09-01

263

Petri net to ladder logic diagram converter and a batch process simulation  

Directory of Open Access Journals (Sweden)

Full Text Available Discrete-event dynamic systems (DEDS are characterized by a set of states which the system can take, and by the set of asynchronous events that cause the state changes at discrete time points. Programmable logic controllers (PLCs are still important special purpose computers used to automate the DEDS in industry. Ladder logic diagrams (LLDs are still the most popular graphical programming tools of the PLCs; but the major problem is that programming is done heuristically and the LLDs are difficult to be used for both analysis and performance evaluation. Petri nets (PNs are nowadays the most effective modeling environment for both the design and implementation of DEDS. This paper proposes a PN to LLD conversion tool, used for graphical editing of a PN net model of a DEDS controller and for converting this PN into the equivalent LLD for programming a PLC. The conversion algorithm is presented, considering many types of transitions, places, and arcs with generality that many types of PNs can be considered. This paper also presents a simulation of a batch process, on a personal computer from one side, interfaced with a real PLC from the other side, that is programmed using a LLD obtained from the conversion of a suitable PN model using the proposed conversion tool. Compared with a LDD got heuristically, the LLD got from a PN conversion is simpler, understandable, and meeting all the characteristics obtained from the PN analysis.

Mostafa M. Gomaa

2011-02-01

264

Experiments on ladders reveal a complex interplay between a spin-gapped normal state and superconductivity  

International Nuclear Information System (INIS)

In recent years, the study of ladder materials has developed into a well-established area of research within the general context of strongly correlated electrons. This effort has been triggered by an unusual cross-fertilization between theory and experiments. In this paper, the main experimental results obtained in the context of ladders are reviewed from the perspective of a theorist. Emphasis is given to the many similarities between the two-dimensional high-Tc cuprates and the two-leg ladder compounds, including Sr14-xCaxCu24O41 ([14-24-41]) which has a superconducting phase at high pressure and a small hole density. Examples of these similarities include regimes of linear resistivity versus temperature in metallic ladders and a normal state with spin gap or pseudogap characteristics. It is remarked that the ladder [14-24-41] is the first superconducting Cu oxide material with a non-square-lattice layered arrangement, and certainly much can be learned from a careful analysis of this compound. A short summary of the main theoretical developments in this field is also included, as well as a brief description of the properties of non-Cu-oxide ladders. Suggestions by the author on possible experiments are described in the text. Overall, it is concluded that the enormous experimental effort carried out on ladders has already unveiled quite challenging and interesting physics that adds to the rich behaviour of electrons in transition metal-oxides, and in addition contributes to the understanding of the two-dimensional cuprates. However, considerable work still needs to be carried out to fully understand the interplay between charge and spin degrees of freedom in these materials. (author)

1999-11-01

265

Benefits of fish passage and protection measures at hydroelectric projects  

Energy Technology Data Exchange (ETDEWEB)

The US Department of Energy`s Hydropower Program is engaged in a multi-year study of the costs and benefits of environmental mitigation measures at nonfederal hydroelectric power plants. An initial report (Volume 1) reviewed and surveyed the status of mitigation methods for fish passage, instream flows, and water quality; this paper focuses on the fish passage/protection aspects of the study. Fish ladders were found to be the most common means of passing fish upstream; elevators/lifts were less common, but their use appears to be increasing. A variety of mitigative measures is employed to prevent fish from being drawn into turbine intakes, including spill flows, narrow-mesh intake screens, angled bar racks, and lightor sound-based guidance measures. Performance monitoring and detailed, quantifiable performance criteria were frequently lacking at non-federal hydroelectric projects. Volume 2 considers the benefits and costs of fish passage and protection measures, as illustrated by case studies for which performance monitoring has been conducted. The report estimates the effectiveness of particular measures, the consequent impacts on the fish populations that are being maintained or restored, and the resulting use and non-use values of the maintained or restored fish populations.

Cada, G.F.; Jones, D.W.

1993-06-01

266

Fish Aware: Textile Design as an Environmental Intervention. How textile design can be used as a medium to raise awareness of overfishing; and influence the pattern of fish consumption.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis is a cooperation between WWF Finland and Makia Clothing, to create textile print designs within in a campaign context. The study specifically addresses the issue of overfishing, with the purpose to raise awareness and better sustainable practices within consumers and companies. Unsustainability has brought design and designers to a position where they have to think and design with an uncertain future in mind. There is no steady route to success or path to follow. Econom...

Barclay, Paula

2013-01-01

267

Stocking fish  

fish: A GUIDE FOR fishery owners AND anglers For more copies of this booklet please contact: National Coarse Fisheries Centre Environment Agency Arthur Drive Hoo Farm Industrial Estate Worcester Road Kidderminster Worcs DY11 7RA Tel: 01562 68975 Fax: 01562 69477 1 Stocking fish: a guide for fishery…

268

Fish oil  

Science.gov (United States)

... the intestine. There is some evidence that using vitamin B12 along with fish oil might boost their ability to lower cholesterol. ... vitamin E levels. Researchers aren't sure whether fish oil keeps vitamin E from being absorbed from food or whether ...

269

Hood River Pelton Ladder Studies : Annual Report 1995.  

Energy Technology Data Exchange (ETDEWEB)

Data collected from this program will provide the baseline information needed to (1) evaluate various management options for implementing the Hood River Production Plan and (2) determine any post-project impacts the Hood River Production Plan has on indigenous populations of resident fish.

Olsen, Erik A.; French, Rod A.; Ritchey, Alan D.

1996-09-01

270

Hood River Pelton Ladder evaluation studies: Annual report 1995; ANNUAL  

International Nuclear Information System (INIS)

Data collected from this program will provide the baseline information needed to (1) evaluate various management options for implementing the Hood River Production Plan and (2) determine any post-project impacts the Hood River Production Plan has on indigenous populations of resident fish

1996-01-01

271

Experiments on Ladders Reveal a Complex Interplay between a Spin-Gapped Normal State and Superconductivity  

CERN Document Server

In recent years, the study of ladder materials has developed into a well-established area of research within the general context of Strongly Correlated Electrons. This effort has been triggered by an unusual cross-fertilization between theory and experiments. In this paper, the main experimental results obtained in the context of ladders are reviewed from the perspective of a theorist. Emphasis is given to the many similarities between the two-dimensional high-$\\rm T_c$ cuprates and the two-leg ladder compounds, including Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$ (14-24-41) which has a superconducting phase at high pressure and a small hole density. Examples of these similarities include regimes of linear resistivity vs temperature in metallic ladders and a normal state with spin-gap or pseudogap characteristics. Some controversial results in this context are also discussed. It is remarked that the ladder 14-24-41 is the first superconducting copper-oxide material with a non-square-lattice layered arrangement, and c...

Dagotto, E

1999-01-01

272

Doped spin ladders under magnetic field; Echelles de spins dopees sous champ magnetique  

Energy Technology Data Exchange (ETDEWEB)

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)

Roux, G

2007-07-15

273

Quantum Entanglement and Thermal Reduced Density Matrices in Fermion and Spin Systems on Ladders  

CERN Document Server

Numerical studies of the reduced density matrix of a gapped spin-1/2 Heisenberg antiferromagnet on a two-leg ladder find that it has the same form as the Gibbs density matrix of a gapless spin-1/2 Heisenberg antiferromagnetic chain at a finite temperature determined by the spin gap of the ladder.\\cite{Poilblanc2010} We investigate this interesting result by considering a model of free fermions on a two-leg ladder (gapped by the inter-chain tunneling operator) and in spin systems on a ladder with a gapped ground state using exact solutions and several controlled approximations. We calculate the reduced density matrix and the entanglement entropy for a leg of the ladder (i.e. cut made between the chains). In the fermionic system we find the exact form of the reduced density matrix for one of the chains and determine the entanglement spectrum explicitly. In the case of the spin system, we consider the strong coupling limit by using perturbation theory and get the reduced density matrix by the Schmidt decompositi...

Chen, Xiao

2013-01-01

274

Characteristics of ITO electrode grown by linear facing target sputtering with ladder type magnetic arrangement for organic light emitting diodes  

International Nuclear Information System (INIS)

The preparation and characteristics of indium tin oxide (ITO) electrodes grown using a specially designed linear facing target sputtering (LFTS) system with a ladder type magnet arrangement for organic light emitting diodes (OLED) are described. It was found that the electrical and optical properties of the ITO electrode were critically dependent on the Ar/O2 flow ratio, while its structural and surface properties remained fairly constant regardless of the Ar/O2 flow ratio, due to the low substrate temperature during the plasma damage-free sputtering. Under the optimized conditions, we obtained an ITO electrode with the lowest sheet resistance of 39.4 ?/sq and high transmittance of 90.1% (550 nm wavelength) at room temperature. This suggests that LFTS is a promising low temperature and plasma damage free sputtering technology for preparing high-quality ITO electrodes for OLEDs and flexible OLEDs at room temperature.

2009-05-29

275

Damped Rabi wavepacket oscillations and damping time in correlated random ladders  

Science.gov (United States)

In this work, we follow the time evolution of an initially localized one-electron wavepacket in a random ladder model with correlated diagonal disorder. Weak localization of the eigenstates is anticipated for antisymmetric cross-correlations with every base pair having the same average energy. We show that the wavepacket width develops damped Rabi-like oscillations after reaching the ladder's borders. The Rabi-like oscillations are shown to originate from the interference between neighboring energy eigenstates, while its damping is associated with a destructive interference due to the random scattering in the underlying random potential. The typical damping time td is estimated as a function of the ladder size N and shown to increase as td?Nz with z=0.62(4). The strong localization in the absence of antisymmetric cross-correlations suppresses the oscillations.

Caetano, R. A.; Lyra, M. L.; Schulz, P. A.

2013-12-01

276

Systematic NMR studies of high- T c and two-leg spin-ladder systems  

Science.gov (United States)

We review systematic NMR studies on underdoped high- T c cuprates and two-leg spin-ladder systems, focusing on their spin gap and dynamics. The pressure-induced superconductivity was discovered in Sr 14- xCa xCu 24O 41 comprising the quasi-one-dimensional S = ½ two-leg spin-ladder Cu 2O 3 planes. Remarkably, the new parent cuprate is the Mott insulator with the spin gap in contrast to the antiferromagnetic (AF) insulator for the high- T c cuprates. From the Cu-NMR results in the ladder Cu 2O 3 plane on single crystals Sr 14- xCa xCu 24O 41 with x = 9 (hereafter denoted as Ca9) and x = 11.5 (Ca11.5), it is shown that the spin gap, ? = 510K in the Sr14 is significantly reduced upon isovalent Ca substitution, but its magnitude remains nearly constant with ? = 270 and 280K for the Ca9 and Ca11.5, respectively. In T range of T ? ?, the spin dynamics in carrier-doped two-leg spin-ladder systems are characterized by the behaviour similar to the S = ½ 1D Heisenberg system. By contrast, the transport property shares a common feature, i.e, due to the spin-gap opening the charge transport is confined in the 2D CuO 2 plane for underdoped high- T c, cuprates and in the quasi-1 D ladder for spin-ladder compounds.

Kitaoka, Y.; Magishi, K.; Matsumoto, S.; Ishida, K.; Ohsugi, S.; Asayama, K.; Uehara, M.; Nagata, T.; Akimitsu, J.

1998-01-01

277

Multiple Robotic Fish’s Target Search and Cooperative Hunting Strategies  

Directory of Open Access Journals (Sweden)

Full Text Available Multi-robotic fish’s cooperative hunting is through that the robotic fish groups’ collaboration and against, ultimately achieves the purpose of encirclement target; there is important significance to realize security of the underwater group. This paper studied the problem of multi-robotic fish’s target search and cooperative hunting, discussed on the multi-robotic fish’s group size, conditions of search target and hunting successful, conditions of failure successfully. Proposed the partition global search strategy, hunt-robotic fish use a hunting strategy that based on dynamic surrounding point, and designed intelligent escape strategy for invasion-robotic fish. A simulation experience is conducted to verify the hunting strategy and escape strategy that proposed in this paper, and the results show that on the basic of fast search to the target, multi-robotic fishes can achieve hunting task efficiently, but also reflects the game against behavior between the intruders and hunters.     Keywords:

Da Lin

2013-07-01

278

Evaluation of Juvenile Fish Bypass and Adult Fish Passage Facilities at Water Diversions on the Umatilla River; 1994 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

We report on our progress from October 1993 through September 1994 in evaluating juvenile salmonid bypass facilities and juvenile salmonid passage through ladder facilities, and investigating passage conditions for juvenile fish at diversion dam facilities on the lower Umatilla River in northeastern Oregon. We also report on our progress in evaluating adult salmonid passage at and between dams on the lower Umatilla River and upriver migration using radio telemetry. Two principal studies are also included. Report A (ODFW): To evaluate the juvenile salmonid bypass facilities a Feed and Furnish canals, juvenile salmonid passage through fish ladders at Stanfield, Feed Canal, Westland, and Three Mile Falls dams, and the juvenile salmonid trap and haul procedures at Westland Canal. To investigate passage conditions at all passage facilities. Report B (CTUIR): To examine the passage of adult salmonids past diversions in the lower Umatilla River and their movement in the upper river after transport, using radio telemetry, and to assess factors for successful homing. These studies are 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.

1995-01-01

279

Linearized coherent states for Hamiltonian systems with two equidistant ladder spectra  

Science.gov (United States)

A simple way to construct exactly solvable Hamiltonians whose spectra contain two equidistant ladders, one finite and another infinite, appears when applying supersymmetric quantum mechanics to the harmonic oscillator. Some of those supersymmetric partners have third order differential ladder operators, although the order of the transformation is higher than one. In this work the linearized coherent states for these specific Hamiltonians are studied. To each SUSY partner Hamiltonian corresponds two families of linearized coherent states: one inside the subspace associated with the isospectral part of the spectrum and another one in the finite subspace generated by the states inserted through the SUSY technique.

Bermudez, D.; Contreras-Astorga, A.; Fernández C, D. J.

2014-05-01

280

Zero energy Majorana modes in spin ladders and a possible realization of the Kitaev model  

CERN Multimedia

We show that in double-chain Mott insulators (ladders), disordered alternating ionic potentials may locally destroy coherence of magnetic excitations and lead to the appearance of spontaneously dimerized islands inside the Haldane spin-liquid phase. We argue that a boundary between the dimerized and Haldane phases of a spin-1/2 ladder supports a localized zero-energy Majorana fermion mode. Based on these findings we suggest a realization of a generalized Kitaev model where Majorana fermions can propagate in more than one dimension.

Nersesyan, A A

2011-01-01

 
 
 
 
281

Can an ethnic group climb up from the bottom of the ladder?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Studies in the US have shown that black immigrants have remained at the bottom of the wage ladder and that other groups of immigrants have overtaken them over time. The goal of this research is to determine whether a specific group of immigrants can displace a group at the bottom of the ladder. We use Israeli data to compare two ethnic groups: Israeli Arabs and Ethiopian immigrants. Israeli Arabs were considered to be the least successful ethnic group in the Israeli labor market until they we...

Epstein, Gil S.; Siniver, Erez

2012-01-01

282

Search for quantum dimer phases and transitions in a frustrated spin ladder  

CERN Multimedia

A two-leg spin-1/2 ladder with diagonal interactions is investigated numerically. We focus our attention on the possibility of columnar dimer phase, which was recently predicted based on a reformulated bosonization theory. By using density matrix renormalization group technique and exact diagonalization method, we calculate columnar dimer order parameter, spin correlation on a rung, string order parameters, and scaled excitation gaps. Carefully using various finite-size scaling techniques, our results show no support for the existence of columnar dimer phase in the spin ladder under consideration.

Hung, H H; Chen, Y C; Yang, M F; Hung, Hsiang-Hsuan; Gong, Chang-De; Chen, Yung-Chung; Yang, Min-Fong

2006-01-01

283

Bond-Alternating Antiferromagnetic S = 1/2 Heisenberg Ladder with Ferromagnetic Diagonal Coupling  

International Nuclear Information System (INIS)

Using the density matrix renormalization group method, we determine the phase diagram of a frustrated bond-alternating S = 1/2 Heisenberg ladder with ferro-antiferromagnetic couplings at zero temperature. With the interactions between spins along the rungs set, we identify three spin-gapped phases (the Haldane phase, the singlet phase and the dimer phase) in the whole parameter range. The analysis of our data shows that two-leg spin bond-alternating ladders have a rich phase diagram if both rung and diagonal couplings are taken into account

2009-12-01

284

Penentration of dynamic localized states in DC-driven Josephson junction ladders by discrete jumps  

CERN Multimedia

We give a theoretical study of unusual resistive (dynamic) localized states in anisotropic Josephson junction ladders, driven by a DC current at one edge. These states comprise nonlinearly coupled rotating Josephson phases in adjacent cells, and with increasing current they are found to expand into neighboring cells by a sequence of sudden jumps. We argue that the jumps arise from instabilities in the ladder's superconducting part, and our analytic expressions for the peculiar voltage (rotational frequency) ratios and I-V curves are in very good agreement with direct numerical simulations.

Fistul, M V

2001-01-01

285

About Fish  

Science.gov (United States)

This activity introduces students to an animal that is to be the subject of much experimentation by them. Because most fish have a relatively simple form and exhibit a wide variety of colors and patterns, they prove to be an excellent animal for experimental study of many aspects of coloration. The body of the lesson is devoted to a description and discussion of the external structure of fish.

Ipsen, David; Gillfillan, Gretchen L.; Judy Diamond (Revised New Edition); Judy Scotchmoor (Revised New Edition); Stebbins, Robert

2008-04-01

286

Umatilla Basin Fish Facilities Operation & Maintenance : Annual Report Fiscal Year 2008.  

Energy Technology Data Exchange (ETDEWEB)

Westland Irrigation District, as contractor to Bonneville Power Administration, and West Extension Irrigation District, as subcontractor to Westland, provide labor, equipment, and material necessary for the operation, care, and maintenance of fish facilities on the Umatilla River. Westland Irrigation District is the contractor of record. Job sites that are covered: Three Mile Right, Three Mile Left, Three Mile Adult Spawning, WEID Sampling Facility, Maxwell Screen Site, Westland Screen Site/Ladder/Juvenile Sampling Facility, Feed Canal Ladder/Screen Site, Stanfield Ladder/Screen Site, Minthorn Holding Facility, Thornhollow Acclimation Site, Imeques Acclimation Site, Pendleton Acclimation Site, and South Fork Walla Walla Spawning Facility. O & M personnel coordinate with the Confederated Tribes of the Umatilla Indian Reservation (CTUIR) and Oregon Department of Fish and Wildlife (ODFW) personnel in performing tasks under this contract including scheduling of trap and haul, sampling, acclimation site maintenance, and other related activities as needed. The input from ODFW biologists Bill Duke and Ken Loffink, and CTUIR biologist Preston Bronson is indispensable to the success of the project, and is gratefully acknowledged. All tasks associated with the project were successfully completed during the fiscal year 2008 work period of October, 2007 through September, 2008. The project provides operations and maintenance throughout the year on five fish screen sites with a total of thirty-four rotating drum-screens, and four fish ladders in the Umatilla River Basin; additionally, periodic operations and maintenance is performed at holding, acclimation, and spawning sites in the Basin. Three people are employed full-time to perform these tasks. The FY08 budget for this project was $492,405 and actual expenditures were $490,267.01. Selected work activities and concerns: (1) Feed Dam Passage Improvement Project - A project to improve fish passage over the short term at the Feed Canal Diversion Dam site (Umatilla River mile 28.7) was implemented with local U.S. Bureau of Reclamation field office personnel coordinating project activities. Operation and Maintenance Project personnel assisted with labor, materials, and equipment to ensure the project was completed as planned. Discussions are under way to determine feasible alternatives for longer term solutions to passage issues at the site. (2) Three Mile Right (east bank) Facilities - The pump for supplying water to the fish handling facility holding pond was reconstructed successfully to achieve the desired increase in flow output necessary when increased quantities of fish are present. (3) Fish Screen Rehab at Stanfield Canal Diversion - Working with the Washington Department of Fish and Wildlife screen shop personnel, three rotating drum screens at the Stanfield Canal diversion site (Umatilla River mile 33.3) were serviced and overhauled with new bearings, seals, paint, and reinforcing bars. Work was completed, and screens reinstalled prior to water diversions beginning in the spring. (4) O & M personnel performed daily, weekly, and monthly operations and maintenance duties at the screen and ladder sites including, but not limited to, desilting of mud and debris, lubrication of mechanical parts, replacement of screen seals and screen motor components, adjustment of ladder gates, removal of large trees and woody debris deposited during high river flow conditions, servicing of pumps and screens for fish handling operations and sampling studies, in addition to general site clean-up, vegetative control, and security. Crew members responded as needed during evenings and after-hours according to weather conditions, river flows, and fish passage facility needs.

Wick, Mike

2008-12-30

287

A Demonstration of Helping Adolescents with Mild Intellectual Disability Climb Ladders  

Science.gov (United States)

A research team at a vocational school in Singapore, catering mainly to students between the ages of 17-21 with mild intellectual disability, studied how to best address the challenge of enabling students to learn how to climb ladders (a skill necessary at many job placements). They documented the approach used and suggested extrapolations and…

Chan, Kok Hoe Anthony; Varahan, Jayashree Lakshmi; Loh, Peng Loong Daniel; Tan, Sey Ing

2011-01-01

288

Carbon isotope enrichment by retention of isotopic excitation selectivity in VV ladder climbing collisions  

International Nuclear Information System (INIS)

Initial isotopic excitation selectivity in cw CO_2 laser pumping of "1"2CH_3F and "1"3CH_3F is retained in upper vibrational states even after ladder climbing collisions. Reaction of these states with atomic bromine samples this non-equilibrium distribution and produces isotopically enriched product, CH_2FBr, with projected excellent energy efficiency. (orig.)

1980-11-15

289

A Twisted Ladder: Relating the Fe Superconductors to the High Tc Cuprates  

Energy Technology Data Exchange (ETDEWEB)

We construct a 2-leg ladder model of an Fe-pnictide superconductor and discuss its properties and relationship with the familiar 2-leg cuprate model. Our results suggest that the underlying pairing mechanism for the Fe-pnictide superconductors is similar to that for the cuprates.

Berg, E.

2010-05-26

290

Gravity-induced Wannier-Stark ladder in an optical lattice  

CERN Document Server

We discuss the dynamics of ultracold atoms in an optical potential accelerated by gravity. The positions and widths of the Wannier-Stark ladder of resonances are obtained as metastable states. The metastable Wannier-Bloch states oscillate in a single band with the Bloch period. The width of the resonance gives the rate transition to the continuum.

Zapata, J; Moore, M G; Meystre, P

2000-01-01

291

NMR study of spin ladder compound (CPA)2CuBr4  

Science.gov (United States)

We performed a nuclear magnetic resonance experiment on 1H in (CPA)2CuBr4 ( CPA=cyclopentylammonium) which is considered as two-leg spin ladder system antiferromagnetic compound. Applied field range up to 8.7 T covers the critical field Hc ( =1.7 T) where the energy gap disappears. In the field range HHc.

Sasaki, T.; Fujii, Y.; Kikuchi, H.; Chiba, M.; Yamamoto, Y.; Hori, H.

2007-03-01

292

R'enyi entropy of d-wave Bose metal phases on multi-leg ladders  

Science.gov (United States)

In recent years, much progress has been made toward understanding 2D Bose metal-type phases by accessing them through a series of controlled quasi-1D ladder studies [1]. Crucially, such quasi-1D descendants of these exotic phases are expected to have a number of gapless Luttinger modes, c, that grows with the width of the ladder. Therefore, characterizing scaling of the entanglement entropy has become an essential tool for establishing the existence of these phases, as it provides a direct measure of c. With density-matrix renormalization group (DMRG) methods, it is easy to calculate the entanglement entropy but the results converge prohibitively slowly as the ladder becomes wider. Here, we present results where we have calculated, using Variational Monte Carlo (VMC), the R'enyi entropy S2 for Gutzwiller-projected d-wave Bose metal (DBM) [2] trial wave functions on ladders, following the method employed in [3]. We compare with DMRG results (where they are available), and comment on what our findings mean for the ability of our trial wave functions to faithfully represent the DBM phase. [4pt] [1] D. N. Sheng et. al., PRB 78, 054520 (2008).[0pt] [2] O. I. Motrunich and M. P. A. Fisher, PRB 75, 235116 (2007).[0pt] [3] Y. Zhang et. al., PRL 107, 067202 (2011).

Garrison, James R.; Mishmash, Ryan V.; Fisher, Matthew P. A.

2012-02-01

293

Effects of aluminum trichloride and magnesium chloride on the synthesis of ladder polyphenylsilsesquioxane  

Directory of Open Access Journals (Sweden)

Full Text Available Ladder polyphenylsilsesquioxane (Ph-LPSQ has been synthesized at 80°C through the hydrolysis and condensation of phenyltrichlorosilane (PhSiCl3, with aluminum chloride (AlCl3 or magnesium chloride (MgCl2 as an assistant reactant. The Ph-LPSQ obtained has been characterized and analyzed by SEM, FTIR, TGA, 29Si NMR, and MALDI-TOF MS, and the effects of AlCl3and MgCl2on the structure regularity of Ph-LPSQ and the condensation polymerizationhavealso been studied. The results showed that Ph-LPSQ could be obtained in theAlCl3and MgCl2systems, respectively, but the experimental phenomena and results showed significant differences between the two systems. SEM observation revealed spherical Ph-LPSQ particles from the PhSiCl3/AlCl3system, but irregular and agglomerated Ph-LPSQ particles from the PhSiCl3/1.5(MgCl2 system. TGA, 29SiNMR, and MALDI-TOF MS indicated that the ladder structure of Ph-LPSQ from the PhSiCl3/1.5(MgCl2 system was more regular. Inthe PhSiCl3/AlCl3system, Al could be incorporated into the ladder chain structure through competing reactions between Si-O-Al and Si-O-Si, which slightly decreased the regularity of the ladder chain structure of Ph-LPSQ. Mechanistic analysis suggests that the presence of AlCl3or MgCl2in the hydrolysis and condensation system favors the intermolecular condensation of intermediate products of polyhydroxyl silanol to form a regular ladder structure.

Jiang Yunyun

2012-01-01

294

Pallet insertion glovebox/hood control ladder diagram. Final project report  

International Nuclear Information System (INIS)

The pallet insertion glovebox/hood (G/H) is a special confinement space that will be designed to allow for insertion of pallets into the Stacker/Retriever (S/R) area. The S/R a large vault that is kept at negative 1 inches w.c. relative to the atmosphere and is used for the safe storage of special nuclear material. The S/R system uses a vehicle to move the special nuclear material that are placed on the pallets from the storage bins to input/output (I/O) stations and vice versa. As the name suggest the I/O stations are used to place the material into the S/R vault or to remove material from the S/R vault. The pallets are specially designed structures that will hold certain numbers of the material containers in a safe configuration. To store additional material containers, there is a need to insert additional pallets in the SIR vault. Due to the presence of radioactive contamination and the fact that the vault must be kept at a negative pressure at all times, one of the several I/O stations will be modified so that pallets could be inserted into the S/R vault. The ventilation system for the S/R area is a dedicated system that recirculates nitrogen with less than 5% oxygen by volume throughout the area while exhausting small option of the nitrogen to keep the S/R at negative 1 inches w.c. relative to the atmosphere. The rooms surrounding the G/H and the S/R area are maintained at negative of 0.3 inches w.c. relative to the outside atmosphere. Both the G/H and the control system for the G/H will be designed such that the confinement requirements of the S/R and the G/H system will not be jeopardized. A ladder diagram will be developed to illustrate the control system

1995-01-01

295

Fish irradiation  

International Nuclear Information System (INIS)

Chub-mackerel was chosen for the study because they are the most common fish in Thailand. Preliminary investigations were conducted to determine the maximum radiation dose of gamma-rays by organoleptic tests. The samples were subjected to radiation at various doses up to 4 Mrad. Many experiments were conducted using other kinds of fish. The results showed that 1 Mrad would be the maximum acceptable dose for fish. Later, the influence of the radiation dose from 0.1-1 Mrad was studied in order to find the optimum acceptable dose for preservation of fish without off-flavour. For this purpose, the Hedonic scale was used. It was found that 0.2 and 0.5 Mrad gave the best result on Chub mackerel. The determinations of optimum dose, organoleptic, microbiological and trimethylamine content changes were done. The results showed that Chub mackerel irradiated at 0.2, 0.5 and 1 Mrad stored at 3"0C for 71 days were still acceptable, on the contrary the untreated samples were found unacceptable at 14 days. The trimethylamine increment was significantly higher in the untreated samples. At 15 days storage, trimethylamine in the non-irradiated Chub-mackerel was about 10 times higher than the irradiated ones. At 51 and 79 days storage, about 13 times higher in the control samples than the irradiated samples except 0.1 Mrad. Only 2 times higher was found for the 0.1 Mrad. The microbiological results showed that the irradiation above 0.2 Mrad gave favorable extension of shelf-life of fish

1970-01-01

296

DISEÑO DE UNA HERRAMIENTA DE EVALUACIÓN DEL DESEMPEÑO AMBIENTAL EN LAS GRANJAS PISCÍCOLAS / DESIGNING AN ASSESMENT TOOL OF ENVIROMENTAL PERFORMANCE INTO FISHING FARMS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish Con el objetivo de evaluar el desempeño ambiental de las empresas piscícolas, se diseñó y aplicó una herramienta basada en las listas de chequeo la cuál fue elaborada a partir de las recomendaciones dadas por la FAO en su código de conducta para una acuicultura responsable, en las guías de organizac [...] iones no gubernamentales que buscan el desarrollo de una acuicultura responsable y de modificaciones a las propuestas metodológicas de Vinatea (1999) y Leripio (2003). La aplicación por entrevista del cuestionario, acompañada de inspección ocular, permitió la recolección de valiosa información que calificó la actuación de las empresas piscícolas como crítica, pésima, aceptable, buena y excelente sostenibilidad. La información entregada a los planificadores del municipio en cuestión se convirtió en una guía para sus acciones a través de metas, estrategias y responsables a corto, mediano y largo plazo. Se comprobó que los aspectos negativos al desempeño ambiental son en su mayoría de rápida y económica solución, y que se requiere de trabajo proactivo entre municipio, corporación ambiental regional y productores. Se recomienda la aplicación de la herramienta en cuatro fases: evaluación preliminar, sensibilización y concienciación, autoevaluación y suministro de guías y recomendaciones para el buen desempeño ambiental. Abstract in english With the objective of evaluating the environmental performance of the fish farms facilities, it was designed and it applied a tool based on the check lists, which was elaborated of agreement with the recommendations given by the FAO in their Conduct Code for a Responsible Aquaculture, in the guides [...] of non government organizations (NGOs) that look for the development of a responsible aquaculture and of modifications to the methodological proposals of Vinatea (1999) and Leripio (2003). The application for interview of the questionnaire, accompanied by ocular inspection, allowed the gathering of valuable information that qualified the performance of the fish farms facilities like critic, terrible, acceptable, good and excellent sustainability. The report of results given to the municipal government became a guide for its actions through goals, strategies and responsible entities. It was certain that the negative aspects to the environmental acting are in their majority of quick and economic solution, and that it is required of work proactive among the municipal government, the regional environmental corporation and the producers. The application of the tool is recommended in four phases: preliminary evaluation, sensitization and understanding, autoevaluation and supply of guides and recommendations for the good environmental acting.

Sandra, Pardo; Héctor, Suárez; Paulo, Jardim-Manso; Eduardo, Soriano-Sierra.

297

Fish habitat mitigation measures for hydrotechnical projects  

International Nuclear Information System (INIS)

In recent years, the identification and mitigation of environmental impacts of hydrotechnical projects, particularly on fish and fish habitats, have become a major component of project planning and design. Potential impacts to fish and fish habitat may include increased fish mortality, decreased species diversity, and loss or decreases in fish production due to loss of habitat or alteration of its suitability. These impacts arise from flooding of riverine habitat, alteration of flow quantity and distribution, changes in morphology, and alteration of water quality, including suspended sediments, temperature, dissolved oxygen, and mercury. The results of a study for the Canadian Federal Department of Fisheries and Oceans Central and Arctic Region, examining fish habitat mitigation techniques for their applicability to hydrotechnical projects in Canada are summarized. The requirements for achievement and verification of the no net loss policy for a project are discussed. 10 refs., 2 tabs

1992-05-27

298

Fish gelatin.  

Science.gov (United States)

Gelatin is a multifunctional ingredient used in foods, pharmaceuticals, cosmetics, and photographic films as a gelling agent, stabilizer, thickener, emulsifier, and film former. As a thermoreversible hydrocolloid with a narrower gap between its melting and gelling temperatures, both of which are below human body temperature, gelatin provides unique advantages over carbohydrate-based gelling agents. Gelatin is mostly produced from pig skin, and cattle hides and bones. Some alternative raw materials have recently gained attention from both researchers and the industry not just because they overcome religious concerns shared by Jews and Muslims but also because they provide, in some cases, technological advantages over mammalian gelatins. Fish skins from a number of fish species are among the other sources that have been comprehensively studied as sources for gelatin production. Fish skins have a significant potential for the production of high-quality gelatin with different melting and gelling temperatures over a much wider range than mammalian gelatins, yet still have a sufficiently high gel strength and viscosity. Gelatin quality is industrially determined by gel strength, viscosity, melting or gelling temperatures, the water content, and microbiological safety. For gelatin manufacturers, yield from a particular raw material is also important. Recent experimental studies have shown that these quality parameters vary greatly depending on the biochemical characteristics of the raw materials, the manufacturing processes applied, and the experimental settings used for quality control tests. In this review, the gelatin quality achieved from different fish species is reviewed along with the experimental procedures used to determine gelatin quality. In addition, the chemical structure of collagen and gelatin, the collagen-gelatin conversion, the gelation process, and the gelatin market are discussed. PMID:20691955

Boran, Gokhan; Regenstein, Joe M

2010-01-01

299

Fish hemoglobins  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Vertebrate hemoglobin, contained in erythrocytes, is a globular protein with a quaternary structure composed of 4 globin chains (2 alpha and 2 beta) and a prosthetic group named heme bound to each one. Having myoglobin as an ancestor, hemoglobin acquired the capacity to respond to chemical stimuli that modulate its function according to tissue requirements for oxygen. Fish are generally submitted to spatial and temporal O2 variations and have developed anatomical, physiological and biochemica...

2007-01-01

300

Minibands and Wannier-Stark ladders in semiconductor superlattices studied by infrared spectroscopy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english We review the basic features of interminiband absorption in superlattices, focussing on the joint density of states, the oscillator strength and the associated sum rule. Then we will discuss infrared spectroscopic studies under application of an electric field. With a field in the plane of the layer [...] s, a hot-electron distribution can be generated. Using the temperature dependence of the interminiband absorption, energy loss and relaxation rates can be determined. A vertical electric field leads to negative differential resistance, domain formation and the break-up of the minibands into Wannier- Stark ladders. We will present experiments showing the formation of interpenetrating Wannier- Stark ladders in the continuum, which are strongly coupled by Zener resonances. This is the first time to correlate transport and infrared absorption in a biased superlattice.

M., Helm; W., Hilber; G., Strasser; R., DeMeester; F. M., Peeters.

 
 
 
 
301

Population transfer in the Na s-p Rydberg ladder by a chirped microwave pulse  

International Nuclear Information System (INIS)

While quantum defects of nl Rydberg states of Na with l?2 are nearly equal to zero, the quantum defects of ns and np states of Na are quite large due to the finite size of its ionic core. Since the Na ns and np states are energetically isolated from the higher angular momentum states of the same n, we can think of the Na ns and np Rydberg states as a specific example of a simple multilevel ladder system consisting of only alternating s and p angular momentum states. Here we report that population transfer in the Na s-p Rydberg ladder can be effectively achieved using a frequency-chirped microwave pulse, which couples only s and p states under suitable conditions.

2011-12-01

302

Staggered-Ladder Quasienergy Spectra for Generic Quasimomentum and Quantum-Dynamical Manifestations  

CERN Document Server

A new kind of regular quasienergy (Floquet) spectrum is found for the generalized kicked particle under quantum-resonance conditions at generic quasimomentum, a quantity most relevant in atom-optics experimental realizations of kicked-rotor systems. The new non-Poisson regular spectrum has the structure of a staggered ladder, i.e., it is the superposition of a finite number of ladder subspectra all having the same spacing, which is independent of the nonintegrability of the system. This spectral structure is shown to have distinct quantum-dynamical manifestations: A suppression of quantum resonances and a novel type of dynamical localization characterized by unique features such as traveling-wave components in the time evolution. These phenomena are found to be robust under small variations of the quasimomentum and should therefore be experimentally observable using Bose-Einstein condensates with sufficiently small quasimomentum width.

Dana, Itzhack

2013-01-01

303

Majorana fermions and multiple topological phase transition in Kitaev ladder topological superconductors  

Science.gov (United States)

Motivated by the InSb nanowire superconductor system, we investigate a system where one-dimensional topological superconductors are placed in parallel. It would be simulated well by a ladder of the Kitaev chains. The system undergoes multiple topological phase transitions, where the number of Majorana fermions changes as a function of the interchain superconducting pairings. We analytically determine the topological phase diagram by explicitly calculating the topological number and the band structure. They show even-odd effects with respect to the number of legs of the ladder. When the relative phase between the inter- and intrachain superconducting pairings is 0 or ?, the system belongs to the class BDI characterized by the Z index, and otherwise it belongs to the class D characterized by the Z2 index. This topological class change would be caused by applying the Josephson current or an external magnetic field, and could be observed by measuring the zero-bias differential conductance.

Wakatsuki, Ryohei; Ezawa, Motohiko; Nagaosa, Naoto

2014-05-01

304

Non-perturbative effective field theory for two-leg antiferromagnetic spin ladders  

CERN Document Server

We study the long wavelength limit of a spin 1/2 Heisenberg antiferromagnetic two-leg ladder, treating the interchain coupling in a non-perturbative way. We perform a mean field analysis and then include exactly the fluctuations. This allows for a discussion of the phase diagram of the system and provides an effective field theory for the low energy excitations. The coset fermionic Lagrangian obtained corresponds to a perturbed SU(4)_1/U(1) Conformal Field Theory (CFT). This effective theory is naturally embedded in a SU(2)_2 x Z_2 CFT, where perturbations are easily identified in terms of conformal operators in the two sectors. Crossed and zig-zag ladders are also discussed using the same approach.

Cabra, D C; Rossini, G L

2001-01-01

305

Structure and transport properties of spin ladder cuprate thin films synthesized by molecular beam epitaxy  

International Nuclear Information System (INIS)

Thin films of new compounds belonging to the (Sr,Ca)-Cu-O system have been synthesized using Molecular Beam Epitaxy (MBE). Their typical composition is (Sr,Ca)Cu2O3. The growth conditions have been optimized on two different substrates, MgO (100) and SrTiO3 (100). The structure was determined by high-resolution electron microscopy (HRTEM) and X-ray diffraction measurements on a four-circle diffractometer. Spin ladders Cu2O3 planes are clearly identified on HRTEM micrographs. The c axis stacking of the ladder planes provides various sites for Sr, Ca and O and it could explain the wide range of accessible of doping in these compounds. At high hole-doping levels induced by field effect, superconductive transitions are observed, in the nominally insulating material, the maximum transition temperature Tc being 14 K. (authors)

2002-01-01

306

From Spin Ladders to the 2-d O(3) Model at Non-Zero Density  

CERN Document Server

The numerical simulation of various field theories at non-zero chemical potential suffers from severe complex action problems. In particular, QCD at non-zero quark density can presently not be simulated for that reason. A similar complex action problem arises in the 2-d O(3) model -- a toy model for QCD. Here we construct the 2-d O(3) model at non-zero density via dimensional reduction of an antiferromagnetic quantum spin ladder in a magnetic field. The complex action problem of the 2-d O(3) model manifests itself as a sign problem of the ladder system. This sign problem is solved completely with a meron-cluster algorithm.

Chandrasekharan, S; Wiese, U J

2002-01-01

307

Tunable Hybridization at Mid Zone and Anomalous Bloch-Zener Oscillations in Optical Waveguide Ladders  

CERN Document Server

We have studied the optical oscillation and tunneling of light waves in optical waveguide ladders formed by two coupled planar optical waveguide arrays. For the band structure, a mid-zone gap is formed due to band hybridization and its wavenumber position can be tuned throughout the whole Brillouin zone, which is different from the Bragg gap. By imposing a gradient in the propagation constant in each array, Bloch-Zener oscillation (BZO) is realized with Zener tunneling between the bands occurring at mid zone, which is contrary to the common BZO with tunneling at the center or edge of the Brillouin zone. The occurrence of BZO is demonstrated by using the field-evolution analysis. The tunable hybridization at mid zone enhances the tunability of BZO in the optical waveguide ladders. This work is of general and fundamental importance in understanding the coherent phenomena in lattice structures.

Zheng, Ming Jie; Yu, Kin Wah

2010-01-01

308

Generation of Fock state and quantum entanglement in a coupled ladder atom-cavity system  

International Nuclear Information System (INIS)

We investigate the behaviour of an atom-cavity system via an adiabatic passage technique using a three-level ladder atom both for one-mode and for two-mode cavity QED. For one-mode cavity QED, we find that a single-photon Fock state can be generated via the technique of stimulated Raman adiabatic passage in the microwave domain. For two-mode cavity QED, we find that a two-photon pair can be generated via the technique of Stark shift rapid adiabatic passage (SRAP). We also find, for the two-mode cavity QED system, that an entangled state of the two modes in a microwave cavity can be prepared via the SRAP technique, in which the number of steps required is significantly reduced due to the adiabatic passage of the ladder atom-cavity coupled system

2003-02-01

309

Generation of Fock state and quantum entanglement in a coupled ladder atom-cavity system  

Energy Technology Data Exchange (ETDEWEB)

We investigate the behaviour of an atom-cavity system via an adiabatic passage technique using a three-level ladder atom both for one-mode and for two-mode cavity QED. For one-mode cavity QED, we find that a single-photon Fock state can be generated via the technique of stimulated Raman adiabatic passage in the microwave domain. For two-mode cavity QED, we find that a two-photon pair can be generated via the technique of Stark shift rapid adiabatic passage (SRAP). We also find, for the two-mode cavity QED system, that an entangled state of the two modes in a microwave cavity can be prepared via the SRAP technique, in which the number of steps required is significantly reduced due to the adiabatic passage of the ladder atom-cavity coupled system.

Gong Shangqing; Feng Xunli; Xu Zhizhan [Laboratory for High Intensity Optics, Shanghai Institute of Optics and Fine Mechanics, Shanghai (China)

2003-02-01

310

IPA-CuCl$_3$: a S=1/2 Ladder with Ferromagnetic Rungs  

CERN Document Server

The spin gap material IPA-CuCl3 has been extensively studied as a ferromagnetic-antiferromagnetic bondalternating S = 1/2 chain. This description of the system was derived from structural considerations and bulk measurements. New inelastic neutron scattering experiments reveal a totally different picture: IPA-CuCl3 consists of weakly coupled spin ladders with antiferromagnetic legs and ferromagnetic rungs. The ladders run perpendicular to the originally supposed bondalternating chain direction. The ferromagnetic rungs make this system equivalent to a Haldane S = 1 antiferromagnet. With a gap energy of 1.17(1) meV, a zone-boundary energy of 4.1(1) meV, and almost no magnetic anisotropy, IPA-CuCl3 may the best Haldane-gap material yet, in terms of suitability for neutron scattering studies in high magnetic fields.

Masuda, T; Manaka, H; Chung, J H

2005-01-01

311

IPA-CuCl3: a S=1/2 Ladder with Ferromagnetic Rungs  

International Nuclear Information System (INIS)

The spin gap material IPA-CuCl3 has been extensively studied as a ferromagnetic-antiferromagnetic bond-alternating S = 1/2 chain. This description of the system was derived from structural considerations and bulk measurements. New inelastic neutron scattering experiments reveal a totally different picture: IPA-CuCl3 consists of weakly coupled spin ladders with antiferromagnetic legs and ferromagnetic rungs. The ladders run perpendicular to the originally supposed bond-alternating chain direction. The ferromagnetic rungs make this system equivalent to a Haldane S = 1 antiferromagnet. With a gap energy of 1.17(1) meV, a zone-boundary energy of 4.1(1) meV, and almost no magnetic anisotropy, IPA-CuCl3 may be the best Haldane-gap material yet, in terms of suitability for neutron scattering studies in high magnetic fields.

2005-08-10

312

Three-Leg Antiferromagnetic Heisenberg Ladder with Frustrated Boundary Condition Ground State Properties  

CERN Document Server

The antiferromagnetic Heisenberg spin systems on the three-leg ladder are investigated. Periodic boundary condition is imposed in the rung direction. The system has an excitation gap for all antiferromagnetic inter-chain coupling ($J_{\\perp}>0$). The estimated gap for the strong coupling limit ($J_{\\perp}/J_1 \\to \\infty$) is 0.28$J_1$. Although the interaction is homogeneous and only nearest-neighbor, the ground states of the system are dimerized and break the translational symmetry in the thermodynamic limit. Introducing the next-nearest neighbor coupling ($J_2$), we can see that the system is solved exactly. The ground state wave function is completely dimer-ordered. Using density matrix renomalization group algorithm, we show numerically that the original model ($J_2=0$) has the same nature with the exactly solvable model. The ground state properties of the ladder with a higher odd number of legs are also discussed.

Kawano, K; Kawano, Kenro; Takahashi, Minoru

1997-01-01

313

Entrepreneurial Progress: Climbing The Entrepreneurial Ladder in Europe and The US  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate which countries have the highest potential to achieve entrepreneurial progress. This progress is defined using an entrepreneurial ladder with five successive steps: “never thought about starting a business”, “thinking about starting a business”, “taking steps to start a business”, “running a business for less than three years”, and “running a business for more than three years”. We assess the influence of individual-level and country-level variables on progr...

Zwan, P. W.; Verheul, I.; Thurik, A. R.; Grilo, I.

2009-01-01

314

The driven Jaynes-Cummings ladder: resonances at far-off resonance  

Energy Technology Data Exchange (ETDEWEB)

We propose a new scheme of single atom lasers/masers which produces a highly intensity-squeezed light virtually in a temporally stationary Fock-state. We identify the multiphoton resonances in the Jaynes-Cummings Ladder (JCL) system, and extract extremely simple dynamics of the system at the multiphoton resonance at far-off resonant frequencies. We show an anomalously high cavity mode excitation occurs at a particular set of atomic, cavity and the driving field frequencies. (author)

Chough, Young Tak; Moon, Hee Jong; Nha, Hyon Cheol; Kim, Jung Bog; An Kyung Won [KAIST, Taejon (Korea, Republic of)

1999-07-01

315

The driven Jaynes-Cummings ladder: resonances at far-off resonance  

International Nuclear Information System (INIS)

We propose a new scheme of single atom lasers/masers which produces a highly intensity-squeezed light virtually in a temporally stationary Fock-state. We identify the multiphoton resonances in the Jaynes-Cummings Ladder (JCL) system, and extract extremely simple dynamics of the system at the multiphoton resonance at far-off resonant frequencies. We show an anomalously high cavity mode excitation occurs at a particular set of atomic, cavity and the driving field frequencies. (author)

1999-11-05

316

Spatially-modulated Superfluid States in Fermionic Optical Ladder Systems with Repulsive Interactions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate two-component ultracold fermionic atoms with repulsive interactions trapped in an optical lattice with a ladder structure. By applying the Bogoliubov-de Gennes equations to an effective t-J model in the strong correlation limit, we discuss how the spatially-modulated spin-singlet pairs with d-wave like symmetry are formed in the systems with trapping potentials. Furthermore, a close examination of the condensation energy as well as the local average of potenti...

Fujihara, Yusuke; Koga, Akihisa; Kawakami, Norio

2008-01-01

317

Critical Lines and Massive Phases in Quantum Spin Ladders with Dimerization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We determine the existence of critical lines in dimerized quantum spin ladders in their phase diagram of coupling constants using the finite-size DMRG algorithm. We consider both staggered and columnar dimerization patterns, and antiferromagnetic and ferromagnetic inter-leg couplings. The existence of critical phases depends on the precise combination of these patterns. The nature of the massive phases separating the critical lines are characterized with generalized string o...

Almeida, Javier; Martin-delgado, M. A.; Sierra, G.

2007-01-01

318

Mean-field theory for Heisenberg zigzag ladder: Ground state energy and spontaneous symmetry breaking  

CERN Document Server

The spin-1/2 zig-zag Heisenberg ladder (J_1 - J_2 model) is considered. A new representation for the model is found and a saddle point approximation over the spin-liquid order parameter is performed. Corresponding effective action is derived and analytically analyzed. We observe the presence of phase transitions at values J_2/J_1=0.231 and J_2/J_1=1/2.

Mkhitaryan, V V

2006-01-01

319

Comment on ``Anomalous Thermal Conductivity of Frustrated Heisenberg Spin Chains and Ladders''  

CERN Document Server

In a recent letter [Phys. Rev. Lett. 89, 156603 (2002); cond-mat/0201300], Alvarez and Gros have numerically analyzed the Drude weight for thermal transport in spin ladders and frustrated chains of up to 14 sites and have proposed that it remains finite in the thermodynamic limit. In this comment, we argue that this conclusion cannot be sustained if the finite-size analysis is taken to larger system sizes.

Heidrich-Meisner, F; Cabra, D C; Brenig, W

2003-01-01

320

Intellectual property rights in a quality-ladder model with persistent leadership  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This article analyzes the effects of intellectual property rights in a quality-ladder model in which incumbent firms preemptively innovate in order to keep their position of leadership. Unlike in models with leapfrogging, granting non-expiring forward protection reduces the rate of innovation and imposing a non-obviousness requirement reduces R&D spending. It is shown that full protection against imitation, granted independently of the size of the lead, maximizes the average innovation rate.

Kiedaisch, Christian

2012-01-01

 
 
 
 
321

Anomalous thermal conductivity of frustrated Heisenberg spin-chains and ladders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the thermal transport properties of several quantum spin chains and ladders. We find indications for a diverging thermal conductivity at finite temperatures for the models examined. The temperature at which the non-diverging prefactor \\kappa^{(th)}(T) peaks is in general substantially lower than the temperature at which the corresponding specific heat c_V(T) is maximal. We show that this result of the microscopic approach leads to a substantial reduction for estimat...

Alvarez, J. V.; Gros, Claudius

2002-01-01

322

Inelastic quantum transport in a ladder model: Measurements of DNA conduction and comparison to theory  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate quantum transport characteristics of a ladder model, which effectively mimics the topology of a double-stranded DNA molecule. We consider the interaction of tunneling charges with a selected internal vibrational degree of freedom and discuss its influence on the structure of the current-voltage characteristics. Further, molecule-electrode contact effects are shown to dramatically affect the orders of magnitude of the current. Recent electrical transport measur...

Gutierrez, R.; Mohapatra, S.; Cohen, H.; Porath, D.; Cuniberti, G.

2006-01-01

323

Enhanced d_{x^2-y^2} pairing correlations in the two-leg Hubbard ladder  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The two-leg Hubbard ladder is characterized by the ratio of the inter- to intra-leg hopping t_perp/t, the relative interaction strength U/t and the electron filling. Here, using density matrix renormalization group and Monte Carlo simulations, we examine the dependence of the pairing correlations on these parameters. We find that the pairing correlations are enhanced when the top of the bonding quasiparticle band and the bottom of the antibonding band are near the Fermi leve...

Noack, R. M.; Bulut, N.; Scalapino, D. J.; Zacher, M. G.

1996-01-01

324

Beyond Rainbow-Ladder in a covariant three-body Bethe-Salpeter approach: Baryons  

CERN Document Server

We report on recent results of a calculation of the nucleon and delta masses in a covariant bound-state approach, where to the simple rainbow-ladder gluon-exchange interaction kernel we add a pion-exchange contribution to account for pion cloud effects. We observe good agreement with lattice data at large pion masses. At the physical point our masses are too large by about five percent, signaling the need for more structure in the gluon part of the interaction.

Sanchis-Alepuz, Hèlios; Fischer, Christian S

2014-01-01

325

Applications of the Sensor Fish Technology  

Energy Technology Data Exchange (ETDEWEB)

The Sensor Fish is an autonomous device developed at Pacific Northwest National Laboratory for U.S. Department of Energy (DOE) and Army Corps of Engineers (COE) to better understand the physical conditions fish experience during passage through hydro-turbines and other dam bypass alternatives. Since its initial development in 1997, the Sensor Fish has undergone several design changes to improve its function and extend the range of its use. The most recent Sensor Fish design, the six-degree-of-freedom (6DOF) device, has been deployed successfully to characterize the environment fish experience when they pass through several hydroelectric projects along main stem Columbia and Snake Rivers in the Pacific Northwest. Just as information gathered from crash test dummies can affect automobile design with the installation of protective designs to lessen or prevent human injury, having sensor fish data to quantify accelerations, rotations, and pressure changes, helps identify fish injury mechanisms such as strike, turbulent shear, pressure, and inertial effects, including non-lethal ones such as stunning or signs of vestibular disruption that expose fish to a higher risk of predation by birds and piscivorous fish downstream following passage.

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

2007-08-28

326

Resonant states and wavepacket super-diffusion in intra-chain correlated ladders with diluted disorder  

International Nuclear Information System (INIS)

In this work, we study a tight-binding Hamiltonian model system of a binary correlated ladder with diluted disorder. We introduce intra-chain correlations between the on-site potentials by imposing that ?i,s = - ?i,-s where s = ± 1 indexes the two ladder chains. Further, we consider each ladder chain as composed of inter-penetrating ordered and random sub-chains. We show that the presence of a random on-site distribution in one of the inter-penetrating chains leads to Anderson localization except at a specific symmetric pair of energy eigenmodes. Further, by integrating the time-dependent Schroedinger equation, we follow the time-evolution of an initially localized one-electron wavepacket. We report that the remaining delocalized resonant modes are responsible for a super-diffusive spread of the wavepacket dispersion while the wavepacket participation function remains finite. A scaling analysis of the wavepacket distribution shows that it obeys a universal scaling form with the development of a power-law tail followed by a super-diffusively evolving cutoff. We obtain three exponents characterizing this super-diffusive dynamics and show that they satisfy a simple scaling relation.

2011-04-06

327

Resonant states and wavepacket super-diffusion in intra-chain correlated ladders with diluted disorder  

Energy Technology Data Exchange (ETDEWEB)

In this work, we study a tight-binding Hamiltonian model system of a binary correlated ladder with diluted disorder. We introduce intra-chain correlations between the on-site potentials by imposing that {epsilon}{sub i,{sub s}} = - {epsilon}{sub i,-s} where s = {+-} 1 indexes the two ladder chains. Further, we consider each ladder chain as composed of inter-penetrating ordered and random sub-chains. We show that the presence of a random on-site distribution in one of the inter-penetrating chains leads to Anderson localization except at a specific symmetric pair of energy eigenmodes. Further, by integrating the time-dependent Schroedinger equation, we follow the time-evolution of an initially localized one-electron wavepacket. We report that the remaining delocalized resonant modes are responsible for a super-diffusive spread of the wavepacket dispersion while the wavepacket participation function remains finite. A scaling analysis of the wavepacket distribution shows that it obeys a universal scaling form with the development of a power-law tail followed by a super-diffusively evolving cutoff. We obtain three exponents characterizing this super-diffusive dynamics and show that they satisfy a simple scaling relation.

De Moura, F A B F; Leao, F F S; Lyra, M L [Instituto de Fisica, Universidade Federal de Alagoas, Maceio-AL 57072-970 (Brazil)

2011-04-06

328

Spin polarization in the Hubbard model with Rashba spin-orbit coupling on a ladder  

Science.gov (United States)

The competition between on-site Coulomb repulsion and Rashba spin-orbit (RSO) coupling is studied on two-leg ladders by numerical techniques. Using DMRG it is found that the contribution to the current due to the RSO coupling for a fixed value of the Hubbard repulsion U reaches a maximum at intermediate values of the RSO coupling-to-hopping ratio and eventually becomes negative. This point of maximum current is correlated with the maximum value of the spin polarization between the two legs of the ladder. The most important result is that for a fixed value of the RSO coupling, the spin polarization increases with U and seems to saturate as U->?. These behaviors are studied at various fillings in the metallic regime. Further support for these conclusions is provided by the study of persistent currents in Hubbard-Rashba models on ladder rings. The implications of this enhancement of the spin Hall effect with electron correlations for spintronic devices is discussed.

Riera, Jose

2013-03-01

329

Orbital currents and charge density waves in a generalized Hubbard ladder  

International Nuclear Information System (INIS)

We study a generalized Hubbard model on the two-leg ladder at zero temperature, focusing on a parameter region with staggered flux (SF)/d-density wave (DDW) order. To guide our numerical calculations, we first investigate the location of a SF/DDW phase in the phase diagram of the half-filled weakly interacting ladder using a perturbative renormalization group (RG) and bosonization approach. For hole doping ? away from half-filling, finite-system density-matrix renormalization-group (DMRG) calculations are used to study ladders with up to 200 rungs for intermediate-strength interactions. In the doped SF/DDW phase, the staggered rung current and the rung electron density both show periodic spatial oscillations, with characteristic wavelengths 2/? and 1/?, respectively, corresponding to ordering wavevectors 2k F and 4k F for the currents and densities, where 2k F = ? (1 - ?). The density minima are located at the anti-phase domain walls of the staggered current. For sufficiently large dopings, SF/DDW order is suppressed. The rung density modulation also exists in neighboring phases where currents decay exponentially. We show that most of the DMRG results can be qualitatively understood from weak-coupling RG/bosonization arguments. However, while these arguments seem to suggest a crossover from non-decaying correlations to power-law decay at a length scale of order 1/?, the DMRG results are consistent with a true long-range order scenario for the currents and densities

2006-04-01

330

Bond-impurity induced bound states in disordered spin-1/2 ladders  

CERN Document Server

We discuss the effect of weak bond-disorder in two-leg spin ladders on the dispersion relation of the elementary triplet excitations with a particular focus on the appearance of bound states in the spin gap. Both the cases of modified exchange couplings on the rungs and the legs of the ladder are analyzed. Based on a projection on the single-triplet subspace, the single-impurity and small cluster problems are treated analytically in the strong-coupling limit. Numerically, we study the problem of a single impurity in a spin ladder by exact diagonalization to obtain the low-lying excitations. At finite concentrations and to leading order in the inter-rung coupling, we compare the spectra obtained from numerical diagonalization of large systems within the single-triplet subspace with the results of diagrammatic techniques, namely low-concentration and coherent-potential approximations. The contribution of small impurity clusters to the density of states is also discussed.

Arlego, M; Cabra, D C; Heidrich-Meisner, F; Honecker, A; Rossini, G

2004-01-01

331

The Pan-STARRS 1 Photometric Reference Ladder, Release 12.0  

CERN Document Server

As of 2012 Jan 21, the Pan-STARRS 1 3\\pi Survey has observed the 3/4 of the sky visible from Hawaii with a minimum of 2 and mean of 7.6 observations in 5 filters, g_p1, r_p1, i_p1, z_p1, y_p1. Now at the end of the second year of the mission, we are in a position to make an initial public release of a portion of this unprecedented dataset. This article describes the PS1 Photometric Ladder, Release 12.01 This is the first of a series of data releases to be generated as the survey coverage increases and the data analysis improves. The Photometric Ladder has rungs every hour in RA and at 4 intervals in declination. We will release updates with increased area coverage (more rungs) from the latest dataset until the PS1 survey and the final re-reduction are completed. The currently released catalog presents photometry of \\approx 1000 objects per square degree in the rungs of the ladder. Saturation occurs at g_p1, r_p1, i_p1 \\approx 13.5; z_p1 \\approx 13.0; and y_p1 \\approx 12.0. Photometry is provided for stars dow...

Magnier, E A; Finkbeiner, D; Juric, M; Tonry, J L; Burgett, W S; Chambers, K C; Flewelling, H A; Kaiser, N; Kudritzki, R -P; Morgan, J S; Price, P A; Sweeney, W E; Stubbs, C W

2013-01-01

332

Hole crystallization in the spin ladder of Sr14Cu24O41  

CERN Document Server

One of the deepest questions in condensed matter physics concerns what other phases compete with superconductivity in high-transition-temperature (high-Tc) superconductors. One candidate is the "stripe" phase, in which the carriers (holes) condense into rivers of charge separating regions of antiferromagnetism. A related but lesser known system is the "spin ladder", which consists of two coupled chains of magnetic ions forming an array of rungs. A doped ladder can be thought of as a high-Tc material with lower dimensionality, and has been predicted to exhibit both superconductivity and an insulating "hole crystal" phase in which the carriers are localised through many-body interactions. The competition between the two resembles that between static stripes and superconductivity in high-Tc materials. Here we report evidence, from resonant x-ray scattering, for the existence of a hole crystal in the doped spin ladder of Sr14Cu24O41. This phase exists without a detectable distortion in the structural lattice, ind...

Abbamonte, P; Rusydi, A; Gozar, A; Evans, P G; Siegrist, T; Venema, L; Eisaki, H; Isaacs, E D; Sawatzky, G A

2004-01-01

333

Damping measurements at fish plates  

Energy Technology Data Exchange (ETDEWEB)

This paper studies oscillations of fish plate support elements, employed for suspension of large excavator or spreader booms in surface mines. Three to five plate elements (300 to 400 mm wide, 20 mm thick and 30 to 35 m long, connected by bolt joints) are generally used as high force support construction as an alternative to heavy steel ropes. Torsion damping tests were carried out at model plate elements on a one-third scale. Oscillation diagrams are provided. The damping performance was best on twin fish plate supports with bolted diaphragms, followed by the regular twin plate design and the twin plate design with welded diaphragms. The simple plate design had the lowest performance. Logarithmic damping decrements for internal damping were determined by the experiment. These values were between 0.015 and 0.04 for an oscillation amplitude of 1 degree, depending on fish plate type examined. (8 refs.) (In German)

Kwast, K.H.

1984-03-01

334

Fish Tales  

International Nuclear Information System (INIS)

This talk is about fishing and the friendships that have resulted in its pursuit. It is also about theoretical physics, and the relationship of imagination and fantasy to the establishment of ideas about nature. Fishermen, like theoretical physicists, are well known for their inventive imaginations. Perhaps neither are as clever as sailors, who conceived of the mermaid. If one doubts the power of this fantasy, one should remember the ghosts of the many sailors who drowned pursuing these young nymphs. An extraordinary painting by J. Waterhouse is shown as Fig. 1. The enchantment of a mermaid must reflect an extraordinary excess of imagination on the part of the sailor, perhaps together with an impractical turn of mind. A consummated relationship with a mermaid is after all, by its very nature a fantasy incapable of realization. To a theoretical physicist, she is symbolic of many ideas we develop. There are many truths known to fisherman in which one might also find parallels to the goals of scientists: (1) A fish is the only animal that keeps growing after its death; (2) Nothing makes a fish bigger than almost being caught; (3) ''...of all the liars among mankind, the fisherman is the most trustworthy.'' (William Sherwood Fox, in Silken Lines and Silver Hooks); and (4) Men and fish are alike. They both get into trouble when they open their mouths. These quotes may be interpreted as reflecting skepticism regarding the honesty of fisherman, and probably do not reflect adequate admiration for a creative imagination. Is it fair to criticize a person for believing a falsehood that he or she sincerely believes to be true? The fisherman simultaneously invents the lie, and believes in it himself. The parallel with theoretical physics is perhaps only approximate, although we physicists may invent stories that we come to believe, on some rare occasions our ideas actually correspond to a more or less true descriptions of nature. These minor philosophical differences are not really the central issue, however. It is more to the point that both fishermen and scientists enjoy creating a good story, and we also enjoy a story well told. The correct mixture of truth, lie, fantasy and excitement is a witches brew.

2010-07-06

335

D0 Silicon Upgrade: Thermally Induced Stresses in the Components of a D0 Ladder in the Silicon Tracker  

Energy Technology Data Exchange (ETDEWEB)

During the operation of the silicon tracker, the ladders will be in direct thermal contact with a cooling channel. The expected operating temperature of the cooling channel is 0 C, maintained by a cooling fluid whose bulk temperature is below 0 C. The assembly temperature is assumed to be 22 C. Due to the mis-match of material expansion coefficients, thermal stresses will be induced in the epoxy, beryllium, and silicon of the ladders. Calculations are presented here as well as some thermal cycling results on test samples. Shown in Figures 1 and 2 are perspective views of the top and bottom of a 3 chip ladder. The silicon temperature within the ladders will not be uniform due to the relative location of the heat dissipating components and the cooling channel. As an example the following plot demonstrates the expected temperature distribution in the 3 chip single sided ladder during operation. Under expected operating conditions of 0.75 W hybrid component power dissipation and 0.5 W per SVX II chip, the temperature profile is shown for two situations of how the ladder is constructed. The cooling channel corresponds roughly to locations on the silicon between 32 and 42 mm. The silicon in this region is sandwiched between two plates of beryllium and is about 4 C. For a construction temperature of 22 C the beryllium/silicon/beryllium assembly will see a 18 C change in temperature. To be conservative a 20 C temperature change will be assumed (some larger temperature extremes will be considered) within the ladder.

Ratzmann, Paul M.; /Fermilab

1996-07-02

336

Intelligent Fish Freshness Assessment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Fish species identification and automated fish freshness assessment play important roles in fishery industry applications. This paper describes a method based on support vector machines (SVMs) to improve the performance of fish identification systems. The result is used for the assessment of fish freshness using artificial neural network (ANN). Identification of the fish species involves processing of the images of fish. The most efficient features were extracted and combined with the down-sa...

Hamid Gholam Hosseini; Dehan Luo; Guanggui Xu; Hongxiu Liu; Deena Benjamin

2008-01-01

337

Fish and fish oil intake: effect on haematological variables related to cardiovascular disease.  

Science.gov (United States)

To investigate the effects of practical amounts of n-3 highly-unsaturated fatty acids (HUFA) on a number of parameters involved in haemostasis, 12 healthy men were fed three diets in a 3 x 3 cross-over design. The diets, fed as the evening meal for 6-week periods, were: Control diet (essentially fish-free), Fish diet (200 g/d of lean Australian fish flesh) and the same fish-based diet but supplemented with 5 g/d fish oil (Fish + Oil). The diets supplied about 0, 0.6, and 2.0 g n-3 HUFA/d, respectively. Relative to the Control diet, the number of circulating leukocytes was significantly reduced after both the Fish and Fish + Oil diets (by 13% and 15%, respectively). This reduction occurred in the number of neutrophils, although this did not reach significance on the Fish diet alone. Platelet count fell on the Fish + Oil diet (by 6%) but not on the Fish diet alone. There was an apparent enhancement of fibrinolytic potential after both fish-containing diets, which tended to be accentuated with the fish oil supplementation. The mechanisms underlying some if not all of these observations may be eicosanoid-mediated as indicated by a diminution in the platelet arachidonic acid (20:4n-6) to eicosapentaenoic acid (20:5n-3) ratios after the Fish + Oil (13.7 +/- 1.8) and Fish (34.4 +/- 8.9) diets relative to the Control diet (66.1 +/- 15.6). These data suggest that a practical amount of lean fish can improve certain haematological parameters implicated in the etiology of cardiovascular disease. PMID:1811337

Brown, A J; Roberts, D C

1991-10-15

338

Microbiological spoilage of fish and fish products  

DEFF Research Database (Denmark)

Spoilage of fresh and lightly preserved fish products is caused by microbial action. This paper reviews the current knowledge in terms of the microbiology of fish and fish products with particular emphasis on identification of specific spoilage bacteria and the qualitative and quantitative biochemical indicators of spoilage. Shewanzella putrefaciens and Pseudomonas spp. are the specific spoilage bacteria of iced fresh fish regardless of the origin of the fish. Modified atmosphere stored marine fish from temperate waters are spoiled by the CO2 resistant Photobacterium phosphoreum whereas Gram- positive bacteria are likely spoilers of CO2 packed fish from fresh or tropical waters. Fish products with high salt contents may spoil due to growth of halophilic bacteria (salted fish) or growth of anaerobic bacteria and yeasts (barrel salted fish). Whilst the spoilage of fresh and highly salted fish is well understood, much less is known about spoilage of lightly preserved fish products. It is concluded that the spoilage is probably caused by lactic acid bacteria, certain psychrotrophic Enterobacteriaceae and/or Photobacterium phosphoreum. However, more work is needed in this area

Gram, Lone; Huss, Hans Henrik

1996-01-01

339

The impact of product experience, product involvement and verbal processing style on consumers' cognitive structure with regard to fresh fish  

DEFF Research Database (Denmark)

Executive summary 1) The means-end chain model has been widely advocated for the understanding of how consumers perceive self-relevant consequences of products. The model implies that subjective product meaning is established by associations between product attributes and more abstract, more central cognitive categories like values. A means-end chain consists of concrete product attributes, abstract product attributes, functional consequences, psychosocial consequences, instrumental values, a terminal values. 2) The most common method of measuring means-end chains has been the laddering interview technique. Laddering is a semi-qualitative technique which is open for the respondent's own answers without flooding the interviewer with data, as do other qualitative techniques. The results from the laddering interviews are coded and usually presented in a so-called hierarchical value map. 3) However popular, a number of problems with means-end chain analysis have been pointed out. In this paper we report how threevariables affect the outcome of a laddering study, namely (1) product experience, (2) product involvement, and (3) verbal processing style. 4) 90 respondents in the Copenhagen area were interviewed. Respondents were asked to rank four meat types, ie, (1) a fresh, whole, gutted plaice, (2) a package of frozen fish fillets, (3) a whole, frozen chicken, and (4) a package of fresh pork chops, according to how likely it would be that they would use them for a hot meal on a work Respondents were asked to give reasons for the ranking, and from the answers given, laddering procedures were carried out. 5) At the aggregate level, ie when comparing hierarchical value maps across different groups of consumers, the investigation showed that less involved consumers perceived more negative consequences of the consumption of fresh plaice than did the more involved consumers. Fresh fish is perceived to be difficult to get hold of ­ it has to be bought at the fishmonger's ­ di to prepare, and difficult to eat. These aspects are considered time-consuming and result in less time spent with the family. Both the less involved and the more involved consumers regard fresh plaice as healthy. 6) At the individual level, ie when comparing the amount and character of the data provided by the individual respondents, we found that consumers' level of experience had a significant positive relationship with the number of ladders retrieved in the interviews and a significant ne relationship with the proportion of consequence categories. There was no effect on the value categories' share of the total number of categories. As for consumers' level of involvement we found a significant positive correlation with the number of ladders provided in the interviews. Consumers' tendency towards a verbal processing style seemed to have no influence on neither the number of ladders, average length of the ladders, nor the proportion of value categories in the data set. 7) The study seems to indicate that it is possible to employ laddering with consumers withboth higher and lower degrees of involvement and experience. The study also showed that the respondent's capability of verbal processing had no influence on the results. method can therefore not be said to be more or less applicable to respondents with varying degrees of verbal processing ability.

Sørensen, Elin; Grunert, Klaus G.

1996-01-01

340

Crossover from Electromagnetically Induced Transparency to Autler-Townes Splitting in Open Ladder Systems with Doppler Broadening  

CERN Document Server

We propose a general theoretical scheme to investigate the crossover from electromagnetically induced transparency (EIT) to Autler-Townes splitting (ATS) in open ladder-type atomic and molecular systems with Doppler broadening. We show that when the wavenumber ratio $k_c/k_p\\approx -1$, EIT, ATS, and EIT-ATS crossover exist for both ladder-I and ladder-II systems, where $k_c$ ($k_p$) is the wavenumber of control (probe) field. Furthermore, when $k_c/k_p$ is far from $-1$ EIT can occur but ATS is destroyed if the upper state of the ladder-I system is a Rydberg state. In addition, ATS exists but EIT is not possible if the control field used to couple the two lower states of the ladder-II system is a microwave field. The theoretical scheme developed here can be applied to atoms, molecules, and other systems (including Na$_2$ molecules, and Rydberg atoms), and the results obtained may have practical applications in optical information processing and transformation.

Tan, Chaohua

2013-01-01

 
 
 
 
341

Component processes in contour integration: a direct comparison between snakes and ladders in a detection and a shape discrimination task.  

Science.gov (United States)

In contour integration, a relevant question is whether snakes and ladders are processed similarly. Higher presentation time thresholds for ladders in detection tasks indicate this is not the case. However, in a detection task only processing differences at the level of element linking and possibly contour localization might be picked up, while differences at the shape encoding level cannot be noticed. In this study, we make a direct comparison of detection and shape discrimination tasks to investigate if processing differences in the visual system between snakes and ladders are limited to contour detection or extend to higher level contour processing, like shape encoding. Stimuli consisted of elements that were oriented collinearly (snakes) or orthogonally (ladders) to the contour path and were surrounded by randomly oriented background elements. In two tasks, six experienced subjects either detected the contour when presented with a contour and a completely random stimulus or performed a shape discrimination task when presented with two contours with different curvature. Presentation time was varied in 9 steps between 8 and 492 ms. By applying a generalized linear mixed model we found that differences in snake and ladder processing are not limited to a detection stage but are also apparent at a shape encoding stage. PMID:24051198

Vancleef, Kathleen; Wagemans, Johan

2013-11-01

342

THE PAN-STARRS 1 PHOTOMETRIC REFERENCE LADDER, RELEASE 12.01  

International Nuclear Information System (INIS)

As of 2012 January 21, the Pan-STARRS 1 3? Survey has observed the 3/4 of the sky visible from Hawaii with a minimum of 2 and mean of 7.6 observations in five filters, g P1, r P1, i P1, z P1, y P1. Now at the end of the second year of the mission, we are in a position to make an initial public release of a portion of this unprecedented data set. This article describes the PS1 Photometric Ladder, Release 12.01. This is the first of a series of data releases to be generated as the survey coverage increases and the data analysis improves. The Photometric Ladder has rungs every hour in right ascension and at four intervals in declination. We will release updates with increased area coverage (more rungs) from the latest data set until the PS1 survey and the final re-reduction are completed. The currently released catalog presents photometry of ?1000 objects per square degree in the rungs of the ladder. Saturation occurs at g P1, r P1, i P1 ? 13.5; z P1 ? 13.0; and y P1 ? 12.0. Photometry is provided for stars down to g P1, r P1, i P1 ? 19.1 in the AB system. This data release depends on the rigid 'Ubercal' photometric calibration using only the photometric nights, with systematic uncertainties of (8.0, 7.0, 9.0, 10.7, 12.4) mmag in (g P1, r P1, i P1, z P1, y P1). Areas covered only with lower quality nights are also included, and have been tied to the Ubercal solution via relative photometry; photometric accuracy of the non-photometric regions is lower and should be used with caution.

2013-04-01

343

Measurement of the Rise-Time in a Single Sided Ladder Detector  

Energy Technology Data Exchange (ETDEWEB)

In this note we report on the measurement of the preamplifier output rise time for a SVXII chip mounted on a D0 single sided ladder. The measurements were performed on the ladder 001-883-L, using the laser test stand of Lab D. The rise time was measured for different values of the response (or bandwidth) of the preamplifier. As a bigger bandwidth results in longer rise times and therefore in less noise, the largest possible bandwidth consistent with the time between bunch crossings should be chosen to operate the detectors. The rise time is defined as the time elapsed between 10% and 90% of the charge is collected. It is also interesting to measure the time for full charge collection and the percentage of charge collected in 132 ns and 396 ns. The results are shown in table 1, for bandwidths between 2 and 63 (binary numbers). The uncertainty on the time measurement is considered to be {approx} 10 ns. Figure 1 schematically defines the four quantities measured: rise time, time of full charge collection, and percentage of charge collected in 132 ns and 396 ns. Figures 2 to 8 are the actual measurements for bandwidths of 2, 4, 8, 12, 24, 32 and 63. Figure 9 is a second measurement for BW=24, used as a consistency check of the system and the time measurement performed on the plots. The data indicate that the single sided ladders can be operated at BW=63 for 396 ns and BW=12 for 132 ns, achieving full charge collection. This will result in smaller noise than originally anticipated.

Gerber, C.E.; /Fermilab

1997-11-10

344

Review of mitigation methods for fish passage, instream flows, and water quality  

International Nuclear Information System (INIS)

This paper reports on current environmental mitigation practices at nonfederal hydropower projects. Information was obtained from project operators on dissolved oxygen (DO) mitigation, instream flows, upstream fish passage facilities, and downstream fish passage facilities. The most common method for DO mitigation is the use of spill flows, which are costly because of lost power generation. DO concentrations are commonly monitored, but biological effects of DO mitigation are not. At many projects, instream flow requirements have been set without reference to formalized methods. About half of the projects with instream flow requirements monitor flow rates, but few monitor fish populations to verify that instream flows are effective. Angled bar racks are the most commonly used downstream fish passage devices and fish ladders are the most commonly used upstream fish passage devices. Fish passage rates or populations have been monitored to verify the effectiveness of passage mitigation at few projects. This analysis is the first phase of an evaluation of the costs, benefits, and effectiveness of mitigation measures

1991-07-24

345

Traditional fishing tools  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper I present the traditional fishing tools used in the area of the Danube Delta. More precisely, I speak about the village of Sfantu Gheorghe, a traditional fishing village, where the fishing activity has been the main activity along the years and where, lately, there have been major changes due to the decrease of the fish species.

STOICA Georgeta

2009-09-01

346

Types of fish pass  

…place the entrance of the fish pass close to the natural gatherings of ascending fish. To overcome these problems, active methods of passing fish have been developed. Fish are drawn into a collection area by an attraction flow and then periodically a downstream gate or sluice is closed to allow the water…

347

Comment on "Metal-Insulator Transition in an Aperiodic Ladder Network: An Exact Result"  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Sil, Maiti, and Chakrabarti (SMC) (Phys. Rev. Lett. 101, 076803 (2008), arXiv:0801.2670) introduce an aperiodic two-leg ladder network composed of atomic sites with on-site potentials distributed according to a quasiperiodic Aubry-Andre potential. SMC claim the existence of multiple mobility edges, i.e. metal-insulator transitions at multiple values of the Fermi energy. SMC use numerical calculations of the conductance and den- sity of states, and an analytical result in a l...

Flach, Sergej; Danieli, Carlo

2014-01-01

348

Role of quadratic and cubic spectral phases in ladder climbing with ultrashort pulses  

International Nuclear Information System (INIS)

Two-photon excitation of a quantum ladder system by an ultrashort chirped pulse leads to interferences in the excited-state population, between direct and sequential paths. Experimental results have been obtained in atomic sodium vapor. The presence of several intermediate and final states leads to new phenomena. The interplay between the two sequential paths leads to strongly contrasted oscillations and a large enhancement of the transition probability for precise values of the chirp. A cubic spectral phase modifies significantly the behavior of the quantum interferences and can be used to enhance the two-photon absorption rate

2004-11-01

349

Electron energy-loss investigation of the electronic structure of a PPP-related ladder polymer  

Energy Technology Data Exchange (ETDEWEB)

The electronic structure of a ladder polymer of PPP has been investigated by high energy electron energy-loss spectroscopy (EELS) in transmission. The band gap of the undoped compound is about 0.4eV smaller compared to PPP. Information on the character of the undoped LPPP as well as on bipolaron states formed upon K doping in the former band gap are obtained from momentum dependent EELS investigations. The extension of the bipolaron is estimated to 20{+-}4A. (orig.)

Romberg, H.A. [Kernforschungszentrum Karlsruhe, Institut fuer Nukleare Festkoerperphysik, Postfach 3640, 76021 Karlsruhe (Germany); Nuecker, N. [Kernforschungszentrum Karlsruhe, Institut fuer Nukleare Festkoerperphysik, Postfach 3640, 76021 Karlsruhe (Germany); Fink, J. [Institut fuer Festkoerperforschung, IFW Dresden e.V., Postfach, 01171 Dresden (Germany); Unterweger, O.F. [Institut fuer Festkoerperphysik, Technische Universitaet Graz, Petersgasse 16, 8010 Graz (Austria); Stampfl, J. [Institut fuer Festkoerperphysik, Technische Universitaet Graz, Petersgasse 16, 8010 Graz (Austria); Leising, G. [Institut fuer Festkoerperphysik, Technische Universitaet Graz, Petersgasse 16, 8010 Graz (Austria)

1995-03-01

350

Field-induced nematic phase in the spin ladder system with easy-axis anisotropy  

Energy Technology Data Exchange (ETDEWEB)

The spin ladder system with the easy-axis anisotropy in magnetic field is theoretically investigated using the numerically exact diagonalization, the density matrix renormalization group (DMRG) and the finite-size scaling analysis. It is found that the field-induced nematic phase appears above the critical field. In addition, there exists another critical field at which the quantum phase transition from the nematic phase to the conventional field-induced Tomonaga-Luttinger liquid (TLL) phase occurs. The phase diagram on the coupling anisotropy versus magnetization plane is given by the numerical diagonalization. Furthermore, a typical magnetization curve calculated by the DMRG is presented. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Sakai, Toru [Japan Atomic Energy Agency (JAEA), Hyogo (Japan); Graduate School of Material Science, University of Hyogo (Japan); Transformative Research-Project on Iron Pnictide, JST, Saitama (Japan); Tonegawa, Takashi [Department of Mechanical Engineering, Fukui University of Technology, Fukui (Japan); Okamoto, Kiyomi [Department of Physics, Tokyo Institute of Technology, Tokyo (Japan)

2010-03-15

351

Quantum compass model on a chain, ladder and finite square clusters  

Science.gov (United States)

I show the exact solutions for the quantum compass model on a chain and ladder which are based on mapping to quantum Ising models in certain subspaces. I discuss the ground state and thermodynamic properties of both models. I show the spin transformation that maps L×L quantum compass model to (L-1)×(L-1) spin model and its applications to compass clusters of the sizes 4×4 and 5×5. I discuss the ground-state and thermodynamic properties of these models.

Brzezicki, W.

2010-11-01

352

Observation of atomic Wannier-Stark ladders in an accelerating optical potential  

International Nuclear Information System (INIS)

We report observation of Wannier-Stark ladders with ultracold sodium atoms in an accelerating one-dimensional standing wave of light. Atoms are trapped in a far-detuned standing wave that is accelerated for a controlled duration. A small oscillatory component is added to the acceleration, and the fraction of trapped atoms is measured as a function of the oscillation frequency. Resonances are observed where the number of trapped atoms drops dramatically. The separation between resonant peaks is found to be proportional to the acceleration. We show that this resonant structure can also be understood as a temporal quantum interference effect. copyright 1996 The American Physical Society

1996-06-01

353

Effects of aluminum trichloride and magnesium chloride on the synthesis of ladder polyphenylsilsesquioxane  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ladder polyphenylsilsesquioxane (Ph-LPSQ) has been synthesized at 80°C through the hydrolysis and condensation of phenyltrichlorosilane (PhSiCl3), with aluminum chloride (AlCl3) or magnesium chloride (MgCl2) as an assistant reactant. The Ph-LPSQ obtained has been characterized and analyzed by SEM, FTIR, TGA, 29Si NMR, and MALDI-TOF MS, and the effects of AlCl3and MgCl2on the structure regularity of Ph-LPSQ and the condensation polymerizationhavealso been studied. The results showed tha...

Jiang Yunyun; Yang Rongjie

2012-01-01

354

Thermodynamics of the t-J Ladder A Stable Finite Temperature Density Matrix Renormalization Group Calculation  

CERN Multimedia

Accurate numerical simulations of a doped t-J model on a two-leg ladder are presented for the particle number, chemical potential, magnetic susceptibility and entropy in the limit of large exchange coupling on the rung using a finite temperature density matrix renormalization group (TDMRG) method. This required an improved algorithm to achieve numerical stability down to low temperatures. The thermal dissociation of hole pairs and of the rung singlets are separately observed and the evolution of the hole pair binding energy and magnon spin gap with hole doping is determined.

Ammon, B; Rice, T M; Shibata, N; Ammon, Beat; Troyer, Matthias

1999-01-01

355

The Electronic Structure of Spin Ladders and Spin Chains Studied by Ellipsometry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Within the scope of this thesis, a spectroscopic ellipsometer has been put into operation and equipped with a UHV liquid Helium flow cryostat to enable low temperature optical measurements down to 10 K in the energy range between 0.8 to 5 eV. After successful installation of the ellipsometer, a systematic investigation of the electronic structure of one-dimensional copper-oxide spin ladders and spin chains was carried out. Ellipsometric optical conductivity data of the biaxial copper oxide co...

2009-01-01

356

Snakes and ladders: Localized states in the Swift-Hohenberg equation  

Energy Technology Data Exchange (ETDEWEB)

The Swift-Hohenberg equation with cubic and quintic nonlinearities exhibits multiple stable and unstable spatially localized states of arbitrary length in the vicinity of the Maxwell point between spatially homogeneous and periodic states. The even and odd states are organized in a characteristic snaking structure and are connected by branches of mixed parity states forming a ladder-like structure. Numerical computations are used to illustrate the changes in the localized solutions as they grow in spatial extent and to determine the stability and wavelength of the resulting states.

Burke, John [Department of Physics, University of California, Berkeley, CA 94720 (United States)]. E-mail: burkej8@socrates.berkeley.edu; Knobloch, Edgar [Department of Physics, University of California, Berkeley, CA 94720 (United States)

2007-01-15

357

Empirical patterns of firm growth and r&d investment:a quality ladder model interpretation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a model of endogenous firm growth with R&D investment and innovation as the engine of growth. The objective of our analysis is to present a framework that can be used for microeconometric analysis of firm performance in high-tech industries. The model for firm growth is a partial equilibrium model drawing on the quality ladder models in the macro growth literature, but also on the literature on patent races and the discrete choice models of product differentiation. We examine t...

Klette, Tor Jakob; Griliches, Zvi

1997-01-01

358

The unusual electronic structure of the "pseudo-ladder" compound CaCu2O3  

CERN Document Server

Experimental and theoretical studies of the unoccupied electronic structure of CaCu2O3 single crystals have been performed using polarization-dependent x-ray absorption spectroscopy and band structure calculations. The measured hole distribution shows an unusual large number of holes in orbitals parallel to the interlayer direction which is in agreement with the theoretical analysis. CaCu2O3 deviates significantly from the standard pd-sigma cuprate picture. The corresponding strong interlayer exchange is responsible for the missing spin gap generic for other two-leg ladder cuprates.

Kim, T K; Drechsler, S L; Hu, Z; Sekar, C; Krabbes, G; Malek, J; Knupfer, M; Fink, J; Eschrig, H

2002-01-01

359

Spin ladder with anisotropic ferromagnetic legs in a transverse magnetic field  

Energy Technology Data Exchange (ETDEWEB)

We have studied the ground-state phase diagram of a two-leg spin ladder with anisotropic ferromagnetic leg couplings under the influence of a symmetry-breaking transverse magnetic field by the exact diagonalization technique. In the case of antiferromagnetic coupling between legs we identified two phase transitions in the plane of magnetic field versus interchain coupling strength. The first corresponds to the transition from the gapped rung-singlet phase to the gapped stripe-ferromagnetic phase. The second represents the transition from the gapped stripe-ferromagnetic phase into the fully polarized ferromagnetic phase.

Japaridze, G I [International Center for Condensed Matter Physics, Universidade de Brasilia, 70904-910 Brasilia-DF (Brazil); Langari, A [Physics Department, Sharif University of Technology, Tehran 11365-9161 (Iran, Islamic Republic of); Mahdavifar, S [Institute for Advanced Studies in Basic Sciences, Zanjan 45195-1159 (Iran, Islamic Republic of)

2007-02-21

360

New nonlinear coherent states associated with inverse bosonic and f-deformed ladder operators  

Energy Technology Data Exchange (ETDEWEB)

Using the nonlinear coherent states method, a formalism for the construction of the coherent states associated with 'inverse bosonic operators' and their dual family has been proposed. Generalizing the approach, the 'inverse of f-deformed ladder operators' corresponding to the nonlinear coherent states in the context of quantum optics and the associated coherent states have been introduced. Finally, after applying the proposal to a few known physical systems, particular nonclassical features as sub-Poissonian statistics and the squeezing of the quadratures of the radiation field corresponding to the introduced states have been investigated.

Tavassoly, M K [Atomic and Molecular Group, Faculty of Physics, Yazd University, Yazd (Iran, Islamic Republic of)], E-mail: mktavassoly@yazduni.ac.ir

2008-07-18

 
 
 
 
361

Photofluxonic detection in ladders and 2D arrays of Josephson junctions  

International Nuclear Information System (INIS)

The transport mechanism of vortices in a new class of photofluxonic detectors based on Josephson Junction (JJ) arrays is examined in detail. Spatial resolution is easily achievable only if the vortex/antivortex moves at constant velocity. Our simulations show that this is the case of JJ ladders. In 2D JJ arrays the situation is less simple: x-y resolution seems possible only in a small range of the bias current values, beyond an upper critical value the detector becomes unstable. (orig.)

1996-02-11

362

Polarization-dependent discharge in fibers of semiconducting ladder-type polymer  

CERN Document Server

We report results on polarization-dependent photoinduced discharge in oriented fibers and films of ladder-type, electron-transporting polymer poly (benzimidazobenzophenanthroline), BBL. The photocarrier generation efficiency in the fiber which is indicated by the rate of discharge, is found to be distinctly higher for light polarized parallel to the fiber axis as compared to the radially perpendicular direction . Similar results, with photocarrier generation efficiency anisotropy ~ 10 are obtained for oriented films. These observations are different from previously obtained results on polyparaphenylenevinylene (PPV). The results are compared with the polarization-dependent steady- state photoconductivity measurements. We interpret these results on the basis of molecular and macroscopic features of the material.

Kumar, N

2001-01-01

363

nu/sub 3/ vibrational ladder of SF/sub 6/  

Energy Technology Data Exchange (ETDEWEB)

From an analysis of the high-resolution spectrum of the 3 nu/sub 3/ manifold of SF/sub 6/, the anharmonicity constants were determined to be (in reciprocal centimeters) X/sub 33/ = -1.7426, G/sub 33/ = 0.9188, and T/sub 33/ = -0.24635. By using these constants, one can for the first time to our knowledge accurately predict the energies of the lower-vibrational sublevels of the nu/sub 3/ ladder and determine the pathways for multiple-photon absorption.

Patterson, C.W. (Los Alamos Scientific Lab., NM); Krohn, B.J.; Pine, A.S.

1981-01-01

364

Doping dependence of the spin gap in a two-leg ladder  

Science.gov (United States)

A spin-fermion model relevant for the description of cuprates ladders is studied in a path integral formalism, where, after integrating out the fermions, an effective action for the spins in term of a Fermi-determinant results. The determinant can be evaluated in the long-wavelength, low-frequency limit to all orders in the coupling constant, leading to a non-linear ? model with doping dependent coupling constants. An explicit evaluation shows that the magnon gap diminishes upon doping, as opposed to previous mean-field treatments.

Campos Venuti, L.; Muramatsu, A.

2002-11-01

365

Doping dependence of the spin gap in a 2-leg ladder  

CERN Document Server

A spin-fermion model relevant for the description of cuprates ladders is studied in a path integral formalism, where, after integrating out the fermions, an effective action for the spins in term of a Fermi-determinant results. The determinant can be evaluated in the long-wavelength, low-frequency limit to all orders in the coupling constant, leading to a non-linear sigma model with doping dependent coupling constants. An explicit evaluation shows, that the spin-gap diminishes upon doping as opposed to previous mean-field treatments.

Venuti, L C

2002-01-01

366

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

"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",...

2011-01-01

367

Role of bound pairs in the optical properties of highly excited semiconductors a self consistent ladder approximation approach  

CERN Document Server

Presence of bound pairs (excitons) in a low-temperature electron-hole plasma is accounted for by including correlation between fermions at the ladder level. Using a simplified one-dimensional model with on-site Coulomb interaction, we calculate the one-particle self-energies, chemical potential, and optical response. The results are compared to those obtained in the Born approximation, which does not account for bound pairs. In the self-consistent ladder approximation the self-energy and spectral function show a characteristic correlation peak at the exciton energy for low temperature and density. In this regime the Born approximation overestimates the chemical potential. Provided the appropriate vertex correction in the interaction with the photon is included, both ladder and Born approximations reproduce the excitonic and free pair optical absorption at low density, and the disappearance of the exciton absorption peak at larger density. However, lineshapes and energy shifts with density of the absorption an...

Piermarocchi, C

2000-01-01

368

Boats to Burn: Bajo Fishing Activity in the Australian Fishing Zone  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Under a Memorandum of Understanding between Indonesia and Australia, traditional Indonesian fishermen are permitted access to fish in a designated area inside the 200 nautical mile Australian Fishing Zone (AFZ). However, crew and vessels are regularly apprehended for illegal fishing activity outside the permitted areas and, after prosecution in Australian courts, their boats and equipment are destroyed and the fishermen repatriated to Indonesia. This is an ethnographic study of one group of I...

Stacey, Natasha

2007-01-01

369

Fish under exercise  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Improved knowledge on the swimming physiology of fish and its application to fisheries science and aquaculture (i.e., farming a fitter fish) is currently needed in the face of global environmental changes, high fishing pressures, increased aquaculture production as well as increased concern on fish well-being. Here, we review existing data on teleost fish that indicate that sustained exercise at optimal speeds enhances muscle growth and has consequences for flesh quality. Potential added bene...

Palstra, A. P.; Planas, J. V.

2011-01-01

370

Oman Fish Biodiversity ?????? ?????? ?????? ????? ????  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The current work presents a comprehensive checklist of the Omani fish species. The different fish samples have been collected since the establishment of the Department of Marine Science and Fisheries (MSAF) in 1986. The fish samples identified by the MSAF were compared with the most recent published book on the Coastal Fishes of Oman. The number of Omani fishes (from both fresh water and sea water) totalled 1179, distributed in 527 genera, 165 families and 37 orders. Under the Chondrichtyes, ...

Saud Al-Jufaili; Greg Hermosa; Sulaiman Al-Shuaily; Amal Al-Mujaini

2010-01-01

371

Two-channel Kondo Lattice Model on a ladder studied by the Density Matrix Renormalization Group Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Using the density matrix renormalization group (DMRG) method we study a two-channel Kondo lattice model on a half filled ladder. Our model involves an on-site s-wave and a nearest neighbor d-wave coupling between the local moments and the conduction electrons on the ladder. By changing the relative strength of the two Kondo interactions we examine the evolution of the system from a conventional Kondo insulator with a singlet at each site to a new kind of semimetallic state f...

Moreno, Juana; Qin, Shaojin; Coleman, P.; Yu, Lu

2000-01-01

372

Consumer beliefs regarding farmed versus wild fish.  

Science.gov (United States)

Aquaculture is a food-producing activity, alternative to traditional extractive fishing, which still acts as a reference for most consumers. The main objective of the present paper was to study which consumer beliefs, regarding farmed versus wild fish, hinder the potential development of the aquaculture sector. To achieve this purpose the study was organized into two complementary steps: a qualitative approach (focus groups) aimed at assessing consumer perception about wild and farmed fish and to identify the salient beliefs that differentiate them; and a quantitative approach (survey by means of a questionnaire) to validate the results obtained in the focus group discussions over a representative sample of participants (n = 919). Results showed that participants perceive clear differences between farmed and wild fish. Although no significant differences between both kinds of fish were detected on safety, in general farmed fish was perceived to be less affected by marine pollution, heavy metals and parasites. In the contrary, wild fish was considered to have healthier feeding, to contain fewer antibiotics and to be fresher, healthier, less handled and more natural. Beliefs related to quality were in favour of wild fish, while those related to availability and price were in favour of farmed fish. Significant differences were observed in the perception of both kinds of fish depending on the consumers' objective knowledge about fish, on the level of education, age and gender and on the three segments of consumers identified: "Traditional/Conservative", "Connoisseur", "Open to aquaculture". The results provided could play an important role when planning and designing efficient marketing strategies for promoting farmed fish by adapting the information provided to the perception of each segment of consumers identified by the present study. PMID:24709486

Claret, Anna; Guerrero, Luis; Ginés, Rafael; Grau, Amàlia; Hernández, M Dolores; Aguirre, Enaitz; Peleteiro, José Benito; Fernández-Pato, Carlos; Rodríguez-Rodríguez, Carmen

2014-08-01

373

Star formation relations and CO SLEDs across the J-ladder and redshift  

CERN Document Server

We present FIR-CO luminosity relations ($\\log L_{\\rm FIR} = \\alpha \\log L'_{\\rm CO} + \\beta$) for the full CO rotational ladder from J=1-0 to J=13-12 for 62 local (z 1) by including 35 (sub)-millimeter selected dusty star forming galaxies from the literature with robust CO observations. The addition of luminous starbursts at high redshifts enlarge the range of the FIR-CO luminosity relations towards the high-IR-luminosity end while also significantly increasing the small amount of mid-/high-J CO line data available prior to Herschel. This new data-set (both in terms of IR luminosity and J-ladder) reveals linear FIR-CO luminosity relations ($\\alpha \\sim 1$) for J=1-0 up to J=5-4, with a nearly constant normalisation ($\\beta \\sim 2$). This is expected from the (also) linear FIR-(molecular line) relations found for the dense gas tracer lines (HCN and CS), as long as the dense gas mass fraction does not vary strongly within our (merger/starburst)-dominated sample. However from J=6-5 and up to J=13-12 we find an ...

Greve, T R; Xilouris, E M; Weiss, A; Zhang, Z -Y; van der Werf, P; Aalto, S; Armus, L; Diaz-Santos, T; Evans, A S; Fischer, J; Gao, Y; Gonzalez-Alfonso, E; Harris, A; Henkel, C; Meijerink, R; Naylor, D A; Smith, H A; Spaans, M; Stacey, G J; Veilleux, S; Walter, F

2014-01-01

374

Spinful fermionic ladders at incommensurate filling: Phase diagram, local perturbations, and ionic potentials  

Energy Technology Data Exchange (ETDEWEB)

We study the effect of external potential on transport properties of the fermionic two-leg ladder model. The response of the system to a local perturbation is strongly dependent on the ground state properties of the system and especially on the dominant correlations. We categorize all phases and transitions in the model (for incommensurate filling) and introduce “hopping-driven transitions” that the system undergoes as the inter-chain hopping is increased from zero. We also describe the response of the system to an ionic potential. The physics of this effect is similar to that of the single impurity, except that the ionic potential can affect the bulk properties of the system and in particular induce true long range order. -- Highlights: •We study low temperature electronic properties of a two leg ladder. •We find a wide variety of phase transitions as a function of model parameters. •We study the effect of impurities on these models. •Conductance may be very sensitive to the structure of these impurities.

Carr, Sam T., E-mail: S.T.Carr@kent.ac.uk [School of Physical Sciences, University of Kent, Canterbury CT2 7NH (United Kingdom); Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76128 Karlsruhe (Germany); DFG Center for Functional Nanostructures, Karlsruher Institut für Technologie, 76128 Karlsruhe (Germany); Narozhny, Boris N. [Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76128 Karlsruhe (Germany); DFG Center for Functional Nanostructures, Karlsruher Institut für Technologie, 76128 Karlsruhe (Germany); Nersesyan, Alexander A. [The Abdus Salam International Centre for Theoretical Physics, 34100, Trieste (Italy)

2013-12-15

375

Trait anxiety and goal difficulty on learning to climb the Bachman ladder.  

Science.gov (United States)

This study examined the effects of trait anxiety and goal setting on learning of the Bachman ladder. It was hypothesized that easy goals would increase learning for individuals with high trait anxiety while hard goals would increase learning for individuals with low trait anxiety. 80 high school students (40 boys, 40 girls; M age = 15 yr., SD = 1.0) filled out the Brazilian State-Trait Anxiety Inventory (STAI) for trait anxiety. The experiment was divided into four phases: acquisition, immediate transfer (after 5 min.), delayed transfer, and retention (after 24 hr.). On the transfer phases, the participants started climbing the ladder with the foot opposite of that used in acquisition. Participants were assigned to one of four experimental groups combining high and low anxiety traits and hard and easy goals. Variances were analyzed with repeated measurements on the last factor of all phases. The results showed the performance increased during the acquisition phase and no effects were observed in any phases. PMID:24897874

Neiva, Jaqueline F O; Barros, Joao A C; Meira, Cassio M

2014-04-01

376

Spinful fermionic ladders at incommensurate filling: Phase diagram, local perturbations, and ionic potentials  

International Nuclear Information System (INIS)

We study the effect of external potential on transport properties of the fermionic two-leg ladder model. The response of the system to a local perturbation is strongly dependent on the ground state properties of the system and especially on the dominant correlations. We categorize all phases and transitions in the model (for incommensurate filling) and introduce “hopping-driven transitions” that the system undergoes as the inter-chain hopping is increased from zero. We also describe the response of the system to an ionic potential. The physics of this effect is similar to that of the single impurity, except that the ionic potential can affect the bulk properties of the system and in particular induce true long range order. -- Highlights: •We study low temperature electronic properties of a two leg ladder. •We find a wide variety of phase transitions as a function of model parameters. •We study the effect of impurities on these models. •Conductance may be very sensitive to the structure of these impurities

2013-12-01

377

Charge Density Waves and Bond Order Waves in a quarter filled extended Hubbard ladder  

CERN Document Server

We investigate the phase diagram of a quarter filled Hubbard ladder with nearest-neighbor Coulomb repulsion using bosonization and renormalization group approach. Focusing on the strong-repulsion regime, we discuss the effect of an interchain exchange interaction J and interchain repulsion V on the possible ground states of the system and charge order configurations. Since the spin excitations always possess a gap, we find competing bond-order wave and charge density wave phases as possible ground states of the ladder model. We discuss the elementary excitations in these various phases and point an analogy between the excitations on some of these phases and those of a Kondo-Heisenberg insulator. We also study the order of the quantum phase transitions between the different ground states of the system. We obtain second order transitions in the Ising or SU(2)_2 universality class or first order transitions. We map the complete phase diagram in the J-V plane by integrating perturbative renormalization-group equa...

Orignac, E

2003-01-01

378

Decoupling of the S=1/2 antiferromagnetic zig-zag ladder with anisotropy  

International Nuclear Information System (INIS)

The spin-1/2 antiferromagnetic zig-zag ladder is studied by exact diagonalization of small systems in the regime of weak interchain coupling. A gapless phase with quasi-long-range spiral correlations has been predicted to occur in this regime if easy-plane (XY) anisotropy is present. We find in general that the finite zig-zag ladder shows three phases: a gapless collinear phase, a dimer phase, and a spiral phase. We study the level crossings of the spectrum, the dimer correlation function, the structure factor, and the spin stiffness within these phases, as well as at the transition points. As the interchain coupling decreases we observe a transition in the anisotropic XY case from a phase with a gap to a gapless phase that is best described by two decoupled antiferromagnetic chains. The isotropic and the anisotropic XY cases are found to be qualitatively the same, however, in the regime of weak interchain coupling for the small systems studied here. We attribute this to a finite-size effect in the isotropic zig-zag case that results from exponentially diverging antiferromagnetic correlations in the weak-coupling limit

2001-06-01

379

Charge ordering in quarter-filled ladder systems coupled to the lattice  

CERN Document Server

We investigate charge ordering in the presence of electron-phonon coupling for quarter-filled ladder systems by using Exact Diagonalization. As an example we consider NaV2O5 using model parameters obtained from first-principles band-structure calculations. The relevant Holstein coupling to the lattice considerably reduces the critical value of the nearest-neighbor Coulomb repulsion at which formation of the zig-zag charge-ordered state occurs, which is then accompanied by a static lattice distortion. Energy and length of a kink-like excitation on the background of the distorted lattice are calculated. Spin and charge spectra on ladders with and without static distortion are obtained, and the charge gap and the effective spin-spin exchange parameter J are extracted. J agrees well with experimental results. Analysis of the dynamical Holstein model, restricted to a small number of phonons, shows that low frequency lattice vibrations increase the charge order, accompanied by dynamically produced zig-zag lattice d...

Aichhorn, M; Sherman, E Y; Spitaler, J; Ambrosch-Draxl, C; Evertz, H G

2004-01-01

380

Fabrication of nanochannels with ladder nanostructure at the bottom using AFM nanoscratching method  

Science.gov (United States)

This letter presents a novel atomic force microscopy (AFM)-based nanomanufacturing method combining the tip scanning with the high-precision stage movement to fabricate nanochannels with ladder nanostructure at the bottom by continuous scanning with a fixed scan size. Different structures can be obtained according to the matching relation of the tip feeding velocity and the precision stage moving velocity. This relationship was first studied in detail to achieve nanochannels with different ladder nanostructures at the bottom. Machining experiments were then performed to fabricate nanochannels on an aluminum alloy surface to demonstrate the capability of this AFM-based fabrication method presented in this study. Results show that the feed value and the tip orientation in the removing action play important roles in this method which has a significant effect on the machined surfaces. Finally, the capacity of this method to fabricate a large-scale nanochannel was also demonstrated. This method has the potential to advance the existing AFM tip-based nanomanufacturing technique of the formation these complex structures by increasing the removal speed, simplifying the processing procedure and achieving the large-scale nanofabrication.

Yan, Yongda; Geng, Yanquan; Hu, Zhenjiang; Zhao, Xuesen; Yu, Bowen; Zhang, Qi

2014-05-01

 
 
 
 
381

The Spin Dynamics of the Spin Ladder, Dimer Chain Material $Sr_{14}Cu_{24}O_{41}$  

CERN Document Server

We have performed inelastic neutron scattering on a single crystal sample of Sr14Cu24O41 to study the spin dynamics of the Cu2O3 spin ladder layers, and CuO2 chains. Data collected with incident energies of 50 meV, 200 meV, 350 meV and 500 meV are best fitted with a dispersion with a spin gap of 32.5+/-0.1 meV and a maximum of 193.52.4 meV, consistent with a coupling along the ladders, J|| = 130 meV and a rung coupling J^=72 meV. We find that excitations with an energy transfer of approximately 11.5 meV can be described solely in terms of a dimer chain with an antiferromagnetic intra-dimer coupling, J1 = 11.2 meV, between next-nearest-neighbour Cu ions and a ferromagnetic inter-dimer coupling, J2 = -1.1 meV. The dimers are separated by two Cu ions providing a periodicity for the dimer chain of five units.

Eccleston, R S; Akimitsu, J; Eisaki, H; Motoyama, N; Uchida, S I; Eccleston, Roger S; Uehara, Masatomo; Akimitsu, Jun; Eisaki, Hiroshi; Motoyama, Naoki; Uchida, Shin-ichi

1998-01-01

382

Quantum Magnetism of Spin-Ladder Compounds with Trapped-Ion Crystals  

CERN Multimedia

The quest for experimental platforms that allow for the exploration, and even control, of the interplay of low dimensionality and frustration is a fundamental challenge in several fields of quantum many-body physics, such as quantum magnetism. Here, we propose the use of cold crystals of trapped ions to study a variety of frustrated quantum spin ladders. By optimizing the trap geometry, we show how to tailor the low dimensionality of the models by changing the number of legs of the ladders. Combined with a method for selectively hiding of ions provided by laser addressing, it becomes possible to synthesize stripes of both triangular and Kagome lattices. Besides, the degree of frustration of the phonon-mediated spin interactions can be controlled by shaping the trap frequencies. We support our theoretical considerations by initial experiments with planar ion crystals, where a high and tunable anisotropy of the radial trap frequencies is demonstrated. We take into account an extensive list of possible error sou...

Bermudez, A; Ott, K; Kaufmann, H; Ulm, S; Schmidt-Kaler, F; Retzker, A; Plenio, M B

2012-01-01

383

Inverse scattering transform for the nonlinear Schrödinger system on a zigzag-runged ladder lattice  

Science.gov (United States)

A detailed description of four-component nonlinear Schrödinger system on zigzag-runged ladder lattice is given. In order to support the equivalence between the two pairs of field amplitudes, we introduce the two sets of auxiliary linear problems, allowing one to develop the inverse scattering technique in the most adequate symmetrical form. The two complementary sets of discrete Marchenko equations are derived and their multisoliton solutions for the true reflectionless field amplitudes are found. The dispersion relations for the diagonal elements of reduced monodromy matrices are obtained. We explicitly present the simplest realization of soliton dynamics corresponding to the time-independent intersite coupling parameters and zero Peierls phases and show that the two-site structure of the lattice unit cell is strictly manifested as the two splitted branches of soliton excitations. In the general case of time-dependent intersite coupling parameters and nonzero Peierls phases, the theory is capable to model the dynamics of parametrically driven nonlinear ladder systems subjected to external magnetic field.

Vakhnenko, Oleksiy O.

2010-10-01

384

Magnetic excitations and phase diagram of the spin ladder material (Hpip)2CuCl4  

International Nuclear Information System (INIS)

Full text: One-dimensional model magnets show generic features of low-dimensional systems with strong fluctuations. These enable important benchmark comparisons between experimental results and theoretical predictions. (Hpip)2CuCl4 is one of these materials, a 2 legged quasi-1D spin ladder compound, where the entire phase diagram is accessible, allowing for rich experiments in the plethora of phases. With rung and leg couplings of Jr=3.1 K and Jl=1.5 K respectively, comparisons can be made to the prototypical spin ladder (Hpip)2CuBr4 (Jr=12.8 K, Jl=3.2 K) which has considerably stronger exchange. Using neutron diffraction and inelastic scattering experiments, we determined the crystal structure as a function of temperature, the spin Hamiltonian and the the exchange parameters for(Hpip)2CuCl4. The phase diagram is explored via a temperature and field dependent study of the specific heat and is found to show the same phases and quantum critical points, except for a smaller coupling ratio Jr/Jl (weak coupling). We also explore the elementary excitations of the system by INS, which shows commensurate magnon modes with an energy gap Eg=0.18 meV. (author)

2011-06-15

385

Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation  

Energy Technology Data Exchange (ETDEWEB)

We include a generalized infinite class of quark-gluon vertex dressing diagrams in a study of how dynamics beyond the ladder-rainbow truncation influences the Bethe-Salpeter description of light quark pseudoscalar and vector mesons. The diagrammatic specification of the vertex is mapped into a corresponding specification of the Bethe-Salpeter kernel, which preserves chiral symmetry. This study adopts the algebraic format afforded by the simple interaction kernel used in previous work on this topic. The new feature of the present work is that in every diagram summed for the vertex and the corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be the self-consistent vertex solution. We also adopt from previous work the effective accounting for the role of the explicitly non-Abelian three gluon coupling in a global manner through one parameter determined from recent lattice-QCD data for the vertex. With the more consistent vertex used here, the error in ladder-rainbow truncation for vector mesons is never more than 10% as the current quark mass is varied from the u/d region to the b region.

Hrayr Matevosyan; Anthony Thomas; Peter Tandy

2007-04-01

386

Fish barriers  

International Nuclear Information System (INIS)

In addition to literature reviews laboratory experiments with both strobe light and different kinds of sound stimuli were carried out. In the experiments silver eel, brown trout, arctic char and salmon smolts were tested. The experiments showed that in darkness silver eel avoided strobe light with intensities between 0.4 and 8.7 lux with 80-90% avoidance in 8.7 lux. The avoidance reactions decreased when background light was raised to 9 lux. Brown trout did not show as strong avoidance reactions possibly due to aggressive behaviour between different individuals of brown trout. The avoidance reaction was however more pronounced in dim background lift with an intensity of 5 lux than in darkness. The experiments also showed that the avoidance reactions started within a few seconds after exposure to strobe light. The frequencies 6.0 and 15 Hz were more effective as triggers of avoidance reactions than were the frequencies 2.1 and 160 Hz. Arctic char did not show any avoidance reactions to strobe light. It was actually attracted to strobe light with the frequency 160 Hz in total darkness and indifferent in dim background light 10 lux. Experiments in running water also showed that salmon smolts could be diverted from an area exposed to strobe light with the frequency 15.0 Hz. The effect was more pronounced in darkness than in dim background light and also more pronounced when water current was 20 cm/s than when it was 40 or 60 cm/s. Experiments to test the avoidance reactions to sound was also performed. The evaluation of these results where however complicated by the fact that the fishes swam rapidly to and fro in the experimental chamber and thus by pure chance very frequently were close to the sound generator

1992-01-01

387

Australian Museum Fish Site  

Science.gov (United States)

Recently redesigned, the Australian Museum Fish Site contains a host of resources for researchers, students, and interested visitors. The heart of the site is the Find a Fish section, a collection of hundreds of fact sheets on fish, sorted by common or scientific name. Each fact sheet includes a quick overview, one or more images, and suggestions for further reading. Visitors can also identify fish pictorially using the Identify a Fish section, which links back to the fact sheets. Other offerings include further information on the Museum's fish department, a student section, some short underwater movies, related links, a FAQ, and an internal search engine.

388

Augmented Fish Health Monitoring, 1992 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

The Augmented Fish Health Monitoring Project (Project) had its origin, in the mid-1980's, in perceived differences or inconsistencies in fish disease detection, diagnosis and control capabilities between the five conservation agencies rearing and releasing anadromous salmonids for fishery resource management and mitigation purposes in the Columbia River basin. Agency fish health programs varied greatly. Some agencies had personnel, equipment and funding to frequently monitor the health status of both juvenile production fish and adult salmon or steelhead trout at the time of spawning. Other agencies had much smaller programs and limited resources. These differences became better understood when the Pacific Northwest Fish Health Protection Committee developed its Model Fish Health Protection Program including recommendations for standard fish disease detection procedures. Even though some agencies could not immediately attain the goals set by the Model Program it was unanimously adopted as a desirable objective. Shortly thereafter, a multi-party planning group was assembled to help the Bonneville Power Administration (BPA) find ways to improve agency fish health programs and implement measures under the Fish and Wildlife Program of the Northwest Power Planning Council. The planning group assessed existing agency fish health monitoring capabilities, agreed upon satisfactory levels of capability to detect and identify important fish pathogens, and designed a five-year project establishing comparable fish health monitoring capability in each agency. It was strongly believed that such a project would improve the health and quality of the millions of hatchery fish released annually in the Columbia River basin and improve interagency communications and disease control coordination. During 1986 and 1987 BPA individually negotiated five separate contracts with the fishery agencies to standardize fish health monitoring, develop a common data collection and reporting format, evaluate and monitor hatchery water supplies, improve communications and coordination, and provide a mechanism for periodic review. The contract with the U. S. Fish and Wildlife Service was approved on May 31, 1987, the last of the five inter-agency agreements to be signed. This did not delay Service participation with the other agencies because the Service already had many elements of the Project in place under its existing Service-wide fish health policy and implementation plan, The Service fully participated in the Project from mid-1987 through mid-1992. This completion report describes some of the many accomplishments under each of the objectives, benefits accruing from the Project, elements to be sustained by the Service after the Project ended, and Project that were not completed or that pointed out new work that needs to be done.

Warren, James W.

1992-08-01

389

Environmental mitigation at hydroelectric projects. Volume 2, Benefits and costs of fish passage and protection  

Energy Technology Data Exchange (ETDEWEB)

This study examines envirorunental mitigation practices that provide upstream and downstream fish passage and protection at hydroelectric projects. The study includes a survey of fish passage and protection mitigation practices at 1,825 hydroelectric plants regulated by the Federal Energy Regulatory Commission (FERC) to determine frequencies of occurrence, temporal trends, and regional practices based on FERC regions. The study also describes, in general terms, the fish passage/protection mitigation costs at 50 non-Federal hydroelectric projects. Sixteen case studies are used to examine in detail the benefits and costs of fish passage and protection. The 16 case studies include 15 FERC licensed or exempted hydroelectric projects and one Federally-owned and-operated hydroelectric project. The 16 hydroelectric projects are located in 12 states and range in capacity from 400 kilowatts to 840 megawatts. The fish passage and protection mitigation methods at the case studies include fish ladders and lifts, an Eicher screen, spill flows, airburst-cleaned inclined and cylindrical wedgewire screens, vertical barrier screens, and submerged traveling screens. The costs, benefits, monitoring methods, and operating characteristics of these and other mitigation methods used at the 16 case studies are examined.

Francfort, J.E.; Rinehart, B.N.; Sommers, G.L. [EG and G Idaho, Inc., Idaho Falls, ID (United States); Cada, G.F.; Jones, D.W. [Oak Ridge National Lab., TN (United States); Dauble, D.D. [Pacific Northwest Lab., Richland, WA (United States); Hunt, R.T. [Hunt (Richard) Associates, Inc., Concord, NH (United States); Costello, R.J. [Northwest Water Resources Advisory Services (United States)

1994-01-01

390

Contribution of experimental fluid mechanics to the design of vertical slot fish passes Contribution de la mécanique des fluides expérimentale à la conception des passes à poissons à fentes verticales  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the main results of an experimental study of mean and turbulent characteristics of flow in a scale model of a vertical slot fish pass with varying width and slope (from 5% to 15%. Experimental hydraulic modelling was combined with the study of fish behaviour in the model. The discharge coefficient, which significantly affects the design of such facilities, varied from 0.67 to 0.89 and was strongly influenced by the slope. Two distinct flow patterns were observed, depending on the slope and the fish pass width. The point of transition between the two states was determined. Low velocity areas are likely resting zones for fish and particular attention was paid to evaluating these areas. Slope was found to affect both the volume of the low velocity zone, and the value of turbulent kinetic energy in these areas. The statistical characteristics of turbulent kinetic energy in the pools were linked primarily to the maximum velocity in the jet. An analysis of the behaviour of juvenile brown trout (Salmo trutta in the scale model clearly showed that the fish avoided the areas of high velocities in the jet, except at the slot itself where they took advantage of the jet’s non-stationary character. Low-velocity areas were not frequented uniformly by fish, which stayed most frequently in the zone located just downstream from the slot and behind the small side baffle. It is suggested that future studies might investigate lower pool-length to slot-width ratios, which might make it possible to increase the slope significantly and should also examine ways of improving hydraulic conditions for fish by carefully distributing obstacles in pools. Cet article présente les résultats d’une étude expérimentale sur les caractéristiques moyennes et turbulentes de l’écoulement dans une passe à fentes verticales de pente variant de 5 % à 15 % et de largeur variable. L’étude hydraulique a été complétée par l’observation du comportement du poisson sur le modèle. Les valeurs du coefficient de débit intervenant dans le dimensionnement des passes varient de 0,67 à 0,89 et sont très sensibles à la pente. La transition entre les deux configurations de l’écoulement observées a été déterminée, en fonction de la pente et de la largeur. Les caractéristiques de l’énergie cinétique turbulente, en particulier dans les zones à faibles vitesses, ont été déterminées. La pente affecte à la fois le volume des zones à faible vitesse et la valeur de l’énergie cinétique turbulente dans ces zones qui sont susceptibles de servir de zone de repos aux poissons. Les caractéristiques statistiques de l’énergie cinétique dans les bassins sont avant tout liées à la vitesse maximale dans le jet. L’analyse du comportement de juvéniles de truites (Salmo trutta dans le modèle montre très clairement que le poisson évite les zones à fortes vitesses, en particulier le jet, sauf évidemment au niveau de la fente qu’il franchit en mettant à profit le caractère instationnaire du jet. Les zones à faibles vitesses ne sont pas fréquentées de façon identique, le poisson utilisant pour stationner le plus fréquemment la zone située à l’aval du déflecteur de paroi. Les résultats et la discussion suggèrent que les études futures portent sur des rapports de forme longueur de bassin sur largeur de fente plus faibles pour augmenter la pente des ouvrages de façon significative et se poursuivent sur l’amélioration des conditions d’écoulement par la mise en place d’obstacles dans les bassins.

Wang R.W.

2010-02-01

391

Evaluation of a Multiplex PCR Assay (Bruce-ladder) for Molecular Typing of All Brucella Species, Including the Vaccine Strains? †  

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An evaluation of a multiplex PCR assay (Bruce-ladder) was performed in seven laboratories using 625 Brucella strains from different animal and geographical origins. This robust test can differentiate in a single step all of the classical Brucella species, including those found in marine mammals and the S19, RB51, and Rev.1 vaccine strains.

2008-01-01

392

Using Task Data in Diagnostic Radiology. Research Report No. 8. Volume 1. Job Ladders: Assigning Tasks to Jobs.  

Science.gov (United States)

This report on the results of the application of the Health Services Mobility Study (HSMS) task analysis method in diagnostic radiology describes several career ladders starting from the aide level in quality assurance or patient care, rising to the technician level, and then on to the radiologic technologist level, with options to continue to…

Gilpatrick, Eleanor

393

Charge density wave in the spin ladder of Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$  

CERN Multimedia

We consider a multiband charge transfer model for a single spin ladder describing the holes in Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$. Using Hartree-Fock approximation we show how the charge density wave, with its periodicity dependent on doping as recently observed in the experiment, can be stabilized by purely electronic many-body interactions.

Wohlfeld, K; Sawatzky, G A; Wohlfeld, Krzysztof; Oles, Andrzej M.; Sawatzky, George A.

2006-01-01

394

THE PAN-STARRS 1 PHOTOMETRIC REFERENCE LADDER, RELEASE 12.01  

Energy Technology Data Exchange (ETDEWEB)

As of 2012 January 21, the Pan-STARRS 1 3{pi} Survey has observed the 3/4 of the sky visible from Hawaii with a minimum of 2 and mean of 7.6 observations in five filters, g {sub P1}, r {sub P1}, i {sub P1}, z {sub P1}, y {sub P1}. Now at the end of the second year of the mission, we are in a position to make an initial public release of a portion of this unprecedented data set. This article describes the PS1 Photometric Ladder, Release 12.01. This is the first of a series of data releases to be generated as the survey coverage increases and the data analysis improves. The Photometric Ladder has rungs every hour in right ascension and at four intervals in declination. We will release updates with increased area coverage (more rungs) from the latest data set until the PS1 survey and the final re-reduction are completed. The currently released catalog presents photometry of {approx}1000 objects per square degree in the rungs of the ladder. Saturation occurs at g {sub P1}, r {sub P1}, i {sub P1} {approx} 13.5; z {sub P1} {approx} 13.0; and y {sub P1} {approx} 12.0. Photometry is provided for stars down to g {sub P1}, r {sub P1}, i {sub P1} {approx} 19.1 in the AB system. This data release depends on the rigid 'Ubercal' photometric calibration using only the photometric nights, with systematic uncertainties of (8.0, 7.0, 9.0, 10.7, 12.4) mmag in (g {sub P1}, r {sub P1}, i {sub P1}, z {sub P1}, y {sub P1}). Areas covered only with lower quality nights are also included, and have been tied to the Ubercal solution via relative photometry; photometric accuracy of the non-photometric regions is lower and should be used with caution.

Magnier, E. A.; Tonry, J. L.; Burgett, W. S.; Chambers, K. C.; Flewelling, H. A.; Kaiser, N.; Kudritzki, R.-P.; Morgan, J. S.; Sweeney, W. E. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Schlafly, E.; Finkbeiner, D.; Juric, M.; Stubbs, C. W. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Price, P. A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2013-04-01

395

Fish Breeding in Nigeria  

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Full Text Available Fish breeding is a very important activity ensuring availability of fingerlings for the stocking of ponds, pens, tanks and cages. The breeding habits of fishes in nature differ from specie to specie Different species of fish choose different places in the aquatic environment for breeding. Most species do not breed when in captivity due to a number of factors. In Nigeria, induced breeding of African mud catfish through injection of ova prim hormone or pituitary gland is the main practice. This article reviews the wild sources of fish seeds, some cultivable fishes. carp breeding, relationship between the endocrine system and gonad development, function of the Central Nervous System (CNS in propagation, influence of ecological conditions on gonad development, artificial propagation of common carp, natural induced spawning, salmon culture and an innovation in the sea to educate fish breeders, fish genetics and fish culturist in other to facilitate their productivity.

J.A. Akankali

2011-06-01

396

Medusivorous fishes, a review  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A preliminary review is presented of fish species having consumed pelagic Cnidaria (Scyphozoa and Hydrozoa) as well as Ctenophora. Quantitative data are scarce. Knowledge of morphological and physiological adaptations of fishes foraging on gelatinous plankton is almost non-existent.

1988-01-01

397

Flashlight Fish Symbiosis.  

Science.gov (United States)

This project investigates the symbiosis between anomalopids (flashlight fishes) and their luminous bacteria symbionts. Anomalopid fishes harbor luminous bacterial symboints in large light organs located beneath the eyes. This association is one of the mos...

M. G. Haygood

1990-01-01

398

River Tees fish counts  

Details of monthly upstream counts of migratory salmonids (salmon and sea trout) from the Environment Agency fish counter on the River Tees. These data will be updated regularly. Related Searches: tees fish counter

399

Sugarcane Fish Silage Fermentation.  

Science.gov (United States)

UNIDO pub on sugar cane fish silage fermentation covers (1) attempts to ensile sugar cane for feed production; relevant research (2) the incorporation of fish in the fermentation with animal droppings as inoculum, redirecting the fermentation to produce h...

D. A. Ali N. Samaroo L. A. Shah

1985-01-01

400

Acoustic Telemetry from Fish.  

Science.gov (United States)

Methods are described for monitoring physiological parameters such as temperature and electrocardiogram from free swimming fish. Information is telemetered as sound radiating from an acoustic transmitter implanted on the fish. Limitations of the technique...

J. Kanwisher K. Lawson G. Sundnes

1973-01-01