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Sample records for foliosus dc asteraceae

  1. Estudo fitoquímico da espécie Pterocaulon interruptum DC. (Asteraceae Phytochemical study of Pterocaulon interruptum Dc., Asteraceae

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    Ana Carolina Winkler Heemann

    2006-12-01

    Full Text Available A análise fitoquímica das partes aéreas de Pterocaulon interruptum DC. (Asteraceae resultou no isolamento de cinco compostos: uma cumarina, sabandinol, dois esteróides, estigmasterol e 3-O-acetil-taraxasterol e dois flavonóides, quercetina e taxifolina 7-O-prenilada. As estruturas destas substâncias foram estabelecidas por análises espectroscópicas, sendo que este é o primeiro trabalho sobre o isolamento destes compostos em Pterocaulon interruptum DC.Chemical investigation of the aerial parts of Pterocaulon interruptum DC., Asteraceae, resulted in the isolation of five compounds: one coumarin, sabandinol, two steroids, stigmasterol and 3-O-acetyl taraxasterol and two flavonoids, quercetin (flavonol and 7-O-prenyl taxifolin (dihydroxyflavonol. The structures of these compounds were established by spectroscopic analysis. This paper deals with the first report of these compounds in Pterocaulon interruptum DC.

  2. Achyrocline satureioides (Lam.) DC., Asteraceae: development of granules from spray dried powder

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    Petrovick,Gustavo F.; Pedro R. Petrovick; Valquiria L. Bassani

    2010-01-01

    Achyrocline satureioides (Lam.) DC., Asteraceae, is a herbal specie widely used in folk medicine in the south of Brazil, Uruguay, Argentina and Paraguay. The technological characteristics of an Achyrocline satureioides spray dried extract powder, produced in semi-industrial scale, as well as the feasibility of the granules are reported in the present work. The spray dried powder was characterized as a fine powder consisting of small spherical particles with rough and porous surface. The Hausn...

  3. New species and nomenclatural action in Saussurea DC.(Asteraceae)

    Institute of Scientific and Technical Information of China (English)

    You-Sheng CHEN; Qi-Liang GAN

    2011-01-01

    @@ Saussurea zhuxiensis Y.S.Chen & Q.L.Gan, sp.nov. 竹溪风毛菊 (S1-1.Figs.1, 2) Type: China.Hubei: Zhuxi County, Shuangqiao, rock crevices along stream, alt.900 m, 2006-08-09, Q.L.Gan 1508 (PE). Latin diagnosis: Species Saussurea salicifoliae DC.similis, a qua radicibus numerosis fibrosis, foliis inferioribus parce dentatis vel incisis, laminis abaxialibus pallidis viridibus, capitulis laxioribus differt.

  4. Achyrocline satureioides (lam.) dc., asteraceae : development of granules from spray dried powder

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    Petrovick, Gustavo Freire; Petrovick, Pedro Ros; Bassani, Valquiria Linck

    2010-01-01

    Achyrocline satureioides (Lam.) DC., Asteraceae, é uma planta amplamente utilizada na medicina popular no sul do Brasil, Uruguai, Argentina e Paraguai. As características tecnológicas do extrato seco por aspersão de Achyrocline satureioides, produzido em escala semi-industrial, assim como a viabilidade da produção de granulados são relatadas no presente trabalho. O extrato seco por aspersão foi caracterizado como um pó fino, composto por pequenas partículas esféricas com superfície rugosa e p...

  5. Atividades antiúlcera e antioxidante Baccharis trimera (Less DC (Asteraceae Antiulcerogenic and antioxidant activities of Baccharis trimera (Less DC (Asteraceae

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    Larissa Funabashi de Toledo Dias

    2009-03-01

    Full Text Available A "carqueja", Baccharis trimera (Less DC (Asteraceae, é uma espécie vegetal característica de regiões tropicais, muito utilizada na medicina popular como antiinflamatória, hipoglicemiante e em tratamento de problemas digestivos. A avaliação da atividade antiúlcera do extrato bruto liofilizado e do extrato liofilizado da "resina" (porção que durante a concentração dos extratos ficava depositada no fundo do recipiente com aspecto viscoso e pegajoso foi realizada através de indução aguda por etanol acidificado. O extrato bruto liofilizado, na dose de 400 mg/ kg, reduziu a área de lesão em 90%, 200 mg/kg, 87%, 100 mg/kg, 66% e o fármaco controle (lansoprazol, 66%. O extrato liofilizado da "resina", administrado na dose de 400 mg/kg, reduziu a área de lesão em 82%, 200 mg/kg, 82%, 100 mg/kg, 53% e o fármaco controle (lansoprazol, 70%. A atividade antioxidante foi ensaiada com extrato bruto liofilizado, extrato liofilizado da "resina", pó da droga e frações clorofórmica, acetato de etila, etanol e etanol 50% através do método que reduz o radical 2,2'-difenil-1-picril-hidrazil (DPPH, permitindo após o equilíbrio da reação, calcular a quantidade de antioxidante gasta para reduzir 50% do DPPH, apresentando resultado evidente, comparado à vitamina E. Não foram verificados sinais de alteração aparente no ensaio de toxicidade na dose única de 5g/kg, em camundongos.Baccharis trimera (Less DC (Asteraceae is a medicinal Brazilian plant well-known by "carqueja". Natural from tropical regions, used as home-made medicine as anti-inflammatory, hypoglycemiant and for the treatment of digestive problems. The evaluation of the antiulcer activity of the extract and the "resin" (portion which during the extracts concentration was settled at the bottom of the recipient, showing a viscous and clammy aspect, was accomplished through the acute induction by acidified ethanol. The lyophilized extract, at a dose of 400 mg/kg, reduced the

  6. Estudo farmacobotânico de partes vegetativas aéreas de Baccharis anomala DC., Asteraceae Pharmacobotanical study of aerial vegetative parts of Baccharis anomala DC., Asteraceae

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    Jane M. Budel

    2008-12-01

    Full Text Available O gênero Baccharis pertence à família Asteraceae e se destaca por incluir espécies medicinais. Baccharis anomala DC., conhecida como "uva-do-mato" e "cambará-de-cipó", é utilizada popularmente como diurético e estudos fitoquímicos constataram a presença de taninos e saponinas. Este trabalho objetivou realizar estudo farmacobotânico de folha e caule dessa espécie. O material foi submetido a microtécnicas fotônica e eletrônica de varredura usuais. A lâmina foliar possui epiderme uniestratificada revestida por cutícula delgada e estriada. Estômatos anomocíticos ocorrem somente na face abaxial. Em ambas as faces aparecem dois tipos de tricomas tectores pluricelulares unisseriados, um com ápice agudo e outro com célula apical flageliforme. O mesofilo é isobilateral e a nervura central é plano-convexa, sendo percorrida por um feixe vascular colateral. O pecíolo mostra três feixes vasculares que se dispõem em arco aberto. O caule tem secção circular e epiderme unisseriada, com tricomas similares aos da folha. Colênquima angular e clorênquima alternam-se no córtex e fibras perivasculares apõem-se ao floema. Evidencia-se uma zona cambial, cujas células formam xilema no sentido centrípeto e floema, centrifugamente, e a medula compõe-se de células parenquimáticas. Dutos secretores acompanham o sistema vascular na folha e no caule.The genus Baccharis belongs to the family Asteraceae and includes medicinal species. Baccharis anomala DC., popularly known as "uva-do-mato" and "cambará-do-cipó" in Portuguese, is used as diuretic in folk medicine and phytochemical studies have demonstrated the presence of tannins and saponins. This work has aimed at studying the macro and microscopic aspects of the leaf and stem of this species. The botanical material was prepared according to standard light and scanning microtechniques. The leaf blade has uniseriate epidermis coated with a thin and striate cuticle. Anomocytic stomata are

  7. Achyrocline satureioides (Lam. DC., Asteraceae: development of granules from spray dried powder

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    Gustavo F. Petrovick

    2010-11-01

    Full Text Available Achyrocline satureioides (Lam. DC., Asteraceae, is a herbal specie widely used in folk medicine in the south of Brazil, Uruguay, Argentina and Paraguay. The technological characteristics of an Achyrocline satureioides spray dried extract powder, produced in semi-industrial scale, as well as the feasibility of the granules are reported in the present work. The spray dried powder was characterized as a fine powder consisting of small spherical particles with rough and porous surface. The Hausner's factor, Carr's index, and densification index of the spray dried powder were, respectively, 1,23, 18,9%, and 27,2 mL, characterizing it as a poor flow and low density powder. The preparation of granules from this spray dried powder, through dry disaggregation method, yielded irregularly shaped granules, with a rough surface, but with better flow and compactability characteristics. These granules presented a Hausner's factor, a Carr's index, and a densification index of, respectively, 1,09, 8,16%, and 12,33 mL. The LC assay of the main polyphenols, quercetin, luteolin, and 3-O-methylquercetin revealed that the granulation process did not changed the quantitative and qualitative profile of these constituents originally present in the spray dried powder. The comparative evaluation of the physical stability of both the spray dried powder and the granules, under relative humidity conditions of 65% and 99%, showed an expressive reduction in the humidity sorption on the granules as compared to the spray dried powders.Achyrocline satureioides (Lam. DC., Asteraceae, é uma planta amplamente utilizada na medicina popular no sul do Brasil, Uruguai, Argentina e Paraguai. As características tecnológicas do extrato seco por aspersão de Achyrocline satureioides, produzido em escala semi-industrial, assim como a viabilidade da produção de granulados são relatadas no presente trabalho. O extrato seco por aspersão foi caracterizado como um pó fino, composto por

  8. Acanthospermum hispidum DC (Asteraceae): perspectives for a phytotherapeutic product Acanthospermum hispidum DC (Asteraceae): perspectivas para um produto fitoterápico

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    Araújo,Evani de L.; Karina P. Randau; José G. Sena-Filho; Rejane M. Mendonça Pimentel; Haroudo S. Xavier

    2008-01-01

    The "Espinho-de-cigano" plant (Acanthospermum hispidum DC) is used throughout northeastern (NE) Brazil as a folk medicine for asthma. Although little is actually known about the effectiveness and safety of this plant extract product, it is possible to find numerous medicines prepared from it in public health services or in stores selling natural products. This study aimed to undertake a literature review relative to Acanthospermum hispidum covering the period between 1926-2006 within the area...

  9. Acanthospermum hispidum DC (Asteraceae: perspectives for a phytotherapeutic product Acanthospermum hispidum DC (Asteraceae: perspectivas para um produto fitoterápico

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    Evani de L. Araújo

    2008-12-01

    Full Text Available The "Espinho-de-cigano" plant (Acanthospermum hispidum DC is used throughout northeastern (NE Brazil as a folk medicine for asthma. Although little is actually known about the effectiveness and safety of this plant extract product, it is possible to find numerous medicines prepared from it in public health services or in stores selling natural products. This study aimed to undertake a literature review relative to Acanthospermum hispidum covering the period between 1926-2006 within the areas of ethnobotany, phytochemistry and pharmacology. The objective was to contribute to a better knowledge of this species and its uses, as well as to aid in improving its performance as a natural medicine. The species is easily identifiable and grows abundantly during the rainy seasons in NE Brazil; is amenable to cultivation without lose of its phytochemical profile, and toxicological studies have showed its safety as a medicine (although more studies will be required in that direction. As such, the compilation of the accumulated knowledge concerning this species will aid in evaluating its pharmacological value, guaranteeing quality control of the final product, and in preparing recommendations for usages and dosages that offer both safety and efficiency to the user.A planta "Espinho-de-cigano" (Acanthospermum hispidum DC é amplamente usada no nordeste do Brasil como medicamento popular para a asma. Embora muito pouco seja conhecido atualmente sobre a eficácia e segurança deste extrato vegetal, é possível encontrar numerosos medicamentos preparados com ele nos serviços públicos ou em lojas que vendem produtos naturais. Este estudo visa proceder a uma revisão de literatura relativa à A. hispidum, no período entre 1926-2006, nas áreas de etnobotânica, fitoquímica e farmacologia. O objetivo foi contribuir para um melhor conhecimento desta espécie e seus usos, assim como auxiliar na melhora de seu desempenho como um medicamento natural. A espécie

  10. Combined treatment with caffeic and ferulic acid from Baccharis uncinella C. DC. (Asteraceae) protects against metabolic syndrome in mice.

    Science.gov (United States)

    Bocco, B M; Fernandes, G W; Lorena, F B; Cysneiros, R M; Christoffolete, M A; Grecco, S S; Lancellotti, C L; Romoff, P; Lago, J H G; Bianco, A C; Ribeiro, M O

    2016-03-01

    Fractionation of the EtOH extract from aerial parts of Baccharis uncinella C. DC. (Asteraceae) led to isolation of caffeic and ferulic acids, which were identified from spectroscopic and spectrometric evidence. These compounds exhibit antioxidant and anti-inflammatory properties and have been shown to be effective in the prevention/treatment of metabolic syndrome. This study investigated whether the combined treatment of caffeic and ferulic acids exhibits a more significant beneficial effect in a mouse model with metabolic syndrome. The combination treatment with caffeic and ferulic acids was tested for 60 days in C57 mice kept on a high-fat (40%) diet. The data obtained indicated that treatment with caffeic and ferulic acids prevented gain in body weight induced by the high-fat diet and improved hyperglycemia, hypercholesterolemia and hypertriglyceridemia. The expression of a number of metabolically relevant genes was affected in the liver of these animals, showing that caffeic and ferulic acid treatment results in increased cholesterol uptake and reduced hepatic triglyceride synthesis in the liver, which is a likely explanation for the prevention of hepatic steatosis. In conclusion, the combined treatment of caffeic and ferulic acids displayed major positive effects towards prevention of multiple aspects of the metabolic syndrome and liver steatosis in an obese mouse model.

  11. Análise morfoanatômica das partes aéreas de Wedelia paludosa DC. (Acmela brasiliensis, Sphagneticola trilobata, Asteraceae Morphoanatomic analysis of aerial parts of Wedelia paludosa DC. (Acmela brasiliensis, Sphagneticola trilobata, Asteraceae

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    Thaisa Baccarin

    2009-06-01

    Full Text Available O presente trabalho teve por objetivo o estabelecimento de parâmetros para análise morfo-anatômica das partes aéreas (caule e folhas da planta Wedelia paludosa DC., Asteraceae. A droga vegetal e o respectivo pó foram submetidos às análises macro e microscópica após preparação de lâminas semi-permanentes de cortes transversais e paradérmicos. O pó foi analisado após diafanização com cloral hidratado. É uma planta herbácea com caule castanho-avermelhado, folhas opostas, curto-pecioladas e membranáceas, apresentando pêlos nas duas faces, estreitada em direção à base acima do meio provida de dois pequenos lobos laterais e um terminal, maior e denteado. A planta apresenta secção circular de caule, que em crescimento primário, possui epiderme, colênquima angular, parênquima cortical e cilindro vascular, assim como oxalato de cálcio (várias drusas e alguns cristais prismáticos. A folha é simples, contendo tricomas tectores e estômato anomocítico. O mesofilo possui organização dorso-ventral e a nervura central, em corte transversal, apresenta-se côncavo-convexo com três feixes colaterais e presença de drusas de oxalato de cálcio nas células parenquimáticas. No pó obtido da droga vegetal foram verificadas as mesmas estruturas microscópicas observadas na droga vegetal rasurada. Os parâmetros morfo-anatômicos estabelecidos neste trabalho permitem o controle de qualidade macro e microscópico da planta tanto rasurada como na forma de pó.This study aimed to establish parameters for morphoanatomical analysis of the aerial parts (stem and leaves of the plant Wedelia paludosa DC., Asteraceae. The drug and its respective powder were characterized by macro and microscopic analysis after obtaining semi-permanent lamina of transverse and paradermal sections. The powder was analyzed after being cleared with chloral hydrate. It is an herbaceous plant with reddish-brown stems, opposite leaves, short-petiolated and

  12. Caracterização morfoanatômica das folhas de Eremanthus erythropappus (DC. MacLeisch, Asteraceae Leaf morpho-anatomical characterization of Eremanthus erythropappus (DC. MacLeisch, Asteraceae

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    Rafael C. Dutra

    2010-12-01

    Full Text Available Eremanthus erythropappus (DC. MacLeisch (Asteraceae, popularmente conhecida como "candeia-da-serra", é uma espécie utilizada na medicina tradicional como cicatrizante e antimicrobiano. O objetivo do presente trabalho foi comparar o número de tricomas glandulares nas folhas jovens e adultas de E. erythropappus, assim como realizar a caracterização morfoanatômica destas folhas. Secções transversais e paradérmicas das folhas foram submetidas às microtécnicas fotônicas e à microscopia eletrônica de varredura. A quantificação dos tricomas glandulares foi realizada em folhas jovens e adultas com auxílio de câmara clara. As folhas são alternas ou fasciculadas e a lâmina foliar possui epiderme uniestratificada, revestida por cutícula delgada e lisa e mesofilo dorsiventral. Em ambas as faces da epiderme, ocorrem estômatos predominantemente anomocíticos e tricomas glandulares inseridos em depressões. Na face abaxial observam-se numerosos tricomas tectores. O parênquima paliçádico é uniestratificado e o parênquima voltado para a face abaxial é formado por três a cinco camadas de células com disposição compacta. As folhas jovens e adultas apresentam respectivamente 21,78±5,83 e 17,80±6,69 tricomas glandulares na face adaxial. A análise morfoanatômica das folhas de E. erythropappus mostra-se um método rápido e prático para a identificação e controle de qualidade de espécies vegetais utilizadas na terapêutica.Eremanthus erythropappus (DC. MacLeisch (Asteraceae, commonly known as 'candeia-da-serra', is a plant used in folk medicine as wound healing and antimicrobial. The aim of this study was to compare the number of glandular trichomes between the young and the mature leaves, as well as to perform the morpho-anatomical characterization of E. erythropappus leaves. Transverse and paradermal sections of the leaves were prepared according to light and scanning microtechniques for the morpho-anatomical characterization

  13. Phenotypic traits variation among native diploid, native tetraploid and invasive tetraploid Senecio inaequidens DC. (Asteraceae

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    Monty, A.

    2010-01-01

    Full Text Available Senecio inaequidens DC. is a rapidly spreading plant invader in Europe. In its native range, it occurs at two co-existing diploid and tetraploid cytotypes. To date, only tetraploids are reported in Europe, even though invasive diploids were recorded in other parts of the world. We compared native diploid and both native and invasive tetraploid populations in common gardens in Europe for a suite of life history traits. Diploids were able to develop, showed high biomass production and produced more flower heads than tetraploids. In contrast, winter survival was null for diploids. It was low for native tetraploids, but reached 40% in invasive tetraploids. Results suggested that diploid cytotype tends to an annual life form when grown in Western Europe, with earlier and more abundant flowering. In contrast, the tetraploid cytotype was mainly perennial which may enhance its invasiveness.

  14. ANATOMY OF GYNURA AURANTIACA (BLUME SCH.BIP. EX DC. (ASTERACEAE

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    Rodica BERCU

    2014-06-01

    Full Text Available The paper presents a detailed histoanatomical description, of the vegetative organs (root, stem and leaf and photographs as well of Gynura aurantiaca (Blume Sch.Bip. ex DC. It was observed that the root have typical primary dictos structure. The stem has a differentiated in two regions cortex and the stele comprise one ring of open collateral vascular bundles with secondary xylem due to the cambium activity. The petiole anatomy is quite similar in its basic structure with the stem. The blade presents a heterogenous and hypostomatic mesophyll and a number of vascular bundles in the midrib zone. Remarkable is the presence of the filamentous, uniseriate non-glandular hairs in the stem, petiole and leaf blade. The mechanical tissue is present in the stem, petiole and blade as well.

  15. Germinação de aquênios de Baccharis dracunculifolia D.C.(Asteraceae Germination of Baccharis dracunculifolia D.C. (Asteraceae achene

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    Vania Gomes

    2002-10-01

    Full Text Available Baccharis dracunculifolia D. C. (Asteraceae é uma espécie arbustiva dióica que apresenta características invasoras e colonizadoras e potencial para recuperação de áreas degradadas. Estudou-se o comportamento germinativo de aquênios de Baccharis dracunculifolia recém coletados e estocados por um ano. Aquênios coletados em 1998 foram postos para germinar em quatro repetições de 25 aquênios nas temperaturas de 15º, 20º, 25º e 30ºC sob luz ou escuro contínuo, enquanto que os coletados em 1997 germinaram a 20º e a 25ºC. As médias de germinação e o índice de velocidade de emergência (IVE foram calculados para responder às seguintes perguntas: (a Como varia o comportamento germinativo dos aquênios de B. dracunculifolia sob diferentes condições de luz e temperatura? (b Existe relação entre o número total de aquênios germinados e o IVE? (c O armazenamento afeta as porcentagens de germinação? Os aquênios que germinaram a 15ºC na presença e na ausência de luz e a 20ºC na luz obtiveram porcentagens de germinação significativamente maiores que os aquênios que germinaram sob os demais tratamentos (p We studied the germination of Baccharis dracunculifolia (Asteraceae, achene, a species that has colonizing traits, which makes it a potential candidate for forest rehabilitation. Achenes were collected in 1998 and were germinated at 15º, 20º, 25º and 30ºC under continuous light, and darkness conditions with four replicates with 25 achenes in each. We had also collected achenes in 1997, ând they were germinated at 20º and 25ºC, under the same conditions. The mean germination rate and emergency velocity index (EVI were calculated to answer the following questions: (a How does the germination behavior of B. dracunculifolia's achenes vary under different temperature and light conditions? (b Is there any relationship between the total number of germinated achenes and the EVI? (c How does achene storage affect the

  16. Herbivoria em Erechtites valerinaefolia DC. (Asteraceae) : distribuição de ataque dos herbivoros e respostas compensatorias da planta

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    Yuriko Yanagizawa de Almeida Nogueira Pinto

    2000-01-01

    Resumo: As interações entre Erechtites valerianaefolia De. (Asteraceae) e herbívoros a ela associados foram estudadas de julho de 1991 a maio de 1993, na Serra do Japi, Jundiaí, SP, e de julho de 1992 a maio de 1993 na Fazenda Lageado, Botucatu, SP. Os principais objetivos foram testar as hipóteses que versam sobre a preferência dos herbívoros quanto ao tipo de plantas dentro de uma mesma população vegetal (Hipótese da Planta Vigorosa e Hipótese da Planta Estressada) e sobre as respostas comp...

  17. Antimicrobial Activity of Emilia sonchifolia DC., Tridax procumbens L. and Vernonia cinerea L. of Asteracea Family: Potential as Food Preservatives.

    Science.gov (United States)

    Yoga Latha, L; Darah, I; Sasidharan, S; Jain, K

    2009-09-01

    Chemical preservatives have been used in the food industry for many years. However, with increased health concerns, consumers prefer additive-free products or food preservatives based on natural products. This study evaluated antimicrobial activities of extracts from Emilia sonchifolia L. (Common name: lilac tassel flower), Tridax procumbens L. (Common name: tridax daisy) and Vernonia cinerea L. (Common name: Sahadevi), belonging to the Asteracea family, to explore their potential for use against general food spoilage and human pathogens so that new food preservatives may be developed. Three methanol extracts of these plants were tested in vitro against 20 bacterial species, 3 yeast species, and 12 filamentous fungi by the agar diffusion and broth dilution methods. The V. cinerea extract was found to be most effective against all of the tested organisms and the methanol fraction showed the most significant (p extracts determined by the broth dilution method ranged from 1.56 to 100.00mg/mL. The MIC of methanol fraction was the lowest in comparison to the other four extracts. The study findings indicate that bioactive natural products from these plants may be isolated for further testing as leads in the development of new pharmaceuticals in food preservation as well as natural plant-based medicine.

  18. Interferência de extratos da Baccharis dracunculifolia DC., Asteraceae, sobre a atividade de antibióticos usados na clínica Interference from extracts of Baccharis dracunculifolia DC., Asteraceae, on the activity of antibiotics used in the clinic

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    Marilde Canton

    2010-07-01

    Full Text Available O objetivo deste estudo foi investigar a interferência da fração polar e apolar, bem como do óleo essencial da Baccharis dracunculifolia DC., Asteraceae, sobre o efeito de antibióticos utilizados na clínica médica. Os ensaios foram realizados com vinte e nove antibióticos em associação com os dois extratos [uma fração polar (HA 50% e uma da fração apolar (EA 25%] e com o óleo essencial. O método utilizado foi o método de difusão em meio sólido utilizando os discos de antibióticos, adquiridos comercialmente. Os resultados mostraram interferência na ação esperada do antibiótico quando associado aos extratos e ao óleo essencial da B. dracunculifolia. Em alguns casos não houve alteração da ação do antibiótico, no entanto, na maioria dos casos houve interferência sinérgica ou antagônica da ação do antibiótico. Estes resultados mostram que o uso de produtos derivados de plantas pode em algumas situações interferir sobre a efetividade de antibióticos de uso no tratamento clínico.The objective of this study was to investigate the interference of the polar and apolar fraction as well the essential oil of Baccharis dracunculifolia DC., Asteraceae, about the antibiotics effects used in the medic clinic. The essays were accomplished with twenty nine antibiotics in association with two extracts [one polar fraction (HA 50% and one of apolar fraction (EA 25%] and with essential oil. The method used was the diffusion one in solid mean using the antibiotic discs, which were acquired commercially. The results showed interference in the hoped action of the antibiotic when associated to the extract and to the B. dracunculifolia essential oil. In some cases there was no alteration of the antibiotic action, however, in most of the cases there was either a synergic or an antagonic interference of the antibiotic action. These outcomes have showed that the use of derived products or plants can interfere on the effectiveness of

  19. Two new herb gall wasps from Spain, including the description of a new species of Aulacidea Ashmead, 1897 (Hymenoptera, Cynipidae, “Aylacini” inducing galls on Serratula nudicaulis L. DC (Asteraceae

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    Nieves-Aldrey, J. L.

    2012-12-01

    Full Text Available Two new species of herb gall wasps are recorded from Spain, which induce galls on flower heads of Serratula nudicaulis L. DC (Asteraceae. Isocolus serratulae (Mayr, 1882 is recorded for the first time in Spain, while a new species of Aulacidea Ashmead, 1897, Aulacidea pilarae sp. n., is described. This new species is similar to Aulacidea serratulae Diakontschuk, 1984, which is found throughout Oriental Europe. However, those two congeneric species may be distinguished by the morphology of the adults.Se citan dos nuevas especies de avispas de las agallas en plantas herbáceas para España. Las dos especies inducen agallas en cabezuelas florales de Serratula nudicaulis L. DC (Asteraceae y se han encontrado en el valle del Lozoya (Madrid, España Central. Isocolus serratulae (Mayr, 1882 se cita por primera vez para la Península Ibérica y se describe una especie nueva de Aulacidea Ashmead, 1897: A. pilarae sp. n. La nueva especie es similar a Aulacidea serratulae Diakontschuk, 1984 citada de Europa oriental, diferenciándose por la morfología de los adultos.

  20. Chemical Composition and Antimicrobial Activity of Essential Oils from the Aerial Parts of Asteriscus graveolens (Forssk.) Less. and Pulicaria incisa (Lam.) DC.: Two Asteraceae Herbs Growing Wild in the Hoggar.

    Science.gov (United States)

    Chaib, Faiza; Allali, Hocine; Bennaceur, Malika; Flamini, Guido

    2017-08-01

    In recent years, antimicrobial activities of essential oils have been intensively explored, mainly in researching and developing new antimicrobial agents to overcome microbial resistance. The present study investigates the chemical composition and antimicrobial activities of essential oils obtained from two Asteraceae: Asteriscus graveolens (Forssk.) Less. and Pulicaria incisa (Lam.) DC. Chemical analysis was performed using a combination of capillary GC-FID and GC/MS analytical techniques. The major component of Asteriscus graveolens were cis-chrysanthenyl acetate (31.1%), myrtenyl acetate (15.1%), and kessane (11.5%), while for Pulicaria incisa the main components were chrysanthenone (45.3%) and 2,6-dimethylphenol (12.6%). The oils obtained from the aerial parts were tested against sixteen microbial strains by agar well diffusion technique and dilution methods and showed minimum inhibitory concentrations (MIC) in the range of 19 - 1250 μg/ml. A good antibacterial activity against a common nosocomial pathogen, Acinetobacter baumanniiATCC 19606 was observed, especially from Pulicaria incisa essential oil, with a MIC value up to 19 μg/ml. These results give significant information about the pharmacological activity of these essential oils, which suggest their benefits to human health, having the potential to be used for medical purposes. © 2017 Wiley-VHCA AG, Zurich, Switzerland.

  1. In vitro antioxidant activities of Asteraceae Plants.

    Science.gov (United States)

    Vijaylakshmi, S; Nanjan, M J; Suresh, B

    2009-10-01

    Anaphalis neelgerriana DC and Cnicus wallichi DC belonging to the family Asteraceae (Compositae) are important medicinal plants indigenous to Nilgiris. Since the related species Anaphalis morrisonicola and Cnicus benedictus were reported for its anti cancer activities, the above mentioned plants were screened for Invitro antioxidant activity. In vitro antioxidant studies were carried out by DPPH, Nitric oxide and Hydrogen peroxide methods for the aerial part extracts of the plants. Different extracts were obtained from the aerial parts of the whole plant by successive solvent extraction and cold maceration process and subjected for Invitro antioxidant activity studies. Among the extracts tested, the ethyl acetate extract of Anaphalis neelgerriana DC and Cnicus wallchi DC showed significant anti oxidant activity in all the above methods. The potent ethyl acetate extract should be tested for anti oxidant activity in animal models.

  2. Pharmacognostical study of achenes of some plants from Asteraceae family

    Directory of Open Access Journals (Sweden)

    Y.O. Bychkova

    2014-04-01

    Full Text Available In the present paper are represented morphological studies on determination of weight of 1000 achenes, and sieve analysis of fruits of some plants from Asteraceae family (Arctium lappa L., Leuzea carthamoides (Willd. D.C, Inula helenium L., Echinacea purpurea Moench., Calendula officinalis L.. Lipid, alcohol-soluble and water-soluble complexes in fruits of C. officinalis were studied.

  3. Eupatorium rufescens y Vernonia oligactoides (Asteraceae, nuevas citas para la flora argentina

    Directory of Open Access Journals (Sweden)

    Álvaro J. Vega

    2008-01-01

    Full Text Available Se mencionan por primera vez para la flora argentina a Eupatorium rufescens Lund ex DC. y Vernonia oligactoides Less. (Asteraceae. Ambas entidades son descriptas y se presenta una clave para diferenciarlas de taxones afines, junto con algunas informaciones ecológicas sobre las entidades

  4. The family Asteraceae: General introduction

    Directory of Open Access Journals (Sweden)

    P. P. J. Herman

    2000-07-01

    Full Text Available The family Asteraceae (the daisy family is probably the largest plant family in the world. It is cosmopolitan in distribution and is economically important as many members are used for food, medicinal purposes, grazing for stock, or ornamentals, while some are troublesome weeds or poisonous to animals. The ‘flower ’is actually a collection of flowers grouped together to form a capitulum.

  5. Two New Labdane Diterpene Glycoside from Flowers of Bacchris Medulosa DC

    Directory of Open Access Journals (Sweden)

    D. A. Cifuente

    2000-03-01

    Full Text Available Two new labdane-type diterpene glycoside, were isolated from the flowers of Baccharis medulosa DC (Asteraceae. Structures of these compounds were established by application of various spectroscopic techniques.

  6. Podospermic acid, 1,3,5-tri-O-(7,8-dihydrocaffeoyl) quinic acid from Podospermum laciniatum (Asteraceae)

    DEFF Research Database (Denmark)

    Zidorn, Christian; Petersen, Bent O.; Udovicic ́, Vedrana

    2005-01-01

    A phytochemical investigation of Podospermum laciniatum (L.) DC. (Asteraceae) yielded the new quinic acid derivative podospermic acid (1,3,5-tridihydrocaffeoylquinic acid), which was named after the genus it was isolated from. The structure was established by HR mass spectrometry and extensive 1D...

  7. Apoptotic Potential of Artemsia sieberia Besser (Asteraceae ...

    African Journals Online (AJOL)

    (Asteraceae) Fraction against Human Cancer Cell Lines. Nael Abutaha*, Ashraf MA ... About 50 % of HepG2 cells were apoptotic when treated for 24 h with the .... phase-contrast microscopy. ... changes in the chromatin structure including.

  8. Wedelia chinenis (Asteraceae) - An overview

    Institute of Scientific and Technical Information of China (English)

    Sameksha Koul; A Pandurangan; RL Khosa

    2012-01-01

    Objective: The plant Wedelia chinensis (W. chinensis) belonging to family Asteraceae (sunflower family) has great importance in Ayurvedic, Sidhha and Unani systems of traditional medicine. Thorough screening of literature available on W. chinensis depicted the fact that it is a popular remedy among the various ethnic groups, Ayurvedic and traditional practitioners for treatment of various ailments. Extensive studies show presence of flavonoids, diterpenes, triterpene saponins and phytosteroids. W. chinensis is reported to possess antioxidant, anti-inflammatory, analgesic, antimicrobial, hepatoprotective, CNS depressant, anti-osteoporic, anticonvulsant, wound healing, sedative, antistress, antiulcerogenic and anticancer activity. This work gives an overview of the phytochemical and pharmacological evidence of W. chinensis. Although more studies are necessary to explore the therapeutic potential of this plant as, it has more therapeutic properties which are not known.

  9. Notas taxonómicas en Asteraceae

    OpenAIRE

    Adriana Bartoli; Roberto D. Tortosa; Francisco Ratto; Darío J Schiavinato

    2012-01-01

    Se describe una nueva variedad para Grindelia anethifolia y se amplía el área de distribución de Bidens andicola, Grindelia coronensis y Proustia cuneifolia var. mendocina.Taxonomic notes on Asteraceae. A new variety for Grindelia anethifolia is described, and the known area of Bidens andicola, Grindelia coronensis and Proustia cuneifolia var. mendocina is extended.

  10. Nuevas citas de Asteraceae para la provincia de Catamarca (Argentina New records of Asteraceae for the province of Catamarca (Argentina

    Directory of Open Access Journals (Sweden)

    Susana E. Freire

    2011-06-01

    Full Text Available Se mencionan los siguientes nuevos registros de Asteráceas para la provincia de Catamarca, Argentina: Baccharis acaulis, B. boliviensis var. latifolia, B. flexuosa, B. glutinosa var. angustissima, B. stenophylla (Tribu Astereae, Eupatorium patens var. tomentosum (Tribu Eupatorieae, Cosmos bipinnatus, C. peucedanifolius var. peucedanifolius, Helianthus annuus (Tribu Heliantheae, Gamochaeta erythractis, G. longipedicellata, Gnaphalium lacteum, Tessaria integrifolia var. integrifolia (Tribu Inuleae, Chuquiraga ruscifolia (Tribu Mutisieae, Senecio crepidifolius, S. subulatus var. subulatus, Xenophyllum incisum var. incisum (Tribu Senecioneae. Se citan además el hábitat de los taxones y las provincias fitogeográficas que integran. Se propone una nueva combinación, Baccharis glutinosa Pers. var. angustissima (DC. Giuliano.The following Asteraceae are mentioned for the province of Catamarca: Baccharis acaulis, B. boliviensis var. latifolia, B. flexuosa, B. glutinosa var. angustissima, B. stenophylla (Tribe Astereae, Eupatorium patens var. tomentosum (Tribe Eupatorieae, Cosmos bipinnatus, C. peucedanifolius var. peucedanifolius, Helianthus annuus (Tribe Heliantheae, Gamochaeta erythractis, G. longipedicellata, Gnaphalium lacteum, Tessaria integrifolia var. integrifolia (Tribe Inuleae, Chuquiraga ruscifolia (Tribe Mutisieae, Senecio crepidifolius, S. subulatus var. subulatus, Xenophyllum incisum var. incisum (Tribe Senecioneae. The habitat and phytogeographic provinces of the taxa are mentioned. The following new combination is proposed: Baccharis glutinosa Pers. var. angustissima (DC. Giuliano.

  11. (asteraceae nativas no rio grande do sul.

    Directory of Open Access Journals (Sweden)

    Anabela Silveira de Oliveira

    2005-01-01

    Full Text Available The present work describes the wood anatomy of Heterothalamus alienus and Heterothalamus rupestris (Astereae - Asteraceae, as part of the secondary xylem study in the named genus. For the two species it was recorded some features usually mentioned in the literature for the Asteraceae, as typically small vessels, grouped in a dendritic pattern, the presence of only simple perforation plates and of paratracheal parenchyma. Heterothalamus alienus shows spiral thickenings in the wood vessels and storied vasicentric axial parenchyma. Heterothalamus rupestris differs itself by the absence of spiral thickenings in wood vessels and by no storied axial parenchyma, in paratracheal vasicentric to unilateral patterns. Photomicrographs, quantitative data of anatomical features and a comparison between the two species of wood are also provided.

  12. Morpho-anatomical features of underground systems in six Asteraceae species from the Brazilian Cerrado

    Directory of Open Access Journals (Sweden)

    Beatriz Appezzato-da-Glória

    2011-09-01

    Full Text Available In the Brazilian Cerrado (neotropical savanna, the development of bud-bearing underground systems as adaptive structures to fire and dry periods can comprise an important source of buds for this ecosystem, as already demonstrated in the Brazilian Campos grasslands and North American prairies. Asteraceae species from both woody and herbaceous strata have subterranean organs that accumulate carbohydrates, reinforcing the adaptive strategy of these plants to different environmental conditions. This study aims to analyse the morpho-anatomy of underground systems of six species of Asteraceae (Mikania cordifolia L.f. Willd., Mikania sessilifolia DC, Trixis nobilis (Vell. Katinas, Pterocaulon alopecuroides (Lam. DC., Vernonia elegans Gardner and Vernonia megapotamica Spreng., to describe these structures and to verify the occurrence and origin of shoot buds, and to analyse the presence of reserve substances. Individuals sampled in Cerrado areas in São Paulo State showed thick underground bud-bearing organs, with adventitious or lateral roots and presence of fructans. Xylopodium was found in all studied species, except for Trixis nobilis, which had stem tuber. The presence of fructans as reserve, and the capacity of structures in the formation of buds indicate the potential of herbaceous species of Asteraceae in forming a viable bud bank for vegetation regeneration in the Brazilian Cerrado.No Cerrado brasileiro (savana neotropical, o desenvolvimento de sistemas subterrâneos que produzem gemas, como estruturas adaptativas contra o fogo e períodos de seca, pode compreender um importante suprimento de gemas para esse ecossistema, como já demonstrado nos campos brasileiros e nas pradarias norte-americanas. Espécies de Asteraceae tanto do estrato lenhoso, quanto do herbáceo têm órgãos que acumulam carboidratos, reforçando a estratégia adaptativa dessas plantas a diferentes condições ambientais. Este estudo tem o objetivo de analisar a morfo

  13. Notas taxonómicas en Asteraceae

    Directory of Open Access Journals (Sweden)

    Adriana Bartoli

    2012-06-01

    Full Text Available Se describe una nueva variedad para Grindelia anethifolia y se amplía el área de distribución de Bidens andicola, Grindelia coronensis y Proustia cuneifolia var. mendocina.Taxonomic notes on Asteraceae. A new variety for Grindelia anethifolia is described, and the known area of Bidens andicola, Grindelia coronensis and Proustia cuneifolia var. mendocina is extended.

  14. Pantoporate pollen in the Asteraceae (Vernonieae

    Directory of Open Access Journals (Sweden)

    Harold Robinson

    2014-05-01

    Full Text Available Pantoporate pollen, which occurs sporadically in the Monocots and Dicots, has now been found in Asteraceae in two apparently related genera of the tribe Vernonieae, Polydora Fenzl and Oocephala H.Rob. Disposition of pores in Polydora seems more asymmetric than in Oocephala. Based on the known relationships within the Vernonieae, some conjectures are made regarding development of the pantoporate condition in the group.

  15. Tipificación de "Arnica montana" L. (Asteraceae)

    OpenAIRE

    Ferrer Gallego, Pedro Pablo

    2014-01-01

    Se designa un lectótipo para Arnica montana L. (Asteraceae) a partir del material original de Linneo conservado en el herbario UPS-BURSER. A lectotype for Arnica montana L. (Asteraceae) is designated from Linnaeus’ original material preserved in the UPS-BURSER herbarium.

  16. Advanced DC/DC converters

    CERN Document Server

    Luo, Fang Lin

    2003-01-01

    INTRODUCTIONHistorical ReviewMultiple Quadrant ChoppersPump CircuitsDevelopment of DC/DC Conversion TechniqueCategorize Prototypes and DC/DC Converters Family TreeVOLTAGE-LIFT CONVERTERSIntroductionSeven Self-Lift ConvertersPositive Output Luo-ConvertersNegative Output Luo-ConvertersModified Positive Output Luo-Converters Double Output Luo-ConvertersPOSITIVE OUTPUT SUPER-LIFT LUO-CONVERTERS IntroductionMain SeriesAdditional SeriesEnhanced Series Re-Enhanced Series Multiple-Enhanced Series Summary of Positive Output

  17. DC + RSL

    DEFF Research Database (Denmark)

    Haxthausen, Anne

    1996-01-01

    This document gives some initial ideas of how the Duration Calculus (DC) can be integrated with the RAISE Specification Language (RSL).......This document gives some initial ideas of how the Duration Calculus (DC) can be integrated with the RAISE Specification Language (RSL)....

  18. Melilotoside Derivatives from Artemisia splendens (Asteraceae

    Directory of Open Access Journals (Sweden)

    Fariba H. Afshar

    2017-01-01

    Full Text Available A combination of solid-phase-extraction (SPE and reversed-phase preparative high-performance liquid chromatography (prep-HPLC of the methanolic extract of the aerial parts of Artemisia splendens (common name: “Asia Minor Wormwood”, an endemic Iranian species, afforded Z- and E-melilotosides (1 and 2, Z- and E-4-methoxy-melilotosides (3 and 4, and a new dimer, bis-ortho-Z-melilotoside (5, named: splendenoside. Whilst the structures of these compounds (1-5 were elucidated unequivocally by spectroscopic means, the in vitro free-radical-scavenging property of 1-5 was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH assay. This is the first report on the occurrence of any melilotoside derivatives in the genus Artemisia. Artemisia splendens, Asteraceae, 2,2-diphenyl-1-picrylhydrazyl (DPPH, free-radical scavenger, melilotoside, splendenoside

  19. Specialist bees collect Asteraceae pollen by distinctive abdominal drumming (Osmia) or brushing (Melissodes, Svastra)

    Science.gov (United States)

    Four species of western US Osmia (Cephalosmia) bees that are Asteraceae specialists (oligoleges) were observed to employ a heretofore unappreciated, stereotypical means of collecting pollen, abdominal drumming, to gather pollen from 19 flowering species representing nine tribes of Asteraceae. Abdom...

  20. Simplified dc to dc converter

    Science.gov (United States)

    Gruber, R. P. (Inventor)

    1984-01-01

    A dc to dc converter which can start with a shorted output and which regulates output voltage and current is described. Voltage controlled switches directed current through the primary of a transformer the secondary of which includes virtual reactance. The switching frequency of the switches is appropriately varied to increase the voltage drop across the virtual reactance in the secondary winding to which there is connected a low impedance load. A starting circuit suitable for voltage switching devices is provided.

  1. PWM DC/DC Converter

    OpenAIRE

    Chen, Juan

    2008-01-01

    This report is the result of a Master Thesis work done at Seaward Electronics Inc. in Beijing, China from June to December in 2007. The main goal for this thesis is to verify and improve the performance of Honey-PWM DC-DC converter, which has been fabricated by a standard 0.6um CMOS processes. The project was started with studying of Buck converter structure. After the understanding of the converter structure, the project goes in to the analyses phase for each sub-cells, including the theory,...

  2. Ejemplares tipo de Asteraceae (= Compositae de A. L. Cabrera

    Directory of Open Access Journals (Sweden)

    Susana E. Freire

    2000-01-01

    Full Text Available Freire, S. E. & Iharlegui, L. 2000. Ejemplares tipo de Asteraceae (= Compositae de A. L.Cabrera. Darwiniana 38(3-4: 307-364.El presente trabajo representa un catálogo de los ejemplares tipo de 426 especies y 82 variedades deAsteraceae descriptas por A. L. Cabrera entre los años 1931 y 1999. Los taxones se presentan en ordenalfabético. Para cada taxón se indica: diagnosis original, tipo nomenclatural, categoría del tipo, herbario,etiqueta original y nombre actualizado

  3. Warionia (Asteraceae: a relict genus of Cichorieae?

    Directory of Open Access Journals (Sweden)

    Katinas, Liliana

    2008-12-01

    Full Text Available The genus Warionia, with its only species W. saharae, is endemic to the northwestern edge of the African Sahara desert. This is a somewhat thistle-like aromatic plant, with white latex, and fleshy, pinnately- partite leaves. Warionia is in many respects so different from any other genus of Asteraceae, that it has been tentatively placed in the tribes Cardueae, Cichorieae, Gundelieae, and Mutisieae. Until now, a comprehensive study of Warionia to have a complete context for discussing its taxonomic position is lacking. The general morphology, anatomy, palynology and chromosome number of W. saharae are investigated here, and the species is described and illustrated. Laticifers in leaves and stems indicate a relationship with Cichorieae, and are associated with the phloem, in contact with it or with the surrounding sclerenchyma sheath. The pollen features indicate a strong relation with Cardueae, namely the structure with Anthemoid pattern where the columellae are joined to the foot layer, the ectosexine with thin columellae, the endosexine with stout and ramified columellae, the conspicuous spines with globose bases and conspicuous apical channels, and the tectum surface very perforate. Chromosomal counts resulted in 2n = 34. The morphological and palynological evidence positions Warionia between the tribes Cardueae and Cichorieae suggesting that it could be a remnant of the ancestral stock that gave rise to both tribes.El género Warionia, y su única especie, W. saharae, es endémico del noroeste del desierto africano del Sahara. Es una planta semejante a un cardo, aromática, con látex blanco y hojas carnosas, pinnatipartidas. Warionia es tan diferente de otros géneros de Asteraceae que fue ubicada en las tribus Cardueae, Cichorieae, Gundelieae y Mutisieae. Hasta ahora, no existía un estudio global de Warionia como contexto para discutir su posición taxonómica. Se ha investigado aquí su morfología, anatomía, palinología y n

  4. Microsculpture of cypselae surface of Baccharis sect. Caulopterae (Asteraceae from Brazil

    Directory of Open Access Journals (Sweden)

    Boldrini, Ilsi Iob

    2011-06-01

    Full Text Available The aim of this study was to characterize the microsculpture of the cypselae surface of the Brazilian species of Baccharis L. sect. Caulopterae DC. (Asteraceae, and to compare this data it with the taxonomy of the group. Scanning electron microscopy was used to examine the cypsela surface of 25 taxa of Baccharis sect. Caulopterae from Brazil. According to the micromorphology of the cypsela surface, the species can be classified into five distinct groups. The cypselae of the species of the Baccharis trimera species complex (B. crispa, B. cylindrica, B. jocheniana, B. myriocephala, and B. trimera share the same micromorphological features.Para examinar la superficie de cipselas de 25 táxones de Baccharis L. sect. Caulopterae DC. de Brasil se ha utilizado la microscopía electrónica de barrido. El objetivo del estudio fue caracterizar la microescultura de la superficie de cipselas de la sección y colaborar con la delimitación taxonómica a nivel específico. Las especies fueron clasificadas en cinco grupos distintos según la micromorfología y asignados a la terminología existente. El complejo Baccharis trimera (B. crispa, B. cylindrica, B. jocheniana, B. myriocephala y B. trimera mostró afinidades micromorfológicas de las cipselas.

  5. In vitro anti-tumour studies on Cnicus wallichi DC.

    Science.gov (United States)

    Vijaylakshmi, S; Nanjan, M J; Suresh, B

    2009-07-01

    Cnicus wallichi DC belonging to the family Asteraceae (Compositae) commonly known as Indian thistle and cirsium wallichi. It is an important medicinal plant indigenous to Nilgiris, Tamilnadu, South India. Since the related species Cnicus benedictus was reported for its anti cancer activities, In vitro screening studies for antitumour activities were carried out for different extracts of Cnicus wallichi DC. Seven different extracts were obtained from the aerial parts of the whole plant by successive solvent extraction and maceration process and subjected for In vitro screening studies. Antitumour study was carried out by short term toxicity studies using Dalton's Lymphoma Ascites (DLA) cells. The ethyl acetate extract of Cnicus wallichi DC showed significant antioxidant activity in all the methods.

  6. Taxonomic novelties in Mikania (Asteraceae: Eupatorieae) from Atlantic Forest, Brazil

    NARCIS (Netherlands)

    Borges, R.A.X.; Forzza, R.C.; Fraga, C.N.

    2010-01-01

    During studies of Brazilian Atlantic Forest Asteraceae, a new species and a replacement name were determined: Mikania amorimii from Bahia State and Mikania capixaba from Espírito Santo State. The former is a new species related to M. ternata but distinct by its leaves, involucral bracts and cypsela

  7. nature of ergastic substances in some nigerian asteraceae 160

    African Journals Online (AJOL)

    DR. AMINU

    There was no correlation between life forms and the ... substances in plant systematics has been stressed by various workers (Omoigui and Gill, 1988; Idu and Gill,. 1998) ... Table 1: Summary of the Locality, Habit and Nature of Ergastic Substances in the Seeds of Some Nigerian Asteraceae. Taxon ... Bank of River Kaduna,.

  8. Taxonomic novelties in Mikania (Asteraceae: Eupatorieae) from Atlantic Forest, Brazil

    NARCIS (Netherlands)

    Borges, R.A.X.; Forzza, R.C.; Fraga, C.N.

    2010-01-01

    During studies of Brazilian Atlantic Forest Asteraceae, a new species and a replacement name were determined: Mikania amorimii from Bahia State and Mikania capixaba from Espírito Santo State. The former is a new species related to M. ternata but distinct by its leaves, involucral bracts and cypsela

  9. New species of Lessingianthus (Asteraceae, Vernonieae) from Brazil and Paraguay

    NARCIS (Netherlands)

    Dematteis, M.; Angulo, M.B.

    2012-01-01

    Two new species of the genus Lessingianthus (Vernonieae, Asteraceae) from Brazil and Paraguay are described and illustrated. Lessingianthus cipoensis is characterized by the presence of solitary heads disposed in short branches and ovate to elliptical leaves. It has a certain resemblance to L. vesti

  10. Hyurterianum (Asteraceae, Inuleae), a new species from NE Anatolia, Turkey

    DEFF Research Database (Denmark)

    Gemici, Y.; Tan, K.; Yidirim, H.

    2008-01-01

    Helichrysum yurterianum Y. Gemici, Kit Tan, H. Yildirim & M. Gemici (Asteraceae, Inuleae) is described and illustrated. It is a serpentine endemic restricted to the province of Erzincan in NE Anatolia, Turkey. Its affinities are with H. arenarium and H. noeanum, which both have a wider distribution...

  11. Gnapholide: a new guaiac-dimer from Pulicaria gnaphalodes (Asteraceae).

    Science.gov (United States)

    Ali, Muhammad Shaiq; Jahangir, Muhammad; Uzair, Syed Shah; Erian, Ayman Wahba; Tareen, Rasool Bakhsh

    2002-06-01

    The ethyl acetate soluble part of the chloroform extract of Pulicaria gnaphalodes belonging to the family Asteraceae afforded a new sesquiterpene-dimer of guaiane class named as gnapholide and anabsinthin of the same skeleton. The structures of both the compounds were elucidated with the aid of spectroscopic techniques including 2D NMR.

  12. Cytogeography and chromosome evolution of subgenus Tridentatae of Artemisia (Asteraceae)

    Science.gov (United States)

    E. Durant McArthur; Stewart C. Sanderson

    1999-01-01

    The subgenus Tridentatae of Artemisia (Asteraceae: Anthemideae) is composed of 11 species of various taxonomic and geographic complexities. It is centered on Artemisia tridentata with its three widespread common subspecies and two more geographically confined ones. Meiotic chromosome counts on pollen mother cells...

  13. Morphometric study of Euchiton traversii complex (Gnaphalieae: Asteraceae)

    NARCIS (Netherlands)

    Flann, C.M.; Breitwieser, I.; Ward, J.M.; Walsh, N.G.; Ladiges, P.Y.

    2008-01-01

    A morphometric study was undertaken into alpine and subalpine species of Euchiton Cass. (Gnaphalieae: Asteraceae) in the Euchiton traversii species complex in south-eastern Australia and New Zealand. Phenetic analysis of both field-collected and herbarium specimens resolved the following six taxa in

  14. Isolerad DC/DC-omvandlare

    OpenAIRE

    Andersson, Martin

    2011-01-01

    1 SammanfattningCrossControl är ett företag som bland annat tillverkar integrerade datorlösningar. Datorerna drivs normalt med 18-30 VDC och förbrukar som mest 50W. Datorerna säljs till flertalet olika kunder som monterar dem i allt från skogsmaskiner till tåg. I de olika fordonen varierar spänningen i de befintliga elnäten. Detta skapar behovet av att omvandla spänningen till en nivå som datorerna klarar av. En sådan apparat kallas DC/DC-omvandlare. Spänningsomvandling kan utföras genom linj...

  15. Macroevolutionary dynamics in the early diversification of Asteraceae.

    Science.gov (United States)

    Panero, Jose L; Crozier, Bonnie S

    2016-06-01

    Spatial and temporal differences in ecological opportunity can result in disparity of net species diversification rates and consequently uneven distribution of taxon richness across the tree of life. The largest eudicotyledonous plant family Asteraceae has a global distribution and at least 460 times more species than its South American endemic sister family Calyceraceae. In this study, diversification rate dynamics across Asteraceae are examined in light of the several hypothesized causes for the family's evolutionary success that could be responsible for rate change. The innovations of racemose capitulum and pappus, and a whole genome duplication event occurred near the origin of the family, yet we found the basal lineages of Asteraceae that evolved in South America share background diversification rates with Calyceraceae and their Australasian sister Goodeniaceae. Instead we found diversification rates increased gradually from the origin of Asteraceae approximately 69.5Ma in the late Cretaceous through the Early Eocene Climatic Optimum at least. In contrast to earlier studies, significant rate shifts were not strongly correlated with intercontinental dispersals or polyploidization. The difference is due primarily to sampling more backbone nodes, as well as calibrations placed internally in Asteraceae that resulted in earlier divergence times than those found in most previous relaxed clock studies. Two clades identified as having transformed rate processes are the Vernonioid Clade and a clade within the Heliantheae alliance characterized by phytomelanic fruit (PF Clade) that represents an American radiation. In Africa, subfamilies Carduoideae, Pertyoideae, Gymnarrhenoideae, Cichorioideae, Corymbioideae, and Asteroideae diverged in a relatively short span of only 6.5millionyears during the Middle Eocene.

  16. Preliminary phytochemical screening and In vitro antioxidant activities of the aqueous extract of Helichrysum longifolium DC

    OpenAIRE

    Okoh Anthony I; Aiyegoro Olayinka A

    2010-01-01

    Abstract Background Many oxidative stress related diseases are as a result of accumulation of free radicals in the body. A lot of researches are going on worldwide directed towards finding natural antioxidants of plants origins. The aims of this study were to evaluate in vitro antioxidant activities and to screen for phytochemical constituents of Helichrysum longifolium DC. [Family Asteraceae] aqueous crude extract. Methods We assessed the antioxidant potential and phytochemical constituents ...

  17. Atividade antimicrobiana de óleos essenciais produzidos por Baccharis dracunculifolia D.C. e Baccharis uncinella D.C. (Asteraceae Antimicrobial activity of essential oils produced by Baccharis dracunculifolia D.C. and Baccharis uncinella D.C. (Asteraceae

    Directory of Open Access Journals (Sweden)

    Regina Ferronatto

    2007-06-01

    Full Text Available Os óleos essenciais obtidos de plantas nativas de Baccharis dracunculifolia e Baccharis uncinella, também conhecido como óleo-de-vassoura, é utilizado na indústria de perfumaria, proporcionando um aroma exótico a diversos perfumes, além de muitos estudos sobre atividades biológicas dessas espécies destacam os efeitos alelopáticos, antioxidante, antimicrobianos, citotóxicos e antiinflamatórios. A vassoura é uma planta arbustiva de ocorrência espontânea no Brasil, assim como nos demais países do Mercosul. A composição do óleo depende da região geográfica e do processo de extração utilizado e a importância comercial está diretamente relacionada com a concentração de compostos oxigenados, destacando o nerolidol e o espatulenol. Óleos essenciais obtidos dessas duas espécies pelo processo de hidrodestilação, foram avaliados pelo método de difusão em disco de papel, em placas de Petri contendo meio de Müeller-Hinton, semeadas com suspensões bacterianas previamente ajustadas ao tubo 0,5 da escala de Mac Farland de quatro cepas provenientes da American Type Culture Colection: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 e Pseudomonas aeruginosa ATCC 27853. Discos contendo diferentes volumes dos óleos essenciais sem qualquer diluição (1, 3, 5 e 10 µL/disco foram adicionadas às placas e incubadas a 36 ºC por 24 a 48 horas. Discos de cloranfenicol (CLO e amoxicilina (AMO com volumes de 50 e 10 µg/disco respectivamente, foram utilizados como controle. Os resultados apresentados revelam que ambos os óleos avaliados apresentam atividade antimicrobiana sobre S. aureus, E. coli e P. aeruginosa.Essential oils obtained from the native plants Baccharis dracunculifolia and Baccharis uncinella, known also as "óleo de vassoura", are used in the perfumery industry, providing diverse perfumes with exotic aromas. Besides several studies about the biological activities of these species highlight the allelopathic, antioxidant, antimicrobial, cytotoxic and antiinflammatory effects. The broom is a bushy plant which occurs spontaneously in Brazil as well as in the other countries from Mercosul. The oil composition depends on the geographical region and on the concentration of oxygenated blends, highlighting the nerolidol and the sphatulenol. Essential oils obtained from these two species by the hydrodistillation process were assessed by the diffusion method in paper disc, in Petri plaques containing Müeller-Hinton agar, with bacteria suspensions, previously adjusted to the tube 0,5 of Mac Farland scale of four strains which came from the American Type Culture Collection: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853. Discs containing different volumes of the essential oils (1, 3, 5 and 10 (µL/disc were added to plaques and incubated at 36 ºC for 24 - 48 hours. Chloranfenicol (CLO and Amoxicillin (AMO with concentrations of 30 and 10 µg/disc were respectively used as control. The presented results reveal that both assessed oils present antimicrobial activity against S. aureus, E. coli and P. aeruginosa.

  18. Adaptable DC offset correction

    Science.gov (United States)

    Golusky, John M. (Inventor); Muldoon, Kelly P. (Inventor)

    2009-01-01

    Methods and systems for adaptable DC offset correction are provided. An exemplary adaptable DC offset correction system evaluates an incoming baseband signal to determine an appropriate DC offset removal scheme; removes a DC offset from the incoming baseband signal based on the appropriate DC offset scheme in response to the evaluated incoming baseband signal; and outputs a reduced DC baseband signal in response to the DC offset removed from the incoming baseband signal.

  19. Contemporary inter-specific hybridization between Cirsium aduncum and C. haussknechtii (Asteraceae: Evidence from molecular and morphological data

    Directory of Open Access Journals (Sweden)

    Sheidai Masoud

    2016-01-01

    Full Text Available Cirsium aduncum Fisch. & C.A.Mey. Ex DC. and C. haussknechtii Boiss., (Asteraceae are important medicinal plant species that grow in different geographical regions of Iran. We had no knowledge about population genetic structure, intra-specific and inter-specific gene flow and the presence of hybrid zone for this two species in Iran. Therefore, in order to provide data for conservation of these two medicinally important species, the population genetic analysis and morphometric studies were performed in 18 geographical populations of these species. ANOVA and MDS analyses revealed significant morphological difference among the studied populations in either species, while MDS plot showed morphological overlap in plants of these two species. AMOVA test revealed significant genetic difference among the studied populations. Mantel test showed positive significant correlation between genetic and geographical distances and the occurrence of isolation by distance. Population assignment test and STRUCTURE plot of genetic data revealed inter-specific introgression between these species.

  20. Anti-inflammatory activity of Lychnophora passerina, Asteraceae (Brazilian Arnica).

    OpenAIRE

    Oliveira, Patricia Capelari de; Paula, Carmem Aparecida de; Rezende, Simone Aparecida; Campos, Fernanda Torres; Guimarães, Andrea Grabe; Lombardi, Júlio Antônio; Guimarães, Dênia Antunes Saúde

    2011-01-01

    Ethnopharmacological relevance: Lychnophora passerina (Asteraceae), popularly known as arnica, is used to treat inflammation, pain, rheumatism, contusions, bruises and insect bites in Brazilian traditional medicine. Materials and methods: The anti-inflammatory activity of crude ethanolic extract of aerial parts of L. passerina and its ethyl acetate and methanolic fractions had their abilities to modulate the production of NO, TNF-α and IL-10 inflammatory mediators in LPS/IFN-γ-stimulated J774...

  1. New species of Ophryosporus (Eupatorieae Asteraceae from Peru

    Directory of Open Access Journals (Sweden)

    Abundio Sagástegui Alva

    2013-03-01

    Full Text Available Ophryosporus marchii Sagást. & E. Rodr. is described as a new species of Ophryosporus Meyen (Eupatorieae: Asteraceae from the Department of Cajamarca, Peru. This new species is apparently endemic to the province of Contumaza and closest relative to O. sagasteguii H. Rob. It is critically compared with this species and data on its geographical distribution, ecology and conservation status are provided.

  2. "Forback" Dc-To-Dc Converters

    Science.gov (United States)

    Lukemire, Alan T.

    1992-01-01

    Dc-to-dc power-converter circuits called "forback" resemble circuits of standard configurations called "forward", "flyback", and "Cuk". Circuit employs minor modifications to existing topologies, combines advantages, while eliminating disadvantages, of older circuits.

  3. Nerolidol, an antiulcer constituent from the essential oil of Baccharis dracunculifolia DC (Asteraceae).

    Science.gov (United States)

    Klopell, Fernando Canani; Lemos, Marivane; Sousa, João Paulo Barreto; Comunello, Eros; Maistro, Edson Luis; Bastos, Jairo Kennup; de Andrade, Sérgio Faloni

    2007-01-01

    In this study, the antiulcerogenic effect of essential oil from Baccharis dracunculifolia was evaluated using the model of acute gastric lesions induced by ethanol. The ulcerative lesion index (ULI) was significantly reduced by oral administration of the essential oil of B. dracunculifolia at doses of 50, 250 and 500 mg/kg which reduced the lesions by 42.79, 45.70 and 61.61%, respectively. The analysis of the chemical composition of the essential oil from B. dracunculifolia by GC showed that this was composed mainly of mono- and sesquiterpenes and the majority compound was nerolidol. Therefore, antiulcerogenic activity of nerolidol (50, 250 and 500 mg/kg) was investigated using ethanol-, indomethacin- and stress-induced ulcer models in rat. In the stress-induced ulcer model, a significant reduction of the ULI in animals treated with nerolidol (50, 250 and 500 mg/kg) and cimetidine (100 mg/kg) was observed, compared to the control group (p omeprazol (positive control), respectively. In indomethacin-ulcer the percentage of inhibition of ulcer was 34.69, 40.80, 51.02 and 46.93% in groups treated with 50, 250, 500 mg/kg of nerolidol and 100 mg/ kg of cimetidine (positive control), respectively. The results of this study show that nerolidol displays antiulcer activity, as it significantly inhibited the formation of ulcers induced in different animal models. However, further pharmacological and toxicological investigations, to delineate the mechanism(s) of action and the toxic effects, are required to allow the use of nerolidol for the treatment of gastric ulcer.

  4. Seed germination of Chresta sphaerocephala DC. and Lessingianthus bardanoides (Less. H. Rob. (asteraceae from Cerrado

    Directory of Open Access Journals (Sweden)

    Graziela Cury

    2010-12-01

    Full Text Available This work aimed to study the effects of different temperature conditions on the germination of L. bardanoides and C. sphaerocephala seeds, compare the germination rates of these two species and estimate the occurrence of embryoless seeds. The results indicated that the best temperatures for the germination of L. bardanoides seeds were 20, 25 and 20-30ºC and for C. sphaerocephala, 20-35ºC and 40.32 µmol m-²s-¹ irradiance; L. bardanoides had a higher germination rate since the number of seeds with embryos higher compared with C. sphaerocephala.Este trabalho teve como objetivo estudar os efeitos de diferentes condições de temperatura na germinação de sementes de L. bardanoides e C. sphaerocephala, comparar as taxas de germinação dessas duas espécies e estimar a ocorrência de sementes sem embrião. Os resultados indicaram que as melhores temperaturas para a germinação das sementes de L. bardanoides foram 20, 25 e 20-30ºC e, para C. sphaerocephala, 20 e 20-35ºC e 40.32 µmol m-²s-¹ de irradiância; L. bardanoides apresentou maior taxa germinativa, já que o número de frutos contendo semente com embrião é maior, comparado com C. sphaerocephala.

  5. Multiport Resonant DC-DC Converter

    OpenAIRE

    Tran, Yan-Kim; Dujic, Drazen; Barrade, Philippe

    2015-01-01

    his paper presents a multiport galvanically isolated LLC resonant DC-DC converter suitable for DC applications. A three-port structure is analyzed, with full bidirectional power flow capabilities, simple control and behavior similar to that expected from a DC transformer. Each port is equipped with half-bridge modules accompanied with tuned resonant tank, partly realized with elements of a multi- winding high frequency transformer. With some restrictions that are explained in the paper, each ...

  6. VLSI Hybrid DC-DC Regulator

    OpenAIRE

    Cosp Vilella, Jordi; Martínez García, Herminio

    2015-01-01

    Hybrid DC-DC regulators are structures that combine both a linear voltage regulator and a switching DC-DC converter. The main objective of this hybrid topology is to converge, in a single circuit topology, the best of both alternatives: a small voltage output ripple, which is a common characteristic of linear regulator circuits, and good energy efficiency, as in switching alternatives. While the linear regulator fixes the required output voltage to a fixed value with negligible steady-state r...

  7. Local Bifurcations in DC-DC Converters

    OpenAIRE

    2012-01-01

    Three local bifurcations in DC-DC converters are reviewed. They are period-doubling bifurcation, saddle-node bifurcation, and Neimark bifurcation. A general sampled-data model is employed to study the types of loss of stability of the nominal (periodic) solution and their connection with local bifurcations. More accurate prediction of instability and bifurcation than using the averaging approach is obtained. Examples of bifurcations associated with instabilities in DC-DC converters are given.

  8. High-Efficiency dc/dc Converter

    Science.gov (United States)

    Sturman, J.

    1982-01-01

    High-efficiency dc/dc converter has been developed that provides commonly used voltages of plus or minus 12 Volts from an unregulated dc source of from 14 to 40 Volts. Unique features of converter are its high efficiency at low power level and ability to provide output either larger or smaller than input voltage.

  9. Evaluation of inflorescence visitors as pollinators of Echinacea angustifolia (Asteraceae): comparison of techniques.

    Science.gov (United States)

    Wist, Tyler J; Davis, Arthur R

    2013-10-01

    Inflorescences (heads or capitula) of the putative self-incompatible species, purple coneflower (Echinacea angustifolia (DC) Cronq. (Asteraceae)), were visited by insects representing the Coleoptera, Diptera, Hymenoptera, and Lepidoptera, in accordance with a generalist pollination syndrome. Measurement of the effectiveness of insect species as pollinators was accomplished by permitting solitary visits to receptive, central disc florets of virgin (previously bagged) heads. Four parameters were quantified: total stigmatic pollen load and proportion of pollen grains germinated, numbers of pollen tubes at style bases, and percentages of total receptive florets that had retracted (shrivelled) styles. Quantifying total and germinated pollen grains proved ineffective, partly owing to the tendency of self-pollen to initiate pollen tubes. The most effective pollinators were Apidae, especially bumble bees (Bombus spp.) and the European honey bee (Apis mellifera L.) (mean: 39 - 61% of styles retracted). Other noteworthy pollinators were cloudless sulfur butterflies (Phoebis sennae L.--Pieridae; mean 47% of style bases with pollen tubes), golden blister beetles (Epicauta ferruginea Say--Meloidae; 44%), and grasshopper bee flies (Systoechus vulgaris Loew--Bombyliidae; 22%). Sunflower leafcutter bees (Megachile pugnata Say) were less effective (4% of styles retracted). Promisingly, analysis of the proportion of retracted styles provided similar results to the established technique of pollen-tube quantification, but had the significant advantages of being completed more rapidly, without a microscope, and in the field. The quantitative technique of retracted-style analysis appears well suited for prompt measurement of inflorescence-visiting insects as pollinators of many asteraceans.

  10. Panorama de la familia Asteraceae (= Compositae en la Republica Argentina An overview of the plant family Asteraceae ( = Compositae in Argentina

    Directory of Open Access Journals (Sweden)

    Liliana Katinas

    2007-07-01

    Full Text Available Se presenta un panorama de la familia Asteraceae en la República Argentina , que incluye una breve historia taxonómica, datos numéricos de tribus, géneros y especies, ejemplos de endemismos y daptaciones ecológicas y una reseña sobre la hipótesis del origen de la familia en Patagonia. En la Argentina, las asteráceas representan la familia más numerosa con 227 géneros (cinco son endémicos y ca. 1400 especies (92 son adventicias y 382 son endémicas. En términos de taxones nativos, se hallan representadas en nuestro país todas las tribus de Asteraceae excepto Inuleae (sensu Bremer. Las tribus Arctoteae y Calenduleae están representadas por taxones adventicios exclusivamente y Cardueae posee sólo una especie nativa. Barnadesieae y Mutisieae son las únicas tribus con géneros endémicos de Argentina y también presentan el porcentaje más alto de géneros y especies en el país en comparación con el resto de las tribus. El mayor número de especies nativas, endémicas y no endémicas, se da en las provincias fitogeográficas Altoandina y Patagónica. La tribu más representada en número de géneros es Heliantheae, y en número de especies nativas es Senecioneae.An overview of the family Asteraceae in Argentina that includes a brief taxonomic history, numerical data of tribes, genera and species, examples of endemisms and ecological adaptations, and a discussion on the hypothesis on the origin of the family in Patagonia is given. Asteraceae is the most numerous family in Argentina , with 227 genera (five are endemic and ca. 1400 species (92 are adventitious and 382 are endemic. In relation to the native taxa, all tribes of Asteraceae occur in Argentina excepting Inuleae (sensu Bremer. Tribes Arctoteae and Calenduleae are represented exclusively by adventitious taxa, and Cardueae has only one native species. Barnadesieae and Mutisieae are the only tribes with endemic genera in Argentina and they also present the highest percentage of

  11. CMOS Integrated Capacitive DC-DC Converters

    CERN Document Server

    Van Breussegem, Tom

    2013-01-01

    This book provides a detailed analysis of all aspects of capacitive DC-DC converter design: topology selection, control loop design and noise mitigation. Readers will benefit from the authors’ systematic overview that starts from the ground up, in-depth circuit analysis and a thorough review of recently proposed techniques and design methodologies.  Not only design techniques are discussed, but also implementation in CMOS is shown, by pinpointing the technological opportunities of CMOS and demonstrating the implementation based on four state-of-the-art prototypes.  Provides a detailed analysis of all aspects of capacitive DC-DC converter design;  Analyzes the potential of this type of DC-DC converter and introduces a number of techniques to unleash their full potential; Combines system theory with practical implementation techniques; Includes unique analysis of CMOS technology for this application; Provides in-depth analysis of four fabricated prototypes.

  12. Identification and quantification of flavonoids from Chuquiraga spinosa (Asteraceae).

    Science.gov (United States)

    Landa, Amaya; Casado, Raquel; Calvo, M Isabel

    2009-10-01

    Nine flavonol glycosides (quercetin-3-O-glucuronide, quercetin-3-O-rutinoside, quercetin-3-O-glucoside, kaemperol-3-O-glucuronide, kaemperol-3-O-rutinoside, kaempherol-3-O-glucoside, isorhamnetin-3-O-glucuronide, isorhamnetin-3-O-rutinoside and isorhamnetin-3-O-glucoside) were isolated from the aerial parts of Chuquiraga spinosa (R. et P.) D. Don (Asteraceae). The identification of the compounds was carried out by HPLC/DAD, HPLC/MS and NMR analysis. These compounds may be useful in the chemotaxonomy of the genus and species.

  13. Psephellus vanensis (Asteraceae, a new species from east Turkey

    Directory of Open Access Journals (Sweden)

    Bekir Dogan

    2015-04-01

    Full Text Available A new species, Psephellus vanensis A.Duran, Behçet & B.Dogan (Asteraceae from Anatolia, Turkey, is described and illustrated. The species grows on the serpentine stony field of the village of Çaldıran in the district of Başkale (Van province in eastern Anatolia. It is morphologically similar to Psephellus pyrrhoblepharus (Boiss. Wagenitz. Diagnostic characters are discussed, and a key to the most similar species is provided. Ecology, conservation status and notes on biogeography of the species are also presented. In addition, the geographical distribution of the new species and other related species in Turkey is mapped.

  14. Structural studies of chemical constituents of Thithonia Tagetiflora Desv (Asteraceae)

    DEFF Research Database (Denmark)

    Ngoc Huynh, Vinh; Nguyen Thi Hoai, Thu; Phi Phung Nguyen, Kim

    2013-01-01

    Tithonia tagetiflora Desv. (Asteraceae) is a widespread plant in Vietnam, and the species of Tithonia are known as plants containing many biologically active compounds. However, T. tagetiflora's chemical composition remains mostly unknown. Therefore, we now report the structural elucidation of tw......)-roseoside (4), and one glutinane type triterpene, epi-glutinol (5), from the leaves of T. tagetiflora. Their structures are established by 1D and 2D NMR spectroscopy, as well as ESI-MS analysis and comparison with literature data...

  15. The Rare Perennial Balduina atropurpurea (Asteraceae) at Fort Stewart, Georgia

    Science.gov (United States)

    1998-06-01

    in Helianthus annuus (Asteraceae). Systematic Botany 3:403-407. Ewel, K.C. 1990. Swamps, pp 281-323 in R.L. Meyers and J.J. Ewel, eds. Ecosystems of...HQ FORSCOM, AFPI-ENE; and Linton L . Swindell, Fort Stewart Fish and Wildlife Branch, AFZP- DEV-W. Public Law 101-510 established SERDP as a multi...USACERL TR-98/75 21 A flowering genet. ^K^ l ^fl Kr*’ Si * ■ Two open inflorences: The top infloresecence with outer stigmas and one row of anthers

  16. Atividade antioxidante e captora de radicais livres dos extratos de Achyrocline alata (Kunth. DC. em comparação com extratos de Achyrocline satureioides (Lam. DC. Antioxidant and free radical scavenging effects in extracts of the Achyrocline alata (Kunth DC. in comparison with the extracts of the Achyrocline satureioides (LAM. DC.

    Directory of Open Access Journals (Sweden)

    Rafaela F. Grassi-Zampieron

    2009-06-01

    Full Text Available Achyrocline alata (Kunth. DC. e Achyrocline satureioides (Lam. DC., espécies pertencentes à família Asteraceae, são utilizadas na medicina popular de Campo Grande, Mato Grosso do Sul, como plantas sucedâneas. O presente trabalho teve com objetivo comparar os extratos obtidos dessas espécies através de ensaios químicos simples destinados a testar as atividades antioxidante e captora de radicais livres, utilizando como modelo β-caroteno e DPPH, respectivamente. Tais ensaios revelaram que os extratos de A. satureioides foram mais ativos como captores de radicais livres do que os extratos obtidos de A. alata. Todos os experimentos foram feitos em triplicata, utilizando quercetina como padrão.Achyrocline alata (Kunth. DC. and Achyrocline satureioides (Lam. DC. are species belonging to the family Asteraceae widely used in the folk medicine of Campo Grande, Mato Grosso do Sul, being considered substitute plants. The present work aimed to compare the obtained extracts of these species to simple chemical assays, in order to test the antioxidant activity and free radical scavenging, using β-carotene and DPPH as reference, respectively. With these assays it was observed that the obtained extracts of Achyrocline satureioides were more active, as free radical scavenging, than the same obtained extracts of Achyrocline alata. These chemical assays were compared to a known patterned, quercetin, and and they were dealt under triplicate basis.

  17. DC/DC Converter Stability Testing Study

    Science.gov (United States)

    Wang, Bright L.

    2008-01-01

    This report presents study results on hybrid DC/DC converter stability testing methods. An input impedance measurement method and a gain/phase margin measurement method were evaluated to be effective to determine front-end oscillation and feedback loop oscillation. In particular, certain channel power levels of converter input noises have been found to have high degree correlation with the gain/phase margins. It becomes a potential new method to evaluate stability levels of all type of DC/DC converters by utilizing the spectral analysis on converter input noises.

  18. 76 FR 31462 - Airworthiness Directives; The Boeing Company Model DC-10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10...

    Science.gov (United States)

    2011-06-01

    ... Model DC-10-10, DC- 10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40, DC-10-40F... Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.... Applicability (c) This AD applies to all The Boeing Company Model DC-10-10, DC-10-10F, DC-10-15,......

  19. Comparative leaf morphology and anatomy of three Asteraceae species

    Directory of Open Access Journals (Sweden)

    Patricia Milan

    2006-01-01

    Full Text Available The objective of this paper was to describe and compare the morphology and anatomy of mature leaves of Mikania glomerata Spreng., Porophyllum ruderale Cass. and Vernonia condensata Baker (Asteraceae species that have different habits emphasizing their secretory structures. Longitudinal and transversal sections of mature leaf blades of the three species were analyzed at the apex, base, and medium third part of the midvein of the leaf blade and of the margin. M. glomerata had uniseriate glandular trichomes and secretory ducts; P. ruderale had hydathodes and secretory cavities; and V. condensata had idioblasts and uni-and biseriate glandular trichomes.Este trabalho teve por objetivo descrever e comparar a morfo-anatomia das folhas adultas de Mikania glomerata Spreng., Porophyllum ruderale Cass. e Vernonia condensata Baker (Asteraceae, que possuem diferentes hábitos, enfatizando suas estruturas secretoras. Secções longitudinais e transversais dos limbos foliares foram analisadas nas regiões do ápice, da base e do terço médio na altura da nervura central, do limbo foliar e da margem. M. glomerata apresentou tricomas glandulares unisseriados e ductos secretores; P. ruderale tinha hidatódios e cavidades secretoras; e V. condensata apresentou idioblastos e tricomas glandulares uni- ou bisseriados.

  20. DC to DC converters: operation; Hacheurs: fonctionnement

    Energy Technology Data Exchange (ETDEWEB)

    Bernot, F. [Ecole d' Ingenieurs de Tours, 37 (France)

    2002-05-01

    This article deals with pulse width modulation (PWM) and pulse position modulation (PPM) DC to DC converters. A tri-phase PWM converter is made of 6 simple DC/DC converters grouped together into 3 reversible converters of the same type: 1 - single-quadrant voltage lowering converters (hydraulic analogy, study with ideal elements, full scheme with input and output filters); 2 - single-quadrant voltage raising converters (hydraulic analogy, operation); 3 - two quadrants reversible converters (structure construction, quadrants of operation, reversible converter connected to a DC motor); 4 - four-quadrants reversible converters; 5 - other converters structure (current converters and converters with intermediate storage, asymmetrical converters, converters with capacitive storage, insulated converters, resonating converters, status); 6 - conclusion. (J.S.)

  1. A resonant dc-dc power converter assembly

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a resonant DC-DC power converter assembly comprising a first resonant DC-DC power converter and a second resonant DC-DC power converter having identical circuit topologies. A first inductor of the first resonant DC-DC power converter and a second inductor...... of the second resonant DC-DC power converter are configured for magnetically coupling the first and second resonant DC-DC power converters to each other to forcing substantially 180 degrees phase shift, or forcing substantially 0 degree phase shift, between corresponding resonant voltage waveforms of the first...... and second resonant DC-DC power converters. The first and second inductors are corresponding components of the first and second resonant DC-DC power converters....

  2. The Principal Component Analysis of Trace Elements in Asteraceae Chinese Medicinal Herbs with Anti-HIV Activity%五种抗HIV活性菊科中草药微量元素主成分分析

    Institute of Scientific and Technical Information of China (English)

    刘云华; 殷彩霞; 彭莉; 张仙; 黄红苹

    2013-01-01

    对具有抗HIV活性的菊科中草药艾叶、紫茎泽兰、臭灵丹、叶下花、辣子草进行微量元素含量测定、含量间相关性分析和主成分分析,找出微量元素主成分的影响.再根据主成分值和综合评价值进行二维聚类,发现微量元素含量与抗HIV活性呈一定正相关.为药用菊科资源的开发与利用提供了理论依据.%Folium artemisiac Argri.,Eupatorium adenophorum Spreng.,Laggera pterodonta (DC)Benth.,Ainsliaea pertyoides Franch.and Galinsoga payviflora Cav.belong to asteraceae with anti-HIV activity.The content determination,content correlation analysis and principal component analysis of trace elements were carried out to find the action of the principal components of trace elements in the five asteraceae herbs.Then,a dimensional clustering analysis was done on the grounds of principal component values and comprehensive evaluation values.The results showed that there was a positive correlation between trace elements content and anti-HIV activity.This paper provided a reference for the development and utilization of the resources of asteraceae herbs.

  3. Charge pump DC-DC converter comprising solid state batteries

    NARCIS (Netherlands)

    Reefman, D.; Roozeboom, F.; Notten, P.H.L.; Klootwijk, J.H.

    2013-01-01

    An electronic device is provided which comprises a DC-DC converter. The DC-DC converter comprises at least one solid-state rechargeable battery (B1, B2) for storing energy for the DC-DC conversion and an output capacitor (C2).

  4. Meiotic analysis of the germoplasm of three medicinal species from Asteraceae family Análise meiótica do germoplasma de três espécies medicinais da família Asteraceae

    Directory of Open Access Journals (Sweden)

    Denise Olkoski

    2008-09-01

    Full Text Available Cytogenetic characterization was carried out on 12 accessions from Aster squamatus (Spreng. Hieron., Pterocaulon polystachyum DC, and Solidago microglossa DC by studying their meiotic behavior and pollen viability. These species are from the Asteraceae family, native to Rio Grande do Sul State, Brazil, and are important for medicinal use. Young inflorescences with four accessions of each species were collected, fixed in ethanol-acetic acid (3:1, and conserved in ethanol 70% until use. The method used was that of squashing the anthers and coloring with acetic orcein 2%. Meiosis was regular in all accessions, presenting chromosomal associations preferentially bivalent, where n=10 was found for Aster squamatus and n=9 for Pterocaulon polystachyum, and Solidago microglossa. The studied accessions presented a Meiotic Index (MI that varied from 65% to 87% in Aster squamatus, 85% to 92% in Pterocaulon polystachyum, and 64% to 92% in Solidago microglossa, indicating meiotic stability, although irregularities appeared during the cellular division. The pollen viability estimative was high in all studied accessions. These results indicate that the studied species can be included in future studies of genetic breeding.Foi realizada a caracterização citogenética de doze acessos de Aster squamatus, Pterocaulon polystachyum e Solidago microglossa, espécies da família Asteraceae, nativas do Rio Grande do Sul, Brasil, por meio do estudo do comportamento meiótico e da viabilidade polínica, que possuem grande importância para uso medicinal. Inflorescências jovens de quatro acessos de cada espécie foram fixadas em álcool-ácido acético (3:1 e conservadas em álcool 70% até o uso. O método utilizado foi o de esmagamento de anteras e a coloração com orceína acética 2%. A meiose foi regular em todos os acessos, apresentando associações cromossômicas preferencialmente em bivalentes, encontrando-se n=10 para Aster squamatus e n=9 para Pterocaulon

  5. DC source assemblies

    Science.gov (United States)

    Campbell, Jeremy B; Newson, Steve

    2013-02-26

    Embodiments of DC source assemblies of power inverter systems of the type suitable for deployment in a vehicle having an electrically grounded chassis are provided. An embodiment of a DC source assembly comprises a housing, a DC source disposed within the housing, a first terminal, and a second terminal. The DC source also comprises a first capacitor having a first electrode electrically coupled to the housing, and a second electrode electrically coupled to the first terminal. The DC source assembly further comprises a second capacitor having a first electrode electrically coupled to the housing, and a second electrode electrically coupled to the second terminal.

  6. Terpenoids, flavonoids and other constituents of Eupatorium betonicaeforme (Asteraceae)

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque, Maria Rose Jane R.; Pires, Andreza Maria L.; Pessoa, Otilia Deusdenia L.; Silveira, Edilberto R. [Ceara Univ., Fortaleza, CE (Brazil). Dept. de Quimica Organica e Inorganica. Curso de Pos-Graduacao em Quimica Organica]. E-mail: opessoa@ufc.br

    2006-01-15

    A new acylated kaurene diterpene, characterized as 15{alpha}-decanoyloxy-kaur-16-en-19-oic acid, along with nine known compounds: pentacosanoic acid, 24{alpha}-ethyl-5{alpha}-cholesta-7,22E-dien-3{beta}-ol, 15{alpha}-hydroxy-kaur-16-en-19-oic acid, 8{beta}-angeloyloxy-9{beta},10{beta}-dihydroxy-1-oxogermacra-4E,11(13)dien-12,6{alpha}-olide, 3{beta}-hydroxyeicosan-1,5{beta}-olide, taraxasteryl acetate, 7-Omethylkaempferol, kaempferol, and nepetin were isolated from the flowers of Eupatorium betonicaeforme (Asteraceae). In addition, from the aerial parts were isolated taraxasteryl acetate and {alpha}- and {beta}-amyrin, while the mixture of {beta}-sitosterol and stigmasterol, and 6-acetyl-2,2-dimethylchroman-4-one were isolated from the roots. The structure elucidation of all compounds was performed by spectroscopic analysis and comparison with published data from literature. (author)

  7. Die Plantfamilie Asteraceae: 4 Interessante groeivorme en ekonomies belangrike soorte

    Directory of Open Access Journals (Sweden)

    P. P.J. Herman

    2002-09-01

    Full Text Available Die plantfamilie Asteraceae bevat ’n ryke verskeidenheid en interessante groeivorme soos eenjarige en meerjarige kruide, dwergstruike, struike, bome, slingerplante, sukkulente, waterplante, rosetplante, kussingplante, heide-agtige plante, platgroeiend, grasagtig  en doringrig. Die blare vertoon ook baie variasie in vorm en ander kenmerke byvoorbeeld afwisselend, teenoorstaande, saamgepak, sittend, gesteeld, enkelvoudig, gaafrandig, getand, gelob of diep verdeeld, saamgesteld, met drie tot vyf hoofare, gereduseer of heeltemal afwesig, glad of baie harig op die boonste of onderste oppervlakke. Soms is melksap teenwoordig en sommiges is aromaties. Sommige verteenwoordigers van die familie is ekonomies belangrik; sommiges is eetbaar of word vir medisyne gebruik terwyl ander giftig is, sommiges word as veevoer benut maar ander is onkruide en die hout van sommiges is in die verlede gebruik.

  8. Research of polysaccharide complexes from asteraceae family plants

    Directory of Open Access Journals (Sweden)

    Світлана Михайлівна Марчишин

    2015-10-01

    Full Text Available Aim of research. Depth study of polysaccharides in some little-known plant species of Asteraceae family is pressing question, considering that polysaccharides are important biologically active compounds widely used in pharmaceutical and medical practice as remedies and preventive medications. The aim of research was to determinate both quantitative content and monomeric composition of polysaccharide complexes from Asteraceae family plant species – Tagetes genus, Arnica genus, and Bellis genus.Materials and methods. Determination of polysaccharides was carried out by the precipitation reaction, using 96 % ethyl alcohol P and Fehling's solution after acid hydrolysis; quantitative content of this group of compounds was determined by gravimetric analysis. On purpose to identify the monomeric composition hydrolysis under sulfuric acid conditions was conducted. Qualitative monomeric composition of polysaccharides after hydrolysis was carried out by paper chromatography method in n-Butanol – Pyridine – Distilled water P (6:4:3 system along with saccharides reference samples.Results. Polysaccharide complexes from Tagetes erecta, Tagetes patula, Tagetes tenuifolia, Arnica montana, Arnica foliosa, wild and cultivated Bellis perennis herbs were studied. Water-soluble polysaccharides and pectin fractions were isolated from studied objects; their quantitative content and monomeric composition were determined.Conclusion. The highest amount of water-soluble polysaccharides was found in cultivated Bellis perennis herb (10,13 %, the highest amount of pectin compounds – in Tagetes tenuifolia herb (13,62 %; the lowest amount of water-soluble polysaccharides and pectin compounds was found in Arnica montana herb (4,61 % and Tagetes patula herb (3,62 %, respectively. It was found that polysaccharide complexes from all studied species include glucose and arabinose

  9. Antioxidant, Anticholinesterase and Antibacterial Activities of Jurinea consanguinea DC

    Directory of Open Access Journals (Sweden)

    Hülya Öztürk

    2011-01-01

    Full Text Available The aim of this study was to investigate in vitro antioxidant, anticholinesterase and antibacterial activities of the petroleum ether, chloroform and methanol extracts obtained from the aerial parts of Jurinea consanguinea DC. (Asteraceae. Total phenolic and flavonoid contents of these crude extracts were determined as pyrocatechol and quercetin equivalents, respectively. The methanol extract which possessed almost the same effect with the chloroform extract in b -carotene-linoleic acid system exhibited higher free radical scavenging activity than a standard compound, BHT, at 100 and 200 m g/mL concentrations. The petroleum ether extract showed the highest acetylcholinesterase inhibitory activity among the tested extracts. The methanol extract exhibited higher butyrylcholinesterase inhibitory activity than galantamine at all concentrations (94% inhibition at 200 m g/mL. The antibacterial activity of the extracts was determined by the disc diffusion method. The chloroform extract showed moderate activity against B. subtilis, P. aeruginosa and S. aureus.

  10. Antimoulting Activity of Eremanthus erythropappus (DC. MacLeisch

    Directory of Open Access Journals (Sweden)

    Danielle Barbosa

    2012-06-01

    Resumo. Os extratos e metabólitos secundários de plantas podem agir como agentes tóxicos e inibidores do da alimentação e do desenvolvimento em insetos. Neste estudo foi utilizado Oncopeltus fasciatus (Dallas (Hemiptera como modelo experimental a fim de avaliar as atividades do extrato etanólico bruto e frações obtidos das flores ou caules de Eremanthus erythropappus (DC. MacLeisch (Asteraceae, na mortalidade e sobre o desenvolvimento do inseto. A fração butanólica obtida do extrato etanólico mostrou toxidade sobre as ninfas de O. fasciatus, bem como atividade de inibição do crescimento. Os resultados sugerem que a fração butanólica de E. erythropappus possui substâncias ativas sobre a fisiologia, crescimento e desenvolvimento de insetos.

  11. Phytochemistry and quantification of polyphenols in extracts of the Asteraceae weeds from Diamantina, Minas Gerais state, Brazil

    OpenAIRE

    Petacci,F.; Tavares,W.S.; Freitas,S. S.; Teles,A.M.; Serrão,J.E.; J. C. Zanuncio

    2012-01-01

    Asteraceae weeds are rich in chemicals that have biological and pharmaceutical activities. The aims of this work were to describe the phytochemistry and quantify the polyphenols in ethanol extracts from leaves of 12 species of Asteraceae weeds collected in Diamantina, Minas Gerais State, Brazil. The screening of Asteraceae extracts revealed the presence of tannins, steroids, triterpenes, anthocyanins, and flavonoids. The total phenolic content was high in extracts of Lychnophora ericoides (14...

  12. Radiation effects on DC-DC Converters

    Science.gov (United States)

    Zhang, Dexin; Attia, John O.; Kankam, Mark D. (Technical Monitor)

    2000-01-01

    DC-DC switching converters are circuits that can be used to convert a DC voltage of one value to another by switching action. They are increasing being used in space systems. Most of the popular DC-DC switching converters utilize power MOSFETs. However power MOSFETs, when subjected to radiation, are susceptible to degradation of device characteristics or catastrophic failure. This work focuses on the effects of total ionizing dose on converter performance. Four fundamental switching converters (buck converter, buck-boost converter, cuk converter, and flyback converter) were built using Harris IRF250 power MOSFETs. These converters were designed for converting an input of 60 volts to an output of about 12 volts with a switching frequency of 100 kHz. The four converters were irradiated with a Co-60 gamma source at dose rate of 217 rad/min. The performances of the four converters were examined during the exposure to the radiation. The experimental results show that the output voltage of the converters increases as total dose increases. However, the increases of the output voltage were different for the four different converters, with the buck converter and cuk converter the highest and the flyback converter the lowest. We observed significant increases in output voltage for cuk converter at a total dose of 24 krad (si).

  13. 75 FR 61989 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-8-31, DC-8-32, DC-8-33, DC-8-41...

    Science.gov (United States)

    2010-10-07

    ... Corporation Model DC- 8-31, DC-8-32, DC-8-33, DC-8-41, DC-8-42, and DC-8-43 Airplanes; Model DC-8-50 Series Airplanes; Model DC-8F-54 and DC-8F-55 Airplanes; Model DC-8-60 Series Airplanes; Model DC-8-60F Series Airplanes; Model DC-8- 70 Series Airplanes; and Model DC-8-70F Series Airplanes AGENCY:......

  14. 75 FR 36298 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-8-31, DC-8-32, DC-8-33, DC-8-41...

    Science.gov (United States)

    2010-06-25

    ... Corporation Model DC- 8-31, DC-8-32, DC-8-33, DC-8-41, DC-8-42, and DC-8-43 Airplanes; Model DC-8-50 Series Airplanes; Model DC-8F-54 and DC-8F-55 Airplanes; Model DC-8-60 Series Airplanes; Model DC-8-61 Series Airplanes; Model DC-8-70 Series Airplanes; and Model DC-8-70F Series Airplanes AGENCY:......

  15. A DC Transformer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — During the period of this project three different possible DC transformer concepts were proposed, theoretically modeled, and then experimentally tested with the...

  16. An extinct Eocene taxon of the daisy family (Asteraceae): evolutionary, ecological and biogeographical implications

    Science.gov (United States)

    Barreda, Viviana D.; Palazzesi, Luis; Katinas, Liliana; Crisci, Jorge V.; Tellería, María C.; Bremer, Kåre; Passala, Mauro G.; Bechis, Florencia; Corsolini, Rodolfo

    2012-01-01

    Background and Aims Morphological, molecular and biogeographical information bearing on early evolution of the sunflower alliance of families suggests that the clade containing the extant daisy family (Asteraceae) differentiated in South America during the Eocene, although palaeontological studies on this continent failed to reveal conclusive support for this hypothesis. Here we describe in detail Raiguenrayun cura gen. & sp. nov., an exceptionally well preserved capitulescence of Asteraceae recovered from Eocene deposits of northwestern Patagonia, Argentina. Methods The fossil was collected from the 47·5 million-year-old Huitrera Formation at the Estancia Don Hipólito locality, Río Negro Province, Argentina. Key Results The arrangement of the capitula in a cymose capitulescence, the many-flowered capitula with multiseriate–imbricate involucral bracts and the pappus-like structures indicate a close morphological relationship with Asteraceae. Raiguenrayun cura and the associated pollen Mutisiapollis telleriae do not match exactly any living member of the family, and clearly represent extinct taxa. They share a mosaic of morphological features today recognized in taxa phylogenetically close to the root of Asteraceae, such as Stifftieae, Wunderlichioideae and Gochnatieae (Mutisioideae sensu lato) and Dicomeae and Oldenburgieae (Carduoideae), today endemic to or mainly distributed in South America and Africa, respectively. Conclusions This is the first fossil genus of Asteraceae based on an outstandingly preserved capitulescence that might represent the ancestor of Mutisioideae–Carduoideae. It might have evolved in southern South America some time during the early Palaeogene and subsequently entered Africa, before the biogeographical isolation of these continents became much more pronounced. The new fossil represents the first reliable point for calibration, favouring an earlier date to the split between Barnadesioideae and the rest of Asteraceae than previously

  17. Radiation Effects on DC-DC Converters

    Science.gov (United States)

    Zhang, De-Xin; AbdulMazid, M. D.; Attia, John O.; Kankam, Mark D. (Technical Monitor)

    2001-01-01

    In this work, several DC-DC converters were designed and built. The converters are Buck Buck-Boost, Cuk, Flyback, and full-bridge zero-voltage switched. The total ionizing dose radiation and single event effects on the converters were investigated. The experimental results for the TID effects tests show that the voltages of the Buck Buck-Boost, Cuk, and Flyback converters increase as total dose increased when using power MOSFET IRF250 as a switching transistor. The change in output voltage with total dose is highest for the Buck converter and the lowest for Flyback converter. The trend of increase in output voltages with total dose in the present work agrees with those of the literature. The trends of the experimental results also agree with those obtained from PSPICE simulation. For the full-bridge zero-voltage switch converter, it was observed that the dc-dc converter with IRF250 power MOSFET did not show a significant change of output voltage with total dose. In addition, for the dc-dc converter with FSF254R4 radiation-hardened power MOSFET, the output voltage did not change significantly with total dose. The experimental results were confirmed by PSPICE simulation that showed that FB-ZVS converter with IRF250 power MOSFET's was not affected with the increase in total ionizing dose. Single Event Effects (SEE) radiation tests were performed on FB-ZVS converters. It was observed that the FB-ZVS converter with the IRF250 power MOSFET, when the device was irradiated with Krypton ion with ion-energy of 150 MeV and LET of 41.3 MeV-square cm/mg, the output voltage increased with the increase in fluence. However, for Krypton with ion-energy of 600 MeV and LET of 33.65 MeV-square cm/mg, and two out of four transistors of the converter were permanently damaged. The dc-dc converter with FSF254R4 radiation hardened power MOSFET's did not show significant change at the output voltage with fluence while being irradiated by Krypton with ion energy of 1.20 GeV and LET of 25

  18. 75 FR 38943 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-30, DC...

    Science.gov (United States)

    2010-07-07

    ... Corporation Model DC- 10-10, DC-10-10F, DC-10-30, DC-10-30F (KDC-10), DC-10-40, and DC-10-40F Airplanes AGENCY... propose to adopt a new airworthiness directive (AD) for certain Model DC-10-10, DC-10-10F, DC-10-30, DC-10-30F (KDC-10), DC-10- 40, and DC-10-40F airplanes. This proposed AD would require......

  19. Evaluating the feasibility of using candidate DNA barcodes in discriminating species of the large Asteraceae family

    Directory of Open Access Journals (Sweden)

    Liu Chang

    2010-10-01

    Full Text Available Abstract Background Five DNA regions, namely, rbcL, matK, ITS, ITS2, and psbA-trnH, have been recommended as primary DNA barcodes for plants. Studies evaluating these regions for species identification in the large plant taxon, which includes a large number of closely related species, have rarely been reported. Results The feasibility of using the five proposed DNA regions was tested for discriminating plant species within Asteraceae, the largest family of flowering plants. Among these markers, ITS2 was the most useful in terms of universality, sequence variation, and identification capability in the Asteraceae family. The species discriminating power of ITS2 was also explored in a large pool of 3,490 Asteraceae sequences that represent 2,315 species belonging to 494 different genera. The result shows that ITS2 correctly identified 76.4% and 97.4% of plant samples at the species and genus levels, respectively. In addition, ITS2 displayed a variable ability to discriminate related species within different genera. Conclusions ITS2 is the best DNA barcode for the Asteraceae family. This approach significantly broadens the application of DNA barcoding to resolve classification problems in the family Asteraceae at the genera and species levels.

  20. Vernonia condensata Baker (Asteraceae: A Promising Source of Antioxidants

    Directory of Open Access Journals (Sweden)

    Jucélia Barbosa da Silva

    2013-01-01

    Full Text Available The present study evaluated the antioxidant potential of Vernonia condensata Baker (Asteraceae. Dried and powdered leaves were exhaustively extracted with ethanol by static maceration followed by partition to obtain the hexane, dichloromethane, ethyl acetate, and butanol fractions. Total phenols and flavonoids contents were determined through spectrophotometry and flavonoids were identified by HPLC-DAD system. The antioxidant activity was assessed by DPPH radical scavenging activity, TLC-bioautography, reducing power of Fe+3, phosphomolybdenum, and TBA assays. The total phenolic content and total flavonoids ranged from 0.19 to 23.11 g/100 g and from 0.13 to 4.10 g/100 g, respectively. The flavonoids apigenin and luteolin were identified in the ethyl acetate fraction. The IC50 of DPPH assay varied from 4.28 to 75.10 µg/mL and TLC-bioautography detected the antioxidant compounds. The reducing power of Fe+3 was 19.98 to 336.48 μg/mL, while the reaction with phosphomolybdenum ranged from 13.54% to 32.63% and 56.02% to 135.00% considering ascorbic acid and rutin as reference, respectively. At 30 mg/mL, the ethanolic extract and fractions revealed significant effect against lipid peroxidation. All these data sustain that V. condensata is an important and promising source of bioactive substances with antioxidant activity.

  1. Ovules anatomy of selected apomictic taxa from Asteraceae family

    Directory of Open Access Journals (Sweden)

    Krystyna Musiał

    2013-04-01

    Full Text Available The present paper reports on our observations on the ovule structure of autonomous obligatory apomicts. We analyzed two triploid species of Taraxacum: T. udum, T. alatum and two triploid species of Chondrilla: Ch. juncea, Ch. brevirostris . The ovules of all studied species show a structure typical for the members of Asteraceae. One basal ovule develops into an inferior and unilocular ovary. The ovule is anatropous, tenuinucellate and unitegmic. Structural changes were observed in the ovule at the time of the embryo sac maturation. The innermost layer of integument develops into an endothelium surrounding the female gametophyte. Moreover, considerable modifications occurred in the integumentary cell layers adjacent to the endothelium. These cells show signs of programmed cell death and their walls begin to thicken. Histological analysis revealed that the prominent thick cell walls were rich in pectins. Layers of thick-walled cells formed a special storage tissue which, most likely, is an additional source of nutrients necessary for the proper nourishment of a female gametophyte and then of a proembryo.

  2. Anatomy of ovary and ovule in dandelions (Taraxacum, Asteraceae).

    Science.gov (United States)

    Musiał, K; Płachno, B J; Świątek, P; Marciniuk, J

    2013-06-01

    The genus Taraxacum Wigg. (Asteraceae) forms a polyploid complex within which there are strong links between the ploidy level and the mode of reproduction. Diploids are obligate sexual, whereas polyploids are usually apomictic. The paper reports on a comparative study of the ovary and especially the ovule anatomy in the diploid dandelion T. linearisquameum and the triploid T. gentile. Observations with light and electron microscopy revealed no essential differences in the anatomy of both the ovary and ovule in the examined species. Dandelion ovules are anatropous, unitegmic and tenuinucellate. In both sexual and apomictic species, a zonal differentiation of the integument is characteristic of the ovule. In the integumentary layers situated next to the endothelium, the cell walls are extremely thick and PAS positive. Data obtained from TEM indicate that these special walls have an open spongy structure and their cytoplasm shows evidence of gradual degeneration. Increased deposition of wall material in the integumentary cells surrounding the endothelium takes place especially around the chalazal pole of the embryo sac as well as around the central cell. In contrast, the integumentary cells surrounding the micropylar region have thin walls and exhibit a high metabolic activity. The role of the thick-walled integumentary layers in the dandelion ovule is discussed. We also consider whether this may be a feature of taxonomic importance.

  3. Radiation-Tolerant DC-DC Converters

    Science.gov (United States)

    Skutt, Glenn; Sable, Dan; Leslie, Leonard; Graham, Shawn

    2012-01-01

    A document discusses power converters suitable for space use that meet the DSCC MIL-PRF-38534 Appendix G radiation hardness level P classification. A method for qualifying commercially produced electronic parts for DC-DC converters per the Defense Supply Center Columbus (DSCC) radiation hardened assurance requirements was developed. Development and compliance testing of standard hybrid converters suitable for space use were completed for missions with total dose radiation requirements of up to 30 kRad. This innovation provides the same overall performance as standard hybrid converters, but includes assurance of radiation- tolerant design through components and design compliance testing. This availability of design-certified radiation-tolerant converters can significantly reduce total cost and delivery time for power converters for space applications that fit the appropriate DSCC classification (30 kRad).

  4. Bidirectional dc-to-dc Power Converter

    Science.gov (United States)

    Griesbach, C. R.

    1986-01-01

    Solid-state, series-resonant converter uses high-voltage thyristors. Converter used either to convert high-voltage, low-current dc power to lowvoltage, high current power or reverse. Taking advantage of newly-available high-voltage thyristors to provide better reliability and efficiency than traditional converters that use vacuum tubes as power switches. New converter essentially maintenance free and provides greatly increased mean time between failures. Attractive in industrial applications whether or not bidirectional capability is required.

  5. Forback DC-to-DC converter

    Science.gov (United States)

    Lukemire, Alan T.

    1995-05-01

    A pulse-width modulated DC-to-DC power converter including a first inductor, i.e. a transformer or an equivalent fixed inductor equal to the inductance of the secondary winding of the transformer, coupled across a source of DC input voltage via a transistor switch which is rendered alternately conductive (ON) and nonconductive (OFF) in accordance with a signal from a feedback control circuit is described. A first capacitor capacitively couples one side of the first inductor to a second inductor which is connected to a second capacitor which is coupled to the other side of the first inductor. A circuit load shunts the second capacitor. A semiconductor diode is additionally coupled from a common circuit connection between the first capacitor and the second inductor to the other side of the first inductor. A current sense transformer generating a current feedback signal for the switch control circuit is directly coupled in series with the other side of the first inductor so that the first capacitor, the second inductor and the current sense transformer are connected in series through the first inductor. The inductance values of the first and second inductors, moreover, are made identical. Such a converter topology results in a simultaneous voltsecond balance in the first inductance and ampere-second balance in the current sense transformer.

  6. Forback DC-to-DC converter

    Science.gov (United States)

    Lukemire, Alan T. (Inventor)

    1993-01-01

    A pulse-width modulated DC-to-DC power converter including a first inductor, i.e. a transformer or an equivalent fixed inductor equal to the inductance of the secondary winding of the transformer, coupled across a source of DC input voltage via a transistor switch which is rendered alternately conductive (ON) and nonconductive (OFF) in accordance with a signal from a feedback control circuit is described. A first capacitor capacitively couples one side of the first inductor to a second inductor which is connected to a second capacitor which is coupled to the other side of the first inductor. A circuit load shunts the second capacitor. A semiconductor diode is additionally coupled from a common circuit connection between the first capacitor and the second inductor to the other side of the first inductor. A current sense transformer generating a current feedback signal for the switch control circuit is directly coupled in series with the other side of the first inductor so that the first capacitor, the second inductor and the current sense transformer are connected in series through the first inductor. The inductance values of the first and second inductors, moreover, are made identical. Such a converter topology results in a simultaneous voltsecond balance in the first inductance and ampere-second balance in the current sense transformer.

  7. Ethnopharmacological survey and phytochemical screening of some medicinal Asteraceae from Algerian Sahara

    Directory of Open Access Journals (Sweden)

    A. CHERITI

    2013-06-01

    Full Text Available A first report of Asteraceae species census of the Algerian folk medicine, currently used in Sahara for the treatment of illenes is presented. 11 Asteraceae species namely: Anvillea radiata Coss, Artemisia herba-alba, Brocchia cinerea, Bubonium graveolens, Cotula anthemoides, Echinops spinosus, Launaea arborescens, Launaea nudicaulis, Launaea resedifolia, Scorzonera undulata and Warionia saharae were selected based on the survey through interviews with local inhabitant, herbalist in the Souk and old women according to our previous works. Ethnopharmacolgical potential and chemical constituents of this species are described.

  8. Ethnopharmacological survey and phytochemical screening of some medicinal Asteraceae from Algerian Sahara

    Directory of Open Access Journals (Sweden)

    A CHERITI

    2013-06-01

    Full Text Available A first report of Asteracea species census of the Algerian folk medicine, currently used in Sahara for the treatment of illenes is presented. 11 Asteraceae species namely: Anvillea radiata coss, Artemisia herba-alba, Brocchia cinerea, Bubonium graveolens, Cotula anthemoides, Echinops spinosus, Launaea arborescens, Launaea nudicaulis, Launaea resedifolia, Scorzonera undulata and Warionia saharae were selected based on the survey through interviews with local inhabitant, herbalist in the Souk and old women according to our previous works. Ethnopharmacolgical potential and chemical constituents of this species are described.

  9. LA FAMILIA ASTERACEAE EN LA FLORA DEL BAJÍO Y DE REGIONES ADYACENTES

    OpenAIRE

    José Luis Villaseñor; Enrique Ortiz

    2012-01-01

    Con base en ejemplares de herbario recolectados, identificados y georreferenciados provenientes del territorio considerado por el proyecto Flora del Bajío y de regiones adyacentes, se analiza la riqueza de Asteraceae conocida en dicha región. Utilizando una división de la región en cuadros de 0.5° x 0.5°, el objetivo fue identificar los sitios de alta diversidad para la familia. La región tiene documentadas, con los ejemplares de herbario revisados, 681 especies de Asteraceae, distribuidas en...

  10. Intelligent dc-dc Converter Technology Developed and Tested

    Science.gov (United States)

    Button, Robert M.

    2001-01-01

    The NASA Glenn Research Center and the Cleveland State University have developed a digitally controlled dc-dc converter to research the benefits of flexible, digital control on power electronics and systems. Initial research and testing has shown that conventional dc-dc converters can benefit from improved performance by using digital-signal processors and nonlinear control algorithms.

  11. Pharmacological characterization of Cirsium ligulare Boiss. (Asteraceae herb decoction

    Directory of Open Access Journals (Sweden)

    Dobrić Silva

    2017-01-01

    Full Text Available Background/Aim. Data on phytochemical and pharmacological investigations of genus Cirsium Mill. (Asteraceae are scarce. Some data suggest that decoctions or infusions prepared from these plants are used in folk medicine as tonics, particularly in inflammatory, liver and stomach diseases. So far there have been no pharmacological investigations related to Cirsium ligulare (C. ligulare Boiss. Accordingly, the aim of this study was to estimate antioxidative, anti-inflammatory and gastroprotective activities of aqueous extracts of C. ligulare herb prepared as 5% and 10% decoctions. Methods. Antioxidative activity was determined using the method of 2,2-diphenyl-1-picrylhydrazyl (DPPH radical scavenging. Investigations of anti-inflammatory (a model of systemic inflammatory response induced by endotoxin of Escherichia coli and carrageenan-induced rat paw oedema model for local inflammatory response, as well as gastroprotective effects (a model of stress-ulcer induced by absolute ethanol, were conducted in adult female Wistar rats that were given the aqueous extracts of C. ligulare herb per os. Indomethacin and ranitidine were used as reference drugs for evaluation of local anti-inflammatory and gastroprotective effects, respectively. Results. The results demonstrated that aqueous extracts of C. ligulare herb produced strong antioxidative activity, diminished body weight loss induced by endotoxin, significantly reduced carrageenan-induced paw oedema, and prevented the ulcerogenic action of absolute ethanol. Both anti-inflammatory and gastroprotective activities of the extract tested were comparable to those of the reference drugs. Conclusion. Presented results justify the traditional use of C. ligulare herb decoctions and further phytochemical and pharmacological investigations are warranted. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 173021

  12. 75 FR 20790 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

    Science.gov (United States)

    2010-04-21

    ... Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40, DC-10-40F... (AD) for certain Model DC-10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC- 10A and KDC-10), DC-10-40, DC-10-40F, MD-10-10F, MD-10-30F, MD-11, and MD-11F airplanes. This proposed......

  13. 75 FR 68246 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

    Science.gov (United States)

    2010-11-05

    ... Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40, DC-10-40F... to supersede an existing airworthiness directive (AD) that applies to all Model DC-10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40, DC-10-40F, MD-10-......

  14. Propriedades farmacológicas do extrato etanólico de Eremanthus erythropappus (DC. McLeisch (Asteraceae Pharmacological properties of the ethanol extract from Eremanthus erythropappus (DC. McLeisch (Asteraceae

    Directory of Open Access Journals (Sweden)

    Marcelo S. Silvério

    2008-09-01

    Full Text Available O presente trabalho investigou as propriedades antinociceptiva, antiinflamatória e antiulcerogênica do extrato etanólico dos galhos de E. erythropappus. Foram realizados os testes de contorções abdominais induzidas por ácido acético; tempo da lambida da pata induzida por formalina; placa quente; edema de pata induzido por carragenina; lesões ulcerativas induzidas por indometacina e etanol. As doses de 50, 100 e 200 mg/kg inibiram as contorções em 43,07%, 69,34% e 70,07%, respectivamente. O tempo da lambida da pata foi reduzido em ambas as fases nas doses testadas, enquanto o tempo de latência da placa quente teve efeito significativo na dose de 200 mg/kg. O edema de pata foi reduzido em 23,81% (100 mg/kg e 47,62% (200 mg/kg. O índice ulcerativo das lesões induzidas por indometacina foi reduzido na dose de 100 mg/kg e 200 mg/kg, enquanto a dose de 200 mg/kg teve efeito significativo sobre o volume e o pH do suco gástrico. O índice ulcerativo e o volume do suco gástrico, induzidos por etanol, foram reduzidos na dose de 200 mg/kg, enquanto o pH do suco gástrico aumentou nas doses de 100 e 200 mg/kg. Os resultados indicam que o extrato etanólico de E. erythropappus avaliado pode constituir alvo potencial para uso em terapias da dor, da inflamação e de úlcera.The present work investigated the antinociceptive, anti-inflammatory and antiulcerogenic activities of Eremanthus erythropappus ethanol extract. The tests were carried out by acetic acid writhing, paw licking induced by formalin, hot plate, indomethacin- and ethanol-induced ulcer. The doses of 50, 100 and 200 mg/kg inhibited the contortions in 43.07, 69.34 and 70.07%, respectively. Both phases of paw lick were reduced at the tested doses, while reaction time at hot plate had significant effect at 200 mg/kg. The paw edema was decreased in 23.81% (100 mg/kg and 47.62% (200 mg/kg. The index of ulceration induced by indomethacin was reduced at the doses of 100 and 200 mg/kg, while 200 mg/kg decreased the gastric volume and pH. The index of ulceration and gastric volume induced by ethanol was reduced at 200 mg/kg, while the pH increased at 100 and 200 mg/kg. The results indicate that the ethanol extract from E. erythropappus may constitute a potential target for the use in therapies of the pain, inflammation and ulcer.

  15. Three-port DC-DC converter with new integrated transformer for DC Distribution Systems

    DEFF Research Database (Denmark)

    Ouyang, Ziwei; Andersen, Michael A. E.

    2014-01-01

    A new integrated transformer for three-port dc-dc converter is proposed to overcome the power coupling effect existed in some known multiple inputs dc-dc converters. Orthogonal primary windings arrangement and in series connection of diagonal secondary Windings enables a fully power decoupling...

  16. On the distribution of Cerastium smolikanum (Caryophyllaceae) and Centaurea vlachorum (Asteraceae) in the Balkan Peninsula

    DEFF Research Database (Denmark)

    Shuka, Lulezim; Tan, Kit

    2009-01-01

    Cerastium smolikanum (Caryophyllaceae) and Centaurea vlachorum (Asteraceae) are reported for the first () and () are reported for the first time in C and NE Albania. These two taxa were previously considered serpentine endemics restricted to a few localities in NW Greece and the extension...

  17. Helichrysum yurterianum (Asteraceae, Inuleae), a new species from NE Anatolia, Turkey

    DEFF Research Database (Denmark)

    Gemici, Yusuf; Tan, Kit; Yildirim, Hasan

    2008-01-01

    Helichrysum yurterianum Y. Gemici, Kit Tan, H. Yildirim & M. Gemici (Asteraceae, Inuleae) is described and illustrated. It is a serpentine endemic restricted to the province of Erzincan in NE Anatolia, Turkey. Its affinities are with H. arenarium and H. noeanum, which both have a wider distribution...

  18. Jurinea micevskii (Asteraceae), a new species from the Republic of Macedonia

    DEFF Research Database (Denmark)

    Stevanovic, Vladimir; Matevski, Vlado; Tan, Kit

    2010-01-01

    Jurinea micevskii (Asteraceae) is described and illustrated as a new species endemic to Mt Galicica in the southwestern Republic of Macedonia. It resembles J. taygetea, a narrow endemic of Mt Taigetos in the Peloponnese, southern Greece and J. bocconei from Mt Madoníe in north central Sicily...

  19. Three new caespitose species of Senecio (Asteraceae, Senecioneae) from South Peru

    NARCIS (Netherlands)

    Montesinos, D.B.

    2014-01-01

    Three new species of the genus Senecio (Asteraceae, Senecioneae) belonging to S. ser. Suffruticosi subser. Caespitosi were discovered in the tributaries of the upper Tambo River, Moquegua Department, South Peru. Descriptions, diagnoses and discussions about their distribution, a table with the morph

  20. Two Newly Recorded Species of Synotis (Asteraceae-Senecioneae) in China%中国合耳菊属(菊科-千里光族)两新记录种

    Institute of Scientific and Technical Information of China (English)

    唐明; 杨亲二

    2014-01-01

    Two species of the genus Synotis (Asteraceae-Senecioneae), S. rufinervis (DC.) C. Jeffrey&Y. L. Chen and S. kunthiana (Wall. ex DC.) C. Jeffrey&Y. L. Chen, are reported from China for the ifrst time. In China, both species are currently known only from southern Xizang (Tibet). We provide descriptions, illustrations and distributional map in China for the two species. Two important lforal micromorphological characters, anther-collar conifguration and anther endothecial tissue cell wall thickenings, are also given for the two species.%首次报道了红脉合耳菊[Synotis rufinervis (DC.) C. Jeffrey&Y. L. Chen]和须弥合耳菊[S. kunthiana (Wall. ex DC.) C. Jeffrey&Y. L. Chen](菊科-千里光族)在中国的分布记录。两种植物都在中国西藏南部有分布。提供了它们的详细形态描述、形态特征图及其在中国的地理分布,同时报道了两种植物的花药领构型和花药内壁细胞增厚方式。

  1. Overview of Multi-DC-Bus Solutions for DC Microgrids

    DEFF Research Database (Denmark)

    Ricchiuto, D.; Mastromauro, R.A.; Liserre, Marco;

    2013-01-01

    DC Microgrids have recently received a lot of attention in the last years due to high penetration of renewable energy sources as well as distributed energy storage systems. In the future DC microgrids could be preferable respect to AC microgrids in terms of redundancy since multi-DC-Bus solutions...... could provide a continuative power supply to the loads. An overview of Multi-DC-Bus solutions is presented in this paper. The performances are compared on the basis of possible DC microgrid configurations, redundancy, different DC voltage levels....

  2. 75 FR 60602 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

    Science.gov (United States)

    2010-10-01

    ... Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40, DC-10-40F.... ACTION: Final rule. SUMMARY: We are adopting a new airworthiness directive (AD) for certain Model DC-10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40,......

  3. 75 FR 23571 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

    Science.gov (United States)

    2010-05-04

    ... Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40, DC-10-40F.... ACTION: Final rule. SUMMARY: We are adopting a new airworthiness directive (AD) for certain Model DC-10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40,......

  4. DC-DC powering for the CMS pixel upgrade

    Science.gov (United States)

    Feld, Lutz; Fleck, Martin; Friedrichs, Marcel; Hensch, Richard; Karpinski, Waclaw; Klein, Katja; Rittich, David; Sammet, Jan; Wlochal, Michael

    2013-12-01

    The CMS experiment plans to replace its silicon pixel detector with a new one with improved rate capability and an additional detection layer at the end of 2016. In order to cope with the increased number of detector modules the new pixel detector will be powered via DC-DC converters close to the sensitive detector volume. This paper reviews the DC-DC powering scheme and reports on the ongoing R&D program to develop converters for the pixel upgrade. Design choices are discussed and results from the electrical and thermal characterisation of converter prototypes are shown. An emphasis is put on system tests with up to 24 converters. The performance of pixel modules powered by DC-DC converters is compared to conventional powering. The integration of the DC-DC powering scheme into the pixel detector is described and system design issues are reviewed.

  5. DC-DC Powering for the CMS Pixel Upgrade

    CERN Document Server

    Feld, Lutz Werner; Marcel Friedrichs; Richard Hensch; Karpinski, Waclaw; Klein, Katja; Rittich, David Michael; Sammet, Jan Domenik; Wlochal, Michael

    2013-01-01

    The CMS experiment plans to replace its silicon pixel detector with a new one with improved rate capability and an additional detection layer at the end of 2016. In order to cope with the increased number of detector modules the new pixel detector will be powered via DC-DC converters close to the sensitive detector volume. This paper reviews the DC-DC powering scheme and reports on the ongoing R and D program to develop converters for the pixel upgrade. Design choices are discussed and results from the electrical and thermal characterisation of converter prototypes are shown. An emphasis is put on system tests with up to24 converters. The performance of pixel modules powered by DC-DC converters is compared to conventional powering. The integration of the DC-DC powering scheme into the pixel detector is described and system design issues are reviewed.

  6. [Fungistatic activity of a sesquiterpene lactone (tomentosin) isolated from fresh Inula viscosa (Asteraceae) flowers from the Puglia region].

    Science.gov (United States)

    Cafarchia, C; De Laurentis, N; Milillo, M A; Losacco, V; Puccini, V

    2001-09-01

    A sesquiterpene lactone, tomentosin, has been isolated and identified form Inula viscosá Ait (Asteraceae) flowers. The molecule, at 1 mg/ml concentration, showed to be active in vitro against Microsporum canis, Microsporum gypseum and Trichophyton mentagrophytes.

  7. Asteraceae visited by honeybees in Argentina: a record from entomopalynological studies Asteraceae visitadas por abejas melíferas en Argentina: un registro a partir de estudios entomopalinológicos

    Directory of Open Access Journals (Sweden)

    María C. Telleria

    2009-07-01

    Full Text Available Entomopalynological studies of Asteraceae in Argentina revealed that 64 taxa occurred in food stored by honeybees. The most visited plant tribes were classified according to both the type of reward provided by the different taxa and the intensity that such reward is collected by honeybees. Exotic plant taxa were intensely visited inside the disturbed areas (e.g. Cardueae and Cichorieae tribes, whereas native taxa (e.g. Barnadesioideae, Mutisieae, Astereae and Eupatorieae were intensely visited in less disturbed areas. A large number of identified taxa of Asteraceae and the evaluation of its importance to honeybee nutrition were presented. The present study contributes to the knowledge of relationship between Asteraceae and honeybees.A partir de estudios entomopalinológicos se encontró que 64 taxa pertenecientes a la familia Asteraceae están presentes en los alimentos almacenados por las abejas melíferas. Los representantes exóticos fueron intensamente visitados en las áreas más alteradas (e.g. Cardueae and Cichorieae, mientras que algunos representantes nativos (e.g. Barnadesioideae, Mutisieae, Astereae y Eupatorieae fueron intensamente visitados en áreas menos alteradas. Se presenta un importante número de taxa de Asteraceae relevantes para la nutrición de las abejas melíferas. El presente trabajo contribuye a conocer la relación entre Asteraceae y abejas melíferas.

  8. Historical biogeography of Asteraceae from Tandilia and Ventania mountain ranges (Buenos Aires, Argentina

    Directory of Open Access Journals (Sweden)

    Crisci V. Jorge

    2001-07-01

    Full Text Available Las sierras septentrionales, o de Tandilia y las australes, o de Ventania, caracterizadas por su gran diversidad orgánica y su alto número de endemismos, están ubicadas en la planicie bonaerense de pastizales denominada "pampa". Con el objeto de establecer las relaciones entre Tandilia y Ventania con otras áreas, se analizaron las distribuciones de los taxones específicos e infraespecíficos de Asteraceae que habitan estas sierras. Se delimitaron trece áreas: sur de América del Norte y América Central, sur de Brasil, Uruguay, Pampa, Tandilia, Ventania, Chaco, Sierras Pampeanas, Sierras Subandinas, Mahuidas, Patagonia, Chile Central, y Andes del Norte. Las unidades de estudio fueron 112 taxones de Asteraceae presentes en Tandilia y Ventania (taxones endémicos, adventicios y naturalizados no fueron incluidos en el análisis. Las distribuciones de estos taxones fueron analizadas utilizando dos métodos: panbiogeografía compatibilidad de trazos y análisis de simplicidad de endemismos. Ambos métodos conectan sur de Brasil, Uruguay, Pampa, Tandilia, Ventania y Sierras Pampeanas. Las Asteraceae de Tandilia y Ventania estarían más relacionadas con estas áreas que con la de las Sierras Subandinas, Andes del Norte, Chaco, Patagonia, Mahuidas y Chile Central. El área de América del Norte y América Central aparece menos relacionada a Tandilia y Ventania en relación a las otras áreas. La evolución de las Asteraceae de Tandilia y Ventania y las áreas relacionadas ha sido probablemente afectada por los eventos geológicos de los períodos Terciario y Cuaternario. La discontinuidad actual en el patrón de distribución de las Asteraceae, restringidas en general a las zonas elevadas, es explicada principalmente por eventos vicariantes debidos a condiciones áridas.Tandilia and Ventania are the only systems ofmountain ranges situated in a grassy steppe or "pampas" in the political province of Buenos Aires in Argentina. Tandilia and Ventania

  9. Early Oscillation Detection for DC/DC Converter Fault Diagnosis

    Science.gov (United States)

    Wang, Bright L.

    2011-01-01

    The electrical power system of a spacecraft plays a very critical role for space mission success. Such a modern power system may contain numerous hybrid DC/DC converters both inside the power system electronics (PSE) units and onboard most of the flight electronics modules. One of the faulty conditions for DC/DC converter that poses serious threats to mission safety is the random occurrence of oscillation related to inherent instability characteristics of the DC/DC converters and design deficiency of the power systems. To ensure the highest reliability of the power system, oscillations in any form shall be promptly detected during part level testing, system integration tests, flight health monitoring, and on-board fault diagnosis. The popular gain/phase margin analysis method is capable of predicting stability levels of DC/DC converters, but it is limited only to verification of designs and to part-level testing on some of the models. This method has to inject noise signals into the control loop circuitry as required, thus, interrupts the DC/DC converter's normal operation and increases risks of degrading and damaging the flight unit. A novel technique to detect oscillations at early stage for flight hybrid DC/DC converters was developed.

  10. An Inventory of the Vascular Flora of Fort Greely, Interior Alaska

    Science.gov (United States)

    2001-02-01

    balsamifera Populus tremuloides Michx. Potamogeton alpinus Balbis Potamogeton filiformis Pers. *Potamogeton foliosus Raf. Potamogeton gramineus L...P. Mill. ssp. multifida (Pritz.) Zamels Pyrola asarifolia Michx. Pyrola chlorantha Sw. Pyrola grandiflora Radius *Pyrola minor L. Ranunculus gmelini...DC. ssp. gmelini 26 Ranunculus hyperboreus Rottb. Ranunculus lapponicus L. * Ranunculus nivalis L. Ranunculus reptans L. Ranunculus sceleratus L. ssp

  11. 75 FR 6160 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

    Science.gov (United States)

    2010-02-08

    ... Douglas Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40, DC-10-40F, MD-10-10F, MD-10-30F, MD-11, and MD-11F Airplanes AGENCY: Federal Aviation... airworthiness directive (AD) for certain Model DC-10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC- 10A...

  12. Control of improved full-bridge three-level DC/DC converter for wind turbines in a DC grid

    DEFF Research Database (Denmark)

    Deng, Fujin; Chen, Zhe

    2013-01-01

    transformer in the IFBTL dc/dc converter. A modulation strategy, including two operation modes, is proposed for the IFBTL dc/dc converter. Then, a voltage balancing control strategy is proposed for the IFBTL dc/dc converter. Furthermore, the control of the wind turbine based on the IFBTL dc/dc converter......This paper presents an improved full-bridge three-level (IFBTL) dc/dc converter for a wind turbine in a dc grid by inserting a passive filter into the dc/dc converter to improve the performance of the converter. The passive filter can effectively reduce the voltage stress of the medium frequency...... in a dc-grid system is presented. Finally, a small-scale IFBTL dc/dc converter prototype was built and tested in the laboratory, and the results verify the theoretical analysis....

  13. Reproductive biology in species of Bidens L. (Asteraceae Biologia reprodutiva em espécies de Bidens L. (Asteraceae

    Directory of Open Access Journals (Sweden)

    Maria Tereza Grombone-Guaratini

    2004-04-01

    Full Text Available Studies about reproductive biology of weed species can have implications on the establishment of controlling practices that minimize the effects of these weed populations on agricultural fields. The pollination biology of Bidens alba (L. DC., B. pilosa L., and Bidens subalternans DC., was studied at different sites and climatic seasons. Bidens pilosa and B. subalternans are widely distributed in agricultural areas, in disturbed habitats, and along road sides. Bidens alba occur only along the coast. The three species are self-compatible and non agamospermous. The composition of the pollinator community changes during the year and between sites. Hymenopterans and lepidopterans are the most frequent visitors to Bidens species in both areas studied. Although the species are self-compatible, the presence of pollinators may affect the levels of inbreeding. The attraction of insects by Bidens species may be benefical to agricultural crop and may also have important implications for conservation biology.Estudos de biologia reprodutiva de espécies invasoras podem ter implicações sobre o estabelecimento de práticas de controle que minimizem o efeito das populações destas espécies em áreas agrícolas. A biologia da polinização de Bidens alba (L. DC., B. pilosa L. e Bidens subalternans DC. foi estudada em diferentes locais e estações climáticas. Bidens pilosa e B. subalternans são espécies amplamente distribuídas em áreas agrícolas, em habitats perturbados e em margens de estradas. Bidens alba ocorre somente em regiões litorâneas. As três espécies são auto-compatíveis e não são agamospérmicas. A composição da comunidade de polinizadores apresenta diferenças durante o ano e entre locais. Himenópteros e lepidópteros são os visitantes mais freqüentes nas espécies de Bidens. Embora as espécies sejam auto compatíveis, a presença de polinizadores pode afetar os níveis de endocruzamento. A atração de insetos por esp

  14. Atlas palinológico de la Amazonia Colombiana II. Familia Asteraceae

    Directory of Open Access Journals (Sweden)

    Jiménez Bulla Luis Carlos

    1997-06-01

    Full Text Available We describe pollen from 26 genera of Asteraceae which belong to six tribes: Heliantheae (10, Eupatorieae (6, Vernonieae (6, Senecioneae (2, Mutisieae (1 and Inulineae (1. Tricolporate grains were dominant, but tetracolporate grains also appears. All grains are tectate and the most common sculpture type was echinate.Se describen 26 palinomorfos pertenecientes a los géneros más importantes en cuanto a número de especies de la familia Asteraceae y dentro de esta a las tribus Heliantheae (10, Eupatorieae (6, Vernonieae (6, Senecioneae (2, Mutisieae (1, Inulineae (1. Las aberturas son tricolporadas o tetracolporadas, los granos son tectados y el tipo de escultura que más se repite es la equinada.

  15. 75 FR 47242 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-14, DC-9-15, and DC-9-15F...

    Science.gov (United States)

    2010-08-05

    ... Corporation Model DC- 9-14, DC-9-15, and DC-9-15F Airplanes; and Model DC-9-20, DC-9-30, DC- 9-40, and DC-9-50... airworthiness directive (AD) that applies to certain Model DC-9-14 and DC-9-15 airplanes; and Model DC-9-20, DC-9-30, DC-9-40, and DC-9-50 series airplanes. The existing AD currently......

  16. Isolated Bidirectional DC-DC Converter for Hybrid Electric Vehicle Application

    Science.gov (United States)

    2006-06-13

    34Approved for public release: distribution is unlimited" Isolated Bidirectional DC-DC Converter for Hybrid Electric Vehicle Applications Sonya...requirements for DC-DC converters for electric and hybrid vehicles . This paper introduces a bidirectional, isolated DC-DC converter for medium power...the design and build of a medium power DC-DC converter . Key words: Power Converter , DC-DC, Hybrid Electric Vehicle , Battery, Galvanically Isolation

  17. Distribution of the most common weeds from fam. Asteraceae in Srem

    OpenAIRE

    Igić Ružica S.; Konstantinović Branko; Polić Dubravka; Anačkov Goran T.

    2002-01-01

    Weeds fall into a specific ecological group of plants and man should play the key role in controlling the process of their formation and the rate of their spreading. Damage caused by weeds is significant in both the agricultural and natural ecosystems. Therefore, special care should be paid to the current rate of their spreading, ensuring that the caused environmental changes do not become irreversible. The paper summarizes the locations in which the most common weed types of the Asteraceae f...

  18. The Anthelmintic Activity of Vernonia Amygdalina (Asteraceae) and Alstonia Boonei De Wild (Apocynaceae)

    OpenAIRE

    Ketor, E.C.; Annan, K.; Koffuor, G. A.; Danquah, C. A.

    2012-01-01

    Intestinal worms affect a host of individuals resulting in malnutrition, stunted growth, intellectual retardation and cognitive deficits. The aim of this study is to investigate the antihelminthic activity of Alstonia boonei De Wild (Apocynaceae) and Vernonia amygdalina (Asteraceae) using earth-worms (Lumbricus terretris). The worms were directly exposed to 50, 100, and 200 mg/ml of aque-ous and ethanolic bark extracts of Alstonia boonei and leaf extract of Vernonia amygdalina and piperazine ...

  19. Evaluation of Selected Ornamental Asteraceae as a Pollen Source for Urban Bees

    OpenAIRE

    Wróblewska Anna; Stawiarz Ernest; Masierowska Marzena

    2016-01-01

    Offering more floral resources for urban bees can be achieved by growing ornamental bee plants. The aim of the present study was to evaluate selected Asteraceae (Calendula officinalis ‘Persimmon Beauty’ and ‘Santana’, Centaurea macrocephala, Cosmos sulphureus, Dahlia pinnata, Tagetes patula, Tithonia rotundifolia, and Zinnia elegans) as pollen sources for pollinators. Under urban conditions in Lublin, SE Poland, the investigated plants flowered from late June to the end of October. The mass o...

  20. 75 FR 63040 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-30, DC...

    Science.gov (United States)

    2010-10-14

    ... Corporation Model DC- 10-10, DC-10-10F, DC-10-30, DC-10-30F (KDC-10), DC-10-40, and DC-10-40F Airplanes AGENCY..., Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590. FOR FURTHER INFORMATION CONTACT... (b) None. Applicability (c) This AD applies to McDonnell Douglas Corporation Model DC- 10-10,...

  1. Eupatorium capilifolium (Lam. Small ex Porter & Britton (Asteraceae: Eupatorieae, REKAMAN BARU UNTUK FLORA JAWA

    Directory of Open Access Journals (Sweden)

    Arifin Surya Dwipa Irsyam

    2016-12-01

    Full Text Available Abstrak Sebanyak 227 jenis tumbuhan Asteraceae terdapat di Pulau Jawa berdasarkan Flora of Java. Namun, suku Asteraceae di Pulau Jawa belum banyak ditinjau kembali sejak buku tersebut terbit 51 tahun yang lalu, sehingga memungkinkan adanya jenis-jenis tambahan yang belum terekam. Penelitian ini bertujuan untuk memberikan informasi adanya jenis tambahan yang terdapat di Pulau Jawa. Penelitian dilakukan menggunakan metode jelajah di Labuan (Banten, Bogor (Jawa Barat, Malang, dan Situbondo (Jawa Timur. Eupatorium capillifolium (Lam. Small ex Porter & Britton merupakan rekaman baru yang dapat melengkapi flora Jawa. Jenis tersebut dikelompokkan ke dalam puak Eupatorieae. Abstract There are 227 species of Asteraceae in Java Island recorded in the Flora of Java. However, only few review of this family for Java since Flora of Java has published 51 years ago. Some possibilities of unrecorded species may occur after this Flora of Java published. This research was conducted to provide information on additional species in Java Island. This research was carried out using exploration method in Labuan (Banten, Bogor (West Java, Malang and Situbondo (East Java. Eupatorium capillifolium (Lam. Small ex Porter & Britton is a new record for completing the flora of Java Island. This species belongs to Eupatorieae tribe.   

  2. A Metabolomic Approach to Target Compounds from the Asteraceae Family for Dual COX and LOX Inhibition

    Directory of Open Access Journals (Sweden)

    Daniela A. Chagas-Paula

    2015-07-01

    Full Text Available The application of metabolomics in phytochemical analysis is an innovative strategy for targeting active compounds from a complex plant extract. Species of the Asteraceae family are well-known to exhibit potent anti-inflammatory (AI activity. Dual inhibition of the enzymes COX-1 and 5-LOX is essential for the treatment of several inflammatory diseases, but there is not much investigation reported in the literature for natural products. In this study, 57 leaf extracts (EtOH-H2O 7:3, v/v from different genera and species of the Asteraceae family were tested against COX-1 and 5-LOX while HPLC-ESI-HRMS analysis of the extracts indicated high diversity in their chemical compositions. Using O2PLS-DA (R2 > 0.92; VIP > 1 and positive Y-correlation values, dual inhibition potential of low-abundance metabolites was determined. The O2PLS-DA results exhibited good validation values (cross-validation = Q2 > 0.7 and external validation = P2 > 0.6 with 0% of false positive predictions. The metabolomic approach determined biomarkers for the required biological activity and detected active compounds in the extracts displaying unique mechanisms of action. In addition, the PCA data also gave insights on the chemotaxonomy of the family Asteraceae across its diverse range of genera and tribes.

  3. Quantification of Sesquiterpene Lactones in Asteraceae Plant Extracts: Evaluation of their Allergenic Potential.

    Science.gov (United States)

    Salapovic, Helena; Geier, Johannes; Reznicek, Gottfried

    2013-01-01

    Sesquiterpene lactones (SLs), mainly those with an activated exocyclic methylene group, are important allergens in Asteraceae (Compositae) plants. As a screening tool, the Compositae mix, consisting of five Asteraceae plant extracts with allergenic potential (feverfew, tansy, arnica, yarrow, and German chamomile) is part of several national patch test baseline series. However, the SL content of the Compositae mix may vary due to the source material. Therefore, a simple spectrophotometric method for the quantitative measurement of SLs with the α-methylene-γ-butyrolactone moiety was developed, giving the percentage of allergenic compounds in plant extracts. The method has been validated and five Asteraceae extracts, namely feverfew (Tanacetum parthenium L.), tansy (Tanacetum vulgare L.), arnica (Arnica montana L.), yarrow (Achillea millefolium L.), and German chamomile (Chamomilla recutita L. Rauschert) that have been used in routine patch test screening were evaluated. A good correlation could be found between the results obtained using the proposed spectrophotometric method and the corresponding clinical results. Thus, the introduced method is a valuable tool for evaluating the allergenic potential and for the simple and efficient quality control of plant extracts with allergenic potential.

  4. The toxicity of Senecio inaequidens DC.

    Directory of Open Access Journals (Sweden)

    A.F.P. Dimande

    2007-06-01

    Full Text Available This study was designed to confirm the toxicity of a plant implicated in an outbreak of poisoning of stock in Frankfort, Free State Province, South Africa. Cows died acutely after being introduced into a camp, where an abundant, green shrublet was noted to be heavily grazed. This plant was subsequently identified as Senecio inaequidens DC. (Asteraceae by the South African National Biodiversity Institute (SANBI. Extraction and chemical analyses for pyrrolizidine alkaloids (PAs in Senecio inaequidens revealed the presence of 4 different compounds, namely retrorsine and senecionine (known to be hepatotoxic and 2 unidentified compounds. The average total PA (free base plus N-oxide concentration in plant parts of S. inaequidens collected at Frankfort during the outbreak was 0.81 %, compared with the total alkaloid content in the dried, milled S. inaequidens plant material, collected 7 weeks after the outbreak, of only 0.18 %. Male Sprague-Dawley rats (n=4, aged 8-9 weeks, were dosed per os. Each rat received a different dose of the crude Senecio inaequidens extract, ranging from 0.049 mg/g body weight (b.w. to 0.25 mg/g b.w. No clinical signs were observed in the rat receiving the lowest dose. Rats receiving higher doses showed depression, an unsteady gait, pilo-erection and jaundice, which was particularly noticeable in the ears. Clinical chemistry evaluation revealed an increase in the activities of ALP (except Rat 4, AST and GGT in all animals. Total serum bilirubin, creatinine and urea concentrations were also elevated. All rats had low serum globulin concentrations with an A/G ratio above 1.2. Post mortem examination of the rats revealed marked hepatic lesions. Histopathologically, these changes were characterised by necrosis (variable in extent of the centrilobular and midzonal hepatocytes (but sparing the portal hepatocytes, with extensive haemorrhage and congestion. Proliferation of the bile ducts, fibrosis and oedema were also present

  5. Asteraceae de interés en la Melisopalinogía: Bosque montano de las yungas (Jujuy - Argentina Asteraceae of melissopalynological interest: Yungas montane forest (Jujuy, Argentina

    Directory of Open Access Journals (Sweden)

    A. C. Sánchez

    2009-07-01

    Full Text Available Se presenta la descripción polínica de 17 especies de la familia Asteraceae, con una clave para su identificación. Estos materiales corresponden a la flora melífera del Bosque Montano en la Provincia Fitogeográfica de las Yungas en Jujuy. El estudio constituye el primer aporte para lograr la determinación polínica de las especies de esta familia en las mieles del área. Las especies descriptas son: Ageratum conyzoides, Baccharis salicifolia, Bidens pilosa, Elephantopus mollis, Eupatorium arnottianum Eupatorium bupleurifolium, Eupatorium leavigatum, Mikania micrantha, Parthenium hysteriophorus, Senecio cremeiflorus, Senecio rudbeckiifolius, Stevia potreriensis, Tagetes terniflora, Verbesina lilloi, Vernonia squamulosa, Viguiera mollis, Viguiera pazensis, todas ellas nativas.The descriptions of 17 pollen types of the Asteraceae family with a key for its identification are presented. These materials correspond to the mellipherus flora of the Bosque Montano in the Phytogeographycal Province of the Yungas in Jujuy. This study constitutes the first contribution to obtain the determination of the pollen types of this family in the honeys of the area. The species are described: Ageratum conyzoides, Baccharis salicifolia, Bidens pilosa, Elephantopus mollis, Eupatorium arnottianum Eupatorium bupleurifolium, Eupatorium leavigatum, Mikania micrantha, Parthenium hysteriophorus, Senecio cremeiflorus, Senecio rudbeckiifolius, Stevia potreriensis, Tagetes terniflora, Verbesina lilloi, Vernonia squamulosa, Viguiera mollis, Viguiera pazensis, all native.

  6. Nova nalazišta vrste Senecio inaequidens DC. u Hrvatskoj

    OpenAIRE

    Milović, Milenko; Pandža, Marija

    2014-01-01

    Senecio inaequidens DC. (Asteraceae) je neofit podrijetlom iz Južne Afrike koji je u Europu slučajno unesen uvozom vune krajem 19. i početkom 20. stoljeća. Od 70-tih godina prošlog stoljeća brzo se proširio većim dijelom srednje, zapadne i južne Europe. Nakon nedavno objavljenog nalaza u Hrvatskom zagorju (Sv. Križ Začretje), u ovom radu se navode dva nova nalazišta u Dalmaciji (Dicmo i Biograd). Zbog odgovarajuće klime i velikog broja pogodnih staništa, možemo očekivati udomaćenje i širenje ...

  7. In vitro propagation of Saussurea obvallata (DC.) Edgew.--an endangered ethnoreligious medicinal herb of Himalaya.

    Science.gov (United States)

    Joshi, M; Dhar, U

    2003-06-01

    This is the first report of a micropropagation protocol for Saussurea obvallata (DC.) Edgew. (Asteraceae), a rare, threatened and near-endemic medicinal herb of the Indian Himalayan region. Multiple shoots were formed from epicotyle explants on Murashige and Skoog (MS) medium supplemented with 1.0 microM kinetin and 0.25 microM alpha-naphthaleneacetic acid. A maximum of five shoots were obtained from one explant in a 75-day culture period. The effect of subsequent subcultures on shoot formation was also studied. After 100% in vitro rooting was obtained in half-strength MS supplemented with 2.5 microM indole-3-butyric acid, the plantlets were transferred to ex vitro conditions. Following a 15-day in vitro rooting period and 12 days of ex vitro acclimatization, 66.7% of the plantlets had established in the field. Application of this protocol has the potential to substantially reduce the pressure on natural populations.

  8. A new optimum topology switching dc-to-dc converter

    Science.gov (United States)

    Cuk, S.; Middlebrook, R. D.

    1977-01-01

    A novel switching dc-to-dc converter is presented, which has the same general conversion property (increase or decrease of the input dc voltage) as does the conventional buck-boost converter, and which offers through its new optimum topology higher efficiency, lower output voltage ripple, reduced EMI, smaller size and weight, and excellent dynamic response. One of its most significant advantages is that both input and output current are not pulsating but are continuous (essentially dc with small superimposed switching current ripple), thus resulting in a close approximation to the ideal physically nonrealizable dc-to-dc transformer. The converter retains the simplest possible structure with the minimum number of components which, when interconnected in its optimum topology, yield the maximum performance.

  9. Conception de convertisseurs DC/DC à base de MEMS

    OpenAIRE

    Ghandour, Sahar

    2011-01-01

    Current trends towards miniaturization of electronic circuits had led to the advent of System onChip containing different types of circuits indented to perform different functions. These sub-systemsrequire different supply voltages that are delivered from the SoC supply voltage using several DC/DCconverters. Currently, most of the electronic circuits of portable applications use conventional SMPS(switch mode power supply) DC/DC converters containing an inductor element to stock temporally the...

  10. A Novel FPSM Controller for DC-DC Switching Converters

    Institute of Scientific and Technical Information of China (English)

    Yong Feng; Shun-Ping Wang; Ping Luo; Quan-Ming Niu; Zhao-Ji Li

    2007-01-01

    This paper presents a novel fuzzy pulse skip modulation (FPSM) controller for switching direct current to direct current (DC-DC) converters based on fuzzy ratiocination modeling approach. Owing to the optimal consideration during the design and the nonlinear characteristics of the controller, improved dynamic responses of the FPSM controller can be achieved over conventional controllers. Compared with conventional proportion integral derivative (PID) control, FPSM control has 60% lower overshoot and 10% lower setting time under the same input voltage and output load change. The presented approach is general and can be applied to other types of DC-DC converters.

  11. High performance dc-dc conversion with voltage multipliers

    Science.gov (United States)

    Harrigill, W. T.; Myers, I. T.

    1974-01-01

    The voltage multipliers using capacitors and diodes first developed by Cockcroft and Walton in 1932 were reexamined in terms of state of the art fast switching transistors and diodes, and high energy density capacitors. Because of component improvements, the voltage multiplier, used without a transformer, now appears superior in weight to systems now in use for dc-dc conversion. An experimental 100-watt 1000-volt dc-dc converter operating at 100 kHz was built, with a component weight of about 1 kg/kW. Calculated and measured values of output voltage and efficiency agreed within experimental error.

  12. Improved DC Gun Insulator

    Energy Technology Data Exchange (ETDEWEB)

    M.L. Neubauer, K.B. Beard, R. Sah, C. Hernandez-Garcia, G. Neil

    2009-05-01

    Many user facilities such as synchrotron light sources and free electron lasers require accelerating structures that support electric fields of 10-100 MV/m, especially at the start of the accelerator chain where ceramic insulators are used for very high gradient DC guns. These insulators are difficult to manufacture, require long commissioning times, and have poor reliability, in part because energetic electrons bury themselves in the ceramic, creating a buildup of charge and causing eventual puncture. A novel ceramic manufacturing process is proposed. It will incorporate bulk resistivity in the region where it is needed to bleed off accumulated charge caused by highly energetic electrons. This process will be optimized to provide an appropriate gradient in bulk resistivity from the vacuum side to the air side of the HV standoff ceramic cylinder. A computer model will be used to determine the optimum cylinder dimensions and required resistivity gradient for an example RF gun application. A ceramic material example with resistivity gradient appropriate for use as a DC gun insulator will be fabricated by glazing using doping compounds and tested.

  13. Hysteretic Current Controlled Zvs Dc/Dc Converter For Automobile

    DEFF Research Database (Denmark)

    Cernat, M.; Scortarul, P.; Tanase, A.

    2007-01-01

    A novel bi-directional dc-dc converter with ZVS and interleaving for dual voltage systems in automobiles is presented. A variable frequency extended band hysteretic current control method is proposed. In comparison with classical fixed frequency current control PWM, the reverse polarity peak curr...

  14. Very High Frequency Half Bridge DC/DC Converter

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

    2014-01-01

    This paper presents the first, off chip, class DE (resonant half bridge) converter working in the Very High Frequency (VHF) range. The benefits of using half bridge circuits both in the inverter and rectifier part of a VHF resonant dc/dc converter are analyzed and design equations for all...

  15. A Plasma-Based DC-DC Electrical Transformer

    Science.gov (United States)

    Nebel, Richard; Finn, John

    2013-10-01

    Previous work has indicated that it may be possible to make DC-DC electrical transformers using plasmas. The mechanism is an MHD electromagnetic relaxation process induced by helical electrodes. This process is now being tested on the Bismark device at Tibbar Technologies.

  16. A Current-Fed Isolated Bidirectional DC-DC Converter

    DEFF Research Database (Denmark)

    Sun, Xiaofeng; Wu, Xiaoying; Shen, Yanfeng;

    2017-01-01

    This paper proposes a current-fed isolated bidirectional DC-DC converter (CF-IBDC) which has the advantages of wide input voltage range, low input current ripple, low conduction losses, and soft switching over the full operating range. Compared with conventional CF-IBDCs, the voltage spikes of th...

  17. SCM Handbooks for dc-to-dc Converters

    Science.gov (United States)

    Lee, F.; Mohmoud, M.; Yu, Y.

    1984-01-01

    Two documents aid in design of control modules for dc-to-dc converters. Features of SCM include: Adaptive stability, power component stress limiting, implementation of various control laws, unified design approach. Analysis and quidelines contained in handbooks enable engineer to design SCM circuit and confidently predict resulting overall performance.

  18. Efficient Design in a DC to DC Converter Unit

    Science.gov (United States)

    Bruemmer, Joel E.; Williams, Fitch R.; Schmitz, Gregory V.

    2002-01-01

    Space Flight hardware requires high power conversion efficiencies due to limited power availability and weight penalties of cooling systems. The International Space Station (ISS) Electric Power System (EPS) DC-DC Converter Unit (DDCU) power converter is no exception. This paper explores the design methods and tradeoffs that were utilized to accomplish high efficiency in the DDCU. An isolating DC to DC converter was selected for the ISS power system because of requirements for separate primary and secondary grounds and for a well-regulated secondary output voltage derived from a widely varying input voltage. A flyback-current-fed push-pull topology or improved Weinberg circuit was chosen for this converter because of its potential for high efficiency and reliability. To enhance efficiency, a non-dissipative snubber circuit for the very-low-Rds-on Field Effect Transistors (FETs) was utilized, redistributing the energy that could be wasted during the switching cycle of the power FETs. A unique, low-impedance connection system was utilized to improve contact resistance over a bolted connection. For improved consistency in performance and to lower internal wiring inductance and losses a planar bus system is employed. All of these choices contributed to the design of a 6.25 KW regulated dc to dc converter that is 95 percent efficient. The methodology used in the design of this DC to DC Converter Unit may be directly applicable to other systems that require a conservative approach to efficient power conversion and distribution.

  19. Dc-To-Dc Converter Uses Reverse Conduction Of MOSFET's

    Science.gov (United States)

    Gruber, Robert P.; Gott, Robert W.

    1991-01-01

    In modified high-power, phase-controlled, full-bridge, pulse-width-modulated dc-to-dc converters, switching devices power metal oxide/semiconductor field-effect transistors (MOSFET's). Decreases dissipation of power during switching by eliminating approximately 0.7-V forward voltage drop in anti-parallel diodes. Energy-conversion efficiency increased.

  20. An organic integrated capacitive DC-DC up-converter

    NARCIS (Netherlands)

    Marien, H.; Steyaert, M.; Steudel, S.; Vicca, P.; Smout, S.; Gelinck, G.H.; Heremans, P.L.

    2010-01-01

    In this paper a fully integrated organic DC-DC upconverter is presented in a pentacene p-type only technology. This 3-stage Dickson converter reaches a voltage conversion factor of 3 for a purely capacitive load and 2.5 for a 10 μA load current. The maximal output voltage goes up to 75 V and the Dic

  1. Sheppard-Taylor Isolated High Boost DC-DC Converter

    DEFF Research Database (Denmark)

    Chub, Andrii; Siwakoti, Yam Prasad; Vinnikov, Dmitri

    2017-01-01

    This paper presents a new galvanically isolated step-up dc-dc converter intended for low-power but high step-up applications. The proposed converter is capable of regulating output voltage within a wide range of the input voltage or load variations. In contrast to competitors, the converter can b...

  2. Early Oscillation Detection Technique for Hybrid DC/DC Converters

    Science.gov (United States)

    Wang, Bright L.

    2011-01-01

    Oscillation or instability is a situation that must be avoided for reliable hybrid DC/DC converters. A real-time electronics measurement technique was developed to detect catastrophic oscillations at early stages for hybrid DC/DC converters. It is capable of identifying low-level oscillation and determining the degree of the oscillation at a unique frequency for every individual model of the converters without disturbing their normal operations. This technique is specially developed for space-used hybrid DC/DC converters, but it is also suitable for most of commercial and military switching-mode power supplies. This is a weak-electronic-signal detection technique to detect hybrid DC/DC converter oscillation presented as a specific noise signal at power input pins. It is based on principles of feedback control loop oscillation and RF signal modulations, and is realized by using signal power spectral analysis. On the power spectrum, a channel power amplitude at characteristic frequency (CPcf) and a channel power amplitude at switching frequency (CPsw) are chosen as oscillation level indicators. If the converter is stable, the CPcf is a very small pulse and the CPsw is a larger, clear, single pulse. At early stage of oscillation, the CPcf increases to a certain level and the CPsw shows a small pair of sideband pulses around it. If the converter oscillates, the CPcf reaches to a higher level and the CPsw shows more high-level sideband pulses. A comprehensive stability index (CSI) is adopted as a quantitative measure to accurately assign a degree of stability to a specific DC/DC converter. The CSI is a ratio of normal and abnormal power spectral density, and can be calculated using specified and measured CPcf and CPsw data. The novel and unique feature of this technique is the use of power channel amplitudes at characteristic frequency and switching frequency to evaluate stability and identify oscillations at an early stage without interfering with a DC/DC converter s

  3. A DC Transformer

    Science.gov (United States)

    Youngquist, Robert C.; Ihlefeld, Curtis M.; Starr, Stanley O.

    2013-01-01

    A component level dc transformer is described in which no alternating currents or voltages are present. It operates by combining features of a homopolar motor and a homopolar generator, both de devices, such that the output voltage of a de power supply can be stepped up (or down) with a corresponding step down (or up) in current. The basic theory for this device is developed, performance predictions are made, and the results from a small prototype are presented. Based on demonstrated technology in the literature, this de transformer should be scalable to low megawatt levels, but it is more suited to high current than high voltage applications. Significant development would be required before it could achieve the kilovolt levels needed for de power transmission.

  4. Potencial antioxidante e antimicrobiano de espécies da família Asteraceae Antioxidant and antimicrobial potential of Asteraceae species

    Directory of Open Access Journals (Sweden)

    R.L Fabri

    2011-01-01

    Full Text Available Espécies da família Asteraceae são amplamente utilizadas na medicina popular para diversos fins terapêuticos. Neste contexto, este estudo teve por objetivo averiguar a atividade antimicrobiana e antioxidante in vitro de extratos metanólicos de plantas pertencentes a Asteraceae, a maioria comumente utilizada na medicina tradicional. A prospecção química dos extratos também foi realizada. A atividade antimicrobiana foi avaliada pelo método de susceptibilidade em microdiluição em caldo e a atividade antioxidante determinada pelo ensaio com o radical DPPH. O extrato da folha de Baccharis dracunculifolia apresentou significativa atividade antimicrobiana para Pseudomonas aeruginosa,Bacillus cereus e Cryptococcus neoformans (CIM = 0,005; 0,005 e 0,039 mg mL-1, respectivamente. Os extratos das folhas de Bidens segetum e Matricaria chamomilla foram seletivos para Shigella sonnei e P. aeruginosa (CIM = 0,005 e 0,078 mg mL-1, respectivamente. Já as folhas de Acanthospermun australe e Baccharis trimera apresentaram atividade significativa apenas para Candida albicans (CIM = 0,039 mg mL-1 enquanto as folhas de Taraxacum officinale foram ativos contra ambas leveduras com CIM 0,039 mg mL-1. Em relação à atividade antioxidante, os extratos das folhas de B. dracunculifolia, T. officinale e das inflorescências de B. segetum apresentaram significativa atividade com CI50 de 5, 5 e 4 µg mL-1, respectivamente. A prospecção química dos extratos identificou presença de compostos como flavonoides, terpenos e outros que podem ser responsáveis pelas atividades observadas.Asteraceae species have been largely used in folk medicine for several therapeutic purposes. Thus, the aim of this work was to investigate the in vitro antimicrobial and antioxidant activities of methanol extracts from plants belonging to the Asteraceae family, most of which are commonly used in traditional medicine. Chemical prospecting of extracts was also performed. The

  5. Germinação de sementes de Asteraceae nativas no Rio Grande do Sul, Brasil Germination of seeds of Asteraceae natives of Rio Grande do Sul, Brazil

    Directory of Open Access Journals (Sweden)

    Alfredo Gui Ferreira

    2001-08-01

    Full Text Available Aquênios (sementes recém coletados, de treze espécies nativas de Asteraceae comuns nos ambientes abertos da região sul do Brasil foram testados quanto à germinação em temperaturas alternadas ( 20/10; 25/15; 30/20; 35/25°C e sob temperaturas constantes ( 20; 25 e 30°C com ou sem luz. A temperatura ótima para germinação varia entre as espécies, sendo que as espécies Elephantopus mobilis; Eupatorium laevigatum; Mikania cordifolia; Senecio oxyphyllus; Trixis prastens germinam de forma semelhante em todas temperaturas testadas. Eclipta alba tem sua germinação promovida a 30°C. Tagetes minuta tem a germinação das sementes promovida a 20°C. Em Senecio heterotrichius; S. selloi; Stenachaenium campestre; Symphyopappus casarettoi e Vernonia nudiflora as sementes germinam igualmente a 20 ou 25°C.. A luz promoveu a germinação de todas espécies exceto para Stenachaenium campestre e Tagetes minuta, sendo esta última espécie fotoblástica negativa. Quanto ao tempo médio de germinação, as espécies podem ser divididas em ; rápidas- menos de 5 dias (Baccharis trimera; Eclipta alba; Elephantopus mollis; Stenachaenium campestre e Vernonia nudiflora; intermediárias: entre 5 e 10 dias ( Eupatorium laevigatum; Mikania cordifolia e Tagetes minuta ; lentas: mais de 10 dias (Senecio heterotrichius; S.oxyphyllus; S.selloi; Symphyopappus casarettoi e Trixis praestans.Os resultados mostram que a germinação de sementes de Asteraceas variam com a temperatura e o regime de luz; podendo prover uma base inicial para interpretação de efeitos sazonais sobre a germinação e estabelecimento a campo. Em adição, comentários sobre o substrato ágar ou areia são feitos.Achenes of thirteen native Asteraceae species common to the natural grassland or weeds of the southern region of Brazil were tested for germination over a range of alternating temperatures ( 20/10; 25/15; 30/20 and 35/25°C, and under constant temperatures ( 20; 25 and 30°C with

  6. DC Microgrids—Part II

    DEFF Research Database (Denmark)

    Dragicevic, Tomislav; Lu, Xiaonan; Quintero, Juan Carlos Vasquez

    2016-01-01

    distribution applications such as traction, telecom, vehicular and distributed power systems can be classified under DC MG framework and ongoing development and expansion of the field is largely influenced by concepts used over there. This paper aims firstly to shed light on the practical design aspects of DC...

  7. Modular Power System Configured with Standard Product Hybrid DC-DC Converters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — VPT proposes an innovative concept whereby complex, multiple-output, DC-DC converter systems can be configured through use of only 2 standard product hybrid DC-DC...

  8. Triple voltage dc-to-dc converter and method

    Science.gov (United States)

    Su, Gui-Jia

    2008-08-05

    A circuit and method of providing three dc voltage buses and transforming power between a low voltage dc converter and a high voltage dc converter, by coupling a primary dc power circuit and a secondary dc power circuit through an isolation transformer; providing the gating signals to power semiconductor switches in the primary and secondary circuits to control power flow between the primary and secondary circuits and by controlling a phase shift between the primary voltage and the secondary voltage. The primary dc power circuit and the secondary dc power circuit each further comprising at least two tank capacitances arranged in series as a tank leg, at least two resonant switching devices arranged in series with each other and arranged in parallel with the tank leg, and at least one voltage source arranged in parallel with the tank leg and the resonant switching devices, said resonant switching devices including power semiconductor switches that are operated by gating signals. Additional embodiments having a center-tapped battery on the low voltage side and a plurality of modules on both the low voltage side and the high voltage side are also disclosed for the purpose of reducing ripple current and for reducing the size of the components.

  9. New taxa of Cousinia Cass., Sect. Stenocephalae Bunge (Asteraceae from Iran

    Directory of Open Access Journals (Sweden)

    Farideh Attar

    2011-06-01

    Full Text Available Six new species of genus Cousinia, sect. Stenocephalae (Asteraceae including Cousinia ginuae, C. shahuensis from Kurdestan region, C. minuticapitata, C. touchalensis, C. kandavanensis from Tehran region and C. golestanica from Golestan region were described and illustrated. These species which are endemic to Iran are placed in accordance with some characters such as the number of flowers (up to 20, shape of head, decurrent leaves (short- or longly decurrent and their habitat. Comments are also presented about their habitats and geographic distribution as well.

  10. Complete chloroplast genomes from apomictic Taraxacum (Asteraceae): Identity and variation between three microspecies

    Science.gov (United States)

    Majeský, Ľuboš; Schwarzacher, Trude; Gornall, Richard; Heslop-Harrison, Pat

    2017-01-01

    Chloroplast DNA sequences show substantial variation between higher plant species, and less variation within species, so are typically excellent markers to investigate evolutionary, population and genetic relationships and phylogenies. We sequenced the plastomes of Taraxacum obtusifrons Markl. (O978); T. stridulum Trávniček ined. (S3); and T. amplum Markl. (A978), three apomictic triploid (2n = 3x = 24) dandelions from the T. officinale agg. We aimed to characterize the variation in plastomes, define relationships and correlations with the apomictic microspecies status, and refine placement of the microspecies in the evolutionary or phylogenetic context of the Asteraceae. The chloroplast genomes of accessions O978 and S3 were identical and 151,322 bp long (where the nuclear genes are known to show variation), while A978 was 151,349 bp long. All three genomes contained 135 unique genes, with an additional copy of the trnF-GGA gene in the LSC region and 20 duplicated genes in the IR region, along with short repeats, the typical major Inverted Repeats (IR1 and IR2, 24,431bp long), and Large and Small Single Copy regions (LSC 83,889bp and SSC 18,571bp in O978). Between the two Taraxacum plastomes types, we identified 28 SNPs. The distribution of polymorphisms suggests some parts of the Taraxacum plastome are evolving at a slower rate. There was a hemi-nested inversion in the LSC region that is common to Asteraceae, and an SSC inversion from ndhF to rps15 found only in some Asteraceae lineages. A comparative repeat analysis showed variation between Taraxacum and the phylogenetically close genus Lactuca, with many more direct repeats of 40bp or more in Lactuca (1% larger plastome than Taraxacum). When individual genes and non-coding regions were for Asteraceae phylogeny reconstruction, not all showed the same evolutionary scenario suggesting care is needed for interpretation of relationships if a limited number of markers are used. Studying genotypic diversity in

  11. A new polyacetylene from Vernonia scorpioides (Lam.) Pers. (Asteraceae) and its in vitro antitumoral activity

    Energy Technology Data Exchange (ETDEWEB)

    Buskuhl, Humberto; Freitas, Rilton A.; Biavatti, Maique W. [Universidade do Vale do Itajai, Itajai, SC (Brazil). Centro de Ciencias da Saude], e-mail: maique@ccs.ufsc.br; Monache, Franco Delle [Universita ' La Sapienza' , Rome (Italy). Dipt. di Chimica e Tecnologia delle Sostanze Biologicamente Attive; Barison, Andersson; Campos, Francinete R. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Centro Politecnico. Dept. de Quimica; Corilo, Yuri E.; Eberlin, Marcos N. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Quimica

    2009-07-01

    The dichloromethane fraction obtained from hydroalcoholic crude extract of leaves and flowers of Vernonia scorpioides (Asteraceae) was investigated, resulting in the isolation and structure elucidation of a new polyacetylene namely 5-octa-2,4,6-triynyl-furan-2(5H)-one. The structure of the isolated compound was determined based on IR, NMR (1D and 2D) and MS spectrometric data. The antitumor potential, including cytotoxicity to tumor cells and genotoxicity, was investigated. The results suggest that apoptotic cell death may have occurred, at least in part, via a caspase-dependent mechanism. (author)

  12. Complete chloroplast genomes from apomictic Taraxacum (Asteraceae): Identity and variation between three microspecies.

    Science.gov (United States)

    M Salih, Rubar Hussein; Majeský, Ľuboš; Schwarzacher, Trude; Gornall, Richard; Heslop-Harrison, Pat

    2017-01-01

    Chloroplast DNA sequences show substantial variation between higher plant species, and less variation within species, so are typically excellent markers to investigate evolutionary, population and genetic relationships and phylogenies. We sequenced the plastomes of Taraxacum obtusifrons Markl. (O978); T. stridulum Trávniček ined. (S3); and T. amplum Markl. (A978), three apomictic triploid (2n = 3x = 24) dandelions from the T. officinale agg. We aimed to characterize the variation in plastomes, define relationships and correlations with the apomictic microspecies status, and refine placement of the microspecies in the evolutionary or phylogenetic context of the Asteraceae. The chloroplast genomes of accessions O978 and S3 were identical and 151,322 bp long (where the nuclear genes are known to show variation), while A978 was 151,349 bp long. All three genomes contained 135 unique genes, with an additional copy of the trnF-GGA gene in the LSC region and 20 duplicated genes in the IR region, along with short repeats, the typical major Inverted Repeats (IR1 and IR2, 24,431bp long), and Large and Small Single Copy regions (LSC 83,889bp and SSC 18,571bp in O978). Between the two Taraxacum plastomes types, we identified 28 SNPs. The distribution of polymorphisms suggests some parts of the Taraxacum plastome are evolving at a slower rate. There was a hemi-nested inversion in the LSC region that is common to Asteraceae, and an SSC inversion from ndhF to rps15 found only in some Asteraceae lineages. A comparative repeat analysis showed variation between Taraxacum and the phylogenetically close genus Lactuca, with many more direct repeats of 40bp or more in Lactuca (1% larger plastome than Taraxacum). When individual genes and non-coding regions were for Asteraceae phylogeny reconstruction, not all showed the same evolutionary scenario suggesting care is needed for interpretation of relationships if a limited number of markers are used. Studying genotypic diversity in

  13. Toxicity of Thiophenes from Echinops transiliensis (Asteraceae) against Aedes aegypti (Diptera: Culicidae) Larvae

    Science.gov (United States)

    2014-01-01

    Toxicity of Thiophenes from Echinops transiliensis (Asteraceae) against Aedes aegypti (Diptera: Culicidae) Larvae by Hiroshi Nakano*a)b)c), Abbas...larvicides against Aedes aegypti . Structural differences among compounds 3, 5, and 8 consisted in differing AcO and OH groups attached to C(3’’) and C(4...mg/ml), 4 (LC50 , 17.95 mg/ml), 6 (LC50 , 18.55 mg/ml), and 7 (LC50 , 19.97 mg/ml). These data indicated that A. aegypti larvicidal activities of

  14. GaN Microwave DC-DC Converters

    Science.gov (United States)

    Ramos Franco, Ignacio

    Increasing the operating frequency of switching converters can have a direct impact in the miniaturization and integration of power converters. The size of energy-storage passive components and the difficulty to integrate them with the rest of the circuitry is a major challenge in the development of a fully integrated power supply on a chip. The work presented in this thesis attempts to address some of the difficulties encountered in the design of high-frequency converters by applying concepts and techniques usually used in the design of high-efficiency power amplifiers and high-efficiency rectifiers at microwave frequencies. The main focus is in the analysis, design, and characterization of dc-dc converters operating at microwave frequencies in the low gigahertz range. The concept of PA-rectifier duality, where a high-efficiency power amplifier operates as a high-efficiency rectifier is investigated through non-linear simulations and experimentally validated. Additionally, the concept of a self-synchronous rectifier, where a transistor rectifier operates synchronously without the need of a RF source or driver is demonstrated. A theoretical analysis of a class-E self-synchronous rectifier is presented and validated through non-linear simulations and experiments. Two GaN class-E2 dc-dc converters operating at a switching frequency of 1 and 1.2 GHz are demonstrated. The converters achieve 80 % and 75 % dc-dc efficiency respectively and are among the highest-frequency and highest-efficiency reported in the literature. The application of the concepts established in the analysis of a self-synchronous rectifier to a power amplifier culminated in the development of an oscillating, self-synchronous class-E 2 dc-dc converter. Finally, a proof-of-concept fully integrated GaN MMIC class-E 2 dc-dc converter switching at 4.6 GHz is demonstrated for the first time to the best of our knowledge. The 3.8 mm x 2.6 mm chip contains distributed inductors and does not require any

  15. Bi-Directional DC-DC Converter for PHEV Applications

    Energy Technology Data Exchange (ETDEWEB)

    Abas Goodarzi

    2011-01-31

    Plug-In Hybrid Electric Vehicles (PHEV) require high power density energy storage system (ESS) for hybrid operation and high energy density ESS for Electric Vehicle (EV) mode range. However, ESS technologies to maximize power density and energy density simultaneously are not commercially feasible. The use of bi-directional DC-DC converter allows use of multiple energy storage, and the flexible DC-link voltages can enhance the system efficiency and reduce component sizing. This will improve fuel consumption, increase the EV mode range, reduce the total weight, reduce battery initial and life cycle cost, and provide flexibility in system design.

  16. Transformerless DC-DC Converter Using Cockcroft-Walton Voltage Multiplier to Obtain High DC Voltage

    Directory of Open Access Journals (Sweden)

    Meghana G Naik,

    2014-11-01

    Full Text Available In the present scenario the use of transformer for high voltages in converter circuit reduces the overall operating efficiency due to leakage inductance and use of transformer also increases the operational cost. . Therefore the proposed system is implemented with transformer less DC-DC converter so as to obtain high DC voltage with the use of nine stage Cockcroft-Walton (CW voltage multiplier. The proposed converter operates in CCM (continuous conduction mode, so that the converter switch stress, the switching losses are reduced. The DC voltage at the input of the proposed model is low and is boosted up by boost inductor (Ls in DC-DC converter stage and performs inverter operation. The number of stages in CW-voltage multiplier circuit is applied with low input pulsating DC (AC Voltage voltage where it is getting converted to high DC output voltage. The proposed converter switches operates at two independent frequencies, modulating (fsm andalternating (fsc frequency. The fsm operates at higher frequency of the output while the fsc operates at lower frequency of the desired output voltage ripple and the output ripples can be adjusted by the switch Sc1 and Sc2. The regulation of the output voltage is achieved by controlling the Duty ratio.The simulation is carried over by the MATLABSIMULINK.

  17. An Efficient DC- DC Converter with Bidirectional Power Flow

    Directory of Open Access Journals (Sweden)

    N.RAJARAJESWARI

    2008-07-01

    Full Text Available This paper introduces a Bi-directional DC-DC converter with adaptive fuzzy logic controller. Bidirectional power flow is obtained by same power components and provides a simple, efficient, and galvanically isolated converter. In the presence of DC mains the converter operates as buck converter and charges the battery. When the DC mains fails, the converter operates as boost converter and the down stream converter is fed by the battery. The power switches are controlled by Pulse Width Modulation technique and the pulses are generated by the application of fuzzy logic with an adoption algorithm. The proposed converter is simulated using MATLAB and laboratory prototype was developed to validate the simulation results.

  18. Fuzzy Control of DC-DC Converters with Input Constraint

    Directory of Open Access Journals (Sweden)

    D. Saifia

    2012-01-01

    Full Text Available This paper proposes a method for designing fuzzy control of DC-DC converters under actuator saturation. Because linear control design methods do not take into account the nonlinearity of the system, a T-S fuzzy model and a controller design approach is used. The designed control not only handles the external disturbance but also the saturation of duty cycle. The input constraint is first transformed into a symmetric saturation which is represented by a polytopic model. Stabilization conditions for the state feedback system of DC-DC converters under actuator saturation are established using the Lyapunov approach. The proposed method has been compared and verified with a simulation example.

  19. General-purpose fuzzy controller for dc-dc converters

    Energy Technology Data Exchange (ETDEWEB)

    Mattavelli, P.; Rossetto, L.; Spiazzi, G.; Tenti, P. [Univ. of Padova (Italy)

    1997-01-01

    In this paper, a general-purpose fuzzy controller for dc-dc converters is investigated. Based on a qualitative description of the system to be controlled, fuzzy controllers are capable of good performances, even for those systems where linear control techniques fail, e.g., when a mathematical description is not available or is in the presence of wide parameter variations. The presented approach is general and can be applied to any dc-dc converter topologies. Controller implementation is relatively simple and can guarantee a small-signal response as fast and stable as other standard regulators and an improved large-signal response. Simulation results of Buck-Boost and Sepic converters show control potentialities.

  20. Step-Up DC-DC Power Converter

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a step-up DC-DC power converter which comprises a primary side circuit and a secondary side circuit coupled through a galvanic isolation barrier. The primary side circuit comprises a positive and a negative input terminal for receipt of an input voltage and an input...... being charged from the input voltage and discharged to the output capacitor through the galvanic isolation barrier in accordance with a switch control signal to produce the converter output voltage. The step-up DC-DC power converter comprises an electrical short-circuit connection across the galvanic...... capacitor coupled between the positive and negative input terminals and the secondary side circuit comprises an output capacitor chargeable to a converter output voltage between a first positive electrode and a second negative electrode. A switched energy storage network is configured for alternatingly...

  1. A Novel High Gain DC-DC Step up Converter

    Directory of Open Access Journals (Sweden)

    M. Al Mamun

    2016-07-01

    Full Text Available High gain dc-dc converters are widely used to maximize the energy harvest for renewable energy systems, for example, photovoltaic systems and fuel cell. Conventional boost converters usually operates at extreme duty cycle to obtain high voltage gain. Operation at extreme duty cycle leads to reverse recovery problem at the switches, high conduction loss, electromagnetic interference etc. This paper proposes a very high gain dc-dc step up converter operating at very low duty cycle (i.e. duty cycle <0.5. The additional advantage of the proposed converter is that a single control signal is used for the switches which reduces the operation complexity. The steady-state theoretical analysis described in this paper is finally verified by simulation results

  2. Decentralized Interleaving of Paralleled Dc-Dc Buck Converters: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Brian B [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rodriguez, Miguel [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-09-01

    We present a decentralized control strategy that yields switch interleaving among parallel connected dc-dc buck converters without communication. The proposed method is based on the digital implementation of the dynamics of a nonlinear oscillator circuit as the controller. Each controller is fully decentralized, i.e., it only requires the locally measured output current to synthesize the pulse width modulation (PWM) carrier waveform. By virtue of the intrinsic electrical coupling between converters, the nonlinear oscillator-based controllers converge to an interleaved state with uniform phase-spacing across PWM carriers. To the knowledge of the authors, this work represents the first fully decentralized strategy for switch interleaving of paralleled dc-dc buck converters.

  3. Active pre-filters for dc/dc Boost regulators

    Directory of Open Access Journals (Sweden)

    Carlos Andrés Ramos-Paja

    2014-07-01

    Full Text Available This paper proposes an active pre-filter to mitigate the current harmonics generated by classical dc/dc Boost regulators, which generate current ripples proportional to the duty cycle. Therefore, high output voltage conditions, i.e., high voltage conversion ratios, produce high current harmonics that must be filtered to avoid damage or source losses. Traditionally, these current components are filtered using electrolytic capacitors, which introduce reliability problems because of their high failure rate. The solution introduced in this paper instead uses a dc/dc converter based on the parallel connection of the Boost canonical cells to filter the current ripples generated by the Boost regulator, improving the system reliability. This solution provides the additional benefits of improving the overall efficiency and the voltage conversion ratio. Finally, the solution is validated with simulations and experimental results.

  4. A Feed-Forward Control Realizing Fast Response for Three-Branch Interleaved DC-DC Converter in DC Microgrid

    DEFF Research Database (Denmark)

    Wang, Haojie; Han, Minxiao; Yan, Wenli

    2016-01-01

    It is a common practice for storage batteries to be connected to DC microgrid buses through DC-DC converters for voltage support on islanded operation mode. A feed-forward control based dual-loop constant voltage PI control for three-branch interleaved DC-DC converters (TIDC) is proposed for stor......It is a common practice for storage batteries to be connected to DC microgrid buses through DC-DC converters for voltage support on islanded operation mode. A feed-forward control based dual-loop constant voltage PI control for three-branch interleaved DC-DC converters (TIDC) is proposed...... for storage batteries in DC microgrids. The working principle of TIDC is analyzed, and the factors influencing the response rate based on the dual-loop constant voltage control for TIDC are discussed, and then the method of feed-forward control for TIDC is studied to improve the response rate for load...

  5. DC-SIGN/DC-SIGNR基因多态性与病原微生物感染%Polymorphisms of DC-SIGN/DC-SIGNR and pathogen infection

    Institute of Scientific and Technical Information of China (English)

    许利军; 潘晨; 李勤光

    2010-01-01

    DC-SIGN和DC-SIGNR是两种表达于DC表面的蛋白,被认为是许多病原微生物的黏附受体,参与很多病原微生物的感染.DC-SIGN和DC-SIGNR(DC-SIGN/DC-SIGNR)的多态性或许影响病原微生物的感染过程和结果.此文对DC-SIGN/DC-SIGNR的结构功能以及与HIV、HCV感染、肺结核、登革热的关系进行了综述.%DC-SIGN and DC-SIGNR are two surface proteins on dendritic cells with complex stmction, and are regarded as attachment receptors of many pathogens, DC-SIGN/DC-SIGNR participate in pathogen infection.Polymorphisms of DC-SIGN/DC-SIGNR probably influence the procedure and outcome of pathogen infection. In this article, the structure and function of DC-SIGN/DC-SIGNR are discussed as well as the relation between the DC-SIGN/DC-SIGNR and pathogens such as HIV, HCV infection, pulmonary tuberculosis, dengue fever.

  6. DC injection into low voltage AC networks

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    This report summarises the results of a study investigating the impact of levels of injected DC current injections on a low voltage AC distribution network systems in order to recommend acceptable limits of DC from microgeneration. Relevant literature is reviewed, and the impact of DC levels in distribution transformers, transformer modelling, and instrumental transformers are discussed. The impact of DC in residual current devices (RCD) and in domestic electricity watt hour meters is examined along with DC enhanced corrosion, corrosion failure, and the measurement of DC current injection. Sources of DC injection outlined include DC from computer power supplies, network faults, geomagnetic phenomena, lighting circuits/dimmers, and embedded generators.

  7. DC-Compensated Current Transformer.

    Science.gov (United States)

    Ripka, Pavel; Draxler, Karel; Styblíková, Renata

    2016-01-20

    Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component.

  8. Modified Multiport Dc-Dc Converter Topology For Smart Grid

    Directory of Open Access Journals (Sweden)

    Dhamodharan Shanmugam

    2013-10-01

    Full Text Available The development of a Solid State Transformer (SST that incorporates a DC-DC multiport converter to integrate both photovoltaic (PV power generation and battery energy storage is presented in this dissertation. The DC-DC stage is based on a quad active-bridge (QAB converter which not only provides isolation for the load, but also for the PV and storage. The AC-DC stage is implemented with a pulse-widthmodulated (PWM single phase rectifier. A unified gyrator-based average model is developed for a general multi-active-bridge (MAB converter controlled through phase-shift modulation (PSM. Expressions to determine the power rating of the MAB ports are also derived. The developed gyrator-based average model is applied to the QAB converter for faster simulations of the proposed SST during the control design process as well for deriving the state-space representation of the plant. Both linear quadratic regulator (LQR and singleinput-single-output (SISO types of controllers are designed for the DC-DC stage. A novel technique that complements the SISO controller by taking into account the cross coupling characteristics of the QAB converter is also presented herein. Cascaded SISO controllers are designed for the AC-DC stage. The QAB demanded power is calculated at the QAB controls and then fed into the rectifier controls in order to minimize the effect of the interaction between the two SST stages. The dynamic performance of the designed control loops based on the proposed control strategies are verified through extensive simulation of the SST average and switching models.

  9. Emissions Tests Of Two Dc-To-Dc Converters

    Science.gov (United States)

    Mclyman, W. T.

    1992-01-01

    Report describes tests to characterize unwanted electric and magnetic fields, at frequencies up to few megahertz, radiated by two dc-to-dc converters, one 20-kHz square-wave converter; the other, a 33-kHz sine-wave converter. Part of effort to develop "quiet" power converter for use aboard spacecraft. Converter required to interfere minimally with delicate instruments measuring electric and magnetic fields.

  10. Hybrid battery with bi-directional DC/DC converter

    Directory of Open Access Journals (Sweden)

    DUDRIK Jaroslav

    2010-05-01

    Full Text Available Bi-directional buck-boost DC/DC converterfor hybrid battery is described in this paper. The firstpart of the paper is aimed at concept of hybrid battery;main advance compared to conventional accumulatoris explained there. Control circuit with UC3637 andpower circuit of the converter are described in thesecond part of the paper. Experimental results frommeasuring of converter are mentioned in the last part.

  11. Digital Control Technologies for Modular DC-DC Converters

    Science.gov (United States)

    Button, Robert M.; Kascak, Peter E.; Lebron-Velilla, Ramon

    2002-01-01

    Recent trends in aerospace Power Management and Distribution (PMAD) systems focus on using commercial off-the-shelf (COTS) components as standard building blocks. This move to more modular designs has been driven by a desire to reduce costs and development times, but is also due to the impressive power density and efficiency numbers achieved by today's commercial DC-DC converters. However, the PMAD designer quickly learns of the hidden "costs" of using COTS converters. The most significant cost is the required addition of external input filters to meet strict electromagnetic interference (MIAMI) requirements for space systems. In fact, the high power density numbers achieved by the commercial manufacturers are greatly due to the lack of necessary input filters included in the COTS module. The NASA Glenn Research Center is currently pursuing a digital control technology that addresses this problem with modular DC-DC converters. This paper presents the digital control technologies that have been developed to greatly reduce the input filter requirements for paralleled, modular DC-DC converters. Initial test result show that the input filter's inductor size was reduced by 75 percent, and the capacitor size was reduced by 94 percent while maintaining the same power quality specifications.

  12. Screening of Asteraceae (Compositae Plant Extracts for Larvicidal Activity against Aedes fluviatilis (Diptera: Culicidae

    Directory of Open Access Journals (Sweden)

    Macêdo Maria E

    1997-01-01

    Full Text Available Ethanol extracts of 83 plants species belonging to the Asteraceae (Compositae family, collected in the State of Minas Gerais, Brazil, were tested for larvicidal activity against the mosquito Aedes fluviatilis - Diptera: Culicidae. The extract from Tagetes minuta was the most active with a LC90 of 1.5 mg/l and LC50 of 1.0 mg/l. This plant has been the object of several studies by other groups and its active components have already been identified as thiophene derivatives, a class of compounds present in many Asteraceae species. The extract of Eclipta paniculata was also significantly active, with a LC90 of 17.2 mg/l and LC50 of 3.3 mg/l and no previous studies on its larvicidal activity or chemical composition could be found in the literature. Extracts of Achryrocline satureoides, Gnaphalium spicatum, Senecio brasiliensis, Trixis vauthieri, Tagetes patula and Vernonia ammophila were less active, killing more than 50% of the larvae only at the higher dose tested (100 mg/l.

  13. Early evolution of the angiosperm clade Asteraceae in the Cretaceous of Antarctica.

    Science.gov (United States)

    Barreda, Viviana D; Palazzesi, Luis; Tellería, Maria C; Olivero, Eduardo B; Raine, J Ian; Forest, Félix

    2015-09-01

    The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76-66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60-50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general.

  14. COROTIPOS PRELIMINARES DE PERÚ BASADOS EN LA DISTRIBUCIÓN DE LA FAMILIA ASTERACEAE

    Directory of Open Access Journals (Sweden)

    Berni Britto

    2014-01-01

    Full Text Available El presente estudio se basa en el concepto de categorías corológicas o corotipos para formular una nueva hipótesis de clasificación biogeográfica del Perú basado en la distribución de la familia Astera - ceae. La información recabada dio como resultado que existen 1669 especies de Asteraceae registradas en Perú (hasta el año 2008, distribuidas en 255 géneros. El territorio peruano se dividió en 218 Distritos de Reporte que representan a los 24 departamentos divididos en franjas de 500 m de altitud. La base de datos biogeográficos de Asteraceae se obtuvo cruzando los registros de distribución actualizados con los Distritos de Reporte, expresándose en una matriz de presencia-ausencia. El análisis de datos dio como resultado un total de 14 corotipos preliminares para el Perú: Abiseo, Amotape, Andino, Apurímac-Huan - cavelica, Chachapoyas-Huánuco, Huancabamba, Huascarán, Ica, Lima-Piura, Loreto-Ucayali, Manu, Pasco, Sandia y Tacna.

  15. Phylogeny of Barnadesioideae (Asteraceae) inferred from DNA sequence data and morphology.

    Science.gov (United States)

    Gruenstaeudl, Michael; Urtubey, Estrella; Jansen, Robert K; Samuel, Rosabelle; Barfuss, Michael H J; Stuessy, Tod F

    2009-06-01

    Subfamily Barnadesioideae (Asteraceae) consists of nine genera and 91 species endemic to South America. They include annual and perennial herbs, arching shrubs and trees up to 30m tall. Presumed sister to all other Asteraceae, its intergeneric relationships are key to understanding the early evolution of the family. Results of the only molecular study on the subfamily conflict with relationships inferred from morphology. We investigate inter- and intrageneric relationships in Barnadesioideae with novel DNA sequence data and morphological characters using parsimony, likelihood and Bayesian inference. All results verify Barnadesioideae as monophyletic and sister to the rest of the family. A basal split within the subfamily is recognized, with Chuquiraga, Doniophyton and Duseniella in one clade, and Arnaldoa, Barnadesia, Dasyphyllum, Fulcaldea, Huarpea and possibly Schlechtendalia in another. The largest genus, Dasyphyllum, is revealed as biphyletic with the two clades separating along subgeneric and geographic lines. Schlechtendalia, suggested as the earliest diverging lineage of the subfamily by morphological studies and parsimony analyses, is found in a more derived position under model-based inference methods. Competing phylogenetic hypotheses, both previous and present, are evaluated using likelihood-based tests. Evolutionary trends within Barnadesioideae are inferred: hummingbird pollination has developed convergently at least three times. An early vicariance in the subfamily's distribution is revealed. X=9 is supported as the ancestral base chromosome number for both Barnadesioideae and the family as a whole.

  16. Ribosomal DNA, heterochromatin, and correlation with genome size in diploid and polyploid North American endemic sagebrushes (Artemisia, Asteraceae)

    Science.gov (United States)

    Sonia Garcia; Teresa Garnatje; Jaume Pellicer; E. Durant McArthur; Sonja Siljak-Yakovlev; Joan Valles

    2009-01-01

    Subgenus Tridentatae (Artemisia, Asteraceae) can be considered a polyploid complex. Both polyploidy and hybridization have been documented in the Tridentatae. Fluorescent in situ hybridization (FISH) and fluorochrome banding were used to detect and analyze ribosomal DNA changes linked to polyploidization in this group by studying four diploidpolyploid species pairs. In...

  17. Phylogenetic relationships and generic delimitation in Inuleae subtribe Inulinae (Asteraceae) based on ITS and cpDNA sequence data

    DEFF Research Database (Denmark)

    Englund, Marcus; Pornpongrungrueng, Pimwadee; Gustafsson, Mats

    2009-01-01

    Phylogenetic relationships in Inuleae subtribe Inulinae (Asteraceae) were investigated. DNA sequence data from three chloroplast regions (ndhF, trnL-F and psbA-trnH) and the nuclear ribosomal internal transcribed spacer (ITS) region were analysed separately and in combination using parsimony...

  18. Hemijski sastav i antimikrobna aktivnost nekih sekundarnih metabolita biljaka Centaurea pannonica (Heuffel) Simonkai (Asteraceae) i Origanum scabrum Boiss. & Heldr. (Lamiaceae)

    OpenAIRE

    Milošević-Ifantis, Tanja S.

    2013-01-01

    Predmet doktorske disertacije je izolovanje i identifikacija sekundarnih metabolita iz ekstrakata nadzemnih delova biljaka Centaurea pannonica (Heuffel) Simonkai (Asteraceae) i Origanum scabrum Boiss. & Heldr. (Lamiacea), kao i ispitivanje obima njihove antimikrobne aktivnosti i hemotaksonomski značaj. Takođe, predmet ispitivanja je hemijski sastav etarskog ulja Centaurea pannonica i antimikrobna aktivnost. Primenom hromatografskih metoda izolovanja jedinjenja i spektroskopskih metod...

  19. The first description of the leaf-mining Nepticulidae (Lepidoptera) feeding on the South American plant genus Liabum, Asteraceae.

    Science.gov (United States)

    Stonis, Jonas R; Diškus, Arūnas; Remeikis, Andrius

    2015-11-13

    First Liabum Adans. (Asteraceae) feeding Nepticulidae are reported. Two new new species from the Andes (Ecuador) are described: Stigmella serpantina Diškus & Stonis, sp. nov. and S. pangorica Diškus & Stonis, sp. nov. The male genitalia of both species and the female genitalia, as well the leaf-mines of S. serpantina sp. nov. are illustrated.

  20. Linking DC together with TRSL

    DEFF Research Database (Denmark)

    Haxthausen, Anne Elisabeth; Yong, X.

    2000-01-01

    Duration Calculus (DC) is an interval-based real-time logic, which can be used in capturing and eliciting users' real-time requirements. The Timed RAISE Specification Language (TRSL) is an extension of the RAISE Specification Language with real-time features. This paper links DC and TRSL together...... approach for linking state-based real-time logics together with event-based, timed process algebra languages....

  1. DC superconducting fault current limiter

    Science.gov (United States)

    Tixador, P.; Villard, C.; Cointe, Y.

    2006-03-01

    There is a lack of satisfying solutions for fault currents using conventional technologies, especially in DC networks, where a superconducting fault current limiter could play a very important part. DC networks bring a lot of advantages when compared to traditional AC ones, in particular within the context of the liberalization of the electric market. Under normal operation in a DC network, the losses in the superconducting element are nearly zero and only a small, i.e. a low cost, refrigeration system is then required. The absence of zero crossing of a DC fault current favourably accelerates the normal zone propagation. The very high current slope at the time of the short circuit in a DC grid is another favourable parameter. The material used for the experiments is YBCO deposited on Al2O3 as well as YBCO coated conductors. The DC limitation experiments are compared to AC ones at different frequencies (50-2000 Hz). Careful attention is paid to the quench homogenization, which is one of the key issues for an SC FCL. The University of Geneva has proposed constrictions. We have investigated an operating temperature higher than 77 K. As for YBCO bulk, an operation closer to the critical temperature brings a highly improved homogeneity in the electric field development. The material can then absorb large energies without degradation. We present tests at various temperatures. These promising results are to be confirmed over long lengths.

  2. Simulation and Implementation of Quasi Resonant DC-DC Converter

    Directory of Open Access Journals (Sweden)

    N. Devarajan

    2012-01-01

    Full Text Available Problem statement: A half-bridge LLC resonant converter with a voltage doubler rectifier has a simple structure and its Zero-Voltage-Switching (ZVS capability is excellent from zero to full load condition. But conduction loss is more due to high circulating energy thus reducing the system efficiency. Moreover a variable frequency control method makes the control circuits more complicated than those using the Pulse Width Modulation (PWM control method. Thus, DC drive has lower efficiency when it operates on light loads. Approach: To improve the efficiency of the DC drive under light loads, a PWM-controlled quasi-resonant converter is proposed .It has simple control circuits and less conduction loss compared to a half-bridge LLC resonant converter under light load conditions. The proposed converter has a half-bridge LLC resonant converter along with an auxiliary circuit. The load regulation of the proposed converter can be achieved by an auxiliary circuit. Thus the proposed converter is expected to be suitable sustaining power module for the efficiency enhancement of DC drives. As the magnetizing inductance of the proposed converter is larger the circulating energy is considerably reduced under light load conditions. In this study the operational principle, design and modeling of QRC DC-DC converters for DC drives are presented. The PWM controlled quasi resonant converter is implemented using PIC microcontroller 16F184A. Results: The capacitor filter in the output is replaced by pi filter to produce DC with minimum ripple. The experimental results and simulation results are compared. This converter has the advantages like reduced number of switches, reduced transformer and filter size, reduced ripple, reduced switching losses, reduced switching stresses and increased power density. Conclusion: The experimental results closely agree with the simulation results.

  3. Mono-switch AC-DC/DC-DC converter for single-phase UPS%单相UPS的单开关AC-DC/DC-DC变换电路

    Institute of Scientific and Technical Information of China (English)

    李宋; 叶满园; 袁义生

    2011-01-01

    A mono-switch AC-DC/DC-DC converter used in single-phase UPS system is introduced,which consists of one power switch and six diodes. As both AC-DC rectifier and DC-DC booster,its operating modes and working principle are detailed. The single-cycle nonlinear control is adopted,which applies two low-speed PI regulators to control the voltage of two capacitors on DC link and a high-speed PI regulator to control the input current. Simulative results prove that,being simple and reliable,it outputs stable DC bus voltage with high input power factor and low THD.%介绍了一种应用在单相UPS系统中的新型单开关AC-DC/DC-DC变换电路,该电路由1个功率开关器件和6个二极管组成,能够实现AC/DC整流和DC/DC升压2种功能.在详细分析了该电路运行模式及工作原理的基础上,采用了单周期非线性控制理论对其进行控制,利于2个低速PI调节器对直流母线上的2个电容器电压进行控制,1个高速PI调节器对输入电流进行控制.仿真结果表明,该电路简单可靠,输入功率因数高,电流谐波失真小,可以获得稳定的正负直流母线电压.

  4. Caracterização morfoanatômica de Ageratum fastigiatum (Asteraceae Morpho-anatomical characterization of Ageratum fastigiatum (Asteraceae

    Directory of Open Access Journals (Sweden)

    Glauciemar Del-Vechio-Vieira

    2008-12-01

    Full Text Available Ageratum fastigiatum (Gardn. R. M. King et H. Rob. (Asteraceae, conhecido como "matapasto", é uma planta usada na medicina popular como cicatrizante e antimicrobiano. O objetivo deste trabalho foi realizar caracterização morfoanatômica da folha, dos ramos e da raiz de A. fastigiatum. Secções transversais e paradérmicas, coradas com safranina/azul de astra e azul de toluidina foram analisadas ao microscópio. As folhas são alternas ou fasciculadas; a inflorescência é constituída de capítulos; as flores com corola lilás; ausência de pápus. A raiz apresenta crescimento secundário na zona de ramificação com estruturas secretoras. O caule possui epiderme uniestratificada, estômatos, tricomas tectores simples e tricomas glandulares capitados. O pecíolo exibe contorno côncavo-convexo e a epiderme é unisseriada. A lâmina foliar é anfiestomática e o mesófilo dorsiventral. A epiderme possui células de contorno sinuoso e os estômatos são do tipo anomocítico. Os caracteres morfoanatômicos permitiram estabelecer parâmetros para identificação do A. fastigiatum.Ageratum fastigiatum (Gardn. R. M. King et H. Rob. (Asteraceae, known as "matapasto", is a plant used in the popular medicine as cicatrizant and antimicrobial. The aim of this work was to perform a morpho-anatomical characterization of the leaves, the stems and the roots from A. fastigiatum. Transversal and paradermic sections, stained with astra safranin/blue and toluidine blue were analyzed under a microscope. The leaves are alternate or fasciculate; the inflorescence is constituted of chapters; the flowers with lilac corolla; papus is absence. The root presents secondary growth in the ramification area with secretor structures. The stem possesses epidermis unistratified, stomata, simple non-glandular trichomes and capitates glandular trichomes. The petiole exhibits concave-convex outline and the epidermis is uniseriate. The blade leaf is hypostomatic; the mesophyll

  5. Pollen morphology of the genus Eremanthus Less. (Vernonieae, Asteraceae Morfologia polínica de espécies do gênero Eremanthus Less. (Vernonieae, Asteraceae

    Directory of Open Access Journals (Sweden)

    BenoÎt Loeuille

    2012-03-01

    Full Text Available In order to evaluate the significance of the pollen morphology for generic and infrageneric taxonomy of the genus Eremanthus (Vernonieae, Asteraceae, and to provide additional data for its phylogenetic reconstruction, the pollen of 20 of the 23 species of the genus was examined using light and scanning electron microscopy. Acetolysed pollen grains were measured, described, and illustrated using light microscopy, while non-acetolysed pollen grains were analyzed using scanning electron microscopy. Pollen grains of these species are isopolar, oblate-spheroidal in most of the species, more rarely prolate spheroidal or suboblate, subtriangular amb, tricolporate and subechinolophate. The variation among quantitative characters does not correlate with the macromorphological subdivision of the genus or with the generic or specific limits.Com a finalidade de avaliar a importância da morfologia polínica para a taxonomia de Eremanthus (Vernonieae, Asteraceae em nível genérico e infragenérico e fornecer dados adicionais para a sua reconstrução filogenética, os grãos de pólen de 20 das 23 espécies do gênero foram examinados usando a microscopia de luz e eletrônica de varredura. Os grãos de pólen foram acetolisados, medidos, descritos e ilustrados sob microscópio de luz. Para a análise em microscópio eletrônico de varredura foram utilizados grãos de pólen com e/ou sem tratamento químico. As espécies apresentaram grãos de pólen isopolares, oblato-esferoidais, na maioria dos táxons, mais raramente prolato-esferoidais ou suboblatos, âmbito subtriangular, tricolporados e subechinolofados. A variação entre os caracteres quantitativos não se correlacionam com a subdivisão macromorfológica do gênero nem com os limites genéricos ou específicos.

  6. DC Hierarchical Control System for Microgrid Applications

    OpenAIRE

    Lu, Xiaonan; Sun, Kai; Guerrero, Josep M.; Huang, Lipei

    2013-01-01

    In order to enhance the DC side performance of AC-DC hybrid microgrid,a DC hierarchical control system is proposed in this paper.To meet the requirement of DC load sharing between the parallel power interfaces,droop method is adopted.Meanwhile,DC voltage secondary control is employed to restore the deviation in the DC bus voltage.The hierarchical control system is composed of two levels.DC voltage and AC current controllers are achieved in the primary control level.

  7. A Comparison of the First Two Sequenced Chloroplast Genomes in Asteraceae: Lettuce and Sunflower

    Energy Technology Data Exchange (ETDEWEB)

    Timme, Ruth E.; Kuehl, Jennifer V.; Boore, Jeffrey L.; Jansen, Robert K.

    2006-01-20

    Asteraceae is the second largest family of plants, with over 20,000 species. For the past few decades, numerous phylogenetic studies have contributed to our understanding of the evolutionary relationships within this family, including comparisons of the fast evolving chloroplast gene, ndhF, rbcL, as well as non-coding DNA from the trnL intron plus the trnLtrnF intergenic spacer, matK, and, with lesser resolution, psbA-trnH. This culminated in a study by Panero and Funk in 2002 that used over 13,000 bp per taxon for the largest taxonomic revision of Asteraceae in over a hundred years. Still, some uncertainties remain, and it would be very useful to have more information on the relative rates of sequence evolution among various genes and on genome structure as a potential set of phylogenetic characters to help guide future phylogenetic structures. By way of contributing to this, we report the first two complete chloroplast genome sequences from members of the Asteraceae, those of Helianthus annuus and Lactuca sativa. These plants belong to two distantly related subfamilies, Asteroideae and Cichorioideae, respectively. In addition to these, there is only one other published chloroplast genome sequence for any plant within the larger group called Eusterids II, that of Panax ginseng (Araliaceae, 156,318 bps, AY582139). Early chloroplast genome mapping studies demonstrated that H. annuus and L. sativa share a 22 kb inversion relative to members of the subfamily Barnadesioideae. By comparison to outgroups, this inversion was shown to be derived, indicating that the Asteroideae and Cichorioideae are more closely related than either is to the Barnadesioideae. Later sequencing study found that taxa that share this 22 kb inversion also contain within this region a second, smaller, 3.3 kb inversion. These sequences also enable an analysis of patterns of shared repeats in the genomes at fine level and of RNA editing by comparison to available EST sequences. In addition, since

  8. Pulsewidth modulated DC-to-DC power conversion circuits, dynamics, and control designs

    CERN Document Server

    Choi, Byungcho

    2013-01-01

    This is the definitive reference for anyone involved in pulsewidth modulated DC-to-DC power conversion Pulsewidth Modulated DC-to-DC Power Conversion: Circuits, Dynamics, and Control Designs provides engineers, researchers, and students in the power electronics field with comprehensive and complete guidance to understanding pulsewidth modulated (PWM) DC-to-DC power converters. Presented in three parts, the book addresses the circuitry and operation of PWM DC-to-DC converters and their dynamic characteristics, along with in-depth discussions of control design of PWM DC-to

  9. DC-DC converter for discharging energy storage magnets

    Science.gov (United States)

    Eyssa, Yehia M.; Huang, Xianrui

    1994-07-01

    A new DC-DC converter to control the output power delivered from a magnetic energy storage magnet or an equivalent current source is discussed. The circuit consists of: (1) highly coupled transformer (air or iron core) with coupling coefficient better than 0.95; (2) low frequency mechanical or superconducting switches (0.1 - 10 Hz) or high frequency (10 - 1000 Hz) GTO switches depending on the application; and (3) small voltage source (capacitor or battery) to control the output voltage. Two examples illustrating the application of this circuit are discussed. They are a step up dc current converter for use in uninterruptible power supplies and a step down one for use in discharging large current storage coil into a small current load. The efficiency expected to exceed 90%.

  10. Antibacterial, antifungal and cytotoxic activities of eight Asteraceae and two Rubiaceae plants from colombian biodiversity Atividades antibactariana, antifúngica e citotóxica de oito plantas Asteraceae e duas Rubiaceae da biodiversidade colombiana

    Directory of Open Access Journals (Sweden)

    Jaime Niño

    2006-12-01

    Full Text Available Thirty crude extracts of eight plants belonging to Asteraceae and two to Rubiaceae families collected at different places from the Regional Natural Park Ucumarí (RNPU, Colombia, were tested for their antibacterial activity against two Gram-positive and two Gram-negative bacteria and three fungi. Both the antibacterial and the antimycotic activities were tested by the agar well diffusion method. The cytotoxic activity on the same plant extracts was determined through the brine shrimp lethality bioassay. The extracts from the Asteraceae family were more bioactive against Bacillus subtilis and Staphylococcus aureus. The extracts of both families studied were bioactive against the fungi Candida albicans and Fusarium solani. In addition, the extracts of Asteraceae species displayed the greatest cytotoxic activities. However, the most important specie in this research was Gonzalagunia rosea Standl (Rubiaceae because of the strong and moderate activities of the methanol and dichloromethane extracts against C. albicans and F. solani, respectively; as well as the strong cytotoxic activity of the methanol extract. None of these ten plants has previously been reported for their biological activities.Trinta extratos crus de oito plantas da família Asteraceae e a duas plantas da família Rubiaceae, coletadas em diferentes lugares do Parque Natural Regional Ucumarí (PNRU, Colombia, foram avaliadas quanto à atividade contra duas bactérias Gram-positivas, duas Gram-negativas e três fungos. As atividades antibacteriana e antimicótica foram determinadas pelo método de difusão em agar. A atividade citotóxica dos mesmos extratos foi determinada através do bioensaio de Artemia salina. Os extratos da família Asteraceae foram os mais bioativos contra Bacillus subtilis e Staphylococcus aureus. Os extratos de ambas famílias estudadas foram bioativos contra os fungos Candida albicans e Fusarium solani. Os extratos da família Asteraceae exibiram maior

  11. Pulse-width modulated DC-DC power converters

    CERN Document Server

    Kazimierczuk, Marian K

    2008-01-01

    This book studies switch-mode power supplies (SMPS) in great detail. This type of converter changes an unregulated DC voltage into a high-frequency pulse-width modulated (PWM) voltage controlled by varying the duty cycle, then changes the PWM AC voltage to a regulated DC voltage at a high efficiency by rectification and filtering. Used to supply electronic circuits, this converter saves energy and space in the overall system. With concept-orientated explanations, this book offers state-of-the-art SMPS technology and promotes an understanding of the principle operations of PWM converters,

  12. Radiated electromagnetic emissions of DC-DC converters

    Energy Technology Data Exchange (ETDEWEB)

    Feld, L; Jussen, R; Karpinski, W; Klein, K; Sammet, J; Wlochal, M, E-mail: sammet@cern.ch [Physikalisches Institut IB, RWTH Aachen University, Aachen (Germany)

    2010-12-15

    For the CMS tracker at SLHC a new powering scheme is considered to be mandatory to allow the detector to provide at least the same performance as today at the LHC. The baseline solution of CMS foresees the use of DC-DC converters to provide larger currents with smaller losses. An important component of most converters are inductors which, however, tend to radiate the switching noise generated by the converter. The emissions of different inductors have been measured and simulated, the coil design has been optimized and noise susceptibility measurements, with present CMS hardware, have been performed. This article summarizes the results.

  13. Radiated electromagnetic emissions of DC-DC converters

    CERN Document Server

    Sammet, Jan Domenik

    2010-01-01

    A new powering scheme is considered to be mandatory for the CMS tracker at SLHC. The baseline solution of CMS foresees the use of DC-DC converters, allowing to provide larger currents while reducing losses. An important component of most converters are inductors, which, however, tend to radiate the switching noise generated by the converter. The radiated emissions of several converters have been measured and simulated. In addition noise susceptibility measurements with radiated noise and present CMS hardware have been performed. A summary of the results will be presented.

  14. Low dose failures of hardened DC-DC power converters

    Science.gov (United States)

    Lehman, J.; Yui, C.; Rax, B. G.; Miyahira, T. F.; Weideman, M.; Schrick, P.; Swift, G. M.; Johnston, A. H.

    2002-01-01

    Box-level total dose testing of the FOG (Fiber Optic Gyro) by IXSEA at ESA's GammabeamFacility were abruptly terminated at 8krad (Si) due to catastrophic failure (complete shutdown). This was unexpected because all components within the gyro were supposedly radiation tolerant. Further testing showed that the components responsible for the failure were two DC-DC converters, manufactured by Interpoint, that stopped regulating shortly before shutdown. This paper summarizes diagnostic test results for the converters to determine the underlying cause of the unexpected failure at low levels of radiation.

  15. Power flow analysis for DC voltage droop controlled DC microgrids

    DEFF Research Database (Denmark)

    Li, Chendan; Chaudhary, Sanjay; Dragicevic, Tomislav

    2014-01-01

    This paper proposes a new algorithm for power flow analysis in droop controlled DC microgrids. By considering the droop control in the power flow analysis for the DC microgrid, when compared with traditional methods, more accurate analysis results can be obtained. The algorithm verification...... is carried out by comparing the calculation results with detailed time domain simulation results. With the droop parameters as variables in the power flow analysis, their effects on power sharing and secondary voltage regulation can now be analytically studied, and specialized optimization in the upper level...... control can also be made accordingly. Case studies on power sharing and secondary voltage regulation are carried out using proposed power flow analysis....

  16. Caffeoyl-D-Glucaric Acid Derivatives in the Genus Gnaphalium (Asteraceae: Gnaphalieae

    Directory of Open Access Journals (Sweden)

    Serhat Sezai Cicek

    2012-03-01

    Full Text Available A chemosystematic survey was carried out to specify whether leontopodic acid and leontopodic acid B, two unique caffeoyl-D-glucaric acid derivatives, recently identified in the emblematic alpine edelweiss (Leontopodium alpinum Cass. are also found in members of the genus Gnaphalium from the Alps. Gnaphalium is closely related to Leontopodium and both genera are assigned to the Gnaphaliinae subtribe (Asteraceae, Gnaphalieae. In all investigated Gnaphalium species, G. hoppeanum W.D.J.Koch, G. norvergicum Gunnerus, G. supinum L., G. sylvaticum L., and G. uliginosum L., both leontopodic acid and leontopodic acid B were detected. Moreover, a number of related compounds were detected by HPLC/MS and their assumed structures are discussed. The chemosystematic data reported here are of interest to explore new sources for the biologically active compounds leontopodic acid and leontopodic acid B and they also hint to the occurrence of novel caffeoyl-D-glucaric acid derivatives in Gnaphalium not detected in Leontopodium, yet.

  17. Taxonomic value of histochemical features of the style in early lineages of Asteraceae

    Directory of Open Access Journals (Sweden)

    Marcelo Paulo Hernández

    2015-12-01

    Full Text Available In this paper we examine lipophilic substances, tannins, proteins, reducing carbohydrates, starch, and oxalate salts in early lineages of Asteraceae to test if they are a useful complement to classification studies. Styles of mature flowers of 44 species were processed according to plant histochemical techniques and observed by means of a light microscope. Lipophilic compounds were always present in the cuticle and cell walls, and in some species were located inside the cells. Proteins were located in the style cell walls and cell interior of most of the analyzed species. No tannins were found. In general, there is a correlation in the presence of reducing sugars and proteins. Starch granules and oxalate salts were found in the style parenchyma of a few species. Cytoplasmic content of lipophilic compounds, proteins, and reducing sugars predominates in Barnadesioideae and Nassauvieae (Mutisioideae, and histochemical similarities were found among members of Gochnatioideae

  18. Synopsis of Plazia Ruiz & Pav. (Onoserideae, Asteraceae), including a new species from northern Peru.

    Science.gov (United States)

    Dillon, Michael O; Luebert, Federico

    2014-01-01

    A synopsis of Plazia Ruiz & Pav. (Onoserideae, Asteraceae) is presented, including the description of a new species, Plazia robinsonii M.O.Dillon & Sagást., from a locality c. 20 kms west of Huamachuco, Department of La Libertad in northern Peru. It most closely resembles Plazia conferta Ruiz & Pav., a narrow endemic from central Peru some 450 km to the south; however, the latter species has larger leaves and smaller capitula. Plazia is a small genus of four species confined to the Andean Cordillera of Peru, Bolivia, Chile, and Argentina. A distribution map of the four species, an illustration of the new species, a photograph of the holotype, and a key to species are provided.

  19. Antifungal activity of essential oils from leaves and flowers of Inula viscosa (Asteraceae) by Apulian region.

    Science.gov (United States)

    Cafarchia, C; De Laurentis, N; Milillo, M A; Losacco, V; Puccini, V

    2002-12-01

    Some essential oils from several plants (Artemisia verlotorum, Lavandula augustifolia, Ocimum gratissimum) have proved to have acaricidal, antifungal and antibacterial activity. Inula viscosa Ait. (Asteraceae), a plant growing spontaneously in the Mediterranean area, is currently used by popular medicine for its therapeutic effects. Flavonoids, azulenes, sesquiterpenes, and essential oils have been isolated and identified from its leaves. This paper reports the results of the composition and antifungal activity in vitro against dermatophytes and Candida spp. of the four essential oils obtained by steam distillation of the leaves, flowers, whole plant and whole plants without flower extracts of I. viscosa. All the extracts proved to have a significant antifungal activity against dermatophytes even at low concentrations (0.01 mg/ml). The leaf extracts exhibited the greatest antifungal efficacy. The high concentration of the sesquiterpene (carboxyeudesmadiene), occurring in the leaf extracts, may explain its greater antifungal activity.

  20. Othonna sonchifolia L. is an earlier name for Senecio cymbalarifolius L. (Asteraceae: Senecioneae

    Directory of Open Access Journals (Sweden)

    Luvo Magoswana

    2017-02-01

    Full Text Available Background: Ongoing systematic studies in the African flora necessitate periodic nomenclatural adjustments and corrections.Objectives: To effect requisite nomenclatural changes.Method: Relevant literature was surveyed and type material located and examined.Results: A nomenclatural correction is necessary in Othonna L. and Senecio L. (Asteraceae.Conclusions: Othonna sonchifolia L. is recognised as the earliest name for Senecio cymbalarifolius (L. Less. and the new combination Senecio sonchifolius (L. J.C. Manning & Magoswana is provided for the species. Othonna cymbalarifolia is lectotypified and Senecio hastifolius (L. Less. is reinstated from synonymy as a species distinct from S. sonchifolius.

  1. Prenanthes violaefolia Decne. (Asteraceae)-a new report from Kashmir Himalaya, India

    Institute of Scientific and Technical Information of China (English)

    Parvaiz Ahmad Lone; Ajay Kumar Bhardwaj; Kunwar Wajahat Shah

    2015-01-01

    Objective:To enumerate the diversity of important medicinal plants used traditionally by the local populace in biodiversity rich and temperate Himalayan ranges of Bandipora district, Jammu and Kashmir, India. Methods:Methods used to explore the plants with medicinal value and to record associated ethnomedicinal knowledge included semi-structured interviews, focus group discussions and walk-in-the-woods with local knowledgeable persons, traditional practitioners called“Bhoeris”and tribals (Gujjars and Bakkerwals). Results:During plant exploration in this floristically rich Himalayan region, a very interesting and less-known species of the genus Prenanthes L., (Asteraceae) was recorded. On examination, the species was identified as Prenanthes violaefolia Decne., which represents a first report from Kashmir Himalaya, India. Conclusions: Prenanthes violaefolia could serve as an important source of new potent compounds provided that it is subjected to thorough phytochemical and pharmacological investigations.

  2. Prenanthes violaefolia Decne.(Asteraceae)-a new report from Kashmir Himalaya, India

    Institute of Scientific and Technical Information of China (English)

    Parvaiz; Ahmad; Lone; Ajay; Kumar; Bhardwaj; Kunwar; Wajahat; Shah

    2015-01-01

    Objective: To enumerate the diversity of important medicinal plants used traditionally by the local populace in biodiversity rich and temperate Himalayan ranges of Bandipora district, Jammu and Kashmir, India. Methods: Methods used to explore the plants with medicinal value and to record associated ethnomedicinal knowledge included semi-structured interviews, focus group discussions and walk-in-the-woods with local knowledgeable persons, traditional practitioners called "Bhoeris" and tribals(Gujjars and Bakkerwals). Results: During plant exploration in this floristically rich Himalayan region, a very interesting and less-known species of the genus Prenanthes L.,(Asteraceae) was recorded. On examination, the species was identified as Prenanthes violaefolia Decne., which represents a first report from Kashmir Himalaya, India. Conclusions: Prenanthes violaefolia could serve as an important source of new potent compounds provided that it is subjected to thorough phytochemical and pharmacological investigations.

  3. Assessment of In vitro Sun Protection Factor of Calendula Officinalis L. (Asteraceae) Essential Oil Formulation.

    Science.gov (United States)

    Mishra, Ak; Mishra, A; Chattopadhyay, P

    2012-01-01

    The present study was undertaken to study the sunscreen activity of herbal formulation. There is no evidence of the sun protection factor (SPF) studies on essential oil of Calendula flowers (Calendula officinalis L., Asteraceae). The study investigates the in vitro SPF by ultraviolet specrtophotometry method of Calendula flower oil in a cream formulation. Calendula oil was isolated by Clavenger's apparatus, compositions were identified by GC-MS and the cream of calendula flower oil was prepared by homogenization method followed by evaluation for physical parameters. The sun protection factor of cream was evaluated by in vitro method employing UV-visible spectrophotometer (Shimazdu-1600). The SPF of Calendula oil in cream formulation exhibited good activity (SPF = 14.84 ± 0.16). Finding of this study suggested that calendula oil cream can be used to protect the skin from UV radiations in form of sunscreen cream and to maintain the natural pigmentation of the skin.

  4. Three new caespitose species of Senecio (Asteraceae, Senecioneae) from South Peru.

    Science.gov (United States)

    Tubée, Daniel B Montesinos

    2014-01-01

    Three new species of the genus Senecio (Asteraceae, Senecioneae) belonging to Senecio ser. Suffruticosi subser. Caespitosi were discovered in the tributaries of the upper Tambo River, Moquegua Department, South Peru. Descriptions, diagnoses and discussions about their distribution, a table with the morphological similarities with other species of Senecio, a distribution map, conservation status assessments, and a key to the caespitose Peruvian species of Senecio subser. Caespitosi are provided. The new species are Senecio moqueguensis Montesinos, sp. nov. (Critically Endangered) which most closely resembles Senecio pucapampaensis Beltrán, Senecio sykorae Montesinos, sp. nov. (Critically Endangered) which most closely resembles Senecio gamolepis Cabrera, and Senecio tassaensis Montesinos, sp. nov. (Critically Endangered) which most closely resembles Senecio moqueguensis Montesinos.

  5. Three new caespitose species of Senecio (Asteraceae, Senecioneae from South Peru

    Directory of Open Access Journals (Sweden)

    Daniel Montesinos Tubée

    2014-06-01

    Full Text Available Three new species of the genus Senecio (Asteraceae, Senecioneae belonging to S. ser. Suffruticosi subser. Caespitosi were discovered in the tributaries of the upper Tambo River, Moquegua Department, South Peru. Descriptions, diagnoses and discussions about their distribution, a table with the morphological similarities with other species of Senecio, a distribution map, conservation status assessments, and a key to the caespitose Peruvian species of S. subser. Caespitosi are provided. The new species are Senecio moqueguensis Montesinos, sp. nov. (Critically Endangered which most closely resembles Senecio pucapampaensis Beltrán, Senecio sykorae Montesinos, sp. nov. (Critically Endangered which most closely resembles Senecio gamolepis Cabrera, and Senecio tassaensis Montesinos, sp. nov. (Critically Endangered which most closely resembles Senecio moqueguensis Montesinos.

  6. Bidens meyeri (Asteraceae, Coreopsideae: a new critically endangered species from Rapa, Austral Islands

    Directory of Open Access Journals (Sweden)

    Vicki Funk

    2014-10-01

    Full Text Available Bidens meyeri (Asteraceae/Compositae is described and illustrated from Rapa, Austral Islands, (French Polynesia. This new species is presumed to be most closely related to Bidens saint-johniana from nearby Marotiri Island. Bidens meyeri may be distinguished from B. saint-johniana based on the length of the peduncle (3 cm versus 10 cm, apex of the inner involucral bracts (glabrous vs. puberulent, smaller leaves (2.0–2.3 cm vs. 5–6 cm, and the general smaller size of the new species. Known from less than 50 individuals and restricted to one remote location, Bidens meyeri falls into the IUCN Critically Endangered (CR category. The new species is named in honor of Dr. Jean-Yves Meyer, Délégation à la Recherche, Polynésie Française,

  7. Bidensmeyeri (Asteraceae, Coreopsideae): a new critically endangered species from Rapa, Austral Islands.

    Science.gov (United States)

    Funk, Vicki A; Wood, Kenneth R

    2014-01-01

    Bidensmeyeri (Asteraceae/Compositae) is described and illustrated from Rapa, Austral Islands, (French Polynesia). This new species is presumed to be most closely related to Bidenssaint-johniana from nearby Marotiri Island. Bidensmeyeri may be distinguished from Bidenssaint-johniana based on the length of the peduncle (3 cm versus 10 cm), apex of the inner involucral bracts (glabrous vs. puberulent), smaller leaves (2.0-2.3 cm vs. 5-6 cm), and the general smaller size of the new species. Known from less than 50 individuals and restricted to one remote location, Bidensmeyeri falls into the IUCN Critically Endangered (CR) category. The new species is named in honor of Dr. Jean-Yves Meyer, Délégation à la Recherche, Polynésie Française.

  8. ISOLATION AND ANALYTICAL CHARACTERIZATION OF STEVIOSIDE FROM LEAVES OF STEVIA REBAUDIANA BERT; (ASTERACEAE

    Directory of Open Access Journals (Sweden)

    Inamake M.R.

    2010-12-01

    Full Text Available Stevioside a natural non caloric sweetener isolated from the leaves of the plant Stevia rebaudiana Bertoni (Asteraceae or compositae. It has been widely used in many countries, including Japan, Korea, China, Brazil and Paraguay, either as a substitute for sucrose in beverages and foods or as a household sweetening agent isolated from the dried leaves of Stevia. In the present work attempt was made to isolate stevioside from the dried leaves of Stevia in its purest form. Isolated stevioside was purified, analyzed & characterized by using various chromatographic & analytical methods including TLC, UV, FTIR, NMR and HPLC methods. The Rf value for TLC was 0.32, λmax of UV spectra was obtained at 333 nm and HPLC showed the sharp peak with 1.958 min retention time. The isolated stevioside was also compared with standard stevioside with all analytical methods.

  9. Chemical constituents of Pseudobrickellia brasiliensis leaves(Spreng. R.M. King & H. Rob. (Asteraceae

    Directory of Open Access Journals (Sweden)

    M.L.L. DE AMORIM

    Full Text Available ABSTRACT Pseudobrickelliabrasiliensisis aspecies endemic toBrazil, popularlyknown as “arnica”/ “arnica-do-campo”/ “arnica-do-mato” and used for itsanalgesicand anti-inflammatoryproperties. The objective of this research was thephytochemical studyof the essential oilandhexaneandethyl acetateextracts of the leaves of this species. The essential oilwasextracted byhydrodistillation using a Clevengerapparatusand was analyzed byGC/MS, 25components were identified, with a predominance ofmonoterpenes. The extractswere subjected toclassicalchromatographyand the fractionswere analyzed byGC/MS, 1D 1H-NMR, 13C-NMR and 13C-NMR-DEPT 135.α-amyrin, α-amyrin acetate, β-amyrin, β-amyrin acetate, lupeol, lupeolacetate, pseudotaraxasterol andtaraxasterol (triterpenes, andkaurenoicacid (diterpene were identified.Theseterpenesarechemo-taxonomicallyrelated to theEupatorieaetribe(Asteraceae and may be responsible for the anti-inflammatory activity attributed to the plant.

  10. Switching coordination of distributed dc-dc converters for highly efficient photovoltaic power plants

    Science.gov (United States)

    Agamy, Mohammed; Elasser, Ahmed; Sabate, Juan Antonio; Galbraith, Anthony William; Harfman Todorovic, Maja

    2014-09-09

    A distributed photovoltaic (PV) power plant includes a plurality of distributed dc-dc converters. The dc-dc converters are configured to switch in coordination with one another such that at least one dc-dc converter transfers power to a common dc-bus based upon the total system power available from one or more corresponding strings of PV modules. Due to the coordinated switching of the dc-dc converters, each dc-dc converter transferring power to the common dc-bus continues to operate within its optimal efficiency range as well as to optimize the maximum power point tracking in order to increase the energy yield of the PV power plant.

  11. Optimization of control sequences for DC-DC-converters; Optimierung der Stellgroessenfolge eines DC-DC-Wandler

    Energy Technology Data Exchange (ETDEWEB)

    Kroeger, Claus [Hochschule Aalen (Germany). Wirtschaftsingenieurwesen

    2009-07-01

    DC-DC-Converters are used in power electronics to adapt different voltage levels of electrical sources and sinks with respect of high efficiency. To minimize electrical losses these power electronic converters always work with switching power semiconductors. This switching principle of the converter is causing a control constraint which limits the achievable performance for the voltage control drastically. This paper presents an optimization for the control sequence in a high dynamic converter control which is based on the dead-beat control design. Thus the non-avoidable control constraint will not be violated. (orig.)

  12. An Integrated Multifunctional Bidirectional AC/DC and DC/DC Converter for Electric Vehicles Applications

    Directory of Open Access Journals (Sweden)

    Liwen Pan

    2016-06-01

    Full Text Available This paper presents an on-board vehicular battery charger that integrates bidirectional AC/DC converter and DC/DC converter to achieve high power density for application in electric vehicles (EVs. The integrated charger is able to transfer electrical energy between the battery pack and the electric traction system and to function as an AC/DC battery charger. The integrated charger topology is presented and the design of passive components is discussed. The control schemes are developed for motor drive system and battery-charging system with a power pulsation reduction circuit. Simulation results in MATLAB/Simulink and experiments on a 30-kW motor drive and 3.3-kW AC/DC charging prototype validate the performance of the proposed technology. In addition, power losses, efficiency comparison and thermal stress for the integrated charger are illustrated. The results of the analyses show the validity of the advanced integrated charger for electric vehicles.

  13. Quasi Y-Source Boost DC-DC Converter

    DEFF Research Database (Denmark)

    Siwakoti, Yam P.; Blaabjerg, Frede; Loh, Poh Chiang

    2015-01-01

    A new topology called “quasi-Y-source impedance network” is presented in this paper. It inherits all the advantages of the original Y-source network. In addition, the new topology draws continuous current from the source which is required for many renewable sources. It also has dc-current-blockin...

  14. Anatomia e histoquímica dos órgãos vegetativos de Siegesbeckia orientalis (Asteraceae Anatomy and histochemistry of the vegetative organs of Siegesbeckia orientalis (Asteraceae

    Directory of Open Access Journals (Sweden)

    D.B. Aguilera

    2004-12-01

    Full Text Available Descreveu-se a anatomia dos órgãos vegetativos de S. orientalis, em estrutura primária, enfatizando a caracterização e histoquímica de suas estruturas secretoras. Folhas, caules e raízes foram fixados em FAA50 e em sulfato ferroso e estocados em etanol 70%. Cortes transversais e longitudinais foram submetidos ao azul-de-toluidina pH 4,0, ao vermelho-de-rutênio, à reação de PAS, ao reativo Xylidine Ponceau, ao Sudan Black B e ao reativo Dragendorff. Anatomicamente, os órgãos vegetativos de S. orientalis são semelhantes aos caracteres descritos para Asteraceae. As raízes laterais são triarcas e o caule, um eustelo. Ductos estão ausentes na raiz e presentes no caule e na folha. Estas estruturas são de pequeno diâmetro, sendo delimitadas por quatro a cinco células epiteliais. No caule, os ductos estavam presentes no córtex, próximos à endoderme e na medula; nas folhas, associados aos feixes vasculares, tanto para o lado do xilema quanto para o do floema. As folhas são dorsiventrais e anfiestomáticas. Três tipos de estruturas secretoras foram observados: ductos, hidatódios e tricomas glandulares. Os testes histoquímicos aplicados demonstraram a presença de compostos fenólicos e alcalóides nos ductos e, nos tricomas, de compostos lipofílicos e fenólicos. Esses resultados indicam a complexidade da secreção produzida pelas estruturas secretoras na espécie.The anatomy of the vegetative organs of S. orientalis in primary structure was described, emphasizing the characterization and histochemistry of its secretory structures. Leaves, stems and roots were fixed in FAA50 and ferrous sulphate and stored in 70% ethanol. Cross and longitudinal sections were submitted to toluidine blue pH 4.0, ruthenium red, PAS reaction, Ponceau Xylidine reactive, Sudan Black B and Dragendorff reactive. Anatomically, S. orientalis vegetative organs are similar to the characters described for the Asteraceae. The lateral roots are triarches and

  15. Experiments with a DC Motor

    Science.gov (United States)

    Kraftmakher, Yaakov

    2010-01-01

    Experiments with an electric motor provide good opportunity to demonstrate some basic laws of electricity and magnetism. The aim of the experiments with a low-power dc motor is to show how the motor approaches its steady rotation and how its torque, mechanical power and efficiency depend on the rotation velocity. The tight relationship between the…

  16. WOOD ANATOMY OF TWO SPECIES OF THE GENUS Heterothalamus Lessing (ASTERACEAE FROM RIO GRANDE DO SUL (BRAZIL

    Directory of Open Access Journals (Sweden)

    Anabela Silveira de Oliveira

    2010-08-01

    Full Text Available The present work describes the wood anatomy of Heterothalamus alienus and Heterothalamus rupestris (Astereae - Asteraceae, as part of the secondary xylem study in the named genus. For the two species it was recorded some features usually mentioned in the literature for the Asteraceae, as typically small vessels, grouped in a dendritic pattern, the presence of only simple perforation plates and of paratracheal parenchyma. Heterothalamus alienus shows spiral thickenings in the wood vessels and storied vasicentric axial parenchyma. Heterothalamus rupestris differs itself by the absence of spiral thickenings in wood vessels and by no storied axial parenchyma, in paratracheal vasicentric to unilateral patterns. Photomicrographs, quantitative data of anatomical features and a comparison between the two  species of wood are also provided.

  17. 75 FR 62331 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-14, DC-9-15, and DC-9-15F...

    Science.gov (United States)

    2010-10-08

    ... Directives; McDonnell Douglas Corporation Model DC- 9-14, DC-9-15, and DC-9-15F Airplanes; and DC-9-20, DC-9-30, DC-9-40, and DC-9-50 Series Airplanes AGENCY: Federal Aviation Administration (FAA), DOT. ACTION... Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590. Hand Delivery: Deliver to...

  18. 76 FR 39251 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

    Science.gov (United States)

    2011-07-06

    ... Model DC-9-81 (MD- 81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 Airplanes AGENCY... Jersey Avenue, SE., Washington, DC 20590. FOR FURTHER INFORMATION CONTACT: Roger Durbin, Aerospace.... Applicability (c) This AD applies to all The Boeing Company Model DC-9-81 (MD- 81), DC-9-82 (MD-82), DC-9-83...

  19. 76 FR 53346 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

    Science.gov (United States)

    2011-08-26

    ... Model DC-9-81 (MD- 81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 Airplanes AGENCY... Jersey Avenue, SE., Washington, DC 20590. Hand Delivery: Deliver to Mail address above between 9 a.m. and...) This AD applies to The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83),...

  20. 76 FR 1993 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

    Science.gov (United States)

    2011-01-12

    ... Model DC-9-81 (MD- 81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 Airplanes AGENCY... Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590. FOR FURTHER INFORMATION.... Applicability (c) This AD applies to The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83...

  1. 76 FR 41651 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

    Science.gov (United States)

    2011-07-15

    ... Model DC-9-81 (MD- 81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 Airplanes AGENCY... Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590. FOR FURTHER INFORMATION...) This AD applies to The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83),...

  2. 75 FR 68686 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-14, DC-9-15, and DC-9-15F...

    Science.gov (United States)

    2010-11-09

    ...; AD 2010-23-10] RIN 2120-AA64 Airworthiness Directives; McDonnell Douglas Corporation Model DC- 9-14, DC-9-15, and DC-9-15F Airplanes; and Model DC-9-20, DC-9-30, DC- 9-40, and DC-9-50 Series Airplanes... Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590. FOR FURTHER...

  3. DC motor operation controlled from a DC/DC power converter in pulse mode with low duty cycle

    OpenAIRE

    Stefanov, Goce; Kukuseva, Maja; Citkuseva Dimitrovska, Biljana

    2016-01-01

    In this paper pulse mode of operation of DC motor controlled by DC/DC power converter is analyzed. DC motor operation with time intervals in which the motor operates without output load is of interest. In this mode it is possible the motor to restore energy. Also, in the paper are represented calculations for the amount of the restored energy in the pulse mode operation of the motor for different duty cycles.

  4. Antipsychotic and sedative effects of the leaf extract of Crassocephalum bauchiense (Hutch.) Milne-Redh (Asteraceae) in rodents.

    OpenAIRE

    Sotoing Taïwe, Germain; Ngo Bum, Elisabeth; Talla, Emmanuel; Dawe, Amadou; Okomolo Moto, Fleur Clarisse; Temkou Ngoupaye, Gwladys; Sidiki, Neteydji; Dabole, Bernard; Djomeni Dzeufiet, Paul Désiré; Dimo, Théophile; De Waard, Michel

    2012-01-01

    International audience; ETHNOPHARMACOLOGICAL RELEVANCE: Crassocephalum bauchiense (Hutch.) Milne-Redh (Asteraceae) has been used as a medicine for the treatment of epilepsy, insomnia, dementia and psychotic disorders in Cameroonian traditional medicine. AIM OF THE STUDY: This study was designed to examine whether the aqueous extract and the alkaloid fraction prepared from the leaves of Crassocephalum bauchiense possess antipsychotic and sedative properties in rodents. MATERIALS AND METHODS: T...

  5. DC to DC power converters and methods of controlling the same

    Science.gov (United States)

    Steigerwald, Robert Louis; Elasser, Ahmed; Sabate, Juan Antonio; Todorovic, Maja Harfman; Agamy, Mohammed

    2012-12-11

    A power generation system configured to provide direct current (DC) power to a DC link is described. The system includes a first power generation unit configured to output DC power. The system also includes a first DC to DC converter comprising an input section and an output section. The output section of the first DC to DC converter is coupled in series with the first power generation unit. The first DC to DC converter is configured to process a first portion of the DC power output by the first power generation unit and to provide an unprocessed second portion of the DC power output of the first power generation unit to the output section.

  6. Speed Control of DC Motor using AC/AC/DC Converter Based on Intelligent Techniques

    Directory of Open Access Journals (Sweden)

    Rakan Kh Antar

    2013-05-01

    Full Text Available    This paper describes the application of ac/ac/dc and ac/dc converters to control the speed of a separately excited DC motor. Artificial neural network and PI controller are trained to select the desired values of firing angles for triggering thyristors of the ac/ac/dc and ac/dc bridge converters in order to control the speed of the dc motor at a desired value with constant and different load torques in order to obtain the best speed response. Simulation results show that the rising time for ac/dc and ac/ac/dc converters at 250rpm are reduced about 79% and 89% respectively, while delay time it reduced about 69% and 64% respectively. Therefore, speed response of the dc motor is more efficient for closed loop system compared with open loop also the response of ac/ac/dc converter is better than ac/dc converter.

  7. Biological Activities of Asteraceae (Achillea millefolium and Calendula officinalis) and Lamiaceae (Melissa officinalis and Origanum majorana) Plant Extracts.

    Science.gov (United States)

    García-Risco, Mónica R; Mouhid, Lamia; Salas-Pérez, Lilia; López-Padilla, Alexis; Santoyo, Susana; Jaime, Laura; Ramírez de Molina, Ana; Reglero, Guillermo; Fornari, Tiziana

    2017-03-01

    Asteraceae (Achillea millefolium and Calendula officinalis) and Lamiaceae (Melissa officinalis and Origanum majorana) extracts were obtained by applying two sequential extraction processes: supercritical fluid extraction with carbon dioxide, followed by ultrasonic assisted extraction using green solvents (ethanol and ethanol:water 50:50). The extracts were analyzed in terms of the total content of phenolic compounds and the content of flavonoids; the volatile oil composition of supercritical extracts was analyzed by gas chromatography and the antioxidant capacity and cell toxicity was determined. Lamiaceae plant extracts presented higher content of phenolics (and flavonoids) than Asteraceae extracts. Regardless of the species studied, the supercritical extracts presented the lowest antioxidant activity and the ethanol:water extracts offered the largest, following the order Origanum majorana > Melissa officinalis ≈ Achillea millefolium > Calendula officinalis. However, concerning the effect on cell toxicity, Asteraceae (especially Achillea millefolium) supercritical extracts were significantly more efficient despite being the less active as an antioxidant agent. These results indicate that the effect on cell viability is not related to the antioxidant activity of the extracts.

  8. Evolutionary Co-Option of Floral Meristem Identity Genes for Patterning of the Flower-Like Asteraceae Inflorescence.

    Science.gov (United States)

    Zhao, Yafei; Zhang, Teng; Broholm, Suvi K; Tähtiharju, Sari; Mouhu, Katriina; Albert, Victor A; Teeri, Teemu H; Elomaa, Paula

    2016-09-01

    The evolutionary success of Asteraceae, the largest family of flowering plants, has been attributed to the unique inflorescence architecture of the family, which superficially resembles an individual flower. Here, we show that Asteraceae inflorescences (flower heads, or capitula) resemble solitary flowers not only morphologically but also at the molecular level. By conducting functional analyses for orthologs of the flower meristem identity genes LEAFY (LFY) and UNUSUAL FLORAL ORGANS (UFO) in Gerbera hybrida, we show that GhUFO is the master regulator of flower meristem identity, while GhLFY has evolved a novel, homeotic function during the evolution of head-like inflorescences. Resembling LFY expression in a single flower meristem, uniform expression of GhLFY in the inflorescence meristem defines the capitulum as a determinate structure that can assume floral fate upon ectopic GhUFO expression. We also show that GhLFY uniquely regulates the ontogeny of outer, expanded ray flowers but not inner, compact disc flowers, indicating that the distinction of different flower types in Asteraceae is connected with their independent evolutionary origins from separate branching systems. © 2016 American Society of Plant Biologists. All rights reserved.

  9. Parasitoid Wasps in Flower Heads of Asteraceae in the Brazilian Cerrado: Taxonomical Composition and Determinants of Diversity.

    Science.gov (United States)

    Nascimento, A R; Almeida-Neto, M; Almeida, A M; Fonseca, C R; Lewinsohn, T M; Penteado-Dias, A M

    2014-08-01

    This study provides the first survey of the parasitoid fauna reared in flower heads of Asteraceae in the Brazilian cerrado. We investigated the relative importance of herbivore richness and plant species commonness to differences in parasitoid species richness among the plant species. A total of 15,372 specimens from 192 morphospecies belonging to 103 genera of Hymenoptera were reared from the flower heads of 74 Asteraceae species. Chalcidoidea and Ichneumonoidea were the most common superfamilies, with Eulophidae and Braconidae as the main families of parasitoid wasps. Singletons and doubletons accounted for 45% of total parasitoid species richness. The number of parasitoid species per plant species ranged from 1 to 67, and the variation in parasitoid species richness among plants was mainly explained by the number of sites in which the plants were recorded. This study shows that there is a highly diversified fauna of Hymenoptera parasitoids associated with flower heads of Asteraceae in the Brazilian cerrado. Our findings suggest that the accumulation of parasitoid species on plants is mainly determined by the regional commonness of plant species rather than the number of herbivore species associated with the plants.

  10. Dilation and Curettage (D&C)

    Science.gov (United States)

    ... For Patients About ACOG Dilation and Curettage (D&C) Home For Patients Search FAQs Dilation and Curettage ( ... February 2016 PDF Format Dilation and Curettage (D&C) Special Procedures What is dilation and curettage (D& ...

  11. Dilation and Curettage (D&C)

    Science.gov (United States)

    ... For Patients About ACOG Dilation and Curettage (D&C) Home For Patients Search FAQs Dilation and Curettage ( ... February 2016 PDF Format Dilation and Curettage (D&C) Special Procedures What is dilation and curettage (D& ...

  12. Optimization of DC-DC Converters via Geometric Programming

    Directory of Open Access Journals (Sweden)

    U. Ribes-Mallada

    2011-01-01

    Full Text Available The paper presents a new methodology for optimizing the design of DC-DC converters. The magnitudes that we take into account are efficiency, ripples, bandwidth, and RHP zero placement. We apply a geometric programming approach, because the variables are positives and the constraints can be expressed in a posynomial form. This approach has all the advantages of convex optimization. We apply the proposed methodology to a boost converter. The paper also describes the optimum designs of a buck converter and a synchronous buck converter, and the method can be easily extended to other converters. The last example allows us to compare the efficiency and bandwidth between these optimal-designed topologies.

  13. RESONANT STEP-DOWN DC-DC POWER CONVERTERS

    DEFF Research Database (Denmark)

    2015-01-01

    charged from the input voltage and discharged to the output capacitor through the galvanic isolation barrier by a semiconductor switch arrangement in accordance with a switch control signal to produce the converter output voltage. The resonant step-down DC-DC power converter comprises an electrical short...... of the primary side circuit thereby establishing in both the first and second cases a series coupling of the output capacitor and the input capacitor. A load connection is established, in the first case, between the first positive electrode of the output capacitor and the positive input terminal or......-circuit connection across the galvanic isolation barrier connecting, in a first case, the second negative electrode of the output capacitor to the positive input terminal of the primary side circuit or, in a second case, connecting the second positive electrode of the output capacitor to the negative input terminal...

  14. DC/DC converter with improved rectification for higher efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Maisel, Peter; Saliternig, Martin [Continental AG, Nuernberg (Germany)

    2010-07-01

    High-power dc-dc converters are an important element of the electrical system of electric vehicles and hybrid electric vehicles. These complex modular components provide the link between the high-voltage level used for the powertrain and the low-voltage bus for the lighting system, engine management and auxiliary needs in the vehicle. The essential requirements for all converters are high efficiency, compact size, lightweight and reliability. A very popular method to increase the efficiency is the synchronous rectification. Parasitic inductances in the commutation circuit and reverse recovery effects can produce a ringing with voltage overshoots at the diodes and the transistors. These spikes can cause higher average power dissipation in the seminconductors and higher EMI (electromagnetic interference).

  15. Study of nonlinear phenomena in switching DC/DC converters

    Science.gov (United States)

    Iu, Herbert Ho-Ching

    This thesis studies some nonlinear phenomena such as bifurcation and chaos in DC/DC switching converters. Five phases of investigations are described. The first phase reviews the existing tools for analyzing nonlinear systems that are helpful to the investigation of nonlinear phenomena in power electronic circuits. Some of these existing tools are employed to study the nonlinear behaviour of power electronic circuits in the subsequent phases. The second phase focuses on the analysis of bifurcation behaviour of parallel-connected DC/DC converters under a master-slave current sharing scheme. An iterative discrete-time map and its Jacobian are established to predict the onset of period-doubling or Neimark-Sacker bifurcation. Both parallel-connected buck converters and boost converters are studied. The third phase studies an autonomous free-running Cuk converter under a hysteretic current-mode control. Hopf bifurcation is observed, for the first time, in this kind of autonomous power electronic circuits. The method of state-space averaging is employed to predict the occurrence of such bifurcation. Extensive simulations and experiments confirm the predicted results. A typical bifurcation sequence from stable fixed points to chaos, via limit cycles and quasiperiodic orbits, is demonstrated. The fourth phase investigates the possibility of synchronization of two chaotic autonomous free-running Cuk converters. With a particular capacitor voltage as driving signal, synchronization is found possible. Averaged state equations and conditional Lyapunov exponents are used to predict the possibility of synchronization while computer simulations and PSPICE simulations provide the verification. The last phase gives suggestions for future research.

  16. A simple DC-DC convertor of high accuracy

    CERN Document Server

    Hausler, M

    1974-01-01

    Origin and dimension of measurement faults are given for the application of a current source driven convertor having parallel ring transformers. Particularly described in this paper is the behaviour of this dc convertor at measurements taken near the zero point and at change of current polarity. The importance of an additional ring transformer in order to improve the ripple of the device is explained; hints to choose the optimal number of turns of the ring transformer are given. (2 refs).

  17. Mesoscopic electronics beyond DC transport

    Science.gov (United States)

    di Carlo, Leonardo

    Since the inception of mesoscopic electronics in the 1980's, direct current (dc) measurements have underpinned experiments in quantum transport. Novel techniques complementing dc transport are becoming paramount to new developments in mesoscopic electronics, particularly as the road is paved toward quantum information processing. This thesis describes seven experiments on GaAs/AlGaAs and graphene nanostructures unified by experimental techniques going beyond traditional dc transport. Firstly, dc current induced by microwave radiation applied to an open chaotic quantum dot is investigated. Asymmetry of mesoscopic fluctuations of induced current in perpendicular magnetic field is established as a tool for separating the quantum photovoltaic effect from classical rectification. A differential charge sensing technique is next developed using integrated quantum point contacts to resolve the spatial distribution of charge inside a double quantum clot. An accurate method for determining interdot tunnel coupling and electron temperature using charge sensing is demonstrated. A two-channel system for detecting current noise in mesoscopic conductors is developed, enabling four experiments where shot noise probes transmission properties not available in dc transport and Johnson noise serves as an electron thermometer. Suppressed shot noise is observed in quantum point contacts at zero parallel magnetic field, associated with the 0.7 structure in conductance. This suppression evolves with increasing field into the shot-noise signature of spin-lifted mode degeneracy. Quantitative agreement is found with a phenomenological model for density-dependent mode splitting. Shot noise measurements of multi-lead quantum-dot structures in the Coulomb blockade regime distill the mechanisms by which Coulomb interaction and quantum indistinguishability correlate electron flow. Gate-controlled sign reversal of noise cross correlation in two capacitively-coupled dots is observed, and shown to

  18. Implementation of hierarchical control in DC microgrids

    DEFF Research Database (Denmark)

    Jin, Chi; Wang, Peng; Xiao, Jianfang

    2014-01-01

    DC microgrids are becoming popular in low-voltage distribution systems due to the better compatibility with photovoltaic panels, electric vehicles, and dc loads. This paper presents a practical dc microgrid developed in the Water and Energy Research Laboratory (WERL) in the Nanyang University...

  19. Hierarchical Power Sharing Control in DC Microgrids

    DEFF Research Database (Denmark)

    Peyghami Akhuleh, Saeed; Mokhtari, Hossein; Blaabjerg, Frede

    2016-01-01

    Because of the advances in power electronics, DC-based power systems, have been used in industrial applications such as data centers [18], space applications [10], aircraft [12], offshore wind farms, electric vehicles [56], DC home systems [5, 20], and high-voltage DC transmission systems...

  20. Primer reporte de empleo de marcadores AFLP en Asteraceae en Cuba

    Directory of Open Access Journals (Sweden)

    Grecia Montalvo Fernández

    2012-08-01

    Full Text Available Título en ingles: First report of the employment of AFLP markers in Asteraceae in Cuba. Resumen: Rhodogeron coronopifolius Griseb., es una especie vegetal de la familia Asteraceae, que se encuentra en peligro crítico de extinción. Es endémico de la provincia Villa Clara en la región central de Cuba. Habita en el matorral xeromorfo sub espinoso sobre serpentina. Existen solo cinco poblaciones naturales dentro de un área protegida, la principal causa de amenaza es la fragmentación de su hábitat por acciones antrópicas. Debido a su situación de conservación, se hace necesario realizar estudios de la diversidad genética de las poblaciones naturales para así generar información básica y diseñar una estrategia de conservación. El objetivo de este trabajo fue analizar de manera preliminar la diversidad genética de cuatro poblaciones de esta especie utilizando marcadores AFLP (Polimorfismo de Longitud de Fragmentos Amplificados. Se emplearon dos combinaciones de iniciadores y se evaluó el porcentaje de polimorfismo así como la similitud entre los individuos.  Se obtuvieron 165 loci de los cuales el 78,7 % fueron polimórficos. La población de mayor polimorfismo fue Corojito con 85,2%, de manera general el polimorfismo fue alto con valores entre 75 y  87%. La similitud entre los individuos también fue alta con un promedio de 0,74. El agrupamiento genético fue independiente a la población de procedencia, lo que sugiere que existe intercambio genético entre las poblaciones y que estas comparten más del 80 % de los alelos que fueron analizados. Los resultados obtenidos son importantes para el mantenimiento in situ de la especie y para tomar decisiones en aras de su conservación. Palabras clave: Rhodogeron coronopifolius, peligro de extinción, polimorfismo, conservación. Abstract: Rhodogeron coronopifolius Griseb., is a specie of Asteraceae family, in critical danger of extinction. It is an endemic of Villa Clara city in the

  1. Molecular phylogeny and biogeography of the Qinghai-Tibet Plateau endemic Nannoglottis (Asteraceae).

    Science.gov (United States)

    Liu, Jian-Quan; Gao, Tian-Gang; Chen, Zhi-Duan; Lu, An-Ming

    2002-06-01

    All taxa endemic to the Qinghai-Tibet Plateau are hypothesized to have originated in situ or from immediately adjacent areas because of the relatively recent formation of the plateau since the Pliocene, followed by the large-scaled biota extinction and recession caused by the Quaternary ice sheet. However, identification of specific progenitors remains difficult for some endemics, especially some endemic genera. Nannoglottis, with about eight species endemic to this region, is one such genus. Past taxonomic treatments have suggested its relationships with four different tribes of Asteraceae. We intend to identify the closest relatives of Nannoglottis by evaluating the level of monophyly, tribal delimitation, and systematic position of the genus by using molecular data from ndhF gene, trnL-F, and ITS region sequences. We find that all sampled species of Nannoglottis are a well-defined monophyly. This supports all recent taxonomic treatments of Nannoglottis, in which all sampled species were placed in one broadly re-circumscribed genus. Nannoglottis is most closely related to the Astereae, but stands as an isolated genus as the first diverging lineage of the tribe, without close relatives. A tentative relationship was suggested for Nannoglottis and the next lineage of the tribe was based on the ITS topology, the "basal group," which consists of seven genera from the Southern Hemisphere. Such a relationship is supported by some commonly shared plesiomorphic morphological characters. Despite the very early divergence of Nannoglottis in the Astereae, the tribe must be regarded to have its origin in Southern Hemisphere rather than in Asia, because based on all morphological, molecular, biogeographical, and fossil data, the Asteraceae and its major lineages (tribes) are supposed to have originated in the former area. Long-distance dispersal using Southeast Asia as a steppingstone from Southern Hemisphere to the Qinghai-Tibet Plateau is the most likely explanation for this

  2. DC-DC conversion powering for the CMS tracker at SLHC

    Energy Technology Data Exchange (ETDEWEB)

    Feld, L., E-mail: Lutz.Feld@cern.c [RWTH Aachen University, Sommerfeldstrasse 14, D-52074 Aachen (Germany); Jussen, R.; Karpinski, W.; Klein, K.; Merz, J.; Sammet, J. [RWTH Aachen University, Sommerfeldstrasse 14, D-52074 Aachen (Germany)

    2011-02-01

    A tracker powering scheme based on DC-DC converters close to the detector modules can supply more power through thinner cables. This will allow to satisfy the increased power demands of tracking systems at the SLHC. This article describes the development of DC-DC converters for upgrades of the CMS pixel and tracking systems and addresses system integration issues.

  3. DC-DC Conversion Powering for the CMS Tracker at SLHC

    CERN Document Server

    Feld, Lutz

    2010-01-01

    A tracker powering scheme based on DC-DC converters close to the detector modules can supply more power through thinner cables. This will allow to satisfy the increased power demands of tracking systems at the SLHC. This article describes the development of DC-DC converters for upgrades of the CMS pixel and tracking systems and addresses system integration issues.

  4. Full wave dc-to-dc converter using energy storage transformers

    Science.gov (United States)

    Moore, E. T.; Wilson, T. G.

    1969-01-01

    Full wave dc-to-dc converter, for an ion thrustor, uses energy storage transformers to provide a method of dc-to-dc conversion and regulation. The converter has a high degree of physical simplicity, is lightweight and has high efficiency.

  5. A DC-DC Conversion Powering Scheme for the CMS Phase-1 Pixel Upgrade

    CERN Document Server

    Feld, Lutz Werner; Marcel Friedrichs; Richard Hensch; Karpinski, Waclaw; Klein, Katja; Sammet, Jan Domenik; Wlochal, Michael

    2012-01-01

    The powering scheme of the CMS pixel detector will be described, and the performance of prototype DC-DC buck converters will be presented, including power efficiency, system tests with DC-DC converters and pixel modules, thermal management, reliability at low temperature, and studies of potential frequency locking betwe...

  6. The DC-DC Conversion Power System of the CMS Phase-1 Pixel Upgrade

    CERN Document Server

    Klein, Katja

    2014-01-01

    The power system of the Phase-1 pixel detector will be described and the performance of the new components, including DC-DC converters, DC-DC converter motherboards and various power distribution boards, will be detailed. The outcome of system tests in terms of electrical behaviour, thermal management and pixel module performance will be discussed.

  7. A Survey on Voltage Boosting Techniques for Step-Up DC-DC Converters

    DEFF Research Database (Denmark)

    Forouzesh, Mojtaba; Siwakoti, Yam Prasad; Gorji, Saman Asghari;

    2016-01-01

    Step-up dc-dc converters are used to boost the voltage level of the input to a higher output level. Despite of its features such as simplicity of implementation, the fundamental boost dc-dc converter has shortcomings such as low boost ability and low power density. With these limitations, researc...

  8. AC-DC PFC Converter Using Combination of Flyback Converter and Full-bridge DC-DC Converter

    Directory of Open Access Journals (Sweden)

    Moh. Zaenal Efendi

    2014-06-01

    Full Text Available This paper presents a combination of power factor correction converter using Flyback converter and Full-bridge dc-dc converter in series connection. Flyback converter is operated in discontinuous conduction mode so that it can serve as a power factor correction converter and meanwhile Full-bridge dc-dc converter is used for dc regulator. This converter system is designed to produce a 86 Volt of output voltage and 2 A of output current. Both simulation and experiment results show that the power factor of this converter achieves up to 0.99 and meets harmonic standard of IEC61000-3-2. Keywords: Flyback Converter, Full-bridge DC-DC Converter, Power Factor Correction.

  9. Five-Level Active-Neutral-Point-Clamped DC/DC Converter for Medium-Voltage DC Grids

    DEFF Research Database (Denmark)

    Liu, Dong; Deng, Fujin; Chen, Zhe

    2017-01-01

    effectively eliminate high voltage leaps caused by the dead time effect. In addition, a capacitor voltage control strategy is proposed for the 5L-ANPC dc/dc converter to ensure the balanced flying capacitor voltage and desired five-level voltage waveforms. Finally, simulation and experimental studies......This paper proposes a five-level active-neutralpoint- clamped (5L-ANPC) dc/dc converter for applications in medium voltage dc (MVDC) grids. A modulation strategy is proposed for the 5L-ANPC dc/dc converter to generate multilevel voltage waveforms, which can effectively reduce voltage change rate dv...... are conducted, and the results have verified the proposed converter and control strategies....

  10. A Feed-Forward Control Realizing Fast Response for Three-Branch Interleaved DC-DC Converter in DC Microgrid

    Directory of Open Access Journals (Sweden)

    Haojie Wang

    2016-07-01

    Full Text Available It is a common practice for storage batteries to be connected to DC microgrid buses through DC-DC converters for voltage support on islanded operation mode. A feed-forward control based dual-loop constant voltage PI control for three-branch interleaved DC-DC converters (TIDC is proposed for storage batteries in DC microgrids. The working principle of TIDC is analyzed, and the factors influencing the response rate based on the dual-loop constant voltage control for TIDC are discussed, and then the method of feed-forward control for TIDC is studied to improve the response rate for load changing. A prototype of the TIDC is developed and an experimental platform is built. The experiment results show that DC bus voltage sags or swells caused by load changing can be reduced and the time for voltage recovery can be decreased significantly with the proposed feed-forward control.

  11. Phytochemistry and quantification of polyphenols in extracts of the Asteraceae weeds from Diamantina, Minas Gerais state, Brazil Fitoquímica e quantificação de polifenóis em extratos de plantas daninhas Asteraceae de Diamantina, Minas Gerais, Brasil

    Directory of Open Access Journals (Sweden)

    F. Petacci

    2012-03-01

    Full Text Available Asteraceae weeds are rich in chemicals that have biological and pharmaceutical activities. The aims of this work were to describe the phytochemistry and quantify the polyphenols in ethanol extracts from leaves of 12 species of Asteraceae weeds collected in Diamantina, Minas Gerais State, Brazil. The screening of Asteraceae extracts revealed the presence of tannins, steroids, triterpenes, anthocyanins, and flavonoids. The total phenolic content was high in extracts of Lychnophora ericoides (147.97 ± 2.66, Lepidaploa lilacina (141.11 ± 1.99, and Eremanthus elaeagnus (134.61 ± 7.81 and low in extracts of Lychnophora ramosissima (32.65 ± 0.70, and Lychnophora sp. (54.03 ± 0.73. Extracts of Asteraceae weeds from Diamantina could have potential for biological studies that are searching for new pesticides and drugs.Plantas daninhas Asteraceae são ricas em substâncias químicas com atividades biológicas e farmacêuticas. Os objetivos deste trabalho foram descrever a fitoquímica e quantificar os polifenóis em extratos etanólicos de folhas de 12 espécies de plantas daninhas Asteraceae coletadas em Diamantina, Minas Gerais, Brasil. A triagem de extratos de Asteraceae revelou a presença de taninos, esteroides, triterpenos, antocianinas e flavonoides. O conteúdo de fenóis totais foi alto para extratos de Lychnophora ericoides (147,97 ± 2,66, Lepidaploa lilacina (141,11 ± 1,99 e Eremanthus elaeagnus (134,61 ± 7,81 e baixo em extratos de Lychnophora ramosissima (32,65 ± 0,70 e Lychnophora sp. (54,03 ± 0,73. Extratos de plantas daninhas Asteraceae de Diamantina podem ter potencial em estudos biológicos que estão à procura para pesticidas e drogas.

  12. Leaf and stem microscopic identification of Tithonia diversifolia (Hemsl. A. Gray (Asteraceae

    Directory of Open Access Journals (Sweden)

    Márcia do Rocio Duarte

    2012-03-01

    Full Text Available Tithonia diversifolia (Hemsl. A. Gray is an Asteraceae shrub, popularly known as Mexican sunflower and cultivated for ornamental and therapeutic uses in different countries. In folk medicine, it is of value for treating diabetes, malaria and infectious diseases. These indications have been corroborated by various pharmacological assays. Given the lack of data on anatomical aspects of T. diversifolia, this work aimed to investigate the leaf and stem microscopic characters of this medicinal plant and potential vegetal drug. Samples of mature leaves and young stems were sectioned and stained. Histochemical tests and scanning electron microscopy were also performed. The leaf has anomocytic stomata on both sides, dorsiventral mesophyll and several collateral vascular bundles arranged as a ring in the midrib. The stem shows angular-tangential collenchyma, an evident endodermis and sclerenchymatic caps adjoining the phloem. The main characters for anatomical identification are the different types of trichome (non-glandular, capitate and non-capitate glandular, the midrib features and the localization of the secretory ducts near the vascular system.Tithonia diversifolia (Hemsl. A. Gray é um arbusto da família Asteraceae, popularmente conhecido como girassol-mexicano e cultivado como ornamental e medicinal em vários países. Tradicionalmente, é usado no tratamento de diabetes, malária e doenças infecciosas. Essas indicações têm sido corroboradas por diversos ensaios farmacológicos. Em razão das escassas informações sobre aspectos anatômicos de T. diversifolia, este trabalho objetivou investigar os caracteres microscópicos foliares e caulinares dessa planta medicinal e potencial droga vegetal. Amostras de folhas adultas e caules jovens foram fixadas, seccionadas e coradas. Testes histoquímicos e microscopia eletrônica de varredura foram também realizados. A folha apresenta estômatos anomocíticos em ambas as superfícies, mesofilo

  13. Anatomy of the underground system in Vernonia grandiflora Less. and V. brevifolia Less. (Asteraceae

    Directory of Open Access Journals (Sweden)

    Adriana Hissae Hayashi

    2007-11-01

    Full Text Available This work dealt with the anatomy of the underground system in Vernonia grandiflora Less. and V. brevifolia Less. (Vernonieae; Asteraceae, two perennial geophytes, to elucidate their ability to sprout in the Brazilian Cerrado conditions. V. grandiflora, a subshrubby species, possessed a thickened underground system constituted by a xylopodium and many tuberous roots. The xylopodium had stem and root structure and its buds were axillary or originated from the cortical parenchyma proliferation. The tuberous roots produced by this organ were adventitious and accumulated inulin-type fructans mainly in the cortical parenchyma. The thickened underground system of V. brevifolia, an herbaceous species, was a tuberous primary root whose buds originated from the proliferated pericycle. The occurrence of these bud-forming underground systems, which stored reserve compounds, enabled these plants to survive throughout unfavourable environmental conditions in the Cerrado, such as dry season and frequent fires in the winter.Este trabalho teve como objetivo estudar a anatomia dos sistemas subterrâneos de Vernonia grandiflora Less. e V. brevifolia Less. (Vernonieae; Asteraceae, duas geófitas perenes, a fim de esclarecer sua capacidade para brotar em condições de Cerrado. O sistema subterrâneo espessado de V. grandiflora, uma espécie subarbustiva, é constituído pelo xilopódio e por várias raízes tuberosas. O xilopódio possui estrutura mista (radicular e caulinar e suas gemas são de origem axilar ou se originam a partir da proliferação do parênquima cortical. As raízes tuberosas produzidas por este órgão são adventícias e acumulam frutanos do tipo inulina, principalmente no parênquima cortical. Em V. brevifolia, uma espécie herbácea, o sistema subterrâneo espessado é constituído pela raiz primária cujas gemas são originadas a partir do periciclo proliferado. A ocorrência destes sistemas subterrâneos gemíferos, que armazenam compostos

  14. Transformerless dc-Isolated Converter

    Science.gov (United States)

    Rippel, Wally E.

    1987-01-01

    Efficient voltage converter employs capacitive instead of transformer coupling to provide dc isolation. Offers buck/boost operation, minimal filtering, and low parts count, with possible application in photovoltaic power inverters, power supplies and battery charges. In photovoltaic inverter circuit with transformerless converter, Q2, Q3, Q4, and Q5 form line-commutated inverter. Switching losses and stresses nil because switching performed when current is zero.

  15. Power Network impedance effects on noise emission of DC-DC converters

    Science.gov (United States)

    Esteban, M. C.; Arteche, F.; Iglesias, M.; Gimeno, A.; Arcega, F. J.; Johnson, M.; Cooper, W. E.

    2012-01-01

    The characterization of electromagnetic noise emissions of DC-DC converters is a critical issue that has been analyzed during the desing phase of CMS tracker upgrade. Previous simulation studies showed important variations in the level of conducted emissions when DC-DC converters are loaded/driven by different impedances and power network topologies. Several tests have been performed on real DC-DC converters to validate the Pspice model and simulation results. This paper presents these test results. Conducted noise emissions at the input and at the output terminals of DC-DC converters has been measured for different types of power and FEE impedances. Special attention has been paid to influence on the common-mode emissions by the carbon fiber material used to build the mechanical structure of the central detector. These study results show important recommendations and criteria to be applied in order to decrease the system noise level when integrating the DC-DC.

  16. FLYWHEEL AND A DC MACHINE

    Directory of Open Access Journals (Sweden)

    IVAN ALCALÁ

    2014-01-01

    Full Text Available Este artículo describe el análisis, modelado y simulación de un vehículo eléctrico (EV enfocado al desarrollo de un banco de pruebas para reproducir la dinámica del EV. El banco está formado por un drive de motor de inducción (IM acoplado directamente a una máquina de DC y a un volante de inercia a través de una transmisión. El volante de inercia y la máquina de DC reproducen la dinámica y las fuerzas que actúan en el vehículo. Se propone una metodología para diseñar un banco de pruebas de EV para estudiar el comportamiento de vehículos eléctricos cercano a las condiciones de operación reales. El análisis de las fuerzas en el EV en conjunto con la máquina DC define las condiciones de operación del EV. El modelado y la simulación son desarrollados en MATLAB/Simulink, el banco de pruebas implementado es controlado por un DSP. Finalmente, los resultados de simulación y experimentales obtenidos validan el funcionamiento del banco de prueba.

  17. 76 FR 13543 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

    Science.gov (United States)

    2011-03-14

    ... Model DC-9-81 (MD- 81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 Airplanes AGENCY... Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590. Hand Delivery: Deliver to Mail... stabilizer is similar in design and loading to that of the Model DC-9-81 (MD-81), DC- 9-82 (MD-82),...

  18. DC

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    金属材质机身拥有三层镀膜工艺,1210万像素CCD,采用4倍变焦28mm广角镜头。配合16:9屏幕以及720p高清短片拍摄为卖点.整体感觉有别于佳能一贯的风格。

  19. DC

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    近期.单反市场最受期待的产品非尼康D40x莫属了,D40x的上市弥补了尼康在低价位千万像素级别无产品的空白,形成了其完整的产品线,D200、D80,D40x和D40.随着D70s的停产,D40x充当这一价位的角色,直接挑战佳能400D及索尼a100.目前千万像素已经普及到了低档单反之中,不难看出尼康D40x是2007年单反市场中的一颗重磅炸弹,相信随着D40x的上市单反的价格战又会再次拉开。

  20. DC

    Institute of Scientific and Technical Information of China (English)

    姚文秋

    2005-01-01

    阳春三月,细雨绵绵,冷却了火爆的年前DC市场,但是也活跃离一部分即将崭露头角的新芽。纵观市场,几大品牌中要数尼康的销售情况最好,这主要是尼康的机器价位合理,外形时尚,功能全面,品质优良。比如尼康5200,这款机器500万像素,才两多块,而且外观十分小巧,性价比很高。

  1. DC

    Institute of Scientific and Technical Information of China (English)

    姚文秋

    2005-01-01

    八月,驴友们的黄金时节。九寨沟清凉的水、张家界翠绿的树、黄山神秘的云雾……都是大家向往的好去处。拿起自己心爱的DC把这些美景定格保留作为美好的纪念是必不可少啦。而厂商们当然不会放过暑期这最后的机会,力求分得暑期市场的最后一块蛋糕。总而言之,与硝烟弥漫的七月市场相比,本月DC市场仍然延续着上月的强劲势头。

  2. DC

    Institute of Scientific and Technical Information of China (English)

    姚文秋

    2005-01-01

    纵观年底DC市场,风云变幻,惊喜不断。各大DC厂商纷纷对自己的产品价格进行调整。降价似乎成了最主流的声音。市场霸主佳能继PowerShot S50在市场上大获成功之后,在今年夏天紧接着发布了其第一款5百万像素的相机PowerShot S60,近这款数码相机做了一次大的价格调整。另外,随着家庭用户要求的不断增加,更高水平的家用数码相机也浮出水面。

  3. DC

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    一般来说数码相机镜头等效焦距在200mm以上的机型,就可以称之为长焦相机。长焦数码相机因其超长的焦距、丰富的功能受到了消费者的喜爱,它们也一直是消费级数码相机市场的热点所在。但是由于过大的体积,让携带长焦相机成为一件很费力的事情。现在,随着机身设计的进一步轻便和防抖技术的进一步成熟,长焦相机正在逐渐变得更加小巧、实用。原来拥有超长焦距的机型现在也可以像卡片机一样随身携带,近期上市的索尼DSC—H3就是其中不错的一款。

  4. DC

    Institute of Scientific and Technical Information of China (English)

    姚文秋

    2005-01-01

    DC市场在经过10月份的促销鏖战之后,行情慢慢稳定下来,各个厂家也不断推出自己在2005下半年的主流DC。家用机和长焦数码已经进入了一个新格局。以前我们耳熟能详的佳能A95、尼康5900等一批经典机型已经慢慢退下一线,取而代之的最新产品昂首进入激烈的数码相机战场。而时尚轻薄是在这些新品中刮起来的一阵旋风。

  5. DC

    Institute of Scientific and Technical Information of China (English)

    姚文秋

    2005-01-01

    进入七月,学校都已放假,不少学生教师也将外出旅游当作假期第一选择。要外出旅游当然少不了带上心爱的DC啦。有需求就会有供给,这是市场规律的铁定原则,因此各大厂商自然不会错过机会一一推新的推新、降价的降价。整个市场一片热火朝天的场面。

  6. DC

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    本月市场动态:第十届中国国际照相机械影像器材与技术博览会(2007 CHINA P&E)于7月1日在北京落幕,作为目前中国规模最大的摄影器材展会,其影响力不言而喻。国际知名的几大品牌,如佳能.尼康,索尼均带来了主流的产品,腾龙、适马也推出了各自最新的镜头。从展出的产品来看.有一个非常明显的信号就是,

  7. In vitro effect of Acanthospermum australe (Asteraceae extracts on Acanthamoeba polyphaga trophozoites

    Directory of Open Access Journals (Sweden)

    LC Castro

    2013-01-01

    Full Text Available Acanthamoeba is a free-living protozoan widely distributed in the environment, occurring in vegetative trophozoite and resistance cyst stages during its life cycle. It constitutes an etiological agent of Acanthamoeba keratitis, a disease that may cause severe ocular inflammation and blindness. New drugs can be developed from molecules found in plants and thus help in its difficult treatment. Acanthospermum australe (Asteraceae, a plant used in folk medicine, had its effect tested on Acanthamoeba polyphaga. Aqueous and ethanolic extracts of A. austral were obtained from aerial parts for infusion and static maceration, respectively. Concentrations of 10, 5, 2.5, 1.25 and 0.625 mg/ml of the extract were tested against Acanthamoeba polyphaga trophozoites. The cytotoxic effect of the extracts was tested in mammalian cells using the 3-(4, 5-dimethylthiazol-2-yl-2, 5-diphenyltetrazolium bromide (MTT assay. RESULTS: The 10 mg/ml concentration of ethanolic extract was lethal to 100% of the A. polyphaga trophozoites in 24 h and both extracts presented cytotoxic effect against mammalian cells. These findings suggest that the A. austral ethanolic extract may have compounds with relevance to the development of new amoebicidal drugs.

  8. Two new species of Asteraceae from Northern and Western Cape, South Africa and a new synonym

    Directory of Open Access Journals (Sweden)

    J. C. Manning

    2005-12-01

    Full Text Available We recognize two new species of Asteraceae from the winter rainfall belt of South Africa and reduce a third to synonomy.  Senecio speciosissimus sp. nov. has been confused with  S. coleophyllus Turcz. in the past but is distinguished by its taller stature, larger and more finely serrated leaves, and congested synflorescences containing (6-l 5-40 flowerheads. The two species are also geographically separated:  S. speciosissimus occurs in the Hottentots Holland and Franschhoek Mountains of the southwestern Cape, whereas S.  coleophyllus is endemic to the Riviersonderend Mountains.  Chrysocoma hantamensis sp. nov. is a distinctive new species endemic to the Bokkeveld and Roggeveld Plateaus. It is distinguished by its resprouting habit. 3-5-fid leaves and large capitula, 12-15 mm in diameter, with lanceolate. 3-veined involucral bracts, the largest 9 - 1 0 x 2 mm. Investigation of the variation in leaf morphology of the two radiate species of Oncosiphon, O. africanum (PJ.Bergius Kallersjo and  O. glabratum (Thunb. Kallersjo. reveals that only one species can be maintained, and O. glabratum is accordingly reduced to synonomy in O. africanum.

  9. Polyphenolic-polysaccharide conjugates from plants of Rosaceae/Asteraceae family as potential radioprotectors.

    Science.gov (United States)

    Zbikowska, Halina Malgorzata; Szejk, Magdalena; Saluk, Joanna; Pawlaczyk-Graja, Izabela; Gancarz, Roman; Olejnik, Alicja Klaudia

    2016-05-01

    Polyphenolic-polysaccharide macromolecular, water-soluble glycoconjugates, isolated from the selected medicinal plants of Rosaceae/Asteraceae family: from leaves of Fragaria vesca L., Rubus plicatus Whe. et N. E., and from flowering parts of Sanguisorba officinalis L., and Erigeron canadensis L., were investigated for their ability to protect proteins and lipids of human plasma against γ-radiation-induced oxidative damage. Treatment of plasma with plant conjugates (6, 30, 150 μg/ml) prior exposure to 100 Gy radiation resulted in a significant inhibition of lipid peroxidation, evaluated by TBARS levels; conjugates isolated from E. canadensis and R. plicatus and a reference flavonoid quercetin showed similar high potential (approx. 70% inhibition, at 6 μg/ml). The conjugates prevented radiation-induced oxidation of protein thiols and significantly improved plasma total antioxidant capacity, estimated with Ellman's reagent and ABTS(.+) assay, respectively. The results demonstrate by the first time a significant radioprotective capability of the polyphenolic-polysaccharide conjugates isolated from E. canadensis, R. plicatus, S. officinalis and to the less extent from F. vesca. The abilities of these substances to inhibit radiation-induced lipid peroxidation and thiol oxidation in plasma seems to be mediated, but not limited to ROS scavenging activity.

  10. Antioxidant activities of extracts from Barkleyanthus salicifolius (Asteraceae) and Penstemon gentianoides (Scrophulariaceae).

    Science.gov (United States)

    Domínguez, Mariana; Nieto, Antonio; Marin, Juan C; Keck, Anna-Sigrid; Jeffery, Elizabeth; Céspedes, Carlos L

    2005-07-27

    Various extracts of the aerial parts of Barkleyanthus salicifolius (Asteraceae) and Penstemon gentianoides (Scrophulariaceae) have been used in folk medicine to treat many ailments, particularly inflammation and migraine. Neither the bioactive components responsible nor the mechanisms involved have been evaluated. Here are reported antioxidant activities of their methanol, dichloromethane, and ethyl acetate extracts. Samples were evaluated for oxygen radical absorption capacity (ORAC), ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging, and inhibition of the formation of thiobarbituric acid reactive species (TBARS), a measure of lipid peroxidation. Antioxidant activities were strongly correlated with total polyphenol content. The most active extracts from P. gentianoides in scavenging DPPH radicals and inhibiting TBARS formation were the methanol extract (A) and a further ethyl acetate extract of this (E). Partition E was further divided into eight fractions, and both E and the fractions were compared for activity against butylated hydroxytoluene, quercetin, and tocopherol. Partition E and the most active fractions, 5 and 6, were found to have I(50) values of 14.1, 38.6, and 41.8 ppm, respectively, against DPPH and 18.5, 26.0, and 12.7 ppm, respectively, against TBARS formation. Consistent with this finding, partition E and fractions 4-6 had the greatest ORAC and FRAP values. These results show that these plants could be useful antioxidant sources.

  11. Antimicrobial and antioxidative activity of various leaf extracts of Amphoricarpos vis. (Asteraceae taxa

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    Gavrilović Milan

    2016-01-01

    Full Text Available The antimicrobial and antioxidative activities of diethyl ether, 80% methanol and 50% acetone extracts of the leaves of three Amphoricarpos taxa (Asteraceae; A. neumayerianus, A. autariatus ssp. autariatus and A. autariatus ssp. bertisceus from the Balkan Peninsula were investigated. The antimicrobial activity was determined by the broth microdilution assay against eight bacterial and eight fungal species. The in vitro antioxidative activity was assessed by the DPPH assay. The total phenolic and flavonoid contents were also determined. The most sensitive bacterial species were Bacillus cereus and Staphylococcus aureus. The best antibacterial potential was obtained for the methanol extract of A. neumayerianus, while the diethyl ether extract of this species showed the lowest effect. In general, the tested extracts showed higher activity than the commercial antibiotics streptomycin and ampicillin. Also, all micromycetes were sensitive to the tested extracts. The most sensitive was Trichoderma viride. The highest and lowest antifungal effect was determined in A. a. ssp. autariatus for the diethyl ether and acetone extracts, respectively. The highest total phenolic and flavonoid contents were determined in the methanol extract of A. a. autariatus. The best antioxidative activity was demonstrated by the methanol extract of A. a. ssp. autariatus as comparing to matching extracts from the other two taxa.

  12. [Occupational contact allergy to feverfew Tanacetum parthenium (L.) Schultz-Bip.; Asteraceae].

    Science.gov (United States)

    Hausen, B M

    1981-01-01

    Allergic Contact Dermatitis due to Feverfew Tanacetum parathenium, Asteraceae. After breeding and selling a new ornamental form of feverfew (Tanacetum parthenium (L.) Schulz-Bip. = Chrysanthemum parthenium (L.) Bernh.), sold the flower markets under the misleading name, "chamomile", a 40 year old female florist developed after a half year handling recurrent dermatitis of the face, neck, hands and forearms. Epicutaneous tests revealed positive reactions to 10 species of the Compositae family, including chrysanthemums, aster Gaillardia. Arnica and truc chamomile. However, the strongests results were seen with petals and leaves of feverfew. Renewed strong reactions to parthenolid, the main sesquiterpene lactonic constitutent of European feverfew demonstrated that this compound was the responsible contact allergen. The sensitizing capacity of parthenolid has been shown in previous investigations in guina pigs. Furthermore, cross-reactionsto parthenolid were frequently observed in chrysanthemum sensitive persons. Mexican samples of feverfew contain the eudesmanolid santamarin and traces of other sesquiterpene lactones, but parthenolid is lacking. Further studies are needed to clarify the sensitizing potency of this related compound.

  13. Protein hydrolysate as a component of salinized soil in the cultivation of Ageratum houstonianum Mill. (Asteraceae

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    Renata Matraszek

    2015-10-01

    Full Text Available The aim of the present study was to evaluate the possibility of using a protein hydrolysate, Hemozym N-K 4.5-6, as a component of salinized soil in the cultivation of flossflower (Ageratum houstonianum Mill., Asteraceae. The experiment was focused on the yield and decorative value of A. houstonianum, grown under different concentrations of NaCl and/or Hemozym. Ageratum houstonianum plants were grown in the soil under different NaCl salinity (EC: 0.28 – as control or 3.25 dS m−1 – salt stress or/and Hemozym dose (0, 0.07 or 0.14 ml kg−1. The results of the experiment imply that A. houstonianum is sensitive to salinity. The application of Hemozym to both unsalinized and salinized soils caused an increase in the yield of the plant organs (roots, stems, leaves, and inflorescence, the number of leaves, and the chlorophyll content without significant changes in the carotenoids. Moreover, an increase in the number and size of first-order inflorescences (heads as well as more intensive flower color were observed. Thus, it can be stated that the protein hydrolysate studied can be a beneficial component of both salinized and unsalinized soils in the cultivation of A. houstonianum.

  14. Embryology of Ageratum conyzoides L. and A. fastigiatum R.M. King & H. Rob. (Asteraceae

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    Rafael de Oliveira Franca

    2015-03-01

    Full Text Available Ageratum has a complex circumscription, and recent studies have indicated its polyphyletism. The genus has been placed in the tribe Eupatorieae whose embryology is not fully known. Embryological data are conservative and important indicators of phylogenetic relationships and can improve family relationships. This study presents, for the first time in Eupatorieae, embryological data for Ageratum conyzoides and A. fastigiatum. Both species have common features of the family such as a unitegmic anatropous ovule, basal placentation, secretory tapetum, Polygonum megagametophyte, and Asterad embryogenesis. The data obtained reinforce the heterogeneity of the family embryology and show, for the first time, the anther wall development of the monocotyledonous type for Asteraceae. The species studied show also differences between themselves. A. conyzoides has bisporangiated and introrse anthers, conspicuous pappus, and cypselae with trichomes on the ribs, whereas A. fastigiatum has tetrasporangiate and latrorse anthers, pappus absent at maturity, and glabrous cypselae. The data presented support recent phylogenetic molecular studies, suggesting the replacement of A. fastigiatum to another genus along with Gyptidinae.

  15. Patterns of MADS-box gene expression mark flower-type development in Gerbera hybrida (Asteraceae

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    Teeri Teemu H

    2006-06-01

    Full Text Available Abstract Background The inflorescence of the cut-flower crop Gerbera hybrida (Asteraceae consists of two principal flower types, ray and disc, which form a tightly packed head, or capitulum. Despite great interest in plant morphological evolution and the tractability of the gerbera system, very little is known regarding genetic mechanisms involved in flower type specification. Here, we provide comparative staging of ray and disc flower development and microarray screening for differentially expressed genes, accomplished via microdissection of hundreds of coordinately developing flower primordia. Results Using a 9K gerbera cDNA microarray we identified a number of genes with putative specificity to individual flower types. Intrestingly, several of these encode homologs of MADS-box transcription factors otherwise known to regulate flower organ development. From these and previously obtained data, we hypothesize the functions and protein-protein interactions of several gerbera MADS-box factors. Conclusion Our RNA expression results suggest that flower-type specific MADS protein complexes may play a central role in differential development of ray and disc flowers across the gerbera capitulum, and that some commonality is shared with known protein functions in floral organ determination. These findings support the intriguing conjecture that the gerbera flowering head is more than a mere floral analog at the level of gene regulation.

  16. Polyphenolic content and antioxidant activity of some wild Saudi Arabian asteraceae plants

    Institute of Scientific and Technical Information of China (English)

    Abdelaaty A Shahat; Abeer Y Ibrahim; Mansour S Elsaid

    2014-01-01

    Objective:To study the antioxidant properties of crude extract of differentAsteraceae plants. Methods:The antioxidant properties of six extracts were evaluated using different antioxidant tests, including free radical scavenging, reducing power, metal chelation, superoxide anion radical scavenging, total antioxidant capacity and inhibition of lipid peroxidation activities.Results:Picris cyanocarpa(P. cyanocarpa) andAnthemis deserti(A. deserti) had powerful antioxidant properties as radical scavenger, reducing agent and superoxide anion radical scavenger while Achillia fragrantissima(A. fragrantissima) andArtemissia monosperma(A. monosperma) were the most efficient as ion chelator(100% at100,200 and400 μg/mL)A. fragrantissima and Rhantarium appoposum(R. appoposum) showed100% inhibition on peroxidation of linoleic acid emulsion at200 and400 μg/mL, while butylatedhydroxy toluene and ascorbic acid showed100 and95% inhibition percentage at400 μg/mL, respectively.Those various antioxidant activities were compared to standard antioxidants such as butylated hydroxyl toluene and ascorbic acid. Conclusions:In most testsP. cyanocarpa andA. deserti had powerful antioxidant properties as radical scavenger, reducing agent and superoxide anion radical scavenger.

  17. Diversity of pyrrolizidine alkaloids in native and invasive Senecio pterophorus (Asteraceae): implications for toxicity.

    Science.gov (United States)

    Castells, Eva; Mulder, Patrick P J; Pérez-Trujillo, Míriam

    2014-12-01

    Changes in plant chemical defenses after invasion could have consequences on the invaded ecosystems by modifying the interactions between plants and herbivores and facilitating invasion success. However, no comprehensive biogeographical studies have yet determined the phenotypic levels of plant chemical defenses, as consumed by local herbivores, covering large distributional areas of a species. Senecio pterophorus is a perennial shrub native to Eastern South Africa, expanded into Western South Africa and introduced into Australia and Europe. As other Asteraceae, S. pterophorus contains pyrrolizidine alkaloids (PAs) toxic to vertebrate and invertebrate herbivores. Here we analyzed S. pterophorus PAs by LC-MS/MS on foliage sampled across its entire distributional range, including the native and all non-native areas. PA concentrations and diversity was very high: we found 57 compounds belonging to 6 distinct necine base-types, including the highly toxic 1,2-unsaturated PAs (retronecine and otonecines) and the less toxic 1,2-saturated PAs (platynecine and rosmarinecines). Plants from different origins diverged in their PA absolute and relative concentrations. Rosmarinine was the most abundant compound in Australia and South Africa, but it was nearly absent in Europe. We characterized three plant chemotypes: retrorsine-senkirkine chemotype in Eastern South Africa, rosmarinine chemotype in Australia and Western South Africa, and acetylseneciphylline chemotype in Europe. PA absolute concentrations were highest in Australia. The increased absolute and relative concentrations of retronecine PAs from Australia and Europe, respectively, indicate that S. pterophorus is potentially more toxic in the invasive range than in the native range.

  18. The effects of extraction method on recovery rutin from Calendula officinalis L. (Asteraceae

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    Frederico Severino Martins

    2014-01-01

    Full Text Available Background: Calendula officinalis L. (Asteraceae is a Mediterranean specie, but in Europe and America it is cultivated for ornamental or medicinal purposes. This species is widely used for presenting activities, antiinflammatory antibacterial and antioxidant. However the therapeutic action is linked to the amount of assets of the extracted raw material. The extraction method of bioactive compounds is an important step in the manufacturing of herbal medicines, because secondary metabolites with therapeutic potential are usually found in small quantities in plant materials. Objective: Due the medical and commercial importance of C. officinalis, this study aimed to evaluate the impact of the extraction method on the quality of herbal extract and optimize the extraction of rutin from C. officinalis. Materials and Methods : The extraction of rutin was performed by ultrasound and shaker and the optimized conditions were determined by response surface methodology. Results: The results of ultrasound extraction assisted (UEA and maceration dynamic (MD showed that rutin yield ranged from 0.218 to 2.28% (w/w when extract by ultrasound and 0.1-1.44% by MD. The optimal extraction condition for rutin (2.48% to UEA or 1.46% to MD from C. officinalis by UEA or MD were a 19-22 min extraction, ethanol: water ratio of 35-40% and 0.05-0.056 mg/mL to raw material: solvent ratio. Conclusion: The UEA is more efficient to extraction rutin.

  19. Identification and quantification of hepatotoxic pyrrolizidine alkaloids in the Ethiopian medicinal plant Solanecio gigas (Asteraceae).

    Science.gov (United States)

    Asres, K; Sporer, F; Wink, M

    2007-09-01

    The pyrrolizidine alkaloid content of Solanecio gigas (Vatke) C. Jeffrey (Asteraceae), an Ethiopian medicinal plant widely used for the treatment of colic, diarrhea, gout, otitis media, typhoid fever, and noted for its wound dressing and antiabortifacient activities was studied. The flower and leaf extracts contained 0.19% and 0.14% alkaloids (dry weight), respectively. GLC-MS analysis indicated that all the alkaloids in the flowers are pyrrolizidine alkaloids (PAs), whereas the leaves contain other type of alkaloids with PAs occurring in low concentrations. Roughly, 80% and 90% of the total PAs in the flowers and the leaves, respectively, were shown to occur as N-oxides. Eighteen alkaloids were detected in the flower extract with the retronecine type twelve-membered macrocyclic diesters integerrimine, senecionine and usaramine comprising 82% of the total PA content. Analysis of the PA profile of the leaves indicated that it has a simpler pattern than the one observed for the flowers. Only five PAs were detected in the leaves with integerrimine making up about 50% of the total PAs. Quantification of the PA content by GLC showed that the flowers and leaves contain 3321.21 and 84.84 microg per 10 g of dried plant material, respectively. These results indicate that users of this herb are at high risk of poisoning since the most toxic twelve membered macrocyclics of the retronecine type are the dominant PAs in the plant.

  20. Piptocarpha angustifolia (VernonIeae, Asteraceae, nueva cita para la flora argentina

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    Massimiliano Dematteis

    2012-12-01

    Full Text Available El género Piptocarpha R. Br. posee 46 especies distribuidas ampliamente desde el sur de Mexico hasta el noreste de Argentina y sur de Brasil. Las especies son arbustos apoyantes o raramente árboles, con inflorescencias axilares formadas generalmente por glomérulos globosos. Para Argentina solamente se ha citado a P. sellowii (Sch. Bip. Baker como único representante del género. En el presente trabajo se cita por primera vez para Argentina a P. angustifolia Dusén ex Malme, que se diferencia de la otra especie de Piptocarpha por tener hábito arbóreo y glomérulos con menor número de capítulos, entre otros caracteres.Piptocarpha angustifolia (Vernonieae, Asteraceae, a new cite for the Argentinean flora. The genus Piptocarpha R. Br. contains 46 species widely distributed from southern Mexico to northeastern Argentina and southern Brasil. The species are scandent shrubs or rarely trees, with axilary inflorescences composed of globose clusters. For Argentina has been only reported to P. sellowii (Sch. Bip. Baker as the single member of the genus. In the present paper is reported for the first time for Argentina to P. angustifolia Dusén ex Malme, which can be distinguished from the remaining species of Piptocarpha by the tree habit and the inflorescence clusters having a lesser number of heads, among other features.

  1. Aspectos de la biología reproductiva de Stevia rebaudiana (Asteraceae

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    Irene Caponio

    2017-06-01

    Full Text Available El género SteviaCav. (Asteraceae presenta alrededor de 200 especies en el continente americano. Stevia rebaudiana (Bertoni Bertoni, originaria de Paraguay, es la única especie cultivada. Ha sido ampliamente estudiada desde el punto de vista químico, por los principios activos que poseen sus hojas. Sin embargo existe controversia respecto a su sistema reproductivo, ya que es considerada apomíctica obligada por algunos autores, mientras otros la consideran de reproducción sexual. A los efectos de clarificar esta cuestión se realizaron estudios de: megasporogénesis, megagametogénesis, fenología de la floración, viabilidad de polen y receptividad estigmática en tres ecotipos en condiciones de autopolinización y polinización cruzada. De acuerdo a los resultados obtenidos, las plantas analizadas se reproducen sexualmente y poseen un sistema de autoincompatibilidad que impide la autofertilización.

  2. Control of Three Stored−Product Beetles with Artemisia haussknechtii (Boiss (Asteraceae Essential Oil

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    Seyed Mehdi Hashemi

    2012-12-01

    Full Text Available Fumigant toxicity of the essential oil of aerial parts from Artemisia haussknechtii (Boiss (Asteraceae was investigated against the cowpea weevil Callosobruchus maculatus (Fab., the rice weevil Sitophilus oryzae (L., and the red flour beetle Tribolium castaneum (Herbst. Dry ground plants were subjected to hydro−distillation using a Clevenger−type apparatus and the chemical composition of the volatile oil was studied by gas chromatography−mass spectrometry (GC−MS. The major components of the oil were camphor (29.24%, 1, 8−cineol (27.62%, yomogi alcohol (5.23%, and camphene (4.80%. The essential oil in same concentrations was assayed against (1−7 days old adults of insect species and percentage mortality was recorded after 24, 48, and 72 h exposure times. LC50 values were varied between 19.84 and 103.59 μL L-1 air, depending on insect species and exposure time. Callosobruchus maculatus was more susceptible than other species. These results suggested that A. haussknechtii oil might have potential as a control agent against C. maculatus, S. oryzae and T. castaneum.

  3. Anatomy and fructan distribution in vegetative organs of Dimerostemma vestitum (Asteraceae from the campos rupestres

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    Taiza M. Silva

    2015-06-01

    Full Text Available Among the compounds stored by plants, several functions are assigned to fructans, such as source of energy and protection against drought and extreme temperatures. In the present study we analyzed the anatomy and distribution of fructans in vegetative organs of Dimerostemma vestitum (Asteraceae, an endemic species from the Brazilian campos rupestres. D. vestitum has amphistomatic and pubescent leaves, with both glandular and non-glandular trichomes. In the basal aerial stem the medulla has two types of parenchyma, which differ from the apical portion. The xylopodium has mixed anatomical origin. Interestingly, although inulin-type fructans with high degree of polymerization were found in all analyzed organs except the leaves, the highest amount and maximum degree of polymerization were detected in the xylopodium. Inulin sphero-crystals were visualized under polarized light in the medulla and in the vascular tissues mainly in the central region of the xylopodium, which has abundant xylem parenchyma. Secretory structures accumulating several compounds but not inulin were identified within all the vegetative organs. The presence of these compounds, in addition to inulin, might be related to the strategies of plants to survive adverse conditions in a semi-arid region, affected seasonally by water restriction and frequently by fire.

  4. Biotechnological potential of endophytic actinomycetes associated with Asteraceae plants: isolation, biodiversity and bioactivities.

    Science.gov (United States)

    Tanvir, Rabia; Sajid, Imran; Hasnain, Shahida

    2014-04-01

    Endophytic actinomycetes from five Asteraceae plants were isolated and evaluated for their bioactivities. From Parthenium hysterophorus, Ageratum conyzoides, Sonchus oleraceus, Sonchus asper and Hieracium canadense, 42, 45, 90, 3, and 2 isolates, respectively, were obtained. Of the isolates, 86 (47.2 %) showed antimicrobial activity. Majority of the isolates were recovered from the roots (n = 127, 69.7 %). The dominant genus was Streptomyces (n = 96, 52.7 %), while Amycolatopsis, Pseudonocardia, Nocardia and Micromonospora were also recovered. Overall, 36 of the 86 isolates were significantly bioactivity while 18 (20.9 %) showed strong bioactivity. In total, 52.1 and 66.6 % showed potent cytotoxicity and antioxidant activities. The LC50 for 15 strains was <20 μg/ml. Compared to the ascorbate standard (EC50 0.34 μg/ml), all isolates gave impressive results with notable EC50 values of 0.65, 0.67, 0.74 and 0.79 μg/ml.

  5. Insecticide Activity of Ageratina jahnii and Ageratina pichinchensis (Asteraceae against Lutzomyia migonei (Diptera: Psychodidae

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    Lizzeth Torres

    2017-01-01

    Full Text Available Background: Insects are mostly pathogens transmitters, thus the necessity of finding effective bioinsecticides to combat them. In the present investigation, the insecticide activity of Ageratina jahnii and Ageratina pichinchensis (Asteraceae essential oils, methanol, and aqueous extracts was evaluated against Lutzomyia migonei (Diptera: Psychodidae females, Leishmania transmitters, a wide distributed parasitosis in Latin America. Materials and Methods: All extracts were prepared by maceration at room temperature, and essential oils were obtained by hydrodistillation process. Females of L. migonei were used in the bioassays using the adulticide test in pots. Results: Essential oils from both assayed plant species showed 100% of L. migonei mortality at 48 h of exposure at the concentration of 10 mg/ml. A. jahnii essential oil exhibited the following values, LD50 = 0.39 mg/ml, LD90 = 1.57 mg/ml, LD95 = 2.31 mg/ml, and LD99 = 4.80 mg/ml while for A. pichinchensis essential oil values were LD50 = 0.31 mg/ml, LD90 = 0.99 mg/ml, LD95 = 1.38 mg/ml, and LD99 = 2.55 mg/ml. Conclusion: Higher toxicity was observed with A. pichinchensis essential oil against L. migonei, comparing to A. jahnii oil. Two new plant species are being reported, showing bioactive properties against common tropical disease vectors such as L. migonei, hence, opening possibilities to a more environmental friendly control.

  6. Insecticide Activity of Ageratina jahnii and Ageratina pichinchensis (Asteraceae) against Lutzomyia migonei (Diptera: Psychodidae).

    Science.gov (United States)

    Torres, Lizzeth; Rojas, Janne; Rondón, Maritza; Morales, Antonio; Nieves, Elsa

    2017-01-01

    Insects are mostly pathogens transmitters, thus the necessity of finding effective bioinsecticides to combat them. In the present investigation, the insecticide activity of Ageratina jahnii and Ageratina pichinchensis (Asteraceae) essential oils, methanol, and aqueous extracts was evaluated against Lutzomyia migonei (Diptera: Psychodidae) females, Leishmania transmitters, a wide distributed parasitosis in Latin America. All extracts were prepared by maceration at room temperature, and essential oils were obtained by hydrodistillation process. Females of L. migonei were used in the bioassays using the adulticide test in pots. Essential oils from both assayed plant species showed 100% of L. migonei mortality at 48 h of exposure at the concentration of 10 mg/ml. A. jahnii essential oil exhibited the following values, LD50 = 0.39 mg/ml, LD90 = 1.57 mg/ml, LD95 = 2.31 mg/ml, and LD99 = 4.80 mg/ml while for A. pichinchensis essential oil values were LD50 = 0.31 mg/ml, LD90 = 0.99 mg/ml, LD95 = 1.38 mg/ml, and LD99 = 2.55 mg/ml. Higher toxicity was observed with A. pichinchensis essential oil against L. migonei, comparing to A. jahnii oil. Two new plant species are being reported, showing bioactive properties against common tropical disease vectors such as L. migonei, hence, opening possibilities to a more environmental friendly control.

  7. Analgesic and antiinflammatory activities of the ethyl acetate fraction of Bidens pilosa (Asteraceae).

    Science.gov (United States)

    Fotso, Aurélien Fotso; Longo, Frida; Djomeni, Paul Désiré Dzeufiet; Kouam, Siméon Fogue; Spiteller, Michael; Dongmo, Alain Bertrand; Savineau, J P

    2014-04-01

    Bidens pilosa is an Asteraceae widely used in traditional medicine for the treatment of various ailments including pain and inflammation. The present work was undertaken to assess the analgesic and antiinflammatory properties of the ethyl acetate fraction of methylene chloride/methanol (1:1) extract of leaves of Bidens pilosa at the gradual doses of 50, 100 and 200 mg/kg in mice and rats, respectively. The analgesic properties of Bidens pilosa were investigated using the acetic acid writhing, hot plate, capsaicin and formalin-induced pain models. This was followed by a study of the antiinflammatory properties using carrageenan, dextran, histamine and serotonin to induce acute inflammation in rat hind paw. The extract provided a significant (p antiinflammatory activity in all four models of acute inflammation. These results show that the ethyl acetate fraction of methylene chloride/methanol (1:1) of Bidens pilosa has both analgesic and antiinflammatory properties. The qualitative analysis of the fraction by the high-performance liquid chromatography (HPLC) fingerprint revealed the presence of two flavonoids, namely quercetin and iso-okanin, known to have antiinflammatory and antinociceptive properties, which could be responsible for the analgesic and antiinflammatory effects observed.

  8. Evolutionary history and phylogeography of Encelia farinosa (Asteraceae) from the Sonoran, Mojave, and Peninsular Deserts.

    Science.gov (United States)

    Fehlberg, Shannon D; Ranker, Tom A

    2009-02-01

    Pleistocene glaciations have had a profound influence on the genetic structure of plant species throughout the Northern Hemisphere because of range contractions, fragmentations, and expansions. Phylogeographic studies have contributed to our knowledge of this influence in several geographic regions of North America, however, very few phylogeographic studies have examined plant species in the Sonoran, Mojave, and Peninsular deserts. In this study, we used sequence data from the chloroplast DNA psbA-trnH intergenic spacer to obtain information on phylogeographic patterns among 310 individuals from 21 populations of Encelia farinosa ("brittlebush"; Asteraceae) across its range. We applied several population and spatial genetic analyses that allowed us to interpret our data with respect to Pleistocene climate change. These analyses indicate that E. farinosa displays patterns of genetic differentiation and geographic structuring consistent with postglacial range expansion. Populations of E. farinosa are characterized by distinct haplotype lineages significantly associated with geography. Centers of genetic diversity for the species occur in southwestern Arizona, the plains of Sonora, and Baja California Sur, all of which are putative sites of glacial refugia as predicted by analyses of macrofossil and pollen data. Nested clade analysis suggests that genetic structure in E. farinosa has been affected by past fragmentation followed by range expansion. Range expansion in several locations is further supported by significant departures from neutrality for values of Fu's F(S) and Tajima's D, and mismatch analyses.

  9. Anti-inflammatory intestinal activity of Arctium lappa L. (Asteraceae) in TNBS colitis model.

    Science.gov (United States)

    de Almeida, Ana Beatriz Albino; Sánchez-Hidalgo, Marina; Martín, Antonio Ramón; Luiz-Ferreira, Anderson; Trigo, José Roberto; Vilegas, Wagner; dos Santos, Lourdes Campaner; Souza-Brito, Alba Regina Monteiro; de la Lastra, Catalina Alarcón

    2013-03-07

    In Brazilian traditional medicine, Arctium lappa (Asteraceae), has been reported to relieve gastrointestinal symptoms. In the present study, we investigated the effects of the lactone sesquiterpene onopordopicrin enriched fraction (ONP fraction) from Arctium lappa in an experimental colitis model induced by 2,4,6 trinitrobenzene sulfonic acid and performed experiments to elucidate the underlying action mechanisms involved in that effect. ONP fraction (25 and 50 mg/kg/day) was orally administered 48, 24 and 1 h prior to the induction of colitis and 24 h after. The inflammatory response was assessed by gross appearance, myeloperoxidase (MPO) activity, tumor necrosis factor alpha (TNF-α) levels and a histological study of the lesions. We determined cyclooxygenase (COX)-1 and -2 protein expressions by western blotting and immunohistochemistry assays. TNBS group was characterized by increased colonic wall thickness, edema, diffuse inflammatory cell infiltration, increased MPO activity and TNF-α levels. On the contrary, ONP fraction (25 and 50 mg/kg) treatment significantly reduced the macroscopic inflammation scores (pArctium lappa exert marked protective effects in acute experimental colitis, confirming and justifying, at least in part, the popular use of this plant to treat gastrointestinal diseases. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  10. [Dengue vector control using ether fractions from two plants (Asteraceae) as larvicide].

    Science.gov (United States)

    Álvarez-Londoño, Juan C; Duarte-Gandica, Irene; Aguirre-Obando, Oscar A; Jiménez-Montoya, Jorge A

    2013-01-01

    Evaluating the larvicidal activity of two ether factions from Asteraceae (the aster, daisy or sunflower family, i.e. Heli opsisoppositifolia (L.) Druce (oxeye, sunflower-like) and Jaegeria hirta (Lag.) Less (weed-like)) on Aedes (Stegomyia) aegypti (L.) final third instar or initial fourth instar larvae near the town of Armenia in the Quindío Department in Colombia. H. oppositifolia and J. hirta plants were collected and submitted to phytochemical analysis. Ether fractions were prepared form both species to assess 11 concentrations for determining LC50, LC90 and LC95 lethal concentrations after 24 and 48 h. The LC50, LC90 and LC95 results were used to create a mathematical model for describing lethal population-concentration dynamics. Phytochemical analysis identified tannins, flavonoids, quinones, cardiac glycosides, sterols, lactones, terpenes, courmarins and alkaloids in H. oppositifolia and J. hirta. LC after 48 h regarding J. hirta (LC50 24, LC90 70 and LC95 93 ppm) was lower than those for H. oppositifolia (LC50 39, LC90 77 and LC95 94 ppm). A factorial ANOVA test confirmed this trend: 66 %, F=18.5 and pbioinsecticide for controlling A. Aegypti immature states.

  11. New synonyms and a new name in Asteraceae: Senecioneae from the southern African winter rainfall region

    Directory of Open Access Journals (Sweden)

    J. C. Manning

    2010-12-01

    Full Text Available A review of the genera Othonna and Senecio undertaken for the forthcoming Greater Cape plants 2: Namaqualand-southern Namib and western Karoo (Manning in prep. led to a re-examination of the taxonomic status of several species. This was facilitated by the recent availability of high-resolution digital images on the Aluka website (www.aluka.org of the Drege isotypes in the Paris Herbarium that formed the basis of many species described by De Candolle in his Prodromus systematis naturalis regni vegetabilis. These images made it possible to identify several names whose application had remained uncertain until now. Each case is briefly discussed, with citation of additional relevant herbarium specimens. The following species are reduced to synonomy: O. incisa Harv. is included in O. rosea Harv.; O. spektakelensis Compton and O. zeyheri Sond. ex Harv. are included in O. retrorsa DC.; S. maydae Merxm. is included in S. albopunctatus Bolus, which is now considered to include forms with radiate and discoid capitula; S. cakilefolius DC. is included in  O. arenarius Thunb.; S. pearsonii Hutch, is included in O. aspertdus DC.; S. parvifolius DC. is included in S. carroensis DC.; S. eriobasis DC. is included in S. erosus L.f.; and S. lobelioides DC. is included in S. flavus (Decne. Sch.Bip. The name S. panduratus (Thunb. Less, is identified as a synonym of S. erosus L.f. and plants that are currently know n under this name should be called S. robertiifolius DC. The confusion in the application o f the names O. perfoliata (L.f. Jacq. and O. filicaulis Jacq. is examined. O. perfoliata is lecto- typified against a specimen in the Linnaean Herbarium (LINN  w ith radiate capitula. The name O. filicaulis correctly applies to a radiate species and is treated as a synonym of O. perfoliata. The vegetatively similar taxon with disciform capitula that is currently known as O. filicaulis should be known as (  undulosa (DC. J.C.Manning  & Goldblatt, comb. nov. The

  12. New synonyms and a new name in Asteraceae: Senecioneae from the southern African winter rainfall region

    Directory of Open Access Journals (Sweden)

    J. C. Manning

    2010-12-01

    Full Text Available A review of the genera Othonna and Senecio undertaken for the forthcoming Greater Cape plants 2: Namaqualand-southern Namib and western Karoo (Manning in prep. led to a re-examination of the taxonomic status of several species. This was facilitated by the recent availability of high-resolution digital images on the Aluka website (www.aluka.org of the Drege isotypes in the Paris Herbarium that formed the basis of many species described by De Candolle in his Prodromus systematis naturalis regni vegetabilis. These images made it possible to identify several names whose application had remained uncertain until now. Each case is briefly discussed, with citation of additional relevant herbarium specimens. The following species are reduced to synonomy: O. incisa Harv. is included in O. rosea Harv.; O. spektakelensis Compton and O. zeyheri Sond. ex Harv. are included in O. retrorsa DC.; S. maydae Merxm. is included in S. albopunctatus Bolus, which is now considered to include forms with radiate and discoid capitula; S. cakilefolius DC. is included in  O. arenarius Thunb.; S. pearsonii Hutch, is included in O. aspertdus DC.; S. parvifolius DC. is included in S. carroensis DC.; S. eriobasis DC. is included in S. erosus L.f.; and S. lobelioides DC. is included in S. flavus (Decne. Sch.Bip. The name S. panduratus (Thunb. Less, is identified as a synonym of S. erosus L.f. and plants that are currently know n under this name should be called S. robertiifolius DC. The confusion in the application o f the names O. perfoliata (L.f. Jacq. and O. filicaulis Jacq. is examined. O. perfoliata is lecto- typified against a specimen in the Linnaean Herbarium (LINN  w ith radiate capitula. The name O. filicaulis correctly applies to a radiate species and is treated as a synonym of O. perfoliata. The vegetatively similar taxon with disciform capitula that is currently known as O. filicaulis should be known as (  undulosa (DC. J.C.Manning  & Goldblatt, comb. nov. The

  13. SDF-1, DC1/DC2, and Tumor Angiogenesis

    Science.gov (United States)

    2006-04-01

    However, the presence of functional immunogenic (mature) myeloid DCs is rare in human ovarian tumours35, breast tumours40,41, prostate cancer42 and...cyclooxygenase-2 ( COX2 )50–52. COX2 promotes prostaglandin E2 (PGE2) production in the tumour environment. PGE2 in turn suppresses DC differentiation and...Abundance of VEGF, IL-6, M-CSF, TGFβ, IL-10, COX2 , PGE2, gangliosides and other suppressive molecules versus negligible GM-CSF, IL-4, B7-H1 A recently

  14. A Feedback Passivation Design for DC Microgrid and Its DC/DC Converters

    Directory of Open Access Journals (Sweden)

    Feifan Ji

    2016-12-01

    Full Text Available There are difficulties in analyzing the stability of microgrids since they are located on various network structures. However, considering that the network often consists of passive elements, the passivity theory is applied in this paper to solve the above-mentioned problem. It has been formerly shown that when the network is weakly strictly positive real (WSPR, the DC microgrid is stable if all interfaces between the microgrid and converters are made to be passive, which is called interface passivity. Then, the feedback passivation method is proposed for the controller design of various DC–DC converters to achieve the interface passivity. The interface passivity is different from the passivity of closed-loop systems on which the passivity based control (PBC concentrates. The feedback passivation design is detailed for typical buck converters and boost converters in terms of conditions that the controller parameters should satisfy. The theoretical results are verified by a hardware-in-loop real-time labotray (RTLab simulation of a DC microgrid with four generators.

  15. Efficient plant regeneration protocol through callus for Saussurea obvallata (DC.) Edgew. (Asteraceae): effect of explant type, age and plant growth regulators.

    Science.gov (United States)

    Dhar, Uppeandra; Joshi, Mitali

    2005-06-01

    A callus induction and in vitro plantlet regeneration system for the endangered state flower of Uttaranchal (Saussurea obvallata) was optimized by studying the influence of explant type (root, hypocotyl, cotyledon and leaf), age and different concentrations of plant growth regulators. Explants from 10 to 15-day-old seedlings showed maximum callus induction. Callus formation and shoot differentiation was initiated on Murashige-Skoog (MS) medium containing 6-benzyladenine (BA) and alpha-naphthalene acetic acid (NAA) in all explant types. The best results were obtained using leaf explants: 100% callusing was achieved in MS medium supplemented with 2.5 microM BA and 1.0 microM NAA, and 100% differentiation along with a multiplication rate of 12 shoots per explant with a combination of 5.0 microM BA and 1.0 microM NAA. However, the results reflected the existence of high inter-explant variability in response to growth regulators. In vitro rooting of shoots was achieved at an efficiency of 100% in one-half strength MS medium supplemented with 2.5 microM indole-3-butyric acid. Application of this protocol has potential for mass multiplication of the target species in a limited time period.

  16. Estudo fitoquímico e avaliação da atividade antiinflamatória Lychnophora passerina (Mart ex DC) Gardn (Asteraceae)

    OpenAIRE

    Oliveira, Patricia Capelari de

    2010-01-01

    O homem mantém relações de subsistência com a natureza desde tempos primordiais. Nesse contexto, a natureza está relacionada aos processos de saúde e doença e serve como fonte de medicamentos para tratamento de enfermidades. As plantas medicinais ocupam lugar de destaque no fornecimento de drogas e a medicina tradicional, praticada por diversas sociedades em todo o mundo, aparece como ferramenta crucial na busca por novas drogas de origem vegetal, à medida que fornece o conhecimento associado...

  17. DC Voltage Droop Control Implementation in the AC/DC Power Flow Algorithm: Combinational Approach

    DEFF Research Database (Denmark)

    Akhter, F.; Macpherson, D.E.; Harrison, G.P.

    2015-01-01

    In this paper, a combinational AC/DC power flow approach is proposed for the solution of the combined AC/DC network. The unified power flow approach is extended to include DC voltage droop control. In the VSC based MTDC grids, DC droop control is regarded as more advantageous in terms...... of operational flexibility, as more than one VSC station controls the DC link voltage of the MTDC system. This model enables the study of the effects of DC droop control on the power flows of the combined AC/DC system for steady state studies after VSC station outages or transient conditions without needing...... to use its complete dynamic model. Further, the proposed approach can be extended to include multiple AC and DC grids for combined AC/DC power flow analysis. The algorithm is implemented by modifying the MATPOWER based MATACDC program and the results shows that the algorithm works efficiently....

  18. Energy Factor and Mathematical Modeling for Power DC/DC Converters

    Institute of Scientific and Technical Information of China (English)

    Fang Lin LUO; Hong YE

    2004-01-01

    Mathematical modelling for power DC/DC converters is a historical problem accompanying DC/DC conversion technology since 1940's. The traditional mathematical modelling is not available for complex structure converters since the differential equation order increases very high. We have to search other way to establish mathematical modelling for power DC/DC converters. We have theoretically defined a new concept - Energy Factor (EF) in this paper and researched the relations between EF and the mathematical modelling for power DC/DC converters. EF is a new concept in power DC/DC conversion technology, which thoroughly differs from the traditional concepts such as power factor (PF), power transfer efficiency (η), total harmonic distortion (THD) and ripple factor (RF). EF and the subsequential EFv (and EFvD ) can illustrate the system stability, reference response and interference recovery. This investigation is very helpful for system design and DC/DC converters characteristics foreseeing. Two DC/DC converters: Buck converter and Super-Lift Luo-Converter as the samples are analysed in this paper to demonstrate the applications of EF, EFv (and EFvD), PE,SE, VE (and VED ), time constant τ and damping time constant τd .

  19. Silicon carbide DC-DC multilevel Cuk converter

    Science.gov (United States)

    Almalaq, Yasser; Alateeq, Ayoob; Matin, Mohammad

    2016-09-01

    In this paper, DC-DC multilevel cuk converter using silicon carbide (SiC) Components is presented. Cuk converter gives output voltage with negative polarity. This topology is useful for applications require high gain with limitation on duty cycle. The gain of the design can be enhanced by increasing the number of multiplier level (N). This relation between the gain and the number of levels is the major advantage of this multilevel cuk converter. In the proposed cuk converter, a single SiC MOSFET, 2N-1 SiC schottky diodes, 2N capacitors, 2 inductors, and single input voltage are used to supply a load with negative polarity. 300V input voltage, 50KHz switching frequency, and 75% duty cycle are the main parameters used in the design. The output parameters are 3KW power and -5.7 KV voltage. Because this design can be used in applications which temperature plays a critical role, the relation between increasing temperature and output voltage and power are tested. The design is simulated using LTspice software and the results are discussed.

  20. DC Magnetics Measurement System Design

    Science.gov (United States)

    Mastny, Timothy

    2012-01-01

    This report will detail the updates to the magnetics measurement system design and testing procedures that are required for performing static (DC) magnetics testing of future flight hardware. An older magnetics testing system had to be integrated with new procedures and hardware to meet the demands of future testing programs and accommodate an upcoming magnetics tests. The next test will be for the Geostationary Operational Environmental Satellite R-Series (GOES-R), which will verify that the SAFT Battery component meets its specifications for magnetic cleanliness. The satellite is scheduled to launch in 2015 with magnetics testing to be completed on the battery in November 2012.

  1. Linking DC together with TRSL

    DEFF Research Database (Denmark)

    Haxthausen, Anne; Yong, Xia

    1999-01-01

    of constraints on the durations of states of the system, i.e. at a high level of abstraction.However, as a state-based logic, it lacks the ability to specifysequential programs and communicating concurrent processes at a concrete level. The Timed RAISE Specification Language (TRSL) [XG99] has this ability...... (parts of) the history of the observables of the system,and then define a satisfaction relation in terms of behaviours. DC has previously been linked together with subsets of other event-based process algebra languages, but using another approach:the event-based languages were given a denotational...

  2. Power factor controller used as DC-DC converter for photovoltaic sources

    Energy Technology Data Exchange (ETDEWEB)

    Mukerjee, A.K.; Dasgupta, Nivedita [Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India)

    2008-06-15

    An active power factor controller (PFC) integrated circuit, normally used in AC circuits, has been used for DC-to-DC boost conversion with a stable output voltage for a variable DC input voltage as obtained from photovoltaic (PV) sources. The circuit described here uses a power factor controller MC 34262 to give approximately 400 V{sub DC} output for an input variation from 90 to 280 V{sub DC}. The maximum efficiency achieved was 98% at 450 W. Comparisons between AC and DC operations have been made. (author)

  3. Chaos analysis and chaotic EMI suppression of DC-DC converters

    CERN Document Server

    Zhang, Bo

    2014-01-01

    Introduces chaos theory, its analytical methods and the means to apply chaos to the switching power supply design DC-DC converters are typical switching systems which have plenty of nonlinear behaviors, such as bifurcation and chaos. The nonlinear behaviors of DC-DC converters have been studied heavily over the past 20 years, yet researchers are still unsure of the practical application of bifurcations and chaos in switching converters. The electromagnetic interference (EMI), which resulted from the high rates of changes of voltage and current, has become a major design criterion in DC-DC co

  4. Elimination of output voltage oscillations in DC-DC converter using PWM with PI controller

    Directory of Open Access Journals (Sweden)

    Sreenivasappa Veeranna Bhupasandra

    2010-01-01

    Full Text Available In this paper the SIMULINK model of a PWM controlled DC-DC converter is modeled using switching function concept to control the speed of the DC motor. The presence of the voltage oscillation cycles due to higher switching frequency in the DC-DC converter is identified. The effect of these oscillations on the output voltage of the converter, Armature current, Developed torque and Speed of the DC motor is analyzed. In order to minimize the oscillation cycles the PI controller is proposed in the PWM controller.

  5. Hierarchical Velocity Control Based on Differential Flatness for a DC/DC Buck Converter-DC Motor System

    Directory of Open Access Journals (Sweden)

    R. Silva-Ortigoza

    2014-01-01

    Full Text Available This paper presents a hierarchical controller that carries out the angular velocity trajectory tracking task for a DC motor driven by a DC/DC Buck converter. The high level control is related to the DC motor and the low level control is dedicated to the DC/DC Buck converter; both controls are designed via differential flatness. The high level control provides a desired voltage profile for the DC motor to achieve the tracking of a desired angular velocity trajectory. Then, a low level control is designed to ensure that the output voltage of the DC/DC Buck converter tracks the voltage profile imposed by the high level control. In order to experimentally verify the hierarchical controller performance, a DS1104 electronic board from dSPACE and Matlab-Simulink are used. The switched implementation of the hierarchical average controller is accomplished by means of pulse width modulation. Experimental results of the hierarchical controller for the velocity trajectory tracking task show good performance and robustness against the uncertainties associated with different system parameters.

  6. Self-organizing maps of molecular descriptors for sesquiterpene lactones and their application to the chemotaxonomy of the Asteraceae family.

    Science.gov (United States)

    Scotti, Marcus T; Emerenciano, Vicente; Ferreira, Marcelo J P; Scotti, Luciana; Stefani, Ricardo; da Silva, Marcelo S; Mendonça Junior, Francisco Jaime B

    2012-04-20

    The Asteraceae, one of the largest families among angiosperms, is chemically characterised by the production of sesquiterpene lactones (SLs). A total of 1,111 SLs, which were extracted from 658 species, 161 genera, 63 subtribes and 15 tribes of Asteraceae, were represented and registered in two dimensions in the SISTEMATX, an in-house software system, and were associated with their botanical sources. The respective 11 block of descriptors: Constitutional, Functional groups, BCUT, Atom-centred, 2D autocorrelations, Topological, Geometrical, RDF, 3D-MoRSE, GETAWAY and WHIM were used as input data to separate the botanical occurrences through self-organising maps. Maps that were generated with each descriptor divided the Asteraceae tribes, with total index values between 66.7% and 83.6%. The analysis of the results shows evident similarities among the Heliantheae, Helenieae and Eupatorieae tribes as well as between the Anthemideae and Inuleae tribes. Those observations are in agreement with systematic classifications that were proposed by Bremer, which use mainly morphological and molecular data, therefore chemical markers partially corroborate with these classifications. The results demonstrate that the atom-centred and RDF descriptors can be used as a tool for taxonomic classification in low hierarchical levels, such as tribes. Descriptors obtained through fragments or by the two-dimensional representation of the SL structures were sufficient to obtain significant results, and better results were not achieved by using descriptors derived from three-dimensional representations of SLs. Such models based on physico-chemical properties can project new design SLs, similar structures from literature or even unreported structures in two-dimensional chemical space. Therefore, the generated SOMs can predict the most probable tribe where a biologically active molecule can be found according Bremer classification.

  7. Novel anthraquinone derivatives produced by Phoma sorghina, an endophyte found in association with the medicinal plant Tithonia diversifolia (Asteraceae)

    Energy Technology Data Exchange (ETDEWEB)

    Borges, Warley de Souza; Pupo, Monica Tallarico [Sao Paulo Univ., Ribeirao Preto, SP (Brazil). Faculdade de Ciencias Farmaceuticas]. E-mail: mtpupo@fcfrp.usp.br

    2006-09-15

    Three known anthraquinones (1,7-dihydroxy-3-methyl-9,10-anthraquinone, 1,6-dihydroxy- 3-methyl-9,10-anthraquinone and 1-hydroxy-3-methyl-9,10-anthraquinone), one new anthraquinone (1,7-dihydroxy-3-hydroxymethyl-9,10-anthraquinone), and two new hexahydro anthraquinone derivatives, dendryols E and F, were isolated from the culture of the endophytic fungus Phoma sorghina, found in association with Tithonia diversifolia (Asteraceae). Their structures were identified on the basis of spectroscopic data, mainly 1D and 2D NMR. (author)

  8. DC operating points of transistor circuits

    Science.gov (United States)

    Trajkovic, Ljiljana

    Finding a circuit's dc operating points is an essential step in its design and involves solving systems of nonlinear algebraic equations. Of particular research and practical interests are dc analysis and simulation of electronic circuits consisting of bipolar junction and field-effect transistors (BJTs and FETs), which are building blocks of modern electronic circuits. In this paper, we survey main theoretical results related to dc operating points of transistor circuits and discuss numerical methods for their calculation.

  9. Control of Parallel DC/DC Converters in DC Microgrid%直流微网中平行DC/DC变换器的控制

    Institute of Scientific and Technical Information of China (English)

    叶友泉; 杨冠鲁

    2016-01-01

    提出以多墙体光伏为研究对象的光伏直流微网系统。将在逆变器并联控制中广泛使用的下垂控制策略应用到平行DC/DC变换器的控制中,与电压、电流环构成三闭环控制,从而抑制平行DC/DC变换器之间的环流。通过Simulink 仿真分析,该方法能够实现直流母线电压的稳定及有效抑制各平行DC/DC变换器之间的环流。最后,在实验室搭建实验平台,验证该控制策略的可行性。%This article proposes a photovoltaic ( PV) DC microgrid system which employs multi-wall PV. In the DC microgrid, the droop control strategy widely used in parallel control of inverter is adopted for the control of parallel DC/DC converters, forming a triple-loop control together with voltage and current loops, which restrains the loop current between parallel DC/DC converters. Simulink simulation shows that, stable DC bus voltage and effective control over the loop current among parallel DC / DC converters can be achieved by this way. In the end, an experimental platform is built in the lab to verify the feasibility of this control strategy.

  10. How Much DC Power is Necessary

    Science.gov (United States)

    2010-04-01

    must transform essentially all of the available AC power to DC, including all of the power for the ship propulsion drive. This approach by the...in Fig. 1 convert the AC source power to DC and energize the associated DC busses. At the power levels anticipated, i.e., for ship propulsion load...for a ship propulsion application. We begin by assuming that the variable frequency power electronics associated with the rotor will only deliver

  11. Energy Evaluation for DC/DC Converters in DC-Based Wind Farms

    Energy Technology Data Exchange (ETDEWEB)

    Max, Lena

    2007-02-15

    In this thesis the suitability of three topologies for DC/DC converters in a DC wind farm grid is investigated from an energy efficiency and energy production cost point of view. The three selected topologies are the fullbridge converter, the single active bridge converter and the series parallel resonant converter. The losses are calculated for all three topologies as a function of the wind speed considering the losses in the semiconductor components and in the transformer. To obtain the average losses, the losses for each converter are integrated over the wind distribution for different average wind speeds. It is found that the resonant converter has the lowest losses of the three types for the DC wind farm application with power losses of about 2.0 - 2.5 % of the input power and the fullbridge converter has slightly higher losses with 2.3 - 3.5 % losses depending on the position in the wind turbine grid. The single active bridge converter has considerably higher losses than the other two topologies with 3.5 - 5.0 % losses. It is shown that the variable operating conditions create problems for all three converters, and as mentioned the single active bridge converter is most affected by the wide range of operation conditions. When comparing the resonant converter and the fullbridge converter, the fullbridge converter has a smaller transformer as well as lower peak current and peak voltage, but also a higher number of diode modules in the output bridge. Comparing the contribution to the energy production cost for the converters, the topology with the lowest contribution varies between the positions in the wind turbine grid. For some positions, the cost of the higher losses for the fullbridge converter are compensated by lower investment cost for the fullbridge converter compared to the resonant converter. Considering the resonant capacitor, the higher peak voltage and the variable frequency control for the resonant converter, the fullbridge converter is here found

  12. A taxonomic revision of the small Cape genus Steirodiscus (Asteraceae: Senecioneae

    Directory of Open Access Journals (Sweden)

    J. C. Manning

    2013-01-01

    Full Text Available The genus Steirodiscus Less. is revised, with full descriptions, nomenclature, illustrations and distribution data. Five species are recognised in two sections: sect. Steirodiscus with free involucral bracts and sect. Psilothonna with bracts connate into a smooth cup. S. linearilobus DC. is established as an earlier name for S. schlechteri Bolus, which is relegated to synonomy.

  13. Zero-voltage switching technique in dc/dc converters

    Science.gov (United States)

    Liu, Kwang-Hwa; Lee, Fred C. Y.

    1990-07-01

    A novel resonant switch operating under the principle of zero-voltage switching is presented. In contrast to the zero-current switching, this technique eliminates the switching loss and dv/dt noise due to the discharging of MOSFET junction capacitances and the reverse recovery of diodes, and enables the converters to operate at high frequencies. A dc analysis of the converter is carried out. The duality relationship between the zero-current switching technique and the zero-voltage switching technique is derived. The two techniques are compared using an example showing the duality between a current-mode quasi-resonant Buck converter and a voltage-mode quasi-resonant boost converter. A 5-MHz 50 V to 5 V flyback converter employing the zero-voltage switching technique has been implemented. The circuit contains the smallest number of components possible, and yet maintains high efficiency at high switching frequency.

  14. SIMPLIFIED APPROACHES FOR CONTROLLING DC-DC POWER CONVERTERS

    Directory of Open Access Journals (Sweden)

    M. M. ABDEL AZIZ

    2012-02-01

    Full Text Available This paper represents the design procedures of different compensation schemes for voltage mode controlled (VMC dc–dc switching converters. Proportional integral derivative (PID controllers, Fuzzy logic controllers (FLC, parallel combination of PID and FLC, and FLC tuned by PI controller have been investigated. MATLAB software is used to depict the buck converter performance with each compensator type when it is electrically simulated, and analytically modeled using its equivalent transfer function (TF. The comparative study Resultsemphasize that FLC tuned by PI controller is superior to the other control strategies because of fast transient response, minimum steady state error and good disturbance rejection under various variations of the operating conditions. Hence, it achieves the most tightly output voltage regulation.

  15. Teaching about operation of brushless DC motors

    OpenAIRE

    Čufar, Aleksandra

    2013-01-01

    Brush DC motor is being replaced by brushless DC motors on every area of application. My diploma thesis is a presentation of brushless DC motor, how it works and its application. Within first part we describe various electric motors and their application. There are several types of electric motors division. Last to be added is a brushless motor. Within second part of thesis we look into a brushless DC motor, how it works, its application and control. In the third part of thesis we construct a...

  16. The good routing of a non-insulated DC/DC converter; Bien router un convertisseur DC/DC non-isole

    Energy Technology Data Exchange (ETDEWEB)

    Lenoir, E.

    2001-03-01

    DC to DC converters are important sources of magnetic and electric fields with frequencies that can exceed 100 MHz. Thus, their positioning on a circuit board is of prime importance to minimize the magnetic and capacitive couplings with other parts and components of the circuit. This article summarizes the important rules to follow for a good routing of non-insulated switching DC/DC converters: taking the ohmic voltage drops into consideration, managing the MOSFET commutation, limiting the current loop disturbances, correct routing of power tracks. (J.S.)

  17. Drilling history core hole DC-8

    Energy Technology Data Exchange (ETDEWEB)

    1978-10-01

    Core hole DC-8 was completed in August, 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scission, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Scisson, Inc. furnished the engineering, daily supervision of the core drilling activities, and geologic core logging for hole DC-8. Core hole DC-8 is located on the Hanford Site near the Wye Barricade and 50 feet northwest of rotary hole DC-7. The Hanford Site vation coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 mean sea level. The purpose of core hole DC-8 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection, and to provide a borehole for hydrologic testing and cross-hole seismic shear and pressure wave velocity studies with rotary hole DC-7. The total depth of core hole DC-8 was 4100.5 feet. Core recovery exceeded 97 percent of the total footage cored.

  18. DC-SIGN:Binding receptor for HCV?

    Institute of Scientific and Technical Information of China (English)

    Zhi-Hua Feng; Quan-Chu Wang; Qing-He Nie; Zhan-Sheng Jia; Yong-Xin Zhou

    2004-01-01

    DC-SIGN, a dendritic Cell-specific adhesion receptor and a type Ⅱ transmembrane mannose-binding C-type lectin, is very important in the function of DC, both in mediating naive T cell interactions through ICAM-3 and as a rolling receptor that mediates the DC-specific ICAM-2-dependent migration processes. It can be used by viral and bacterial pathogens including Human Immunodeficiency Virus (HIV), HCV, Ebola Virus, CMV and Mycobacterium tuberculosis to facilitate infection. Both DC-SIGN and DC-SIGNR can act either in cis,by concentrating virus on target cells, or in trans, by transmission of bound virus to a target cell expressing appropropriate entry receptors. Recent work showed that DC-SIGN are highaffinity binding receptors for HCV. Besides playing a role in entry into DC, HCV E2 interaction with DC-SIGN might also be detrimental for the interaction of DC with T cells during antigen presentation. The clinical strategies that target DCSIGN may be successful in restricting HCV dissemination and pathogenesis as well as directing the migration of DCs to manipulate appropriate immune responses in autoimmunity and tumorigenic situations.

  19. Ficus sur (Moraceae and Gymnanthemum coloratum (Asteraceae: Vernonieae – first distribution records for Namibia

    Directory of Open Access Journals (Sweden)

    Wessel Swanepoel

    2015-03-01

    Full Text Available Background: The distribution of Ficus sur includes most of tropical Africa, but whilst this species was suspected to occur in Namibia, this has not been verified. Gymnanthemum coloratum is a tropical African savannah shrub or tree that has been recorded for Botswana, Swaziland and South Africa, but which has not previously been recorded for Namibia.Objectives: To formally document the first records of two plant species from Namibia and provide habitat details of the localities from which these species were recorded.Method: The data presented have resulted from botanical expeditions to the poorly known Baynes Mountains in the Koakoveld region of Namibia. Specimens of the two species in the National Herbarium, Pretoria were examined to verify the identity in the case of G. coloratum, and to document additional records in Namibia for F. sur.Results: Ficus sur was recorded from two localities, and a third locality based on a specimen in the National Herbarium, Pretoria, was verified. Gymnanthemum coloratum, a member of the Asteraceae, was recorded from a single locality.Conclusion: The fact that F. sur was collected at more than one location in the Kaokoveld suggests that it is probably more widespread in suitable microhabitats. Ficus sur also occurs further north in Angola, suggesting that the Kaokoveld plants represent a cross-border outlier of the much more widespread Angolan population. Gymnanthemum coloratum was only recorded from the one locality in the Koakoveld. The species also occurs in Angola, which suggests that the Kaokoveld plant represents a cross-border outlier of the population in that country.

  20. Origins and recent radiation of Brazilian Eupatorieae (Asteraceae) in the eastern Cerrado and Atlantic Forest.

    Science.gov (United States)

    Rivera, Vanessa Lopes; Panero, Jose L; Schilling, Edward E; Crozier, Bonnie S; Moraes, Marta Dias

    2016-04-01

    The remarkable diversity of Eupatorieae in the Brazilian flora has received little study, despite the tribe's very high levels of endemism and importance in the threatened Cerrado and the Atlantic Forest biodiversity hotspots. Eupatorieae are one of the largest tribes in Asteraceae with 14 of 19 recognized subtribes occurring in Brazil. We constructed the largest phylogeny of Brazilian Eupatorieae to date that sampled the nrITS and ETS, chloroplast ndhI and ndhF genes, and the ndhI-ndhG intergenic spacer for 183 species representing 77 of the 85 Brazilian genera of the tribe. Maximum likelihood and Bayesian phylogenetic analyses showed that these species are not collectively monophyletic, so their distribution reflects multiple introductions into Brazil. A novel clade was found that includes 75% of the genera endemic to Brazil (Cerrado-Atlantic Forest Eupatorieae, "CAFE" clade). This radiation of at least 247 species concentrated in the Cerrado and Atlantic Forest biomes of central eastern Brazil is <7 my old and exhibits several ecologically diverse life forms. Eight subtribes of Brazilian Eupatorieae (Ageratinae, Alomiinae, Ayapaninae, Critoniinae, Disynaphiinae, Eupatoriinae, Gyptidinae and Hebecliniinae) and 16 genera (Ageratum, Agrianthus, Austroeupatorium, Bejaranoa, Chromolaena, Critonia, Disynaphia, Grazielia, Hatschbachiella, Heterocondylus, Koanophyllon, Lasiolaena, Neocabreria, Praxelis, Stylotrichium, and Symphyopappus) were found to be polyphyletic. We attribute incongruities between the molecular phylogenetic results and the current classification of the tribe mostly to convergent evolution of morphological characters traditionally used in the classification of the tribe. We used these phylogenetic results to suggest changes to the classification of some subtribes and genera of Eupatorieae that occur in Brazil. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Evaluation of Selected Ornamental Asteraceae as a Pollen Source for Urban Bees

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    Wróblewska Anna

    2016-12-01

    Full Text Available Offering more floral resources for urban bees can be achieved by growing ornamental bee plants. The aim of the present study was to evaluate selected Asteraceae (Calendula officinalis ‘Persimmon Beauty’ and ‘Santana’, Centaurea macrocephala, Cosmos sulphureus, Dahlia pinnata, Tagetes patula, Tithonia rotundifolia, and Zinnia elegans as pollen sources for pollinators. Under urban conditions in Lublin, SE Poland, the investigated plants flowered from late June to the end of October. The mass of pollen produced in florets and capitula was found to be species-related. The highest pollen amounts per 10 florets (10.1 mg as well as per capitulum (249.7 mg were found for C. macrocephala. The mass of pollen yielded by a single plant depended on both the pollen mass delivered per disk florets and the proportion of disk florets in capitulum, and the flowering abundance of the plants. A single plant of D. pinnata and a single plant of T. rotundifolia each produced the largest pollen mass. Mean pollen yield per 1m2 of a plot ranged from 6.2 g (Z. elegans to 60.7 g (D. pinnata. Pollen grains are tricolporate, with echinate exine, medium or small in size. They can be categorised as oblatespherical, spherical, and prolatespherical. The principal visitors to C. macrocephala, C. sulphureus, and C. officinalis were honey bees, whereas bumble bees dominated on T. rotundifolia and D. pinnata. A magnet plant for butterflies was Z. elegans. Among the investigated species, D. pinnata, C. macrocephala, and T. rotundifolia were found to be the most valuable sources of pollen flow for managed and wild bees.

  2. Sesquiterpene lactones from the Yugoslavian wild growing plant families Asteraceae and Apiaceae (REVIEW

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    MILUTIN STEFANOVIC

    1999-08-01

    Full Text Available 1. Introduction 2. Results 3. Asteraceae 3.1. Genus Artemisia L. 3.1.1. Artemisia annua L. 3.1.2. Artemisia vulgaris L. 3.1.3. Artemisia absinthium L. (warmwood 3.1.4. Artemisia scoparia W. et K. 3.1.5. Artemisia camprestris L. 3.2. Genus Ambrosia L. 3.2.1. Ambrosia artemisiifolia L. (the common rag weed 3.3. Genus Tanacetum L. (syn. Chrysanthemum L. 3.3.1. Tanacetum parthenium L. (feverfew 3.3.2. Tanacetum serotinum L. 3.3.3. Tanacetum vulgare L. (tansy 3.3.4. Tanacetum macrophyllum Willd. 3.3.5. Tanacetum corymbosum L. 3.4. Genus Telekia Baumg. 3.4.1. Telekia speciosa (Schreb. Baumg. 3.5. Genus Inula L. 3.5.1. Inula helenium L. 3.5.2. Inula spiraeifolia L. 3.6. Genus Eupatorium L. 3.6.1. Eupatorium cannabinum L. 3.7. Genus Achillea L. 3.7.1. Achillea abrotanoides Vis. 3.7.2. Achillea millefolium subsp. pannonica 3.7.3. Achillea crithmifolia W. et K. 3.7.4. Achillea clypeolata Sibth. et Sm. 3.7.5. Achillea serbica Nyman 3.7.6. Achillea depressa Janka 3.8. Genus Anthemis L. 3.8.1. Anthemis carpatica Willd. 3.8.2. Anthemis cretica L. subsp. cretica 3.9. Genus Centaurea L. 3.9.1. Centaurea derventana Vis. et Panc. 3.9.2. Centaurea kosaninii Hayek 3.9.3. Centaurea solstitialis L. 4. Apiaceae 4.1. Genus Laserpitium L. 4.1.1. Laserpitium siler L. 4.1.2. Laserpitium marginatum L. 4.1.3. Laserpitium latifolium L. 4.1.4. Laserpitium alpinum W. K. 4.2. Genus Angelica L. 4.2.1. Angelica silvestris L. 4.3. Genus Peucedanum L. 4.3.1. Peucedanum austriacum (Jacq. Koch

  3. Genetic and ecotypic differentiation in a Californian plant polyploid complex (Grindelia, Asteraceae.

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    Abigail J Moore

    Full Text Available Studies of ecotypic differentiation in the California Floristic Province have contributed greatly to plant evolutionary biology since the pioneering work of Clausen, Keck, and Hiesey. The extent of gene flow and genetic differentiation across interfertile ecotypes that span major habitats in the California Floristic Province is understudied, however, and is important for understanding the prospects for local adaptation to evolve or persist in the face of potential gene flow across populations in different ecological settings. We used microsatellite data to examine local differentiation in one of these lineages, the Pacific Coast polyploid complex of the plant genus Grindelia (Asteraceae. We examined 439 individuals in 10 different populations. The plants grouped broadly into a coastal and an inland set of populations. The coastal group contained plants from salt marshes and coastal bluffs, as well as a population growing in a serpentine grassland close to the coast, while the inland group contained grassland plants. No evidence for hybridization was found at the single location where adjacent populations of the two groups were sampled. In addition to differentiation along ecotypic lines, there was also a strong signal of local differentiation, with the plants grouping strongly by population. The strength of local differentiation is consistent with the extensive morphological variation observed across populations and the history of taxonomic confusion in the group. The Pacific Clade of Grindelia and other young Californian plant groups warrant additional analysis of evolutionary divergence along the steep coast-to-inland climatic gradient, which has been associated with local adaptation and ecotype formation since the classic studies of Clausen, Keck, and Hiesey.

  4. Genetic and ecotypic differentiation in a Californian plant polyploid complex (Grindelia, Asteraceae).

    Science.gov (United States)

    Moore, Abigail J; Moore, William L; Baldwin, Bruce G

    2014-01-01

    Studies of ecotypic differentiation in the California Floristic Province have contributed greatly to plant evolutionary biology since the pioneering work of Clausen, Keck, and Hiesey. The extent of gene flow and genetic differentiation across interfertile ecotypes that span major habitats in the California Floristic Province is understudied, however, and is important for understanding the prospects for local adaptation to evolve or persist in the face of potential gene flow across populations in different ecological settings. We used microsatellite data to examine local differentiation in one of these lineages, the Pacific Coast polyploid complex of the plant genus Grindelia (Asteraceae). We examined 439 individuals in 10 different populations. The plants grouped broadly into a coastal and an inland set of populations. The coastal group contained plants from salt marshes and coastal bluffs, as well as a population growing in a serpentine grassland close to the coast, while the inland group contained grassland plants. No evidence for hybridization was found at the single location where adjacent populations of the two groups were sampled. In addition to differentiation along ecotypic lines, there was also a strong signal of local differentiation, with the plants grouping strongly by population. The strength of local differentiation is consistent with the extensive morphological variation observed across populations and the history of taxonomic confusion in the group. The Pacific Clade of Grindelia and other young Californian plant groups warrant additional analysis of evolutionary divergence along the steep coast-to-inland climatic gradient, which has been associated with local adaptation and ecotype formation since the classic studies of Clausen, Keck, and Hiesey.

  5. A volatolomic approach for studying plant variability: the case of selected Helichrysum species (Asteraceae).

    Science.gov (United States)

    Giuliani, Claudia; Lazzaro, Lorenzo; Calamassi, Roberto; Calamai, Luca; Romoli, Riccardo; Fico, Gelsomina; Foggi, Bruno; Mariotti Lippi, Marta

    2016-10-01

    The species of Helichrysum sect. Stoechadina (Asteraceae) are well-known for their secondary metabolite content and the characteristic aromatic bouquets. In the wild, populations exhibit a wide phenotypic plasticity which makes critical the circumscription of species and infraspecific ranks. Previous investigations on Helichrysum italicum complex focused on a possible phytochemical typification based on hydrodistilled essential oils. Aims of this paper are three-fold: (i) characterizing the volatile profiles of different populations, testing (ii) how these profiles vary across populations and (iii) how the phytochemical diversity may contribute in solving taxonomic problems. Nine selected Helichrysum populations, included within the H. italicum complex, Helichrysum litoreum and Helichrysum stoechas, were investigated. H. stoechas was chosen as outgroup for validating the method. After collection in the wild, plants were cultivated in standard growing conditions for over one year. Annual leafy shoots were screened in the post-blooming period for the emissions of volatile organic compounds (VOCs) by means of headspace solid phase microextraction coupled with gas-chromatography and mass spectrometry (HS-SPME-GC/MS). The VOC composition analysis revealed the production of overall 386 different compounds, with terpenes being the most represented compound class. Statistical data processing allowed the identification of the indicator compounds that differentiate the single populations, revealing the influence of the geographical provenance area in determining the volatile profiles. These results suggested the potential use of VOCs as valuable diacritical characters in discriminating the Helichrysum populations. In addition, the cross-validation analysis hinted the potentiality of this volatolomic study in the discrimination of the Helichrysum species and subspecies, highlighting a general congruence with the current taxonomic treatment of the genus. The consistency

  6. Clonal variation in floral stage timing in the common dandelion Taraxacum officinale (Asteraceae).

    Science.gov (United States)

    Collier, Matthew H; Rogstad, Steven H

    2004-11-01

    We investigated the hypothesis that dandelion clones (Taraxacum officinale Weber, sensu lato; Asteraceae) differ in their floral stage timing characteristics under a constant set of environmental conditions. To test this hypothesis, plants representing nine different dandelion clones (identified by DNA fingerprinting) were grown in groups of five (N = 45) in a growth chamber for a period of 8 mo, with chamber settings similar to environmental conditions at peak dandelion flowering time for their population sites. Five flowering phenology parameters were monitored daily for a total of 301 buds developing during this time: (1) time to bud; (2) time to full opening and inflorescence maturation (i.e., first anthesis); (3) time to re-closure of an inflorescence; (4) time to fruit (full re-opening of the inflorescence); and (5) total flowering time. Scape length at the appearance of a fully expanded infructescence was also measured for each individual. Significant differences in mean time to inflorescence, mean time to re-closure, mean time to fruit, and mean total flowering time were revealed among some dandelion clones (Kruskal-Wallis, P ≤ 0.0005). No differences in mean number of inflorescence buds per plant (P = 0.2217), mean time to bud (P = 0.2396), or mean scape length (P = 0.3688) were detected among the nine clones. These results suggest that differences in floral stage timing may in part involve varying genotypic environmental response characteristics and that these differences may have potential fitness effects. Further research is needed to determine if such clonal differences are observed under a broader range of uniform environmental conditions.

  7. Effects of origin, seasons and storage under different temperatures on germination of Senecio vulgaris (Asteraceae) seeds

    Science.gov (United States)

    2016-01-01

    Invasive plants colonize new environments, become pests and cause biodiversity loss, economic loss and health damage. Senecio vulgaris L. (Common groundsel, Asteraceae), a widely distributing cosmopolitan weed in the temperate area, is reported with large populations in the north–eastern and south–western part, but not in southern, central, or north-western parts of China. We studied the germination behavior of S. vulgaris to explain the distribution and the biological invasion of this species in China. We used seeds originating from six native and six invasive populations to conduct germination experiments in a climate chamber and under outdoor condition. When incubated in a climate chamber (15 °C), seeds from the majority of the populations showed >90% germination percentage (GP) and the GP was equal for seeds with a native and invasive origin. The mean germination time (MGT) was significantly different among the populations. Under outdoor conditions, significant effects of origin, storage conditions (stored at 4 °C or ambient room temperature, ca. 27 °C) and seasons (in summer or autumn) were observed on the GP while the MGT was only affected by the season. In autumn, the GP (38.6%) was higher and the MGT was slightly longer than that in summer. In autumn, seeds stored at 4 °C showed higher GP than those stored at ambient room temperature (ca.27 °C), and seeds from invasive populations revealed higher GP than those from native populations. The results implied that the high temperature in summer has a negative impact on the germination and might cause viability loss or secondary dormancy to S. vulgaris seeds. Our study offers a clue to exploring what factor limits the distribution of S. vulgaris in China by explaining why, in the cities in South-East China and central China such as Wuhan, S. vulgaris cannot establish natural and viable populations. PMID:27602303

  8. Study of the antitumor potential of Bidens pilosa (Asteraceae) used in Brazilian folk medicine.

    Science.gov (United States)

    Kviecinski, Maicon Roberto; Felipe, Karina Bettega; Schoenfelder, Tatiana; de Lemos Wiese, Luiz Paulo; Rossi, Maria Helena; Gonçalez, Edlayne; Felicio, Joana D'arc; Filho, Danilo Wilhelm; Pedrosa, Rozangela Curi

    2008-04-17

    Bidens pilosa (L.) (Asteraceae) is a medicinal plant traditionally used in Brazil for treating conditions that can be related to cancer. Therefore the present study was carried out to evaluate the antitumor activity of extracts obtained from the aerial parts of this plant species. The crude hydroalcoholic extract (HAE) (water:alcohol, 6:4) and solvent fractions (chloroform=CHCl3,ethyl acetate=EtOAc, methanol=MeOH) were assessed for cytotoxicity assay by the brine shrimp and hemolytic, MTT and NRU assays. The antiproliferative potential of the crude extract and fractions was investigated in vivo using the Ehrlich ascites carcinoma (EAC) in isogenic Balb/c mice that were administered intraperitoneally 150 and 300 mg/kg body weight per day for nine days beginning 24 h after tumor inoculation. In in vitro cytotoxicity using Ehrlich ascites carcinoma cell line assay CHCl3 extract proved to be more toxic than the crude HAE with an IC(50) of 97+/-7.2 and 83+/-5.2 microg/mL to NRU and MTT, respectively. Histomorphological evaluations indicated that the treatment with CHCl3 and HAE extracts significantly reduced (P<0.05) body weight, abdominal circumference, tumor volume, packed cell volume and viable cell count, when compared to EAC control group. Furthermore, nonviable tumor cell count increased significantly (P<0.01) only under treatment with CHCl3 or HAE, and this was accompanied by a marked percentage increase in life span (54.2 and 41.7%, respectively). Biochemical assays revealed that CHCl3 and HAE extracts were also able to decrease serum LDH activity (39.5 and 30.6%) and GSH concentration (94.6 and 50.7%) in ascitic fluid, respectively. The chloroform fraction showed the best and methanolic the worst antitumor activity.

  9. Ficus sur (Moraceae and Gymnanthemum coloratum (Asteraceae: Vernonieae – first distribution records for Namibia

    Directory of Open Access Journals (Sweden)

    Wessel Swanepoel

    2015-03-01

    Full Text Available Background: The distribution of Ficus sur includes most of tropical Africa, but whilst this species was suspected to occur in Namibia, this has not been verified. Gymnanthemum coloratum is a tropical African savannah shrub or tree that has been recorded for Botswana, Swaziland and South Africa, but which has not previously been recorded for Namibia.Objectives: To formally document the first records of two plant species from Namibia and provide habitat details of the localities from which these species were recorded.Method: The data presented have resulted from botanical expeditions to the poorly known Baynes Mountains in the Koakoveld region of Namibia. Specimens of the two species in the National Herbarium, Pretoria were examined to verify the identity in the case of G. coloratum, and to document additional records in Namibia for F. sur.Results: Ficus sur was recorded from two localities, and a third locality based on a specimen in the National Herbarium, Pretoria, was verified. Gymnanthemum coloratum, a member of the Asteraceae, was recorded from a single locality.Conclusion: The fact that F. sur was collected at more than one location in the Kaokoveld suggests that it is probably more widespread in suitable microhabitats. Ficus sur also occurs further north in Angola, suggesting that the Kaokoveld plants represent a cross-border outlier of the much more widespread Angolan population. Gymnanthemum coloratum was only recorded from the one locality in the Koakoveld. The species also occurs in Angola, which suggests that the Kaokoveld plant represents a cross-border outlier of the population in that country.

  10. Antiplasmodial activity of sesquiterpene lactones and a sucrose ester from Vernonia guineensis Benth. (Asteraceae)

    Science.gov (United States)

    Toyang, Ngeh J.; Krause, Michael A.; Fairhurst, Rick M.; Tane, Pierre; Bryant, Joseph; Verpoorte, Rob

    2013-01-01

    Ethnopharmacological relevance Aqueous preparations of Vernonia guineensis Benth. (Asteraceae) are used in Cameroonian folk medicine as a general stimulant and to treat various illnesses and conditions including malaria, bacterial infections and helminthic infestations. Materials and methods 10-g samples of the leaf and tuber powders of V. guineensis were extracted separately using dichloromethane, methanol and distilled water. The extracts were dried in vacuo and used in bioassays. These extracts and three compounds previously isolated from V. guineensis [vernopicrin (1), vernomelitensin (2) and pentaisovalerylsucrose (3)] were screened for antiplasmodial activity against chloroquine (CQ)-sensitive (Hb3) and CQ-resistant (Dd2) Plasmodium falciparum lines. Results Crude extracts and pure compounds from V. guineensis showed antiplasmodial activity against both Hb3 and Dd2. The IC50 values of extracts ranged from 1.64 – 27.2 μg/ml for Hb3 and 1.82 – 30.0 μg/ml for Dd2; those for compounds 1, 2 and 3 ranged from 0.47 – 1.62 μg/ml (1364 – 1774 nM) for Hb3 and 0.57 – 1.50 μg/ml (1644 – 2332 nM) for Dd2. None of the crude extracts or pure compounds was observed to exert toxic effects on the erythrocytes used to cultivate the P. falciparum lines. Conclusion In Cameroonian folk medicine, V. guineensis may be used to treat malaria in part due to the antiplasmodial activity of sesquiterpene lactones (1, 2), a sucrose ester (3) and perhaps other compounds present in crude plant extracts. Exploring the safety and antiplasmodial efficacy of these compounds in vivo requires further study. PMID:23542146

  11. Inaccessible Biodiversity on Limestone Cliffs: Aster tianmenshanensis (Asteraceae, a New Critically Endangered Species from China.

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    Guo-Jin Zhang

    Full Text Available Aster tianmenshanensis G. J. Zhang & T. G. Gao, a new species of Asteraceae from southern China is described and illustrated based on evidence from morphology, micromorphology and molecular phylogeny. The new species is superficially similar to Aster salwinensis Onno in having rosettes of spatulate leaves and a solitary, terminal capitulum, but it differs by its glabrous leaf margins, unequal disc floret lobes and 1-seriate pappus. The molecular phylogenetic analysis, based on nuclear sequences ITS, ETS and chloroplast sequence trnL-F, showed that the new species was nested within the genus Aster and formed a well supported clade with Aster verticillatus (Reinw. Brouillet et al. The new species differs from the latter in having unbranched stems, much larger capitula, unequal disc floret lobes, beakless achenes and persistent pappus. In particular, A. tianmenshanensis has very short stigmatic lines, only ca. 0.18 mm long and less than 1/3 of the length of sterile style tip appendages, remarkably different from its congeners. This type of stigmatic line, as far as we know, has not been found in any other species of Aster. The very short stigmatic lines plus the unequal disc floret lobes imply that the new species may have a very specialized pollination system, which may be a consequence of habitat specialization. The new species grows only on the limestone cliffs of Mt. Tianmen, Hunan Province, at the elevation of 1400 m. It could only be accessed when a plank walkway was built across the cliffs for tourists. As it is known only from an area estimated at less than 10 km2 and a walkway passes through this location, its habitat could be easily disturbed. This species should best be treated as Critically Endangered based on the International Union for Conservation of Nature Red List Categories and Criteria B2a.

  12. Morphogenesis of galls induced by Baccharopelma dracunculifoliae (Hemiptera: Psyllidae on Baccharis dracunculifolia (Asteraceae leaves

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    M. Arduin

    Full Text Available The commonest insect gall on Baccharis dracunculifolia (Asteraceae leaves is induced by Baccharopelma dracunculifoliae (Hemiptera, Psyllidae. The gall-inducing insect attacks young leaves in both the unfolded and the fully expanded stages. Four developmental phases were observed in this type of gall: 1 A folding phase, during which the leaf lamina folded upward alongside the midrib and the edges of the upper portion of the leaf approached each other, forming a longitudinal slit. A single chamber was formed on the adaxial surface of the leaf; 2 A swelling phase, in which the folded leaf tissues thickened and the edges of the leaf drew closer together, narrowing the slit. In this phase the gall matured, turning succulent, fusiform and pale green. The single nymphal chamber was lined with white wax and was able to house from one to several nymphs; 3 A dehiscence phase, characterized by the opening of the slit to release inducers; and 4 A senescence phase, when the gall turned dark and dry. The dermal system of the mature gall was composed of a single-layered epidermis. The mesophyll was swollen, and the swelling was due mainly to hyperplasia of the parenchyma. The vascular tissues along the midrib vein were conspicuous and the perivascular fibers resembled parenchymal cells. The hypertrophied secretory cavities contained low lipophylic content. This gall does not form nutritive tissue, but salivary sheaths left by the inducers were observed near the parenchyma, vascular bundles and secretory cavities. This study complements our current knowledge of gall biology and sheds further light on the plasticity of plant tissues stimulated by biotic factors.

  13. Modular Power System Configured with Standard Product Hybrid DC-DC Converters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — VPT proposes an innovative concept whereby complex NASA space power electronic systems can be configured using a small number of qualified hybrid DC-DC converter and...

  14. Improved Control Strategy for T-type Isolated DC/DC Converters

    DEFF Research Database (Denmark)

    Liu, Dong; Deng, Fujin; Wang, Yanbo

    2017-01-01

    T-type isolated DC/DC converters have recently attracted attention due to their numerous advantages, including few components, low cost, and symmetrical operation of transformers. This study proposes an improved control strategy for increasing the efficiency of T-type isolated DC/DC converters....... Under the proposed strategy, the primary circulating current flows through the auxiliary switches (metal–oxide–semiconductor field-effect transistors) instead of their body diodes in free-wheeling periods. Such feature can reduce conduction losses, thereby improving the efficiency of T-type isolated DC....../DC converters. The operation principles and performances of T-type isolated DC/DC converters under the proposed control strategy are analyzed in detail and verified through the simulation and experimental results....

  15. Development of a DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

    Science.gov (United States)

    Feld, L.; Fimmers, C.; Karpinski, W.; Klein, K.; Lipinski, M.; Preuten, M.; Rauch, M.; Rittich, D.; Sammet, J.; Wlochal, M.

    2014-01-01

    A novel powering scheme based on the DC-DC conversion technique will be exploited to power the CMS Phase-1 pixel detector. DC-DC buck converters for the CMS pixel project have been developed, based on the AMIS5 ASIC designed by CERN. The powering system of the Phase-1 pixel detector is described and the performance of the converter prototypes is detailed, including power efficiency, stability of the output voltage, shielding, and thermal management. Results from a test of the magnetic field tolerance of the DC-DC converters are reported. System tests with pixel modules using many components of the future pixel barrel system are summarized. Finally first impressions from a pre-series of 200 DC-DC converters are presented.

  16. Wide Temperature Range DC-DC Boost Converters for Command/Control/Drive Electronics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We shall develop wide temperature range DC-DC boost converters that can be fabricated using commercial CMOS foundries. The boost converters will increase the low...

  17. Digitally intensive DC-DC converter for extreme space environments Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Space Micro –Arizona State University (ASU) team will develop an all-digitally controlled, wide temperature range point-of-load switch-mode DC-DC regulator...

  18. DIAGNOSTIC/PROGNOSTIC EXPERIMENTS FOR CAPACITOR DEGRADATION AND HEALTH MONITORING IN DC-DC CONVERTERS

    Data.gov (United States)

    National Aeronautics and Space Administration — Studying and analyzing the ageing mechanisms of electronic components avionics in systems such as the GPS and INAV are of critical importance. In DC-DC power...

  19. Decentralized Nonlinear Controller Based SiC Parallel DC-DC Converter Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is aimed at demonstrating the feasibility of a Decentralized Control based SiC Parallel DC-DC Converter Unit (DDCU) with targeted application for...

  20. Development of a DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

    CERN Document Server

    Feld, Lutz Werner; Karpinski, Waclaw; Klein, Katja; Lipinski, Martin; Preuten, Marius; Max Rauch; Rittich, David Michael; Sammet, Jan Domenik; Wlochal, Michael

    2014-01-01

    A novel powering scheme based on the DC-DC conversion technique will be exploited to power the CMS Phase-1 pixel detector. DC-DC buck converters for the CMS pixel project have been developed, based on the AMIS5 ASIC designed by CERN. The powering system of the Phase-1 pixel detector is described and the performance of the converter prototypes is detailed, including power efficiency, stability of the output voltage, shielding, and thermal management. Results from a test of the magnetic field tolerance of the DC-DC converters are reported. System tests with pixel modules using many components of the future pixel barrel system are summarized. Finally first impressions from a pre-series of 200 DC-DC converters are presented.

  1. Hybrid-Circuit Module For Dc-To-Dc Power Converter

    Science.gov (United States)

    Vorperian, Vatche; Detwiler, Robert; Karmon, Dan

    1996-01-01

    Power hybrid module is general-purpose power-switching module providing flexibility in design and application. Complete dc-to-dc power converter constructed by adding input/output filters and feedback circuitry to module to suit specific application.

  2. High Efficiency Interleaved Active Clamped Dc-Dc Converter with Fuel Cell for High Voltage Applications

    Directory of Open Access Journals (Sweden)

    Sona P

    2014-02-01

    Full Text Available A high efficiency interleaved ZVS active clamped current fed dc-dc converter is proposed in this paper specially used for fuel cell applications. As the fuel cell output is very low we are in need of a step up dc-dc converter. Here a current fed dc-dc converter is used. Two current fed dc-dc converters are interleaved by connecting their inputs in parallel and outputs in series. With this proposed methodology input current ripples in the fuel cell stacks can be reduced and a regulated output voltage ripples can be obtained. The active clamping circuit used in this model absorbs the turn off voltage spikes hence low voltage devices with low on state resistance can be used.Voltage doubler circuits will give double the output voltage than normal with smaller transformer turns ratio and flexibility. The proposed method is simulated in MATLAB for verifying the accuracy of the proposed design.

  3. Effect of Antioxidants on DC Tree and Grounded DC Tree in XLPE

    Science.gov (United States)

    Kawanami, Hiroshi; Komatsu, Isao; Sekii, Yasuo; Saito, Mitsugu; Sugi, Kazuyuki

    To study the effects of antioxidants on the initiation of the DC tree and the grounded DC tree, experiments were conducted using XLPE specimens containing phenolic and sulfur type antioxidants. Experimental results showed that sulfur type antioxidants in XLPE have the effect of increasing inception voltages of both the DC tree and the grounded DC tree. Based on results of those experiments, the mechanism of increase in the inception voltage of the DC tree and the grounded DC tree by antioxidants was examined along with the mechanism of polarity effects on those trees. Results showed a promotional effect of charge injection from a needle electrode by antioxidants, which are responsible for the increased inception voltages of the DC tree. Charge trapping by antioxidants explains the increase of inception voltages of the grounded DC tree.

  4. Digitally intensive DC-DC converter for extreme space environments Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Space Micro-Arizona State University (ASU) team will develop an all-digitally controlled, wide temperature range point-of-load switch-mode DC-DC regulator core...

  5. 76 FR 52225 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

    Science.gov (United States)

    2011-08-22

    ... Model DC-9-81 (MD- 81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 Airplanes AGENCY... Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590. FOR FURTHER INFORMATION... ADs (b) None. Applicability (c) This AD applies to The Boeing Company Model DC-9-81 (MD-81),...

  6. Effectiveness of Asteraceae extracts on Trichostrongylidae eggs development in sheep Eficácia de extratos da família Asteraceae no desenvolvimento dos ovos de Trichostrongilídeos de ovinos

    Directory of Open Access Journals (Sweden)

    Silvana Krychak-Furtado

    2011-09-01

    Full Text Available Data on in vitro evaluation of extracts of three species of the Asteraceae family on the development of Trichostrongylidae eggs in sheep are presented. Egg hatchability was tested using herbal extracts prepared in a Soxhlet extractor, and using hydrolate prepared by means of hydrodistillation. The laboratory tests showed that the ethanol extract from flowers of the species Aster lanceolatus presented high activity against Trichostrongylidae eggs development in sheep, inhibiting larva formation by 91% within 48 hours, and maintaining similar rates after 72 hours.Apresentam-se dados da avaliação in vitro de três espécies vegetais da família Asteraceae sobre o desenvolvimento dos ovos de Trichostrongilídeos de ovinos. Realizou-se o teste de eclodibilidade com extratos vegetais preparados por aparelho de Soxhlet e hidrolato preparado por hidrodestilação. Os testes laboratoriais evidenciaram que o extrato etanólico das flores da espécie Aster lanceolatus apresenta alta atividade sobre o desenvolvimento dos ovos de Trichostrongilídeos de ovinos, inibindo em 91% a formação da larva em 48 horas, mantendo-se índices próximos em 72 horas.

  7. Tipificación y estatus raxonómico de Centaurea resupinata subsp. virens (sect. Willkommia Blanca, Asteraceae [Typification and taxonomic status of Centaurea resupinata subsp. virens comb. et stat. nov. (Sect. Willkommia Blanca, Asteraceae

    Directory of Open Access Journals (Sweden)

    P. Pablo FERRER GALLEGO

    2012-12-01

    Full Text Available RESUMEN: Se reivindica el valor taxonómico y lectotipifica el nombre de Centaurea incana Lag. (non auct. β virens (Sect. Willkommia Blanca, Asteraceae propuesto por Carlos Pau para describir una planta presente en la sierra litoral valenciana de Carcaixent (Valencia. Esta variedad se recombina con rango subespecífico dentro C. resupinta Coss., acorde con la actual sistemática propuesta para este complejo grupo de plantas. Morfológicamente esta planta se caracterizada por la ausencia o el pequeño tamaño de las fimbrias en el ápice de las brácteas involucrales del capítulo. ABSTRACT: We both propose the taxonomic value and lectotypify the name of Centaurea incana Lag. (non auct. β virens (Sect. Willkommia Blanca, Asteraceae proposed by Carlos Pau to describe a plant taxa living in the Valencian litoral range of Carcaixent (Valencia, Spain. This variety is recombined with subspecific rank inside C. resupinata Coss., following the current systematics proposed for this plant group. As main morphological trait, this subspecies is characterised by the absence or very low size of fimbriae under the involucral bract ápex.

  8. Studies of Interleaved DC-DC Boost Converters with Coupled Inductors

    Science.gov (United States)

    2011-04-01

    power density requirements, interleaved buck and boost converters have been studied in recent years for their potential to improve power converter ...duty ratio of switch S1. Figure 1: Conventional DC-DC Boost Converter Topology (1) Vout/Vin...interleaved DC-DC boost converters with coupled inductors. Included are discussions on a 10kW prototype, a 2kW high temperature prototype, and two 2kW

  9. A Family of Four Quadrant DC/DC Converters with Reduced Number of Components

    DEFF Research Database (Denmark)

    Mostaan, Ali; Soltani, Mohsen

    2015-01-01

    A family of four quadrant DC/DC converters is presented in this paper. Compare with existing four quadrant DC/DC converters that have been introduced in literature, the proposed converters have lower number of components. There are two bidirectional switches, two coupled inductors and one capacit...... effect is minimized in these converters. The effectiveness of the proposed converters is validated with simulation using MATLAB/SIMULINK....

  10. A Fixed-Frequency Bidirectional Resonant DC-DC Converter Suitable for Wide Voltage Gain Range

    DEFF Research Database (Denmark)

    Shen, Yanfeng; Wang, Huai; Al-Durra, Ahmed;

    2017-01-01

    This paper proposes a new bidirectional resonant dc-dc converter suitable for wide voltage gain range applications (e.g., energy storage systems). The proposed converter overcomes the narrow voltage gain range of conventional resonant DC-DC converters, and meanwhile achieves high efficiency...... and characteristics of the proposed converter are analyzed. Finally, a 1-kW converter prototype is built and the experimental results verify the theoretical analyses....

  11. 多路输出DC-DC电路设计%Design of multiple-output DC-DC circuit

    Institute of Scientific and Technical Information of China (English)

    郑晓庆; 杨日杰; 杨立永; 赵轩坤

    2012-01-01

    In order to convert a single input voltage to multiple outputs,a multiple-output DC-DC conversion circuit based LTC1624 and AMS1117 was designed in this paper. The circuit can convert the input voltage of 12V offered by a lead-acid battery to 5 V,3. 3 V and 1. 8 V as the output,and as tested,the output voltage of the DC-DC circuit designed in this paper is stable and reliable. Supplying power to different modules of a temperature measurement system, the circuit performance meets system requirements.%为了将单一输入电压变换为多路稳压输出,设计了基于LTC1624和AMS1117的DC-DC变换电路,该电路能够将铅酸蓄电池12V输入电压经过DC-DC变换后得到5V、3.3V和1.8V三路输出电压,经测试,设计的DC-DC电路输出电压稳定可靠.该电路应用于某温度测试系统的不同模块供电,电路性能满足系统要求.

  12. Extra-High-Voltage DC-DC Boost Converters Topology with Simple Control Strategy

    Directory of Open Access Journals (Sweden)

    K. Rajambal

    2009-01-01

    Full Text Available This paper presents the topology of operating DC-DC buck converter in boost mode for extra-high-voltage applications. Traditional DC-DC boost converters are used in high-voltage applications, but they are not economical due to the limited output voltage, efficiency and they require two sensors with complex control algorithm. Moreover, due to the effect of parasitic elements the output voltage and power transfer efficiency of DC-DC converters are limited. These limitations are overcome by using the voltage lift technique, opens a good way to improve the performance characteristics of DC-DC converter. The technique is applied to DC-DC converter and a simplified control algorithm in this paper. The performance of the controller is studied for both line and load disturbances. These converters perform positive DC-DC voltage increasing conversion with high power density, high efficiency, low cost in simple structure, small ripples, and wide range of control. Simulation results along theoretical analysis are provided to verify its performance.

  13. Characterization of diode valve in medium voltage dc/dc converter for wind turbines

    DEFF Research Database (Denmark)

    Dincan, Catalin Gabriel; Kjær, Philip Carne

    2016-01-01

    This paper proposes a methodology for characterization of medium voltage (MV), medium frequency (MF) rectifier diode valve. The intended application is for 10MW dc/dc converters used in DC offshore wind turbines. Sensitivity to semiconductor component parameter variation, snubber component...

  14. Analysis of DC/DC Converter Efficiency for Energy Storage System Based on Bidirectional Fuel Cells

    DEFF Research Database (Denmark)

    Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

    2013-01-01

    Renewable energy sources are fluctuating depending on the availability of the energy source. For this reason, energy storage is becoming more important and bidirectional fuel cells represent an attractive technology. Fuel cells require highcurrent low-voltage dc-dc or dc-ac converters as power...

  15. Startup Capability of Boost DC/DC Converter%Boost DC/DC的低压启动能力

    Institute of Scientific and Technical Information of China (English)

    向乾尹; 冯全源

    2011-01-01

    An analytical model was proposed to calculate the minimum startup voltage of a boost DC/ DC converter under a constant current load. The factors, such as the current load, the parasitic parameters, the saturation current and on-resistance of the power switch, the switching frequency, and the minimum startup voltage, etc. , which affect the startup capability of the boost DC/DC converter were analyzed with a steady-state analysis method. The model was applied to the design of a boost DC/ DC converter with a 0. 6 jxm CMOS process, and the maximum error of the minimum startup voltage calculated by the proposed model was 4. 5% compared with that by the HSPICE simulator.%为了准确预测Boost DC/DC低压启动能力,采用稳态分析方法,分析了电流负载、寄生参数、功率开关饱和电流及导通阻抗、开关频率、启动电路最低工作电压等因素对Boost DC/DC低压启动能力的影响,提出了预测Boost DC/DC恒流负载下最小启动电压的解析模型.将该模型应用于采用0.6 μm CMOS工艺的Boost DC/DC设计中,模型计算结果相对HSPICE仿真结果的最大误差为4.5%.本模型可推广至恒定电阻负载的情况.

  16. Genetic analysis of floral symmetry in Van Gogh's sunflowers reveals independent recruitment of CYCLOIDEA genes in the Asteraceae.

    Directory of Open Access Journals (Sweden)

    Mark A Chapman

    Full Text Available The genetic basis of floral symmetry is a topic of great interest because of its effect on pollinator behavior and, consequently, plant diversification. The Asteraceae, which is the largest family of flowering plants, is an ideal system in which to study this trait, as many species within the family exhibit a compound inflorescence containing both bilaterally symmetric (i.e., zygomorphic and radially symmetric (i.e., actinomorphic florets. In sunflower and related species, the inflorescence is composed of a single whorl of ray florets surrounding multiple whorls of disc florets. We show that in double-flowered (dbl sunflower mutants (in which disc florets develop bilateral symmetry, such as those captured by Vincent van Gogh in his famous nineteenth-century sunflower paintings, an insertion into the promoter region of a CYCLOIDEA (CYC-like gene (HaCYC2c that is normally expressed specifically in WT rays is instead expressed throughout the inflorescence, presumably resulting in the observed loss of actinomorphy. This same gene is mutated in two independent tubular-rayed (tub mutants, though these mutations involve apparently recent transposon insertions, resulting in little or no expression and radialization of the normally zygomorphic ray florets. Interestingly, a phylogenetic analysis of CYC-like genes from across the family suggests that different paralogs of this fascinating gene family have been independently recruited to specify zygomorphy in different species within the Asteraceae.

  17. Genetic analysis of floral symmetry in Van Gogh's sunflowers reveals independent recruitment of CYCLOIDEA genes in the Asteraceae.

    Science.gov (United States)

    Chapman, Mark A; Tang, Shunxue; Draeger, Dörthe; Nambeesan, Savithri; Shaffer, Hunter; Barb, Jessica G; Knapp, Steven J; Burke, John M

    2012-01-01

    The genetic basis of floral symmetry is a topic of great interest because of its effect on pollinator behavior and, consequently, plant diversification. The Asteraceae, which is the largest family of flowering plants, is an ideal system in which to study this trait, as many species within the family exhibit a compound inflorescence containing both bilaterally symmetric (i.e., zygomorphic) and radially symmetric (i.e., actinomorphic) florets. In sunflower and related species, the inflorescence is composed of a single whorl of ray florets surrounding multiple whorls of disc florets. We show that in double-flowered (dbl) sunflower mutants (in which disc florets develop bilateral symmetry), such as those captured by Vincent van Gogh in his famous nineteenth-century sunflower paintings, an insertion into the promoter region of a CYCLOIDEA (CYC)-like gene (HaCYC2c) that is normally expressed specifically in WT rays is instead expressed throughout the inflorescence, presumably resulting in the observed loss of actinomorphy. This same gene is mutated in two independent tubular-rayed (tub) mutants, though these mutations involve apparently recent transposon insertions, resulting in little or no expression and radialization of the normally zygomorphic ray florets. Interestingly, a phylogenetic analysis of CYC-like genes from across the family suggests that different paralogs of this fascinating gene family have been independently recruited to specify zygomorphy in different species within the Asteraceae.

  18. DC/DC converters for integration of double-layer condensers in onboard power supply; DC/DC-Wandler zur Einbindung von Doppelschichtkondensatoren in das Fahrzeugenergiebordnetz

    Energy Technology Data Exchange (ETDEWEB)

    Polenov, Dieter

    2010-01-15

    The paper discusses DC/DC converters for integration of double layer condensers into the onboard power system. First, requirements on DC/DC converters are listed and compared on the basis of three exemplary applications. A DC/DC converter concept is developed for decoupling transient high-power loads like electric steering systems. Three different topologies are compared using a specially developed method in order to find the best solution for the given application. In order to establish adequate criteria for selecting the switching frequency and inductivities of storage throttles, the influence of the trottle power change on the switching characteristics of the MOSFETs and on certain ranges of EMP interference emissions is investigated. As methods of optimising the operation of the synchronous rectifiers, parallel connection of Schottky diodes and synchronous rectifiers as well as the variation of the shut-off dead times of synchronous rectifiers were investigated. Further, a concept for converter control was developed in consideration of the intended application and topology. Finally, selected aspects for implementation of the DC/DC converter concept are presented as well as the results of experimental investigations.

  19. DC KIDS COUNT e-Databook Indicators

    Science.gov (United States)

    DC Action for Children, 2012

    2012-01-01

    This report presents indicators that are included in DC Action for Children's 2012 KIDS COUNT e-databook, their definitions and sources and the rationale for their selection. The indicators for DC KIDS COUNT represent a mix of traditional KIDS COUNT indicators of child well-being, such as the number of children living in poverty, and indicators of…

  20. DC-based immunotherapy for hematological malignancies.

    Science.gov (United States)

    Kitawaki, Toshio

    2014-02-01

    Great advances have been made in the treatment of hematological malignancies, but achieving a definitive cure remains an elusive goal for the majority of patients. Antigen-specific tumor immunotherapy has the potential to improve clinical outcome in patients with such diseases by eradicating chemotherapy-resistant tumor cell clones without damaging normal tissues. Dendritic cells (DCs) serve as an essential link between the innate and the adaptive immune systems, acting as key controllers of antigen-specific T cell responses. Molecular identification of tumor-specific antigens recognized by T lymphocytes and technical advances in ex vivo generation of human DCs has enabled us to develop DC-based tumor immunotherapies (also called "DC vaccines"). To date, a large number of clinical trials of DC vaccines have been conducted for a variety of tumors, including hematological malignancies. Overall, these trials have demonstrated that DC vaccines have excellent safety profiles, moderate immunological activity, and mild clinical efficacy. To establish a role for DC vaccines in the treatment of hematological malignancies, we need both to define patient populations that can obtain clinical benefit from DC vaccines and to develop combination therapies that augment clinical efficacy of DC vaccines. In this review, I will describe current status of DC-based immunotherapy for hematological malignancies, and discuss future perspectives in this field.

  1. ALA 2010: Where to Eat in DC

    Science.gov (United States)

    Library Journal, 2010

    2010-01-01

    As host to visitors and transplants from around the world, Washington, DC, benefits from the constant infusion of different cultures. Although most neighborhoods lack a unified culinary flavor, make no mistake: DC is a city of distinctive areas, each with its own style, ensuring that hungry American Library Association (ALA) 2010 conference…

  2. Modelling of flow phenomena during DC casting

    NARCIS (Netherlands)

    Zuidema, J.

    2005-01-01

    Modelling of Flow Phenomena during DC Casting Jan Zuidema The production of aluminium ingots, by semi-continuous casting, is a complex process. DC Casting stands for direct chill casting. During this process liquid aluminium transforms to solid aluminium while cooling down. This is not an instanta

  3. Modelling of flow phenomena during DC casting

    NARCIS (Netherlands)

    Zuidema, J.

    2005-01-01

    Modelling of Flow Phenomena during DC Casting Jan Zuidema The production of aluminium ingots, by semi-continuous casting, is a complex process. DC Casting stands for direct chill casting. During this process liquid aluminium transforms to solid aluminium while cooling down. This is not an

  4. Close-Range Gunfire around DC Schools

    Science.gov (United States)

    Bieler, Sam; La Vigne, Nancy

    2014-01-01

    This report examines the incidence of gunfire as measured by gunshot detection technology using data from the 2011-2012 school year. It finds that a disproportionate volume of gunfire happened near a small share of DC schools. About half of DC schools covered by gunshot detection sensors are in close proximity to gunfire, and four schools were…

  5. Electronic DC transformer with high power density

    NARCIS (Netherlands)

    Pavlovský, M.

    2006-01-01

    This thesis is concerned with the possibilities of increasing the power density of high-power dc-dc converters with galvanic isolation. Three cornerstones for reaching high power densities are identified as: size reduction of passive components, reduction of losses particularly in active components

  6. DC-based magnetic field controller

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)

    1994-01-01

    A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

  7. DC-based magnetic field controller

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, D.K.; Rankin, R.A.; Morgan, J.P.

    1994-05-31

    A magnetic field controller is described for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a Hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage. 1 fig.

  8. Type specimens of taxa of Artemisia L. (Asteraceae from Siberia and the Far East kept in the Herbarium of V.L. Komarov Botanical Insitute

    Directory of Open Access Journals (Sweden)

    A. A. Korobkov

    2015-04-01

    Full Text Available Typification of 97 Artemisia (Asteraceae taxa from Siberia and the Far East kept in the Herbarium of V.L. Komarov Botanical Institute was carried out. Holotypes for 39 taxa, lectotypes for 48 taxa, 28 syntypes and 4 isotypes are given.

  9. The first record of Baccharis L. (Asteraceae) as a host-plant genus for Nepticulidae (Lepidoptera), with description of new Stigmella species from South America

    Science.gov (United States)

    We record the first Nepticulidae species found to feed on Baccharis L. (Asteraceae). Despite the high species richness of Baccharis in the Western Hemisphere, no nepticulid has ever been recorded feeding on Baccharis. In this paper we describe four new Stigmella Schrank species feeding on Baccharis:...

  10. Intoxicação experimental pelos frutos de Xanthium cavanillesii (Asteraceae em ovinos Experimental poisoning by the burs of Xanthium cavanillesii (Asteraceae in sheep

    Directory of Open Access Journals (Sweden)

    Alexandre Paulino Loretti

    1999-04-01

    Full Text Available Os frutos moídos de Xanthium cavanillesii foram administrados por via oral, em doses únicas ou fracionadas, a 15 ovinos adultos. Nove ovinos morreram. Doses a partir de 2 g/kg em uma única administração foram letais para os ovinos. Doses únicas de 1,25 g/kg e doses de 2,5 g/kg subdivididas em duas administrações diárias (1,25 g/kg em dois dias consecutivos não causaram a intoxicação. Sinais clínicos foram observados apenas nos animais que morreram. Iniciavam entre 5 horas e 20 horas após o início da administração dos frutos. A evolução do quadro clínico foi superaguda (90 minutos a 3 horas ou aguda (9 a 13 horas. Sinais clínicos incluíam apatia, anorexia, hipomotilidade ruminal, tremores musculares generalizados, incoordenação motora, andar rígido, relutância em caminhar, instabilidade, quedas e decúbito. Muitos animais apresentavam corrimento nasal seromucoso que dificultava a respiração. Nas fases terminais havia tiques, sialorréia, convulsões, nistagmo, movimentos de pedalagem e períodos de apnéia seguidos de morte. Os principais achados de necropsia incluíam acentuação do padrão lobular do fígado acompanhada de petéquias distribuídas aleatoriamente na superfície capsular e de corte, distensão da vesícula biliar associada a edema e hemorragias na parede, ascite, hidrotórax, edema gelatinoso e translúcido da região perirrenal, conteúdo do ceco e alça proximal do cólon ascendente ressequido, compactado, recoberto por muco e estrias de sangue coagulado. Havia petéquias e sufusões disseminadas. A principal lesão microscópica consistia em acentuada necrose coagulativa hepatocelular centrolobular ou massiva acompanhada de congestão e hemorragia e vacuolização ou tumefação dos hepatócitos remanescentes.The ground burs of Xanthium cavanillesii (Asteraceae were force fed to 15 adult sheep in single doses or divided in two doses. Nine sheep died. Doses of 2 g/kg and above were lethal for the

  11. CHROMOSOME STUDIES IN VERNONIA CINCTA AND V. SCORPIOIDES (ASTERACEAE, VERNONIEAE ESTUDIOS CROMOSÓMICOS EN VERNONIA CINCTA y V. SCORPIOIDES (ASTERACEAE, VERNONIEAE

    Directory of Open Access Journals (Sweden)

    Massimiliano Dematteis

    2010-11-01

    Full Text Available

    Vernonia eineta Griseb. and V. seorpioides (Lam. Pers. (Asteraeeae, Vernonieae are two closely related taxa which have been considered by different authors either the same species or two varieties of the same species or two different species. In the present study a detailed chromosome analysis was carried out in an attempt to clarify the status and relationships of these two taxa. The cytological study revealed that Vernonia eineta has 2n=60 chromosomes and a
    karyotype formula composed of 36m + 16sm + St, whereas V. seorpioides presents 2n=66 and a karyotype with 34m + 20sm + 12t. Besides, V. eineta showed two chromosome pairs bearing satellites on the short arms, one m pair with linear satellite and one t pair with macrosatellite; while V. seorpioides presented one mchromosome pair carrying a linear satellite in the long armo In addition to the chromosome number, these species showed certain other karyotypic differences, mainly in theirformula, total chromosome length and asymmetry leve!. Chromosomal information here reported supports the specific status of both taxa. The presence of telocentric chromosomes in V. cincta and V. seorpioides would distinguish them from the remainder New World species of Vernoniawhich commonly have metacentric and submetacentric chromosomes.
    The karyotypic differences between V. cincta and V. seorpioides may be explained by the occurrence of structural rearrangements such as centric fusions or traslocations. This hypothesis is well supported by the similar total karyotype length of both taxa and the higher mean chromosome length of V. cincta, which presents a lower number of telocentric chromosomes than V. seorpioides.
    Vernonia cincta Griseb. y V. seorpioides V. (Lam. Pers.. (Asteraceae, Vernonieae son dos taxones estrechamente relacionados que han sido considerados por diferentes

  12. A Component-Reduced Zero-Voltage Switching Three-Level DC-DC Converter

    DEFF Research Database (Denmark)

    Qin, Zian; Pang, Ying; Wang, Huai;

    2016-01-01

    The basic Zero-Voltage Switching (ZVS) three-level DC-DC converter has one clamping capacitor to realize the ZVS of the switches, and two clamping diodes to clamp the voltage of the clamping capacitor. In order to reduce the reverse recovery loss of the diode as well as its cost, this paper...... proposes to remove one of the clamping diodes in basic ZVS three-level DC-DC converter. With less components, the proposed converter can still have a stable clamping capacitor voltage, which is clamped at half of the dc link voltage. Moreover, the ZVS performance will be influenced by removing the clamping...

  13. Drilling history core hole DC-4

    Energy Technology Data Exchange (ETDEWEB)

    1978-12-01

    Core hole DC-4 was completed at a depth of 3998 feet in December, 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scission, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Sicsson, Inc. furnished the engineering, daily supervision of the cable tool and core drilling activities, and geological core logging for DC-4. Core hole DC-4 is located on the Hanford Site about 3 miles east of the Yakima Barricade and approximately 103 feet southwest of rotary hole DC-5, which was completed to 3990 feet in February, 1978. Hanford Site coordinates reported for hole DC-4 are north 49,385.62 feet and west 85,207.63 feet, and Washington State coordinates are north 454,468.73 feet and east 2,209,990.87 feet. No elevation survey is available for hole DC-4, but it is approximately 745 feet above mean sea level based upon the survey of hole DC-5, which has a reported elevation of 745.16 feet on the top of the 3-inch flange. The purpose of core hole DC-4 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection, and to provide a borehole for hydrologic testing, cross-hole seismic shear, and pressure wave velocity studies with rotary hole DC-5. Hole DC-4 was drilled through the overburden into basalt bedrock by cable tool methods (0-623 feet) and continuously cored through the final interval (623 to 3998 feet).Core recovery was 95.8 percent of the total footage cored.

  14. Controlling DC-DC converters by chaos-based pulse width modulation to reduce EMI

    Energy Technology Data Exchange (ETDEWEB)

    Li Hong [Department of Mathematics and Computer Science, FernUniversitaet in Hagen, 58084 Hagen (Germany)], E-mail: hong.li@FernUni-Hagen.de; Zhang Bo [School of Electric Power, South China University of Technology, Guangzhou (China); Li Zhong; Halang, Wolfgang A. [Department of Mathematics and Computer Science, FernUniversitaet in Hagen, 58084 Hagen (Germany); Chen Guanrong [Department of Electronic Engineering, City University of Hong Kong, Hong Kong (China)

    2009-11-15

    In this paper, periodic and chaotic behaviors of DC-DC converters under certain parametric conditions are simulated, experimentally verified, and analyzed. Motivated by the work of J.H.B. Deane and D.C. Hamill in 1996, where chaotic phenomena are useful in suppressing electromagnetic interference (EMI) by adjusting the parameters of the DC-DC converter and making it operate in chaos, a chaos-based pulse width modulation (CPWM) is proposed to distribute the harmonics of the DC-DC converters continuously and evenly over a wide frequency range, thereby reducing the EMI. The output waves and spectral properties of the EMI are simulated and analyzed as the carrier frequency or amplitude changes with regard to different chaotic maps. Simulation and experimental results are given to illustrate the effectiveness of the proposed CPWM, which provides a good example of applying chaos theory in engineering practice.

  15. Voltage Tracking of a DC-DC Flyback Converter Using Neural Network Control

    Directory of Open Access Journals (Sweden)

    Wahyu Mulyo Utomo

    2012-01-01

    Full Text Available This paper proposes a neural network control scheme of a DC-DC Flyback converter that will step up a 12V DC and applied it on brushless DC motor with 12 and 24V dc. In this technique, a back propagation learning algorithm is derived. The controller is designed to track the output voltage of the DC-DC converter and to improve performance of the Flyback converter during transient operations. Furthermore, to investigate the effectiveness of the proposed controller, some operations such as starting-up and reference voltage variations are verified. The numerical simulation results show that the proposed controller has a better performance compare to the conventional PI-Controller method.

  16. High Current Planar Magnetics for High Efficiency Bidirectional DC-DC Converters for Fuel Cell Applications

    DEFF Research Database (Denmark)

    Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

    2014-01-01

    Efficiency is one of the main concerns during the design phase of switch mode power supply. Planar magnetics based on PCB windings have the potential to reduce the magnetic manufacturing cost however, one of their main drawbacks comes from their low filling factor and high stray capacitance....... This paper presents an analysis of different planar windings configurations focusing on dc and ac resistances in order to achieve highly efficiency in dc-dc converters. The analysis considers different copper thicknesses form 70 μm up to 1500 μm (extreme copper PCB) taking into account manufacturing...... complexity and challenges. The analysis is focused on a high current inductor for a dc-dc converter for fuel cell applications and it is based on FEM simulations. Analysis and results are verified on a 6 kW dc-dc isolated full bridge boost converter prototype based on fully planar magnetics achieving a peak...

  17. A high voltage ratio and low ripple interleaved DC-DC converter for fuel cell applications.

    Science.gov (United States)

    Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

    2012-01-01

    This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters.

  18. Chromosomal organization and phylogenetic relationships in Hypochaeris species (Asteraceae from Brazil

    Directory of Open Access Journals (Sweden)

    Claudete de Fátima Ruas

    2005-03-01

    Full Text Available The association of cytogenetic and molecular techniques has contributed to the analysis of chromosome organization and phylogeny in plants. The fluorochrome GC-specific CMA3, fluorescent in situ hybridization (FISH and RAPD (Random Amplified Polymorphic DNA markers were used to investigate chromosome structure and genetic relationships in Hypochaeris (Asteraceae. Seven species native to South America, and two species introduced from Europe (H. glabra and Hypochaeris sp were studied. FISH with rDNA probes identified one or two loci of 18S-5.8S-25S rDNA in the South American Hypochaeris species and one locus in the European species. Only one 5S rDNA locus was seen in all species studied. Blocks of GC-rich heterochromatin (CMA-positive bands associated to 18S-5.8S-25SrDNA loci were detected in all species investigated. Co-location of 5S rDNA and CMA bands was also observed, except for three South American species and Hypochaeris sp. In two South American species, additional CMA bands not related to rDNA were observed on the long arm of chromosome 2, near to the centromere. Hypochaeris glabra exhibited additional CMA-positive signals distributed at pericentromeric regions, on the short arms of all chromosomes. A total of 122 RAPD markers were used to determine the genetic relationships among species. The level of polymorphism was very high, revealing two genetic groups comprising the South American and the European species, thus supporting a previous hypothesis of monophyly of the South American Hypochaeris species. The coefficients of genetic similarity between European and South American species were 0.35, on average. Polymorphism was also high within the two groups. The genetic associations observed with RAPD markers were consistent with chromosome characteristics. Species carrying similar distribution of 45S rDNA loci and CMA-positive signals were included in the same group revealed by RAPDs. Cytogenetic and molecular data support the view that

  19. Mexican Arnica (Heterotheca inuloides Cass. Asteraceae: Astereae): Ethnomedical uses, chemical constituents and biological properties.

    Science.gov (United States)

    Rodríguez-Chávez, José Luis; Egas, Verónica; Linares, Edelmira; Bye, Robert; Hernández, Tzasna; Espinosa-García, Francisco J; Delgado, Guillermo

    2017-01-04

    Heterotheca inuloides Cass. (Asteraceae) has been traditionally used to treat a wide range of diseases in Mexico in the treatment of rheumatism, topical skin inflammation, muscular pain colic, and other painful conditions associated with inflammatory processes, additionally has been used to treat dental diseases, and gastrointestinal disorders. This species has also been used for the treatment of cancer and diabetes. This review provides up-to-date information on the botanical characterization, traditional uses, chemical constituents, as well as the biolological activities of H. inuloides. A literature search was conducted by analyzing the published scientific material. Information related to H. inuloides was collected from various primary information sources, including books, published articles in peer-reviewed journals, monographs, theses and government survey reports. The electronic search of bibliographic information was gathered from accepted scientific databases such as Scienfinder, ISI Web of Science, Scielo, LILACS, Redalyc, Pubmed, SCOPUS and Google Scholar. To date, more than 140 compounds have been identified from H. inuloides, including cadinane sesquiterpenes, flavonoids, phytosterols, triterpenes, benzoic acid derivatives, and other types of compounds. Many biological properties associated with H. inuloides. Many studies have shown that the extracts and some compounds isolated from this plant exhibit a broad spectrum of biological activities such as antioxidant, antitumor, anti-inflammatory, cytotoxic, and chelating activities, as well as insecticidal and phytotoxic activity. To date, reports on the toxicity of H. inuloides are limited. A comprehensive analysis of the literature obtained through the above-mentioned sources confirmed that ethnomedical uses of H. inuloides have been recorded in Mexico to treat rheumatism, pain, and conditions associated with inflammatory processes. Pharmacological studies have demonstrated the activity of certain

  20. CARACTERIZACIÓN DE MICROSITIOS PARA EL ESTABLECIMIENTO DE PLÁNTULAS DE Espeletia uribei (Asteraceae

    Directory of Open Access Journals (Sweden)

    Angélica María Gallego Maya

    2016-04-01

    Full Text Available Con el fin de determinar si los micrositios de establecimiento están limitando el reclutamiento de las plántulas y la regeneración de Espeletia uribei, un frailejón endémico y valor objeto de conservación del Parque Nacional Natural Chingaza, se evaluaron diez variables bióticas y abióticas dentro de micrositios con plántulas y micrositios vacíos. Las variables que más se relacionaron con el establecimiento fueron: la distancia al adulto reproductivo más cercano, el tipo de zona de luz “abierta” y la estructura de vegetación “herbácea” asociada. La distancia al adulto reproductivo más cercano dificulta que las semillas alcancen micrositios más alejados debido al tipo de dispersión primaria barócora de la especie. Zonas de luz “abiertas” y vegetación asociada herbácea condicionaron la capacidad de germinación y establecimiento de la especie. Los resultados mostraron que el reclutamiento de E. uribei está limitado por la disponibilidad de micrositios que reúnan estas condiciones, un factor que es importante considerar para el planteamiento de futuros proyectos de manejo para la conservación y restauración de las poblaciones de la especie.Characterization of Microsites for Seedling Establishment of Espeletia uribei (AsteraceaeIn order to determine whether microsites are limiting seedling recruitment and regeneration of Espeletica uribei (an endemic frailejon, a valuable species subject to conservation in the Parque Nacional Natural Chingaza ten biotic and abiotic variables were evaluated from E. uribei seedling microsites as well as from sites without seedlings. The variables associated with seedling establishment were distance from the nearest reproductive adult, the quality of exposure to light, and associated herbaceous structure. Reduced distances from the nearest reproductive adult made it difficult for the seeds to reach distant microsites due to the principle wind dispersal type (anemochory. Open gaps and

  1. Theory of multi-phase PWM DC/DC converter%多相PWM控制DC/DC变换器

    Institute of Scientific and Technical Information of China (English)

    陈小明

    2001-01-01

    @@ 概述 近年来,随着一些高性能CPU的出现,如Pentium 4、Athlon等,需要输出电压更小,更大电流的DC/DC变换器,对热性能、EMI及负载瞬变应答(Load Transient)的要求也不断提高.传统的单相DC/DC变换器日益显示出局限性.多相DC/DC变换器以其独特的性能,为高性能CPU电源的解决方案开辟的一条新路.

  2. Swarming Speed Control for DC Permanent Magnet Motor Drive via Pulse Width Modulation Technique and DC/DC Converter

    Directory of Open Access Journals (Sweden)

    A.S. Oshaba

    2013-05-01

    Full Text Available This study presents an approach for the speed control of a permanent magnet DC motor drive via Pulse Width Modulation (PWM technique and a DC/DC converter. The Particle Swarm Optimization (PSO technique is used to minimize a time domain objective function and obtain the optimal controller parameters. The performance of the proposed technique has been evaluated using various types of disturbances including load torque variations. Simulation results illustrate clearly the robustness of the controller and validity of the design technique for controlling the speed of permanent magnet motors.

  3. DC/DC开关变换器混沌现象研究综述%Summary of the Research on Chaos Phenomena of DC/DC Converter

    Institute of Scientific and Technical Information of China (English)

    蔚洋; 冯平

    2012-01-01

    DC/DC功率开关变换器是开关电源的核心部分,通过对其混沌现象的研究可以更加深刻地认识DC/DC变换器的本质,也会在将来基于混沌现象提出新的设计方法和控制策略,实现现有DC/DC变换器无法达到的性能.本文介绍了DC/DC变换器混沌现象的研究现状,对DC/DC变换器混沌现象的基本建模方法进行了综合对比分析,展望了DC/DC变换器混沌研究的发展和未来应用前景.%DC/DC power switch converter is the core part of switch power supply. Through the study of chaos phenomena, the essence of DC/DC converter can be more deeply understand, the new design methods and control strategies based on chaos phenomena will be put forward in the future, to achieve the existing DC/DC converter that cannot reach. This paper introduces the research status of the DC/DC converter chaos phenomena, makes comprehensive comparative analysis of the basic modeling method of DC/DC converter chaos phenomena, and looks to its development and future application prospect.

  4. Pulsed-DC DBD Plasma Actuators

    Science.gov (United States)

    Duong, Alan; McGowan, Ryan; Disser, Katherine; Corke, Thomas; Matlis, Eric

    2016-11-01

    A new powering system for dielectric barrier discharge (DBD) plasma actuators that utilizes a pulsed-DC waveform is presented. The plasma actuator arrangement is identical to most typical AC-DBD designs with staggered electrodes that are separated by a dielectric insulator. However instead of an AC voltage input to drive the actuator, the pulsed-DC utilizes a DC voltage source. The DC source is supplied to both electrodes, and remains constant in time for the exposed electrode. The DC source for the covered electrode is periodically grounded for very short instants and then allowed to rise to the source DC level. This process results in a plasma actuator body force that is significantly larger than that with an AC-DBD at the same voltages. The important characteristics used in optimizing the pulsed-DC plasma actuators are presented. Time-resolved velocity measurements near the actuator are further used to understand the underlying physics of its operation compared to the AC-DBD. Supported by NASA Glenn RC.

  5. Control and dynamic analysis of a parallel-connected single active bridge DC-DC converter for DC-grid wind farm application

    DEFF Research Database (Denmark)

    Park, Kiwoo; Chen, Zhe

    2015-01-01

    This study presents a control strategy and its dynamic analysis of a high-power dc-dc converter, which is constructed with the parallel-connected single active bridge (SAB) dc-dc converters for dc-grid wind farm applications. The structural and operational characteristics of the SAB dc-dc converter...... have several advantages for high-power applications, and the modular concept of the parallel-connected converter is highly beneficial especially for offshore wind farm applications in terms of maintenance cost and fault tolerance. To justify the feasibility of the parallel-connected SAB dc-dc converter...... for dc-grid wind farm applications, an input voltage control method based on the PI control will be introduced and the dynamics of the overall system will be analysed. The analysis results are to be verified by means of simulations and experiments....

  6. Expression of DC-SIGN and DC-SIGNRs in placentas of HIV-positive patients

    Directory of Open Access Journals (Sweden)

    Komala Pillay

    2014-09-01

    Full Text Available Background. Human dendritic cell-specific intracellular adhesion molecule-3 (ICAM3-grabbing non-integrin (DC-SIGN is a mannose-binding lectin that initiates interaction between dendritic cells and resting T-lymphocytes. DC-SIGN is highly expressed in placental tissue on dendritic cells and Hofbauer cells, and it is suggested that HIV may become adsorbed to DC-SIGN on Hofbauer cells as part of the mechanism of mother-to-child HIV transmission. A possible mechanism of transfer of the virus from the Hofbauer cells to the fetus is the subsequent adsorption to DC-SIGN-related molecules (DC-SIGNRs, present on immediately adjacent capillary vascular endothelium. However, data on DC-SIGN and DC-SIGNR expression in the placenta are few.Methods. Forty term placentas from HIV-positive mothers and 21 term placentas from HIV-negative mothers underwent immunohistochemistry staining for DC-SIGN and DC-SIGNR expression. Five random sets of 10 villi were assessed, and the average number of positive cells were counted in each case. In addition, where possible, maternal and cord blood viral loads and maternal CD4+ counts were performed in the HIV-positive group only.Results. The median maternal CD4+ count was 377 cells/µl and 27% of participants had undetectable viral loads; the median detectable viral load was 3.72 log. Most (97% of the cord bloods tested in infants from HIV-positive mothers had lower than detectable viral loads. HIV-positive cases had significantly greater expression of both DC-SIGNRs (median values in HIV-positive cases, 14.5 positive cells/10 villi (pc/10villi, compared with 11 pc/10villi in HIV-negative cases, p=0.020 and DC-SIGN (median value in HIV-positive cases, 26.5 pc/10villi, compared with 23 pc/10villi in HIV-negative cases, p=0.037. DC-SIGNR expression was also noted in Hofbauer cells and decidual macrophages in addition to endothelium (reported currently. There was no difference in expression of DC-SIGN and DC-SIGNRs in patients

  7. Robust DC/DC converter control for polymer electrolyte membrane fuel cell application

    Science.gov (United States)

    Wang, Ya-Xiong; Yu, Duck-Hyun; Chen, Shi-An; Kim, Young-Bae

    2014-09-01

    This study investigates a robust controller in regulating the pulse width modulation (PWM) of a DC/DC converter for a polymer electrolyte membrane fuel cell (PEMFC) application. A significant variation in the output voltage of a PEMFC depends on the power requirement and prevents a PEMFC from directly connecting to a subsequent power bus. DC/DC converters are utilized to step-up or step-down voltage to match the subsequent power bus voltage. In this study, a full dynamic model, which includes a PEMFC and boost and buck DC/DC converters, is developed under MATLAB/Simulink environment for control. A robust PWM duty ratio control for the converters is designed using time delay control (TDC). This control enables state variables to accurately follow the dynamics of a reference model using time-delayed information of plant input and output information within a few sampling periods. To prove the superiority of the TDC performance, traditional proportional-integral control (PIC) and model predictive control (MPC) are designed and implemented, and the simulation results are compared. The efficacies of TDC for the PEMFC-fed PWM DC/DC converters are validated through experimental test results using a 100 W PEMFC as well as boost and buck DC/DC converters.

  8. High power density dc/dc converter: Selection of converter topology

    Science.gov (United States)

    Divan, Deepakraj M.

    1990-01-01

    The work involved in the identification and selection of a suitable converter topology is described. Three new dc/dc converter topologies are proposed: Phase-Shifted Single Active Bridge DC/DC Converter; Single Phase Dual Active Bridges DC/DC Converter; and Three Phase Dual Active Bridges DC/DC Converter (Topology C). The salient features of these topologies are: (1) All are minimal in structure, i.e., each consists of an input and output bridge, input and output filter and a transformer, all components essential for a high power dc/dc conversion process; (2) All devices of both the bridges can operate under near zero-voltage conditions, making possible a reduction of device switching losses and hence, an increase in switching frequency; (3) All circuits operate at a constant frequency, thus simplifying the task of the magnetic and filter elements; (4) Since, the leakage inductance of the transformer is used as the main current transfer element, problems associated with the diode reverse recovery are eliminated. Also, this mode of operation allows easy paralleling of multiple modules for extending the power capacity of the system; (5) All circuits are least sensitive to parasitic impedances, infact the parasitics are efficently utilized; and (6) The soft switching transitions, result in low electromagnetic interference. A detailed analysis of each topology was carried out. Based on the analysis, the various device and component ratings for each topology operating at an optimum point, and under the given specifications, are tabulated and discussed.

  9. Novel bidirectional DC-DC converters based on the three-state switching cell

    Science.gov (United States)

    da Silva Júnior, José Carlos; Robles Balestero, Juan Paulo; Lessa Tofoli, Fernando

    2016-05-01

    It is well known that there is an increasing demand for bidirectional DC-DC converters for applications that range from renewable energy sources to electric vehicles. Within this context, this work proposes novel DC-DC converter topologies that use the three-state switching cell (3SSC), whose well-known advantages over conventional existing structures are ability to operate at high current levels, while current sharing is maintained by a high frequency transformer; reduction of cost and dimensions of magnetics; improved distribution of losses, with consequent increase of global efficiency and reduction of cost associated to the need of semiconductors with lower current ratings. Three distinct topologies can be derived from the 3SSC: one DC-DC converter with reversible current characteristic able to operate in the first and second quadrants; one DC-DC converter with reversible voltage characteristic able to operate in the first and third quadrants and one DC-DC converter with reversible current and voltage characteristics able to operate in four quadrants. Only the topology with bidirectional current characteristic is analysed in detail in terms of the operating stages in both nonoverlapping and overlapping modes, while the design procedure of the power stage elements is obtained. In order to validate the theoretical assumptions, an experimental prototype is also implemented, so that relevant issues can be properly discussed.

  10. Studi Komparasi Fungsi Keanggotaan Fuzzy sebagai Kontroler Bidirectional DC-DC Converter pada Sistem Penyimpan Energi

    Directory of Open Access Journals (Sweden)

    Eka Prasetyono

    2015-09-01

    Full Text Available Bidirectional DC-DC converter is needed in the energy storage system. The converter topology used in this paper was a non-isolated bidirectional DC-DC buck-boost converter. This converter worked in two ways, which the charging mode stored energy into battery when load current was less than nominal main DC current (set point and discharging mode transferred energy from battery to the load when its current exceeded set point value. Both of these modes worked automatically according to the load current. The charging and discharging currents were controlled by fuzzy logic controller which was implemented on microcontroller ARM Cortex-M4F STM32F407VG. This paper compares two types of fuzzy membership function (triangular and sigmoid in controlling bidirectional DC-DC converter. The results showed that fuzzy logic controller with triangle membership function and sigmoid as control bidirectional DC-DC converter had no significant different response, both had an average error for charging and discharging process under 4% with ripple current on the main DC bus around 0.5%. The computing time of program for fuzzy logic controller with triangular membership functions had 19.01% faster than sigmoid, and fuzzy logic computation time on a microcontroller with hardware floating point was 60% faster than software floating point.

  11. Study on the Control Algorithm of Two-Stage DC-DC Converter for Electric Vehicles

    Directory of Open Access Journals (Sweden)

    Changhao Piao

    2014-01-01

    Full Text Available The fast response, high efficiency, and good reliability are very important characteristics to electric vehicles (EVs dc/dc converters. Two-stage dc-dc converter is a kind of dc-dc topologies that can offer those characteristics to EVs. Presently, nonlinear control is an active area of research in the field of the control algorithm of dc-dc converters. However, very few papers research on two-stage converter for EVs. In this paper, a fixed switching frequency sliding mode (FSFSM controller and double-integral sliding mode (DISM controller for two-stage dc-dc converter are proposed. And a conventional linear control (lag is chosen as the comparison. The performances of the proposed FSFSM controller are compared with those obtained by the lag controller. In consequence, the satisfactory simulation and experiment results show that the FSFSM controller is capable of offering good large-signal operations with fast dynamical responses to the converter. At last, some other simulation results are presented to prove that the DISM controller is a promising method for the converter to eliminate the steady-state error.

  12. Superconducting DC homopolar motors for ship propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Heiberger, M.; Reed, M.R.; Creedon, W.P.; O' Hea, B.J. [General Atomic (United States)

    2000-07-01

    Superconducting DC homopolar motors have undergone recent advances in technology, warranting serious consideration of their use for ship propulsion. Homopolar motor propulsion is now practical because of two key technology developments: cryogen-free superconducting refrigeration and high performance motor fiber brushes. These compact motors are ideal for podded applications, where reduced drag and fuel consumption are predicted. In addition, the simple DC motor controller is more efficient and reliable compared with AC motor controllers. Military ships also benefit from increased stealth implicit in homopolar DC excitation, which also allows the option for direct hull or pod mounting. (authors)

  13. DC-Compensated Current Transformer †

    Science.gov (United States)

    Ripka, Pavel; Draxler, Karel; Styblíková, Renata

    2016-01-01

    Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component. PMID:26805830

  14. A series array of dc SQUIDs

    Energy Technology Data Exchange (ETDEWEB)

    Welty, R.P. (Colorado Univ., Boulder, CO (United States). Dept. of Electrical Engineering); Martinis, J.M. (Geraghty and Miller, Inc., Reston, VA (United States))

    1991-03-01

    This paper reports on a series array of 100 dc SQUIDs using trilayer Nb-AlO{sub x}-Nb junctions. The SQUIDs are modulated with a common flux bias line and produce an output voltage swing of several millivolts across the array. The large output voltage will allow direct connection to room temperature electronics without the transformer coupling and resulting frequency limitations commonly associated with dc SQUID amplifiers. The authors measured a bandwidth of dc to at least 175 MHz for a 100-SQUID array. The series array will be used as the output stage for a multistage integrated SQUID amplifier.

  15. Revisión taxonómica del género sudamericano Chrysolaena (Vernonieae, Asteraceae

    Directory of Open Access Journals (Sweden)

    Massimiliano Dematteis

    2009-07-01

    Full Text Available El género Chrysolaena H. Rob. (Vernonieae, Asteraceae se diferencia de los restantes miembros sudamericanos de la tribu por la presencia de indumento seríceo o velutino, anteras con apéndice apical glanduloso, estilo sin nódulo basal y cipselas glandulares. También se puede separar de otros grupos americanos por la morfología de los granos de polen y el número de cromosomas. Esta última es una de las diferencias más importantes, dado que Chrysolaena es el único miembro americano de la tribu con número básico x=10, un guarismo presente principalmente en las Vernonieae del Viejo Mundo. Hasta la actualidad, este género comprende 12 especies distribuidas principalmente en el sur de Brasil, Paraguay y nordeste de Argentina. En el presente trabajo se describen e ilustran todas las especies reconocidas hasta ahora y se incorporan otras seis entidades, dos de las cuales son nuevas para la ciencia. También se discuten las posibles relaciones filogenéticas del género y se amplía la distribución geográfica de la mayoría de las especies.A revision of the South American genus Chrysolaena (Vernonieae, Asteraceae.The genus Chrysolaena H. Rob. (Vernonieae, Asteraceae can be distinguished from the remaining South American members of the tribe by its sericeous to velvety indumentum, anthers with glandular apical appendages, styles lacking a basal nodule and glandular cypselas. It can also be separated from other American genera of the tribe by the pollen morphology and the chromosome number. The last constitutes one of the most important features, because Chrysolaena is the single American member of the tribe with basic number x=10, a number widespread in Old World Vernonieae. At the present, this genus comprises 12 species mainly distributed in southern Brazil, Paraguay and northeastern Argentina. In this paper, all the species recognized until now are described and illustrated and six entities are added to the group, two of which are new

  16. Constant switching frequency control-based linear-assisted DC/DC regulator for photovoltaic solar-powered facilities

    OpenAIRE

    Martínez García, Herminio; Grau Saldes, Antoni

    2015-01-01

    Hybrid DC-DC regulators or linear–assisted DC-DC regulators are structures that combine both a linear voltage regulator and a switching DC-DC converter. The main objective of this hybrid topology is to converge, in a single circuit topology, the best of both alternatives: One the one hand, obtaining small voltage output ripple, which is typical of linear regulator structures, and, on the other, achieving good energy efficiency, as in switching alternatives. While the linear regulator fixes th...

  17. LLC resonant half-bridge circuit design with DC-DC%LLC谐振半桥DC-DC电路设计

    Institute of Scientific and Technical Information of China (English)

    杨磊; 吴晓光; 羊彦

    2013-01-01

    LED drive power level after the DC-DC constant current circuit using LLC resonant half-bridge topology structure, and through the output current and voltage feedback loop to achieve constant current limiting function.LLC resonant half-bridge DC-DC constant current circuit power part comprises a resonant circuit and the output of the rectifier circuit, the control part chip power supply circuit, the control chip peripheral circuit, an output feedback loop, the test shows that the system has stable output can be good, long time working with high efficiency.%LED驱动电源的后级DC-DC恒流电路采用LLC谐振半桥的拓扑结构,并通过输出的电流电压双环反馈来实现恒流限压功能.LLC谐振半桥DC-DC恒流电路的功率部分包括了谐振电路和输出整流电路,控制部分有芯片供电电路、控制芯片外围电路、输出反馈回路等,经试验证明该系统输出稳定好,能够长时间高效工作.

  18. Determination of input/output characteristics of full-bridge AC/DC/DC converter for arc welding

    OpenAIRE

    Stefanov, Goce; Karadzinov, Ljupco; Sarac, Vasilija; Cingoski, Vlatko; Gelev, Saso

    2016-01-01

    This paper describes the design and practical implementation of AC/DC/DC converter in mode of arc welding. An analysis of the operation of AC/DC/DC converter and its input/output characteristics are determined with computer simulations. The practical part is consisted of AC/DC/DC converter prototype for arc welding with output power of 3 kW and switching frequency of 64 kHz. The operation of AC/DC/DC converter is validated with experimental measurements.

  19. (PFC) converters feeding brushless DC motor drive

    African Journals Online (AJOL)

    DR OKE

    harmonic distortion (THD) of supply current at AC mains for a wide range of ... An uncontrolled diode bridge rectifier (DBR) with high value of DC link ...... ac transmission systems), HVDC (High voltage direct current) transmission systems. Prof.

  20. Nonlinear Phenomena and Resonant Parametric Perturbation Control in QR-ZCS Buck DC-DC Converters

    Science.gov (United States)

    Hsieh, Fei-Hu; Liu, Feng-Shao; Hsieh, Hui-Chang

    The purpose of this study is to investigate the chaotic phenomena and to control in current-mode controlled quasi-resonant zero-current-switching (QR-ZCS) DC-DC buck converters, and to present control of chaos by resonant parametric perturbation control methods. First of all, MATLAB/SIMULINK is used to derive a mathematical model for QR-ZCS DC-DC buck converters, and to simulate the converters to observe the waveform of output voltages, inductance currents and phase-plane portraits from the period-doubling bifurcation to chaos by changing the load resistances. Secondly, using resonant parametric perturbation control in QR-ZCS buck DC-DC converters, the simulation results of the chaotic converter form chaos state turn into stable state period 1, and improve ripple amplitudes of converters under the chaos, to verify the validity of the proposes method.

  1. DC-DC Conversion Powering Schemes for the CMS Tracker at Super-LHC

    CERN Document Server

    Klein, Katja; Jussen, Rüdiger; Karpinski, Waclaw; Merz, Jennifer; Sammet, Jan

    2010-01-01

    The CMS experiment at the Large Hadron Collider (LHC) at CERN, Geneva, houses the largest silicon strip tracker ever built. For the foreseen luminosity upgrade of the LHC, the Super-LHC, however, a completely new silicon tracker will have to be constructed. One out of several major improvements currently under consideration is the implementation of a track trigger, with tracking information being provided to the first level trigger. Such an intelligent tracker design, utilising fast digital readout electronics, will most certainly lead to an increased power consumption, compared to today's tracker. In combination with the desire to reduce the amount of passive material inside the tracking volume and the impracticality to exchange or even add additional supply cables, a novel powering scheme will be inevitable. In this article a powering scheme based on DC-DC conversion is proposed, and requirements for the DC-DC converters are discussed. Studies of important DC-DC converter quantities such as th...

  2. The DC-DC conversion power system of the CMS Phase-1 pixel upgrade

    Science.gov (United States)

    Feld, L.; Karpinski, W.; Klein, K.; Lipinski, M.; Preuten, M.; Rauch, M.; Schmitz, St.; Wlochal, M.

    2015-01-01

    The pixel detector of the CMS experiment will be exchanged during the year-end technical stop in 2016/2017, as part of the experiment's Phase-1 upgrade. The new device will feature approximately twice the number of readout channels, and consequently the power consumption will be doubled. By moving to a DC-DC conversion powering scheme, it is possible to power the new pixel detector with the existing power supplies and cable plant. The power system of the Phase-1 pixel detector is described and the performance of the new components, including DC-DC converters, DC-DC converter motherboards and various power distribution boards, is detailed. The outcome of system tests in terms of electrical behaviour, thermal management and pixel module performance is discussed.

  3. Modelling and Simulation of Digital Compensation Technique for dc-dc Converter by Pole Placement

    Science.gov (United States)

    Shenbagalakshmi, R.; Sree Renga Raja, T.

    2015-09-01

    A thorough and effective analysis of the dc-dc converters is carried out in order to achieve the system stability and to improve the dynamic performance. A small signal modelling based on state space averaging technique for dc-dc converters is carried out. A digital state feedback gain matrix is derived by pole placement technique in order to achieve the stability of a completely controllable system. A prediction observer for the dc-dc converters is designed and a dynamic compensation (observer plus control law) is provided using separation principle. The output is very much improved with zero output voltage ripples, zero peak overshoot, and much lesser settling time in the range of ms and with higher overall efficiency (>90 %).

  4. DC-DC converters with reduced mass for trackers at the HL-LHC

    Science.gov (United States)

    Affolder, A.; Allongue, B.; Blanchot, G.; Faccio, F.; Fuentes, C.; Greenall, A.; Michelis, S.

    2011-11-01

    The development at CERN of low noise DC-DC converters for the powering of front-end systems enables the implementation of efficient powering schemes for the physics experiments at the HL-LHC. Recent tests made on the ATLAS short strip tracker modules confirm the full electromagnetic compatibility of the DC-DC converter prototypes with front-end detectors. The integration of the converters in the trackers front-ends needs to address also the material budget constraints. The impact of the DC-DC converters onto the material budget of the ATLAS tracker modules is discussed and mass reduction techniques are explored, leading to a compromise between electromagnetic compatibility and mass. Low mass shield implementations and Aluminum core inductors are proposed. Also, the impact on emitted noise due to a size reduction of critical components is discussed. Finally, material reduction techniques are discussed at the board layout and manufacturing levels.

  5. Efficient and ripple-mitigating dc-dc converter for residential fuel cell system

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yong [Danfoss Solar Inverters, Hardware, Jyllandsgade 28, 6400 Soenderborg (Denmark); Choi, Seeyoung [Digital Appliance Division, Samsung Electronics Co. Ltd., Maetan-3Dong, Suwon, Gyeonggi (Korea); Lee, Eunchul [Willings Co. Ltd., SK Ventium, 522 Dangjung-Dong, Gunpo-Si, Gyeonggi-Do (Korea)

    2009-01-15

    Proton exchange membrane fuel cell (PEMFC) systems for residential application require efficient and ripple-mitigating power conditioning system (PCS). The key point to reach it, is the design and control of the dc-dc converter. Based on the theoretical and experimental analysis of the traditional converter, this paper proposes a novel parallel-series full bridge (P-SFB) dc-dc converter, and improves its phase shifting scheme. This paper also proposes a novel controller for low frequency ripple current suppressing applied on the converter. The experimental results verify that, the dc-dc converter achieves a peak efficiency of 95.5%. Therefore PCS's maximum efficiency reaches 92.9%. And the input current ripple is reduced significantly with the new controller. (author)

  6. Critical conditions of saddle-node bifurcations in switching DC-DC converters

    Science.gov (United States)

    Fang, Chung-Chieh

    2013-08-01

    Although existence of multiple periodic orbits in some DC-DC converters have been known for decades, linking the multiple periodic orbits with the saddle-node bifurcation (SNB) is rarely reported. The SNB occurs in popular DC-DC converters, but it is generally reported as a strange instability. Recently, design-oriented instability critical conditions are of great interest. In this article, average, sampled-data and harmonic balance analyses are applied and they lead to equivalent results. Many new critical conditions are derived. They facilitate future research on the instability associated with multiple periodic orbits, sudden voltage jumps or disappearances of periodic orbits observed in DC-DC converters. The effects of various converter parameters on the instability can be readily seen from the derived critical conditions. New Nyquist-like plots are also proposed to predict or prevent the occurrence of the instability.

  7. Simulation and Implementation of Interleaved Boost DC-DC Converter for Fuel Cell Application

    Directory of Open Access Journals (Sweden)

    Ahmad Saudi Samosir

    2011-10-01

    Full Text Available This paper deals with a boost dc-dc converter for fuel cell application. In fuel cell electric vehicles application, a high power boost dc-dc converter is adopted to adjust the output voltage, current and power of fuel cell engine to meet the vehicle requirements. One of challenge in designing a boost converter for high power application is how to handle the high current at the input side. In this paper an interleaved boost dc-dc converter is proposed for current sharing on high power application. Moreover, this converter also reduces the fuel ripple current. Performance of the interleaved boost converter is tested through simulation and experimental results. Keywords: component; Interleaved Boost Converter; Fuel Cell Electric Vehicle; high power application.  

  8. Application handbook for a Standardized Control Module (SCM) for DC-DC converters, volume 1

    Science.gov (United States)

    Lee, F. C.; Mahmoud, M. F.; Yu, Y.

    1980-01-01

    The standardized control module (SCM) was developed for application in the buck, boost and buck/boost DC-DC converters. The SCM used multiple feedback loops to provide improved input line and output load regulation, stable feedback control system, good dynamic transient response and adaptive compensation of the control loop for changes in open loop gain and output filter time constraints. The necessary modeling and analysis tools to aid the design engineer in the application of the SCM to DC-DC Converters were developed. The SCM functional block diagram and the different analysis techniques were examined. The average time domain analysis technique was chosen as the basic analytical tool. The power stage transfer functions were developed for the buck, boost and buck/boost converters. The analog signal and digital signal processor transfer functions were developed for the three DC-DC Converter types using the constant on time, constant off time and constant frequency control laws.

  9. Optimized photovoltaic generator-water electrolyser coupling through a controlled DC-DC converter

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Valverde, R.; Miguel, C.; Urbina, A. [Universidad Politecnica de Cartagena, Departamento de Electronica, Tecnologia de Computadoras y Proyectos, Plaza del Hospital, 1, Cartagena, 30203 Murcia (Spain); Martinez-Bejar, R. [Universidad de Murcia, Departamento de Ingenieria de la Informacion y las Comunicaciones, Facultad de Informatica, Campus de Espinardo, 30071 Murcia (Spain)

    2008-10-15

    The coupling of a photovoltaic generator and an electrolyser is one of the most promising options for obtaining hydrogen from a renewable energy source. Both are well known technologies, however, since the high variability of the solar radiation, an efficient coupling still presents some challenges. Direct or through a DC-DC converter couplings are the options in isolated applications. In this work, three models, respectively, for a photovoltaic (PV) generator, a controlled DC-DC converter and a complete proton exchange membrane (PEM) electrolyser have been designed by using Matlab/Simulink. A PV-electrolyser specific algorithm to search for the optimum and safe working point for both elements is presented. Simulation results demonstrate that the use of a controlled DC-DC converter with the proposed algorithm shows better adaptability to the variable radiation conditions than the other coupling options. Therefore, it leads to a better compliance between the electrolyser and the sizing of the PV generator. (author)

  10. Test Results of Selected Commercial DC/DC Converters under Cryogenic Temperatures - A Digest

    Science.gov (United States)

    Patterson, Richard; Hammoud, Ahmad

    2010-01-01

    DC/DC converters are widely used in space power systems in the areas of power management and distribution, signal conditioning, and motor control. Design of DC/DC converters to survive cryogenic temperatures will improve the power system performance, simplify design, and reduce development and launch costs. In this work, the performance of nine COTS modular, low-tomedium power DC/DC converters was investigated under cryogenic temperatures. The converters were evaluated in terms of their output regulation, efficiency, and input and output currents. At a given temperature, these properties were obtained at various input voltages and at different load levels. A summary on the performance of the tested converters was given. More comprehensive testing and in-depth analysis of performance under long-term exposure to extreme temperatures are deemed necessary to establish the suitability of these and other devices for use in the harsh environment of space exploration missions.

  11. Advanced DC/DC Converters Towards Higher Volumetric Efficiencies For Space Applications

    Science.gov (United States)

    Shaw, Harry; Shue, Jack; Liu, David; Wang, Bright; Plante, Jeanette

    2005-01-01

    A new emphasis on planetary exploration by NASA drives the need for small, high power DC/DC converters which are functionally modular. NASA GSFC and other government space organizations are supporting technology development in the DC/DC converter area to both meet new needs and to promote more sources of supply. New technologies which enable miniaturization such as embedded passive technologies and thermal management using high thermal conductivity materials are features of the new designs. Construction of some simple DC/DC converter core circuits using embedded components was found to be successful for increasing volumetric efficiency to 37 W/inch. The embedded passives were also able to perform satisfactorily in this application in cryogenic temperatures.

  12. Ultra-high Efficiency DC-DC Converter using GaN Devices

    DEFF Research Database (Denmark)

    Ramachandran, Rakesh

    2016-01-01

    The demands for high efficiency dc-dc power converters are increasing day by day in various applications such as telecommunication, data-centers, electric vehicles and various renewable energy systems. Silicon (Si) has been used as the semiconductor material in majority of the power devices...... properties of GaN devices can be utilized in power converters to make them more compact and highly efficient. This thesis entitled “Ultra-high Efficiency DC-DC Converter using GaN devices” focuses on achieving ultra-high conversion efficiency in an isolated dc-dc converter by the optimal utilization of Ga......N devices. Simple replacement of Si or SiC devices with GaN devices in the converter will not give an expected increase in efficiency or any improvement in the performance of the converter. The use of GaN devices has defined another dimension in the design of power converters, which mainly deals...

  13. Efficiency Enhancement of DC to DC Multilevel Boost Converter and Its Applications

    Directory of Open Access Journals (Sweden)

    R. Ravikumar

    2015-03-01

    Full Text Available The aim of this study is to propose a experimental verification for single-phase to three phase drive system composed of two parallel single-phase rectifiers, a three-phase inverter and an induction motor. Apart from traditional application in dc motor drives, new applications of BDC include energy storage in renewable energy systems, fuel cell energy systems, Hybrid Electric Vehicles (HEV and Uninterruptible Power Supplies (UPS. A dc-dc converter is always required to allow energy exchange between storage device and the rest of system. In HEV applications, BDCs are required to link different dc voltage buses and transfer energy between them. A non-isolated bi-directional dc-dc converters is used in our project to achieve better efficiency.

  14. Aspectos morfo-anatômicos da folha de Baccharis dracunculifolia DC. (Asteraceae visando a identificação da origem botânica da própolis Morphological and anatomical aspects of the leaf of Baccharis dracunculifolia DC. (Asteraceae as regards to the identification of the botanical origin of propolis

    Directory of Open Access Journals (Sweden)

    Virginia del Carmen Oliveira

    1998-01-01

    Full Text Available Foi estudada a anatomia da folha, em diferentes fases de desenvolvimento, a partir do ápice caulinar, de B. dracunculifolia para caracterizar as estruturas secretoras e tricomas que podem ser utilizados como indicadores na determinação da origem botânica da própolis produzida por Apis mellifera. O material foi coletado no Município de Jaboticatubas, MG, onde estão instaladas colmeias experimentais. A espécie estudada apresenta primórdios foliares densamente recobertos por tricomas glandulares e tectores. Os tricomas glandulares são freqüentes em folhas jovens e raros em folhas adultas. A folha adulta é anfi-estomática. O mesofilo é composto por parênquima paliçádico, escasso parênquima lacunoso e canais secretores associados ao floema. Os fragmentos foliares, estômatos, tricomas glandulares e tricomas tectores encontrados em amostras de própolis são semelhantes aos observados em folhas de B. dracunculifolia.The leaf anatomy of B. dracunculifolia, in different developmental stages, was studied, with the purpose of characterizing the secretory structures that can be used as indicators for determining of the botanical origin of propolis produced by Apis mellifera. The material was collected in the Municipal district of Jaboticatubas, Minas Gerais State, where experimental hives were installed. The studied species are characterized by having the surface of the youngest leaves densely covered by glandular and non-glandular trichomes. The glandular trichomes are abundant in the early stages of leaf growth and uncommon in mature leaves. The mature leaf is amphistomatic. The mesophyll consists of palisade cells, scarce spongy parenchyma and secretory ducts associated to the phloem. The leaf fragments, stomata, glandular trichomes and non-glandular trichomes present in propolis samples are similar to those found in B. dracunculifolia leaves.

  15. Physicochemical characteristics of the essential oils of Baccharis dracunculifolia and Baccharis uncinella D.C. (Asteraceae Características físico-químicas dos óleos essenciais de Baccharis dracunculifolia e Baccharis uncinella D.C. (Asteraceae

    Directory of Open Access Journals (Sweden)

    Kely Cristina Fabiane

    2008-06-01

    Full Text Available The essential oils of Baccharis dracunculifolia and Baccharis uncinella, which were obtained by hydrodistillation, were physically and chemically characterized for their yield, relative density (d20(20, refraction index, solubility in ethanol and chemical composition through gas chromatography coupled to mass spectrophotometry (GC/MS. The results showed a yield of 1.5 and 1.65 mL/100g-1, relative density (d20(20 of 0.9151 and 0.9147, refraction index of 1.4593 and 1.4602, rotatory power of +1.99 and +2.18. Solubility in 70% ethanol was 3.0, in 80% ethanol was 1.0 and in 96.5% ethanol was 1.0, for the oils of B. dracunculifolia and B. uncinella respectively. The evaluations in gas chromatography coupled to mass spectrophotometry showed that the oils studied are similar, presenting 26 constituents among which β-pinene, ε-nerolidol, limonene and spathulenol are highlighted.Os óleos essenciais de Baccharis dracunculifolia e Baccharis uncinella, obtidos por hidrodestilação, foram caracterizados físico e quimicamente em relação ao seu rendimento, sua densidade relativa (d20(20, seu índice de refração, sua solubilidade em etanol e sua composição química por meio de cromatografia gasosa acoplada à espectrometria de massas (CG/EM. Os resultados mostraram um rendimento de 1,5 e 1,65 mL/100g-1, uma densidade relativa (d20(20 de 0,9151 e 0,9147, um índice de refração de 1,4593 e 1,4602, um poder rotatório de +1,99 e +2,18, a sua solubilidade em etanol 70% foi 3,0, em etanol 80% foi 1,0 e em etanol 96,5% também foi de 1,0, para o óleo de B. dracunculifolia e B. uncinella, respectivamente. Os resultados mostraram que os óleos avaliados são semelhantes, apresentando 26 compostos, com destaque para β-pineno, ε-nerolidol, limoneno e espatulenol.

  16. The DC-DC converter reduces its size and increases its efficiency; Le convertisseur DC-DC reduit sa taille et augmente son rendement

    Energy Technology Data Exchange (ETDEWEB)

    Feste, J.P.

    2000-03-01

    The DC to DC converters built by the US SynQor company use a dual stage conversion technique. One stage is devoted to regulation and the other to insulation. This technique allows to combine a high efficiency (up to 90%) with small dimensions. Instead of the classical Schottky diodes, a synchronous MOSFET is used for the rectification of the low voltage current. A simple air flow is required for the cooling of these converters. Short paper. (J.S.)

  17. Solid-State dc Circuit Breaker

    Science.gov (United States)

    Harvey, P.

    1983-01-01

    Circuit breaker with no moving parts protects direct-current (dc) loads. Current which circuit breaker opens (trip current) is adjustable and so is time delay before breaker trips. Forward voltage drop rises from 0.6 to 1.2 V as current rises to trip point. Breaker has two terminals, like fuse, therefore replaces fuse in dc circuit. Powered by circuit it protects and reset by either turning off power source or disconnecting load.

  18. ALELOPATIA DE Arctium minus BERNH (ASTERACEAE NA GERMINAÇÃO E CRESCIMENTO RADICULAR DE SORGO E PEPINO

    Directory of Open Access Journals (Sweden)

    Valdenir José Belinelo

    2008-01-01

    Full Text Available The objectives of this work were identified and characterize the allelopatic activity of extracts obtained from Arctium minus (Hill Bernh (Asteraceae. The fitotoxic activity of organic extracts (1 e 100 mg.L-1 and aqueous extract (5,00 e 0,05% m/v on the germination and radicular growth of the monocotyledon Sorghum bicolor L. (sorghum, and the dicotyledon Cucumis sativus L. (cucumber were evaluated. The results showed the presence of allelopatic activity variable in according to the extract concentration and with the target plant. The intensity of induced inhibitory effect was higher for the ethanolic extract in concentration of 100 mg.L-1 for Sorghum bicolor L. The results also indicates the existence of the potential use of Arctium minus (Hill Bernh ethanolic extract as a natural herbicide and open perspectives for the research of the constituent(s with higher allelopatic activity.

  19. Cytological study on the genus Syncalathium (Asteraceae-Lactuceae), an endemic taxon to alpine scree of the Sino-Himalayas

    Institute of Scientific and Technical Information of China (English)

    Jian-Wen ZHANG; Ze-Long NIE; Hang SUN

    2009-01-01

    Cytological characters of four species in Syncalathium (Asteraceae: Lactuceae), a small genus with six identified species endemic to alpine scree of the Sino-Himalayan region, are surveyed in this report. Three species ( Syncalathium pilosum, Syncalathium chrysocephalum, and Syncalathium disciforme ) are examined for the first time. Combined with our previous counts, five species have been cytologically investigated from the genus and the results indicated that all species are diploid with the basic somatic chromosome number of x=8. The karyotype asymmetry of Syncalathium souliei is 2A, distinct from the other four species of 1 A, and the remaining species are divided into two subgroups with different karyotypes, consistent with their morphological features. The significance of the cytological evolution of Syncalathium is briefly discussed.

  20. Systematic of genera Pulicaria Gaertn. and Platycheteae Boiss. from tribe Inuleae s.str (Asteraceae in Iran

    Directory of Open Access Journals (Sweden)

    Peyman Zarin

    2010-04-01

    Full Text Available The genus Pulicaria Gaertn belongs to the tribe Inuleae (Asteraceae. This genus includes five species in Iran (P. dysenterica, P. vulgaris, P. Arabica, P. gnaphalodes and P. salvifolia. The most diagnostic morphological characteristics were kind of pappus, achene, corolla, phyllaries and form of leafs. In the recent study by Anderberg, focusing on the close relationship between the genus Pulicaria and platychaete, they have been announced synonymous. Platychaete includes five species in Iran (P. glucescens, P. carnosa, P. velutina, P. mucronifolia and P. aucheri. In this study the relationships between them were confirmed and therefore, the Anderberg’s view of convergence of the two genera was attested. Also, species identification key, phenogram and distribution map in Iran were provided and discussed.

  1. Distribución geográfica y riqueza del género Cosmos (Asteraceae: Coreopsideae)

    OpenAIRE

    Georgina Vargas-Amado; Arturo Castro-Castro; Mollie Harker; José Luis Villaseñor; Enrique Ortiz; Aarón Rodríguez

    2013-01-01

    Cosmos es uno de los géneros monofiléticos más diversos de la tribu Coreopsideae (Asteraceae). El grupo incluye 35 especies y 4 taxa infraespecíficos restringidos al continente americano. El objetivo del presente trabajo fue evaluar la distribución geográfica y la riqueza de Cosmos a través de un sistema de información geográfica (SIG). Se estimó el área de distribución geográfica de los taxa con más de un registro. También se evaluó la riqueza de las especies de Cosmos por región política, p...

  2. [Diversity of Plants Belonging to the Genus Ligularia (Asteraceae) Based on Terpenoids and Synthetic Studies on Some Terpenoids].

    Science.gov (United States)

    Tori, Motoo

    2016-01-01

    The terpenoid constituents of Ligularia virgaurea (30 samples), Ligularia pleurocaulis (8 samples), Ligularia dictyoneura (8 samples), Ligularia brassicoides (5 samples), Ligularia lingiana (1 sample), and Ligularia liatroides (1 sample)(all belonging to section Senecillis of Ligularia, Asteraceae and collected in Yunnan, Sichuan, Qinghai, and Gansu provinces, China), from which 220 compounds were isolated, including 113 novel ones, are reviewed. Five chemotypes were identified in L. virgaurea based on their chemical constituents, while three clades were detected from the base sequences. Although intra-specific diversity was found in L. virgaurea, more samples were needed of other species in order to reach a definite conclusion. Inter-specific diversity was also examined in section Senecillis but was restricted due to the scarcity of samples. Synthetic studies on chiral natural products to determine their absolute configurations, especially those of riccardiphenols A and B as well as crispatanolide, which were all isolated from the liverwort, are briefly reviewed.

  3. Evaluation of antimalarial, free-radical-scavenging and insecticidal activities of Artemisia scoparia and A. Spicigera, Asteraceae

    Directory of Open Access Journals (Sweden)

    Fariba H. Afshar

    2011-12-01

    Full Text Available Artemisia species (Asteraceae, widespread throughout the world, are a group of important medicinal plants. The extracts of two medicinal plants of this genus, Artemisia scoparia Waldst. & Kit. and A. spicigera C. Koch, were evaluated for potential antimalarial, free-radical-scavenging and insecticidal properties, using the heme biocrystallisation and inhibition assay, the DPPH assay and the contact toxicity bioassay using the pest Tribolium castaneum, respectively. The methanol extracts of both species showed strong free-radical-scavenging activity and the RC50 values were 0.0317 and 0.0458 mg/mL, respectively, for A. scoparia and A. spicigera. The dichloromethane extracts of both species displayed a moderate level of potential antimalarial activity providing IC50 at 0.778 and 0.999 mg/mL for A. scoparia and A. spicigera, respectively. Both species of Artemisia showed insecticidal properties. However, A. spicigera was more effective than A. scoparia.

  4. Brushless DC Motors, Velocity and Position Control of the Brushless DC Motor.

    Science.gov (United States)

    1986-06-01

    DC motor was designed using the Hall effect sensors. In addition, the position control of the brushless DC motor was developed using an optical encoder to sense angular position changes and a microprocessor to provide the desired position control. A Pittman 5111 wdg 1 brushless DC motor was used for this study. The design of the digital tachometer and pulse width modulator for velocity control and the design of the Z-80 based microprocessor controller and software design are described in

  5. The application of standardized control and interface circuits to three dc to dc power converters.

    Science.gov (United States)

    Yu, Y.; Biess, J. J.; Schoenfeld, A. D.; Lalli, V. R.

    1973-01-01

    Standardized control and interface circuits were applied to the three most commonly used dc to dc converters: the buck-boost converter, the series-switching buck regulator, and the pulse-modulated parallel inverter. The two-loop ASDTIC regulation control concept was implemented by using a common analog control signal processor and a novel digital control signal processor. This resulted in control circuit standardization and superior static and dynamic performance of the three dc-to-dc converters. Power components stress control, through active peak current limiting and recovery of switching losses, was applied to enhance reliability and converter efficiency.

  6. Model predictive control of bidirectional isolated DC-DC converter for energy conversion system

    Science.gov (United States)

    Akter, Parvez; Uddin, Muslem; Mekhilef, Saad; Tan, Nadia Mei Lin; Akagi, Hirofumi

    2015-08-01

    Model predictive control (MPC) is a powerful and emerging control algorithm in the field of power converters and energy conversion systems. This paper proposes a model predictive algorithm to control the power flow between the high-voltage and low-voltage DC buses of a bidirectional isolated full-bridge DC-DC converter. The predictive control algorithm utilises the discrete nature of the power converters and predicts the future nature of the system, which are compared with the references to calculate the cost function. The switching state that minimises the cost function is selected for firing the converter in the next sampling time period. The proposed MPC bidirectional DC-DC converter is simulated with MATLAB/Simulink and further verified with a 2.5 kW experimental configuration. Both the simulation and experimental results confirm that the proposed MPC algorithm of the DC-DC converter reduces reactive power by avoiding the phase shift between primary and secondary sides of the high-frequency transformer and allow power transfer with unity power factor. Finally, an efficiency comparison is performed between the MPC and dual-phase-shift-based pulse-width modulation controlled DC-DC converter which ensures the effectiveness of the MPC controller.

  7. Design of the DC-DC power stage of the capacitor charger for MAXIDISCAP power converters

    CERN Document Server

    Cravero, Jean-Marc

    2013-01-01

    This technical report presents the design of the DC-DC power stage of the capacitor charger for MAXIDISCAP power converters. The power stage is based on a half bridge series resonant converter in Discontinuous Conduction Mode (DCM). This simple and robust topology allows obtaining a current source behavior with a low switching losses power stage. The associated control stage is implemented using a commercial controller which has differenti nternal circuits that allows a high integration of the converter control system. The report presents the design and tuning criteria for the DC-DC converter, including the power stage and the control system.

  8. A Reduced-Part, Triple-Voltage DC-DC Converter for Electric Vehicle Power Management

    Energy Technology Data Exchange (ETDEWEB)

    Su, Gui-Jia [ORNL; Tang, Lixin [ORNL

    2007-01-01

    Electrical power systems in future hybrid and fuel cell vehicles may consist of three voltage nets; 14 V, 42 V and high voltage (>200 V) buses. A soft-switched, bi-directional dc-dc converter using only four switches was proposed for interconnecting the three nets. This paper presents a reduced- part dc-dc converter, which decreases the converter cost while retaining all the favorable features of the original topology. Simulation and experimental data are included to verify a simple power flow control scheme.

  9. High-Voltage DC-DC Converter Topology for PV Energy Utilization - Investigation and Implementation

    DEFF Research Database (Denmark)

    Sanjeevikumar, Padmanaban; Blaabjerg, Frede; Wheeler, Patrick

    2017-01-01

    This paper exploited the utilization of photovoltaic (PV) energy system with high-voltage (HV) output DC-DC converter. Classical boost converters are used for both renewable energy integration and HV applications, but limited by reducing output/efficiency in performance. Moreover, as parasitic...... elements suppress the power transfer ratio, converter needs to maximize the PV energy utilization. This investigation study focused to include additional parasitic elements (voltage-lift technique) to a standard DC-DC buck converter and to overcome all the above drawbacks to maximize the PV power...

  10. Laboratory manual for pulse-width modulated DC-DC power converters

    CERN Document Server

    Kazimierczuk, Marian K

    2015-01-01

    Designed to complement a range of power electronics study resources, this unique lab manual helps students to gain a deep understanding of the operation, modeling, analysis, design, and performance of pulse-width modulated (PWM) DC-DC power converters.  Exercises focus on three essential areas of power electronics: open-loop power stages; small-signal modeling, design of feedback loops and PWM DC-DC converter control schemes; and semiconductor devices such as silicon, silicon carbide and gallium nitride. Meeting the standards required by industrial employers, the lab manual combines program

  11. Efficiency and Regulation of Commercial Low Power DC/DC Converter Modules at Low Temperatures

    Science.gov (United States)

    Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard L.

    2000-01-01

    DC/DC converters that are capable of operating at cryogenic temperatures are anticipated to play an important role in the power systems of future NASA deep space missions. Design of these converters to survive cryogenic temperatures will improve the power system performance, and reduce development and launch costs. At the NASA Glenn Research Center Low Temperature Electronics Laboratory, several commercial off-the-shelf dc/dc converter modules were evaluated for their low temperature performance. Various parameters were investigated as a function of temperature, in the range of 20 C to -190 C. Data pertaining to the efficiency and voltage regulation of the tested converters is presented and discussed.

  12. High power density dc/dc converter: Component selection and design

    Science.gov (United States)

    Divan, Deepakraj M.

    1989-01-01

    Further work pertaining to design considerations for the new high power, high frequency dc/dc converters is discussed. The goal of the project is the development of high power, high power density dc/dc converters at power levels in the multi-kilowatt to megawatt range for aerospace applications. The prototype converter is rated for 50 kW at a switching frequency of 50 kHz, with an input voltage of 200 Vdc and an output of 2000 Vdc. The overall power density must be in the vicinity of 0.2 to 0.3 kg/kW.

  13. Analysis of high voltage step-up nonisolated DC-DC boost converters

    Science.gov (United States)

    Alisson Alencar Freitas, Antônio; Lessa Tofoli, Fernando; Junior, Edilson Mineiro Sá; Daher, Sergio; Antunes, Fernando Luiz Marcelo

    2016-05-01

    A high voltage step-up nonisolated DC-DC converter based on coupled inductors suitable to photovoltaic (PV) systems applications is proposed in this paper. Considering that numerous approaches exist to extend the voltage conversion ratio of DC-DC converters that do not use transformers, a detailed comparison is also presented among the proposed converter and other popular topologies such as the conventional boost converter and the quadratic boost converter. The qualitative analysis of the coupled-inductor-based topology is developed so that a design procedure can be obtained, from which an experimental prototype is implemented to validate the theoretical assumptions.

  14. Interleaved DC-DC Converter with Discrete Duty Cycle and Open Loop Control

    Science.gov (United States)

    Kroics, K.; Sokolovs, A.

    2016-08-01

    The authors present the control principle of the multiphase interleaved DC-DC converter that can be used to vastly reduce output current ripple of the converter. The control algorithm can be easily implemented by using microcontroller without current loop in each phase. The converter works in discontinuous conduction mode (DCM) but close to boundary conduction mode (BCM). The DC-DC converter with such a control algorithm is useful in applications that do not require precise current adjustment. The prototype of the converter has been built. The experimental results of the current ripple are presented in the paper.

  15. Interleaved DC-DC Converter with Discrete Duty Cycle and Open Loop Control

    Directory of Open Access Journals (Sweden)

    Kroics K.

    2016-08-01

    Full Text Available The authors present the control principle of the multiphase interleaved DC-DC converter that can be used to vastly reduce output current ripple of the converter. The control algorithm can be easily implemented by using microcontroller without current loop in each phase. The converter works in discontinuous conduction mode (DCM but close to boundary conduction mode (BCM. The DC-DC converter with such a control algorithm is useful in applications that do not require precise current adjustment. The prototype of the converter has been built. The experimental results of the current ripple are presented in the paper.

  16. Preliminary phytochemical screening and In vitro antioxidant activities of the aqueous extract of Helichrysum longifolium DC

    Directory of Open Access Journals (Sweden)

    Okoh Anthony I

    2010-05-01

    Full Text Available Abstract Background Many oxidative stress related diseases are as a result of accumulation of free radicals in the body. A lot of researches are going on worldwide directed towards finding natural antioxidants of plants origins. The aims of this study were to evaluate in vitro antioxidant activities and to screen for phytochemical constituents of Helichrysum longifolium DC. [Family Asteraceae] aqueous crude extract. Methods We assessed the antioxidant potential and phytochemical constituents of crude aqueous extract of Helichrysum longifolium using tests involving inhibition of superoxide anions, DPPH, H2O2, NO and ABTS. The flavonoid, proanthocyanidin and phenolic contents of the extract were also determined using standard phytochemical reaction methods. Results Phytochemical analyses revealed the presence of tannins, flavonoids, steroids and saponins. The total phenolic content of the aqueous leaf extract was 0.499 mg gallic acid equivalent/g of extract powder. The total flavonoid and proanthocyanidin contents of the plant were 0.705 and 0.005 mg gallic acid equivalent/g of extract powder respectively. The percentage inhibition of lipid peroxide at the initial stage of oxidation showed antioxidant activity of 87% compared to those of BHT (84.6% and gallic acid (96%. Also, the percentage inhibition of malondialdehyde by the extract showed percentage inhibition of 78% comparable to those of BHT (72.24% and Gallic (94.82%. Conclusions Our findings provide evidence that the crude aqueous extract of H. longifolium is a potential source of natural antioxidants, and this justified its uses in folkloric medicines.

  17. Contribution to the Knowledge of the Alien Flora from Romania: Rudbeckia triloba L. and Senecio inaequidens DC.

    Directory of Open Access Journals (Sweden)

    Culita SIRBU

    2010-06-01

    Full Text Available Two alien species new to the Romanian flora, namely Rudbeckia triloba L. and Senecio inaequidens DC (Asteraceae family have been recorded during 2004-2009 period in different places of Moldavia and Maramures provinces (Romania. Rudbeckia triloba, native of North America, is a perennial species, 150 cm of length, with glabrate stems, blades ovate to subcordate or elliptic leaves, which present serrate margins. The capitula (10-30 is long pedunculate, with conic to subhemispheric receptacles (8-150-15 mm; with the paleae dark purple (5-6.5 mm. The ray florets are 7-15; the laminae is yellow-orange, linear to oblanceolate, 8-17 3-8 mm. The other species, Senecio inaequidens, is native of South Africa and it is a perennial herb. The cross pollination with non-specialized insects ensures the production of a large number of seeds, but self-pollination populations have also been reported, increasing the chances of the species to colonize new territory, where other sources of pollen were missing. Though for the moment these two species are sporadically met among the Romanian flora, at least one of them (Senecio inaequidens might become in the near future a threat to the natural or agricultural national ecosystems.

  18. Anatomia da madeira de duas espécies do gênero Heterothalamus Lessing (Asteraceae nativas no Rio Grande do Sul

    Directory of Open Access Journals (Sweden)

    Luciano Denardi

    Full Text Available O presente trabalho descreve a anatomia da madeira de Heterothalamus alienus e Heterothalamus rupestris (Astereae – Asteraceae, como parte do estudo do xilema secundário do referido gênero. Para ambas as espécies, foram confirmados detalhes anatômicos mencionados na literatura para a família Asteraceae, como vasos tipicamente pequenos e agrupados em padrão dendrítico, placas de perfuração invariavelmente simples e parênquima paratraqueal. Heterothalamus alienus possui espessamentos espiralados nos vasos lenhosos e parênquima axial vasicêntrico estratificado. Heterothalamus rupestris distingue-se pela ausência de espessamentos espiralados nos vasos e pelo parênquima paratraqueal vasicêntrico a unilateral. São fornecidas fotomicrografias, dados quantitativos de características anatômicas e uma comparação entre a madeira das duas espécies.

  19. Design of current source DC/DC converter and inverter for 2kW fuel cell application

    DEFF Research Database (Denmark)

    Andreiciks, A.; Steiks, I.; Krievs, O.

    2013-01-01

    of a DC/DC converter and an inverter. In this paper a detailed simulation study of such interfacing converter system comprising a double inductor push-pull step-up DC/DC converter and a cascaded H-bridge inverter has been carried out and further confirmed with experimental results. The power converter...

  20. Research on Two-channel Interleaved Two-stage Paralleled Buck DC-DC Converter for Plasma Cutting Power Supply

    DEFF Research Database (Denmark)

    Yang, Xi-jun; Qu, Hao; Yao, Chen

    2014-01-01

    As for high power plasma power supply, due to high efficiency and flexibility, multi-channel interleaved multi-stage paralleled Buck DC-DC Converter becomes the first choice. In the paper, two-channel interleaved two- stage paralleled Buck DC-DC Converter powered by three-phase AC power supply...

  1. Novel Step-Up DC/DC Converter with No Right Half Plane Zero and Reduced Switched Voltage Stress Characteristics

    DEFF Research Database (Denmark)

    Mostaan, Ali; Alizadeh, Ebrahim; Soltani, Mohsen

    2014-01-01

    Novel step-up DC/DC converter is introduced in this paper. This converter is realized with adding the switched capacitor voltage multiplier cell to the three switch step-down DC/DC converter that has been proposed in the literature. The proposed converter is analyzed in the steady state and the v...

  2. Comparative efficiency evaluation of buck and hybrid buck DC-DC converters for automotive applications

    DEFF Research Database (Denmark)

    Pelan, Ovidiu; Cornea, Octavian; Muntean, Nicolae

    2014-01-01

    This paper presents and discusses design considerations and efficiency investigation of a conventional step-down and a hybrid switched-capacitor DC-DC converter. Three MOSFETs with low on-resistance have been tested for each converter in order to find the most adequate switch for this application...

  3. Single Event Burnout in DC-DC Converters for the LHC Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Claudio H. Rivetta et al.

    2001-09-24

    High voltage transistors in DC-DC converters are prone to catastrophic Single Event Burnout in the LHC radiation environment. This paper presents a systematic methodology to analyze single event effects sensitivity in converters and proposes solutions based on de-rating input voltage and output current or voltage.

  4. Very High Frequency Resonant DC/DC Converters for LED Lighting

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

    2013-01-01

    This paper presents a very high frequency DC/DC converter for LED lighting. Several resonant topologies are compared and their usability discussed. At the end the resonant SEPIC converter is chosen based on the achievable power density and total bill of material. Simulations of a 51 MHz converter...

  5. Area-Efficiency Trade-Offs in Integrated Switched-Capacitor DC-DC Converters

    DEFF Research Database (Denmark)

    Spliid, Frederik Monrad; Larsen, Dennis Øland; Knott, Arnold

    2016-01-01

    This paper analyzes the relationship between efficiency and chip area in a fully integrated switched capacitor voltage divider dc-dc converter implemented in 180nm-technology and a 1/2 topology. A numerical algorithm for choosing the optimal sizes of individual components, in terms of power loss...

  6. A novel DC-DC convertor using LTCC technology for magnetic integration application

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Z Q [Research Institutes, University of Electronic Science and Technology of China, Chengdu (China); Shi, Y; Guo, H P; Yang, B C, E-mail: nanterxu@uestc.edu.cn [State key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu (China)

    2011-01-01

    A compact DC-DC convertor is proposed and fabricated in multilayer ferrite substrate using LTCC technology. The spiral conductors are buried into the ferrite substrate with a multilayer 3-D structure to reduce the volume of convertor. The passive integration of magnetic components and surface circuitry are achieved in a whole substrate and the size of module can be reduced markedly. The whole height of module is only 3mm, 1/3 of the height of conventional modules. Testing results indicate that the performance of the module is excellent in Point-of-Load (POL) field. The step-down DC-DC converter converts input voltage of 5V to output voltage of 3.3V. It is confirmed that the maximum conversion efficiency of 93.2% is sufficient for actual DC-DC converter application. Such a compact DC-DC convertor provides a compact, low cost and high reliability approach for power supply and magnetic integration application.

  7. Five-Level Active-Neutral-Point-Clamped DC/DC Converter

    DEFF Research Database (Denmark)

    Liu, Dong; Deng, Fujin; Chen, Zhe

    Multi-level converters are getting more and more attentions because of their obvious merits such as lower voltage stress and harmonic, smaller size of output filters, and so on. In this paper, a five-level active-neutral-point-clamped (5L-ANPC) dc/dc converter is proposed for power transfer...

  8. DC-DC conversion powering schemes for the CMS tracker at Super-LHC

    Energy Technology Data Exchange (ETDEWEB)

    Klein, K; Feld, L; Jussen, R; Karpinski, W; Merz, J; Sammet, J, E-mail: katja.klein@cern.c [I. Physikalisches Institut B, RWTH Aachen University, Aachen (Germany)

    2010-07-15

    The CMS experiment at the Large Hadron Collider (LHC) at CERN, Geneva, houses the largest silicon strip tracker ever built. For the foreseen luminosity upgrade of the LHC, the Super-LHC, however, a completely new silicon tracker will have to be constructed. One out of several major improvements currently under consideration is the implementation of a track trigger, with tracking information being provided to the first level trigger. Such an intelligent tracker design, utilising fast digital readout electronics, will most certainly lead to an increased power consumption, compared to today's tracker. In combination with the desire to reduce the amount of passive material inside the tracking volume and the impracticality to exchange or even add additional supply cables, a novel powering scheme will be inevitable. In this article a powering scheme based on DC-DC conversion is proposed, and requirements for the DC-DC converters are discussed. Studies of important DC-DC converter quantities such as the power efficiency, conducted and radiated noise levels, and material budget are presented, and a possible implementation of DC-DC buck converters into one proposed track trigger layout is sketched.

  9. Computer-aided analysis and simulation of switched dc-dc converters

    Science.gov (United States)

    Lee, F. C.; Yu, Y.

    1978-01-01

    State space techniques are employed to derive an equivalent nonlinear recurrent time-domain model that describes the switched dc-dc converter behavior exactly. This model is employed effectively to analyze both large signal behavior by propagating the recurrence equation and matching boundary conditions through digital computation and small signal behavior by linearizing it about the equilibrium state.

  10. Low noise DC to DC converters for the sLHC experiments

    Energy Technology Data Exchange (ETDEWEB)

    Allongue, B; Blanchot, G; Faccio, F; Fuentes, C; Michelis, S; Orlandi, S, E-mail: georges.blanchot@cern.c [CERN, Route de Meyrin, CH-1211 Geneva 23 (Switzerland)

    2010-11-15

    The development of front-end systems for the ATLAS tracker at the sLHC is now in progress and the availability of radiation tolerant buck converter ASICs enables the implementation of DC to DC converter based powering schemes. The front-end systems powered in this manner will be exposed to the radiated and conducted noise emitted by the converters. The electromagnetic compatibility between DC to DC converters and ATLAS short strip tracker hybrid prototypes has been studied with specific susceptibility tests. Different DC to DC converter prototypes have been designed following a noise optimization methodology to match the noise requirements of these front-end systems. The DC to DC converter developed in this manner presents a negligible emission of noise that was confirmed by system tests on an ATLAS tracker front-end module prototype. As a result of this, power converters can now be integrated in close vicinity of front-end chips without compromising their overall noise performance.

  11. A DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

    Science.gov (United States)

    Feld, L.; Fleck, M.; Friedrichs, M.; Hensch, R.; Karpinski, W.; Klein, K.; Sammet, J.; Wlochal, M.

    2013-02-01

    The CMS pixel detector was designed for a nominal instantaneous LHC luminosity of 1ṡ1034 cm-2s-1. During Phase-1 of the LHC upgrade, the instantaneous luminosity will be increased to about twice this value. To preserve the excellent performance of the pixel detector despite the increase in particle rates and track densities, the CMS Collaboration foresees the exchange of its pixel detector in the shutdown 2016/2017. The new pixel detector will be improved in many respects, and will comprise twice the number of readout channels. A powering scheme based on DC-DC conversion will be adopted, which will enable the provision of the required power with the present cable plant. The powering scheme of the CMS pixel detector will be described, and the performance of prototype DC-DC buck converters will be presented, including power efficiency, system tests with DC-DC converters and pixel modules, thermal management, reliability at low temperature, and studies of potential frequency locking between DC-DC converters.

  12. Operation and control of a DC-grid offshore wind farm under DC transmission system faults

    DEFF Research Database (Denmark)

    Deng, Fujin; Chen, Zhe

    2013-01-01

    So far, all existing offshore wind farms have an ac collection system, and the collected power in the offshore wind farm is sent to an onshore ac grid through high-voltage ac (HVAC) or DC (HVDC) transmission lines. However, future of fshore wind farms may use dc also for power collection. Consequ...

  13. A Bidirectional Multi-Port DC-DC Converter Integrating Voltage Equalizer

    DEFF Research Database (Denmark)

    Chen, Jianfei; Hou, Shiying; Deng, Fujin

    2015-01-01

    with a uniform voltage level while eliminating the voltage imbalance. In addition, high step-down and step-up ratios with low component voltage stress can be achieved in the proposed converter. A bidirectional four-port dc-dc converter is presented to do theoretical analysis for the voltage equalization of three...

  14. DC-DC converter with a wide load range and a wide input-voltage range

    NARCIS (Netherlands)

    Ting, Y.

    2015-01-01

    This thesis investigated the possibility of increasing the efficiency of a DC-DC converter over a wide load range and a wide input-voltage range based on the Single Active Bridge (SAB) topology with two approaches. The first approach involved making changes to the topology whereas the second made us

  15. Modelling, Simulation and Construction of a DC/DC Boost Power Converter: A School Experimental System

    Science.gov (United States)

    Silva-Ortigoza, R.; Silva-Ortigoza, G.; Hernandez-Guzman, V. M.; Saldana-Gonzalez, G.; Marcelino-Aranda, M.; Marciano-Melchor, M.

    2012-01-01

    We introduce a dc/dc boost power converter as a didactic prototype intended to support courses on electric circuit analysis experimentally. The corresponding mathematical model is obtained, the converter is designed and an experimental setup is described, constructed and tested. Simplicity of construction as well as low cost of components renders…

  16. A Novel Quasi-SEPIC High-Voltage Boost DC-DC Converter

    DEFF Research Database (Denmark)

    Siwakoti, Yam Prasad; N. Soltani, Mohsen; Mostaan, Ali

    2017-01-01

    This paper proposes a modified coupled-inductor SEPIC dc-dc converter for low power and high voltage gain applications such as for piezoelectric drive systems. The converter uses the same components as of SEPIC converter with an additional diode. Compared to conventional topologies with similar v...

  17. Trans-inverse (Tx−1) high step-up DC-DC converter

    DEFF Research Database (Denmark)

    Siwakoti, Yam Prasad; Blaabjerg, Frede; Loh, Poh Chiang

    2015-01-01

    In this paper, a new magnetically coupled single-switch non-isolated dc-dc converter with a high voltage gain is proposed. The new topology utilizes a transformer to boost the output voltage. However, unlike other converter topologies with transformer or coupled magnetics, the voltage gain in the...

  18. Ultra-Step-Up DC-DC Converter with Integrated Autotransformer and Coupled Inductor

    DEFF Research Database (Denmark)

    Siwakoti, Yam Prasad; Blaabjerg, Frede; Loh, Poh Chiang

    2016-01-01

    This paper introduces a new single-switch nonisolated dc-dc converter with very high voltage transfer ratio and reduced semiconductor voltage stress. The converter utilizes an integrated autotransformer and a coupled inductor on the same core to achieve a high step-up voltage gain without extreme...

  19. Y-source impedance-network-based isolated boost DC/DC converter

    DEFF Research Database (Denmark)

    Siwakoti, Yam P.; Town, Graham; Loh, Poh Chiang

    2014-01-01

    A dc-dc converter with very high voltage gain is proposed in this paper for any medium-power application requiring a high voltage boost with galvanic isolation. The proposed converter topology can be realized using only two switches. With this topology a very high voltage boost can be achieved ev...

  20. Magnetically coupled high-gain Y-source isolated DC/DC converter

    DEFF Research Database (Denmark)

    Siwakoti, Yam P.; Loh, Poh Chiang; Blaabjerg, Frede

    2014-01-01

    A new form of magnetically coupled DC/DC converter is proposed for medium power applications (250 W to 2 kW), requiring a high-voltage gain, short inductive charging time and galvanic isolation. The proposed converter can be realised using a unique Y-source impedance network and a two-switch push...

  1. A high voltage gain quasi Z-source isolated DC/DC converter

    DEFF Research Database (Denmark)

    Siwakoti, Yam P.; Blaabjerg, Frede; Loh, Poh Chiang

    2014-01-01

    A compact quasi-Z-source DC/DC converter is presented with high voltage gain, isolated output, and improved efficiency. The improvements in size and performance were achieved by using a square wave inverter with only two output switches driving an isolating transformer in push-pull mode, followed...

  2. Planar integrated magnetics design in wide input range DC-DC converter for fuel cell application

    DEFF Research Database (Denmark)

    Ouyang, Ziwei; Zhang, Zhe; Thomsen, Ole Cornelius

    2010-01-01

    , hereby increasing the power density of converters. A new planar integrated magnetics (PIM) technique for a phase-shift plus duty cycle controlled hybrid bi-directional DC/DC converter is presented and investigated in this paper. The main magnetic components including one boost inductor and two...

  3. A Dual-Buck–Boost AC/DC Converter for DC Nanogrid With Three Terminal Outputs

    DEFF Research Database (Denmark)

    Wu, Weimin; Wang, Houqing; Liu, Yuan

    2017-01-01

    such as the low-voltage ac power system. There are three typical grounding configurations for a dc nanogrid: the united grounding, the unidirectional grounding, and the virtual isolated grounding. Each grounding configuration has its own specifications to ac/dc converters. In this paper, a dual-buck-boost ac...

  4. Quasiperiodicity and Torus Breakdown in a Power Electronic DC/DC Converter

    DEFF Research Database (Denmark)

    Zhusubaliyev, Zhanybai; Soukhoterin, Evgeniy; Mosekilde, Erik

    2007-01-01

    This paper discusses the mechanisms of torus formation and torus destruction in a dc/dc converter with relay control and hysteresis. We establish a chart of the dynamical modes in the input voltage versus load resistance parameter plane. This chart displays several different torus bifurcations...

  5. Multistability and hidden attractors in a multilevel DC/DC converter

    DEFF Research Database (Denmark)

    Zhusubaliyev, Zhanybai T.; Mosekilde, Erik

    2015-01-01

    for the hidden set in most cases has been so complicated that special analytic and/or numerical techniques have been required to locate the set. By simulating the model of a multilevel DC/DC converter that operates in the regime of high feedback gain, the paper illustrates how pulse-width modulated control can...

  6. Analysis and design of PPFHB bidirectional DC-DC converter with coupled inductors

    DEFF Research Database (Denmark)

    Zhang, Zhe; Thomsen, Ole Cornelius; Andersen, Michael Andreas E.

    2009-01-01

    In this paper, a novel push-pull-forward half-bridge (PPFHB) bi-directional DC-DC converter with coupled inductors is proposed. All switches can operate under zero-voltage-switching (ZVS). The operation principle with phase-shift modulation scheme, characteristics of coupled inductors, the steady...

  7. A VHF Class E DC-DC Converter with Self-Oscillating Gate Driver

    DEFF Research Database (Denmark)

    Andersen, Toke Meyer; Christensen, Søren K.; Knott, Arnold

    2011-01-01

    This paper describes the analysis and design of a DC-DC converter topology which is operational at frequencies in the Very High Frequency (VHF) band ranging from 30 MHz − 300 MHz. The presented topology, which consists of a class E inverter, class E rectifier, and self-oscillating gate driver, is...

  8. A New Sliding Mode Controller for DC/DC Converters in Photovoltaic Systems

    Directory of Open Access Journals (Sweden)

    M. Sarvi

    2013-01-01

    Full Text Available DC/DC converters are widely used in many industrial and electrical systems. As DC/DC converters are nonlinear and time-variant systems, the application of linear control techniques for the control of these converters is not suitable. In this paper, a new sliding mode controller is proposed as the indirect control method and compared to a simple direct control method in order to control a buck converter in photovoltaic applications. The solar arrays are dependent power sources with nonlinear voltage-current characteristics under different environmental conditions (insolation and temperature. From this point of view, the DC/DC converter is particularly suitable for the application of the sliding mode control in photovoltaic application, because of its controllable states. Simulations are performed in Matlab/Simulink software. The simulation results are presented for a step change in reference voltage and input voltage as well as step load variations. The simulations results of proposed method are compared with the conventional PID controller. The results show the good performance of the proposed sliding mode controller. The proposed method can be used for the other DC/DC converter.

  9. Interleaved Self-Oscillating Class E Derived Resonant DC/DC Converters

    DEFF Research Database (Denmark)

    Kovacevic, Milovan; Knott, Arnold; Andersen, Michael A. E.

    2012-01-01

    A new method for achieving self-oscillating, self-interleaved operation of class E derived resonant DC/DC converters is presented. The proposed method is suitable for operation at frequencies in the Very High Frequency (VHF) band. Interleaved and self-oscillating modes of operation are achieved...

  10. Integrated S-band transmitter with on-chip DC-DC converter and control loop

    NARCIS (Netherlands)

    Brouzes, H.; Geurts, S.; Besselink, M.; Telli, A.; Hek, A.P. de; Bent, G. van der; Vliet, F.E. van

    2012-01-01

    A highly integrated high-power transmitter has been designed in a high breakdown GaAs MMIC technology. The transmitter includes, on top of an S-Band 10 W class-F HPA, a DC/DC converter and its associated gate driver, the full voltage regulation control loop, which provides a significant step for pha

  11. Y-Source Boost DC/DC Converter for Distributed Generation

    DEFF Research Database (Denmark)

    Siwakoti, Yam P.; Loh, Poh Chiang; Blaabjerg, Frede

    2015-01-01

    This paper introduces a versatile Y-source boost dc/dc converter intended for distributed power generation, where high gain is often demanded. The proposed converter uses a Y-source impedance network realized with a tightly coupled three-winding inductor for high voltage boosting that is presently...

  12. Regulation of a lightweight high efficiency capacitator diode voltage multiplier dc-dc converter

    Science.gov (United States)

    Harrigill, W. T., Jr.; Myers, I. T.

    1976-01-01

    A method for the regulation of a capacitor diode voltage multiplier dc-dc converter has been developed which has only minor penalties in weight and efficiency. An auxiliary inductor is used, which only handles a fraction of the total power, to control the output voltage through a pulse width modulation method in a buck boost circuit.

  13. Regulation of a lightweight high efficiency capacitor diode voltage multiplier dc-dc converter

    Science.gov (United States)

    Harrigill, W. T., Jr.; Myers, I. T.

    1976-01-01

    A method for the regulation of a capacitor diode voltage multiplier dc-dc converter has been developed which has only minor penalties in weight and efficiency. An auxiliary inductor is used, which only handles a fraction of the total power, to control the output voltage through a pulse width modulation method in a buck boost circuit.

  14. A buck DC-DC controller based on WSAR-ADC%基于 WSAR-ADC的降压型 DC-DC 控制器设计

    Institute of Scientific and Technical Information of China (English)

    田登尧; 冯全源

    2014-01-01

    设计了一种基于加窗逐次逼近寄存器( WSAR)模拟数字转换器( ADC)的降压型DC-DC控制器,这种WSAR-ADC适用于数字电源系统,通过对输入电压进行加窗处理,能有效地降低芯片的复杂度;并利用蚁群算法,对该DC-DC控制器的比例积分微分(PID)参数进行了整定,使得整个系统能够稳定工作。电路使用BCD(Bipolar/CMOS/DMOS)0.5μm工艺,输入电压3.3 V,输出电压1 V,设计最大负载电流2 A,纹波小于9 mV,开关频率500 kHz。经过验证,该降压型DC-DC控制器能满足数字电源的采样需求。%A buck DC-DC controller based on window successive approximation register ( WSAR) and analog-to-digital converter ( ADC) was designed.It is applicable to digital power system.The circuit complexity can be re-duced by adding the window function to process input voltage;and the PID (proportion integration differentiation) parameters setting of the DC-DC controller is completed using the ant colony algorithm, which makes the whole sys-tem work stably.The circuit is implemented under Bipolar/CMOS/DMOS ( BCD) 0.5μm process, the input volt-age is 3.3 V, and the output voltage is 1 V.The designed maximum load current is 2 A, the ripple of output voltage is less than 9 mV.After verification, the switch frequency is 500 kHz.This buck DC-DC controller can meet the demand of digital power sampling.

  15. Clave interactiva para los géneros de la familia Asteraceae (Compositae presentes en la reserva municipal de Cogua (Cundinamarca, Colombia

    Directory of Open Access Journals (Sweden)

    Gómez Juan Carlos

    2005-07-01

    Full Text Available En el trabajo científico y práctico con plantas, identificar las especies es fundamental. Esta identificación se realiza con el uso de claves, las cuales proporcionan la identidad correcta de una especie a través de un proceso de eliminación por contraste. En este trabajo se planteó elaborar una clave interactiva para los géneros de la familia Asteraceae (Compositae reportados en la Reserva Municipal de Cogua (Cundinamarca, Colombia, como herramienta para el reconocimiento de la flora local. Se obtuvo una clave interactiva en formato DELTA para los 31 géneros de la familia Asteraceae registrados en la reserva, con un listado de 173 caracteres diagnósticos para la familia, que engloban la variabilidad de las 57 especies estudiadas. Además, fue ilustrada con fotografías y dibujos de las especies y de los caracteres para facilitar el proceso de identificación, y se preparó para ser publicada en Internet de manera que pueda ser utilizada desde la red o quemada en un CD sin necesidad de conexión. La clave demostró ser eficiente para identificar los géneros de
    Asteraceae presentes en la reserva, utilizando solamente los caracteres de tipo vegetativo, con escaso uso de los caracteres de inflorescencia, y nulo requerimiento de caracteres florales. Esto es un resultado asombroso y no esperado para la familia Asteraceae, cuyas claves tradicionales requieren, desde el comienzo caracteres reproductivos. Es posible apreciar así la alta efectividad de la clave y la gran utilidad del programa DELTA.

  16. Revisión taxonómica del complejo Centaurea alba L. (Asteraceae) en la Península Ibérica

    OpenAIRE

    López, Eusebio; Devesa Alcaraz, Juan Antonio

    2011-01-01

    Taxonomic revision of the Centaurea alba L. complex (Asteraceae) in the Iberian Peninsula.- A taxonomic revision of the Centaurea alba L. complex (Centaurea L. sect. Centaurea) in the Iberian Peninsula is presented, which is represented by two species, C. alba and C. costae Willk. Three subspecies of C. alba with reasonably well-defined areas are recognized: C. alba subsp. alba, with three varieties –alba, macrocephala Pau and latronum (Pau) E. López & Devesa-, C. alba subsp. aris...

  17. Revisión taxonómica del complejo Centaurea alba L. (Asteraceae) en la Península Ibérica

    OpenAIRE

    Devesa, J. A.; López, E.

    2011-01-01

    Taxonomic revision of the Centaurea alba L. complex (Asteraceae) in the Iberian Peninsula.- A taxonomic revision of the Centaurea alba L. complex (Centaurea L. sect. Centaurea) in the Iberian Peninsula is presented, which is represented by two species, C. alba and C. costae Willk. Three subspecies of C. alba with reasonably well-defined areas are recognized: C. alba subsp. alba, with three varieties –alba, macrocephala Pau and latronum (Pau) E. López & Devesa-, C. alba subsp. aristifera (Pau...

  18. Use of Bidens pilosa L. (Asteraceae) and Curcuma longa L. (Zingiberaceae) to treat intestinal mucositis in mice: Toxico-pharmacological evaluations

    OpenAIRE

    Carla Caroline Cunha Bastos; Paulo Henrique Marcelino de Ávila; Edvande Xavier dos Santos Filho; Renato Ivan de Ávila; Aline Carvalho Batista; Simone Gonçalves Fonseca; Eliana Martins Lima; Ricardo Neves Marreto; Elismauro Francisco de Mendonça; Marize Campos Valadares

    2016-01-01

    Introduction: Several studies towards the development of an effective treatment for intestinal mucositis have been reported, since this condition represents a major problem in clinical oncology practice due to cytotoxic effects of chemotherapy. However standardized protocols and universally accepted treatment options are yet to be established. Objectives: Given above, this study evaluated the protective effects of a mucoadhesive formulation containing both Bidens pilosa L. (Asteraceae) (BP...

  19. A suitable model plant for control of the set fuel cell-DC/DC converter

    Energy Technology Data Exchange (ETDEWEB)

    Andujar, J.M.; Segura, F.; Vasallo, M.J. [Departamento de Ingenieria Electronica, Sistemas Informaticos y Automatica, E.P.S. La Rabida, Universidad de Huelva, Ctra. Huelva - Palos de la Frontera, S/N, 21819 La Rabida - Palos de la Frontera Huelva (Spain)

    2008-04-15

    In this work a state and transfer function model of the set made up of a proton exchange membrane (PEM) fuel cell and a DC/DC converter is developed. The set is modelled as a plant controlled by the converter duty cycle. In addition to allow setting the plant operating point at any point of its characteristic curve (two interesting points are maximum efficiency and maximum power points), this approach also allows the connection of the fuel cell to other energy generation and storage devices, given that, as they all usually share a single DC bus, a thorough control of the interconnected devices is required. First, the state and transfer function models of the fuel cell and the converter are obtained. Then, both models are related in order to achieve the fuel cell+DC/DC converter set (plant) model. The results of the theoretical developments are validated by simulation on a real fuel cell model. (author)

  20. Optimization of Shielded PCB Air-Core Toroids for High-Efficiency DC-DC Converters

    CERN Document Server

    Orlandi, S; Buso, S; Michelis, S; Fuentes, C A; Kayal, M; Faccio, F; Spiazzi, G

    2011-01-01

    The paper describes the design of optimized printed circuit board (PCB) air-core toroids for high-frequency dc-dc converters with strict requirements in terms of volume and noise. The effect of several design parameters on the overall inductor volume, on dc and ac winding resistance, and on the radiated noise will be investigated. PCB toroids are compared to standard air-core solenoids and other state-of-the-art air-core toroids both theoretically and experimentally: at first, using ANSOFT Maxwell and ANSOFT Q3D simulation tools, and subsequently, with laboratory measurements (irradiated noise, efficiency, and frequency response) on several prototypes. These very flexible and rather easy to manufacture inductors appear very attractive for compact high-frequency dc-dc converters where high efficiency, low volume, and low noise are of primary concern.