WorldWideScience

Sample records for del gradiente altitudinal

  1. ESTRUCTURA DE UNA COMUNIDAD DE LÍQUENES Y MORFOLOGIA DEL GÉNERO STICTA (STICTACEAE EN UN GRADIENTE ALTITUDINAL

    Directory of Open Access Journals (Sweden)

    Benicia Watteijne Ceron

    2009-09-01

    Full Text Available La distribución y el crecimiento de los líquenes están condicionados por diferentes factores ambientales, entre estos la variación en gradientes altitudinales. En la cordillera Oriental de los Andes de Colombia, no se han realizado estudios sobre zonación altitudinal de líquenes. En este trabajo se estudiaron las variaciones en la estructura de la comunidad de líquenes epifitos en un gradiente altitudinal (2000-2600 m en el PNN Tatamá. Se encontró que con el aumento en altura hay una disminución en riqueza y diversidad, siendo esto una desviación del patrón encontrado generalmente en otros trabajos sobre líquenes y gradientes altitudinales. La comunidad a bajas alturas se compone principalmente de líquenes fruticosos (cobertura de 30% a 2070 m y 0% a 2560 m y a mayores alturas de líquenes foliosos (cobertura de 15% a 2070 m y 43% a 2560 m. La altura, además de influenciar la estructura de la comunidad de los líquenes, puede afectar el desarrollo y la morfología de estos. En el género folioso Sticta se presentaron variaciones intraespecificas en la densidad de cifelas (órganos de intercambio gaseoso asociadas a la altura, encontrándose un efecto significativo de la altura sobre la densidad de cifelas en las especies S. andensis  y S. gyalocarpa (ANOVA, valor p= 0.008 y 0.05 respectivamente. Esto muestra un mecanismo de adaptación a los cambios ambientales que se dan con la altura.

  2. ANUROS DEL GRADIENTE ALTITUDINAL DE LA ESTACIÓN EXPERIMETAL Y DEMOSTRATIVA EL RASGÓN (SANTANDER, COLOMBIA

    Directory of Open Access Journals (Sweden)

    SUÁREZ-BADILLO HENRY A.

    2004-12-01

    Full Text Available Se caracterizó la fauna de anuros sobre un gradiente altitudinal de 2200 a 3200 mabarcando tres formaciones vegetales, Selva Andina, Bosque Altoandino ySubpáramo, sobre la cordillera Oriental colombiana. Se realizaron 43 sesiones detrabajo entre Agosto de 2000 y Febrero de 2002 aplicando búsqueda libre porinspección visual y transectos. Se registraron doce de las especies conocidas de lazona y una más indescrita que constituye un nuevo registro y se suma a las dosespecies indescritas previamente registradas. Las abundancias absolutas fuerondiferentes entre las 3 formaciones vegetales y entre las épocas de muestreo.Contrariamente, no hubo diferencias entre el número de individuos obtenidos enlos meses secos contrastados con los meses lluviosos. La mayoría de especies eindividuos utilizaron el estrato herbáceo y parece no haber un uso diferencial delestrato vertical. E. prolixodiscus mostró preferencia por las bromelias como sustrato.Las curvas de acumulación de especies mostraron que el inventario está casicompleto en la Selva Andina y está en sus inicios en el Bosque Altoandino y elSubpáramo. Se observó una diversidad â baja entre los sitios evaluados.Eleutherodactylus anolirex, E. prolixodiscus y Eleutherodactylus sp. 1 sedistribuyen de forma continua en el gradiente, mientras que E. douglasi, E. lutitus,E. merostictus y Eleutherodactylus sp. 3 llegan hasta su parte media. E. douglasiy E. prolixodiscus aumentaron sus cotas altitudinales superiores (en 350 y 710 mrespectivamente. La disminución de la riqueza a lo largo del gradiente (quince,siete y tres especies es reflejo de una tendencia conocida, acentuada por elsubmuestreo de las partes media y alta de El Rasgón.

  3. Perfil altitudinal de la temperatura media del aire en Colombia

    Directory of Open Access Journals (Sweden)

    Eslava Jesus

    1992-10-01

    Full Text Available

    Se establecen ecuaciones que relacionan la temperatura media anual del aire en

    Colombia con la altitud. Por medio de ellas se posibilita estimar los valores de esa temperatura en cualquier lugar, con el requisito de conocer únicamente el dato de su altitud y ubicación regional; también se determinan los gradientes altitudinales que, a su vez, posibilitan conocer cualquier otro dato de temperatura del aire,  conociendo los datos de otro sitio o estación base. Las ecuaciones muestran que los valores a nivel del mar y la variación altitudinal de la temperatura del aire en Colombia no son únicos, sino que cambian según las condiciones físicas de cada región o subregión y se diferencias sustancialmente de los valores propuestos con anterioridad por otros autores.

    Equations that establish relations between annual average temperature and altitude are defined for Colombia. These equations allow to estimate temperature values at any place, just by knowing altitude and regional location data. It is also possible to determine altitudinal gradients, which in turn allows to know the temperature of a given place, from the data for a base. The defined equations show that temperature is not a unique function of altitudinal changes, but it also depends on specific physical conditions for each region or subregion.

  4. Altitudinal gradient effect on morphometric variation and leaf symmetry of Platanus mexicana Moric

    OpenAIRE

    Dulce Ma. Galván-Hernández; J. Armando Lozada-García; Norma Flores-Estévez; Jorge Galindo-González; S. Mario Vázquez-Torres

    2015-01-01

    La variación morfométrica y simetría foliar de una población de Platanus mexicana se caracterizaron en un gradiente altitudinal ripario del estado de Veracruz. Ocho caracteres morfométricos se evaluaron en 1,800 hojas provenientes de 15 individuos por sitio (70, 200, 600 y 1,700 m de altitud). Las diferencias morfométricas entre sitios (F(24, 5189) = 21.1, P < 0.05) se determinaron con un análisis de funciones discriminantes. Los caracteres relacionados con el largo y ancho de las hojas deter...

  5. Strong altitudinal partitioning in the distributions of ectomycorrhizal fungi along a short (300 m) elevation gradient

    OpenAIRE

    Jarvis, Susan G.; Woodward, Steve; Taylor, Andy F.S.

    2015-01-01

    • Changes in species richness and distributions of ectomycorrhizal (ECM) fungal communities along altitudinal gradients have been attributed to changes in both host distributions and abiotic variables. However, few studies have considered altitudinal relationships of ECM fungi associated with a single host to identify the role of abiotic drivers. To address this, ECM fungal communities associated with one host were assessed along five altitudinal transects in Scotland. • Roots of Scots pin...

  6. Aquatic macroinvertebrate diversity and composition in streams along an altitudinal gradient in Southeastern Brazil

    OpenAIRE

    Henriques-Oliveira, Ana Lucia; Nessimian, Jorge Luiz

    2010-01-01

    Aquatic macroinvertebrate diversity and composition in streams along an altitudinal gradient in Southeastern Brazil. A study concerning taxonomic richness and composition of the aquatic insect fauna in streams within the same catchment basin along an altitudinal gradient in Southeast Brazil, was conducted to test the hypothesis that there is a faunal discontinuity in the biocenotic composition, related to differences in altitude and latitude. In Southeastern Brazil, around latitude 22°, this ...

  7. Distribution of grasses along an altitudinal gradient in a Venezuelan paramo Distribución de gramíneas a lo largo de un gradiente altitudinal en un páramo de Venezuela

    Directory of Open Access Journals (Sweden)

    EDJULY J. MÁRQUEZ

    2004-12-01

    Full Text Available In Venezuelan paramos grasses, after Asteraceae, are the second family in numerical importance. We studied their distribution in an altitudinal gradient located in Venezuela, Sierra de La Culata, between 2,500 and 4,200 m of altitude. Twenty one 32 m parallel line transects every 50 m were placed along the gradient, perpendicular to the main slope. Each line was divided into contiguous 50 x 50 cm sampling units. Grass species occurrence inside each sample unit was considered to determine their frequency in each line or altitude. The peak and altitudinal amplitude was determined through the weighted averaging method. A total of 47 grass species were found along the gradient. Agrostis was the best-represented genus in the gradient. Considering the distribution ranges, we assume that there are different biotic and abiotic processes determining the distribution patterns. The species occurring at the highest altitudes were temperate elements, while those in the lowest areas were tropical and subtropical elements. Seven species in the gradient are endemic to the Venezuelan paramos. Grass distribution patterns in the paramo may be related to phytogeographical origin. In order to better understand the plant altitudinal distribution pattern is necessary to consider the plant responses to low temperatures, high incoming radiation, water stress and slope aspectEn los páramos de Venezuela las gramíneas son la segunda familia numéricamente más importante, después de las Asteraceae. Nosotros estudiamos su distribución en un gradiente altitudinal ubicado en Venezuela, Sierra de La Culata, entre 2.500 y 4.200 m de altitud. Para esto colocamos 21 transectas de 32 m de longitud a lo largo del gradiente, ubicados de manera perpendicular a la pendiente, cada 50 m en altitud. Cada transecta estaba dividida en unidades de muestreo contiguas de 50 x 50 cm. Para estimar la frecuencia de las especies en cada transecta o altitud, consideramos la ocurrencia de las

  8. Species richness and trait composition of butterfly assemblages change along an altitudinal gradient.

    Science.gov (United States)

    Leingärtner, Annette; Krauss, Jochen; Steffan-Dewenter, Ingolf

    2014-06-01

    Species richness patterns along altitudinal gradients are well-documented ecological phenomena, yet very little data are available on how environmental filtering processes influence the composition and traits of butterfly assemblages at high altitudes. We have studied the diversity patterns of butterfly species at 34 sites along an altitudinal gradient ranging from 600 to 2,000 m a.s.l. in the National Park Berchtesgaden (Germany) and analysed traits of butterfly assemblages associated with dispersal capacity, reproductive strategies and developmental time from lowlands to highlands, including phylogenetic analyses. We found a linear decline in butterfly species richness along the altitudinal gradient, but the phylogenetic relatedness of the butterfly assemblages did not increase with altitude. Compared to butterfly assemblages at lower altitudes, those at higher altitudes were composed of species with larger wings (on average 9%) which laid an average of 68% more eggs. In contrast, egg maturation time in butterfly assemblages decreased by about 22% along the altitudinal gradient. Further, butterfly assemblages at higher altitudes were increasingly dominated by less widespread species. Based on our abundance data, but not on data in the literature, population density increased with altitude, suggesting a reversed density-distribution relationship, with higher population densities of habitat specialists in harsh environments. In conclusion, our data provide evidence for significant shifts in the composition of butterfly assemblages and for the dominance of different traits along the altitudinal gradient. In our study, these changes were mainly driven by environmental factors, whereas phylogenetic filtering played a minor role along the studied altitudinal range.

  9. Compositional changes in bee and wasp communities along Neotropical mountain altitudinal gradient.

    Directory of Open Access Journals (Sweden)

    Lucas Neves Perillo

    Full Text Available Climate conditions tend to differ along an altitudinal gradient, resulting in some species groups' patterns of lower species richness with increasing altitude. While this pattern is well understood for tropical mountains, studies investigating possible determinants of variation in beta-diversity at its different altitudes are scarce. We sampled bee and wasp communities (Hymenoptera: Aculeata along an altitudinal gradient (1,000-2,000 m.a.s.l. in a tropical mountainous region of Brazil. Trap nests and Moericke traps were established at six sampling points, with 200 m difference in altitude between each point. We obtained average climate data (1970-2000 from Worldclim v2 for altitudes at each sampling site. Nest traps captured 17 bee and wasp species from six families, and Moericke traps captured 124 morphospecies from 13 families. We found a negative correlation between altitude and species richness and abundance. Temperature, precipitation, water vapor pressure, and wind speed influenced species richness and abundance, and were correlated with altitude. β-diversity was primarily determined by species turnover as opposed to nestedness, and Aculeate community similarity was higher for more similar altitudinal ranges. Moericke traps seem to be more efficient for altitudinal surveys compared to nest traps. We found high occurrence of singleton and doubleton species at all altitudes, highlighting the need for long-term studies to efficiently assess hymenopteran diversity in these environments.

  10. Anthocyanin Profile in Berries of Wild and Cultivated Vaccinium spp. along Altitudinal Gradients in the Alps.

    Science.gov (United States)

    Zoratti, Laura; Jaakola, Laura; Häggman, Hely; Giongo, Lara

    2015-10-07

    Vaccinium spp. berries provide some of the best natural sources of anthocyanins. In the wild bilberry (Vaccinium myrtillus L.), a clear increasing trend in anthocyanin biosynthesis has been reported toward northern latitudes of Europe, but studies related to altitude have given contradictory results. The present study focused on the anthocyanin composition in wild bilberries and highbush blueberry (Vaccinium corymbosum L. cv. Brigitta Blue) growing along altitudinal gradients in the Alps of northern Italy. Our results indicate an increasing accumulation of anthocyanins in bilberries along an altitudinal gradient of about 650 m. The accumulation was due to a significant increase in delphinidin and malvidin glycosides, whereas the accumulation of cyanidin and peonidin glycosides was not affected by altitude. Seasonal differences, especially temperature, had a major influence on the accumulation of anthocyanins in blueberries.

  11. Selection by pollinators on floral traits in generalized Trollius ranunculoides (Ranunculaceae along altitudinal gradients.

    Directory of Open Access Journals (Sweden)

    Zhi-Gang Zhao

    Full Text Available Abundance and visitation of pollinator assemblages tend to decrease with altitude, leading to an increase in pollen limitation. Thus increased competition for pollinators may generate stronger selection on attractive traits of flowers at high elevations and cause floral adaptive evolution. Few studies have related geographically variable selection from pollinators and intraspecific floral differentiation. We investigated the variation of Trollius ranunculoides flowers and its pollinators along an altitudinal gradient on the eastern Qinghai-Tibet Plateau, and measured phenotypic selection by pollinators on floral traits across populations. The results showed significant decline of visitation rate of bees along altitudinal gradients, while flies was unchanged. When fitness is estimated by the visitation rate rather than the seed number per plant, phenotypic selection on the sepal length and width shows a significant correlation between the selection strength and the altitude, with stronger selection at higher altitudes. However, significant decreases in the sepal length and width of T. ranunculoides along the altitudinal gradient did not correspond to stronger selection of pollinators. In contrast to the pollinator visitation, mean annual precipitation negatively affected the sepal length and width, and contributed more to geographical variation in measured floral traits than the visitation rate of pollinators. Therefore, the sepal size may have been influenced by conflicting selection pressures from biotic and abiotic selective agents. This study supports the hypothesis that lower pollinator availability at high altitude can intensify selection on flower attractive traits, but abiotic selection is preventing a response to selection from pollinators.

  12. Characteristics of soils in selected maize growing sites along altitudinal gradients in East African highlands

    Directory of Open Access Journals (Sweden)

    Elijah Njuguna

    2015-12-01

    Full Text Available Maize is the main staple crop in the East African Mountains. Understanding how the edaphic characteristics change along altitudinal gradients is important for maximizing maize production in East African Highlands, which are the key maize production areas in the region. This study evaluated and compared the levels of some macro and micro-elements (Al, Ca, Fe, K, Mg, Mn, Na and P and other soil parameters (pH, organic carbon content, soil texture [i.e. % Sand, % Clay and % Silt], cation exchange capacity [CEC], electric conductivity [EC], and water holding capacity [HC]. Soil samples were taken from maize plots along three altitudinal gradients in East African highlands (namely Machakos Hills, Taita Hills and Mount Kilimanjaro characterized by graded changes in climatic conditions. For all transects, pH, Ca, K and Mg decreased with the increase in altitude. In contrast, % Silt, organic carbon content, Al and water holding capacity (HC increased with increasing altitude. The research provides information on the status of the physical–chemical characteristics of soils along three altitudinal ranges of East African Highlands and includes data available for further research.

  13. Variation and Genetic Structure in Platanus mexicana (Platanaceae along Riparian Altitudinal Gradient

    Directory of Open Access Journals (Sweden)

    Dulce M. Galván-Hernández

    2015-01-01

    Full Text Available Platanus mexicana is a dominant arboreal species of riparian ecosystems. These ecosystems are associated with altitudinal gradients that can generate genetic differences in the species, especially in the extremes of the distribution. However, studies on the altitudinal effect on genetic variation to riparian species are scarce. In Mexico, the population of P. mexicana along the Colipa River (Veracruz State grows below its reported minimum altitude range, possibly the lowest where this tree grows. This suggests that altitude might be an important factor in population genetics differentiation. We examined the genetic variation and population structuring at four sites with different altitudes (70, 200, 600 and 1700 m a.s.l. using ten inter-simple sequence repeats (ISSR markers. The highest value for Shannon index and Nei’s gene diversity was obtained at 1700 m a.s.l. (He = 0.27, Ne = 1.47, I = 0.42 and polymorphism reached the top value at the middle altitude (% p = 88.57. Analysis of molecular variance (AMOVA and STRUCTURE analysis indicated intrapopulation genetic differentiation. The arithmetic average (UPGMA dendrogram identified 70 m a.s.l. as the most genetically distant site. The genetic structuring resulted from limited gene flow and genetic drift. This is the first report of genetic variation in populations of P. mexicana in Mexico. This research highlights its importance as a dominant species, and its ecological and evolutionary implications in altitudinal gradients of riparian ecosystems.

  14. How do two Lupinus species respond to temperature along an altitudinal gradient in the Venezuelan Andes? ¿Cómo responden dos especies de Lupinus a la temperatura en un gradiente altitudinal en los Andes venezolanos?

    Directory of Open Access Journals (Sweden)

    FERMÍN RADA

    2008-09-01

    Full Text Available Temperature determines plant formations and species distribution along altitudinal gradients. Plants in the tropical high Andes, through different physiological and morphological characteristics, respond to freezing night temperatures and high daytime energy inputs which occur anytime of the year. The main objective of this study was to characterize day and night temperature related responses of two Lupinus species with different altitudinal ranges (L. meridanus, 1,800-3,600 and L. eromonomos, 3,700-4,300 m of altitude. Are there differences in night low temperature resistance mechanisms between the species along the gradient? How do these species respond, in terms of optimum temperature for photosynthesis, to increasing altitude? Lupinus meridanus shows frost avoidance, in contrast to L. eromonomos, which tolerates freezing at higher altitudes. Optimum temperature for photosynthesis decreases along the gradient for both species. Maximum C0(2 assimilation rates were higher in L. meridanus, while L. eromonomos showed decreasing C0(2 assimilation rates at the higher altitude. In most cases, measured daily leaf temperature is always within the 80 % of optimum for photosynthesis. L. meridanus7 upper distribution limit seems to be restricted by cold resistance mechanisms, while L. eromonomos7 to a combination of both cold resistance and to C0(2 assimilation responses at higher altitudes.La temperatura determina las formaciones vegetales y la distribución de especies a lo largo de gradientes altitudinales. Las plantas en los altos Andes tropicales, a través de diferentes características morfológicas y fisiológicas, responden a temperaturas congelantes nocturnas y altas entradas energéticas durante el día en cualquier momento del año. El objetivo principal de este estudio fue caracterizar las respuestas relacionadas con temperaturas diurnas y nocturnas en dos especies de Lupinus con diferente distribución altitudinal (L. meridanus, 1

  15. Carbon and nitrogen dynamics of soil and litter along an altitudinal gradient in Atlantic Forest

    Science.gov (United States)

    Piccolo, M. D.; Martins, S. C.; Camargo, P. B.; Carmo, J. B.; Sousa Neto, E.; Martinelli, L. A.

    2008-12-01

    The Ombrophylus Dense Forest or Atlantic Forest is the second most important Biome in extension of Brazil, and it is considered a hot-spot in terms of biodiversity. It is localized in Brazilian Coast, and it covered originally 1.2 million km2, but currently only 8% of the original forest remains. The study was carried out in Sao Paulo State, Brazil (23° 24' S and 45° 11' W). The studied areas were: Restinga Vegetation (RV), 5 m above sea level; Low Altitude Ombrophylus Dense Forest (LAODF), 100 m asl; Submontane Ombrophylus Dense Forest (SODF), 600m asl and; Montane Ombrophylus Dense Forest (MODF), 1000 m asl. The aim of this study was to evaluate the effect of altitudinal gradient, with specific phytophysiognomies, on C and N dynamics in the soil and litter at Atlantic Forest. A sampling area of 1 ha was subdivided in contiguous sub- parcels (10 x 10 m). The forest floor litter accumulated (0.06 m2) was collected monthly (n=60), during 12 months, in each phytophysiognomies. Soils samples (0-0.05m depth) were collected (n=32) from square regular grids, 30 m away from each other. Changes in litter contents of C and N were not detected along the altitudinal gradient, and the values observed were 400 and 15g kg-1 for C and N, respectively. Litter ä13C values did not change significantly with the altitudinal gradient and were represented by C3 plants values. The C and N stocks were high in the clay soils (LAODF, SODF and MODF) when compared to sandy soil (RV). The soil C stocks (24 to 30 Mg ha-1) were similar among the altitudinal gradients, except RV (16 Mg ha-1). The areas of elevated altitude (MODF and SODF) showed high N stocks (2.3 Mg ha-1), followed by LAODF (1.8Mg ha-1) and RV (0.9Mg ha-1). In all altitudes there was 13C enrichment with soil depth, and it can be explained by the different fractions of the organic matter distributed along the soil profile, and also due the effect of the isotopic dilution between the forest floor litter and the soil.

  16. Medicinal Plants Density Along an Altitudinal Gradient in and Around Ayubia National Park

    International Nuclear Information System (INIS)

    Tariq, A.; Adnan, M.; Begum, S.

    2016-01-01

    Medicinal plants are an essential source of livelihood for many rural populations and are currently facing several threats of extinction in temperate Himalaya, such as excessive grazing and collection along altitudinal gradients. The present study was designed to investigate the species density of medicinal plants at different mid-altitude levels (2200, 2300, 2400, and 2500 m above the sea level (a.s.l.) between two forest-use types and to examine the possible association between medicinal plant densities and forest-stand structural variables along the altitudinal gradient. Factorial design analysis of variance showed that the densities of all medicinal plants differed significantly between the forest-use types (p<0.00) and elevation (p<0.00). Moreover, a significant interaction (p<0.04) was also observed between the forest-use types and elevation. In the old-growth forest, density of medicinal plants was 290/40 m/sup 2/ at the higher altitude (2500 m a.s.l.), approximately 1.5-fold less than the 475/40 m/sup 2/ density observed at lower altitude (2200 m a.s.l.). However, in derived woodland, density of medicinal plants at higher altitude was approximately 4-fold less than that at the lower altitude. At these altitudinal levels, medicinal plants densities, such as Valeriana jatamansi, were significantly higher under old-growth forest compared to derived woodland, where they were almost nonexistent. A rapid vulnerability assessment has also shown that Valeriana jatamansi and Viola canescens were highly vulnerable species. Litter cover was the influential variable that was most likely related to medicinal plant density. In conclusion, abundance of medicinal plants decreased along mid-altitude levels in both of the forest-use types. However, this decrease was extremely marked in the derived woodland, and this decline may be due to human activity. Hence, these factors must be considered in future studies to suggest protective measures that can be applied along

  17. Morphological and colour morph clines along an altitudinal gradient in the meadow grasshopper Pseudochorthippus parallelus.

    Science.gov (United States)

    Köhler, Günter; Samietz, Jörg; Schielzeth, Holger

    2017-01-01

    Many animals show altitudinal clines in size, shape and body colour. Increases in body size and reduction in the length of body appendices in colder habitats are usually attributed to improved heat conservation at lower surface-to-volume ratios (known as Bergmann's and Allen's rule, respectively). However, the patterns are more variable and sometimes reversed in small ectotherms that are affected by shortened growing seasons. Altitude can also affect colouration. The thermal melanism hypothesis predicts darker colours under cooler conditions because of a thermoregulatory advantage. Darker colours may also be favoured at high altitudes for reasons of UV protection or habitat-dependent crypsis. We studied altitudinal variation in morphology and colour in the colour-polymorphic meadow grasshopper Pseudochorthippus parallelus based on 563 individuals from 17 populations sampled between 450 and 2,500 m asl. Pronotum length did not change with altitude, while postfemur length decreased significantly in both sexes. Tegmen (forewing) length decreased in males, but not in females. The results indicate that while body size, as best quantified by pronotum length, was remarkably constant, extended appendices were reduced at high altitudes. The pattern thus follows Allen's rule, but neither Bergmann's nor converse Bergmann's rule. These results indicate that inference of converse Bergmann's rule based on measurements from appendices should be treated with some caution. Colour morph ratios showed significant changes in both sexes from lowland populations dominated by green individuals to high-altitude populations dominated by brown ones. The increase of brown morphs was particularly steep between 1,500 and 2,000 m asl. The results suggest shared control of colour in males and females and local adaptation along the altitudinal gradient following the predictions of the thermal melanism hypothesis. Interestingly, both patterns, the reduction of body appendices and the higher

  18. Morphological and colour morph clines along an altitudinal gradient in the meadow grasshopper Pseudochorthippus parallelus.

    Directory of Open Access Journals (Sweden)

    Günter Köhler

    Full Text Available Many animals show altitudinal clines in size, shape and body colour. Increases in body size and reduction in the length of body appendices in colder habitats are usually attributed to improved heat conservation at lower surface-to-volume ratios (known as Bergmann's and Allen's rule, respectively. However, the patterns are more variable and sometimes reversed in small ectotherms that are affected by shortened growing seasons. Altitude can also affect colouration. The thermal melanism hypothesis predicts darker colours under cooler conditions because of a thermoregulatory advantage. Darker colours may also be favoured at high altitudes for reasons of UV protection or habitat-dependent crypsis. We studied altitudinal variation in morphology and colour in the colour-polymorphic meadow grasshopper Pseudochorthippus parallelus based on 563 individuals from 17 populations sampled between 450 and 2,500 m asl. Pronotum length did not change with altitude, while postfemur length decreased significantly in both sexes. Tegmen (forewing length decreased in males, but not in females. The results indicate that while body size, as best quantified by pronotum length, was remarkably constant, extended appendices were reduced at high altitudes. The pattern thus follows Allen's rule, but neither Bergmann's nor converse Bergmann's rule. These results indicate that inference of converse Bergmann's rule based on measurements from appendices should be treated with some caution. Colour morph ratios showed significant changes in both sexes from lowland populations dominated by green individuals to high-altitude populations dominated by brown ones. The increase of brown morphs was particularly steep between 1,500 and 2,000 m asl. The results suggest shared control of colour in males and females and local adaptation along the altitudinal gradient following the predictions of the thermal melanism hypothesis. Interestingly, both patterns, the reduction of body appendices and

  19. Floristic diversity and distribution pattern of plant communities along altitudinal gradient in Sangla Valley, Northwest Himalaya.

    Science.gov (United States)

    Sharma, Pankaj; Rana, J C; Devi, Usha; Randhawa, S S; Kumar, Rajesh

    2014-01-01

    Himalayas are globally important biodiversity hotspots and are facing rapid loss in floristic diversity and changing pattern of vegetation due to various biotic and abiotic factors. This has necessitated the qualitative and quantitative assessment of vegetation here. The present study was conducted in Sangla Valley of northwest Himalaya aiming to assess the structure of vegetation and its trend in the valley along the altitudinal gradient. In the forest and alpine zones of the valley, 15 communities were recorded. Study revealed 320 species belonging to 199 genera and 75 families. Asteraceae, Rosaceae, Apiaceae, and Ranunculaceae were dominant. Among genera, Artemisia followed by Polygonum, Saussurea, Berberis, and Thalictrum were dominant. Tree and shrub's density ranged from 205 to 600 and from 105 to 1030 individual per hectare, respectively, whereas herbs ranged from 22.08 to 78.95 individual/m(2). Nearly 182 species were native to the Himalaya. Maximum altitudinal distribution of few selected climate sensitive species was found to be highest in northeast and north aspects. This study gives an insight into the floristic diversity and community structure of the fragile Sangla Valley which was hitherto not available.

  20. Species richness of vascular plants, bryophytes, and lichens along an altitudinal gradient in western Norway

    Science.gov (United States)

    Grytnes, John Arvid; Heegaard, Einar; Ihlen, Per G.

    2006-05-01

    Species richness patterns of ground-dwelling vascular plants, bryophytes, and lichens were compared along an altitudinal gradient (310-1135 m a.s.l.), in western Norway. Total species richness peaked at intermediate altitudes, vascular plant species richness peaked immediately above the forest limit (at 600-700 m a.s.l.), bryophyte species richness had no statistically significant trend, whereas lichen richness increased from the lowest point and up to the forest limit, with no trend above. It is proposed that the pattern in vascular plant species richness is enhanced by an ecotone effect. Bryophyte species richness responds to local scale factors whereas the lichen species richness may be responding to the shading from the forest trees.

  1. Distribución y diversidad de colémbolos (Hexapoda: Collembola en el gradiente altitudinal de un bosque templado en México

    Directory of Open Access Journals (Sweden)

    Arturo García-Gómez

    2011-03-01

    Full Text Available Los colémbolos son fragmentadores importantes de la hojarasca, presentan diferentes patrones de distribución a lo largo de un gradiente altitudinal. El objetivo del presente trabajo es determinar la diversidad y distribución de Collembola en el volcán Iztaccíhuatl. Para ello, se realizaron cuatro muestreos, a lo largo de un año en cuatro pisos altitudinales (I=2 753, II=3 015, III=3 250 y IV=3 687m.s.n.m. y se calcularon los índices de diversidad de Shannon, equitatividad de Pielou y dominancia de Simpson, para compararlos mediante una prueba de t modificada. Los resultados muestran al piso III como el más diverso, y la mayor equitatividad se encuentra en el II. Además, se hallaron diferencias significativas entre los pisos II-III (t0.01, 187=4.11, pDistribution and diversity of springtails (Hexapoda: Collembola on the altitudinal gradient of a temperate forest in Mexico. Mountain ecosystems have shown slow mineralization activity due to weather conditions, and to some groups with arthropods with special roles. The Collembola is an important group for litter fragmentation, showing different distribution patterns. The objective of the present study was to determine the diversity of Collembola along a volcano altitudinal gradient. For this, four sampling expeditions evaluated four altitudinal levels (I=2 753, II=3 015, III=3 250 and IV=3 687 masl in Iztaccihuatl Volcano, from November 2003, and March, June and August 2004. Shannon diversity (H’, Pielou evenness (J’ and Simpson dominance (1/λ indices were calculated. The similarity between the associations of springtails between the sampling sites was evaluated by a cluster analysis using the Pearson correlation coefficient, as distance and the unpaired arithmetic averages (UPGMA as amalgamation method. A total of 24 075 springtails, distributed in 12 families, 46 genera and 86 species was collected. The higher species abundance was found at the altitudinal area II. The lowest

  2. Temperature sensitivity and enzymatic mechanisms of soil organic matter decomposition along an altitudinal gradient on Mount Kilimanjaro

    Science.gov (United States)

    Blagodatskaya, Еvgenia; Blagodatsky, Sergey; Khomyakov, Nikita; Myachina, Olga; Kuzyakov, Yakov

    2016-02-01

    Short-term acceleration of soil organic matter decomposition by increasing temperature conflicts with the thermal adaptation observed in long-term studies. Here we used the altitudinal gradient on Mt. Kilimanjaro to demonstrate the mechanisms of thermal adaptation of extra- and intracellular enzymes that hydrolyze cellulose, chitin and phytate and oxidize monomers (14C-glucose) in warm- and cold-climate soils. We revealed that no response of decomposition rate to temperature occurs because of a cancelling effect consisting in an increase in half-saturation constants (Km), which counteracts the increase in maximal reaction rates (Vmax with temperature). We used the parameters of enzyme kinetics to predict thresholds of substrate concentration (Scrit) below which decomposition rates will be insensitive to global warming. Increasing values of Scrit, and hence stronger canceling effects with increasing altitude on Mt. Kilimanjaro, explained the thermal adaptation of polymer decomposition. The reduction of the temperature sensitivity of Vmax along the altitudinal gradient contributed to thermal adaptation of both polymer and monomer degradation. Extrapolating the altitudinal gradient to the large-scale latitudinal gradient, these results show that the soils of cold climates with stronger and more frequent temperature variation are less sensitive to global warming than soils adapted to high temperatures.

  3. Exploring climatic controls on blanket bog litter decomposition across an altitudinal gradient

    Science.gov (United States)

    Bell, Michael; Ritson, Jonathan P.; Clark, Joanna M.; Verhoef, Anne; Brazier, Richard E.

    2016-04-01

    The hydrological and ecological functioning of blanket bogs is strongly coupled, involving multiple ecohydrological feedbacks which can affect carbon cycling. Cool and wet conditions inhibit decomposition, and favour the growth of Sphagnum mosses which produce highly recalcitrant litter. A small but persistent imbalance between production and decomposition has led to blanket bogs in the UK accumulating large amounts of carbon. Additionally, healthy bogs provide a suite of other ecosystems services including water regulation and drinking water provision. However, there is concern that climate change could increase rates of litter decomposition and disrupt this carbon sink. Furthermore, it has been argued that the response of these ecosystems in the warmer south west and west of the UK may provide an early analogue for later changes in the more extensive northern peatlands. In order to investigate the effects of climate change on blanket bog litter decomposition, we set-up a litter bag experiment across an altitudinal gradient spanning 200 m of elevation (including a transition from moorland to healthy blanket bog) on Dartmoor, an area of hitherto unstudied, climatically marginal blanket bog in the south west of the UK. At seven sites, water table depth and soil and surface temperature were recorded continuously. Litter bags filled with the litter of three vegetation species dominant on Dartmoor were incubated just below the bog surface and retrieved over a period of 12 months. We found significant differences in the rate of decomposition between species. At all sites, decomposition progressed in the order Calluna vulgaris (dwarf shrub) > Molinia caerulea (graminoid) > Sphagnum (bryophyte). However, while soil temperature did decrease along the altitudinal gradient, being warmer in the lower altitudes, a hypothesised accompanying decrease in decomposition rates did not occur. This could be explained by greater N deposition at the higher elevation sites (estimated

  4. Abundance of Royle’s pika (Ochotona roylei along an altitudinal gradient in Uttarakhand, Western Himalaya

    Directory of Open Access Journals (Sweden)

    Sabuj Bhattacharyya

    2010-06-01

    Full Text Available Abstract The relative abundance of Royle’s pika (Ochotona roylei was studied in a part of the Kedarnath Wildlife Sanctuary, Uttarakhand, West Himalaya along an altitudinal gradient from 2900 to 3650 m a.s.l. Pikas’ detection probability and relative abundance per month and habitat were recorded by monthly surveys consisting of three sampling sessions of four hours each. Food plant species were identified by visual observation and quantified by a standard quadrat method. The highest relative abundance was observed at man-made walls and surroundings in the alpine zone and on broken slopes in the sub-alpine one, whereas alpine meadows showed the lowest abundance. A total of 26 plant species were found to be consumed by pikas. The proportion of forage plants was the highest (77.4% on the rocky slopes of the timberline zone The results of multiple regressions suggest that rock cover is the main factor affecting the relative abundance of Royle’s pika. Rocky areas probably offer both nest-sites and temporary refuges to escape from predators.
    Riassunto Abbondanza relativa del pica di Royle (Ochotona roylei lungo un gradiente altitudinale in Uttarakhand, Himalaya occidentale. In un’area del Kedarnath Wildlife Sanctuary (Uttarakhand, Himalaya occidentale, é stata stimata l’abbondanza relativa del pika di Royle (Ochotona roylei lungo un gradiente altitudinale compreso tra 2900 e 3650 m. Sono stati identificate tre fasce altitudinali e 10 habitat complessivi. La probabilità di osservazione e l’abbondanza relativa dei pika per ciascun mese e habitat sono state stimate tramite censimenti mensili consistenti in tre periodi di 4 ore ciascuno. Le specie vegetali consumate sono state identificate tramite osservazione diretta; la disponibilità è stata quantificata tramite rilievo fitosociologico standard. L’abbondanza relativa maggiore è stata riscontrata nella

  5. Floristic-functional variation of tree component along an altitudinal gradient in araucaria forest areas, in Southern Brazil.

    Science.gov (United States)

    Soboleski, Vanessa F; Higuchi, Pedro; Silva, Ana Carolina DA; Silva, Mariele A F DA; Nunes, Amanda S; Loebens, Rodineli; Souza, Karine DE; Ferrari, Jheniffer; Lima, Carla L; Kilca, Ricardo V

    2017-01-01

    We aimed to investigate the taxonomic and functional variations of tree component of Araucaria Forest (AF) areas located along an altitudinal gradient (700, 900 and 1,600 m asl), in the southern region of Brazil. The functional traits determined were leaf area, specific leaf area, wood density, maximum potential height and dispersal syndromes and deciduousness. The data were analyzed through a functional and taxonomic dissimilarity dendrograms, community-weighted mean trait values, parametric and nonparametric tests, and Principal Component Analysis. The largest floristic-structural similarity was observed between the lower altitude areas (700 and 900 m asl), whose Bray-Curtis distance was 0.63. The area at 700 m asl was characterized by a predominance of deciduous and semi-deciduous species, with a high number of self- and wind-dispersed species, whereas the area at 1,600 m asl exhibited a predominance of animal-dispersed and evergreen species. It was also observed that there were significant variations for leaf traits, basic wood density and maximum potential height. Over all altitudinal gradient, the ordinations indicated that there was no evidence of functional differentiation among dispersal and deciduousness groups. In conclusion, the evaluated Araucaria Forest areas presented high floristic-functional variation of the tree component along the altitudinal gradient.

  6. Tree growth and its climate signal along latitudinal and altitudinal gradients: comparison of tree rings between Finland and the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    L. Lyu

    2017-06-01

    Full Text Available Latitudinal and altitudinal gradients can be utilized to forecast the impact of climate change on forests. To improve the understanding of how these gradients impact forest dynamics, we tested two hypotheses: (1 the change of the tree growth–climate relationship is similar along both latitudinal and altitudinal gradients, and (2 the time periods during which climate affects growth the most occur later towards higher latitudes and altitudes. To address this, we utilized tree-ring data from a latitudinal gradient in Finland and from two altitudinal gradients on the Tibetan Plateau. We analysed the latitudinal and altitudinal growth patterns in tree rings and investigated the growth–climate relationship of trees by correlating ring-width index chronologies with climate variables, calculating with flexible time windows, and using daily-resolution climate data. High latitude and altitude plots showed higher correlations between tree-ring chronologies and growing season temperature. However, the effects of winter temperature showed contrasting patterns for the gradients. The timing of the highest correlation with temperatures during the growing season at southern sites was approximately 1 month ahead of that at northern sites in the latitudinal gradient. In one out of two altitudinal gradients, the timing for the strongest negative correlation with temperature at low-altitude sites was ahead of treeline sites during the growing season, possibly due to differences in moisture limitation. Mean values and the standard deviation of tree-ring width increased with increasing mean July temperatures on both types of gradients. Our results showed similarities of tree growth responses to increasing seasonal temperature between latitudinal and altitudinal gradients. However, differences in climate–growth relationships were also found between gradients due to differences in other factors such as moisture conditions. Changes in the timing of the most

  7. Changes in structure and composition of evergreen forests on an altitudinal gradient in the Venezuelan Guayana Shield

    Directory of Open Access Journals (Sweden)

    Lionel Hernández

    2012-03-01

    Full Text Available There have been several ecological studies in forests of the Guayana Shield, but so far none had examined the changes in structure and composition of evergreen forests with altitude. This study describes and analyzes the structure, species composition and soil characteristics of forest stands at different altitudinal zones in Southeastern Venezuelan Guayana, in order to explain the patterns and the main factors that determine the structure and composition of evergreen forests along the altitudinal gradient. Inventories of 3 948 big (>10cm DBH and 1 328 small (5-10cm DBH woody stems were carried out in eleven plots, ranging from 0.1 to 1.0ha, along a 188km long transect with elevations between 290 and 1 395masl. It has been found that 1 hemiepihytes become more dominant and lianas reduce their dominance with increasing altitude and 2 the forest structure in the study area is size-dependent. Five families and 12 genera represented only 9% of the total number of families and genera, respectively, recorded troughout the gradient, but the two groups of taxa comprised more than 50% of the Importance Value (the sum of the relative density and the relative dominance of all measured stems. Moreover, the results suggest that low species richness seems to be associated with the dominance of one or few species. Stand-level wood density (WD of trees decreased significantly with increasing elevation. WD is an indicator of trees’life history strategy. Its decline suggests a change in the functional composition of the forest with increasing altitude. The Canonical Correspondence Analysis (CCA indicated a distinction of the studied forests on the basis of their altitudinal levels and geographic location, and revealed different ecological responses by the forests, to environmental variables along the altitudinal gradient. The variation in species composition, in terms of basal area among stands, was controlled primarily by elevation and secondarily by rainfall

  8. Características de la avifauna en un gradiente altitudinal de un bosque nublado andino en La Paz, Bolivia

    Directory of Open Access Journals (Sweden)

    Omar Martínez

    2013-04-01

    Full Text Available El presente trabajo analiza la diversidad y composición de la avifauna en tres localidades ubicadas dentro del Parque Nacional y Área Natural de Manejo Integrado de Cotapata, La Paz, Bolivia. Las tres localidades se distribuyeron en gradiente altitudinal y tres tipos de bosques húmedos andinos (ceja de monte a 3170 m, bosque nublado a 2620 m y bosque nublado secundario a 1850 m de la zona Yungas. Se realizó un esfuerzo total de 3286 horas-red niebla, 324 horas de caminatas y 216 horas de conteos por puntos en los tres lugares de estudio. Un total de 220 especies fueron registradas, la mayoría capturadas en redes (100 spp., 45%. Veinticinco familias fueron representadas en las capturas por redes y 42 mediante los censos. Tyrannidae y Thraupidae fueron las más representativas mediante ambos métodos. Las curvas acumulativas de especies fueron similares en todos los sitios. La riqueza de especies para la ceja de monte, bosque nublado y bosque secundario a partir de las capturas y censos fueron de 44, 40, 44 especies y 69, 57, 86 especies, respectivamente. Un total de 16 especies de rango restringido fueron registradas (p.e. Odontophorus balliviani, Andigena cucullata. La diversidad para la ceja de monte fue H´= 1,41; para el bosque nublado (H´= 0,98 y el bosque nublado secundario (H´= 0,96. La diversidad beta fue 0,74 basada en datos de capturas con redes y 0,79 basada en datos de censos en las tres alturas.

  9. Forest structure, diversity and regeneration potential along altitudinal gradient in Dhanaulti of Garhwal Himalaya

    Energy Technology Data Exchange (ETDEWEB)

    Saha, S.; Rajwar, G.S.; Kumar, M.

    2016-07-01

    Aim of the study: The aim of the present study was to understatnd the forest composition, structure, diversity and regeneration potential along altitudinal gradient. Area of study: The study was carried out in Dhanaulti forest which falls under temperate region of Garhwal Himalaya in Uttarakhand state, India. Material and Methods: Vegetation analysis was carried out using 10 quadrats at each altitude using a quadrate size of 10×10 m2. In each quadrate, categories of trees >30 cm cbh were considered as trees, 10-30cm cbh as saplings and <10 cm cbh as seedlings. The data were quantitatively analyzed. Main results: In upper and middle altitudes, Cedrus deodara was reported dominant tree whereas, in lower altitude Quercus leucotrichophora was reported dominant. Tree density was highest in lower altitude which reduced middle and upper altitudes whereas, total basal cover increased with increasing altitude. The increasing total basal cover with altitude could be because of the presence of Cedrus deodara trees having higher girth classes. In tree, sapling and seedling layers, diversity (H) and equitabiltiy (EC) decreased with increasing altitude. However, concentrations of dominace (CD) and beta diversity (BD have shown reverse trend with H and EC which increased with increasing altitudes, in each layer of tree, sapling and seedling. The distribution pattern of most species in all layers of trees, saplings and seedlings was contagious. The regeneration potential of the species has shown that some of the species in the absence of tree layer are still regenerating particularly, Rhododendron arboreum, Benthamidia capitata, Neolitsea pallens etc. It indicates that most of the species are shifting upward as they are getting suitable conditions. Research highlights: Altitude influence species composition, diversity and regeneration potential of species. (Author)

  10. Distribution and diversity of Tardigrada along altitudinal gradients in the Hornsund, Spitsbergen (Arctic

    Directory of Open Access Journals (Sweden)

    Krzysztof Zawierucha

    2015-02-01

    Full Text Available Two transects were established and sampled along altitudinal gradients on the slopes of Ariekammen (77°01′N; 15°31′E and Rotjesfjellet (77°00′N; 15°22′E in Hornsund, Spitsbergen. In total 59 moss, lichen, liverwort and mixed moss–lichen samples were collected and 33 tardigrade species of Hetero- and Eutardigrada were found. The α diversity ranged from 1 to 8 per sample; the estimated number of species based on all analysed samples was 52±17 for the Chao 2 estimator and 41 for the incidence-based coverage estimator. According to the results of detrended canonical correspondence analysis, altitude and type of substratum were the most important factors influencing tardigrade communities in the investigated area. Macrobiotus crenulatus, M. hufelandi hufelandi and Hypsibius pallidus dominated in the lower elevations, whereas Echiniscus wendti and E. merokensis merokensis prevailed in samples from higher plots. Macrobiotus islandicus islandicus was collected most often from mosses collected from rock whereas Isohypsibius coulsoni from mosses collected from soil. Analyses of covariance were employed to test for differences in species richness between the transects in relation to altitude. Contrary to expectations, there were significant differences in species richness between the transects, but richness was not significantly related to altitude. Interestingly, significant effects of colonies of seabirds, little auk (Alle alle, on the tardigrades communities were detected. Additionally, in one of the samples first ever males of Milnesium asiaticum were found. Their measurements and microphotographs are provided herein.

  11. Carbon stocks of three secondary coniferous forests along an altitudinal gradient on Loess Plateau in inland China

    Science.gov (United States)

    Liu, Ning; Nan, Hongwei

    2018-01-01

    Natural forests in inland China are generally distributed in montane area and secondary due to a semi-arid climate and past anthropogenic disturbances. However, quantification of carbon (C) stock in these forests and the role of altitude in determining C storage and its partition among ecosystem components are unclear. We sampled 54 stands of three secondary coniferous forests (Larix principis-rupprechtii (LP) forest, Picea meyerii (PM) forest and Pinus tabulaeformis (PT) forest) on Loess Plateau in an altitudinal range of 1200-2700m a.s.l. C stocks of tree layer, shrub layer, herb layer, coarse wood debris, forest floor and soil were estimated. We found these forests had relatively high total C stocks. Driven by both higher vegetation and soil C stocks, total C stocks of LP and PM forests in the high altitudinal range were 375.0 and 368.4 t C ha-1 respectively, significantly higher than that of PT forest in the low altitudinal range (230.2 t C ha-1). In addition, understory shrubs accounted for about 20% of total biomass in PT forest. The proportions of vegetation to total C stock were similar among in the three forests (below 45%), so were the proportions of soil C stock (over 54%). Necromass C stocks were also similar among these forests, but their proportions to total C stock were significantly lower in LP and PM forests (1.4% and 1.6%) than in PT forest (3.0%). Across forest types, vegetation biomass and soil C stock simultaneously increased with increasing altitude, causing fairly unchanged C partitioning among ecosystem components along the altitudinal gradient. Soil C stock also increased with altitude in LP and PT forests. Forest floor necromass decreased with increasing altitude across the three forests. Our results suggest the important role of the altitudinal gradient in C sequestration and floor necromass of these three forests in terms of alleviated water conditions and in soil C storage of LP and PM forests in terms of temperature change. PMID

  12. Soil carbon stocks along an altitudinal gradient in different land-use categories in Lesser Himalayan foothills of Kashmir

    Science.gov (United States)

    Shaheen, H.; Saeed, Y.; Abbasi, M. K.; Khaliq, A.

    2017-04-01

    The carbon sequestration potential of soils plays an important role in mitigating the effect of climate change, because soils serve as sinks for atmospheric carbon. The present study was conducted to estimate the carbon stocks and their variation with altitudinal gradient in the Lesser Himalayan foothills of Kashmir. The carbon stocks were estimated in different land use categories, namely: closed canopy forests, open forests, disturbed forests, and agricultural lands within the altitudinal range from 900 to 2500 m. The soil carbon content was determined by the Walkley-Black titration method. The average soil carbon stock was found to be 2.59 kg m-2. The average soil carbon stocks in closed canopy forests, open forests, and disturbed forests were 3.39, 2.06, and 2.86 kg m-2, respectively. The average soil carbon stock in the agricultural soils was 2.03 kg m-2. The carbon stocks showed a significant decreasing trend with the altitudinal gradient with maximum values of 4.13 kg m-2 at 900-1200 m a.s.l. and minimum value of 1.55 kg m-2 at 2100-2400 m a.s.l. The agricultural soil showed the least carbon content values indicating negative impacts of soil plowing, overgrazing, and soil degradation. Lower carbon values at higher altitudes attest to the immature character of forest stands, as well as to degradation due to immense fuel wood extraction, timber extraction, and harsh climatic conditions. The study indicates that immediate attention is required for the conservation of rapidly declining carbon stocks in agricultural soils, as well as in the soils of higher altitudes.

  13. Species presence frequency and diversity in different patch types along an altitudinal gradient: Larix chinensis Beissn in Qinling Mountains (China

    Directory of Open Access Journals (Sweden)

    Minyi Huang

    2016-03-01

    Full Text Available Forest communities are mosaic systems composed of patches classified into four different developmental patch types: gap patch (G, building patch (B, mature patch (M and degenerate patch (D. To study the mechanisms maintaining diversity in subalpine coniferous forests, species presence frequency and diversity in the four distinct patch types (G, B, M and D of Larix chinensis conifer forests at three altitudinal gradients in the Qinling Mountains were analyzed. Our results were as follows: (1 Different species (or functional groups had distinct presence frequencies in the four different patch types along the altitudinal gradient; (2 Some species or functional groups (species groups sharing similar traits and responses to the environment only occurred in some specific patches. For seed dispersal, species using wind mainly occurred in G and D, while species using small animals mainly occurred in B and M; (3 Species composition of adjacent patch types was more similar than non-adjacent patch types, based on the lower β diversity index of the former; (4 The maximum numbers of species and two diversity indices (D′ and H′ were found in the middle altitudes. Various gap-forming processes and dispersal limitation may be the two major mechanisms determining species diversity in Larix chinensis coniferous forests at the patch scale.

  14. Growth response of Larix hybrids between L. kaempferi and L. gmelinii var. japonica with altitudinal gradient

    Energy Technology Data Exchange (ETDEWEB)

    Kisanuki, Hiromitsu; Kurahashi, Akio; Takahashi, Yasuo [Tokyo Univ. Forest, Hokkaido (Japan)

    1995-12-31

    To test the adaptability of Japanese larch, Dahurian larch and their hybrid to the environment in Hokkaido, these three materials were planted and surveyed of their survival and growth for 30 years at four elevation in central Hokkaido, northern Japan. Japanese larch showed low adaptation with high mortality affected by voles at every elevation. Dahurian larch has high vole resistance but showed high mortality caused by the infection of Armillaria root rot. Hybrid could persist through low to high elevation. Only hybrid showed enough growth at the highest elevation. Stress tolerance of hybrid was confirmed under high altitudinal condition. 12 refs, 4 figs, 3 tabs

  15. Growth response of Larix hybrids between L. kaempferi and L. gmelinii var. japonica with altitudinal gradient

    Energy Technology Data Exchange (ETDEWEB)

    Kisanuki, Hiromitsu; Kurahashi, Akio; Takahashi, Yasuo [Tokyo Univ. Forest, Hokkaido (Japan)

    1996-12-31

    To test the adaptability of Japanese larch, Dahurian larch and their hybrid to the environment in Hokkaido, these three materials were planted and surveyed of their survival and growth for 30 years at four elevation in central Hokkaido, northern Japan. Japanese larch showed low adaptation with high mortality affected by voles at every elevation. Dahurian larch has high vole resistance but showed high mortality caused by the infection of Armillaria root rot. Hybrid could persist through low to high elevation. Only hybrid showed enough growth at the highest elevation. Stress tolerance of hybrid was confirmed under high altitudinal condition. 12 refs, 4 figs, 3 tabs

  16. Distribution pattern of the threatened Himalayan serow (Capricornis thar) in western midhills of Nepal. An insight for conservation along an altitudinal gradient

    Czech Academy of Sciences Publication Activity Database

    Paudel, Prakash K.; Kindlmann, Pavel

    2012-01-01

    Roč. 20, č. 3 (2012), s. 177-180 ISSN 1617-1381 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : Capricornis thar * Himalaya n serow * Nepal * Midhills * Habitat fragmentation * Altitudinal gradient Subject RIV: EH - Ecology, Behaviour Impact factor: 1.535, year: 2012

  17. Modelling decomposition of standard plant material along an altitudinal gradient: A re-analysis of data of Coûteaux et al.

    NARCIS (Netherlands)

    Braakhekke, W.G.; Bruijn, de A.M.G.

    2007-01-01

    We explored an alternative method to analyse data of Cou¿teaux et al. [2002, Soil Biology and Biochemistry 34, 69-78] on the decomposition of a standard organic material in six soils along an altitudinal gradient in the Venezuelan Andes (65-3968 m a.s.l.). Cou¿teaux et al., fitted separate

  18. Nutrient addition modifies phosphatase activities along an altitudinal gradient in a tropical montane forest in Southern Ecuador

    Directory of Open Access Journals (Sweden)

    Karla eDietrich

    2016-02-01

    Full Text Available Atmospheric nutrient deposition and climate change are expected to endanger the diversity of tropical forest ecosystems. Nitrogen (N deposition might influence nutrient fluxes beyond the N cycle by a concomitant increased demand for other nutritional elements such as phosphorus (P. Organisms might respond to the increased P demand by enhanced activity of enzymes involved in releasing inorganic P from organic matter (OM. Our aims were to assess the effect of i climate shifts (approximated by an altitudinal gradient, and ii nutrient addition (N, P, N+P on phosphatase activity (PA in organic layer and mineral soil of a tropical montane rainforest in Southern Ecuador. A nutrient manipulation experiment (NUMEX was set up along an altitudinal gradient (1000, 2000, and 3000 m a.s.l.. We determined PA and inorganic and total P concentrations. PA at 1000 m was significantly lower (mean ± standard error: 48 ± 20 µmol p-NP g-1 dm h-1 as compared to 2000 m and 3000 m (119 ± 11 and 137 ± 19, respectively. One explanation might be that very rapid decomposition of OM at 1000 m results in very thin organic layers reducing the stabilization of enzymes and thus, resulting in leaching loss of enzymes under the humid tropical climate. We found no effect of N addition on PA neither in the organic layer nor in mineral soil, probably because of the low nutrient addition rates that showed ambiguous results so far on productivity measures as a proxy for P demand. In the organic layers of P and N+P treatments, we found decreased PA and increased concentrations of inorganic P. This indicates that the surplus of inorganic P reduced the biosynthesis of phosphatase enzymes. PA in megadiverse montane rainforests is likely to be unaffected by increased atmospheric N deposition but reduced upon atmospheric P deposition.

  19. The roles of genetic drift and natural selection in quantitative trait divergence along an altitudinal gradient in Arabidopsis thaliana.

    Science.gov (United States)

    Luo, Y; Widmer, A; Karrenberg, S

    2015-02-01

    Understanding how natural selection and genetic drift shape biological variation is a central topic in biology, yet our understanding of the agents of natural selection and their target traits is limited. We investigated to what extent selection along an altitudinal gradient or genetic drift contributed to variation in ecologically relevant traits in Arabidopsis thaliana. We collected seeds from 8 to 14 individuals from each of 14 A. thaliana populations originating from sites between 800 and 2700 m above sea level in the Swiss Alps. Seed families were grown with and without vernalization, corresponding to winter-annual and summer-annual life histories, respectively. We analyzed putatively neutral genetic divergence between these populations using 24 simple sequence repeat markers. We measured seven traits related to growth, phenology and leaf morphology that are rarely reported in A. thaliana and performed analyses of altitudinal clines, as well as overall QST-FST comparisons and correlation analyses among pair-wise QST, FST and altitude of origin differences. Multivariate analyses suggested adaptive differentiation along altitude in the entire suite of traits, particularly when expressed in the summer-annual life history. Of the individual traits, a decrease in rosette leaf number in the vegetative state and an increase in leaf succulence with increasing altitude could be attributed to adaptive divergence. Interestingly, these patterns relate well to common within- and between-species trends of smaller plant size and thicker leaves at high altitude. Our results thus offer exciting possibilities to unravel the underlying mechanisms for these conspicuous trends using the model species A. thaliana.

  20. Altitudinal zonation among lizards of the genus Liolaemus: questions answered and unanswered questions Zonación altitudinal en lagartijas del género Liolaemus: preguntas respondidas y pendientes

    Directory of Open Access Journals (Sweden)

    JOHN H. CAROTHERS

    2001-06-01

    temperaturas ambientales frías determinan que sólo las especies vivíparas puedan sobrevivir arriba de los 2.400 m de altura. Tres especies de Liolaemus se especializan en microhábitats de distribución restringida en el gradiente altitudinal. Liolaemus tenuis se encuentra exclusivamente en la base de árboles, los cuales se distribuyen típicamente debajo de los 1.800 m. Liolaemus leopardinus se especializa en rocas grandes que se encuentran sólo en altitudes mayores. Liolaemus monticola usa rocas pequeñas: la oviparidad determina su límite distribucional superior en dos de los tres transectos examinados, y en el tercero esta especie y su habitat rocoso virtualmente desaparecen arriba de los 1.500 m. La competencia interespecífica entre Liolaemus aparentemente no se relaciona con su distribución altitudinal. No encontramos ejemplos de distribuciones parapátricas entre pares de especies de Liolaemus con similares requerimientos de nicho. Otros investigadores han encontrado que la depredación no se correlaciona con la altitud: su papel en determinar las distribuciones altitudinales de especies depende tanto de las densidades de predadores como de las presas. Concluímos que los factores determinantes de los límites de distribución de las especies de Liolaemus varían dependiendo de sus circunstancias individuales en el tiempo y el espacio: si bien la fisiología puede ser relevante en un transecto, la disponibilidad del microhábitat preferido puede ser importante en otro

  1. Biomass and selected ecological factors of epiphytic bryophyte along altitudinal gradients in Southern Thailand

    Directory of Open Access Journals (Sweden)

    Sahut Chantanaorrapint

    2011-12-01

    Full Text Available Biomass of epiphytic bryophytes was investigated along three altitudinal transects in southern Thailand: TarutaoNational Park (25-700 m, Khao Nan National Park (400-1,300 m, and Khao Luang National Park (400-1,500 m. The dry weightof epiphytic bryophytes per surface area increased from 1.15 g/m2 in the lowland to a maximum 199 g/m2 at the lower montaneforests. The estimation of dry weight per hectare increased along transect from 2.4 to 620 kg. The water storing capacity ofepiphytic bryophytes was about 1.2 to 2.4 times as dry weight and was generally higher in the lower montane forest (up to1,500 l/ha than in the lowland forests. The bark pH of host trees range between 3.19 and 6.84, and show negative correlationwith the altitude (r=-0.635, p<0.05. Air temperature gradually decreases with the increasing altitude ca 0.6°C per 100 m elevation.

  2. Timing and duration of European larch growing season along altitudinal gradients in the Swiss Alps.

    Science.gov (United States)

    Moser, Lea; Fonti, Patrick; Büntgen, Ulf; Esper, Jan; Luterbacher, Jürg; Franzen, Julia; Frank, David

    2010-02-01

    The 2007 European larch (Larix decidua Mill.) growing season was monitored along two elevational transects in the Lötschental valley in the Swiss Alps. Phenological observations and weekly microcore sampling of 28 larch trees were conducted between April and October 2007 at seven study sites regularly spaced from 1350 to 2150 m a.s.l. on northwest- and southeast-facing slopes. The developmental stages of nearly 75,000 individual cells assessed on 1200 thin sections were used to investigate the links between the trees' thermal regimes and growth phases including the beginning and ending of cell enlargement, wall thickening and maturation of the stem wood. Needles appeared approximately 3-4 weeks earlier than stem growth. The duration of ring formation lasted from mid-May to the end of October, with the length of the growing season decreasing along elevation from 137 to 101 days. The onset of the different growing seasons changed by 3-4 days per 100 m elevation; the ending of the growing season, however, appeared minimally related to altitude. If associated with the monitored altitudinal lapse rate of -0.5 degrees C per 100 m, these results translate into a lengthening of the growing season by approximately 7 days per degree Celsius. This study provides new data on the timing and duration of basic growth processes and contributes to quantification of the impacts of global warming on tree growth and productivity.

  3. Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard

    Directory of Open Access Journals (Sweden)

    P. Kotas

    2018-03-01

    Full Text Available The unique and fragile High Arctic ecosystems are vulnerable to global climate warming. The elucidation of factors driving microbial distribution and activity in arctic soils is essential for a comprehensive understanding of ecosystem functioning and its response to environmental change. The goals of this study were to investigate microbial biomass and activity, microbial community structure (MCS, and their environmental controls in soils along three elevational transects in the coastal mountains of Billefjorden, central Svalbard. Soils from four different altitudes (25, 275, 525 and 765 m above sea level were analyzed for a suite of characteristics including temperature regimes, organic matter content, base cation availability, moisture, pH, potential respiration, and microbial biomass and community structure using phospholipid fatty acids (PLFAs. We observed significant spatial heterogeneity of edaphic properties among transects, resulting in transect-specific effects of altitude on most soil parameters. We did not observe any clear elevation pattern in microbial biomass, and microbial activity revealed contrasting elevational patterns between transects. We found relatively large horizontal variability in MCS (i.e., between sites of corresponding elevation in different transects, mainly due to differences in the composition of bacterial PLFAs, but also a systematic altitudinal shift in MCS related to different habitat preferences of fungi and bacteria, which resulted in high fungi-to-bacteria ratios at the most elevated sites. The biological soil crusts on these most elevated, unvegetated sites can host microbial assemblages of a size and activity comparable to those of the arctic tundra ecosystem. The key environmental factors determining horizontal and vertical changes in soil microbial properties were soil pH, organic carbon content, soil moisture and Mg2+ availability.

  4. Toughness of the Virunga mountain gorilla (Gorilla beringei beringei) diet across an altitudinal gradient.

    Science.gov (United States)

    Glowacka, Halszka; McFarlin, Shannon C; Vogel, Erin R; Stoinski, Tara S; Ndagijimana, Felix; Tuyisingize, Deo; Mudakikwa, Antoine; Schwartz, Gary T

    2017-08-01

    The robust masticatory system of mountain gorillas is thought to have evolved for the comminution of tough vegetation, yet, compared to other primates, the toughness of the mountain gorilla diet is unremarkable. This may be a result of low plant toughness in the mountain gorilla environment or of mountain gorillas feeding selectively on low-toughness foods. The goal of this paper is to determine how the toughness of the mountain gorilla diet varies across their habitat, which spans a large altitudinal range, and whether there is a relationship between toughness and food selection by mountain gorillas. We collected data on the following variables to determine whether, and if so how, they change with altitude: leaf toughness of two plant species consumed by mountain gorillas, at every 100 m increase in altitude (2,600-3,700 m); toughness of consumed foods comprising over 85% of the gorilla diet across five vegetation zones; and toughness of unconsumed/infrequently consumed plant parts of those foods. Although leaf toughness increased with altitude, the toughness of the gorilla diet remained similar. There was a negative relationship between toughness and consumption frequency, and toughness was a better predictor of consumption frequency than plant frequency, biomass, and density. Consumed plant parts were less tough than unconsumed/infrequently consumed parts and toughness of the latter increased with altitude. Although it is unclear whether gorillas select food based on toughness or use toughness as a sensory cue to impart other plant properties (e.g., macronutrients, chemicals), our results that gorillas maintain a consistent low-toughness dietary profile across altitude, despite toughness increasing with altitude, suggest that the robust gorilla masticatory apparatus evolved for repetitive mastication of foods that are not high in toughness. © 2017 Wiley Periodicals, Inc.

  5. Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard)

    Science.gov (United States)

    Kotas, Petr; Šantrůčková, Hana; Elster, Josef; Kaštovská, Eva

    2018-03-01

    The unique and fragile High Arctic ecosystems are vulnerable to global climate warming. The elucidation of factors driving microbial distribution and activity in arctic soils is essential for a comprehensive understanding of ecosystem functioning and its response to environmental change. The goals of this study were to investigate microbial biomass and activity, microbial community structure (MCS), and their environmental controls in soils along three elevational transects in the coastal mountains of Billefjorden, central Svalbard. Soils from four different altitudes (25, 275, 525 and 765 m above sea level) were analyzed for a suite of characteristics including temperature regimes, organic matter content, base cation availability, moisture, pH, potential respiration, and microbial biomass and community structure using phospholipid fatty acids (PLFAs). We observed significant spatial heterogeneity of edaphic properties among transects, resulting in transect-specific effects of altitude on most soil parameters. We did not observe any clear elevation pattern in microbial biomass, and microbial activity revealed contrasting elevational patterns between transects. We found relatively large horizontal variability in MCS (i.e., between sites of corresponding elevation in different transects), mainly due to differences in the composition of bacterial PLFAs, but also a systematic altitudinal shift in MCS related to different habitat preferences of fungi and bacteria, which resulted in high fungi-to-bacteria ratios at the most elevated sites. The biological soil crusts on these most elevated, unvegetated sites can host microbial assemblages of a size and activity comparable to those of the arctic tundra ecosystem. The key environmental factors determining horizontal and vertical changes in soil microbial properties were soil pH, organic carbon content, soil moisture and Mg2+ availability.

  6. Precipitation and air temperature control the variations of dissolved organic matter along an altitudinal forest gradient, Gongga Mountains, China.

    Science.gov (United States)

    Hu, Zhaoyong; Wang, Genxu; Sun, Xiangyang

    2017-04-01

    Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) contribute significantly to C and N cycling in forest ecosystems. Little information is available on the variations in the DOC and DON concentrations and depositions in bulk and stand precipitation within forests along an altitudinal gradient. To determine the temporal variations in the DOC and DON concentrations and depositions in different forests and the spatial variations along the elevation gradient, the DOC and DON concentrations and depositions were measured in bulk precipitation, throughfall, and stemflow within three forest types, i.e., broadleaf forest (BLF), broadleaf-coniferous forest (BCF), and coniferous forest (CF), during the wet season (May to October) on Gongga Mountain, China, in 2015. The concentrations of bulk precipitation in BLF, BCF, and CF were 3.92, 4.04, and 2.65 mg L -1 , respectively, for DOC and were 0.38, 0.26, and 0.29 mg L -1 , respectively, for DON. BCF had the highest DOC deposition both in bulk precipitation (45.12 kg ha -1 ) and stand precipitation (98.52 kg ha -1 ), whereas the highest DON deposition was in BLF (3.62 kg ha -1 bulk precipitation and 4.11 kg ha -1 stand precipitation) during the study period. The meteorological conditions of precipitation and air temperature significantly influenced the dissolved organic matter (DOM) depositions along the elevation gradient. The leaf area index did not show any correlation with DOM depositions during the growing season.

  7. Shrub type dominates the vertical distribution of leaf C : N : P stoichiometry across an extensive altitudinal gradient

    Science.gov (United States)

    Zhao, Wenqiang; Reich, Peter B.; Yu, Qiannan; Zhao, Ning; Yin, Chunying; Zhao, Chunzhang; Li, Dandan; Hu, Jun; Li, Ting; Yin, Huajun; Liu, Qing

    2018-04-01

    Understanding leaf stoichiometric patterns is crucial for improving predictions of plant responses to environmental changes. Leaf stoichiometry of terrestrial ecosystems has been widely investigated along latitudinal and longitudinal gradients. However, very little is known about the vertical distribution of leaf C : N : P and the relative effects of environmental parameters, especially for shrubs. Here, we analyzed the shrub leaf C, N and P patterns in 125 mountainous sites over an extensive altitudinal gradient (523-4685 m) on the Tibetan Plateau. Results showed that the shrub leaf C and C : N were 7.3-47.5 % higher than those of other regional and global flora, whereas the leaf N and N : P were 10.2-75.8 % lower. Leaf C increased with rising altitude and decreasing temperature, supporting the physiological acclimation mechanism that high leaf C (e.g., alpine or evergreen shrub) could balance the cell osmotic pressure and resist freezing. The largest leaf N and high leaf P occurred in valley region (altitude 1500 m), likely due to the large nutrient leaching from higher elevations, faster litter decomposition and nutrient resorption ability of deciduous broadleaf shrub. Leaf N : P ratio further indicated increasing N limitation at higher altitudes. Interestingly, drought severity was the only climatic factor positively correlated with leaf N and P, which was more appropriate for evaluating the impact of water status than precipitation. Among the shrub ecosystem and functional types (alpine, subalpine, montane, valley, evergreen, deciduous, broadleaf, and conifer), their leaf element contents and responses to environments were remarkably different. Shrub type was the largest contributor to the total variations in leaf stoichiometry, while climate indirectly affected the leaf C : N : P via its interactive effects on shrub type or soil. Collectively, the large heterogeneity in shrub type was the most important factor explaining the overall leaf C : N : P variations

  8. The Effect of Altitudinal Gradient on the Carbon and Nitrogen Dynamics in Coastal Atlantic Forest of Southeast Brazil

    Science.gov (United States)

    Piccolo, M. D.; Martins, S. C.; Camargo, P. B.; Almeida, D. Q.; Correa, L. O.; Carmo, J. B.; Martinelli, L. A.

    2009-12-01

    The Brazilian Atlantic forest is a vast heterogeneous region with 1.5 million km2, encompassing a large variety of forest physiognomies and compositions, containing large number of species. These forests are distributed in different topographic and climatic conditions, with high levels of precipitation. The rate of deforestation is high, approaching 350 km2 per year, showing be highly fragmented with a large number of species in extinction. The aim of this study was to understanding of the basic biogeochemistry functioning of the coastal Atlantic Forest. The study was carried out in São Paulo State, Brazil (23° 24' S and 45° 11' W). The studied areas were: Restinga Forest at sea level; Lowland Ombrophylus Dense Forest at 100m of altitude asl; Submontana Ombrophylus Dense Forest at 400m of altitude asl and; Montane Ombrophylus Dense Forest at 1000m of altitude asl. A sampling area of 1 ha in each phytophysiognomies was subdivided in contiguous sub-parcels (10 x 10m). The forest floor litter accumulated (0.06m2) was collected monthly (n=15), during 12 months, in each phytophysiognomies. Soils samples (0-0.05m depth) were collected (n=32) from square regular grids, 30m away from each other. Techniques of multivariate like principal components analysis (PCA) were used to determine correlations between the variable. The ordination graphs make possible to observe frequent of standards, representing a significant ratio of the variability of the data. The two first PCA axes cumulatively explained 60% of the total variance of the litter variables. Litter C and δ13C values were strongly influenced by altitude at 1000m. The N and δ15N of litter were influenced by altitude at 100 and 400m. The C/N relation was influenced by altitude at 0m. The lignin was elevated (p<0.01) at sea level in comparison with the other phytophysiognomies. The cellulose values did not vary significantly along the altitudinal gradient. Soil C and N concentrations progressively increased along the

  9. Shrub type dominates the vertical distribution of leaf C : N : P stoichiometry across an extensive altitudinal gradient

    Directory of Open Access Journals (Sweden)

    W. Zhao

    2018-04-01

    Full Text Available Understanding leaf stoichiometric patterns is crucial for improving predictions of plant responses to environmental changes. Leaf stoichiometry of terrestrial ecosystems has been widely investigated along latitudinal and longitudinal gradients. However, very little is known about the vertical distribution of leaf C : N : P and the relative effects of environmental parameters, especially for shrubs. Here, we analyzed the shrub leaf C, N and P patterns in 125 mountainous sites over an extensive altitudinal gradient (523–4685 m on the Tibetan Plateau. Results showed that the shrub leaf C and C : N were 7.3–47.5 % higher than those of other regional and global flora, whereas the leaf N and N : P were 10.2–75.8 % lower. Leaf C increased with rising altitude and decreasing temperature, supporting the physiological acclimation mechanism that high leaf C (e.g., alpine or evergreen shrub could balance the cell osmotic pressure and resist freezing. The largest leaf N and high leaf P occurred in valley region (altitude 1500 m, likely due to the large nutrient leaching from higher elevations, faster litter decomposition and nutrient resorption ability of deciduous broadleaf shrub. Leaf N : P ratio further indicated increasing N limitation at higher altitudes. Interestingly, drought severity was the only climatic factor positively correlated with leaf N and P, which was more appropriate for evaluating the impact of water status than precipitation. Among the shrub ecosystem and functional types (alpine, subalpine, montane, valley, evergreen, deciduous, broadleaf, and conifer, their leaf element contents and responses to environments were remarkably different. Shrub type was the largest contributor to the total variations in leaf stoichiometry, while climate indirectly affected the leaf C : N : P via its interactive effects on shrub type or soil. Collectively, the large heterogeneity in shrub type was the most

  10. Reticulate Pleistocene evolution of Ethiopian rodent genus along remarkable altitudinal gradient.

    Science.gov (United States)

    Bryja, Josef; Kostin, Danila; Meheretu, Yonas; Šumbera, Radim; Bryjová, Anna; Kasso, Mohammed; Mikula, Ondřej; Lavrenchenko, Leonid A

    2018-01-01

    The Ethiopian highlands are the most extensive complex of mountainous habitats in Africa. The presence of the Great Rift Valley (GRV) and the striking elevational ecological gradients inhabited by recently radiated Ethiopian endemics, provide a wide spectrum of model situations for evolutionary studies. The extant species of endemic rodents, often markedly phenotypically differentiated, are expected to possess complex genetic features which evolved asa consequence of the interplay between geomorphology and past climatic changes. In this study, we used the largest available multi-locus genetic dataset of the murid genus Stenocephalemys (347 specimens from ca 40 localities across the known distributional area of all taxa) to investigate the relative importance of disruptive selection, temporary geographic isolation and introgression in their adaptive radiations in the Pleistocene. We confirmed the four main highly supported mitochondrial (mtDNA) clades that were proposed as four species in a previous pilot study: S. albipes is a sister species of S. griseicauda (both lineages are present on both sides of the GRV), while the second clade is formed by two Afro-alpine species, S. albocaudata (east of GRV) and the undescribed Stenocephalemys sp. A (west of GRV). There is a clear elevational gradient in the distribution of the Stenocephalemys taxa with two to three species present at different elevations of the same mountain range. Surprisingly, the nuclear species tree corresponded only a little to the mtDNA tree. Multispecies coalescent models based on six nuclear markers revealed the presence of six separate gene pools (i.e. candidate species), with different topology. Phylogenetic analysis, together with the geographic distribution of the genetic groups, suggests a complex reticulate evolution. We propose a scenario that involves (besides classical allopatric speciation) two cases of disruptive selection along the elevational ecological gradient, multiple crosses of

  11. The Biogeographic Pattern of Microbial Functional Genes along an Altitudinal Gradient of the Tibetan Pasture

    Directory of Open Access Journals (Sweden)

    Qi Qi

    2017-06-01

    Full Text Available As the highest place of the world, the Tibetan plateau is a fragile ecosystem. Given the importance of microbial communities in driving soil nutrient cycling, it is of interest to document the microbial biogeographic pattern here. We adopted a microarray-based tool named GeoChip 4.0 to investigate grassland microbial functional genes along an elevation gradient from 3200 to 3800 m above sea level open to free grazing by local herdsmen and wild animals. Interestingly, microbial functional diversities increase with elevation, so does the relative abundances of genes associated with carbon degradation, nitrogen cycling, methane production, cold shock and oxygen limitation. The range of Shannon diversities (10.27–10.58 showed considerably smaller variation than what was previously observed at ungrazed sites nearby (9.95–10.65, suggesting the important role of livestock grazing on microbial diversities. Closer examination showed that the dissimilarity of microbial community at our study sites increased with elevations, revealing an elevation-decay relationship of microbial functional genes. Both microbial functional diversity and the number of unique genes increased with elevations. Furthermore, we detected a tight linkage of greenhouse gas (CO2 and relative abundances of carbon cycling genes. Our biogeographic study provides insights on microbial functional diversity and soil biogeochemical cycling in Tibetan pastures.

  12. The Biogeographic Pattern of Microbial Functional Genes along an Altitudinal Gradient of the Tibetan Pasture

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Qi; Zhao, Mengxin; Wang, Shiping; Ma, Xingyu; Wang, Yuxuan; Gao, Ying; Lin, Qiaoyan; Li, Xiangzhen; Gu, Baohua; Li, Guoxue; Zhou, Jizhong; Yang, Yunfeng

    2017-06-13

    As the highest place of the world, the Tibetan plateau is a fragile ecosystem. Given the importance of microbial communities in driving soil nutrient cycling, it is of interest to document the microbial biogeographic pattern here. We adopted a microarray-based tool named GeoChip 4.0 to investigate grassland microbial functional genes along an elevation gradient from 3200 to 3800 m above sea level open to free grazing by local herdsmen and wild animals. Interestingly, microbial functional diversities increase with elevation, so does the relative abundances of genes associated with carbon degradation, nitrogen cycling, methane production, cold shock and oxygen limitation. The range of Shannon diversities (10.27–10.58) showed considerably smaller variation than what was previously observed at ungrazed sites nearby (9.95–10.65), suggesting the important role of livestock grazing on microbial diversities. Closer examination showed that the dissimilarity of microbial community at our study sites increased with elevations, revealing an elevation-decay relationship of microbial functional genes. Both microbial functional diversity and the number of unique genes increased with elevations. Furthermore, we detected a tight linkage of greenhouse gas (CO2) and relative abundances of carbon cycling genes. Our biogeographic study provides insights on microbial functional diversity and soil biogeochemical cycling in Tibetan pastures.

  13. Non-sequential fruit tracking by birds along an altitudinal gradient

    Science.gov (United States)

    Hasui, Erica; Ramos, Flavio Nunes; Tamashiro, Jorge Yoshio; Silva, Wesley Rodrigues

    2012-11-01

    Despite landscape-level changes in fruit quantity, food resources may be constantly available to frugivorous animals if they track asynchronous fruit peaks. To investigate fruit availability patterns and their consequences on bird abundance, we tested for the occurrence of seasonal patterns in fruit production at three elevations (range 500-1000 m asl) in the Brazilian Atlantic Forest over three years and compared these patterns among the elevations and years. Fruit production occurred throughout the year and showed only slight seasonality, and only at the two higher elevation sites. Contrary to expectation, fruiting peaks were neither predictable nor complementary. A few plant species (about 5%) contributed disproportionately to the high annual variation of fruit production in plant communities. We found no relationship between fruit production and bird capture rates of both generalist and specialist fruit eating species, suggesting that birds do not track fruit resources along the gradient, at least in some parts of the Atlantic Forest, or in some years. The apparent constancy of fruit availability probably does not stimulate birds to track to other elevations. In addition, plants with high annual variation in fruit production could be influencing and biasing our assessment of this relationship.

  14. Factors controlling soil organic carbon stability along a temperate forest altitudinal gradient

    Science.gov (United States)

    Tian, Qiuxiang; He, Hongbo; Cheng, Weixin; Bai, Zhen; Wang, Yang; Zhang, Xudong

    2016-01-01

    Changes in soil organic carbon (SOC) stability may alter carbon release from the soil and, consequently, atmospheric CO2 concentration. The mean annual temperature (MAT) can change the soil physico-chemical characteristics and alter the quality and quantity of litter input into the soil that regulate SOC stability. However, the relationship between climate and SOC stability remains unclear. A 500-day incubation experiment was carried out on soils from an 11 °C-gradient mountainous system on Changbai Mountain in northeast China. Soil respiration during the incubation fitted well to a three-pool (labile, intermediate and stable) SOC decomposition model. A correlation analysis revealed that the MAT only influenced the labile carbon pool size and not the SOC stability. The intermediate carbon pool contributed dominantly to cumulative carbon release. The size of the intermediate pool was strongly related to the percentage of sand particle. The decomposition rate of the intermediate pool was negatively related to soil nitrogen availability. Because both soil texture and nitrogen availability are temperature independent, the stability of SOC was not associated with the MAT, but was heavily influenced by the intrinsic processes of SOC formation and the nutrient status. PMID:26733344

  15. SOM storage and pool distribution in forest soils along climatic and altitudinal gradients across Switzerland

    Science.gov (United States)

    Gosheva, Sia; Müller, Mirjam; Walthert, Lorenz; Zimmermann, Stephan; Niklaus, Pascal A.; González Domínguez, Beatriz R.; Abiven, Samuel; Hagedorn, Frank

    2016-04-01

    Soil organic matter (SOM) plays a key role for a number of soil and ecosystem functions. Yet our quantitative understanding of the main driving factors is uncertain. SOM consists of a continuum of compounds ranging from slightly altered plant residues, known as particulate OM (POM) to mineral-associated OM (mOM). POM is the most rapidly cycling and hence vulnerable fraction of SOM. Therefore, it might respond particularly sensitive to climate change. In grassland soils, SOM content as well as the contribution of POM was found to increase with increasing elevation, which suggests that climate exerts a major control on SOM stability and storage. Little is known, however, for forest soils where a substantial fraction of POM is stored in the organic layer. In our study based on 1000 soil profiles, we explore the controlling factors of SOM stocks and the distribution of POM in the organic layer as well as within mineral soils in forests across Switzerland. We hypothesize that (i) elevation and hence climate have rather negligible effects on carbon (C) stocks, but exert large effects on SOM quality (contribution of POM, SOM depth distribution, and C/N ratio); (ii) furthermore, we postulate to find an elevational effect on C stocks in the organic layer but not in the mineral soil. We examined SOM stocks in the organic layer and the mineral soil of 1000 soil profiles. Mineral soils (0-20cm) from a subset of 54 sites were separated into free light fraction and occluded light fraction, representing POM, while fine heavy fraction and coarse heavy fraction represented the mineral-associated OM. The sites, all located in Swiss forests, were distributed along a great elevational gradient ranging between 277 and 2207 m a.s.l., and spanning a gradient in mean annual temperatures (MAT) from 0.6 to 11.9 °C, and mean annual precipitation (MAP) from 704 to 2340 mm. Our results indicate that POM and C/N ratio are more closely related to elevation and climate compared to mOM. For C

  16. Controls on soil solution nitrogen along an altitudinal gradient in the Scottish uplands.

    Science.gov (United States)

    Jackson-Blake, L; Helliwell, R C; Britton, A J; Gibbs, S; Coull, M C; Dawson, L

    2012-08-01

    Nitrogen (N) deposition continues to threaten upland ecosystems, contributing to acidification, eutrophication and biodiversity loss. We present results from a monitoring study aimed at investigating the fate of this deposited N within a pristine catchment in the Cairngorm Mountains (Scotland). Six sites were established along an elevation gradient (486-908 m) spanning the key habitats of temperate maritime uplands. Bulk deposition chemistry, soil carbon content, soil solution chemistry, soil temperature and soil moisture content were monitored over a 5 year period. Results were used to assess spatial variability in soil solution N and to investigate the factors and processes driving this variability. Highest soil solution inorganic N concentrations were found in the alpine soils at the top of the hillslope. Soil carbon stock, soil solution dissolved organic carbon (DOC) and factors representing site hydrology were the best predictors of NO(3)(-) concentration, with highest concentrations at low productivity sites with low DOC and freely-draining soils. These factors act as proxies for changing net biological uptake and soil/water contact time, and therefore support the hypothesis that spatial variations in soil solution NO(3)(-) are controlled by habitat N retention capacity. Soil percent carbon was a better predictor of soil solution inorganic N concentration than mass of soil carbon. NH(4)(+) was less affected by soil hydrology than NO(3)(-) and showed the effects of net mineralization inputs, particularly at Racomitrium heath and peaty sites. Soil solution dissolved organic N concentration was strongly related to both DOC and temperature, with a stronger temperature effect at more productive sites. Due to the spatial heterogeneity in N leaching potential, a fine-scale approach to assessing surface water vulnerability to N leaching is recommended over the broad scale, critical loads approach currently in use, particularly for sensitive areas. Copyright © 2012

  17. Assessment of variations in taxonomic diversity, forest structure, and aboveground biomass using remote sensing along an altitudinal gradient in tropical montane forest of Costa Rica

    Science.gov (United States)

    Robinson, C. M.; Saatchi, S. S.; Clark, D.; Fricker, G. A.; Wolf, J.; Gillespie, T. W.; Rovzar, C. M.; Andelman, S.

    2012-12-01

    This research sought to understand how alpha and beta diversity of plants vary and relate to the three-dimensional vegetation structure and aboveground biomass along environmental gradients in the tropical montane forests of Braulio Carrillo National Park in Costa Rica. There is growing evidence that ecosystem structure plays an important role in defining patterns of species diversity and along with abiotic factors (climate and edaphic) control the phenotypic and functional variations across landscapes. It is well documented that strong subdivisions at local and regional scales are found mainly on geologic or climate gradients. These general determinants of biodiversity are best demonstrated in regions with natural gradients such as tropical montane forests. Altitudinal gradients provide a landscape scale changes through variations in topography, climate, and edaphic conditions on which we tested several theoretical and biological hypotheses regarding drivers of biodiversity. The study was performed by using forest inventory and botanical data from nine 1-ha plots ranging from 100 m to 2800 m above sea level and remote sensing data from airborne lidar and radar sensors to quantify variations in forest structure. In this study we report on the effectiveness of relating patterns of tree taxonomic alpha diversity to three-dimensional structure of a tropical montane forest using lidar and radar observations of forest structure and biomass. We assessed alpha and beta diversity at the species, genus, and family levels utilizing datasets provided by the Terrestrial Ecology Assessment and Monitoring (TEAM) Network. Through the comparison to active remote sensing imagery, our results show that there is a strong relationship between forest 3D-structure, and alpha and beta diversity controlled by variations in abiotic factors along the altitudinal gradient. Using spatial analysis with the aid of remote sensing data, we find distinct patterns along the environmental gradients

  18. Pattern of NDVI-based vegetation greening along an altitudinal gradient in the eastern Himalayas and its response to global warming.

    Science.gov (United States)

    Li, Haidong; Jiang, Jiang; Chen, Bin; Li, Yingkui; Xu, Yuyue; Shen, Weishou

    2016-03-01

    The eastern Himalayas, especially the Yarlung Zangbo Grand Canyon Nature Reserve (YNR), is a global hotspot of biodiversity because of a wide variety of climatic conditions and elevations ranging from 500 to > 7000 m above sea level (a.s.l.). The mountain ecosystems at different elevations are vulnerable to climate change; however, there has been little research into the patterns of vegetation greening and their response to global warming. The objective of this paper is to examine the pattern of vegetation greening in different altitudinal zones in the YNR and its relationship with vegetation types and climatic factors. Specifically, the inter-annual change of the normalized difference vegetation index (NDVI) and its variation along altitudinal gradient between 1999 and 2013 was investigated using SPOT-VGT NDVI data and ASTER global digital elevation model (GDEM) data. We found that annual NDVI increased by 17.58% in the YNR from 1999 to 2013, especially in regions dominated by broad-leaved and coniferous forests at lower elevations. The vegetation greening rate decreased significantly as elevation increased, with a threshold elevation of approximately 3000 m. Rising temperature played a dominant role in driving the increase in NDVI, while precipitation has no statistical relationship with changes in NDVI in this region. This study provides useful information to develop an integrated management and conservation plan for climate change adaptation and promote biodiversity conservation in the YNR.

  19. Altitudinal and thermal gradients of hepatic Cyp1A gene expression in natural populations of Salmo trutta from high mountain lakes and their correlation with organohalogen loads

    Energy Technology Data Exchange (ETDEWEB)

    Jarque, Sergio; Gallego, Eva [Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18, 08034-Barcelona, Catalonia (Spain); Bartrons, Mireia; Catalan, Jordi [Center for Advanced Studies of Blanes (CEAB-CSIC), Acces Cala St. Francesc 14, 17300-Blanes, Catalonia (Spain); Grimalt, Joan O. [Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18, 08034-Barcelona, Catalonia (Spain); Pina, Benjamin, E-mail: bpcbmc@cid.csic.e [Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18, 08034-Barcelona, Catalonia (Spain)

    2010-05-15

    The biomarker of xenobiotic exposure cytochrome p450A1 (Cyp1A) was used to analyze the biological response to chemical pollution in Salmo trutta (brown trout) from nine high mountain European lakes in Norway, Tatras, Tyrol, and central Pyrenees. Hepatic Cyp1A mRNA levels correlated both with the reciprocal of absolute annual average air temperatures of the sampled lakes and with muscle concentrations of several hydrophobic organohalogen compounds (OC), including chlorinated polychlorobiphenyls (PCB), DDE, and DDT. The correlation between Cyp1A expression and OC content was observed across the whole temperature range (between -0.7 deg. C and +6.2 deg. C), but also in the absence of any thermal gradient. We concluded that airborne pollutants accumulate in high mountain lake fish at concentrations high enough to increase Cyp1A expression, among other possible effects. As geographical distribution of semi-volatile OC is strongly influenced by air temperatures, future climate modifications will potentially enhance their physiological effects in lake ecosystems. - Altitudinal gradients of hepatic Cyp1A gene expression in mountain trout correlate with geographic and individual organohalogen distribution.

  20. Studies on Colombian cryptogams XX. A transect analysis of the bryophyte vegetation along an altitudinal gradient on the Sierra Nevada de Santa Marta, Colombia

    NARCIS (Netherlands)

    Reenen, van G.B.A.; Gradstein, S.R.

    1983-01-01

    Along an altitudinal transect on the northern slope of the Sierra Nevada de Santa Marta, Colombia, 500-4100 m, five altitudinal bryophyte zones are distinguished – four forest zones and one páramo zone – based on ecosystem relevé analysis concerning species presence, substrate preference and

  1. Soil carbon and nitrogen stocks in forests along an altitudinal gradient in the eastern Himalayas and a meta-analysis of global data.

    Science.gov (United States)

    Tashi, Sonam; Singh, Balwant; Keitel, Claudia; Adams, Mark

    2016-06-01

    High-altitude soils potentially store a large pool of carbon (C) and nitrogen (N). The assessment of total C and N stocks in soils is vital to understanding the C and N dynamics in terrestrial ecosystems. In this study, we examined effects of altitude and forest composition on soil C and N along a transect from 317 to 3300 m a.s.l. in the eastern Himalayas. We used meta-analysis to establish the context for our results on the effects of altitude on soil C, including variation with depth. Total C and N contents of soils significantly increased with altitude, but decreased with soil depth. Carbon and N were similarly correlated with altitude and temperature, and temperature was seemingly the main driver of soil C along the altitudinal gradient. Altitude accounted for 73% of the variation in C and 47% of the variation in N stocks. Soil pH and cation exchange capacity were correlated with both soil C and N stocks. Increases in soil C and N stocks were related to forest composition, forest basal area as well as quantity of leaf litter that were in turn influenced by altitude and temperature. Concentrations of C in foliage increased by 2.1% for every 1000 m rise in altitude, while that in leaf litter increased by 2.3%. © 2016 John Wiley & Sons Ltd.

  2. Concentrations of dissolved organic carbon along an altitudinal gradient from Norway spruce forest to the mountain birch/alpine ecotone in Norway

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, N.; Roesberg, I.; Aamlid, D.

    2005-07-01

    Concentrations of dissolved organic carbon (DOC) in soil water from the base of the soil organic layer were determined at three forest plots along an altitudinal gradient in eastern Norway. The lowest plot, at 830 m above sea level (a.s.l.), was in Norway spruce forest and there were additional plots at the ecotone between Norway spruce and mountain birch at 925 m a.s.l. and at the forest line (1000 m a.s.l.). DOC concentrations in soil water did not decrease uniformly with altitude although tree biomass, above-ground litterfall and the soil C pool all did so. Significant correlations between DOC and (H{sup +}) or electrical conductivity may reflect the contribution of DOC to solution acidity and the anionic charge, respectively. If mean temperature during the growing season increases, tree growth at any given altitude will tend to increase and the spruce-birch ecotone may move to a higher altitude than at present. Increased C inputs as litter to the soil might then lead to increasing DOC concentrations and fluxes in surface waters. (orig.)

  3. Arbuscular mycorrhizal fungal community composition affected by original elevation rather than translocation along an altitudinal gradient on the Qinghai-Tibet Plateau

    Science.gov (United States)

    Yang, Wei; Zheng, Yong; Gao, Cheng; Duan, Ji-Chuang; Wang, Shi-Ping; Guo, Liang-Dong

    2016-11-01

    Elucidating arbuscular mycorrhizal (AM) fungal responses to elevation changes is critical to improve understanding of microbial function in ecosystems under global asymmetrical climate change scenarios. Here we examined AM fungal community in a two-year reciprocal translocation of vegetation-intact soil blocks along an altitudinal gradient (3,200 m to 3,800 m) in an alpine meadow on the Qinghai-Tibet Plateau. AM fungal spore density was significantly higher at lower elevation than at higher elevation regardless of translocation, except that this parameter was significantly increased by upward translocation from original 3,200 m to 3,400 m and 3,600 m. Seventy-three operational taxonomic units (OTUs) of AM fungi were recovered using 454-pyrosequencing of 18S rDNA sequences at a 97% sequence similarity. Original elevation, downward translocation and upward translocation did not significantly affect AM fungal OTU richness. However, with increasing altitude the OTU richness of Acaulosporaceae and Ambisporaceae increased, but the OTU richness of Gigasporaceae and Glomeraceae decreased generally. The AM fungal community composition was significantly structured by original elevation but not by downward translocation and upward translocation. Our findings highlight that compared with the short-term reciprocal translocation, original elevation is a stronger determinant in shaping AM fungal community in the Qinghai-Tibet alpine meadow.

  4. Variations in chemical sexual signals of Psammodromus algirus lizards along an elevation gradient may reflect altitudinal variation in microclimatic conditions

    Science.gov (United States)

    Martín, José; Javier Zamora-Camacho, Francisco; Reguera, Senda; López, Pilar; Moreno-Rueda, Gregorio

    2017-04-01

    Chemical signals used in intraspecific communication are expected to evolve or to show phenotipic plasticity to maximize efficacy in the climatic conditions of a given environment. Elevational environmental gradients in mountains provide a good opportunity to test this hypothesis by examining variation in characteristics of signals in species found across different elevations with different climatic conditions. We analyzed by gas chromatography-mass spectrometry (GC-MS) the lipophilic fraction of the femoral gland secretions of male lizards Psammodromus algirus (Fam. Lacertidae) from six localities located along a 2200 m elevational gradient at Sierra Nevada Mountains (SE Spain). There was elevational clinal variation in climatic variables, number of femoral pores and in the relative proportions of some classes of compounds (i.e., ethyl esters of fatty acids, waxy esters, and aldehydes) but not others. We discuss how this variation would result in different physicochemical properties of the entire femoral secretion, which might help optimize the efficacy of chemical signals under the particular microclimatic conditions at each elevation.

  5. Altitudinal gradients, midwinter melt, and wind effects on snow accumulation in semiarid midlatitude Andes under La Niña conditions

    Science.gov (United States)

    Ayala, A.; McPhee, J.; Vargas, X.

    2014-04-01

    The Andes Cordillera remains a sparsely monitored and studied snow hydrology environment in comparison to similar mountain ranges in the Northern Hemisphere. In order to uncover some of the key processes driving snow water equivalent (SWE) spatial variability, we present and analyze a distributed SWE data set, sampled at the end of accumulation season 2011. Three representative catchments across the region were monitored, obtaining measurements in an elevation range spanning 2000 to 3900 m asl and from 32.4° to 34.0°S in latitude. Climatic conditions during this season corresponded to a moderate La Niña phenomenon, which is generally correlated with lower-than normal accumulation. Collected measurements can be described at the regional and watershed extents by altitudinal gradients that imply an increase by a factor of two in snow depth between 2200 and 3000 m asl, though with significant variability at the upper sites. In these upper sites, we found north-facing, wind-sheltered slopes showing 25% less average SWE values than south-facing, wind-exposed ones. This suggests that under these conditions, solar radiation dominated wind transport effects in controlling end-of-winter variability. Nevertheless, we found clusters of snow depth measurements above 3000 m asl that can be explained by wind exposure differences. This is the first documented snow depth data set of this spatial extent for this region, and it is framed within an ongoing research effort aimed at improving understanding and modeling of snow hydrology in the extratropical Andes Cordillera.

  6. Efeito do gradiente altitudinal/latitudinal sobre espécies de aves florestais da família Furnariidae na Bacia do Rio Tibagi, Paraná, Brasil Effect of altitudinal/latitudinal gradient about forest ovenbirds species (Aves: Furnariidae in the Tibagi river basin, Paraná, Brazil

    Directory of Open Access Journals (Sweden)

    Fernando de L. Fávaro

    2006-03-01

    Full Text Available Variações na riqueza e abundância de Furnariidae florestais foram analisadas ao longo do gradiente altitudinal/latitudinal da bacia do rio Tibagi (BRT, Paraná, Brasil. A Floresta Ombrófila Mista (1060 m a.n.m. é a formação dominante no sul da BRT, enquanto que a Floresta Estacional Semidecidual (298 m a.n.m., ocorre no norte. O número total de espécies obtidas na BRT foi 14. A riqueza e a abundância de Furnariidae foram maiores no sul (12 espécies, IPA = 2,01 do que no norte (cinco espécies, IPA = 0,45 da BRT. As similaridades também foram altas entre o sul e o centro da BRT. A estrutura da comunidade de Furnariidae também apresentou correlação positiva entre o sul e o centro da BRT (coeficiente de correlação por postos de Spearman; r s = 0,96, r s = 0,89, r s = 1,00. As relações evolutivas de alguns representantes de Furnariidae com o sul da América do Sul e com os Andes podem explicar a maior presença desta família no sul da BRT. Um outro aspecto que também pode ajudar a explicar os resultados apresentados por Furnariidae são as semelhanças entre a Floresta Ombrófila Mista do sul da BRT e outras florestas temperadas da América do Sul.Variations in richness and abundance of forest ovenbirds (Aves: Furnariidae were studied along an altitudinal/latitudinal gradient of the Tibagi river basin (TRB, southern Brazil. Mixed Temperate Rain Forest (1060 m a.s.l. is the dominant forest in the southern TRB while Seasonal Semideciduous Forest (298 m a.s.l. occurs in the northern. The total number of species obtained in the TRB was 14. Richness and Abundance of Furnariidae were greater in the southern (12 species, IPA = 2.01 than in the northern (five species, IPA = 0.45 TRB. Similarities were also greatest in the southern and in the middle TRB. The community structure of Furnariidae also presented a positive correlation between the southern and the middle TRB (Spearman's rank correlation coefficient; r s = 0.96, r s = 0.89, r s

  7. DISTRIBUIÇÃO E RIQUEZA DE ESPÉCIES ARBÓREAS RARAS EM FRAGMENTOS DE FLORESTA OMBRÓFILA MISTA AO LONGO DE UM GRADIENTE ALTITUDINAL, EM SANTA CATARINA

    Directory of Open Access Journals (Sweden)

    Tiago de Souza Ferreira

    2015-06-01

    Full Text Available RESUMOEste estudo teve por objetivo analisar como a distribuição e riqueza de espécies raras em fragmentos de Floresta Ombrófila Mista ocorrem ao longo de um gradiente altitudinal. Para isso, espécies arbóreas (diâmetro à altura do peito > 5 cm foram amostradas em 10 fragmentos florestais localizados em diferentes pisos altitudinais do Planalto Sul-Catarinense, em uma área total de 10 ha. As espécies que apresentaram número de indivíduos igual ou inferior a 2 em pelo menos um fragmento foram classificadas como raras. A distribuição das espécies foi verificada por meio de dendrograma construído a partir do índice de distância florística de Jaccard e do algoritmo de agrupamento UPGMA. A riqueza total de espécies por fragmento e o número de espécies raras foram comparados entre as subformações montana e alto-montana, por meio do teste de Mann-Whitney (U. As relações entre altitude e os valores de riqueza total e número de espécies raras em cada fragmento foram determinadas por regressões lineares simples. Os resultados indicaram a formação de dois grandes grupos de espécies raras em função do piso altitudinal. Apesar de a riqueza total das comunidades reduzir com o aumento da altitude, o número de espécies raras não apresentou alterações significativas. Conclui-se que na região do Planalto Sul-Catarinense os fragmentos de Floresta Ombrófila Mista apresentam diferentes conjunto de espécies arbóreas raras de acordo com a altitude e que a diminuição da riqueza das comunidades com o aumento do piso altitudinal não é acompanhada pela redução do número de espécies raras.

  8. Ampliación del ámbito geográfico-altitudinal y uso de hábitats suburbanos por la mascarita pico grueso (Geothlypis poliocephala Geographic-altitudinal range extension and suburban habitat use of the Grey-crowned Yellowthroat (Geothlypis poliocephala

    Directory of Open Access Journals (Sweden)

    Ian MacGregor-Fors

    2008-12-01

    Full Text Available Se presenta el primer registro de la mascarita pico grueso (Geothlypis poliocephala para la región del Eje Neovolcánico Transversal, México. Los sitios donde registramos/capturamos esta especie se encuentran en los suburbios de la ciudad de Morelia, 427 m arriba del ámbito altitudinal descrito para la especie. Esto puede deberse a 2 factores: 1 la urbanización que genera hábitats propicios para la especie en su periferia, y 2 el incremento de la temperatura en la región en la que se encuentra la ciudad de Morelia. Ambos factores facilitan que esta especie de tierras bajas pueda habitar en áreas de mayor altitud. Así, nuestros registros sugieren que la mascarita pico grueso puede catalogarse como especie potencial a utilizar hábitats suburbanos cuando éstos son similares a los hábitats en los que se distribuye de manera natural.The first record of the Grey-crowned Yellowthroat (Geothlypis poliocephala in the Transmexican Volcanic Belt biogeographic region (Mexico, within the Morelia city suburbs is presented. Sites were this parulid was sighted / captured were located 427 m higher than its described altitudinal range. This could be due to 2 factors: 1 urbanization generates suitable habitats for this species in periurban areas, and 2 temperature values have increased in the region where the city of Morelia is located. These factors allow that a lowland bird species can inhabit in more elevated areas. Thus, our records suggest that the Grey-crowned Yellowthroat can be catalogued as potential to use suburban environments when these are similar to those used by the species on its natural distribution area.

  9. Escorrentía y erosión a lo largo de un gradiente climático-altitudinal efecto por el pastoreo en el desierto de Judea

    Directory of Open Access Journals (Sweden)

    Artemi Cerdà

    1999-01-01

    Full Text Available Los suelos del Desierto de Judea generan rápidos encharcamientos y abundantes escorrentías, lo que es debido a las ínfimas tasas de infiltración y a curvas de escorrentía de gran pendiente que alcanzan súbitamente las tasas máximas ante chaparrones simulados de 50,36 mm h-1 de intensidad y 45 minutos de duración.Se ha comprobado que el clima determina las características de los suelos y el comportamiento de los procesos geomorfológicos. A lo largo del gradiente climático estudiado las tasas de infiltración decrecen con la precipitación, mientras que las escorrentías, la salinidad de éstas y las pérdidas de suelo aumentan. Además del clima, el uso antrópico influye drásticamente en la respuesta del suelo ante la lluvia. Así, la influencia del clima se ve alterada por el sobrepastoreo, ya que éste modifica la composición florística, la cubierta vegetal y las costras superficiales, con lo que se favorece la erosión del suelo.

  10. Anfibios de las Sierras Pampeanas Centrales de Argentina: diversidad y distribución altitudinal

    Directory of Open Access Journals (Sweden)

    Julián N. Lescano

    2015-09-01

    Full Text Available Amphibians from Sierras Pampeanas Centrales of Argentina: diversity and altitudinal distribution. Sierras Pampeanas Centrales (SPC mountains are located in Córdoba and San Luis provinces (Argentina and represent an area of unique biogeographic importance. In this paper we provide a synthesis about the knowledge of diversity and altitudinal distribution of anurans that inhabit SPC mountains. We compiled a species list through different information sources (field data, biological collections and bibliography. Using this information we characterize altitudinal distribution range of each species and analyze associations between species richness and composition and altitude gradient. We recorded 24 amphibians species belonging to five families. These species are heterogeneously distributed over the altitude gradient of SPC. We detect a linear negative relationship between altitude and species richness and defined assemblages associated with different altitude sectors. The results obtained in the paper represent basic information that will be useful to evaluate anthropogenic impact on this particular and fragile mountain system.

  11. Altitudinal distribution limits of aquatic macroinvertebrates

    DEFF Research Database (Denmark)

    Madsen, Philip B.; Morabowen, Andrés; Andino, Patricio

    2015-01-01

    1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates...... relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits....

  12. Doppia oscillazione diurna della pressione atmosferica e del gradiente verticale del campo elettromagnetico

    Directory of Open Access Journals (Sweden)

    R. JANESELLI

    1968-06-01

    Full Text Available After having stated the essential characteristics about the
    double diurnal oscillation of the atmospheric pressure over the whole Earth's
    surface, using the barograms of the metereological Observatory of Istituto
    Cavanis in Venice, there are drawn the diagrams of the hour-averages for
    the single months from the year 1959 to the year 19(57.
    The same monthly and annual diagrams are drawn for the vertical gradient
    of the electro-atmospheric field for the period 1963-1967.
    The parallelism between the two series of diagrams is good, and almost
    perfect between the two diagrams which contain all the considered measures.
    Then there is a short mention about the structure of the electricatmospheric
    field of the Earth, as it is furnished by the last discoveries,
    reached by the meteorological rockets and by the artificial satellites. As a conclusion there is noticed that, with mueh of probability, the doublé
    oscillation of the two parameters considered is produced by the sanie causes,
    especially by the atinospheric tides and by the electric fields, produced by
    the same tides.

  13. Cultivable bacterial diversity along the altitudinal zonation and vegetation range of tropical Eastern Himalaya

    Directory of Open Access Journals (Sweden)

    Nathaniel A. Lyngwi

    2013-03-01

    that this is a biome with a vast reservoir of bacteria which decrease with increasing altitudes, and highlights the microbiological importance of the poorly studied Eastern Himalayan range, justifying efforts to explore the prevalence of novel species in the biome.La parte noreste de la India se extiende sobre una superficie de 262 379km² en la cordillera oriental del Himalaya. Es un punto de acceso con altos niveles de biodiversidad y endemismo; desafortunadamente, también es una zona poco conocida, sobre todo su diversidad microbiana. En este estudio se evaluó la diversidad de bacterias cultivables del suelo, su diversidad y distribución de las tierras bajas a las altas (34 a 3 990m.s.n.m. Se caracterizaron los parámetros físico-químicos del suelo y tipos de bosques a lo largo del gradiente altitudinal y se correlacionaron con la distribución y diversidad bacteriana. Los microbios del suelo se cultivaron en placas de agar enriquecido Muller Hinton y Luria-Bertani, e inicialmente se caracterizaron mediante métodos bioquímicos. Parámetros tales como actividad de la deshidrogenasa y ureasa, temperatura, contenido de humedad y de carbono, pH y densidad aparente del suelo se midieron en cada sitio. Aislamientos representativos también se sometieron al análisis secuencial de 16S rADN. Un total de 155 aislamientos bacterianos cultivables se caracterizaron para estimar los índices de riqueza, equidad y diversidad. Los bosques tropicales y subtropicales albergan una mayor diversidad bacteriana en comparación con los bosques templados de pino y coníferas, y los bosques subalpinos de rododendro. El análisis filogenético de 16S rARN reveló que Firmicutes fue el grupo más común, seguido de Proteobacteria y Bacteroidetes. Especies pertenecientes a los géneros Bacillus y Pseudomonas fueron las más abundantes. Las UFC bacterianas mostraron una positiva pero insignificante correlación con los parámetros del suelo, tales como pH (r=0.208, temperatura (r=0

  14. Fluid inclusions study in thermal gradient wells, Nevado del Ruiz Volcano

    International Nuclear Information System (INIS)

    Uruena Suarez, Cindy L; Zuluaga, Carlos A; Molano, Juan Carlos

    2012-01-01

    A fluid inclusions study in the Nevado del Ruiz volcano hydrothermal system allowed to characterize fluids involved in the evolution of the geothermal system. Fluid inclusions hosted in quartz, plagioclase and carbonate from samples of the deepest parts of three thermal gradient wells were analyzed to understand fluid-rock interaction. Fluid inclusions hosted in carbonate veins with coloform microestructure represent hydrothermal fluids with temperatures higher than 250 Celsius degrade. This interpretation is supported by microprobe and cathodoluminescence analysis that also indicate a hydrothermal origin for the veins. Fluid inclusions hosted in quartz (mylonite) were originated by metamorphic fluids and fluid inclusions hosted in plagioclase (andesitic lavas) are considered to be originated from magmatic fluids (H 2 O + CO 2 system).

  15. Comparación de los patrones electroforéticos de proteínas en extractos de hojas de Senecio niveoaureus Cuatr . en un gradiente altitudinal en el Páramo de Chingaza (Colombia

    Directory of Open Access Journals (Sweden)

    Fagua Alvarez Florez

    2000-01-01

    Full Text Available En los ecosistemas de alta montaña (páramo, las plantas están expuestas a temperaturasbajas en horas nocturnas. En este trabajo se comparan, por primera vez, los patroneselectroforéticos de proteínas de apoplasto en Espeletia killipii, (caulirrósula y de Senecioniveoaureus(acaule. Estas especies presentan principalmente proteínas de pesos moleculares de35 a 11 kDa. Proteínas con pesos moleculares similares se han descrito como proteínasanticongelantes (AFP en peces del ártico y en el apoplasto de plantas de zonas templadas.Algunos extractos analizados presentaron actividad beta 1-3 glucanasa y quitinasa (enzimasrelacionadas con proteínas de protección a temperaturas bajas. Mediante las metodologíasConA-peroxidasa y Schiff, se determinó que algunas proteínas presentes en los extractosapoplásticos tienen carácter glicoproteico.

  16. Altitudinal patterns of plant diversity on the Jade Dragon Snow Mountain, southwestern China.

    Science.gov (United States)

    Xu, Xiang; Zhang, Huayong; Tian, Wang; Zeng, Xiaoqiang; Huang, Hai

    2016-01-01

    Understanding altitudinal patterns of biological diversity and their underlying mechanisms is critically important for biodiversity conservation in mountainous regions. The contribution of area to plant diversity patterns is widely acknowledged and may mask the effects of other determinant factors. In this context, it is important to examine altitudinal patterns of corrected taxon richness by eliminating the area effect. Here we adopt two methods to correct observed taxon richness: a power-law relationship between richness and area, hereafter "method 1"; and richness counted in equal-area altitudinal bands, hereafter "method 2". We compare these two methods on the Jade Dragon Snow Mountain, which is the nearest large-scale altitudinal gradient to the Equator in the Northern Hemisphere. We find that seed plant species richness, genus richness, family richness, and species richness of trees, shrubs, herbs and Groups I-III (species with elevational range size 500 m, respectively) display distinct hump-shaped patterns along the equal-elevation altitudinal gradient. The corrected taxon richness based on method 2 (TRcor2) also shows hump-shaped patterns for all plant groups, while the one based on method 1 (TRcor1) does not. As for the abiotic factors influencing the patterns, mean annual temperature, mean annual precipitation, and mid-domain effect explain a larger part of the variation in TRcor2 than in TRcor1. In conclusion, for biodiversity patterns on the Jade Dragon Snow Mountain, method 2 preserves the significant influences of abiotic factors to the greatest degree while eliminating the area effect. Our results thus reveal that although the classical method 1 has earned more attention and approval in previous research, method 2 can perform better under certain circumstances. We not only confirm the essential contribution of method 1 in community ecology, but also highlight the significant role of method 2 in eliminating the area effect, and call for more

  17. Altitudinal, seasonal and interannual shifts in microbial communities and chemical composition of soil organic matter in Alpine forest soils

    Czech Academy of Sciences Publication Activity Database

    Siles, J.A.; Cajthaml, Tomáš; Filipová, Alena; Minerbi, S.; Margesin, R.

    2017-01-01

    Roč. 112, SEP 2017 (2017), s. 1-13 ISSN 0038-0717 Institutional support: RVO:61388971 Keywords : Elevational (altitudinal) gradient * Forest * Microbial communit Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 4.857, year: 2016

  18. ZONIFICACIÓN ALTITUDINAL PROVISIONAL DE Abies religiosa EN UN ÁREA CERCANA A LA RESERVA DE LA BIÓSFERA DE LA MARIPOSA MONARCA, MICHOACÁN

    Directory of Open Access Journals (Sweden)

    Dante Castellanos-Acuña

    2014-01-01

    Full Text Available E l objetivo del presente trabajo fue determinar la existencia de diferenciación morfológica (como indicador de variación genética entre poblaciones de Abies religiosa , con la finalidad de delimitar una zonificación altitudinal para decidir el movimiento de semillas en los progra - mas de reforestación. Se recolectaron y analizaron morfológicamente ramas y conos de 11 in - dividuos de 15 poblaciones de A. religiosa en el cerro de San Andrés, municipio de Hidalgo, Michoacán (cercano a la Reserva de la Biósfera de la Mariposa Monarca, a lo largo de un transecto altitudinal (2,850-3,550 m, una población cada 50 m. La diferenciación morfológica significativa entre poblacio - nes se determinó a lo largo del gradiente altitudinal; las poblaciones de baja altitud tienen acículas más cortas y conos más largos que las poblaciones de elevada altitud. Se sugiere delimitar tres zonas altitu - dinales provisionales: 2,800 a 3,050; 3,050 a 3,300; y 3,300 a 3,550 m. Ignorando el cambio climático, se sugiere reforestar cada zona con planta originada de la semilla en la misma zona. Considerando el cambio climático, se sugiere realizar migración asistida altitudinalmente, plantando sitios en la zona inmediata superior a la zona donde la semilla se recolecte.

  19. Woody vegetation status on different altitudinal gradients of an ...

    African Journals Online (AJOL)

    Journal of Research in Forestry, Wildlife and Environment. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 8, No 1 (2016) >. Log in or Register to get access to full text downloads.

  20. Effects of habitat structure and altitudinal gradients on avian species ...

    African Journals Online (AJOL)

    ... effect on bird species diversity. Bird species diversity increased with increase in tree height. A significant decline in bird species diversity with increased number of trees and canopy cover was noted. This result probably suggests an accumulation of forest edge species and generalist species in the less forested habitat.

  1. Animal Fascioliasis: Perspectives from high altitudinal regions.

    Science.gov (United States)

    Lyngdoh, Damanbha; Sharma, Sunil; Roy, Bishnupada; Tandon, Veena

    2016-12-15

    The parasitic flukes of the genus Fasciola (Platyhelminthes: Trematoda: Digenea) cause fascioliasis or liver-rot disease in ruminant livestock in tropical and sub-tropical regions of the world. Classically, two species of Fasciola- F. hepatica and F. gigantica, are universally recognized as taxonomically valid species. Our survey studies on ovid and bovid animals including yak and mithun from high altitudinal mountainous regions in Northeast India revealed the occurrence of Fasciola gigantica and also Fasciola sp.- an intermediate form, at altitudes between 5000 and 14,085 feet above sea level (asl). Two morphotypes- F. hepatica - like and F. gigantica - like, of Fasciola species were reported from the high altitudinal areas of Northeast India; most of these locales constitute new-locality and first records for the occurrence of these liver flukes. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. A reconstruction of Colombian biomes derived from modern pollen data along an altitude gradient

    NARCIS (Netherlands)

    Marchant, R.; Berrío, J.C.; Cleef, A.M.; Duivenvoorden, J.; Helmens, K.; Hooghiemstra, H.; Kuhry, P.; Melief, B.; Schreve-Brinkman, E.; Geel, van B.; Reenen, van G.; Hammen, van der T.

    2001-01-01

    Biomes are reconstructed in Colombia from modern (core-top) pollen data derived from 22 sites along an altitudinal gradient (2000–4100 m) that encompasses the tree line. The `biomization' methodology is described in a stepwise manner that details the reconstruction of vegetation along an altitudinal

  3. Differences between tree species seedling and adult altitudinal distribution in mountain foests during the recent warm period (1986-2006)

    DEFF Research Database (Denmark)

    Lenoir, Jonathan; Gégout, Jean-Claude; Pierrat, Jean-Claude

    2009-01-01

    Spatial fingerprints of climate change on tree species distribution are usually detected at latitudinal or altitudinal extremes (arctic or alpine tree line), where temperatures play a key role in tree species distribution. However, early detection of recent climate change effects on tree species...... distribution across the overall temperature gradient remains poorly explored. Within French mountain forests, we investigated altitudinal distribution differences between seedling (≤50 cm tall and >1 yr old) and adult (>8 m tall) life stages for 17 European tree taxa, encompassing the entire forest elevation...... range from lowlands to the subalpine vegetation belt (50-2250 m a.s.l.) and spanning the latitudinal gradient from northern temperate to southern Mediterranean forests. We simultaneously identified seedlings and adults within the same vegetation plots. These twin observations gave us the equivalent...

  4. Asymmetric changes of growth and reproductive investment herald altitudinal and latitudinal range shifts of two woody species.

    Science.gov (United States)

    Matías, Luis; Jump, Alistair S

    2015-02-01

    Ongoing changes in global climate are altering ecological conditions for many species. The consequences of such changes are typically most evident at the edge of the geographical distribution of a species, where range expansions or contractions may occur. Current demographical status at geographical range limits can help us to predict population trends and their implications for the future distribution of the species. Thus, understanding the comparability of demographical patterns occurring along both altitudinal and latitudinal gradients would be highly informative. In this study, we analyse the differences in the demography of two woody species through altitudinal gradients at their southernmost distribution limit and the consistency of demographical patterns at the treeline across a latitudinal gradient covering the complete distribution range. We focus on Pinus sylvestris and Juniperus communis, assessing their demographical structure (density, age and mortality rate), growth, reproduction investment and damage from herbivory on 53 populations covering the upper, central and lower altitudes as well as the treeline at central latitude and northernmost and southernmost latitudinal distribution limits. For both species, populations at the lowermost altitude presented older age structure, higher mortality, decreased growth and lower reproduction when compared to the upper limit, indicating higher fitness at the treeline. This trend at the treeline was generally maintained through the latitudinal gradient, but with a decreased growth at the northern edge for both species and lower reproduction for P. sylvestris. However, altitudinal and latitudinal transects are not directly comparable as factors other than climate, including herbivore pressure or human management, must be taken into account if we are to understand how to infer latitudinal processes from altitudinal data. © 2014 John Wiley & Sons Ltd.

  5. Changes of arthropod diversity across an altitudinal ecoregional zonation in Northwestern Argentina

    Directory of Open Access Journals (Sweden)

    Andrea X. González-Reyes

    2017-12-01

    Full Text Available This study examined arthropod community patterns over an altitudinal ecoregional zonation that extended through three ecoregions (Yungas, Monte de Sierras y Bolsones, and Puna and two ecotones (Yungas-Monte and Prepuna of Northwestern Argentina (altitudinal range of 2,500 m, and evaluated the abiotic and biotic factors and the geographical distance that could influence them. Pitfall trap and suction samples were taken seasonally in 15 sampling sites (1,500–4,000 m a.s.l during one year. In addition to climatic variables, several soil and vegetation variables were measured in the field. Values obtained for species richness between ecoregions and ecotones and by sampling sites were compared statistically and by interpolation–extrapolation analysis based on individuals at the same sample coverage level. Effects of predictor variables and the similarity of arthropods were shown using non-metric multidimensional scaling, and the resulting groups were evaluated using a multi-response permutation procedure. Polynomial regression was used to evaluate the relationship between altitude with total species richness and those of hyperdiverse/abundant higher taxa and the latter taxa with each predictor variable. The species richness pattern displayed a decrease in species diversity as the elevation increased at the bottom wet part (Yungas of our altitudinal zonation until the Monte, and a unimodal pattern of diversity in the top dry part (Monte, Puna. Each ecoregion and ecotonal zone evidenced a particular species richness and assemblage of arthropods, but the latter ones displayed a high percentage of species shared with the adjacent ecoregions. The arthropod elevational pattern and the changes of the assemblages were explained by the environmental gradient (especially the climate in addition to a geographic gradient (the distance of decay of similarity, demonstrating that the species turnover is important to explain the beta diversity along the

  6. Altitudinal variation in soil organic carbon stock in coniferous subtropical and broadleaf temperate forests in Garhwal Himalaya

    Directory of Open Access Journals (Sweden)

    Kumar Munesh

    2009-08-01

    Full Text Available Abstract Background The Himalayan zones, with dense forest vegetation, cover a fifth part of India and store a third part of the country reserves of soil organic carbon (SOC. However, the details of altitudinal distribution of these carbon stocks, which are vulnerable to forest management and climate change impacts, are not well known. Results This article reports the results of measuring the stocks of SOC along altitudinal gradients. The study was carried out in the coniferous subtropical and broadleaf temperate forests of Garhwal Himalaya. The stocks of SOC were found to be decreasing with altitude: from 185.6 to 160.8 t C ha-1 and from 141.6 to 124.8 t C ha-1 in temperature (Quercus leucotrichophora and subtropical (Pinus roxburghii forests, respectively. Conclusion The results of this study lead to conclusion that the ability of soil to stabilize soil organic matter depends negatively on altitude and call for comprehensive theoretical explanation

  7. Parallel altitudinal clines reveal trends in adaptive evolution of genome size in Zea mays

    Science.gov (United States)

    Berg, Jeremy J.; Birchler, James A.; Grote, Mark N.; Lorant, Anne; Quezada, Juvenal

    2018-01-01

    While the vast majority of genome size variation in plants is due to differences in repetitive sequence, we know little about how selection acts on repeat content in natural populations. Here we investigate parallel changes in intraspecific genome size and repeat content of domesticated maize (Zea mays) landraces and their wild relative teosinte across altitudinal gradients in Mesoamerica and South America. We combine genotyping, low coverage whole-genome sequence data, and flow cytometry to test for evidence of selection on genome size and individual repeat abundance. We find that population structure alone cannot explain the observed variation, implying that clinal patterns of genome size are maintained by natural selection. Our modeling additionally provides evidence of selection on individual heterochromatic knob repeats, likely due to their large individual contribution to genome size. To better understand the phenotypes driving selection on genome size, we conducted a growth chamber experiment using a population of highland teosinte exhibiting extensive variation in genome size. We find weak support for a positive correlation between genome size and cell size, but stronger support for a negative correlation between genome size and the rate of cell production. Reanalyzing published data of cell counts in maize shoot apical meristems, we then identify a negative correlation between cell production rate and flowering time. Together, our data suggest a model in which variation in genome size is driven by natural selection on flowering time across altitudinal clines, connecting intraspecific variation in repetitive sequence to important differences in adaptive phenotypes. PMID:29746459

  8. Altitudinal and temporal distribution of Plagiometriona Spaeth, 1899 (Coleoptera, Chrysomelidae, Cassidinae) in a tropical forest in southeast Brazil.

    Science.gov (United States)

    Flinte, Vivian; de Freitas, Sama; de Macedo, Margarete Valverde; Monteiro, Ricardo Ferreira

    2011-01-01

    Species richness and abundance of seven Plagiometriona species on their host plants were studied along a single trail in the mountainous Serra dos Órgãos National Park in the State of Rio de Janeiro, Brazil. Six sites were chosen along an altitudinal gradient ranging from 1300 m to 2050 m, where all Solanaceae host plants were inspected in search of adults every two months from June 2006 to June 2007. Species richness did not vary clearly with altitude, but abundance increased up to 1800 m, where the highest mean host plant density was found, and abruptly decreased at the last elevational site. Most species showed a restricted distribution and just one occurred across the entire gradient. For at least four species, altitudinal distribution seems to be strongly related to host plant availability, while for the others it is difficult to access which factors are decisive, due to their low numbers. Only in October all species were found in the field, although February was the month with the highest total abundance. Over the course of the study, the greatest abundances were recorded from October to February, comprehending the hottest and rainiest months, and the lowest abundances were found from June to August, which include the coldest and driest months. Thus, species seasonal distribution, supported by other studies in the same area, seems to be related to the local climate.

  9. Altitudinal and temporal distribution of Plagiometriona Spaeth, 1899 (Coleoptera, Chrysomelidae, Cassidinae in a tropical forest in southeast Brazil

    Directory of Open Access Journals (Sweden)

    Vivian Flinte

    2011-12-01

    Full Text Available Species richness and abundance of seven Plagiometriona species on their host plants were studied along a single trail in the mountainous Serra dos Órgãos National Park in the State of Rio de Janeiro, Brazil. Six sites were chosen along an altitudinal gradient ranging from 1300 m to 2050 m, where all Solanaceae host plants were inspected in search of adults every two months from June 2006 to June 2007. Species richness did not vary clearly with altitude, but abundance increased up to 1800 m, where the highest mean host plant density was found, and abruptly decreased at the last elevational site. Most species showed a restricted distribution and just one occurred across the entire gradient. For at least four species, altitudinal distribution seems to be strongly related to host plant availability, while for the others it is difficult to access which factors are decisive, due to their low numbers. Only in October all species were found in the field, although February was the month with the highest total abundance. Over the course of the study, the greatest abundances were recorded from October to February, comprehending the hottest and rainiest months, and the lowest abundances were found from June to August, which include the coldest and driest months. Thus, species seasonal distribution, supported by other studies in the same area, seems to be related to the local climate.

  10. Contrasting growth forecasts across the geographical range of Scots pine due to altitudinal and latitudinal differences in climatic sensitivity.

    Science.gov (United States)

    Matías, Luis; Linares, Juan C; Sánchez-Miranda, Ángela; Jump, Alistair S

    2017-10-01

    Ongoing changes in global climate are altering ecological conditions for many species. The consequences of such changes are typically most evident at the edge of a species' geographical distribution, where differences in growth or population dynamics may result in range expansions or contractions. Understanding population responses to different climatic drivers along wide latitudinal and altitudinal gradients is necessary in order to gain a better understanding of plant responses to ongoing increases in global temperature and drought severity. We selected Scots pine (Pinus sylvestris L.) as a model species to explore growth responses to climatic variability (seasonal temperature and precipitation) over the last century through dendrochronological methods. We developed linear models based on age, climate and previous growth to forecast growth trends up to year 2100 using climatic predictions. Populations were located at the treeline across a latitudinal gradient covering the northern, central and southernmost populations and across an altitudinal gradient at the southern edge of the distribution (treeline, medium and lower elevations). Radial growth was maximal at medium altitude and treeline of the southernmost populations. Temperature was the main factor controlling growth variability along the gradients, although the timing and strength of climatic variables affecting growth shifted with latitude and altitude. Predictive models forecast a general increase in Scots pine growth at treeline across the latitudinal distribution, with southern populations increasing growth up to year 2050, when it stabilizes. The highest responsiveness appeared at central latitude, and moderate growth increase is projected at the northern limit. Contrastingly, the model forecasted growth declines at lowland-southern populations, suggesting an upslope range displacement over the coming decades. Our results give insight into the geographical responses of tree species to climate change

  11. Altitudinal patterns of diversity and functional traits of metabolically active microorganisms in stream biofilms

    Science.gov (United States)

    Wilhelm, Linda; Besemer, Katharina; Fragner, Lena; Peter, Hannes; Weckwerth, Wolfram; Battin, Tom J

    2015-01-01

    Resources structure ecological communities and potentially link biodiversity to energy flow. It is commonly believed that functional traits (generalists versus specialists) involved in the exploitation of resources depend on resource availability and environmental fluctuations. The longitudinal nature of stream ecosystems provides changing resources to stream biota with yet unknown effects on microbial functional traits and community structure. We investigated the impact of autochthonous (algal extract) and allochthonous (spruce extract) resources, as they change along alpine streams from above to below the treeline, on microbial diversity, community composition and functions of benthic biofilms. Combining bromodeoxyuridine labelling and 454 pyrosequencing, we showed that diversity was lower upstream than downstream of the treeline and that community composition changed along the altitudinal gradient. We also found that, especially for allochthonous resources, specialisation by biofilm bacteria increased along that same gradient. Our results suggest that in streams below the treeline biofilm diversity, specialisation and functioning are associated with increasing niche differentiation as potentially modulated by divers allochthonous and autochthonous constituents contributing to resources. These findings expand our current understanding on biofilm structure and function in alpine streams. PMID:25978543

  12. The genus morpho in colombia: I. species present in colombia, and their geographic and altitudinal distribution El genero Morpho en Colombia: I. especies presentes en Colombia, distribución geográfica y altitudinal

    Directory of Open Access Journals (Sweden)

    Rodríguez Claudia

    1994-06-01

    Full Text Available This work puts together the results of six studies carried out in Colombia on the genus Morpho, with a revised description of. the species found in Colombia based on color patterns and mal e
    genitalia. Biological and ecological data are included, such as geographic and altitudinal distribution, habitat, habits and behavior, and annotated comments on each of the 24 species.
    The work features drawings of genitalia for each species, some of which had not been published before. This first issue covers the distribution of species found in Colombia.En este trabajo, se presentan los resultados de los estudios sobre el género Morphoen Colombia recopilados (6, con una redescripción de las especies del género que habitan en Colombia, con base en las características de patrones de
    coloración y genitalias. Simultáneamente, se incluyen datos biológicos y ecológicos, como: distribución geográfica y altitudinal, hábitos, hábitat y comportamiento, además de otras anotaciones y comentarios de cada una de las 24 especies; se adicionan gráficos simplificados de las genitalias de cada una de las especies, muchas de las cuales no habían sido ilustradas anteriormente y, finalmente, se incluyen los registros de diferentes colecciones. En esta primera entrega, se señala la distribución geográfica y altitudinal de las especies que habitan en Colombia.

  13. Análisis del gradiente edáfico en la región Andinopatagónica Analysis of soil gradient in Andean Patagonia Region

    Directory of Open Access Journals (Sweden)

    Juan José Gaitán

    2007-07-01

    Full Text Available Se analizaron las relaciones entre la ubicación geográfica, precipitación media anual y nueve variables edáficas de 95 perfiles de suelos de origen volcánico distribuidos a lo largo de la región Andina de las provincias de Neuquén, Río Negro y Chubut. Con las variables edáficas correspondientes a dos profundidades (0-20 cm y 30-60 cm se realizó un análisis de cluster que permitió agrupar a los perfiles en cinco grupos principales. Se realizó un análisis de componentes principales y se observó que los grupos se diferenciaron a lo largo del eje 1. Este eje se relaciona con la longitud. Desde los suelos de régimen xérico de estepa ubicados en el este de la región hacia los suelos de régimen údico de bosque ubicados en el oeste, se incrementa el pH (NaF, la concentración de carbono orgánico y la capacidad de retención hídrica y disminuye, el pH (H2O, el pH (KCl y la densidad aparente.The relationships among location, mean annual precipitation and nine edaphic variables were studied for 95 profiles of volcanic soils throughout the Andean Region of the provinces of Neuquen, Rio Negro and Chubut. A cluster analysis conducted with the edaphic variables at two depths (0-20 cm and 30-60 cm indicated five main groups. Principal component analysis (PCA allowed to differentiate the groups for the axis 1. This axis was positively related to longitude, indicating an increase of pH (NaF, organic C and water retention capacity, and a decrease of pH (H2O, pH (KCl and bulk density from the xeric steppe soils at east to the udic forest soils at west.

  14. Estructura del paisaje a lo largo de gradientes urbano-rurales en la cuenca del río Aisén (Región de Aisén, Chile Landscape structure along urban-rural gradients: Aisén river watershed (Aisén region, Chile

    Directory of Open Access Journals (Sweden)

    MARCELA TORRES-GÓMEZ

    2009-03-01

    Full Text Available Los cambios en la estructura del paisaje generalmente están asociados a factores físicos, biológicos y sociales. Sin embargo, su análisis integrado es poco frecuente. El objetivo de este estudio fue determinar los patrones de distribución de los parches de vegetación nativa y del nivel de intervención humana en la cuenca del río Aisén, para establecer si la posición a lo largo de gradientes urbano-rurales tiene alguna relación con estos patrones del paisaje. Para ello se analizaron unidades a lo largo de gradientes en forma multidireccional, considerando como centro urbano la ciudad de Coihaique. Los resultados muestran que no se puede establecer una disposición en gradiente de la cobertura de vegetación nativa desde la zona urbana a la zona rural en los transectos analizados. Sin embargo, hay una correlación negativa entre el nivel de intervención y el área promedio de los parches. Además, se observa que la distribución de los diferentes usos del suelo y las coberturas del paisaje están fuertemente influenciadas por la topografía de las unidades. En base a esto, y considerando que actualmente existe una serie de políticas para el uso y manejo del territorio, no es posible usar el concepto de gradiente urbano-rural como paradigma único para estudiar la estructura del paisaje, como lo han propuesto otros autores.Changes in landscape structure are generally associated to physical, biological and social factors. However, their integrated analysis is rarely done. The objective of this study was to determine the distribution patterns of native vegetation patches and the level of human intervention within the Aisén watershed. The main aim was to establish if the position within urban-rural gradients have some relation with the above patterns. Vegetation units were analyzed in multiple directions considering the city of Coihaique as the main urban center. Results show that the proximity to the city is not correlated with the

  15. Effects of phylogeny, leaf traits, and the altitudinal distribution of host plants on herbivore assemblages on congeneric Acer species.

    Science.gov (United States)

    Nakadai, Ryosuke; Murakami, Masashi; Hirao, Toshihide

    2014-08-01

    Historical, niche-based, and stochastic processes have been proposed as the mechanisms that drive community assembly. In plant-herbivore systems, these processes can correspond to phylogeny, leaf traits, and the distribution of host plants, respectively. Although patterns of herbivore assemblages among plant species have been repeatedly examined, the effects of these factors among co-occurring congeneric host plant species have rarely been studied. Our aim was to reveal the process of community assembly for herbivores by investigating the effects of phylogeny, leaf traits, and the altitudinal distribution of closely related host plants of the genus Acer. We sampled leaf functional traits for 30 Acer species in Japan. Using a newly constructed phylogeny, we determined that three of the six measured leaf traits (leaf thickness, C/N ratio, and condensed tannin content) showed a phylogenetic signal. In a field study, we sampled herbivore communities on 14 Acer species within an elevation gradient and examined relationships between herbivore assemblages and host plants. We found that herbivore assemblages were significantly correlated with phylogeny, leaf traits, phylogenetic signals, and the altitudinal distribution of host plants. Our results indicate that the interaction between historical and current ecological processes shapes herbivore community assemblages.

  16. Cross-continental comparison of the functional composition and carbon allocation of two altitudinal forest transects in Ecuador and Rwanda.

    Science.gov (United States)

    Verbeeck, Hans; Bauters, Marijn; Bruneel, Stijn; Demol, Miro; Taveirne, Cys; Van Der Heyden, Dries; Kearsley, Elizabeth; Cizungu, Landry; Boeckx, Pascal

    2017-04-01

    Tropical forests are key actors in the global carbon cycle. Predicting future responses of these forests to global change is challenging, but important for global climate models. However, our current understanding of such responses is limited, due to the complexity of forest ecosystems and the slow dynamics that inherently form these systems. Our understanding of ecosystem ecology and functioning could greatly benefit from experimental setups including strong environmental gradients in the tropics, as found on altitudinal transects. We setup two such transects in both South-America and Central Africa, focussing on shifts in carbon allocation, forest structure, nutrient cycling and functional composition. The Ecuadorian transect has 16 plots (40 by 40 m) and ranges from 400 to 3000 m.a.s.l., and the Rwandan transect has 20 plots (40 by 40 m) from 1500 to 3000 m.a.s.l. All plots were inventoried and canopy, litter and soil were extensively sampled. By a cross-continental comparison of both transects, we will gain insight in how different or alike both tropical forests biomes are in their responses, and how universal the observed altitudinal adaption mechanisms are. This could provide us with vital information of the ecological responses of both biomes to future global change scenarios. Additionally, comparison of nutrient shifts and trait-based functional composition allows us to compare the biogeochemical cycles of African and South-American tropical forests.

  17. Altitudinal patterns in breeding bird species richness and density in relation to climate, habitat heterogeneity, and migration influence in a temperate montane forest (South Korea).

    Science.gov (United States)

    Kim, Jin-Yong; Lee, Sanghun; Shin, Man-Seok; Lee, Chang-Hoon; Seo, Changwan; Eo, Soo Hyung

    2018-01-01

    Altitudinal patterns in the population ecology of mountain bird species are useful for predicting species occurrence and behavior. Numerous hypotheses about the complex interactions among environmental factors have been proposed; however, these still remain controversial. This study aimed to identify the altitudinal patterns in breeding bird species richness or density and to test the hypotheses that climate, habitat heterogeneity (horizontal and vertical), and heterospecific attraction in a temperate forest, South Korea. We conducted a field survey of 142 plots at altitudes between 200 and 1,400 m a.s.l in the breeding season. A total of 2,771 individuals from 53 breeding bird species were recorded. Altitudinal patterns of species richness and density showed a hump-shaped pattern, indicating that the highest richness and density could be observed at moderate altitudes. Models constructed with 13 combinations of six variables demonstrated that species richness was positively correlated with vertical and horizontal habitat heterogeneity. Density was positively correlated with vertical, but not horizontal habitat heterogeneity, and negatively correlated with migratory bird ratio. No significant relationships were found between spring temperature and species richness or density. Therefore, the observed patterns in species richness support the hypothesis that habitat heterogeneity, rather than climate, is the main driver of species richness. Also, neither habitat heterogeneity nor climate hypotheses fully explains the observed patterns in density. However, vertical habitat heterogeneity does likely help explain observed patterns in density. The heterospecific attraction hypothesis did not apply to the distribution of birds along the altitudinal gradient. Appropriate management of vertical habitat heterogeneity, such as vegetation cover, should be maintained for the conservation of bird diversity in this area.

  18. Corridor- and stopover-use of the Hawaiian goose (Branta sandvicensis), an intratropical altitudinal migrant

    Science.gov (United States)

    Leopold, Christina R.; Hess, Steven C.

    2014-01-01

    We outfitted six male Hawaiian geese, or nene (Branta sandvicensis), with 45-g solar-powered satellite transmitters and collected four location coordinates d−1 from 2010 to 2012. We used 6193 coordinates to characterize migration corridors, habitat preferences and temporal patterns of displacement for 16 migration events with Brownian bridge utilization distributions (BBUD). We used 1552 coordinates to characterize stopovers from 37 shorter-distance movement events with 25% BBUDs. Two subpopulations used a well-defined common migration corridor spanning a broad gradient of elevation. Use of native-dominated subalpine shrubland was 2.81 times more likely than the availability of this land-cover type. The nene differed from other tropical and temperate-zone migrant birds in that: (1) migration distance and the number of stopovers were unrelated (Mann–Whitney test W = 241, P movements were not unidirectional suggesting that social interactions may be more important than refuelling en route; but like other species, nene made more direct migrations with fewer stopovers in return to breeding areas (0.58 ± 0.50) than in migration away from breeding areas (1.64 ± 0.48). Our findings, combined with the direction and timing of migration, which is opposite that of most other intratropical migrants, suggest fundamentally different drivers of altitudinal migration.

  19. A reconstruction of Colombian biomes derived from modern pollen data along an altitude gradient.

    NARCIS (Netherlands)

    Marchant, R.A.; Behling, H.; Berrio Mogollon, J.C.; Cleef, A.M.; Duivenvoorden, J.F.; van Geel, B.; van der Hammen, T.; Hooghiemstra, H.; Kuhry, P.; Melief, B.M.; van Reenen, G.B.A.; Wille, M.

    2001-01-01

    Biomes are reconstructed in Colombia from modern (core-top) pollen data derived from twenty-two sites along an altitudinal gradient (2000 to 4100 m) that encompasses the tree line. The 'biomization' methodology is described in a stepwise manner that details the reconstruction of vegetation along an

  20. Anthocyanin Profile in Berries of Wild and Cultivated Vaccinium spp. along Altitudinal Gradients in the Alps

    OpenAIRE

    Zoratti, Laura; Jaakola, Laura; Häggman, Hely; Giongo, Lara

    2015-01-01

    This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Agricultural and Food Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/acs.jafc.5b02833. Vaccinium spp. berries provide some of the best natural sources of anthocyanins. In the wild bilberry (Vaccinium myrtillus L.), a clear increasing trend in anth...

  1. Trade-off among different anti-herbivore defence strategies along an altitudinal gradient

    Czech Academy of Sciences Publication Activity Database

    Dostálek, T.; Rokaya, Maan Bahadur; Maršík, P.; Rezek, J.; Skuhrovec, J.; Pavela, R.; Münzbergová, Z.

    2016-01-01

    Roč. 8, Jul 11 (2016), č. článku plw026. ISSN 2041-2851 Institutional support: RVO:67179843 Keywords : Climate change * Lamiaceae * VOCs * defence strategies * elevation * greenhouse experiment * insect herbivory * plant–animal interactions Subject RIV: EH - Ecology, Behaviour Impact factor: 2.238, year: 2016

  2. Batrachochytrium dendrobatidis not found in rainforest frogs along an altitudinal gradient of Papua New Guinea

    Czech Academy of Sciences Publication Activity Database

    Dahl, C.; Kiatik, I.; Baisen, I.; Bronikowski, E.; Fleischer, R. C.; Rotzel, N. C.; Lock, J.; Novotný, Vojtěch; Narayan, E.; Hero, J.-M.

    2012-01-01

    Roč. 22, č. 3 (2012), s. 183-186 ISSN 0268-0130 Institutional support: RVO:60077344 Keywords : altitude * amphibians * Batrachochytrium dendrobatidis Subject RIV: EH - Ecology, Behaviour Impact factor: 1.081, year: 2012

  3. Structure, composition and regeneration of riparian forest along an altitudinal gradient in northern Iran

    Science.gov (United States)

    Mohammad Naghi Adel; Hassan Pourbabaei; Ali Salehi; Seyed Jalil Alavi; Daniel C. Dey

    2017-01-01

    In order to protect and understand the regeneration of riparian forests, it is important to understand the environmental conditions that lead to their vegetation differentiation. We evaluated the structure, composition, density and regeneration of woody species in forests along the river Safaroud in Ramsar forest in northern Iran in relation to elevation, soil...

  4. Small mammals and l1abitat structure along altitudinal gradients in ...

    African Journals Online (AJOL)

    of species, and population size with habitat structure, with a view to predicting .... clipping the coat to expose the darker undercoat. Aluminium ..... living on green plant material rathe'l' than seed. It appears to ..... quently thermo-regulation.

  5. Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard)

    Czech Academy of Sciences Publication Activity Database

    Kotas, P.; Šantrůčková, H.; Elster, Josef; Kaštovská, E.

    2018-01-01

    Roč. 15, č. 6 (2018), s. 1879-1894 ISSN 1726-4170 R&D Projects: GA MŠk(CZ) LM2015075 Grant - others:GA MŠk LM2010009 Institutional support: RVO:67985939 Keywords : ecosystem * High Arctic * soil microbial biomass Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 3.851, year: 2016

  6. Species richness pattern along altitudinal gradient in Central European beech forests

    Czech Academy of Sciences Publication Activity Database

    Hrivnák, R.; Gömöry, D.; Slezák, M.; Ujházy, K.; Hédl, Radim; Jarčuška, B.; Ujházyová, M.

    2014-01-01

    Roč. 49, č. 3 (2014), s. 425-441 ISSN 1211-9520 Institutional support: RVO:67985939 Keywords : altitude * beech-dominated forest * species richness Subject RIV: EF - Botanics Impact factor: 1.778, year: 2014

  7. Reticulate Pleistocene evolution of Ethiopian rodent genus along remarkable altitudinal gradient

    Czech Academy of Sciences Publication Activity Database

    Bryja, Josef; Kostin, D.; Meheretu, Y.; Šumbera, R.; Bryjová, Anna; Kasso, M.; Mikula, Ondřej; Lavrenchenko, L. A.

    2018-01-01

    Roč. 118, January (2018), s. 75-87 ISSN 1055-7903 Institutional support: RVO:68081766 Keywords : Stenocephalemys * mitochondrial introgression * Ethiopian highlands * Rodentia * ecological speciation * Great Rift Valley Subject RIV: EG - Zoology Impact factor: 4.419, year: 2016

  8. Predator pressure, herbivore abundance and plant damage along a subtropical altitudinal gradient

    Czech Academy of Sciences Publication Activity Database

    Bito, D.; Novotný, Vojtěch; Burwell, C. J.; Nakamura, A.; Kitching, R. L.; Ødegaard, F.

    2011-01-01

    Roč. 55, č. 2 (2011), s. 451-461 ISSN 0079-8835 Institutional research plan: CEZ:AV0Z50070508 Keywords : elevation * Formicidae * Coleoptera Subject RIV: EH - Ecology, Behaviour http://www.qm.qld.gov.au/About+Us/Publications/Memoirs+of+the+ Queensland +Museum/MQM+Vol-55

  9. Trade-off among different anti-herbivore defence strategies along an altitudinal gradient

    Czech Academy of Sciences Publication Activity Database

    Dostálek, Tomáš; Rokaya, Maan Bahadur; Maršík, Petr; Rezek, Jan; Skuhrovec, J.; Pavela, R.; Münzbergová, Zuzana

    2016-01-01

    Roč. 8, Jul 11 (2016), č. článku plw026. ISSN 2041-2851 R&D Projects: GA ČR GP13-10850P Institutional support: RVO:67985939 ; RVO:61389030 Keywords : climate change * plant–animal interactions * defence strategies Subject RIV: EF - Botanics; EF - Botanics (UEB-Q) Impact factor: 2.238, year: 2016

  10. Modelo climático de los páramos de la Cordillera Oriental colombiana aplicado a regímenes de temperatura del suelo

    Directory of Open Access Journals (Sweden)

    Carlos Enrique Castro Méndez

    2016-06-01

    Full Text Available La aplicación (con criterios consistentes de los regímenes de temperatura del suelo, no había sido necesaria y decisiva, hasta ahora, ya que se consideraba suficiente esta información de carácter descriptivo. La temperatura asignada al suelo provenía de la reclasificación directa del clima ambiental al edáfico con valores medios anuales dados a cada franja altitudinal hace más de 200 años, esto no es acorde con los cambios, que desde la geografía biofísica, se han percibido en el ambiente. Se propone un modelo climático, basado en isotermas del suelo, para determinar los regímenes de temperatura a partir de información bajo coberturas vegetales y del suelo, para cada vertiente montañosa en particular. Se encontraron gradientes de temperatura (ºC/100 m de 0,73 y 0,61 en la vertiente occidental y oriental, respectivamente. La temperatura del suelo fue 1.9 ºC mayor que la del aire y se delimitaron los regímenes térmicos del suelo cryico, isofrígido e isomésico.

  11. Altitudinal patterns and controls of trace metal distribution in soils of a remote high mountain, Southwest China.

    Science.gov (United States)

    Li, Rui; Bing, Haijian; Wu, Yanhong; Zhou, Jun; Xiang, Zhongxiang

    2018-02-01

    The aim of this study is to reveal the effects of regional human activity on trace metal accumulation in remote alpine ecosystems under long-distance atmospheric transport. Trace metals (Cd, Pb, and Zn) in soils of the Mt. Luoji, Southwest China, were investigated along a large altitudinal gradient [2200-3850 m above sea level (a.s.l.)] to elaborate the key factors controlling their distribution by Pb isotopic composition and statistical models. The concentrations of Cd, Pb, and Zn in the surface soils (O and A horizons) were relatively low at the altitudes of 3500-3700 m a.s.l. The enrichment factors of trace metals in the surface soils increased with altitude. After normalization for soil organic matter, the concentrations of Cd still increased with altitude, whereas those of Pb and Zn did not show a clear altitudinal trend. The effects of vegetation and cold trapping (CTE) (pollutant enrichment by decreasing temperature with increasing altitude) mainly determined the distribution of Cd and Pb in the O horizon, whereas CTE and bedrock weathering (BW) controlled that of Zn. In the A horizon, the distribution of Cd and Pb depended on the vegetation regulation, whereas that of Zn was mainly related to BW. Human activity, including ores mining and fossil fuels combustion, increased the trace metal deposition in the surface soils. The anthropogenic percentage of Cd, Pb, and Zn quantified 92.4, 67.8, and 42.9% in the O horizon, and 74.5, 33.9, and 24.9% in the A horizon, respectively. The anthropogenic metals deposited at the high altitudes of Mt. Luoji reflected the impact of long-range atmospheric transport on this remote alpine ecosystem from southern and southwestern regions.

  12. Barbel species arrangement in a regional Natura 2000 network (Emilia Romagna, Northern Italy: An altitudinal perspective

    Directory of Open Access Journals (Sweden)

    Federica Piccoli

    2017-07-01

    Full Text Available Southern Europe hosts a large number of critical catchments for freshwater biodiversity, including endemic fish species. Unfortunately, these areas are severely threatened due to direct and indirect anthropogenic effects. In this context, with the aim to improve the effectiveness of threatened fish protection, the Life project BARBIE (LIFE13 NAT/IT/001129 started in 2014 and focused on three congeneric species of the genus Barbus: two of “priority interest” sensu Habitats Directive [Barbus caninus (Bonaparte, 1839, and B. plebejus (Bonaparte, 1839], and one alien [Barbus barbus (Linnaeus, 1758]. Our main objective was to assess the contribution of a complex of protected areas included in the Natura 2000 network – located in the provinces of Parma, Piacenza and Reggio Emilia (Norther Italy – to support the presence of the three barbel species in analysis. Additionally, we explored the role of a set of environmental variables (i.e., physical, chemical, biological, and land-use descriptors to drive the current conditions of the study sites and the responses of Barbus species. As a general rule, the present study confirmed a clear decline of the local native barbel populations, and confirmed the existence of a zonation pattern of the barbel taxa. Hence, we observed a strong altitude segregation between native vs. alien species, with the exotic B. barbus currently limited to plain and only sporadically present in the Apennine areas as genetic introgression. These evidences mirrored the altitudinal gradients of anthropogenic disturbance. The main causes were the progressive disappearance of well-structured riparian stripes, and the intense land use change, ranging from semi-natural patches (mountain and hill sectors to land clearing for intensive agriculture (lowland sectors. This highlights the need to take into account the spatial dynamics of alien invasive species in programming recovery actions that could have unexpected impacts to the

  13. Biodiversidad de la flora del flanco oriental del Cordón del Plata (Luján de Cuyo, Mendoza, Argentina. Catálogo florístico Biodiversity of the flora of the eastern slope of the Cordón del Plata (Luján de Cuyo, Mendoza, Argentina

    Directory of Open Access Journals (Sweden)

    Eduardo Méndez

    2009-07-01

    Full Text Available La biodiversidad de la flora de la vertiente oriental del Cordón del Plata, Luján de Cuyo, Mendoza, Argentina se analizó a lo largo de un gradiente altitudinal, entre los 1200 y 4500 m s.n.m. Para ello se utilizó la lista florística de las especies de 89 comunidades vegetales distribuidas en 14 unidades de vegetación, 5 pisos de vegetación y 3 unidades fitogeográficas. Para cada especie se consideró su distribución en los grupos de comunidades vegetales, ubicación fitogeográfica, formas de vida, origen y registro de colección. La flora examinada contiene 667 especies vegetales que se corresponden con 338 géneros y 82 familias. Las familias están representadas por 8 Pteridophyta, 1 Gymnospermae y 73 Angiospermae, con 12 Monocotyledoneae y 61 Dicotyledoneae. Las familias mejor representadas son Asteraceae y Poaceae que tienen en conjunto 110 géneros y 249 especies. Los géneros Senecio, Baccharis y Adesmia son los más ricos en especies. Aproximadamente el 20 % de las especies son endémicas de Argentina. La flora del área se la compara con la del país, la provincia y la de otras áreas.Floristic catalogue. The floristic biodiversity of the eastern slope of the Cordón del Plata, Luján de Cuyo, Mendoza, Argentina, was studied along an altitudinal gradient, between 1200 and 4500 m a.s.l. For this we used a floristic list of 89 plant communities, distributed in 14 vegetation types, 5 vegetation belts and 3 phytogeographic units. For each of the species, its distribution in the groups of plant communities, phytogeographic position, life form, biogeographical origin, and registration of each collection was considered. The studied flora has 667 species, corresponding to 338 genera and 82 families. There are 8 Pteridophyta, 1 Gymnospermae, and 73 Angiospermae, of which 12 are Monocotyledons and 61 Dicotyledons. The most represented families are Asteraceae and Poaceae, which in total have 110 genera and 249 species. The most species

  14. DESLIZAMIENTOS NATURALES Y COMUNIDADES PIONERA DE ECOSISTEMAS MONTANOS AL OCCIDENTE DEL PARQUE NACIONAL PODOCARPUS (ECUADOR

    Directory of Open Access Journals (Sweden)

    LOZANO PABLO

    2008-07-01

    Full Text Available El Parque Nacional Podocarpus (PNP, ubicado al sur del Ecuador, ocupa una posición climatológica clave con respecto a la deflexión de Huancabamba aledaña a esta área hacia el sur, que ocasiona una barrera natural de distribución de especies y por otro lado este aislamiento biogeográfíco ha originado especiación florística en algunas especies. La geografía accidentada de esta región, sumada a la escasa capa vegetal y precipitaciones que superan los 6000 mm en los páramos, ocasiona impactos severos en los flancos orientales y occidentales de la baja Cordillera Oriental que no sobrepasa los 3700 m, en sus límites altitudinales más altos. Es aquí donde existe una dinámica alta de deslizamientos, los mismos que si bien afectan la diversidad vegetal, también son considerados un motor generador de continuos procesos de regeneración. Se establecieron 138 parcelas, distribuidas a o largo de un gradiente latitudinal y altitudinal, de 1 x 5m al occidente del PNP, encontrándose 218 especies representantes de 180 géneros y 51 familias; el piso altitudinal de mayor diversidad está a los 2700 m. El análisis TWINSPAN separó nueve comunidades vegetales, mientras que el análisis multivariado CANOCO, determinó que las características edafológicas influyen en la composición de la vegetación, mientras que la altitud y la pendiente no establecen notable diferencia.

  15. Forest filter effect versus cold trapping effect on the altitudinal distribution of PCBs: a case study of Mt. Gongga, eastern Tibetan Plateau.

    Science.gov (United States)

    Liu, Xin; Li, Jun; Zheng, Qian; Bing, Haijian; Zhang, Ruijie; Wang, Yan; Luo, Chunling; Liu, Xiang; Wu, Yanhong; Pan, Suhong; Zhang, Gan

    2014-12-16

    Mountains are observed to preferentially accumulate persistent organic pollutants (POPs) at higher altitude due to the cold condensation effect. Forest soils characterized by high organic carbon are important for terrestrial storage of POPs. To investigate the dominant factor controlling the altitudinal distribution of POPs in mountainous areas, we measured concentrations of polychlorinated biphenyls (PCBs) in different environmental matrices (soil, moss, and air) from nine elevations on the eastern slope of Mt. Gongga, the highest mountain in Sichuan Province on the Tibetan Plateau. The concentrations of 24 measured PCBs ranged from 41 to 510 pg/g dry weight (dw) (mean: 260 pg/g dw) in the O-horizon soil, 280 to 1200 pg/g dw (mean: 740 pg/g dw) in moss, and 33 to 60 pg/m(3) (mean: 47 pg/m(3)) in air. Soil organic carbon was a key determinant explaining 75% of the variation in concentration along the altitudinal gradient. Across all of the sampling sites, the average contribution of the forest filter effect (FFE) was greater than that of the mountain cold trapping effect based on principal components analysis and multiple linear regression. Our results deviate from the thermodynamic theory involving cold condensation at high altitudes of mountain areas and highlight the importance of the FFE.

  16. Latitudinal and altitudinal controls of Titan's dune field morphometry

    Science.gov (United States)

    Le Gall, A.; Hayes, A. G.; Ewing, R.; Janssen, M. A.; Radebaugh, J.; Savage, C.; Encrenaz, P.; the Cassini Radar Team

    2012-01-01

    Dune fields dominate ˜13% of Titan's surface and represent an important sink of carbon in the methane cycle. Herein, we discuss correlations in dune morphometry with altitude and latitude. These correlations, which have important implications in terms of geological processes and climate on Titan, are investigated through the microwave electromagnetic signatures of dune fields using Cassini radar and radiometry observations. The backscatter and emissivity from Titan's dune terrains are primarily controlled by the amount of interdune area within the radar footprint and are also expected to vary with the degree of the interdunal sand cover. Using SAR-derived topography, we find that Titan's main dune fields (Shangri-La, Fensal, Belet and Aztlan) tend to occupy the lowest elevation areas in Equatorial regions occurring at mean elevations between ˜-400 and ˜0 m (relative to the geoid). In elevated dune terrains, we show a definite trend towards a smaller dune to interdune ratio and possibly a thinner sand cover in the interdune areas. A similar correlation is observed with latitude, suggesting that the quantity of windblown sand in the dune fields tends to decrease as one moves farther north. The altitudinal trend among Titan's sand seas is consistent with the idea that sediment source zones most probably occur in lowlands, which would reduce the sand supply toward elevated regions. The latitudinal preference could result from a gradual increase in dampness with latitude due to the asymmetric seasonal forcing associated with Titan's current orbital configuration unless it is indicative of a latitudinal preference in the sand source distribution or wind transport capacity.

  17. Do American dippers obtain a survival benefit from altitudinal migration?

    Directory of Open Access Journals (Sweden)

    David J Green

    Full Text Available Studies of partial migrants provide an opportunity to assess the cost and benefits of migration. Previous work has demonstrated that sedentary American dippers (residents have higher annual productivity than altitudinal migrants that move to higher elevations to breed. Here we use a ten-year (30 period mark-recapture dataset to evaluate whether migrants offset their lower productivity with higher survival during the migration-breeding period when they occupy different habitat, or early and late-winter periods when they coexist with residents. Mark-recapture models provide no evidence that apparent monthly survival of migrants is higher than that of residents at any time of the year. The best-supported model suggests that monthly survival is higher in the migration-breeding period than winter periods. Another well-supported model suggested that residency conferred a survival benefit, and annual apparent survival (calculated from model weighted monthly apparent survival estimates using the Delta method of residents (0.511 ± 0.038SE was slightly higher than that of migrants (0.487 ± 0.032. Winter survival of American dippers was influenced by environmental conditions; monthly apparent survival increased as maximum daily flow rates increased and declined as winter temperatures became colder. However, we found no evidence that environmental conditions altered differences in winter survival of residents and migrants. Since migratory American dippers have lower productivity and slightly lower survival than residents our data suggests that partial migration is likely an outcome of competition for limited nest sites at low elevations, with less competitive individuals being forced to migrate to higher elevations in order to breed.

  18. Do American dippers obtain a survival benefit from altitudinal migration?

    Science.gov (United States)

    Green, David J; Whitehorne, Ivy B J; Middleton, Holly A; Morrissey, Christy A

    2015-01-01

    Studies of partial migrants provide an opportunity to assess the cost and benefits of migration. Previous work has demonstrated that sedentary American dippers (residents) have higher annual productivity than altitudinal migrants that move to higher elevations to breed. Here we use a ten-year (30 period) mark-recapture dataset to evaluate whether migrants offset their lower productivity with higher survival during the migration-breeding period when they occupy different habitat, or early and late-winter periods when they coexist with residents. Mark-recapture models provide no evidence that apparent monthly survival of migrants is higher than that of residents at any time of the year. The best-supported model suggests that monthly survival is higher in the migration-breeding period than winter periods. Another well-supported model suggested that residency conferred a survival benefit, and annual apparent survival (calculated from model weighted monthly apparent survival estimates using the Delta method) of residents (0.511 ± 0.038SE) was slightly higher than that of migrants (0.487 ± 0.032). Winter survival of American dippers was influenced by environmental conditions; monthly apparent survival increased as maximum daily flow rates increased and declined as winter temperatures became colder. However, we found no evidence that environmental conditions altered differences in winter survival of residents and migrants. Since migratory American dippers have lower productivity and slightly lower survival than residents our data suggests that partial migration is likely an outcome of competition for limited nest sites at low elevations, with less competitive individuals being forced to migrate to higher elevations in order to breed.

  19. Bilateral occipital lobe infarction with altitudinal field loss following radiofrequency cardiac catheter ablation

    Directory of Open Access Journals (Sweden)

    Chen Celia S

    2010-03-01

    Full Text Available Abstract Background Bilateral stroke following radiofrequency catheter ablation is an unusual complication and may result in bilateral altitudinal visual field defects. Bilateral altitudinal visual field defects usually result from prechiasmal pathology causing damage to both retinas or optic nerves and rarely from bilateral symmetric damage to the post chiasmal visual pathways. Case presentation A 48-year-old man complained of visual disturbance on wakening following radiofrequency catheter ablation. The patient had a CHADS score of 1 pre-operatively and no complications were noted intra-operatively. Examination revealed a bilateral superior altitudinal defect and MRI of the brain showed multifocal areas of infarction predominantly involving the occipital lobes which correlated to with the visual deficits. Conclusion While the risk of thromboembolism and perioperative stroke during radiofrequency catheter ablation is small, it is not insignificant.

  20. Composición florística de la cuenca del río Ilo-Moquegua y Lomas de Ilo, Moquegua, Perú

    Directory of Open Access Journals (Sweden)

    Mónica Arakaki

    2013-06-01

    Full Text Available Se presenta un estudio de la composición y riqueza de la flora vascular en la cuenca del Río Ilo- Moquegua y las Lomas de Ilo, a lo largo de una gradiente altitudinal que va desde los 0 hasta 4600 m, basado en colectas intensivas, revisión de ejemplares de herbario y consulta bibliográfica. De acuerdo al presente estudio, la flora vascular de la cuenca del río Ilo-Moquegua y las Lomas de Ilo está integrada por 63 familias, 233 géneros y 394 especies. Las Magnoliopsida representan el 83% de las especies y las Liliopsida el 15%. Las familias con mayor número de géneros y especies son Asteraceae (41 géneros y 60 especies, Poaceae (28 y 44, Solanaceae (11 y 32, Fabaceae (17 y 26, Malvaceae (11 y 21, Brassicaceae (10 y 15, Boraginaceae (9 y 15 y Cactaceae (10 y 14. Las formas biológicas dominantes son las hierbas (72%, seguidas por los arbustos (21%, plantas que pueden ser hierbas o arbustos (5%, árboles (2% y plantas parásitas (menos del 1%. De las 55 especies endémicas del Perú reportadas en el presente estudio, 10 están restringidas al departamento de Moquegua. Se presenta un total de 176 nuevas adiciones a la flora del departamento.

  1. SPATIAL PATTERNS OF DISTRIBUTION OF TREE SPECIES IN HIGH MOUNTAIN FORESTS AT THE REGION OF ANTIOQUIA, COLOMBIA PATRONES DE DISTRIBUCIÓN ESPACIAL DE ESPECIES ARBÓREAS EN BOSQUES DE ALTA MONTAÑA DEL DEPARTAMENTO DE ANTIOQUIA, COLOMBIA

    Directory of Open Access Journals (Sweden)

    Ronald Alfonso Montañez Valencia

    2010-12-01

    Full Text Available The assessed the patterns of spatial distribution of tree species along an altitudinal gradient in high mountain forests it was evaluated. The study was carried out in three 1-ha plots located in high Andean forests on the northern part of the Central cordillera of Colombia, classifying the data into two categories of size: canopy (DBH>10 cm and understory (DBHSe evaluó el patrón de distribución espacial de especies arbóreas a lo largo de un gradiente altitudinal en bosques de alta montaña. El estudio se realizó en tres (3 parcelas permanentes de 1 ha ubicadas en bosques alto andinos al norte de la cordillera Central de Colombia, clasificando los datos en dos estratos arbóreos: dosel (DAP≥10cm y sotobosque (DAP<10cm. El objeto es responder si: 1. ¿Son similares los patrones de distribución entre dosel y sotobosque? 2. ¿Existen diferencias en el patrón de distribución a lo largo del gradiente altitudinal? Para definir el patrón de distribución de las especies a diferentes escalas se empleó el índice estandarizado de Morisita (Ip. El patrón de distribución predominante fue el gregario para especies de dosel y sotobosque en las tres áreas de estudio. El grado de agrupamiento de las especies de dosel aumentó a medida que incrementó la escala o el tamaño de la parcela. En contraste, en el sotobosque el gregarismo disminuyó con la escala espacial de análisis. Lo anterior sugiere que la denso-dependencia aumenta proporcionalmente con la altitud. Esta tendencia, no obstante, parece estar controlada por mecanismos reguladores contrastantes, tales como la limitación en dispersión y la especialización de hábitat, entre especies del dosel y el sotobosque respectivamente.

  2. Cultivable bacterial diversity along the altitudinal zonation and vegetation range of tropical Eastern Himalaya

    Directory of Open Access Journals (Sweden)

    Nathaniel A. Lyngwi

    2013-03-01

    Full Text Available The Northeastern part of India sprawls over an area of 262 379km² in the Eastern Himalayan range. This constitutes a biodiversity hotspot with high levels of biodiversity and endemism; unfortunately, is also a poorly known area, especially on its microbial diversity. In this study, we assessed cultivable soil bacterial diversity and distribution from lowlands to highlands (34 to 3 990m.a.s.l.. Soil physico-chemical parameters and forest types across the different altitudes were characterized and correlated with bacterial distribution and diversity. Microbes from the soil samples were grown in Nutrient, Muller Hinton and Luria-Bertani agar plates and were initially characterized using biochemical methods. Parameters like dehydrogenase and urease activities, temperature, moisture content, pH, carbon content, bulk density of the sampled soil were measured for each site. Representative isolates were also subjected to 16S rDNA sequence analysis. A total of 155 cultivable bacterial isolates were characterized which were analyzed for richness, evenness and diversity indices. The tropical and sub-tropical forests supported higher bacterial diversity compared to temperate pine, temperate conifer, and sub-alpine rhododendron forests. The 16S rRNA phylogenetic analysis revealed that Firmicutes was the most common group followed by Proteobacteria and Bacteroidetes. Species belonging to the genera Bacillus and Pseudomonas were the most abundant. Bacterial CFU showed positive but insignificant correlation with soil parameters like pH (r=0.208, soil temperature (r=0.303, ambient temperature (r=0.443, soil carbon content (r=0.525, soil bulk density (r=0.268, soil urease (r=0.549 and soil dehydrogenase (r=0.492. Altitude (r=0.561 and soil moisture content (r=-0.051 showed negative correlation. Altitudinal gradient along with the vegetation and soil physico-chemical parameters were found to influence bacterial diversity and distribution. This study points out

  3. Evaluation of the impact of frost resistances on potential altitudinal limit of trees.

    Science.gov (United States)

    Charrier, Guillaume; Cochard, Hervé; Améglio, Thierry

    2013-09-01

    Winter physiology of woody plants is a key issue in temperate biomes. Here, we investigated different frost resistance mechanisms on 1-year-old branches of 11 European tree species from November until budburst: (i) frost hardiness of living cells (by electrolyte leakage method), (ii) winter embolism sensitivity (by percentage loss of conductivity: PLC) and (iii) phenological variation of budburst (by thermal time to budburst). These ecophysiological traits were analyzed according to the potential altitudinal limit, which is highly related to frost exposure. Seasonal frost hardiness and PLC changes are relatively different across species. Maximal PLC observed in winter (PLCMax) was the factor most closely related to potential altitudinal limit. Moreover, PLCMax was related to the mean hydraulic diameter of vessels (indicating embolism sensitivity) and to osmotic compounds (indicating ability of living cells to refill xylem conducting elements). Winter embolism formation seems to be counterbalanced by active refilling from living cells. These results enabled us to model potential altitudinal limit according to three of the physiological/anatomical parameters studied. Monitoring different frost resistance strategies brings new insights to our understanding of the altitudinal limits of trees.

  4. Altitudinal and seasonal differences of tick communities in dogs from pastoralist tribes of Northern Kenya

    Czech Academy of Sciences Publication Activity Database

    D'Amico, G.; Dumitrache, M.O.; Široký, P.; Albrechtová, K.; Sloboda, M.; Domsa, C.; Sándor, A.D.; Balázsi, R.; Kanyari, P. W. N.; Modrý, David; Mihalca, A. D.

    2015-01-01

    Roč. 212, 3-4 (2015), s. 318-323 ISSN 0304-4017 Institutional support: RVO:60077344 Keywords : Altitudinal distribution * Rhipicephalus sanguineus * Rhipicephalus pulchellus * Rhipicephalus armatus Subject RIV: GJ - Animal Vermins ; Diseases, Veterinary Medicine Impact factor: 2.242, year: 2015

  5. Growth trends and climate responses of Norway spruce along elevational gradients in East-Central Europe

    Czech Academy of Sciences Publication Activity Database

    Ponočná, T.; Spyt, B.; Kaczka, R. J.; Büntgen, Ulf; Treml, V.

    2016-01-01

    Roč. 30, č. 5 (2016), s. 1633-1646 ISSN 0931-1890 R&D Projects: GA MŠk(CZ) EE2.3.20.0248 Institutional support: RVO:67179843 Keywords : abies l. karst. * tree-ring chronologies * basal area increment * radial growth * forest growth * altitudinal gradient * sudetes mountains * northern europe * tatra mountains * alps * climate change * mountain forests * picea abies * radial growth * rree rings * trend preservation Subject RIV: GK - Forestry Impact factor: 1.842, year: 2016

  6. Body Size Adaptations to Altitudinal Climatic Variation in Neotropical Grasshoppers of the Genus Sphenarium (Orthoptera: Pyrgomorphidae)

    Science.gov (United States)

    2015-01-01

    Altitudinal clines in body size can result from the effects of natural and sexual selection on growth rates and developing times in seasonal environments. Short growing and reproductive seasons constrain the body size that adults can attain and their reproductive success. Little is known about the effects of altitudinal climatic variation on the diversification of Neotropical insects. In central Mexico, in addition to altitude, highly heterogeneous topography generates diverse climates that can occur even at the same latitude. Altitudinal variation and heterogeneous topography open an opportunity to test the relative impact of climatic variation on body size adaptations. In this study, we investigated the relationship between altitudinal climatic variation and body size, and the divergence rates of sexual size dimorphism (SSD) in Neotropical grasshoppers of the genus Sphenarium using a phylogenetic comparative approach. In order to distinguish the relative impact of natural and sexual selection on the diversification of the group, we also tracked the altitudinal distribution of the species and trends of both body size and SSD on the phylogeny of Sphenarium. The correlative evidence suggests no relationship between altitude and body size. However, larger species were associated with places having a warmer winter season in which the temporal window for development and reproduction can be longer. Nonetheless, the largest species were also associated with highly seasonal environments. Moreover, large body size and high levels of SSD have evolved independently several times throughout the history of the group and male body size has experienced a greater evolutionary divergence than females. These lines of evidence suggest that natural selection, associated with seasonality and sexual selection, on maturation time and body size could have enhanced the diversification of this insect group. PMID:26684616

  7. Effect of water stress in soil-water-vegetation relationships, along a rainfall gradient in southern Spain; Incidencia del stress hidrico en las relaciones suelo-agua-planta a lo largo de un gradiente pluviometrico en el sur de Espana

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Sinoga, J. D.; Ferre Bueno, E.; Martinez-Murillo, J. F.; Gabarron-Galeote, M. A.

    2009-07-01

    The Andalusian Mediterranean Watershed, in the South of the Iberian Peninsula, shows a climatic gradient from the Straits of Gibraltar (1,600 mm year{sup -1}) to the Cabo de Gata (150 mm year{sup -1}). Climate conditions differences are translating into variations in the elements of the eco-geomorphologic system at hillslope scale. In this study has been analysed the immediate consequences of a period of two years drought (2004-06) on several elements of the Mediterranean eco-geomorphologic system at three hillslopes (sub-humid, dry Mediterranean and semi-arid). the soil water content, the pattern of vegetation and some soil properties (organic matter content, aggregate stability and permeability) were analysed before (Nov-2003) and during (Nov-2005) the drought period. Final results have shown: i) reduction in soil water content which reached in the wet seasons values below wilting point, affecting negatively to the water available for vegetation and especially in the wettest sites; ii) reduction in vegetation cover and in the number of plants, especially at semi-arid field site; iii) changes in the organic matter content which aggravates the loss of stability of soil aggregates, a process seen more clearly under more arid conditions; and iv) reduction of soil permeability in all situations in the climate gradient studied, which supposes a priori an increase in erosive processes due to surface runoff. These results indicate increased vulnerability of the eco-geomorphologic system because of the rainfall drought situation. (Author) 14 refs.

  8. Altitudinal divergence in maternal thermoregulatory behaviour may be driven by differences in selection on offspring survival in a viviparous lizard

    NARCIS (Netherlands)

    Uller, Tobias; While, Geoffrey M.; Cadby, Chloe D.; Harts, Anna; O'Connor, Katherine; Pen, Ido; Wapstra, Erik

    Plastic responses to temperature during embryonic development are common in ectotherms, but their evolutionary relevance is poorly understood. Using a combination of field and laboratory approaches, we demonstrate altitudinal divergence in the strength of effects of maternal thermal opportunity on

  9. Abiotic gradients drive floristic composition and structure of plant communities in the Monte Desert Gradientes abióticos dirigen la composición florística y la estructura de las comunidades de plantas en el Desierto del Monte

    Directory of Open Access Journals (Sweden)

    PABLO ACEBES

    2010-01-01

    Full Text Available Defining plant communities in desert zones is difficult due to large scale homogeneity and small scale heterogeneity, thus making provision of systematic information for conservation decisions problematic. We analysed plant communities of the most arid sector of Monte Desert for structure, plant composition and environmental variables. Small-scale variables such as slope, rock cover, bare ground and litter, as well as large-scale ones such as species diversity, composition and similarity within and between sites were included. Analyses of floristic composition showed the difficulty of segregating distinct communities due to high internal heterogeneity and overlap between the different sites. Only mesquite woodlands, a community situated at the extreme of the soil moisture-gradient was segregated. Ordination on structural variables was somewhat more successful in segregating communities on the basis of substrate type and of tree and shrub cover. Our results showed the difficulty distinguishing plant communities in temperate deserts, suggesting the existence of relatively stable assemblages of species at the extremes of the gradients and of great heterogeneity within and between sites. They cannot be defined by floristic variables solely, but require environmental information also.La definición de comunidades discretas de plantas en zonas desérticas es complejo debido tanto a su homogeneidad a gran escala como a su heterogeneidad a pequeña escala, lo que acaba generando dificultades para la toma de decisiones de conservación. En este trabajo analizamos las comunidades de plantas del sector más árido del Desierto del Monte en función de su estructura y composición florística. Se han utilizado también variables ambientales estimadas a pequeña escala como la pendiente o la superficie de roca, suelo desnudo y hojarasca, así como variables que operan a mayor escala como la diversidad de especies, la composición florística y la similitud

  10. Integrating the EMPD with an Alpine altitudinal training set to reconstruct climate variables in Holocene pollen records from high-altitude peat bogs

    Science.gov (United States)

    Furlanetto, Giulia; Badino, Federica; Brunetti, Michele; Champvillair, Elena; De Amicis, Mattia; Maggi, Valter; Pini, Roberta; Ravazzi, Cesare; Vallé, Francesca

    2016-04-01

    Temperatures and precipitation are the main environmental factors influencing vegetation and pollen production. Knowing the modern climate optima and tolerances of those plants represented in fossil assemblages and assuming that the relationships between plants and climate in the past are not dissimilar from the modern ones, fossil pollen records offer many descriptors to reconstruct past climate variables. The aim of our work is to investigate the potential of high-altitude pollen records from an Alpine peat bog (TBValter, close to the Ruitor Glacier, Western Italian Alps) for quantitative paleoclimate estimates. The idea behind is that high-altitude ecosystems are more sensitive to climate changes, especially to changes in July temperatures that severely affect the timberline ecotone. Meantime, we met with difficulties when considering the factors involved in pollen dispersal over a complex altitudinal mountain pattern, such as the Alps. We used the EMPD-European Modern Pollen Database (Davis et al., 2013) as modern training set to be compared with our high-altitude fossil site. The EMPD dataset is valuable in that it provides a large geographic coverage of main ecological and climate gradients (at sub-continental scale) but lacks in sampling of altitudinal gradients and high-altitude sites in the Alps. We therefore designed an independent altitudinal training set for the alpine valley hosting our fossil site. 27 sampling plots were selected along a 1700m-elevational transect. In a first step, each plot was provided with (i) 3 moss polsters collected following the guidelines provided by Cañellas-Boltà et al. (2009) and analyzed separately to account for differences in pollen deposition at small scale, (ii) morphometrical parameters obtained through a high-resolution DEM, and (iii) temperature and precipitation were estimated by means of weighted linear regression of the meteorological variable versus elevation, locally evaluated for each site (Brunetti et al

  11. Estudio coste-efectividad sobre la medición del gradiente de presión venosa hepática en la profilaxis secundaria de la hemorragia digestiva varicosa A cost-effectiveness study of hepatic venous pressure gradient measurement in the secondary prevention of variceal bleeding

    Directory of Open Access Journals (Sweden)

    A. Amorós

    2008-07-01

    Full Text Available Objetivo: la hemorragia digestiva es una complicación frecuente en pacientes con cirrosis hepática. La tasa de recidiva tras un primer episodio oscila en torno al 60%, motivo por el cual la profilaxis está recomendada. Esta puede realizarse mediante fármacos (betabloqueantes y nitratos combinados o no con ligadura endoscópica con bandas. El objetivo de este estudio es valorar el coste-efectividad de la medición del gradiente de presión venosa hepática (GPVH previo a la elección de la profilaxis secundaria. Métodos: creamos un árbol de decisión para calcular el coste-efectividad de dos estrategias: grupo 1: pacientes a los que se les determinó el GPVH; cuando tras la administración de propranolol hubo una disminución del gradiente ≥ al 20% respecto al inicial o disminuyó por debajo de 12 mmHg, los pacientes fueron tratados con propranolol. Si no hubo tal variación del GPVH, se realizó ligadura endoscópica de las varices. Grupo 2: en este grupo no se monitorizó el GPVH. Los pacientes con varices grado I recibieron tratamiento con betabloqueantes más nitratos y los que presentaban varices grandes (II, III, IV fueron tratados con betabloqueantes y LEB. Resultados: en el grupo del estudio hemodinámico respondió un 36%, estos recibieron tratamiento betabloqueante, la tasa de resangrado fue del 0%. En los no respondedores la tasa de resangrado fue de un 17%. En el grupo sin estudio se trató con propranolol más nitratos al 28,42% y resangraron un 25%; la tasa de resangrado en el grupo que recibió tratamiento con betabloqueantes más ligadura endoscópica fue de un 13%. El coste total en el grupo al que se realizó el estudio hemodinámico fue de 14.100,49 euros y de 14.677,16 euros para el grupo sin estudio hemodinámico. Conclusiones: la realización del estudio hemodinámico es una herramienta coste-efectiva en la profilaxis de la hemorragia digestiva varicosa en pacientes cirróticos y mantiene una relación coste efectiva

  12. Lingual and fusiform gyri in visual processing: a clinico-pathologic study of superior altitudinal hemianopia.

    OpenAIRE

    Bogousslavsky, J; Miklossy, J; Deruaz, J P; Assal, G; Regli, F

    1987-01-01

    A macular-sparing superior altitudinal hemianopia with no visuo-psychic disturbance, except impaired visual learning, was associated with bilateral ischaemic necrosis of the lingual gyrus and only partial involvement of the fusiform gyrus on the left side. It is suggested that bilateral destruction of the lingual gyrus alone is not sufficient to affect complex visual processing. The fusiform gyrus probably has a critical role in colour integration, visuo-spatial processing, facial recognition...

  13. Madicolous Chironomidae from the Brazilian Atlantic Forest: a checklist with notes on altitudinal distributions (Diptera, Insecta)

    Science.gov (United States)

    Shimabukuro, Erika Mayumi; Trivinho-Strixino, Susana

    2018-01-01

    Abstract Thin layers of water running over rocky surfaces are characteristic of madicolous habitats, which harbor a peculiar Chironomidae community. However, information on the identity, distribution, and ecology of madicolous chironomids in the Neotropical region are still sparse. The main purpose of this research is to reveal and contribute to the ecology of madicolous Chironomidae species, especially regarding their altitudinal distribution in the Atlantic Forest. Sampling was performed using our own designed emergence traps deployed from 0 to 2700 m a.s.l. in 70 sites in three mountains in southeastern Brazil. Sixty taxa of chironomids were collected and identified, of which only 22 are known to science. Most of the species showed a wider distribution than previously known, both in terms of geographic and altitudinal ranges, while others showed significant association with particular altitudinal bands (as evidenced by the indicator species analysis). Atlantic Forest mountainous regions are known to harbor one of the richest fauna in the world and have been suffering from several types of environmental impacts, including climate change, which will especially affect taxa living in specialized habitats. The narrow range of tolerance to environmental conditions verified for mountain species, and the fact that many of them are rare and endemic, make the conservation efforts in these areas indispensable. PMID:29706784

  14. Seasonal and altitudinal variation in roe deer (Capreolus pygargus tianschanicus diet on Jeju Island, South Korea

    Directory of Open Access Journals (Sweden)

    Pradeep Adhikari

    2016-12-01

    Full Text Available In order to understand the feeding ecology and dietary differences of roe deer (Capreolus pygargus tianschanicus in different seasons and altitudes, this study was carried out at three altitudinal sites (Songdang 250–270 m above sea level (ASL, Aradong 330–370 m ASL, Mt. Hallasan 1100 m ASL on Jeju Island, South Korea. Altogether, 205 plants taxa of six categories of foods (forbs-climbers, graminoids, trees, shrubs, conifers, and ferns were identified using morphological and molecular analyses. The highest number of dietary plants was found in summer (93 taxa and at Aradong (124 taxa and lowest at Songdang (71 taxa and in winter (51 taxa. Food categories were significantly different among the seasons (F = 15.646, p < 0.05 and altitudinal sites (F = 3.941, p < 0.05. This study revealed that dietary selectivity of roe deer shifted with seasonal and altitudinal variations and preferred to the nutritive and low fibers food.

  15. Altitudinal vegetation belts in the high-Andes of central Chile (33°S Pisos altitudinales de vegetación en los Andes de Chile central (33°S

    Directory of Open Access Journals (Sweden)

    Lohengrin A. Cavieres

    2000-06-01

    ón. Los objetivos de este articulo son: 1 describir los cambios altitudinales de la de vegetación por sobre el límite arbóreo, 2 comparar la delimitación de los pisos de vegetación usando fisionomía y métodos floristicos (uno cualitativo basado en cambios en la composición de especies, y otro cuantitativo basado en cambios en la abundancia relativa de las especies; y 3 detectar algunos factores medioambientales responsables de los patrones de distribución altitudinal de la vegetación entre los 2.100 y 3.700 msnm en los Andes de Santiago, Chile central (33°S. Se encontró una completa concordancia entre los diferentes métodos en delimitar el piso subandino. Sin embargo, en el piso andino inferior (el piso de los cojines los métodos florísticos lo subdividieron en 2-3 sub-pisos. Las altitudes 3.500-3.700 m que forman el piso andino superior segregaron en forma separada en los métodos florísticos ya que no tienen especies en común. En consecuencia, la descripción fisonómica pierde información relevante sobre la distribución de las especies, especialmente a mayores altitudes. La temperatura media anual y el contenido de nitrógeno del suelo fueron los principales factores medioambientales involucrados en la delimitación altitudinal de la vegetación de los Andes de Chile central

  16. Altitudinal variations of ground tissue and xylem tissue in terminal shoot of woody species: implications for treeline formation.

    Science.gov (United States)

    Chen, Hong; Wang, Haiyang; Liu, Yanfang; Dong, Li

    2013-01-01

    1. The terminal shoot (or current-year shoot), as one of the most active parts on a woody plant, is a basic unit determining plant height and is potentially influenced by a variety of environmental factors. It has been predicted that tissues amount and their allocation in plant stems may play a critical role in determining plant size in alpine regions. The primary structure in terminal shoots is a key to our understanding treeline formation. The existing theories on treeline formation, however, are still largely lacking of evidence at the species level, much less from anatomy for the terminal shoot. 2. The primary structures within terminal shoot were measured quantitatively for 100 species from four elevation zones along the eastern slope of Gongga Mountain, southwestern China; one group was sampled from above the treeline. An allometric approach was employed to examine scaling relationships interspecifically, and a principal components analysis (PCA) was performed to test the relation among primary xylem, ground tissue, species growth form and altitude. 3. The results showed that xylem tissue size was closely correlated with ground tissue size isometrically across species, while undergoing significant y- or/and x-intercept shift in response to altitudinal belts. Further, a conspicuous characteristic of terminal shoot was its allocation of contrasting tissues between primary xylem and ground tissues with increasing elevation. The result of the PCA showed correlations between anatomical variation, species growth form/height classes and environment. 4. The current study presents a comparative assessment of the allocation of tissue in terminal shoot across phylogenically and ecologically diverse species, and analyzes tissue, function and climate associations with plant growth forms and height classes among species. The interspecific connection between primary xylem ratio and plant size along an elevation gradient suggests the importance of primary xylem in explaining

  17. Altitudinal variations of ground tissue and xylem tissue in terminal shoot of woody species: implications for treeline formation.

    Directory of Open Access Journals (Sweden)

    Hong Chen

    Full Text Available 1. The terminal shoot (or current-year shoot, as one of the most active parts on a woody plant, is a basic unit determining plant height and is potentially influenced by a variety of environmental factors. It has been predicted that tissues amount and their allocation in plant stems may play a critical role in determining plant size in alpine regions. The primary structure in terminal shoots is a key to our understanding treeline formation. The existing theories on treeline formation, however, are still largely lacking of evidence at the species level, much less from anatomy for the terminal shoot. 2. The primary structures within terminal shoot were measured quantitatively for 100 species from four elevation zones along the eastern slope of Gongga Mountain, southwestern China; one group was sampled from above the treeline. An allometric approach was employed to examine scaling relationships interspecifically, and a principal components analysis (PCA was performed to test the relation among primary xylem, ground tissue, species growth form and altitude. 3. The results showed that xylem tissue size was closely correlated with ground tissue size isometrically across species, while undergoing significant y- or/and x-intercept shift in response to altitudinal belts. Further, a conspicuous characteristic of terminal shoot was its allocation of contrasting tissues between primary xylem and ground tissues with increasing elevation. The result of the PCA showed correlations between anatomical variation, species growth form/height classes and environment. 4. The current study presents a comparative assessment of the allocation of tissue in terminal shoot across phylogenically and ecologically diverse species, and analyzes tissue, function and climate associations with plant growth forms and height classes among species. The interspecific connection between primary xylem ratio and plant size along an elevation gradient suggests the importance of primary

  18. Patrones de diversidad de aves a lo largo de un gradiente latitudinal de bosques ribereños del río Paraná medio, Argentina

    OpenAIRE

    Berduc, Alfredo; Lorenzón, Rodrigo Ezequiel; Beltzer, Adolfo Héctor

    2015-01-01

    Se estudió la variación de la riqueza de especies (diversidad alfa), la diversidad beta, la abundancia y la equidad de ensambles de aves a lo largo de un gradiente latitudinal de 500 km de bosques ribereños. Se muestrearon 5 localidades ubicadas en dirección norte-sur mediante una técnica mixta: transectos y puntos de conteo. La riqueza de especies decreció con el incremento de la latitud, reproduciendo el patrón de la riqueza regional informado en estudios previos. Los resultados apoyaron la...

  19. Registro preliminar de Basidiomycetes del Páramo De Ocetá (Monguí-Boyacá, Colombia

    Directory of Open Access Journals (Sweden)

    Helbert David Siabatto F.

    2005-07-01

    órdenes: Agaricales, Afiloforales, Lycoperdales y Russulales. Se realizó un análisis de acuerdo al gradiente altitudinal muestreado (3.265 a 3.455 msnm y su incidencia en la morfología, indicando posibles adaptaciones en contraste a colecciones consultadas.

  20. Irradiance gradients

    International Nuclear Information System (INIS)

    Ward, G.J.; Heckbert, P.S.; Technische Hogeschool Delft

    1992-04-01

    A new method for improving the accuracy of a diffuse interreflection calculation is introduced in a ray tracing context. The information from a hemispherical sampling of the luminous environment is interpreted in a new way to predict the change in irradiance as a function of position and surface orientation. The additional computation involved is modest and the benefit is substantial. An improved interpolation of irradiance resulting from the gradient calculation produces smoother, more accurate renderings. This result is achieved through better utilization of ray samples rather than additional samples or alternate sampling strategies. Thus, the technique is applicable to a variety of global illumination algorithms that use hemicubes or Monte Carlo sampling techniques

  1. Recursos florísticos de la cuenca baja del río mayo, Sonora

    Directory of Open Access Journals (Sweden)

    Julio César Duarte Ruiz

    2014-06-01

    Full Text Available En México se presentan prácticamente todos los grandes tipos de vegetación que existen en el mundo y su distribución a menudo es compleja. El objetivo del trabajo consistió en realizar un listado de la flora silvestre ribereña del Río Mayo, localizado en el sur del estado de Sonora, para conocer su composición. La recolección de especímenes se realizó mediante la técnica de intercepción o línea de Canfield (1941, en 15 sitios con dos repeticiones sumando 30 transectos. Se encontraron un total de 40 familias, 79 géneros y 99 especies. Las familias mejor representadas fueron: Leguminoseae, Cactaceae, Gramineae, Compositae, Chenopodiaceae, Salicaceae, Solanaceae, Euphorbiaceae, Amaranthaceae y Asteraceae. La dominante fue Leguminoseae con vegetación de bosque espinoso compuesta por Acacia cymbispina, Acacia farnesiana, Parkinsonia aculeata y Prosopis juliflora. Resulta perceptible la pérdida de flora debido al cambio de uso de suelo. Especies representativas de la zona riparia como Populus fremontii y Salix bonplandiana están desapareciendo por alteración del ecosistema. Poblaciones de mangle como Rhizophora mangle y Conocarpus erectus están disminuidas. El área estudiada es rica en especies a pesar de la perturbación. La diversidad varía de acuerdo al gradiente altitudinal y el número de especies guarda relación con los géneros y familias recolectadas. La agricultura, acuicultura, ganadería, la industria pesquera y la urbanización, son los giros que causan mayor afectación en los ecosistemas

  2. Novo registro altitudinal de Trichodactylus fluviatilis (Latreille, 1828 (Decapoda, Trichodactylidae no Brasil = New altitudinal record of Trichodactylus fluviatilis (Latreille, 1828 (Decapoda, Trichodactylidae in Brazil

    Directory of Open Access Journals (Sweden)

    Samuel Campos Gomides

    2009-07-01

    Full Text Available Trichodactylus fluviatilis (Latreille, 1828 (Decapoda, Trichodactylidae é uma espécie de caranguejo que habita rios e riachos montanhosos em altitudes até aproximadamente 500 m. Sua distribuição ocorre na América do Sul, desde as bacias costeiras da faixa leste do Brasil até a bacia do alto Paraná e na Argentina. O objetivo do presente trabalho foi registrar a ocorrência de T. fluviatilis em uma Unidade de Conservação de Juiz de Fora, Minas Gerais, e fornecer um novo registro altitudinal dessa espécie noBrasil. As amostras foram obtidas de outubro de 2004 a julho de 2005. Foram coletados três indivíduos vivos, dois machos e uma fêmea da espécie. Também foram analisados 16 regurgitos estomacais do cágado Hydromedusa maximiliani, dos quais, em seis foram encontrados partes corporais deste crustáceo. Muitas espécies de caranguejos do Brasil dafamília Trichodactylidae vivem em regiões acima de 500m do nível do mar. No presente estudo, T. fluviatilis foi coletado a 770 m de altitude, ampliando assim a faixa de distribuição altitudinal dessa espécie no Brasil. Até o presente estudo não existiam relatos de T. fluviatilis no município de Juiz de Fora, portanto este estudo também se constitui em um novo registro desse tricodatilídeo em Minas Gerais. Trichodactylus fluviatilis (Latreille, 1828 (Decapoda, Trichodactylidae is a crab species that lives in mountainous rivers and streams at altitudes up to 500m. Its distribution ranges from South America from the Basins of eastern coast of Brazil to basins of the Upper Paraná River and Argentina. The main objective of this study was to register a new occurrence of T. fluviatilis at a Conservation Unit in Juiz de Fora, Minas Gerais and provide a new altitudinal record for this species in Brazil. The samples were taken between October 2004 and July 2005. We collected three live T. fluviatilis individuals – two males and one female. We also analyzed the stomach contents of 16

  3. Ethnobotanical Study of Herbaceous Flora along an Altitudinal Gradient in Bharmour Forest Division, District Chamba of Himachal Pradesh, India

    Directory of Open Access Journals (Sweden)

    Kehar S. Thakur

    2014-01-01

    Full Text Available The present ethnobotanical study was carried out in Holi (Deol, Kut, Dal, and Lahaud Dhar forest range and in Bharmor (Seri, Bharmour, Malkauta, Bharmani, Harsar, Dhancho, Sundrasi, Gorikund, and Manimahesh forest range to obtain information on the plants used by the local inhabitants for several purposes. A total of 54 plants were recorded in this study. The plants are employed to treat simple diseases (cough, cold, fever, and burns and some serious diseases (typhoid, jaundice, and kidney disease. Some of the plants are also used as incense for religious ceremonies and several other daily needs. But due to absence of scientific monitoring of plants, their cultivation, harvesting, and management techniques as well as sustainable use and lack of awareness of social factors, the availability of valuable plant resources is decreasing at an alarming rate. In addition, the indigenous knowledge regarding the use of lesser-known plants of this region is also rapidly declining. Therefore, the documentation of plant resources is a necessary step towards the goal of raising awareness in local communities about the importance of these plants and their further conservation.

  4. Environmental controls on the distribution and diversity of lentic Chironomidae (Insecta: Diptera) across an altitudinal gradient in tropical South America

    NARCIS (Netherlands)

    Matthews-Bird, F.; Gosling, W.D.; Coe, A.L.; Bush, M.; Mayle, F.E.; Axford, Y.; Brooks, S.J.

    To predict the response of aquatic ecosystems to future global climate change, data on the ecology and distribution of keystone groups in freshwater ecosystems are needed. In contrast to mid- and high-latitude zones, such data are scarce across tropical South America (Neotropics). We present the

  5. Diversity, distribution pattern and seasonal variation in moth assemblages along altitudinal gradient in Gangotri landscape area, Western Himalaya, Uttarakhand, India

    Directory of Open Access Journals (Sweden)

    A.K. Sanyal

    2013-02-01

    Full Text Available Field survey was conducted at different altitudes and land-use areas in the two protected areas, viz., Gangotri National Park and Govind National Park of Uttarkashi District, Uttarakhand, India. A total of 475 specimens of moth representing 436 morphospecies were collected using light trap method during the survey conducted between September 2008-May 2010. Preliminary findings show a decreasing diversity with increasing altitude. Subalpine areas were least diverse and subtropical areas had the highest diversity of moths. The greatest number of specimens were collected during the summer and post-monsoon period. The lunar phase had a significant effect on catch success with new moon days resulting in the largest catches and full moon days resulting in the least number of species as well as individuals. Of the thirty two species mentioned in Appendix 1, nine species are first time record from the state Uttarakhand. Four species are new record from Western Himalaya within Indian Territory, and also first time recorded from entire Himalayan landscape. As there was no previous comprehensive study on the moth diversity of Gangotri landscape area, all the 32 species described could be regarded as new record from these two protected areas.

  6. Organic persistent toxic substances in soils, waters and sediments along an altitudinal gradient at Mt. Sagarmatha, Himalayas, Nepal

    International Nuclear Information System (INIS)

    Guzzella, Licia; Poma, Giulia; De Paolis, Adolfo; Roscioli, Claudio; Viviano, Gaetano

    2011-01-01

    Persistent Organic Pollutants (POPs) and Polycyclic Aromatic Hydrocarbons (PAHs) are important classes of compounds of serious environmental concern. These compounds were measured in waters, sediments and soils from several high altitude sites in the Sagarmatha National Park (Nepal) and included in the Himalayan ridge. In water samples, low-level substituted PCBs and PBDEs, along with more volatile PAHs, were the most common contaminants. In sediment and soil samples, the PCB profile was mainly composed of medium-level chlorinated congeners and significantly correlated with altitude. The PAH profile for water and soil samples showed the main contribution of pyrogenic PAHs due to emissions of solid combustion, whereas the profile for sediments indicated the main contribution of pyrogenic PAHs from gasoline emissions. The PAH levels measured in Himalayan samples must be considered as low to medium contaminated, whereas the regarded Himalayan stations can be considered undisturbed remote areas concerning PCB, PBDE and OC compounds. - Highlights: → POPs were measured in environmental samples from remote lakes in the Himalaya ridge. → It was confirmed the hypothesis of Long-Range Atmospheric Transport for lighter POPs. → PAH levels in Himalayan samples must be considered as low to medium contaminated. → The stations can be considered undisturbed remote areas concerning PCB, PBDE and OCC. - Organic PTSs in environmental matrices in remote regions of the Himalayan ridge.

  7. Life-forms and clonality of vascular plants along an altitudinal gradient in E Ladakh (NW Himalayas)

    Czech Academy of Sciences Publication Activity Database

    Klimeš, Leoš

    2003-01-01

    Roč. 4, - (2003), s. 317-328 ISSN 1439-1791 R&D Projects: GA ČR GA206/01/1039; GA AV ČR KSK6005114 Institutional research plan: CEZ:AV0Z6005908 Keywords : altitude * diversity * Ladakh Subject RIV: EF - Botanics Impact factor: 1.577, year: 2003

  8. Contribution of arbuscular mycorrhizal fungi of sedges to soil aggregation along an altitudinal alpine grassland gradient on the Tibetan Plateau.

    Science.gov (United States)

    Li, Xiaoliang; Zhang, Junling; Gai, Jingping; Cai, Xiaobu; Christie, Peter; Li, Xiaolin

    2015-08-01

    The diversity of arbuscular mycorrhizal fungi (AMF) in sedges on the Tibetan Plateau remains largely unexplored, and their contribution to soil aggregation can be important in understanding the ecological function of AMF in alpine ecosystems. Roots of Kobresia pygmaea C.B. Clarke and Carex pseudofoetida Kük. in alpine Kobresia pastures along an elevational transect (4149-5033 m) on Mount Mila were analysed for AMF diversity. A structural equation model was built to explore the contribution of biotic factors to soil aggregation. Sedges harboured abundant AMF communities covering seven families and some operational taxonomic units are habitat specific. The two plant species hosted similar AMF communities at most altitudes. The relative abundance of the two sedges contributed largely to soil macroaggregates, followed by extraradical mycorrhizal hyphae (EMH) and total glomalin-related soil protein (T-GRSP). The influence of plant richness was mainly due to its indirect influence on T-GRSP and EMH. There was a strong positive correlation between GRSP and soil total carbon and nitrogen. Our results indicate that mycorrhization might not be a major trait leading to niche differentiation of the two co-occurring sedge species. However, AMF contribute to soil aggregation and thus may have the potential to greatly influence C and N cycling in alpine grasslands. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  9. Plant trait variation along an altitudinal gradient in Mediterranean high mountain grasslands: controlling the species turnover effect

    Czech Academy of Sciences Publication Activity Database

    Pescador, D. S.; de Bello, Francesco; Valladares, F.; Escudero, A.

    2015-01-01

    Roč. 10, č. 3 (2015), e0118876 E-ISSN 1932-6203 Institutional support: RVO:67985939 Keywords : intraspecific trait variability * altitude * filtering * functional diversity Subject RIV: EF - Botanics Impact factor: 3.057, year: 2015

  10. Feeding patterns of red deer along altitudinal gradient in the Bohemian Forest: the effect of habitat and season

    Czech Academy of Sciences Publication Activity Database

    Krojerová-Prokešová, Jarmila; Barančeková, Miroslava; Šustr, P.; Heurich, M.

    2010-01-01

    Roč. 16, č. 2 (2010), s. 173-184 ISSN 0909-6396 R&D Projects: GA MŠk LC06073 Institutional research plan: CEZ:AV0Z60930519 Keywords : Bavarian Forest National Park * red deer * PCA * seasonal and spatial variation * Šumava National Park Subject RIV: EG - Zoology Impact factor: 0.697, year: 2010

  11. Changes of bat activity, species richness, diversity and community composition over an altitudinal gradient in the Soutpansberg range, South Africa

    NARCIS (Netherlands)

    Linden, V.M.G.; Weier, S.M.; Gaigher, I.; Kuipers, H.J.; Weterings, M.J.A.; Taylor, P.

    2014-01-01

    Bats are important indicator species which can help in identifying areas where conservation efforts should be concentrated and whether these areas are affected by ongoing climate change. To elucidate factors limiting and influencing the elevational distribution of bats in a recognised biodiversity

  12. Relationship between survival rate of avian artificial nests and forest vegetation structure along a tropical altitudinal gradient on Mount Cameroon

    Czech Academy of Sciences Publication Activity Database

    Djomo Nana, E.; Sedláček, O.; Doležal, Jiří; Dančák, Martin; Altman, Jan; Svoboda, M.; Majeský, L.; Hořák, D.

    2015-01-01

    Roč. 47, č. 6 (2015), s. 758-764 ISSN 0006-3606 R&D Projects: GA ČR(CZ) GAP505/11/1617 Institutional support: RVO:67985939 Keywords : artificial nest s * vegetation parameters * West-Central Africa Subject RIV: EH - Ecology, Behaviour Impact factor: 1.944, year: 2015

  13. Ethnobotanical Study of Herbaceous Flora along an Altitudinal Gradient in Bharmour Forest Division, District Chamba of Himachal Pradesh, India.

    Science.gov (United States)

    Thakur, Kehar S; Kumar, Munesh; Bawa, Rajan; Bussmann, Rainer W

    2014-01-01

    The present ethnobotanical study was carried out in Holi (Deol, Kut, Dal, and Lahaud Dhar) forest range and in Bharmor (Seri, Bharmour, Malkauta, Bharmani, Harsar, Dhancho, Sundrasi, Gorikund, and Manimahesh) forest range to obtain information on the plants used by the local inhabitants for several purposes. A total of 54 plants were recorded in this study. The plants are employed to treat simple diseases (cough, cold, fever, and burns) and some serious diseases (typhoid, jaundice, and kidney disease). Some of the plants are also used as incense for religious ceremonies and several other daily needs. But due to absence of scientific monitoring of plants, their cultivation, harvesting, and management techniques as well as sustainable use and lack of awareness of social factors, the availability of valuable plant resources is decreasing at an alarming rate. In addition, the indigenous knowledge regarding the use of lesser-known plants of this region is also rapidly declining. Therefore, the documentation of plant resources is a necessary step towards the goal of raising awareness in local communities about the importance of these plants and their further conservation.

  14. Above ground perennial plant biomass across an altitudinal and land-use gradient in Namaqualand, South Africa

    CSIR Research Space (South Africa)

    Anderson, PML

    2010-08-01

    Full Text Available palatable and highly palatable species was determined. A paired Wilcoxon sign-rank test was used to test for sig- nificant differences in the grazing scores. Didelta spinosa (L.f.) Aiton Dimorphotheca cuneata (Thunb.) Less. Diospyros glabra (L.) De...-normal and the Kruskal–Wallis test Qwas used to test 239for significant differences. A paired Wilcoxon sign-ranks test 240was used to test for significant differences in total biomass and 241biomass graded according to palatability on either side of the 242fence (Zar...

  15. Efecto de las actividades humanas sobre la diversidad de mamíferos terrestres en un gradiente altitudinal

    Directory of Open Access Journals (Sweden)

    Lilliana Piedra C

    2000-03-01

    Full Text Available The effect of human activity on terrestrial mammals was studied with footprint counts in Guanacaste, Costa Rica (10°30'N, 85°40'W in February 1998 (in fifty 2 m² quadrats. The most common species were Canis latrans, Didelphis marsupialis, Odoicoleus virginianus, Dasyprocta punctata and Tapirus bairdii. No stastically significant association was found between humna activity and mammal frequency in the footprint counts.

  16. Seasonal and altitudinal variation in roe deer (Capreolus pygargus tianschanicus) diet on Jeju Island, South Korea

    OpenAIRE

    Adhikari, Pradeep; Park, Seon-Mi; Kim, Tae-Wook; Lee, Jun-Won; Kim, Ga-Ram; Han, Sang-Hyun; Oh, Hong-Shik

    2016-01-01

    In order to understand the feeding ecology and dietary differences of roe deer (Capreolus pygargus tianschanicus) in different seasons and altitudes, this study was carried out at three altitudinal sites (Songdang 250–270 m above sea level (ASL), Aradong 330–370 m ASL, Mt. Hallasan 1100 m ASL) on Jeju Island, South Korea. Altogether, 205 plants taxa of six categories of foods (forbs-climbers, graminoids, trees, shrubs, conifers, and ferns) were identified using morphological and molecular ana...

  17. Limitaciones del IMC como indicador exclusivo de estado nutricional

    OpenAIRE

    Moreno Romero, Susana; Dipierri, José Edgardo; Marrodán, María D.

    2007-01-01

    El presente trabajo tiene como objetivo determinar el potencial diagnóstico y las limitaciones del uso del Índice de Masa Corporal como único indicador del estado nutricional. Para ello se analizó una muestra constituida por 2155 sujetos de ambos sexos, con edades comprendidas entre los 6 y 18 años y pertenecientes a tres poblaciones jujeñas que difieren en ubicación altitudinal y nivel socieconómico (NSE): 1.) Susques, localidad rural situada a 3675 m.s.n.m; 2.) Alto Comedero, barrio perifér...

  18. Foliar δ13C Showed No Altitudinal Trend in an Arid Region and Atmospheric Pressure Exerted a Negative Effect on Plant δ13C

    Directory of Open Access Journals (Sweden)

    Zixun Chen

    2017-07-01

    Full Text Available Previous studies have suggested foliar δ13C generally increases with altitude. However, some observations reported no changes or even decreased trends in foliar δ13C. We noted that all the studies in which δ13C increased with elevation were conducted in the human regions, whereas those investigations in which δ13C did not vary or decreased were conducted in areas with water stress. Thus, we proposed that the pattern of increasing δ13C with elevation is not a general one, and that δ13C may remain unchanged or decrease in plants grown in arid environments. To test the hypothesis, we sampled plants along altitude gradients on the shady and sunny slopes of Mount Tianshan characterized by arid and semiarid climates. The measurements of foliar δ13C showed no altitudinal trends for the plants grown on either of the slopes. Therefore, this study supported our hypothesis. In addition, the present study addressed the effect of atmospheric pressure on plant δ13C by accounting for the effects of temperature and precipitation on δ13C. This study found that the residual foliar δ13C increased with increasing altitude, suggesting that atmospheric pressure played a negative role in foliar δ13C.

  19. Will Climate Change, Genetic and Demographic Variation or Rat Predation Pose the Greatest Risk for Persistence of an Altitudinally Distributed Island Endemic?

    Directory of Open Access Journals (Sweden)

    Alison Shapcott

    2012-11-01

    Full Text Available Species endemic to mountains on oceanic islands are subject to a number of existing threats (in particular, invasive species along with the impacts of a rapidly changing climate. The Lord Howe Island endemic palm Hedyscepe canterburyana is restricted to two mountains above 300 m altitude. Predation by the introduced Black Rat (Rattus rattus is known to significantly reduce seedling recruitment. We examined the variation in Hedyscepe in terms of genetic variation, morphology, reproductive output and demographic structure, across an altitudinal gradient. We used demographic data to model population persistence under climate change predictions of upward range contraction incorporating long-term climatic records for Lord Howe Island. We also accounted for alternative levels of rat predation into the model to reflect management options for control. We found that Lord Howe Island is getting warmer and drier and quantified the degree of temperature change with altitude (0.9 °C per 100 m. For H. canterburyana, differences in development rates, population structure, reproductive output and population growth rate were identified between altitudes. In contrast, genetic variation was high and did not vary with altitude. There is no evidence of an upward range contraction as was predicted and recruitment was greatest at lower altitudes. Our models predicted slow population decline in the species and that the highest altitude populations are under greatest threat of extinction. Removal of rat predation would significantly enhance future persistence of this species.

  20. Vegetation composition and altitudinal distribution of Andean rain forests in El Angel and Guandera reserves, northern Ecuador

    NARCIS (Netherlands)

    Moscol Olivera, M.C.; Cleef, A.M.

    2009-01-01

    Patterns of vascular plant species composition and structure of the remaining rain forest of the Andean Cordillera in northern Ecuador were studied in two reserves: Guandera and El Angel. Thirty three plots located between 3300 and 3700 in were examined along two altitudinal transects crossing the

  1. Vegetation composition and altitudinal distribution of Andean rain forests in El Angel and Guandera reserves, northern Ecuador

    NARCIS (Netherlands)

    Moscol Olivera, M.C.; Cleef, A.M.

    2009-01-01

    Patterns of vascular plant species composition and structure of the remaining rain forest of the Andean Cordillera in northern Ecuador were studied in two reserves: Guandera and El Angel. Thirty three plots located between 3300 and 3700 m were examined along two altitudinal transects crossing the

  2. Bionomics of Anopheline species and malaria transmission dynamics along an altitudinal transect in Western Cameroon

    Directory of Open Access Journals (Sweden)

    Toto Jean-Claude

    2010-05-01

    Full Text Available Abstract Background Highland areas of Africa are mostly malaria hypoendemic, due to climate which is not appropriate for anophelines development and their reproductive fitness. In view of designing a malaria control strategy in Western Cameroon highlands, baseline data on anopheline species bionomics were collected. Methods Longitudinal entomological surveys were conducted in three localities at different altitudinal levels. Mosquitoes were captured when landing on human volunteers and by pyrethrum spray catches. Sampled Anopheles were tested for the presence of Plasmodium circumsporozoite proteins and their blood meal origin with ELISA. Entomological parameters of malaria epidemiology were assessed using Mac Donald's formula. Results Anopheline species diversity and density decreased globally from lowland to highland. The most aggressive species along the altitudinal transect was Anopheles gambiae s.s. of S molecular form, followed in the lowland and on the plateau by An. funestus, but uphill by An. hancocki. An. gambiae and An. ziemanni exhibited similar seasonal biting patterns at the different levels, whereas different features were observed for An. funestus. Only indoor resting species could be captured uphill; it is therefore likely that endophilic behaviour is necessary for anophelines to climb above a certain threshold. Of the ten species collected along the transect, only An. gambiae and An. funestus were responsible for malaria transmission, with entomological inoculation rates (EIR of 90.5, 62.8 and zero infective bites/human/year in the lowland, on the plateau and uphill respectively. The duration of gonotrophic cycle was consistently one day shorter for An. gambiae as compared to An. funestus at equal altitude. Altitudinal climate variations had no effect on the survivorship and the subsequent life expectancy of the adult stage of these malaria vectors, but most probably on aquatic stages. On the contrary increasing altitude

  3. Are altitudinal limits of equatorial stream insects reflected in their respiratory performance?

    DEFF Research Database (Denmark)

    Jacobsen, Dean; Brodersen, Klaus Peter

    2008-01-01

    .6 between genera at 17 °C, and from 1.3 to 2.5 at 5 °C. Q10 values for this temperature interval ranged 1.5-2.9 (mean 2.3). The two "high-altitude" genera had higher respiration rates at low temperature and oxygen saturation, and their respiration rate saturated at lower temperatures, than three of the four......-term physiological tolerance of low temperature and oxygen concentration. 5. Multiple regressions (based on respiration experiments and previously obtained relationships between water temperature, oxygen saturation and altitude) were used to predict how respiration rates should vary with altitude. At the upper limit...... saturation. Further quantitative and long-term studies on survival and recruitment in populations and communities are needed to determine the importance of temperature and oxygen for altitudinal limits of aquatic insects....

  4. Can variation in risk of nest predation explain altitudinal migration in tropical birds?

    Science.gov (United States)

    Boyle, W Alice

    2008-03-01

    Migration is among the best studied of animal behaviors, yet few empirical studies have tested hypotheses explaining the ultimate causes of these cyclical annual movements. Fretwell's (1980) hypothesis predicts that if nest predation explains why many tropical birds migrate uphill to breed, then predation risk must be negatively associated with elevation. Data from 385 artificial nests spanning 2,740 m of elevation on the Atlantic slope of Costa Rica show an overall decline in predation with increasing elevation. However, nest predation risk was highest at intermediate elevations (500-650 m), not at lowest elevations. The proportion of nests depredated by different types of predators differed among elevations. These results imply that over half of the altitudinal migrant bird species in this region migrate to safer breeding areas than their non-breeding areas, suggesting that variation in nest predation risk could be an important benefit of uphill migrations of many species.

  5. Reservorios y flujos de carbono en un gradiente de intensificación de usos del suelo de un ecosistema mediterráneo: factores de control y capacidad de secuestro de carbono

    OpenAIRE

    Almagro Bonmatí, María

    2011-01-01

    Se estudia el ciclo del carbono en diferentes usos del suelo (uso forestal, campo agrícola abandonado y olivar de secano) de un ecosistema mediterráneo ante la perspectiva del cambio climático. La hipótesis general de esta tesis es que los cambios en los patrones (estructura y distribución espacial) y tipo de vegetación resultantes de la intensificación de los usos del suelo causarán alteraciones en las condiciones microclimáticas (temperatura y humedad del suelo) y en las características del...

  6. Reservorios y flujos de carbono en un gradiente de intensificación de usos del suelo de un ecosistema mediterráneo: factores de control y capacidad de secuestro de carbono = Carbon pools and fluxes along a land use intensification gradient in a Mediterranean ecosystem: controls and carbon sequestration capacity

    OpenAIRE

    Almagro Bonmatí, María

    2011-01-01

    Se estudia el ciclo del carbono en diferentes usos del suelo (uso forestal, campo agrícola abandonado y olivar de secano) de un ecosistema mediterráneo ante la perspectiva del cambio climático. La hipótesis general de esta tesis es que los cambios en los patrones (estructura y distribución espacial) y tipo de vegetación resultantes de la intensificación de los usos del suelo causarán alteraciones en las condiciones microclimáticas (temperatura y humedad del suelo) y en las características del...

  7. Integrating evolutionary and functional tests of adaptive hypotheses: a case study of altitudinal differentiation in hemoglobin function in an Andean Sparrow, Zonotrichia capensis.

    Science.gov (United States)

    Cheviron, Zachary A; Natarajan, Chandrasekhar; Projecto-Garcia, Joana; Eddy, Douglas K; Jones, Jennifer; Carling, Matthew D; Witt, Christopher C; Moriyama, Hideaki; Weber, Roy E; Fago, Angela; Storz, Jay F

    2014-11-01

    In air-breathing vertebrates, the physiologically optimal blood-O2 affinity is jointly determined by the prevailing partial pressure of atmospheric O2, the efficacy of pulmonary O2 transfer, and internal metabolic demands. Consequently, genetic variation in the oxygenation properties of hemoglobin (Hb) may be subject to spatially varying selection in species with broad elevational distributions. Here we report the results of a combined functional and evolutionary analysis of Hb polymorphism in the rufous-collared sparrow (Zonotrichia capensis), a species that is continuously distributed across a steep elevational gradient on the Pacific slope of the Peruvian Andes. We integrated a population genomic analysis that included all postnatally expressed Hb genes with functional studies of naturally occurring Hb variants, as well as recombinant Hb (rHb) mutants that were engineered through site-directed mutagenesis. We identified three clinally varying amino acid polymorphisms: Two in the α(A)-globin gene, which encodes the α-chain subunits of the major HbA isoform, and one in the α(D)-globin gene, which encodes the α-chain subunits of the minor HbD isoform. We then constructed and experimentally tested single- and double-mutant rHbs representing each of the alternative α(A)-globin genotypes that predominate at different elevations. Although the locus-specific patterns of altitudinal differentiation suggested a history of spatially varying selection acting on Hb polymorphism, the experimental tests demonstrated that the observed amino acid mutations have no discernible effect on respiratory properties of the HbA or HbD isoforms. These results highlight the importance of experimentally validating the hypothesized effects of genetic changes in protein function to avoid the pitfalls of adaptive storytelling. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please

  8. Ignored fungal community in activated sludge wastewater treatment plants: diversity and altitudinal characteristics.

    Science.gov (United States)

    Niu, Lihua; Li, Yi; Xu, Lingling; Wang, Peifang; Zhang, Wenlong; Wang, Chao; Cai, Wei; Wang, Linqiong

    2017-02-01

    Fungi are important contributors to the various functions of activated sludge wastewater treatment plants (WWTPs); however, the diversity and geographic characteristics of fungal populations have remained vastly unexplored. Here, quantitative polymerase chain reaction and 454 pyrosequencing were combined to investigate the abundance and diversity of the activated sludge fungal communities from 18 full-scale municipal WWTPs in China. Phylogenetic taxonomy revealed that the members of the fungal communities were assigned to 7 phyla and 195 genera. Ascomycota and Basidiomycota were the most abundant phyla, dominated by Pluteus, Wickerhamiella, and Penicillium. Twenty-three fungal genera, accounting for 50.1 % of the total reads, were shared by 18 WWTPs and constituted a core fungal community. The fungal communities presented similar community diversity but different community structures across the WWTPs. Significant distance decay relationships were observed for the dissimilarity in fungal community structure and altitudinal distance between WWTPs. Additionally, the community evenness increased from 0.25 to 0.7 as the altitude increased. Dissolved oxygen and the C/N ratio were determined to be the most dominant contributors to the variation in fungal community structure via redundancy analysis. The observed data demonstrated the diverse occurrence of fungal species and gave a marked view of fungal community characteristics based on the previously unexplored fungal communities in activated sludge WWTPs.

  9. ASSESSMENT OF ANTIMICROBIAL AND PHYTOCHEMICAL POTENTIALS OF HIGH ALTITUDINAL NEPALESE LICHENS

    Directory of Open Access Journals (Sweden)

    Bijaya Laxmi Maharjan

    2011-10-01

    Full Text Available Lichens and lichen products have been used in traditional medicines for centuries. The lichens of the high altitudinal meadow of MCA (Manaslu Conservation Area have remained unexplored for which this research has been conducted with an aim of unveiling the phytochemical and antimicrobial properties of lichens present there. Four densely populated lichen species namely Usnea longifolia, Setraria spp, Parmotrema reticulatum and Evernastrium nepalense were chosen for the study. The extracts of these species were obtained in 6 different solvents viz. hexane, chloroform, ethyl acetate, acetone, methanol and water by soxhlet extraction method and the antimicrobial assay was carried out by agar well diffusion method. The extract yield varied from 0.07 -29.4%. The extracts obtained showed the presence of volatile oil, saponins, coumarins and quinines, flavonic glycosides and carotenoids. The ethyl acetate fraction of E. nepalense and U. longifolia were found to be most effective against all the 8 clinical bacterial pathogens and 5 phytopathogenic fungi tested. The extracts of Cetraria spp and P. milghenensis were found to be specifically inhibiting the fungal pathogens compared to the bacterial pathogens. Generally the lichen extracts tested demonstrated antimicrobial effect which suggests a possibility of their use in treatment of various diseases caused by these and similar microorganisms.

  10. The effects of forest-savanna-grassland gradients on bird communities of Chiquitano Dry Forests domain, in western Brazil.

    Science.gov (United States)

    Godoi, Mauricio N; Souza, Edivaldo O DE

    2016-01-01

    Different vegetation types are distributed in mountains according to altitude, topography and soil. The composition and structure of bird communities in these areas can change in relation to the vegetation gradient, with particular communities occupying each habitat type. In this study we present the changes in composition, species richness and bird abundance over the gradient of forests, savannas and altitudinal grasslands of Maciço do Urucum, a mountainous region located in the Chiquitano Dry Forests domain in western Brazil. We recorded 165 bird species through qualitative and quantitative methods. Forested savannas, riparian forests and submontane forests presented the highest richness and abundance of birds, while arboreal savannas and altitudinal grasslands had intermediate and low values, respectively. The bird composition was similar between riparian and submontane forests, while other vegetation types present more dissimilar bird communities. Our results show differences in composition, richness and bird abundance among the vegetation types present at Maciço do Urucum, and highlight an important function of vegetation gradients for the conservation of bird communities in mountains. Additionally, this is the first study of the bird communities in the Brazilian Chiquitano Dry Forests, an important domain in the west of Brazil which has been poorly studied.

  11. Insect temperature-body size trends common to laboratory, latitudinal and seasonal gradients are not found across altitudes

    DEFF Research Database (Denmark)

    Horne, Curtis R.; Hirst, Andrew G.; Atkinson, David

    2018-01-01

    Body size affects rates of most biological and ecological processes, from individual performance to ecosystem function, and is fundamentally linked to organism fitness. Within species, size at maturity can vary systematically with environmental temperature in the laboratory and across seasons...... altitude. Although the general direction of body size clines along altitudinal gradients has been examined previously, to our knowledge altitude-body size (A-S) clines have never been synthesised quantitatively, nor compared with temperature-size (T-S) responses measured under controlled laboratory......, as well as over latitudinal gradients. Recent meta-analyses have revealed a close match in the magnitude and direction of these size gradients in various arthropod orders, suggesting that these size responses share common drivers. As with increasing latitude, temperature also decreases with increasing...

  12. The altitudinal temperature lapse rates applied to high elevation rockfalls studies in the Western European Alps

    Science.gov (United States)

    Nigrelli, Guido; Fratianni, Simona; Zampollo, Arianna; Turconi, Laura; Chiarle, Marta

    2018-02-01

    Temperature is one of the most important aspects of mountain climates. The relationships between air temperature and rockfalls at high-elevation sites are very important to know, but are also very difficult to study. In relation to this, a reliable method to estimate air temperatures at high-elevation sites is to apply the altitudinal temperature lapse rates (ATLR). The aims of this work are to quantify the values and the variability of the hourly ATLR and to apply this to estimated temperatures at high-elevation sites for rockfalls studies. To calculate ATLR prior the rockfalls, we used data acquired from two automatic weather stations that are located at an elevation above 2500 m. The sensors/instruments of these two stations are reliable because subjected to an accurate control and calibration once for year and the raw data have passed two automatic quality controls. Our study has yielded the following main results: (i) hourly ATLR increases slightly with increasing altitude, (ii) it is possible to estimate temperature at high-elevation sites with a good level of accuracy using ATLR, and (iii) temperature plays an important role on slope failures that occur at high-elevation sites and its importance is much more evident if the values oscillate around 0 °C with an amplitude of ±5 °C during the previous time-period. For these studies, it is not enough to improve the knowledge on air temperature, but it is necessary to develop an integrated knowledge of the thermal conditions of different materials involved in these processes (rock, debris, ice, water). Moreover, this integrated knowledge must be acquired by means of sensors and acquisition chains with known metrological traceability and uncertainty of measurements.

  13. Seasonal and Altitudinal Prevalence of Fascioliasis in Buffalo in Eastern Nepal

    Directory of Open Access Journals (Sweden)

    Ramesh Prasad Sah

    2018-05-01

    Full Text Available Buffalo is the most important livestock commodities for milk, meat production and several other multipurpose uses distributed densely from southern tarai to northern mid-hills in Nepal. Among several internal parasitic diseases fascioliasis is highly economic one caused by Fasciola in buffaloes. However, there are only few studies carried on prevalence of fascioliasis emphasizing buffaloes in relation to seasonal (summer and rainy, and winter and altitudinal variations. Therefore, we examined prevalence of fascioliasis seasonally and vertically. For the purpose, we selected two districts of eastern Nepal and sampled from low altitude area known as Madhesha ranging from 175-200, Dhankuta from 800-1200 m, and Murtidhunga from 1800-2200 m elevation from the sea level, representing tarai, mid hills and high hills, respectively. Altogether from February 2013 to January 2014 at every two months interval we collected 798 fecal samples from buffaloes; 282 from Murtidhunga, 239 from Dhankuta and 277 from Madhesha. The samples were examined microscopically for the presence of Fasciola eggs using sedimentation technique. Results showed that overall prevalence of fascioliasis in buffaloes was 39.9% (319/798, ranging highest 42.6%in Madhesha followed by 39.7% in Murtidhunga and 37.2% in Dhankuta, respectively. The prevalence of fascioliasis was found to be significantly (p <0.05 high in winter (44.9% comparing to rainy season (34.4%. The prevalence of fascioliasis in buffaloes was relatively higher in low altitude than high altitude, although it was not statistically significant (p <0.05. In our findings the female buffaloes showed higher prevalence for fascioliasis than in male. Since the fascioliasis in buffaloes is highly endemic, thus strategic deworming in high risk period is recommended along with measure to prevent pasture contamination with buffalo feces.

  14. Hemoglobin function and allosteric regulation in semi-fossorial rodents (family Sciuridae) with different altitudinal ranges

    Science.gov (United States)

    Revsbech, Inge G.; Tufts, Danielle M.; Projecto-Garcia, Joana; Moriyama, Hideaki; Weber, Roy E.; Storz, Jay F.; Fago, Angela

    2013-01-01

    SUMMARY Semi-fossorial ground squirrels face challenges to respiratory gas transport associated with the chronic hypoxia and hypercapnia of underground burrows, and such challenges are compounded in species that are native to high altitude. During hibernation, such species must also contend with vicissitudes of blood gas concentrations and plasma pH caused by episodic breathing. Here, we report an analysis of hemoglobin (Hb) function in six species of marmotine ground squirrels with different altitudinal distributions. Regardless of their native altitude, all species have high Hb–O2 affinities, mainly due to suppressed sensitivities to allosteric effectors [2,3-diphosphoglycerate (DPG) and chloride ions]. This suppressed anion sensitivity is surprising given that all canonical anion-binding sites are conserved. Two sciurid species, the golden-mantled and thirteen-lined ground squirrel, have Hb–O2 affinities that are characterized by high pH sensitivity and low thermal sensitivity relative to the Hbs of humans and other mammals. The pronounced Bohr effect is surprising in light of highly unusual amino acid substitutions at the C-termini that are known to abolish the Bohr effect in human HbA. Taken together, the high O2 affinity of sciurid Hbs suggests an enhanced capacity for pulmonary O2 loading under hypoxic and hypercapnic conditions, while the large Bohr effect should help to ensure efficient O2 unloading in tissue capillaries. In spite of the relatively low thermal sensitivities of the sciurid Hbs, our results indicate that the effect of hypothermia on Hb oxygenation is the main factor contributing to the increased blood–O2 affinity in hibernating ground squirrels. PMID:24172889

  15. Murciélagos (Chiroptera: Mammalia del Parque Nacional Yurubí, Venezuela: listado taxonómico y estudio comunitario

    Directory of Open Access Journals (Sweden)

    Mariana Delgado-Jaramillo

    2011-12-01

    Full Text Available Los murciélagos constituyen el grupo de mamíferos más diversificado en la región neotropical y representan un componente clave en la dinámica de muchos ecosistemas terrestres. En este trabajo se describen los resultados de un estudio sobre la quiropterofauna del Parque Nacional Yurubí (ubicado en la zona montañosa del norte de Venezuela, se incluye un listado taxonómico y la caracterización de algunos atributos comunitarios en ambientes predominantemente boscosos. Los datos evaluados fueron obtenidos mediante la revisión de colecciones zoológicas y muestreos diversificados realizados entre febrero y julio del 2009, en un gradiente altitudinal (100-1 500m, que integra a tres unidades ecológicas: bosque semideciduo, bosque siempreverde y selva nublada. Se registraron 64 especies agrupadas en cinco familias, lo que constituye el 63% de los murciélagos conocidos en la Cordillera de la Costa. La familia Phyllostomidae fue dominante (42 especies; 66% del total, seguida por Vespertilionidae, Molossidae, Emballonuridae y Mormoopidae. La comunidad presente a baja elevación fue la más diversificada en términos taxonómicos, mientras que la del piso superior evidenció el menor grado de diversificación. Se identificaron 11 categorías tróficas, con dominancia de los insectívoros en cuanto a la riqueza taxonómica y de los frugívoros en lo que respecta a la abundancia. Nuestros resultados permiten inferir, en un contexto general, que los ecosistemas boscosos del área de estudio muestran un buen estado de conservación, en virtud de la presencia de una proporción relativamente alta de especies pertenecientes a la subfamilia Phyllostominae, cuyos componentes han sido considerados por otros autores como indicadores del grado de conservación de hábitats boscosos primarios, así como la presencia de otras especies con prioridades de conservación. Todos estos aspectos, le confieren a esta área protegida un alto valor proteccionista, en

  16. ESTUDIO DE LA VARIABILIDAD ESPACIAL DE LA TEMPERATURA DE SUPERFICIE EN EL NORTE DE LA PROVINCIA DEL NEUQUÉN CON IMÁGENES SATELITALES

    Directory of Open Access Journals (Sweden)

    Marisa Gloria Cogliati

    2015-12-01

    Full Text Available La zona noroeste de la provincia del Neuquén constituye una zona importante debido a su utilización con fines ganaderos, pero los sistemas áridos o semi áridos como el estudiado en el presente trabajo son vulnerables a procesos de uso del suelo y desertización. En este trabajo se presenta el análisis de la temperatura de superficie obtenida a partir de información del canal térmico del satélite Landsat 7 ETM+ para esa región durante un periodo fresco (otoño-invierno y cálido (primavera-verano. El estudio es parte de un proyecto de análisis geoecológico utilizando imágenes Landsat. La zona no cuenta con estudios de la variabilidad espacial de la temperatura del aire y del suelo debido a la necesidad de contar con redes de información micro o meso meteorológicas que incorporen una mayor densidad espacial de observaciones siguiendo el gradiente altitudinal y la complejidad del terreno debido a que el área es de difícil acceso y ho hay datos de superficie disponibles. Esto hace necesario utilizar métodos alternativos para el estudio de la distribución espacial de variables topo meteorológicas. La información satelital provee información en distintas escalas temporales y espaciales a un menor costo. En el presente trabajo, se obtuvo la radiancia emitida en la superficie utilizando la radiancia medida por el satélite a partir de la ecuación de transferencia radiativa y el modelo MODTRAN con información de reanálisis disponibles en línea. Se analizaron seis escenas libres de nubosidad. La temperatura de superficie presentó un comportamiento correlacionado con la topografía principalmente en el período frío, con una menor relación en verano. La isoterma de 273 K (0 oC alcanzó alturas de 1900 m, restringiéndose a alturas mayores a 3700 m en verano. Las áreas con temperatura menor a 273 K fueron las que presentaron mayores diferencias entre el período cálido y el período frío analizados

  17. $L_{0}$ Gradient Projection.

    Science.gov (United States)

    Ono, Shunsuke

    2017-04-01

    Minimizing L 0 gradient, the number of the non-zero gradients of an image, together with a quadratic data-fidelity to an input image has been recognized as a powerful edge-preserving filtering method. However, the L 0 gradient minimization has an inherent difficulty: a user-given parameter controlling the degree of flatness does not have a physical meaning since the parameter just balances the relative importance of the L 0 gradient term to the quadratic data-fidelity term. As a result, the setting of the parameter is a troublesome work in the L 0 gradient minimization. To circumvent the difficulty, we propose a new edge-preserving filtering method with a novel use of the L 0 gradient. Our method is formulated as the minimization of the quadratic data-fidelity subject to the hard constraint that the L 0 gradient is less than a user-given parameter α . This strategy is much more intuitive than the L 0 gradient minimization because the parameter α has a clear meaning: the L 0 gradient value of the output image itself, so that one can directly impose a desired degree of flatness by α . We also provide an efficient algorithm based on the so-called alternating direction method of multipliers for computing an approximate solution of the nonconvex problem, where we decompose it into two subproblems and derive closed-form solutions to them. The advantages of our method are demonstrated through extensive experiments.

  18. Fauna anfibia del valle de sibundoy, putumayo-colombia

    OpenAIRE

    MUESES-CISNEROS, JONH JAIRO

    2012-01-01

    La fauna Amphibia del Valle de Sibundoy consta de 32 especies agrupadas en dos órdenes, cinco familias y siete géneros. De éstas, cinco son especies nuevas cuya descripción se encuentra en proceso. Se amplía el límite altitudinal de otras siete y se presentan tres más para ser incluidas en la lista de anfibios de Colombia. A pesar de que en el lugar se han realizado colectas herpetológicas desde finales de los años sesenta, este estudio es el primero que se realiza en el Putumayo (uno de los ...

  19. Conservation status affects elevational gradient in bird diversity in the Himalaya: A new perspective

    Directory of Open Access Journals (Sweden)

    Prakash Kumar Paudel

    2014-12-01

    Full Text Available Understanding diversity patterns along altitudinal gradients, and their underlying causes are important for conserving biodiversity. Previous studies have focused on climatic, energetic, and geographic variables (e.g., mid-domain effects, with less attention paid to human-induced habitat modifications. We used published data of bird distributions along an elevational gradient (0–4900 m in the Nepalese Himalaya and interpolated species presence between elevational limits. The relationship between species richness and environmental variables was analyzed using generalized linear models. A low plateau relationship between bird richness and elevation was observed, with a main peak at intermediate elevations (2800 m. Across the total gradient, interpolated bird species richness had a unimodal relationship to maximum monthly precipitation and a linear response to seasonal variation in temperature, proportion of forest cover, and proportion of protected area. In lower elevations (0–2800 m, interpolated species richness had a positive and linear response to the proportion of Ramsar sites and a unimodal response to habitat heterogeneity. At higher elevations (2900–4900 m, interpolated bird richness had a positive linear response to monthly variation in temperature and a negative linear response to proportion forest cover. We conclude that factors related to human management are important drivers of elevational gradients in bird species richness. Keywords: Elevational gradient, Biogeography, Bird species richness, Conservation, Himalaya, Nepal

  20. Hemiparásitas en la franja subandina del Departamento de Cundinamarca, Colombia

    Directory of Open Access Journals (Sweden)

    Berrera Torres Eduardo

    1997-06-01

    Full Text Available The hemiparasites studied are grouped in 3 families: Loranthaceae, Viscaceae and Eremolepidaceae. 30 species belonging to 7 genera are reported in this work. Phoradendron of the Viscaceae family is the genus best represented with 15 species. The species Phoradendron aft. aequatoris, P. balslevií, P. Brittonianum y P. cymosum are reported for the first time to Colombia. Four hiperparasitic species are registered: Ixocactus hutchisonií, Phoradendron aff. aequatoris, P. dipterum and Struthanthus orbicularis. The taxa studied are distributed in altitudinal ranges from the lower montane forest. The diversity of hemiparasitic species is greater in the western slope of the Eastern Andean mountain ranga. This flora correspond to 33 % of the species registered for Colombia.Las hemiparásitas estudiadas se agrupan en 3 familias: Loranthaceae, Viscaceae y Eremolepidaceae. Se registran 30 especies pertenecientes a 7 géneros: el mejor representado es Phoradendron de la familia Viscaceae, con 15 especies. Las especies Phoradendron aff. aequatoris, P. balslevií, P. brittonianum y P. cymosum se reportan por primera vez para Colombia. Además se destacan 4 especies hiperparásitas: Ixocectus hutchisonii; Phoradendron aff. aequatoris, P. dipterum y Struthanthus orbicularis. Los taxa estudiados se distribuyen en gradientes altitudinales del Bosque Subandino. La diversidad de especies hemiparásitas en el flanco occidental de la Cordillera Oriental es mayor. La comparación de los registros obtenidos con los provenientes de otros lugares, en el territorio colombiano, indica que esta flora constituye aproximadamente el 33%.

  1. Dendroecological studies of rhododendron campanulatum d. don along the elevational gradient of manaslu conservation area, nepal himalaya

    International Nuclear Information System (INIS)

    Prabinarana, A.; Koirala, M.; Boonchird, C.

    2017-01-01

    The increase in temperature due to global warming is affecting forest ecosystems worldwide. At the treeline ecotone growth is usually restricted by low temperatures. Recently, the impacts of climate change have been visible with the upward shift of the Himalaya fir (Abies spectabilis) in Nepal. Rhododendron campanulatum D. Don grows at the treeline ecotone and subalpine forest. Hardly any studies have been carried on this species in Nepal. The local people have reported that this species has been seen colonizing upper altitude in recent years, however, these needs to be verified with dendroecological studies. The study aims to assess the response of R. campanulatum to climatic variability and to evaluate the relationship of its basal diameter (Groundline) and age using dendroecological methods. Results reveal that the basal diameter was found to be significantly correlated with age (r2= 0.824, p<0.00001). Using the basal diameter age equations, attempts were made to study the age distribution along the altitudinal gradient. The species limit was observed at 4090 m asl. The age structure differed along the altitudinal gradient with multi age cohorts below the treeline and younger cohorts above the treeline. Results show that this species is migrating up at a rate of 24.7m per decade. (author)

  2. HPTLC detection of altitudinal variation of the potential antivenin stigmasterol in different populations of the tropical ethnic antidote Rauvolfia serpentina.

    Science.gov (United States)

    Dey, Abhijit; Pandey, Devendra Kumar

    2014-09-01

    To determine the altitudinal variation of stigmasterol, a potential antivenin, in roots from seven populations of Rauvolfia serpentina (L). Benth. ex Kurz. (Apocynaceae) (R. serpentina), an important herb found in Indian subcontinent which has long been used in the treatment of snakebite, blood pressure and schizophrenia. Altitudinal variation of stigmasterol content in R. serpentina roots was analyzed by high performance thin layer chromatography. Chromatography was performed on silica gel 60 F254 thin layer chromatography plates with benzene-acetone 86:14 (v/v) as mobile phase. Densitometric analysis was done at λ=366 nm after derivatization with vanillin-10% (v/v) sulphuric acid alcohol reagent. The method was validated for precision and recovery. The present experiment demonstrates a simple, rapid, precise and sensitive high performance thin layer chromatography protocol for qualitative and quantitative determination of stigmasterol from different populations of R. serpentina. Results demonstrated that in root samples stigmasterol was present at Rf value of 0.44. This investigation demonstrates that stigmasterol content in R. serpentina roots varies in different altitudes. Popular ethnomedicinal use of this herb against snakebite may be contributed by the occurrence of stigmasterol in its roots. Copyright © 2014 Hainan Medical College. Published by Elsevier B.V. All rights reserved.

  3. UREDINALES (RUST FUNGI BIOTA OF THE PARQUE NACIONAL DO ITATIAIA, BRAZIL: AN ANALYSIS OF COMPOSITION, SPECIES DIVERSITY AND ALTITUDINAL DISTRIBUTION

    Directory of Open Access Journals (Sweden)

    Salazar Yepes Mauricio

    2013-07-01

    Full Text Available The present study analyzed the composition, species diversity, and altitudinal distributionof rust fungi (Uredinales collected in the Parque Nacional do Itatiaia, Brazil.Results were compared with other Atlantic Forest locations, the São Paulo Cerradoand some other tropical regions. The Uredinales collections were made over thecourse of two years, covering the states of Rio de Janeiro and Minas Gerais, from500 to 2600m above the sea level. The Uredinales Biota is composed of 38 genera(32 teleomorphs and 6 anamorphs and 207 species, 178 of which were teleomorphicand 29 anamorphic. The genera Puccinia, Uromyces and Phakopsora contained ahigh number of species (58% combined. A hundred and ninety-two hosts belongingto 63 botanical families were recorded. The rust/host ratio for ten of the richestfamilies in number of species was 1:8. A high similarity (50% was found betweentwo altitudinal ranges. The results provide a strong additional argument for the needto preserve and continue studies in such areas

  4. Diversity and altitudinal distribution of Chrysomelidae (Coleoptera in Peregrina Canyon, Tamaulipas, Mexico

    Directory of Open Access Journals (Sweden)

    Uriel Jeshua Sánchez-Reyes

    2014-06-01

    species assemblages of Chrysomelidae. The highest abundance was obtained during the late dry season, whereas diversity indices were highest during the early wet season. The present work represents the first report of the altitudinal variation in richness, abundance, and diversity of Chrysomelidae in Mexico. These results highlight the importance of conservation of this heterogeneous habitat and establish baseline data for Chrysomelidae richness and diversity for the region.

  5. Anatomía foliar y del pecíolo de cuatro especies de Lupinus (Fabaceae Foliar and petiole anatomy of four species of Lupinus (Fabaceae

    Directory of Open Access Journals (Sweden)

    Juan Francisco Zamora-Natera

    2012-09-01

    Full Text Available Se describe y compara la anatomía foliar y del pecíolo de 4 especies del género Lupinus (L. aschenbornii S.Schauer, L. exaltatus Zucc., L. montanus Kunth y L. reflexus Rose que se distribuyen en un gradiente altitudinal en el Parque Nacional Nevado de Colima. Las hojas se fijaron en campo y se procesaron mediante la técnica de inclusión en parafina. Parte de las láminas se deshidrataron para caracterizar la superficie foliar por medio del microscopio electrónico de barrido. Las especies comparten la epidermis papilosa de paredes anticlinales con diferentes grados de ondulación, estomas anomocíticos, tricomas simples lineares y mesofilo bifacial. Los folíolos de L. montanus son glabros en la superficie abaxial, las estrías cuticulares sobre las células localizadas en la base de los tricomas es un rasgo característico de L. montanus y de L. reflexus. Las diferencias encontradas en espesor de la lámina y del mesofilo así como la abundancia de ceras epicuticulares pueden estar influenciadas por el ambiente. Distintivamente, el número y distribución de haces vasculares en los pecíolos difieren entre las 4 especies y podrían ser de utilidad para diferenciarlas si estos resultados se confirman al estudiar un mayor número de especies de Lupinus.The aims of this study were to describe and compare the foliar and petiole anatomy of 4 species of Lupinus (L. aschenbornii S.Schauer, L. exaltatus Zucc., L. montanus Kunth, and L. reflexus Rose distributed in an elevation gradient at Parque Nacional Nevado de Colima. Leaves were fixed in the field and prepared using the paraffin embedding technique. In addition, part of the blades was dehydrated to describe leaf surface through the scanning electron microscope. The 4 species shared a papillose epidermis with undulated anticlinal walls in different degrees, stomata anomocytic, simple unicellular trichomes, and bifacial mesophyll. Leaflets of L. montanus are glabrous on the abaxial surface

  6. Altitudinal distribution and advertisement call of Colostethus latinasus (Amphibia: Dendrobatidae), endemic species from eastern Panama and type species of Colostethus , with a molecular assessment of similar sympatric species.

    Science.gov (United States)

    Ibáñez, Roberto D; Griffith, Edgardo J; Lips, Karen R; Crawford, Andrew J

    2017-04-12

    We conducted a molecular assessment of Colostethus-like frogs along an elevational gradient in the Serranía de Pirre, above Santa Cruz de Cana, eastern Panama, aiming to establish their species identity and to determine the altitudinal distribution of C. latinasus. Our findings confirm the view of C. latinasus as an endemic species restricted to the highlands of this mountain range, i.e., 1350-1475 m.a.s.l., considered to be type locality of this species. We described the advertisement call of C. latinasus that consists of a series of 4-18 single, short and relatively loud "peep"-like notes given in rapid succession, and its spectral and temporal features were compared with calls of congeneric species. For the first time, DNA sequences from C. latinasus were obtained, since previously reported sequences were based on misidentified specimens. This is particularly important because C. latinasus is the type species of Colostethus, a genus considered paraphyletic according to recent phylogenetic analyses based on molecular data.

  7. [Altitudinal distribution, richness and composition of bird assemblages in a mountainous region in Southern Nayarit, Mexico].

    Science.gov (United States)

    Jaime-Escalante, Nidia Gissell; Figueroa-Esquivel, Elsa Margarita; Villaseñor Gómez, José Fernando; Jacobo-Sapien, Edwin Alberto; Puebla-Olivares, Fernando

    2016-12-01

    Elevation gradient studies have strengthened the evaluation of changes in richness and composition of bird assemblages. They also provide information on environmental variables that determine bird distribution, and the variables that define their population structure. Our aim was to describe their variation through an elevational cline in Southern Nayarit, Mexico. To analyze the behavior of richness across the gradient, we gathered information through point counts in nine elevational intervals (300 m from each other) from sea level to 2 700 m of elevation. With a standardized sampling effort, we produced rarefaction curves and analyzed changes in species composition by hierarchical classification using the TWINSPAN technique. In order to identify variables associated with richness changes, we examined the effect of precipitation and habitat structure via regression trees. An analysis of nonmetric multidimensional scaling (NMDS) was implemented with the purpose to determine if the changes in composition correspond to changes in vegetation types. Species richness varied significantly across the gradient: high in the lower parts of the gradient, reached its peak in the middle, and decreased monotonically with elevation. Species responded to changes in the cline and were grouped in three elevational zones. Analyses suggest that changes in richness and species composition are influenced by vegetation, its structure and precipitation regime, as well as various aspects related to habitat features and disturbance. These aspects should be taken into account in order to design appropriate strategies for the conservation of the birds of Nayarit.

  8. Travelling gradient thermocouple calibration

    International Nuclear Information System (INIS)

    Broomfield, G.H.

    1975-01-01

    A short discussion of the origins of the thermocouple EMF is used to re-introduce the idea that the Peltier and Thompson effects are indistinguishable from one another. Thermocouples may be viewed as devices which generate an EMF at junctions or as integrators of EMF's developed in thermal gradients. The thermal gradient view is considered the more appropriate, because of its better accord with theory and behaviour, the correct approach to calibration, and investigation of service effects is immediately obvious. Inhomogeneities arise in thermocouples during manufacture and in service. The results of travelling gradient measurements are used to show that such effects are revealed with a resolution which depends on the length of the gradient although they may be masked during simple immersion calibration. Proposed tests on thermocouples irradiated in a nuclear reactor are discussed

  9. Soil , phyto and zoocenosis characteristics along an elevational gradient in the Alps (NW Italy)

    Science.gov (United States)

    Caimi, Angelo; Freppaz, Michele; Filippa, Gianluca; Buffa, Giorgio; Rivella, Enrico; Griselli, Bona; Parodi, Alessandra; Zanini, Ermanno

    2010-05-01

    values suggest an heterogeneous environment where parameters such as light and temperature display sharp changes along the elevation gradient and/or as function of morphological features at single sites. Consequently, the vegetation physiognomy, abundance and richness change as a function of altitude and morphology. According to mesofauna communities we observed a reduction of "adapted" organisms along the altitudinal gradient. In both transects euedaphic biological forms were more abundant at the altitudinal range, between 1600-2000 m ASL.

  10. Quaternion Gradient and Hessian

    OpenAIRE

    Xu, Dongpo; Mandic, Danilo P.

    2014-01-01

    The optimization of real scalar functions of quaternion variables, such as the mean square error or array output power, underpins many practical applications. Solutions typically require the calculation of the gradient and Hessian. However, real functions of quaternion variables are essentially nonanalytic, which are prohibitive to the development of quaternion-valued learning systems. To address this issue, we propose new definitions of quaternion gradient and Hessian, based on the novel gen...

  11. Gradient Alloy for Optical Packaging

    Data.gov (United States)

    National Aeronautics and Space Administration — Advances in additive manufacturing, such as Laser Engineered Net Shaping (LENS), enables the fabrication of compositionally gradient microstructures, i.e. gradient...

  12. Potential of Gdgts as Temperature Proxies Along Altitudinal Transects in East Africa

    Science.gov (United States)

    Coffinet, Sarah; Huguet, Arnaud; Omuombo, Christine; Williamson, David; Fosse, Céline; Anquetil, Christine; Derenne, Sylvie

    2014-05-01

    Glycerol dialkyl glycerol tetraethers (GDGTs) are lipids of high molecular weight and include the isoprenoid GDGTs (iGDGTs) produced by Archaea and the branched GDGTs (brGDGTs) produced by unknown bacteria. Several indices were developed to describe the relationship between GDGT distribution and environmental parameters: the TEX86 (tetraether index of tetraethers consisting of 86 carbons), based on the relative abundances of iGDGTs in sediments, and the MBT (methylation index of branched tetraethers) and CBT (cyclisation ratio of branched tetraethers), based on the relative abundance of brGDGTs in soils. The TEX86 was shown to correlate well with water surface temperature, and the MBT and CBT with mean annual air temperature (MAAT) and soil pH. The GDGTs are increasingly used as temperature proxies. In this study, 41 surface soils were sampled along two altitudinal transects, from 500 to 2800 meters in Mount Rungwe (South western, Tanzania) and from 1897 to 3268 meters in Mount Kenya (Central Kenya). MAAT was reconstructed along the two transects using the MBT/CBT proxies. A linear correlation between the MBT/CBT-derived temperatures and the altitude (R2=0.83) was obtained by combining results of the two transects. The reconstructed temperature lapse rate (0.5 ° C/100 m) was consistent with the one determined from temperature measurements at six altitudes. These results show that the MBT/CBT is a suitable and robust temperature proxy in East Africa. In Mt. Rungwe soil samples, the TEX86 index, which was mainly used to reconstruct water surface temperatures until now, was found to vary linearly with altitude (R2=0.50). Such a relationship between TEX86 and altitude in organic soils has also been recently noticed in Mt. Xiangpi, China (Liu et al., 2013; R2=0.68). The adiabatic cooling of air with altitude could explain the TEX86 variation with altitude. If such a relationship is confirmed, the use of the TEX86 as a temperature proxy could be extended to soil

  13. Distribution of PCBs and PBDEs in soils along the altitudinal gradients of Balang Mountain, the east edge of the Tibetan Plateau

    International Nuclear Information System (INIS)

    Zheng Xiaoyan; Liu Xiande; Jiang Guibin; Wang Yawei; Zhang Qinghua; Cai Yaqi; Cong Zhiyuan

    2012-01-01

    Surface soils were collected in Balang Mountain to explore the environmental process of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) during air transport. The average concentrations of ∑ 25 PCBs and ∑ 13 PBDEs in soils were 163 pg/g and 26 pg/g, respectively. The significant correlations between the concentrations of pollutants and total organic carbon (TOC) indicated the importance of TOC in accumulation potential of POPs. The slopes from fitted curves of PCBs were highly related with logK oa , demonstrating that TOC dominates the soil-air exchange of PCBs. The TOC-normalized concentrations of contaminants in samples from below-treeline were higher than those from alpine meadow, probably due to the forest filter effect. The increasing trends of the concentrations with altitude from the alpine meadow samples, could be attributed to the mountain cold-trapping effect. And the weak cold-trapping effect of POPs might be due to the less precipitation in 2008 when comparing with those in 2006. - Highlights: ► Total organic carbon plays an important role in accumulation potential of POPs. ► Forest filter effect might enhance the chemical levels for below-treeline soils. ► Precipitation was the key factor of mountain cold-trapping effect in this area. ► The reduction of precipitation might lead to a weak cold-trapping effect of POPs. ► Higher level of BDE-153 at Site 7 probably resulted from the human disturbance. - The concentrations of POPs in soils in the east edge of the Tibetan Plateau were mainly influenced by forest filter effect and mountain cold-trapping.

  14. To heat or to save time? Thermoregulation in the lizard Zootoca vivipara (Squamata: Lacertidae) in different thermal environments along an altitudinal gradient

    Czech Academy of Sciences Publication Activity Database

    Gvoždík, Lumír

    2002-01-01

    Roč. 80, č. 3 (2002), s. 479-492 ISSN 0008-4301 Institutional research plan: CEZ:AV0Z6093917 Keywords : common lizard * body temperature * behavioral thermoregulation Subject RIV: EG - Zoology Impact factor: 1.175, year: 2002

  15. Spatial Distribution of Bactrocera dorsalis and Thaumatotibia leucotreta in Smallholder Avocado Orchards along Altitudinal Gradient of Taita Hills and Mount Kilimanjaro

    Directory of Open Access Journals (Sweden)

    James J. Odanga

    2018-06-01

    Full Text Available Avocado (Persea americana fruits are an important source of income and a nutritious food for small-scale growers and other stakeholders involved in farming along the Afrotropical highlands of Taita Hills and Mount Kilimanjaro in Kenya and Tanzania, respectively. Avocado fruits are infested by several insect pests, namely the Asian invasive fruit fly, Bactrocera dorsalis (Hendel (Diptera: Tephritidae, and the false codling moth, Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae. However, there is inadequate information on the distribution patterns of these pests in small-scale avocado cropping systems in the East African highlands. This study was initiated to generate a spatial distribution map of B. dorsalis and T. leucotreta in avocado orchards at Taita Hills and Mount Kilimanjaro in Kenya and Tanzania, respectively. The two pests were monitored by using their respective parapheromone lures for two years between August 2012 and July 2014. Fruit damage was assessed by computing the proportion of infested fruits for B. dorsalis, whereas the damage score was used for T. leucotreta. Our results indicated that the mean number of B. dorsalis per trap per day differed significantly across elevation, being highest in lowland zone for both Taita Hills (15.90 and Mount Kilimanjaro (24.45. Similarly, the percentage infestation of ground collected fruits by B. dorsalis varied with altitude, being lowest at highlands above 1500 m.a.s.l. (0.66% and 0.83% for Taita Hills and Mount Kilimanjaro, respectively. Conversely, the mean number of T. leucotreta did not vary with altitude in either study area. However, the damage score for T. leucotreta infestation was significantly lower in the highlands of both transects (7.0% and11.1% for Taita Hills and Mount Kilimanjaro, respectively. These findings describe spatial trends that are important in formulating strategies aimed at suppressing the populations of B. dorsalis and T. leucotreta in East African avocado cropping systems.

  16. VARIACIÓN ALTITUDINAL ENTRE ESPECIES Y PROCEDENCIAS DE Pinus pseudostrobus, P. devoniana y P. leiophylla. ENSAYO DE VIVERO

    Directory of Open Access Journals (Sweden)

    Dante Castellanos-Acuña

    2013-01-01

    Full Text Available Los bosques de pino-encino de la comunidad de Nuevo San Juan, Michoacán, están dominados por Pinus pseudostrobus, P. devoniana y P. leiophylla. Los patrones de variación genética de estas especies no se conocen lo suficiente, particularmente los de P. leiophylla, lo cual limita la creación de lineamientos para el movimiento de semillas y plántulas para reforestación y su adaptación al cambio climático. Las especies se recolectaron en cuatro o cinco procedencias a lo largo de un transecto altitudinal (1,650 a 2,500 m para el establecimiento de un ensayo en vivero, con el objetivo de cuantificar la variación genética entre y dentro de las especies. La altura de la planta (tres y cinco meses de edad fue significativamente diferente (P < 0.0001 entre especies. Entre procedencias hubo diferencias significativas para P. devoniana (P < 0.0001 y P. leiophylla (P = 0.0352. La especie P. devoniana mostró un pronunciado patrón de crecimiento asociado con la altitud de origen, donde las plantas con mayor crecimiento procedían de una menor altitud. Las poblaciones de P. leiophylla fueron diferentes sólo a los tres meses de edad, sin un patrón altitudinal estadísticamente significativo. No se encontraron diferencias significativas entre poblaciones de P. pseudostrobus.

  17. Phyllostomidae assemblage (Chiroptera: Mammalia in altitudinal forests at the Parque Estadual do Ibitipoca, Southeast of Minas Gerais, Brazil

    Directory of Open Access Journals (Sweden)

    Rodrigo M. Mello

    Full Text Available ABSTRACT Many studies have demonstrated the ecological relevance and great biodiversity of bats in Brazil. However, mountainous areas have been disproportionately less sampled, mainly in the Southeast. The aim of this study was to identify and compare the richness and diversity of Phyllostomidae, the most diverse bat family, in different forest types in Parque Estadual do Ibitipoca, trying to understand the causes of possible differences. The Parque Estadual do Ibitipoca is inserted in the Serra da Mantiqueira's domain, in an Atlantic Forest region known as "Zona da Mata", state of Minas Gerais, with an altitudinal range between 1200-1784 meters. The study was conducted in two forest types, classified as "Nanofloresta Nebular" and "Floresta Nebular", whose respective data on richness and diversity were compared. The bats were captured with 8-10 mist nets for 14 months (April 2011 to May 2012 and four nights per month totaling 62,171.25 m2h of capture effort. A total of 392 captures (12 species belonging to the Phyllostomidae family were obtained. The most abundant species were Sturnira lilium (59.9%, Platyrrhinus lineatus (11.3%, Artibeus lituratus (8.7% and Carollia perspicillata (7.6%. The two sampled areas presented differences in bat richness, diversity and species composition, and this difference was predominantly influenced by S. lilium. It is likely that the observed difference in the assembly of bats between the two study sites depends on the variation in floristic composition. The records of A. lituratus and P. lineatus in a few months of the year and close to Ficus mexiae bearing ripe fruits suggests that at least these species move to the park for a few periods of the year in search of food resources, possibly moving through the altitudinal landscapes.

  18. High Gradient Accelerator Research

    International Nuclear Information System (INIS)

    Temkin, Richard

    2016-01-01

    The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave cold test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.

  19. Uniform gradient expansions

    CERN Document Server

    Giovannini, Massimo

    2015-01-01

    Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  20. High gradient superconducting quadrupoles

    International Nuclear Information System (INIS)

    Lundy, R.A.; Brown, B.C.; Carson, J.A.; Fisk, H.E.; Hanft, R.H.; Mantsch, P.M.; McInturff, A.D.; Remsbottom, R.H.

    1987-07-01

    Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed

  1. Manipulating the Gradient

    Science.gov (United States)

    Gaze, Eric C.

    2005-01-01

    We introduce a cooperative learning, group lab for a Calculus III course to facilitate comprehension of the gradient vector and directional derivative concepts. The lab is a hands-on experience allowing students to manipulate a tangent plane and empirically measure the effect of partial derivatives on the direction of optimal ascent. (Contains 7…

  2. The covariance between genetic and environmental influences across ecological gradients: reassessing the evolutionary significance of countergradient and cogradient variation.

    Science.gov (United States)

    Conover, David O; Duffy, Tara A; Hice, Lyndie A

    2009-06-01

    Patterns of phenotypic change across environmental gradients (e.g., latitude, altitude) have long captivated the interest of evolutionary ecologists. The pattern and magnitude of phenotypic change is determined by the covariance between genetic and environmental influences across a gradient. Cogradient variation (CoGV) occurs when covariance is positive: that is, genetic and environmental influences on phenotypic expression are aligned and their joint influence accentuates the change in mean trait value across the gradient. Conversely, countergradient variation (CnGV) occurs when covariance is negative: that is, genetic and environmental influences on phenotypes oppose one another, thereby diminishing the change in mean trait expression across the gradient. CnGV has so far been found in at least 60 species, with most examples coming from fishes, amphibians, and insects across latitudinal or altitudinal gradients. Traits that display CnGV most often involve metabolic compensation, that is, the elevation of various physiological rates processes (development, growth, feeding, metabolism, activity) to counteract the dampening effect of reduced temperature, growing season length, or food supply. Far fewer examples of CoGV have been identified (11 species), and these most often involve morphological characters. Increased knowledge of spatial covariance patterns has furthered our understanding of Bergmann size clines, phenotypic plasticity, species range limits, tradeoffs in juvenile growth rate, and the design of conservation strategies for wild species. Moreover, temporal CnGV explains some cases of an apparent lack of phenotypic response to directional selection and provides a framework for predicting evolutionary responses to climate change.

  3. Limitaciones del IMC como indicador exclusivo de estado nutricional

    Directory of Open Access Journals (Sweden)

    Moreno Romero, Susana

    2007-01-01

    Full Text Available El presente trabajo tiene como objetivo determinar el potencial diagnóstico y las limitaciones del uso del Índice de Masa Corporal como único indicador del estado nutricional. Para ello se analizó una muestra constituida por 2155 sujetos de ambos sexos, con edades comprendidas entre los 6 y 18 años y pertenecientes a tres poblaciones jujeñas que difieren en ubicación altitudinal y nivel socieconómico (NSE: 1. Susques, localidad rural situada a 3675 m.s.n.m; 2. Alto Comedero, barrio periférico de San Salvador de Jujuy (1250 m.s.n.m. de NSE bajo; y 3. José Hernández, muestra representativa del estrato SE elevado de la misma capital. Se tomaron las medidas directas de talla, peso, perímetro braquial y pliegues de grasa subcutánea tricipital y subescapular, entre otras. A partir de éstas, se calculó el IMC y las áreas tisulares del brazo. Se establecieron las categorías nutricionales en función de los percentilos establecidos por el NHANES I y II para la talla, IMC, área magra y grasa del brazo y pliegues tricipital y subescapular. Al comparar los resultados obtenidos para cada variable se comprueba como el uso exclusivo del IMC enmascara importantes patologías nutricionales, tanto por defecto como por exceso.

  4. Efectos del cambio climático sobre especies de plantas vasculares del sur de los Andes Centrales: un estudio en el noroeste de Argentina (NOA)

    OpenAIRE

    Godoy Bürki, Ana Carolina

    2017-01-01

    La región de los Andes Tropicales es considerada como una región muy vulnerable al cambio climático porque presenta una alta diversidad y endemismo y porque posee una gran variabilidad altitudinal. Si bien se ha efectuado un gran número de predicciones sobre los cambios que ocurrirán en el clima, pocos estudios evaluaron el impacto que éste tendrá sobre las distribuciones de las especies. En este estudio se estima el efecto del cambio climático sobre la distribución y la conservación de espec...

  5. FAUNA ANFIBIA DEL VALLE DE SIBUNDOY, PUTUMAYO-COLOMBIA

    Directory of Open Access Journals (Sweden)

    MUESES-CISNEROS JONH JAIRO

    2005-12-01

    Full Text Available La fauna Amphibia del Valle de Sibundoy consta de 32 especies agrupadas en dos órdenes, cinco familias y siete géneros. De éstas, cinco son especies nuevas cuya descripción se encuentra en proceso. Se amplía el límite altitudinal de otras siete y se presentan tres más para ser incluidas en la lista de anfibios de Colombia. A pesar de que en el lugar se han realizado colectas herpetológicas desde finales de los años sesenta, este estudio es el primero que se realiza en el Putumayo (uno de los departamentos menos muestreados del país.

  6. Abiotic alterations caused by forest fragmentation affect tree regeneration: a shade and drought tolerance gradient in the remnants of Coastal Maulino Forest Alteraciones abióticas causadas por la fragmentación del bosque afectan la regeneración arbórea: un gradiente de tolerancia a la sombra y la sequía en los remanentes del Bosque Maulino Costero

    Directory of Open Access Journals (Sweden)

    PABLO C GUERRERO

    2009-01-01

    by regeneration niche attributes for implementing conservation actions and ecological restoration.La regeneración en plantas está determinada por las diferencias de luz y humedad del suelo entre hábitats, ambas variables son modificadas por la fragmentación de bosques a gran escala. Varios estudios consideran esas alteraciones como parte del mecanismo involucrado en el cambio comunitario en bosques tropicales. Sin embargo, en bosques mediterráneos y deciduos esa tendencia podría ser más severa, debido a que las plantas presentan un "trade off" entre la tolerancia a la sombra y a la sequía. Nuestro estudio fue realizado en el Bosque Maulino Costero: Reserva Nacional Los Queules (RNLQ y fragmentos aledaños de bosque. Hipotetizamos que Aristotelia chilensis (sombra intolerante pero tolerante a la sequía debería aumentar su regeneración en fragmentos pequeños de bosque, como consecuencia del cambio en la idoneidad del habitat (i.e. más luminoso y seco, mientras que, Cryptocarya alba (sombra tolerante pero sequía intolerante debería reducir su regeneración en fragmentos pequeños de bosque. Nosotros además esperamos que Nothofagus glauca y N. obliqua, ambas con tolerancias a la sombra y a la sequía intermedias entre A. chilensis y C. alba, deberían responder en menor medida a la fragmentación del bosque. En este estudio utilizamos dos evaluaciones: (i la abundancia de plántulas y juveniles a través de observaciones de campo y (ii la germinación y establecimiento de plántulas vía un experimento de campo. Los patrones de regeneración natural de C. alba indican una reducción en la regeneración dentro de los fragmentos pequeños de bosque comparado con la RNLQ, a pesar de que en el experimento de campo, la proporción de semillas germinadas, de plántulas establecidas y reclutadas no variaron entre hábitats. Por el contrario, la regeneración de A. chilensis y de N. glauca fueron favorecidas por la fragmentación del bosque, con un aumento en las

  7. Leaf morphology and phenology of Beech (Fagus sylvatica L.) are linked to environmental conditions depending on the altitudinal origin

    Science.gov (United States)

    Capdevielle-Vargas, Renee; Schuster, Christina; Estrella, Nicole; Menzel, Annette

    2014-05-01

    differences in SLA were found among the altitudinal levels in any of the transects, significant differences were found in biomass among the two highest sites of the two transects. The length of the lamina differed significantly between 900 to 1100-1400 m.a.s.l. in the south facing transect, while in the north facing transect the lamina width showed significant differences between the highest and the lower sites. A higher percentage of germination of seeds originating from higher altitudinal sites may points to a developed sensitivity to environmental changes and a rapid and more favorable response. Our results suggest, contrary to what has been reported, (leaf size differentiation among altitudinal sites under natural conditions), that the altitude of origin doesn't have an overriding impact on leaf morphological responses when growing under the same conditions, indicating that leaf morphology and phenology may have an adaptive significance linked to climate.

  8. Bigravity from gradient expansion

    International Nuclear Information System (INIS)

    Yamashita, Yasuho; Tanaka, Takahiro

    2016-01-01

    We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takes the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.

  9. An altitudinal comparison of caterpillar (Lepidoptera) assemblages on Ficus trees in Papua New Guinea

    Czech Academy of Sciences Publication Activity Database

    Novotný, Vojtěch; Miller, S. E.; Basset, Y.; Čížek, Lukáš; Darrow, K.; Kaupa, B.; Kua, J.; Weiblen, G. D.

    2005-01-01

    Roč. 32, č. 8 (2005), s. 1303-1314 ISSN 0305-0270 R&D Projects: GA AV ČR(CZ) IAA6007106; GA AV ČR(CZ) KSK6005114; GA ČR(CZ) GA206/04/0725; GA ČR(CZ) GD206/03/H034; GA MŠk(CZ) ME 646 Grant - others:US National Science Foundation(US) DEB-94-07297; US National Science Foundation(US) DEB-96-28840; US National Science Foundation(US) DEB-97-07928; US National Science Foundation(US) DEB-02-11591; National Geographic Society(US) 7659-04 Institutional research plan: CEZ:AV0Z50070508 Keywords : beta diversity * cryptic species * elevation gradient Subject RIV: EH - Ecology, Behaviour Impact factor: 2.804, year: 2005

  10. Gradient-Index Optics

    Science.gov (United States)

    2010-03-31

    nonimaging design capabilities to incorporate 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 12-04-2011 13. SUPPLEMENTARY NOTES The views, opinions...Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS Imaging Optics, Nonimaging Optics, Gradient Index Optics, Camera, Concentrator...imaging and nonimaging design capabilities to incorporate manufacturable GRIN lenses can provide imaging lens systems that are compact and

  11. Predicted altitudinal shifts and reduced spatial distribution of Leishmania infantum vector species under climate change scenarios in Colombia.

    Science.gov (United States)

    González, Camila; Paz, Andrea; Ferro, Cristina

    2014-01-01

    Visceral leishmaniasis (VL) is caused by the trypanosomatid parasite Leishmania infantum (=Leishmania chagasi), and is epidemiologically relevant due to its wide geographic distribution, the number of annual cases reported and the increase in its co-infection with HIV. Two vector species have been incriminated in the Americas: Lutzomyia longipalpis and Lutzomyia evansi. In Colombia, L. longipalpis is distributed along the Magdalena River Valley while L. evansi is only found in the northern part of the Country. Regarding the epidemiology of the disease, in Colombia the incidence of VL has decreased over the last few years without any intervention being implemented. Additionally, changes in transmission cycles have been reported with urban transmission occurring in the Caribbean Coast. In Europe and North America climate change seems to be driving a latitudinal shift of leishmaniasis transmission. Here, we explored the spatial distribution of the two known vector species of L. infantum in Colombia and projected its future distribution into climate change scenarios to establish the expansion potential of the disease. An updated database including L. longipalpis and L. evansi collection records from Colombia was compiled. Ecological niche models were performed for each species using the Maxent software and 13 Worldclim bioclimatic coverages. Projections were made for the pessimistic CSIRO A2 scenario, which predicts the higher increase in temperature due to non-emission reduction, and the optimistic Hadley B2 Scenario predicting the minimum increase in temperature. The database contained 23 records for L. evansi and 39 records for L. longipalpis, distributed along the Magdalena River Valley and the Caribbean Coast, where the potential distribution areas of both species were also predicted by Maxent. Climate change projections showed a general overall reduction in the spatial distribution of the two vector species, promoting a shift in altitudinal distribution for L

  12. [Altitudinal patterns of species richness and species range size of vascular plants in Xiaolong- shan Reserve of Qinling Mountain: a test of Rapoport' s rule].

    Science.gov (United States)

    Zheng, Zhi; Gong, Da-Jie; Sun, Cheng-Xiang; Li, Xiao-Jun; Li, Wan-Jiang

    2014-09-01

    Altitudinal patterns of species richness and species range size and their underlying mechanisms have long been a key topic in biogeography and biodiversity research. Rapoport's rule stated that the species richness gradually declined with the increasing altitude, while the species ranges became larger. Using altitude-distribution database from Xiaolongshan Reverse, this study explored the altitudinal patterns of vascular plant species richness and species range in Qinling Xiaolongshan Reserve, and examined the relationships between species richness and their distributional middle points in altitudinal bands for different fauna, taxonomic units and growth forms and tested the Rapoport's rule by using Stevens' method, Pagel's method, mid-point method and cross-species method. The results showed that the species richness of vascular plants except small-range species showed a unimodal pattern along the altitude in Qinling Xiaolongshan Reserve and the highest proportion of small-range species was found at the lower altitudinal bands and at the higher altitudinal bands. Due to different assemblages and examining methods, the relationships between species distributing range sizes and the altitudes were different. Increasing taxonomic units was easier to support Rapoport's rule, which was related to niche differences that the different taxonomic units occupied. The mean species range size of angiosperms showed a unimodal pattern along the altitude, while those of the gymnosperms and pteridophytes were unclearly regular. The mean species range size of the climbers was wider with the increasing altitude, while that of the shrubs which could adapt to different environmental situations was not sensitive to the change of altitude. Pagel's method was easier to support the Rapoport's rule, and then was Steven's method. On the contrary, due to the mid-domain effect, the results of the test by using the mid-point method showed that the mean species range size varied in a unimodal

  13. Altitudinal and chiral signature of persistent organochlorine pesticides in air, soil, and spruce needles (Picea abies) of the Alps.

    Science.gov (United States)

    Shen, Heqing; Henkelmann, Bernhard; Levy, Walkiria; Zsolnay, Adam; Weiss, Peter; Jakobi, Gert; Kirchner, Manfred; Moche, Wolfgang; Braun, Katharina; Schramm, Karl-Werner

    2009-04-01

    The present study investigated the distribution, transportation, and biodegradation of the selected chiral persistent organochlorine pesticides (OCP) in the Alps. In the complex environment, we found the movement and fate of OCP could be defined by many factors. Taking HCE as an example, below the timberline its accumulation from air into SPMD increased with altitude and seasonally changed, but the trends reversed above the timberline. In soil, the tendency of HCE concentrations vs organic materials followed a sigmoid curve, and HCE concentration-altitude correlations are positive in central Alps but negative in southern Alps. The HCE enantiomeric ratios (ERs) in soil correlated to HCE isomers concentrations, the humus pH values, and the sampling site altitudes. HCE shift from humus to mineral soil can also be traced by ERs. The altitudinal and longitudinal trends in needles suggested that alpha-HCH has a more complex movementthan HCE in Alps. In conclusion, altitude conducted condensation, plant canopies, organic material in soil, and geographic specific precipitations may affect OCP distributions and transportation, whereas altitude conducted temperature and soil pH could dictate their fate in the environment.

  14. Differences between Non-arteritic Anterior Ischemic Optic Neuropathy and Open Angle Glaucoma with Altitudinal Visual Field Defect.

    Science.gov (United States)

    Han, Sangyoun; Jung, Jong Jin; Kim, Ungsoo Samuel

    2015-12-01

    To investigate the differences in retinal nerve fiber layer (RNFL) change and optic nerve head parameters between non-arteritic anterior ischemic optic neuropathy (NAION) and open angle glaucoma (OAG) with altitudinal visual field defect. Seventeen NAION patients and 26 OAG patients were enrolled prospectively. The standard visual field indices (mean deviation, pattern standard deviation) were obtained from the Humphrey visual field test and differences between the two groups were analyzed. Cirrus HD-OCT parameters were used, including optic disc head analysis, average RNFL thickness, and RNFL thickness of each quadrant. The mean deviation and pattern standard deviation were not significantly different between the groups. In the affected eye, although the disc area was similar between the two groups (2.00 ± 0.32 and 1.99 ± 0.33 mm(2), p = 0.586), the rim area of the OAG group was smaller than that of the NAION group (1.26 ± 0.56 and 0.61 ± 0.15 mm(2), respectively, p field defects, optic disc head analysis of not only the affected eye, but also the unaffected eye, by using spectral domain optical coherence tomography may be helpful.

  15. Wetting of flat gradient surfaces.

    Science.gov (United States)

    Bormashenko, Edward

    2018-04-01

    Gradient, chemically modified, flat surfaces enable directed transport of droplets. Calculation of apparent contact angles inherent for gradient surfaces is challenging even for atomically flat ones. Wetting of gradient, flat solid surfaces is treated within the variational approach, under which the contact line is free to move along the substrate. Transversality conditions of the variational problem give rise to the generalized Young equation valid for gradient solid surfaces. The apparent (equilibrium) contact angle of a droplet, placed on a gradient surface depends on the radius of the contact line and the values of derivatives of interfacial tensions. The linear approximation of the problem is considered. It is demonstrated that the contact angle hysteresis is inevitable on gradient surfaces. Electrowetting of gradient surfaces is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

  16. Peces del Noroeste del Ecuador

    OpenAIRE

    Barriga, Ramiro

    1994-01-01

    La ictiofauna del occidente del Ecuador es poco conocida. Los peces del noroccidente son diferentes a los del suroccidente del Ecuador. 34 familias y 82 especies fueron colectadas que equivale al 11 % de las especies de peces continentales registradas en el Ecuador. Icteogeográficamente se sabe que la costa ecuatoriana posee dos provincias: la del Pacifico Norte y la del Guayas, se determinó que el límite de las dos provincias es el río Santiago ya que las especies del mencionado río so...

  17. FLORISTIC CHANGES ALONG THE TOPOGRAPHICAL GRADIENT IN MONTANE GRASSLANDS IN MONTI PICENTINI (CAMPANIA, SW ITALY

    Directory of Open Access Journals (Sweden)

    M. CUTINI

    2010-01-01

    Full Text Available Populations of xerotolerant species (Achnatherum calamagrostis, Stipa crassiculmis subsp. picentina, are scattered along a wide altitudinal gradient on slopes at mid- and high elevation in Monti Picentini, a subcoastal mesozoic limestone ridge in Tyrrhenian Southern Italy. Their stands are widespread in grasslands of mostly secondary origin. At lower altitudes these grasslands replace former deciduous forest communities dominated by oaks or beech, while at higher altitudes they reach the summits, where they apparently merge into the remnants of the still partially grazed, zonal climatogenic, grasslands ranging above the local tree-line. Nevertheless primary stands of these grasslands are to be found around the many clusters of highly dynamic sites of the montane and sub-alpine levels, scattered around screes and rocky outcrops of the prevalently dolomitic morphology of the slopes. This virtual continuity of non arboreal communities across more than 1000 metres of the local topographical gradient, where azonal, relic stands of Pinus nigra s.l. are transitional between the grasslands and the surrounding zonal broadleaved forest vegetation, stresses patterns of the coenological changes between Festuco-Brometea and Elyno-Seslerietea along the catena, which suggest fragmentary persistence of a paleozonation.

  18. FLORISTIC CHANGES ALONG THE TOPOGRAPHICAL GRADIENT IN MONTANE GRASSLANDS IN MONTI PICENTINI (CAMPANIA, SW ITALY

    Directory of Open Access Journals (Sweden)

    F. SPADA

    2010-04-01

    Full Text Available Populations of xerotolerant species (Achnatherum calamagrostis, Stipa crassiculmis subsp. picentina, are scattered along a wide altitudinal gradient on slopes at mid- and high elevation in Monti Picentini, a subcoastal mesozoic limestone ridge in Tyrrhenian Southern Italy. Their stands are widespread in grasslands of mostly secondary origin. At lower altitudes these grasslands replace former deciduous forest communities dominated by oaks or beech, while at higher altitudes they reach the summits, where they apparently merge into the remnants of the still partially grazed, zonal climatogenic, grasslands ranging above the local tree-line. Nevertheless primary stands of these grasslands are to be found around the many clusters of highly dynamic sites of the montane and sub-alpine levels, scattered around screes and rocky outcrops of the prevalently dolomitic morphology of the slopes. This virtual continuity of non arboreal communities across more than 1000 metres of the local topographical gradient, where azonal, relic stands of Pinus nigra s.l. are transitional between the grasslands and the surrounding zonal broadleaved forest vegetation, stresses patterns of the coenological changes between Festuco-Brometea and Elyno-Seslerietea along the catena, which suggest fragmentary persistence of a paleozonation.

  19. Seasonal and altitudinal variations in snow algal communities on an Alaskan glacier (Gulkana glacier in the Alaska range)

    International Nuclear Information System (INIS)

    Takeuchi, Nozomu

    2013-01-01

    Snow and ice algae are cold tolerant algae growing on the surface of snow and ice, and they play an important role in the carbon cycles for glaciers and snowfields in the world. Seasonal and altitudinal variations in seven major taxa of algae (green algae and cyanobacteria) were investigated on the Gulkana glacier in Alaska at six different elevations from May to September in 2001. The snow algal communities and their biomasses changed over time and elevation. Snow algae were rarely observed on the glacier in May although air temperature had been above 0 ° C since the middle of the month and surface snow had melted. In June, algae appeared in the lower areas of the glacier, where the ablation ice surface was exposed. In August, the distribution of algae was extended to the upper parts of the glacier as the snow line was elevated. In September, the glacier surface was finally covered with new winter snow, which terminated algal growth in the season. Mean algal biomass of the study sites continuously increased and reached 6.3 × 10 μl m −2 in cell volume or 13 mg carbon m −2 in September. The algal community was dominated by Chlamydomonas nivalis on the snow surface, and by Ancylonema nordenskiöldii and Mesotaenium berggrenii on the ice surface throughout the melting season. Other algae were less abundant and appeared in only a limited area of the glacier. Results in this study suggest that algae on both snow and ice surfaces significantly contribute to the net production of organic carbon on the glacier and substantially affect surface albedo of the snow and ice during the melting season. (letter)

  20. From frugivore to folivore: Altitudinal variations in the diet and feeding ecology of the Bioko Island drill (Mandrillus leucophaeus poensis).

    Science.gov (United States)

    Owens, Jacob R; Honarvar, Shaya; Nessel, Mark; Hearn, Gail W

    2015-12-01

    Variation in the quality and availability of food resources can greatly influence the ecology, behavior, and conservation of wild primates. We studied the influence of altitudinal differences in resource availability on diet in wild drill monkeys (Mandrillus leucophaeus poensis) on Bioko Island, Equatorial Guinea. We compared fecal samples (n = 234) collected across three consecutive dry seasons for drills living in lowland (0-300 m asl) forest with nearby (18 km distance) drills living in montane forest (500-1000 m asl) in the Gran Caldera Southern Highlands Scientific Reserve. Lowland forest drills had a frugivorous diet very similar to that reported from studies on nearby mainland drills (M. l. leucophaeus) and mandrills (M. sphinx), with fruits comprising 90% of their dried fecal samples. However drills living in montane forest had a more folivorous diet, with herbaceous pith, leaves and fungi comprising 74% of their dried fecal samples and fruit becoming a minor component (24%). Furthermore, a dietary preference index indicated that the differences in the proportion of fruit and fibrous vegetation in the diets of lowland compared to montane drills was not simply a result of relative availability. Montane drills were actively consuming a higher mass of the available fruits and fibrous vegetation, a condition reflected in the greater mass of their fresh feces. Our results demonstrate the unexpected flexibility and complexity of dietary choices of this endangered species in two adjacent habitat types, a comparison of considerable importance for many other limited-range species faced with habitat loss and climate change. © 2015 Wiley Periodicals, Inc.

  1. Potential and Limitations of Low-Cost Unmanned Aerial Systems for Monitoring Altitudinal Vegetation Phenology in the Tropics

    Science.gov (United States)

    Silva, T. S. F.; Torres, R. S.; Morellato, P.

    2017-12-01

    Vegetation phenology is a key component of ecosystem function and biogeochemical cycling, and highly susceptible to climatic change. Phenological knowledge in the tropics is limited by lack of monitoring, traditionally done by laborious direct observation. Ground-based digital cameras can automate daily observations, but also offer limited spatial coverage. Imaging by low-cost Unmanned Aerial Systems (UAS) combines the fine resolution of ground-based methods with and unprecedented capability for spatial coverage, but challenges remain in producing color-consistent multitemporal images. We evaluated the applicability of multitemporal UAS imaging to monitor phenology in tropical altitudinal grasslands and forests, answering: 1) Can very-high resolution aerial photography from conventional digital cameras be used to reliably monitor vegetative and reproductive phenology? 2) How is UAS monitoring affected by changes in illumination and by sensor physical limitations? We flew imaging missions monthly from Feb-16 to Feb-17, using a UAS equipped with an RGB Canon SX260 camera. Flights were carried between 10am and 4pm, at 120-150m a.g.l., yielding 5-10cm spatial resolution. To compensate illumination changes caused by time of day, season and cloud cover, calibration was attempted using reference targets and empirical models, as well as color space transformations. For vegetative phenological monitoring, multitemporal response was severely affected by changes in illumination conditions, strongly confounding the phenological signal. These variations could not be adequately corrected through calibration due to sensor limitations. For reproductive phenology, the very-high resolution of the acquired imagery allowed discrimination of individual reproductive structures for some species, and its stark colorimetric differences to vegetative structures allowed detection of the reproductive timing on the HSV color space, despite illumination effects. We conclude that reliable

  2. Gradient Boosting Machines, A Tutorial

    Directory of Open Access Journals (Sweden)

    Alexey eNatekin

    2013-12-01

    Full Text Available Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods. A theoretical information is complemented with many descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. A set of practical examples of gradient boosting applications are presented and comprehensively analyzed.

  3. Gradient waveform synthesis for magnetic propulsion using MRI gradient coils

    International Nuclear Information System (INIS)

    Han, B H; Lee, S Y; Park, S

    2008-01-01

    Navigating an untethered micro device in a living subject is of great interest for both diagnostic and therapeutic applications. Magnetic propulsion of an untethered device carrying a magnetic core in it is one of the promising methods to navigate the device. MRI gradients coils are thought to be suitable for navigating the device since they are capable of magnetic propulsion in any direction while providing magnetic resonance images. For precise navigation of the device, especially in the peripheral region of the gradient coils, the concomitant gradient fields, as well as the linear gradient fields in the main magnetic field direction, should be considered in driving the gradient coils. For simple gradient coil configurations, the Maxwell coil in the z-direction and the Golay coil in the x- and y-directions, we have calculated the magnetic force fields, which are not necessarily the same as the conventional linear gradient fields of MRI. Using the calculated magnetic force fields, we have synthesized gradient waveforms to navigate the device along a desired path

  4. Environmental factors associated with fish assemblage patterns in a high gradient river of the Gulf of Mexico slope Factores ambientales asociados a los patrones en las comunidades de peces en un río de alta pendiente en la vertiente del golfo de México

    Directory of Open Access Journals (Sweden)

    Norman Mercado-Silva

    2012-03-01

    Full Text Available Using multivariate analyses of fish community and environmental data, we explored associations among 13 fish species and 9 ecological guilds and identified ecological gradients that explain patterns in the fish community of the La Antigua River (Veracruz, Mexico. Altitude, distance to ocean, stream width, and water temperature were the most important variables explaining community composition. Sites with high altitudes (> 1 393 m, cold water ( 100 km and less than 5 m wide were dominated by non-native Onchorhynchus mykiss. Many sites exclusively inhabited by native poeciliids were also narrow ( 80 km, 20°C. Because 7 guilds were exclusive to a single species, results from the guild analysis were very similar to species-specific analyses. Higher species and guild diversity were found in wider sites (> 5 m, sites with lower altitudes (Utilizamos datos de la comunidad de peces y de variables ambientales y análisis multivariados para explorar asociaciones entre 13 especies y 9 gremios ecológicos en el río La Antigua (Veracruz, México. Además, identificamos gradientes ecológicos que explicaron los patrones en las comunidades de peces. Las variables más importantes en la determinación de la composición de la comunidad fueron altitud, distancia al océano, ancho de río y temperatura del agua. Los sitios ubicados a gran altitud (> 1 393 m, con aguas frías ( 100 km y menos de 5 m de ancho estuvieron dominados por la especie no nativa Onchorhynchus mykiss. Muchos sitios habitados exclusivamente por poecílidos nativos también fueron angostos ( 20°C y estuvieron a distancias intermedias al océano (> 80 km, 5 m, con menor altitud (< 600 m y más cercanos al océano (< 71 km. Las variables relacionadas con la influencia antropogénica no tuvieron relevancia en la explicación de las tendencias encontradas.

  5. Nueva especie del genero Buenoa Kirkaldy (Hemiptera, notonectidae con clave para especies y notas ecológicas

    Directory of Open Access Journals (Sweden)

    Padilla Gil Dora N.

    1992-06-01

    Full Text Available Se incluyen las especies del género Buenoa encontradas en el Departamento de Cundinamarca con un rango altitudinal entre
    los 1728 y 3000 m.s.n.m. y descipción de la especie Buenoa cucunubensis n. sp., además clave para determinar especies y algunos datos ecológicos.Four species of genus Buenoa are recorded from Cundinamarca province in Colombia, Buenos cucunubensis nov. spec. is
    described. Also included are key to males, data on distribution and ecological information.

  6. Denaturing gradient gel electrophoresis

    International Nuclear Information System (INIS)

    Kocherginskaya, S.A.; Cann, I.K.O.; Mackie, R.I.

    2005-01-01

    It is worthwhile considering that only some 30 species make up the bulk of the bacterial population in human faeces at any one time based on the classical cultivation-based approach. The situation in the rumen is similar. Thus, it is practical to focus on specific groups of interest within the complex community. These may be the predominant or the most active species, specific physiological groups or readily identifiable (genetic) clusters of phylogenetically related organisms. Several 16S rDNA fingerprinting techniques can be invaluable for selecting and monitoring sequences or phylogenetic groups of interest and are described below. Over the past few decades, considerable attention was focussed on the identification of pure cultures of microbes on the basis of genetic polymorphisms of DNA encoding rRNA such as ribotyping, amplified fragment length polymorphism and randomly amplified polymorphic DNA. However, many of these methods require prior cultivation and are less suitable for use in analysis of complex mixed populations although important in describing cultivated microbial diversity in molecular terms. Much less attention was given to molecular characterization of complex communities. In particular, research into diversity and community structure over time has been revolutionized by the advent of molecular fingerprinting techniques for complex communities. Denaturing or temperature gradient gel electrophoresis (DGGE/TGGE) methods have been successfully applied to the analysis of human, pig, cattle, dog and rodent intestinal populations

  7. Ion temperature gradient instability

    International Nuclear Information System (INIS)

    1989-01-01

    Anomalous ion thermal conductivity remains an open physics issue for the present generation of high temperature Tokamaks. It is generally believed to be due to Ion Temperature Gradient Instability (η i mode). However, it has been difficult, if not impossible to identify this instability and study the anomalous transport due to it, directly. Therefore the production and identification of the mode is pursued in the simpler and experimentally convenient configuration of the Columbia Linear Machine (CLM). CLM is a steady state machine which already has all the appropriate parameters, except η i . This parameter is being increased to the appropriate value of the order of 1 by 'feathering' a tungsten screen located between the plasma source and the experimental cell to flatten the density profile and appropriate redesign of heating antennas to steepen the ion temperature profile. Once the instability is produced and identified, a thorough study of the characteristics of the mode can be done via a wide range of variation of all the critical parameters: η i , parallel wavelength, etc

  8. Characterization of gradient control systems

    NARCIS (Netherlands)

    Cortés, Jorge; van der Schaft, Arjan; Crouch, Peter E.

    2005-01-01

    Given a general nonlinear affine control system with outputs and a torsion-free affine connection defined on its state space, we investigate the gradient realization problem: we give necessary and sufficient conditions under which the control system can be written as a gradient control system

  9. Characterization of Gradient Control Systems

    NARCIS (Netherlands)

    Cortés, Jorge; Schaft, Arjan van der; Crouch, Peter E.

    2005-01-01

    Given a general nonlinear affine control system with outputs and a torsion-free affine connection defined on its state space, we investigate the gradient realization problem: we give necessary and sufficient conditions under which the control system can be written as a gradient control system

  10. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, J W

    2010-01-01

    A Sobolev gradient of a real-valued functional on a Hilbert space is a gradient of that functional taken relative to an underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. For discrete versions of partial differential equations, corresponding Sobolev gradients are seen to be vastly more efficient than ordinary gradients. In fact, descent methods with these gradients generally scale linearly with the number of grid points, in sharp contrast with the use of ordinary gradients. Aside from the first edition of this work, this is the only known account of Sobolev gradients in book form. Most of the applications in this book have emerged since the first edition was published some twelve years ago. What remains of the first edition has been extensively revised. There are a number of plots of results from calculations and a sample MatLab code is included for a simple problem. Those working through a fair p...

  11. Electric field gradients in metals

    International Nuclear Information System (INIS)

    Schatz, G.

    1979-01-01

    A review of the recent works on electric field gradient in metals is given. The main emphasis is put on the temperature dependence of the electric field gradient in nonmagnetic metals. Some methods of investigation of this effect using nuclear probes are described. One of them is nuclear accoustic resonance method. (S.B.)

  12. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independent...... tensor elements. Furthermore, in current free regions the magnetic gradient tensor becomes symmetric, further reducing the number of independent elements to five. In that case B is a Laplacian potential field and the gradient tensor can be expressed in series of spherical harmonics. We present properties...... of the magnetic gradient tensor and provide explicit expressions of its elements in terms of spherical harmonics. Finally we discuss the benefit of using gradient measurements for exploring the Earth’s magnetic field from space, in particular the advantage of the various tensor elements for a better determination...

  13. A new species of Anacroneuria Klapálek 1909 (Plecoptera: Perlidae) and notes on the altitudinal distribution of the genus in Costa Rica.

    Science.gov (United States)

    Gutiérrez-Fonseca, Pablo E; Springer, Monika

    2015-12-18

    Anacroneuria is the most widespread genus of Perlidae throughout the Neotropical region and 30 species have been reported from Costa Rica. In this paper, we describe and illustrate a new species from a high elevation cloud forest, A. quetzali sp.n., increasing to 31 the number of described species for Costa Rica. In addition, we examine the altitudinal distribution of Anacroneuria in Costa Rica to determine possible patterns, using the data available on its altitudinal range (10-2700 masl). We divided the elevational range in seven categories, using 500 m intervals. We found that most species (90.3%) are distributed in elevations that range from 500 to 1500 masl, followed by low-elevations (35.5%). Interestingly, despite the fact that Plecoptera are known to inhabit clean, fast flowing water at high elevations, only 16.1% of the species have been found at high elevations in Costa Rica (above 2000 masl). Thus, it seems that most Anacroneuria species are distributed in middle elevations, which are the areas that have a high diversity of freshwater habitats.

  14. Analysis of the altitudinal structure of Storm-enhanced density using Total Electron Content data of space-borne and ground-based GPS receivers

    Directory of Open Access Journals (Sweden)

    Yukari Goi

    2013-11-01

    Full Text Available The altitudinal structure of Storm-enhanced density (SED was studied using the Total Electron Content (TEC data of the GPS receiver on the Gravity Recovery and Climate Experiment (GRACE satellite and the ground-based GPS receivers. The GRACETEC-data are derived from the GPS receiver on the GRACE satellite. A SED is a high-electron density phenomenon that extends from the Equatorial Ionization Anomaly (EIA toward the north-west in the northern hemisphere during geomagnetic disturbed time. TwoSEDs were observed as TEC variations in the GRACE-TEC data and in the ground-GPS TEC data. The ground-GPS TEC data is the TEC data between the ground GPS receiver and the GPS satellites. The SED observed in the GRACE-TEC data appeared at higher latitudes than that in the ground-GPS TEC data. We concluded detected that the altitudinal structure of the SED would be different between at lower than at higher latitudes due to the effects of the eastward E×B drift.

  15. Multi-source analysis reveals latitudinal and altitudinal shifts in range of Ixodes ricinus at its northern distribution limit

    Directory of Open Access Journals (Sweden)

    Kristoffersen Anja B

    2011-05-01

    Full Text Available Abstract Background There is increasing evidence for a latitudinal and altitudinal shift in the distribution range of Ixodes ricinus. The reported incidence of tick-borne disease in humans is on the rise in many European countries and has raised political concern and attracted media attention. It is disputed which factors are responsible for these trends, though many ascribe shifts in distribution range to climate changes. Any possible climate effect would be most easily noticeable close to the tick's geographical distribution limits. In Norway- being the northern limit of this species in Europe- no documentation of changes in range has been published. The objectives of this study were to describe the distribution of I. ricinus in Norway and to evaluate if any range shifts have occurred relative to historical descriptions. Methods Multiple data sources - such as tick-sighting reports from veterinarians, hunters, and the general public - and surveillance of human and animal tick-borne diseases were compared to describe the present distribution of I. ricinus in Norway. Correlation between data sources and visual comparison of maps revealed spatial consistency. In order to identify the main spatial pattern of tick abundance, a principal component analysis (PCA was used to obtain a weighted mean of four data sources. The weighted mean explained 67% of the variation of the data sources covering Norway's 430 municipalities and was used to depict the present distribution of I. ricinus. To evaluate if any geographical range shift has occurred in recent decades, the present distribution was compared to historical data from 1943 and 1983. Results Tick-borne disease and/or observations of I. ricinus was reported in municipalities up to an altitude of 583 metres above sea level (MASL and is now present in coastal municipalities north to approximately 69°N. Conclusion I. ricinus is currently found further north and at higher altitudes than described in

  16. Biodiversidad del complejo de artrópodos asociados al follaje de la vegetación del norte de Chile, II región Biodiversity of the canopy arthropods associated to vegetation of the north of Chile, II region

    Directory of Open Access Journals (Sweden)

    FRANCISCO SAIZ

    2000-12-01

    Full Text Available Uno de los componentes principales de la biodiversidad de los ecosistemas corresponde al complejo plantas hospederas, fitófagos y organismos que regulan a las poblaciones de fitófagos. El conocimiento de este complejo en la región árida de Chile es escaso, situación que motiva la presente investigación. Como hipótesis se plantea que a más favorables condiciones ambientales, a mayor diversidad de plantas hospederas y a mayor contenido de nitrógeno y de agua en los vegetales se sustentará una mayor biodiversidad de fitófagos, los que, a su vez, sustentarán mayor diversidad de depredadores y de parasitoides. El estudio se realizó en la II Región del país, mediante un transecto longitudinal, desde la Costa a la Cordillera de los Andes, el que cruza las siguientes zonas bioclimáticas: Desierto Litoral (DL, Desierto Interior (DI, Tropical Marginal (TM Tropical de Altura (TA, con un gradiente altitudinal de 0 a 4.000 msnm. La colecta de los artrópodos del follaje se hizo mediante la técnica del paraguas entomológico sobre las plantas vegetativamente activas y los formadores de cecidias, minadores y defoliadores por colecta directa de los órganos afectados. En total se colectó e identificó un total de 97 especies vegetales distribuidas en 28 familias. Desde este punto de vista, la zona ecológica más pobre es el DI, destacando DL y TM como las zonas más ricas en vegetación. Sin embargo, existe fuerte aislamiento de la vegetación del DL y una casi total sobreposición de la vegetación del DI con la de la zona TM. En cuanto a familias, la mayor riqueza específica la presenta Asteraceae, seguida por Chenopodiaceae, Solanaceae, Nolanaceae, Fabaceae y Portulacaceae. Asteraceae y Chenopodiaceae destacan, además, por estar presentes en las cuatro zonas ecológicas. Desde el punto de vista nutricional, el contenido foliar de agua y de cenizas de la vegetación varía considerablemente, con valores promedio extremos en el DL y en TA

  17. Murciélagos (Chiroptera: Mammalia del Parque Nacional Yurubí, Venezuela: listado taxonómico y estudio comunitario

    Directory of Open Access Journals (Sweden)

    Mariana Delgado-Jaramillo

    2011-12-01

    Full Text Available Los murciélagos constituyen el grupo de mamíferos más diversificado en la región neotropical y representan un componente clave en la dinámica de muchos ecosistemas terrestres. En este trabajo se describen los resultados de un estudio sobre la quiropterofauna del Parque Nacional Yurubí (ubicado en la zona montañosa del norte de Venezuela, se incluye un listado taxonómico y la caracterización de algunos atributos comunitarios en ambientes predominantemente boscosos. Los datos evaluados fueron obtenidos mediante la revisión de colecciones zoológicas y muestreos diversificados realizados entre febrero y julio del 2009, en un gradiente altitudinal (100-1 500m, que integra a tres unidades ecológicas: bosque semideciduo, bosque siempreverde y selva nublada. Se registraron 64 especies agrupadas en cinco familias, lo que constituye el 63% de los murciélagos conocidos en la Cordillera de la Costa. La familia Phyllostomidae fue dominante (42 especies; 66% del total, seguida por Vespertilionidae, Molossidae, Emballonuridae y Mormoopidae. La comunidad presente a baja elevación fue la más diversificada en términos taxonómicos, mientras que la del piso superior evidenció el menor grado de diversificación. Se identificaron 11 categorías tróficas, con dominancia de los insectívoros en cuanto a la riqueza taxonómica y de los frugívoros en lo que respecta a la abundancia. Nuestros resultados permiten inferir, en un contexto general, que los ecosistemas boscosos del área de estudio muestran un buen estado de conservación, en virtud de la presencia de una proporción relativamente alta de especies pertenecientes a la subfamilia Phyllostominae, cuyos componentes han sido considerados por otros autores como indicadores del grado de conservación de hábitats boscosos primarios, así como la presencia de otras especies con prioridades de conservación. Todos estos aspectos, le confieren a esta área protegida un alto valor proteccionista, en

  18. MODIFIED ARMIJO RULE ON GRADIENT DESCENT AND CONJUGATE GRADIENT

    Directory of Open Access Journals (Sweden)

    ZURAIDAH FITRIAH

    2017-10-01

    Full Text Available Armijo rule is an inexact line search method to determine step size in some descent method to solve unconstrained local optimization. Modified Armijo was introduced to increase the numerical performance of several descent algorithms that applying this method. The basic difference of Armijo and its modified are in existence of a parameter and estimating the parameter that is updated in every iteration. This article is comparing numerical solution and time of computation of gradient descent and conjugate gradient hybrid Gilbert-Nocedal (CGHGN that applying modified Armijo rule. From program implementation in Matlab 6, it's known that gradient descent was applying modified Armijo more effectively than CGHGN from one side: iteration needed to reach some norm of the gradient  (input by the user. The amount of iteration was representing how long the step size of each algorithm in each iteration. In another side, time of computation has the same conclusion.

  19. Combining Step Gradients and Linear Gradients in Density.

    Science.gov (United States)

    Kumar, Ashok A; Walz, Jenna A; Gonidec, Mathieu; Mace, Charles R; Whitesides, George M

    2015-06-16

    Combining aqueous multiphase systems (AMPS) and magnetic levitation (MagLev) provides a method to produce hybrid gradients in apparent density. AMPS—solutions of different polymers, salts, or surfactants that spontaneously separate into immiscible but predominantly aqueous phases—offer thermodynamically stable steps in density that can be tuned by the concentration of solutes. MagLev—the levitation of diamagnetic objects in a paramagnetic fluid within a magnetic field gradient—can be arranged to provide a near-linear gradient in effective density where the height of a levitating object above the surface of the magnet corresponds to its density; the strength of the gradient in effective density can be tuned by the choice of paramagnetic salt and its concentrations and by the strength and gradient in the magnetic field. Including paramagnetic salts (e.g., MnSO4 or MnCl2) in AMPS, and placing them in a magnetic field gradient, enables their use as media for MagLev. The potential to create large steps in density with AMPS allows separations of objects across a range of densities. The gradients produced by MagLev provide resolution over a continuous range of densities. By combining these approaches, mixtures of objects with large differences in density can be separated and analyzed simultaneously. Using MagLev to add an effective gradient in density also enables tuning the range of densities captured at an interface of an AMPS by simply changing the position of the container in the magnetic field. Further, by creating AMPS in which phases have different concentrations of paramagnetic ions, the phases can provide different resolutions in density. These results suggest that combining steps in density with gradients in density can enable new classes of separations based on density.

  20. cultivadas bajo un gradiente de sombra

    Directory of Open Access Journals (Sweden)

    Marco V. Gutiérrez

    2007-01-01

    Full Text Available Se evaluó el crecimiento de 9 especies de palmas cultivadas bajo un gradiente de sombra producido por mallas de polipropileno negro de 40, 50, 60, 70 y 80% de sombra, más un tratamiento de malla aluminizada de 70%, y uno con plantas a pleno sol. Las especies evaluadas fueron Caryota mitis (cola de pez, Chamaedorea costaricana (pacaya, Chamaedorea tepejilote (tepejilote, Dypsis lutescens (areca, Licuala elegans (licuala, Phoenix roebelenii (fénix, Ptychosperma macarthurii (palma macarthur, Roystonea regia (palma real, y Veitchia merrillii (navideña. Se midió la altura de las plantas, la longitud de las hojas maduras, y el número de hojas cosechadas, durante 5 cosechas por 2 años. En general, la altura de las plantas y la longitud de las hojas fueron menores a 0-40% de sombra, se incrementaron a 50-70%, y decrecieron a 80%. C. mitis, C. tepejilote, L. elegans y P. macarthurii, se comportaron como especies obligadas de sombra y no sobrevivieron a pleno sol. C. costaricana y D. lutescens sobrevivieron a plena exposición solar, y su crecimiento alcanzó valores máximos a 50-60%. P. roebelenii, R. regia, y V. merrillii mostraron un crecimiento reducido a 0-40%, pero éste mejoró bajo los demás niveles de sombra a lo largo del gradiente. En general, 1-2 años es un periodo apropiado para el cultivo de palmas de crecimiento rápido (R. regia, Chamedorea spp., D. lutescens en casas de mallas. Palmas de lento crecimiento (L.elegans pueden permanecer 3-5 años en una casa de sombra. Se discute estrategias para el uso de gradientes de sombra en el tiempo y en el espacio, según la utilidad y los requerimientos de las especies, los requisitos establecidos por el mercado, y el ciclo de producción del material vegetal.

  1. Block-conjugate-gradient method

    International Nuclear Information System (INIS)

    McCarthy, J.F.

    1989-01-01

    It is shown that by using the block-conjugate-gradient method several, say s, columns of the inverse Kogut-Susskind fermion matrix can be found simultaneously, in less time than it would take to run the standard conjugate-gradient algorithm s times. The method improves in efficiency relative to the standard conjugate-gradient algorithm as the fermion mass is decreased and as the value of the coupling is pushed to its limit before the finite-size effects become important. Thus it is potentially useful for measuring propagators in large lattice-gauge-theory calculations of the particle spectrum

  2. Spatial gradient tuning in metamaterials

    Science.gov (United States)

    Driscoll, Tom; Goldflam, Michael; Jokerst, Nan; Basov, Dimitri; Smith, David

    2011-03-01

    Gradient Index (GRIN) metamaterials have been used to create devices inspired by, but often surpassing the potential of, conventional GRIN optics. The unit-cell nature of metamaterials presents the opportunity to exert much greater control over spatial gradients than is possible in natural materials. This is true not only during the design phase but also offers the potential for real-time reconfiguration of the metamaterial gradient. This ability fits nicely into the picture of transformation-optics, in which spatial gradients can enable an impressive suite of innovative devices. We discuss methods to exert control over metamaterial response, focusing on our recent demonstrations using Vanadium Dioxide. We give special attention to role of memristance and mem-capacitance observed in Vanadium Dioxide, which simplify the demands of stimuli and addressing, as well as intersecting metamaterials with the field of memory-materials.

  3. Low-gradient aortic stenosis.

    Science.gov (United States)

    Clavel, Marie-Annick; Magne, Julien; Pibarot, Philippe

    2016-09-07

    An important proportion of patients with aortic stenosis (AS) have a 'low-gradient' AS, i.e. a small aortic valve area (AVA gradient (gradient discrepancy raises uncertainty about the actual stenosis severity and thus about the indication for aortic valve replacement (AVR) if the patient has symptoms and/or left ventricular (LV) systolic dysfunction. The most frequent cause of low-gradient (LG) AS is the presence of a low LV outflow state, which may occur with reduced left ventricular ejection fraction (LVEF), i.e. classical low-flow, low-gradient (LF-LG), or preserved LVEF, i.e. paradoxical LF-LG. Furthermore, a substantial proportion of patients with AS may have a normal-flow, low-gradient (NF-LG) AS: i.e. a small AVA-low-gradient combination but with a normal flow. One of the most important clinical challenges in these three categories of patients with LG AS (classical LF-LG, paradoxical LF-LG, and NF-LG) is to differentiate a true-severe AS that generally benefits from AVR vs. a pseudo-severe AS that should be managed conservatively. A low-dose dobutamine stress echocardiography may be used for this purpose in patients with classical LF-LG AS, whereas aortic valve calcium scoring by multi-detector computed tomography is the preferred modality in those with paradoxical LF-LG or NF-LG AS. Although patients with LF-LG severe AS have worse outcomes than those with high-gradient AS following AVR, they nonetheless display an important survival benefit with this intervention. Some studies suggest that transcatheter AVR may be superior to surgical AVR in patients with LF-LG AS. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

  4. Graded/Gradient Porous Biomaterials

    Directory of Open Access Journals (Sweden)

    Xigeng Miao

    2009-12-01

    Full Text Available Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering.

  5. Dose gradient curve: A new tool for evaluating dose gradient.

    Science.gov (United States)

    Sung, KiHoon; Choi, Young Eun

    2018-01-01

    Stereotactic radiotherapy, which delivers an ablative high radiation dose to a target volume for maximum local tumor control, requires a rapid dose fall-off outside the target volume to prevent extensive damage to nearby normal tissue. Currently, there is no tool to comprehensively evaluate the dose gradient near the target volume. We propose the dose gradient curve (DGC) as a new tool to evaluate the quality of a treatment plan with respect to the dose fall-off characteristics. The average distance between two isodose surfaces was represented by the dose gradient index (DGI) estimated by a simple equation using the volume and surface area of isodose levels. The surface area was calculated by mesh generation and surface triangulation. The DGC was defined as a plot of the DGI of each dose interval as a function of the dose. Two types of DGCs, differential and cumulative, were generated. The performance of the DGC was evaluated using stereotactic radiosurgery plans for virtual targets. Over the range of dose distributions, the dose gradient of each dose interval was well-characterized by the DGC in an easily understandable graph format. Significant changes in the DGC were observed reflecting the differences in planning situations and various prescription doses. The DGC is a rational method for visualizing the dose gradient as the average distance between two isodose surfaces; the shorter the distance, the steeper the dose gradient. By combining the DGC with the dose-volume histogram (DVH) in a single plot, the DGC can be utilized to evaluate not only the dose gradient but also the target coverage in routine clinical practice.

  6. Altitudinal changes in composition and structure of mountain-temperate vegetation: a case study from the Western Carpathians

    Czech Academy of Sciences Publication Activity Database

    Doležal, J.; Šrůtek, Miroslav

    2003-01-01

    Roč. 158, - (2003), s. 201-221 ISSN 1385-0237 R&D Projects: GA AV ČR KSK6005114 Keywords : floristic calssification * gradient analysis * tree spatial pattern Subject RIV: EF - Botanics Impact factor: 1.000, year: 2003

  7. Rapid Gradient-Echo Imaging

    Science.gov (United States)

    Hargreaves, Brian

    2012-01-01

    Gradient echo sequences are widely used in magnetic resonance imaging (MRI) for numerous applications ranging from angiography to perfusion to functional MRI. Compared with spin-echo techniques, the very short repetition times of gradient-echo methods enable very rapid 2D and 3D imaging, but also lead to complicated “steady states.” Signal and contrast behavior can be described graphically and mathematically, and depends strongly on the type of spoiling: fully balanced (no spoiling), gradient spoiling, or RF-spoiling. These spoiling options trade off between high signal and pure T1 contrast while the flip angle also affects image contrast in all cases, both of which can be demonstrated theoretically and in image examples. As with spin-echo sequences, magnetization preparation can be added to gradient-echo sequences to alter image contrast. Gradient echo sequences are widely used for numerous applications such as 3D perfusion imaging, functional MRI, cardiac imaging and MR angiography. PMID:23097185

  8. The influence of ALN-Al gradient material gradient index on ballistic performance

    International Nuclear Information System (INIS)

    Wang Youcong; Liu Qiwen; Li Yao; Shen Qiang

    2013-01-01

    Ballistic performance of the gradient material is superior to laminated material, and gradient materials have different gradient types. Using ls-dyna to simulate the ballistic performance of ALN-AL gradient target plates which contain three gradient index (b = 1, b = 0.5, b = 2). Through Hopkinson bar numerical simulation to the target plate materials, we obtained the reflection stress wave and transmission stress wave state of gradient material to get the best gradient index. The internal stress state of gradient material is simulated by amplification processing of the target plate model. When the gradient index b is equal to 1, the gradient target plate is best of all.

  9. Examining relationship between environmental gradients and Lesser Himalyan forest vegetation of Nikyal valley, Azad Jammu and Kashmir using ordination analysis.

    Science.gov (United States)

    Amjad, Muhammad Shoaib; Arshad, Muhammad; Rashid, Audil; Chaudhari, Sunbal Khalil; Malik, Nafeesa Zahid; Fatima, Sammer; Akrim, Faraz

    2014-09-01

    To report the relationship of vegetation structure and environmental gradient and physiochemical properties of soil at Nikyal valley, Azad Jammu and Kashmir . A survey of natural vegetation and soil of Nikyal valley was undertaken. Phytosociological survey was conducted by using Braun-Blanquet's approach. The study also investigated the vegetation structure and its relationship with altitude and edaphic factors. The floristic data was analyzed by cluster anlaysis, detrended correspondence analysis and canonical correspondence analysis using CANACOO 5.0. A total of 110 plant species and 13 stands were merged into five major associations as dema rcated by cluster analysis and detrended correspondence analysis. The associations were Olea-Pinus-Themeda association, Myrsine-Rhus-Quercus association, Quercus-Rubus-Pinus association and Quercus association. Soil organic matter, saturation, pH and altitude play the major role in distribution of species. The variation in vegetation structure is controlled by the altitudinal gradient and physiochemical properties of soil. These results indicate a deteriorated forest structure and reduced regeneration pattern, demanding immediate attention of forest management authorities. Copyright © 2014 Hainan Medical College. Published by Elsevier B.V. All rights reserved.

  10. Effects of climate and geochemistry on soil organic matter stabilization and greenhouse gas emissions along altitudinal transects in different mountain regions

    Science.gov (United States)

    Griepentrog, Marco; Bodé, Samuel; Boudin, Mathieu; Dercon, Gerd; Doetterl, Sebastian; Matulanya, Machibya; Msigwa, Anna; Vermeir, Pieter; Boeckx, Pascal

    2017-04-01

    Terrestrial ecosystems are strongly influenced by climate change and soils are key compartments of the global carbon (C) cycle in terms of their potential to store or release significant amounts of C. This study is part of the interregional IAEA Technical Cooperation Project ``Assessing the Impact of Climate Change and its Effects on Soil and Water Resources in Polar and Mountainous Regions (INT5153)'' aiming to improve the understanding of climate change impacts on soil organic carbon (SOC) in fragile polar and high mountainous ecosystems at local and global scale for their better management and conservation. The project includes 13 benchmark sites situated around the world. Here we present novel data from altitudinal transects of three different mountain regions (Mount Kilimanjaro, Tanzania; Mount Gongga, China; Cordillera Blanca, Peru). All altitudinal transects cover a wide range of natural ecosystems under different climates and soil geochemistry. Bulk soil samples (four field replicates per ecosystem) were subjected to a combination of aggregate and particle-size fractionation followed by organic C, total nitrogen, stable isotope (13C, 15N) and radiocarbon (14C) analyses of all fractions. Bulk soils were further characterized for their geochemistry (Na, K, Ca, Mg, Al, Fe, Mn, Si, P) and incubated for 63 days to assess greenhouse gas emissions (CO2, CH4, NO, N2O). Further, stable C isotopic signature of CO2 was measured to determine the isotopic signature of soil respiration (using Keeling plots) and to estimate potential respiration sources. The following four ecosystems were sampled at an altitudinal transect on the (wet) southern slopes of Mount Kilimanjaro: savannah (920m), lower montane rain forests with angiosperm trees (2020m), upper montane cloud forest with gymnosperm trees (2680m), subalpine heathlands (3660m). Both forests showed highest C contents followed by subalpine and savannah. The largest part of SOC was found in particulate organic matter

  11. NUEVA ESPECIE DE RANA BROMELÍCOLA DEL GÉNERO PRISTIMANTIS (AMPHIBIA: CRAUGASTORIDAE, MESETA DE LA CORDILLERA DEL CÓNDOR, ECUADOR

    Directory of Open Access Journals (Sweden)

    JORGE BRITO M.

    Full Text Available RESUMEN Describimos una especie pequeña de rana bromelícola del género Pristimantis (longitud rostro-cloaca en hembras 20.3-23.3 mm; en machos 16.1-17.4 mm, proveniente de una remota meseta de arenisca de la Cordillera del Cóndor, en el sureste de Ecuador, con un rango altitudinal de 2.045-2.860 m. Una filogenia en base a secuencias de ADN (genes mitocondriales y nucleares muestra que la nueva especie forma parte del grupo P. orestes y está más cercanamente relacionada con una especie de Pristimantis aún no descrita de la vertiente sur oriental ecuatoriana. Difiere de sus congéneres de Ecuador, por su coloración dorsal y ventral predominantemente negra; superficie palmar amplia y robusta con dedos cortos y gruesos; presencia de un surco profundo y amplio extendido desde la base anterior del I dedo manual hasta la base posterior del tubérculo palmar; tubérculos subarticulares divididos, tubérculos supernumerarios agrandados y con granulaciones pequeñas. Todos los individuos registrados estuvieron en bromelias terrestres. Las llamadas son cortas, de frecuencia modulada, conformada por una nota con duración de 5-15 ms. Los insectos representaron el 80% de la dieta de la especie nueva.

  12. Average niche breadths of species in lake macrophyte communities respond to ecological gradients variably in four regions on two continents.

    Science.gov (United States)

    Alahuhta, Janne; Virtala, Antti; Hjort, Jan; Ecke, Frauke; Johnson, Lucinda B; Sass, Laura; Heino, Jani

    2017-05-01

    Different species' niche breadths in relation to ecological gradients are infrequently examined within the same study and, moreover, species niche breadths have rarely been averaged to account for variation in entire ecological communities. We investigated how average environmental niche breadths (climate, water quality and climate-water quality niches) in aquatic macrophyte communities are related to ecological gradients (latitude, longitude, altitude, species richness and lake area) among four distinct regions (Finland, Sweden and US states of Minnesota and Wisconsin) on two continents. We found that correlations between the three different measures of average niche breadths and ecological gradients varied considerably among the study regions, with average climate and average water quality niche breadth models often showing opposite trends. However, consistent patterns were also found, such as widening of average climate niche breadths and narrowing of average water quality niche breadths of aquatic macrophytes along increasing latitudinal and altitudinal gradients. This result suggests that macrophyte species are generalists in relation to temperature variations at higher latitudes and altitudes, whereas species in southern, lowland lakes are more specialised. In contrast, aquatic macrophytes growing in more southern nutrient-rich lakes were generalists in relation to water quality, while specialist species are adapted to low-productivity conditions and are found in highland lakes. Our results emphasise that species niche breadths should not be studied using only coarse-scale data of species distributions and corresponding environmental conditions, but that investigations on different kinds of niche breadths (e.g., climate vs. local niches) also require finer resolution data at broad spatial extents.

  13. Hydraulic gradients in rock aquifers

    International Nuclear Information System (INIS)

    Dahlblom, P.

    1992-05-01

    This report deals with fractured rock as a host for deposits of hazardous waste. In this context the rock, with its fractures containing moving groundwater, is called the geological barrier. The desired properties of the geological barrier are low permeability to water, low hydraulic gradients and ability to retain matter dissolved in the water. The hydraulic gradient together with the permeability and the porosity determines the migration velocity. Mathematical modelling of the migration involves calculation of the water flow and the hydrodynamic dispersion of the contaminant. The porous medium approach can be used to calculate mean flow velocities and hydrodynamic dispersion of a large number of fractures are connected, which means that a large volume have to be considered. It is assumed that the porous medium approach can be applied, and a number of idealized examples are shown. It is assumed that the groundwater table is replenished by percolation at a constant rate. One-dimensional analytical calculations show that zero hydraulic gradients may exist at relatively large distance from the coast. Two-dimensional numerical calculations show that it may be possible to find areas with low hydraulic gradients and flow velocities within blocks surrounded by areas with high hydraulic conductivity. (au)

  14. A theory of gradient analysis

    NARCIS (Netherlands)

    Braak, ter C.J.F.

    1988-01-01

    The theory of gradient analysis is presented in this chapter, in which the heuristic techniques are integrated with regression, calibration, ordination and constrained ordination as distinct, well-defined statistical problems. The various techniques used for each type of problem are classified into

  15. Compositional gradients in Gramineae genes

    DEFF Research Database (Denmark)

    Wong, Gane Ka-Shu; Wang, Jun; Tao, Lin

    2002-01-01

    In this study, we describe a property of Gramineae genes, and perhaps all monocot genes, that is not observed in eudicot genes. Along the direction of transcription, beginning at the junction of the 5'-UTR and the coding region, there are gradients in GC content, codon usage, and amino-acid usage...

  16. Orderings for conjugate gradient preconditionings

    Science.gov (United States)

    Ortega, James M.

    1991-01-01

    The effect of orderings on the rate of convergence of the conjugate gradient method with SSOR or incomplete Cholesky preconditioning is examined. Some results also are presented that help to explain why red/black ordering gives an inferior rate of convergence.

  17. Color gradients in elliptical galaxies

    International Nuclear Information System (INIS)

    Franx, M.; Illingworth, G.

    1990-01-01

    The relationship of the color gradients within ellipticals and the color differences between them are studied. It is found that the local color appears to be strongly related to the escape velocity. This suggests that the local escape velocity is the primary factor that determines the metallicity of the stellar population. Models with and without dark halos give comparable results. 27 refs

  18. Generation of charge imbalance in a superconductor by a temperature gradient

    International Nuclear Information System (INIS)

    Entin-Wohlman, O.; Orbach, R.

    1980-01-01

    The charge-imbalance voltage in a superconductor carrying a current in the presence of a temperature gradient is calculated from the Boltzmann equation in the clean limit. We demonstrate why the Green's-function approach in the dirty limit, first performed by Schmid and Schoem, generates the same Boltzmann-like equation for the distribution function. In addition, the charge-imbalance voltage in the absence of an impressed current is calculated. It is shown to depend on del 2 T+(delT) 2 /T, and not solely on (delT) 2 . The calculations are limited to the temperature regime near T/sub c/, such that Δ<< T

  19. Potencial del Agua del suelo

    Directory of Open Access Journals (Sweden)

    Bustamante Heliodoro

    1986-12-01

    Full Text Available La energía potencial del agua presenta diferencias de un punto del suelo a otro; esas diferencias son las que originan el movimiento del agua de acuerdo a la tendencia universal de la materia en el sentido de moverse de donde la energía potencial es mayor a donde dicha energía es menor. En el suelo el agua en consecuencia se mueve hacia donde su energía decrece hasta lograr su estado de equilibrio. Se desprende entonces que la cantidad de energía potencial absoluta contenida en el agua, no es importante por sí misma, sino por su relación con la energía en diferentes lugares dentro del suelo. El concepto Potencial de agua del suelo es un criterio para esta energía.

  20. Elemental gradients in macrophytes from a reactor effluent gradient

    International Nuclear Information System (INIS)

    Grace, J.B.; Tilly, L.J.

    1978-01-01

    The tissues of submersed macrophtes from along the thermal gradient were analyzed for phosphorus to determine whether any pattern correspondent to standing crop distributions could be detected. Although water concentrations of phosphorus showed no detectable relationship to the thermal effluent, tissue concentrations of this element in submersed macrophytes declined with distance from the effluent entry point. The occurrence of this concentration pattern suggests that phosphorus availability is greater near the discharge. Because phosphorus is the element most often determined to limit aquatic productivity, its greater availability may partially account for the apparent enhancement of macrophte growth near the thermal discharge. A patter of macrophyte abundance which indicated enchancement related to the discharge gradient in the reactor-cooling reservoir, Par Pond is reported. Correlative data tended to implicate light and temperature as important in influencing the differential abundance pattern

  1. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...... element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles. Some plane deformation problems relevant for certain specific orientations of a face centered cubic crystal under plane loading conditions are studied, and effective in......-plane parameters are developed based on the crystallographic properties of the material. The problem of cyclic shear of a single crystal between rigid platens is studied as well as void growth of a cylindrical void....

  2. Computational strain gradient crystal plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2014-01-01

    A numerical method for viscous strain gradient crystal plasticity theory is presented, which incorporates both energetic and dissipative gradient effects. The underlying minimum principles are discussed as well as convergence properties of the proposed finite element procedure. Three problems...... of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically...... oriented face centered cubic crystals are developed in terms of the crystallographic slip parameters. The effect on geometrically necessary dislocation structures introduced by plastic deformation is investigated as a function of the ratio of void radius to plasticity length scale....

  3. Vertebrate pressure-gradient receivers

    DEFF Research Database (Denmark)

    Christensen-Dalsgaard, Jakob

    2011-01-01

    The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and stro......The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum....... Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural...

  4. Primordial vorticity and gradient expansion

    CERN Document Server

    Giovannini, Massimo

    2012-01-01

    The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the $\\Lambda$CDM paradigm the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the or...

  5. Gradient computation for VTI acoustic wavefield tomography

    KAUST Repository

    Li, Vladimir; Wang, Hui; Tsvankin, Ilya; Diaz, Esteban; Alkhalifah, Tariq Ali

    2016-01-01

    -power objective functions. We also obtain the gradient expressions for the data-domain objective function, which can incorporate borehole information necessary for stable VTI velocity analysis. These gradients are compared to the ones obtained with a space

  6. del alcoholismo

    Directory of Open Access Journals (Sweden)

    Rodrigo Arias Duque

    2005-01-01

    Full Text Available Desde el punto de vista farmacológico, es importante comprender qué es el alcohol y cómo actúa en el organismo. No existe una causa simple, sino una interacción complicada de factores neuroquímicos, fisiológicos, psicológicos y sociales que originan y desarrollan esta grave enfermedad fármaco-dependiente. La acción psicofisiológica y farmacodinámica del alcohol es fundamentalmente depresiva, por la reducción de la transmisión sináptica en el sistema nervioso humano. Es un hecho conocido que el consumo excesivo de alcohol causa una disfunción aguda y crónica del cerebro, produciendo trastornos en el sistema nervioso central, presentando alteraciones en la memoria y en las funciones intelectuales como cálculo, comprensión y aprendizaje. A nivel hepático tiene lugar, en su mayoría, el metabolismo del alcohol, produciéndose un hígado graso alcohólico, aumentando el tamaño, terminando en necrosis e inflamación grave del hígado; esto se llama hepatitis alcohólica, y si se sigue consumiendo alcohol se desarrollará la cirrosis. El alcohol también ha estado relacionado con alteraciones del miocardio; se ha constatado en animales de experimentación sanos que tanto la velocidad de contracción del músculo cardiaco y su máxima tensión disminuyen en presencia del alcohol, como consecuencia, la fuerza de cada contracción y el aumento de presión en el ventrículo izquierdo son menores, perdiendo eficacia el corazón como bomba.

  7. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...... of gradient hardening are found to delay the onset of localization under plane strain tension, and significantly reduce strain gradients in the localized zone. For plane strain compression gradient hardening is found to increase the load-carrying capacity significantly....

  8. An education gradient in health, a health gradient in education, or a confounded gradient in both?

    Science.gov (United States)

    Lynch, Jamie L; von Hippel, Paul T

    2016-04-01

    There is a positive gradient associating educational attainment with health, yet the explanation for this gradient is not clear. Does higher education improve health (causation)? Do the healthy become highly educated (selection)? Or do good health and high educational attainment both result from advantages established early in the life course (confounding)? This study evaluates these competing explanations by tracking changes in educational attainment and Self-rated Health (SRH) from age 15 to age 31 in the National Longitudinal Study of Youth, 1997 cohort. Ordinal logistic regression confirms that high-SRH adolescents are more likely to become highly educated. This is partly because adolescent SRH is associated with early advantages including adolescents' academic performance, college plans, and family background (confounding); however, net of these confounders adolescent SRH still predicts adult educational attainment (selection). Fixed-effects longitudinal regression shows that educational attainment has little causal effect on SRH at age 31. Completion of a high school diploma or associate's degree has no effect on SRH, while completion of a bachelor's or graduate degree have effects that, though significant, are quite small (less than 0.1 points on a 5-point scale). While it is possible that educational attainment would have greater effect on health at older ages, at age 31 what we see is a health gradient in education, shaped primarily by selection and confounding rather than by a causal effect of education on health. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Strain gradient effects in surface roughening

    DEFF Research Database (Denmark)

    Borg, Ulrik; Fleck, N.A.

    2007-01-01

    evidence for strain gradient effects. Numerical analyses of a bicrystal undergoing in-plane tensile deformation are also studied using a strain gradient crystal plasticity theory and also by using a strain gradient plasticity theory for an isotropic solid. Both theories include an internal material length...

  10. Gradient remediability in linear distributed parabolic systems ...

    African Journals Online (AJOL)

    The aim of this paper is the introduction of a new concept that concerned the analysis of a large class of distributed parabolic systems. It is the general concept of gradient remediability. More precisely, we study with respect to the gradient observation, the existence of an input operator (gradient efficient actuators) ensuring ...

  11. Novo registro altitudinal de Trichodactylus fluviatilis (Latreille, 1828 (Decapoda, Trichodactylidae no Brasil - DOI: 10.4025/actascibiolsci.v31i3.785 New altitudinal record of Trichodactylus fluviatilis (Latreille, 1828 (Decapoda, Trichodactylidae in Brazil - DOI: 10.4025/actascibiolsci.v31i3.785

    Directory of Open Access Journals (Sweden)

    Bernadete Maria Sousa

    2009-07-01

    Full Text Available Trichodactylus fluviatilis (Latreille, 1828 (Decapoda, Trichodactylidae é uma espécie de caranguejo que habita rios e riachos montanhosos em altitudes até aproximadamente 500 m. Sua distribuição ocorre na América do Sul, desde as bacias costeiras da faixa leste do Brasil até a bacia do alto Paraná e na Argentina. O objetivo do presente trabalho foi registrar a ocorrência de T. fluviatilis em uma Unidade de Conservação de Juiz de Fora, Minas Gerais, e fornecer um novo registro altitudinal dessa espécie no Brasil. As amostras foram obtidas de outubro de 2004 a julho de 2005. Foram coletados três indivíduos vivos, dois machos e uma fêmea da espécie. Também foram analisados 16 regurgitos estomacais do cágado Hydromedusa maximiliani, dos quais, em seis foram encontrados partes corporais deste crustáceo. Muitas espécies de caranguejos do Brasil da família Trichodactylidae vivem em regiões acima de 500m do nível do mar. No presente estudo, T. fluviatilis foi coletado a 770 m de altitude, ampliando assim a faixa de distribuição altitudinal dessa espécie no Brasil. Até o presente estudo não existiam relatos de T. fluviatilis no município de Juiz de Fora, portanto este estudo também se constitui em um novo registro desse tricodatilídeo em Minas Gerais.Trichodactylus fluviatilis (Latreille, 1828 (Decapoda, Trichodactylidae is a crab species that lives in mountainous rivers and streams at altitudes up to 500m. Its distribution ranges from South America from the Basins of eastern coast of Brazil to basins of the Upper Paraná River and Argentina. The main objective of this study was to register a new occurrence of T. fluviatilis at a Conservation Unit in Juiz de Fora, Minas Gerais and provide a new altitudinal record for this species in Brazil. The samples were taken between October 2004 and July 2005. We collected three live T. fluviatilis individuals – two males and one female. We also analyzed the stomach contents of 16

  12. Temperature Gradient in Hall Thrusters

    International Nuclear Information System (INIS)

    Staack, D.; Raitses, Y.; Fisch, N.J.

    2003-01-01

    Plasma potentials and electron temperatures were deduced from emissive and cold floating probe measurements in a 2 kW Hall thruster, operated in the discharge voltage range of 200-400 V. An almost linear dependence of the electron temperature on the plasma potential was observed in the acceleration region of the thruster both inside and outside the thruster. This result calls into question whether secondary electron emission from the ceramic channel walls plays a significant role in electron energy balance. The proportionality factor between the axial electron temperature gradient and the electric field is significantly smaller than might be expected by models employing Ohmic heating of electrons

  13. Generalized Gradient Approximation Made Simple

    International Nuclear Information System (INIS)

    Perdew, J.P.; Burke, K.; Ernzerhof, M.

    1996-01-01

    Generalized gradient approximations (GGA close-quote s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. copyright 1996 The American Physical Society

  14. Dai-Kou type conjugate gradient methods with a line search only using gradient.

    Science.gov (United States)

    Huang, Yuanyuan; Liu, Changhe

    2017-01-01

    In this paper, the Dai-Kou type conjugate gradient methods are developed to solve the optimality condition of an unconstrained optimization, they only utilize gradient information and have broader application scope. Under suitable conditions, the developed methods are globally convergent. Numerical tests and comparisons with the PRP+ conjugate gradient method only using gradient show that the methods are efficient.

  15. Diversity of bees and their floral resources at altitudinal areas in the Southern Espinhaço Range, Minas Gerais, Brazil.

    Science.gov (United States)

    Araújo, Vinícius A; Antonini, Yasmine; Araújo, Ana P A

    2006-01-01

    The Southern Espinhaço Range consists of large areas covered by quartzitic or metaliferous tropical altitudinal fields. The Espinhaço Range ecosystems are endangered by anthropic high impacts, particularly due to mining and urbanization. We conducted a one-year inventory of the bee flora and fauna at the quartzitic Ouro Branco Mountains and a two-year survey of the metaliferous Ouro Preto fields. The samples were collected twice a month, from 8:00 am to 5:00 pm. The bees (677) belonged to 91 species, five families. The family Apidae was the richest and most abundant, followed by the Halictidae and Megachilidae. The bees visited 46 flowering plant species; the most visited plants were the Asteraceae (n = 220), the Malpighiaceae (n = 95), the Melastomataceae (n = 94), the Fabaceae (n = 78), and the Solanaceae (n = 63). Diversity was higher in Ouro Branco (H = 1.47) than in Ouro Preto (H = 1.17). The low richness and abundance of bees in our research site when compared to other Brazilian "Cerrado" areas can be due to the high altitude, low temperature, and low availability of flowers we found. "Canga" and rupestrian areas house fauna and flora species that are rare and threatened by extinction. The southern Espinhaço areas can, therefore, be given the status of permanent biodiversity preservation area.

  16. Taxonomic study of Onobrychis transcaspica V. Nikitin (Fabaceae in northeastern of Iran with emphasis on altitudinal effect on morphological characters using floristic marker

    Directory of Open Access Journals (Sweden)

    Zeinab Toluei

    2010-07-01

    Full Text Available Onobrychis Miller is the second largest genus of Fabaceae in Iran with nearly 60 species. These species are used as valuable forage plants. Onobrychis sect. Onobrychis with nearly 15 species in Iran is one of the important sections of the genus. Onobrychis transcaspica V. Nikitin, is one of the species of this section that is distributed in NE of Iran. To determine intraspecific variations in O. transcaspica from taxonomic point of view and effective ecological factor, data were collected using special station method. In this way, four special stations were recognized for O. transcaspica in NE of Iran. Results from floristic data (Floristic composition of each special station analysis with MVSP software by PCO method, led to identification of 3 separate groups that was indicative of existence of intraspecific diversity. Morphometric data analysis of individual collected from each special station, by using 65 vegetative and reproductive characters, with PCO and UPGMA methods, confirmed 3 mentioned floristic groups. Ecologic data analysis with CCA Method showed the presence of 3 phenoecodeme based on 3 morphologic groups resulting from altitudinal variations.

  17. Classification of Korean forests: patterns along geographic and environmental gradients

    Czech Academy of Sciences Publication Activity Database

    Černý, T.; Kopecký, Martin; Petřík, Petr; Song, J.-S.; Šrůtek, M.; Valachovič, M.; Altman, Jan; Doležal, Jiří

    2015-01-01

    Roč. 18, č. 1 (2015), s. 5-22 ISSN 1402-2001 R&D Projects: GA ČR GA206/05/0119; GA ČR GA13-13368S; GA AV ČR IAA600050802 Grant - others:AVČR & Korean Science and Engeneering Foundation (KOSEF)(CZ) M200050902 Institutional support: RVO:67985939 Keywords : altitudinal zones * East Asia * ISOPAM Subject RIV: EH - Ecology, Behaviour Impact factor: 2.308, year: 2015

  18. Ternary gradient metal-organic frameworks.

    Science.gov (United States)

    Liu, Chong; Rosi, Nathaniel L

    2017-09-08

    Gradient MOFs contain directional gradients of either structure or functionality. We have successfully prepared two ternary gradient MOFs based on bMOF-100 analogues, namely bMOF-100/102/106 and bMOF-110/100/102, via cascade ligand exchange reactions. The cubic unit cell parameter discrepancy within an individual ternary gradient MOF crystal is as large as ∼1 nm, demonstrating the impressive compatibility and flexibility of the component MOF materials. Because of the presence of a continuum of unit cells, the pore diameters within individual crystals also change in a gradient fashion from ∼2.5 nm to ∼3.0 nm for bMOF-100/102/106, and from ∼2.2 nm to ∼2.7 nm for bMOF-110/100/102, indicating significant porosity gradients. Like previously reported binary gradient MOFs, the composition of the ternary gradient MOFs can be easily controlled by adjusting the reaction conditions. Finally, X-ray diffraction and microspectrophotometry were used to analyse fractured gradient MOF crystals by comparing unit cell parameters and absorbance spectra at different locations, thus revealing the profile of heterogeneity (i.e. gradient distribution of properties) and further confirming the formation of ternary gradient MOFs.

  19. Strain gradient effects on cyclic plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Legarth, Brian Nyvang

    2010-01-01

    Size effects on the cyclic shear response are studied numerically using a recent higher order strain gradient visco-plasticity theory accounting for both dissipative and energetic gradient hardening. Numerical investigations of the response under cyclic pure shear and shear of a finite slab between...... rigid platens have been carried out, using the finite element method. It is shown for elastic–perfectly plastic solids how dissipative gradient effects lead to increased yield strength, whereas energetic gradient contributions lead to increased hardening as well as a Bauschinger effect. For linearly...... hardening materials it is quantified how dissipative and energetic gradient effects promote hardening above that of conventional predictions. Usually, increased hardening is attributed to energetic gradient effects, but here it is found that also dissipative gradient effects lead to additional hardening...

  20. Culturas del Mundo

    DEFF Research Database (Denmark)

    Benwell, Ann Fenger; Costa, Alberto; Waehle, Espen

    2006-01-01

    ’Culturas del mundo. Colecciones del Museo Nacional de Dinamarca’ with Ann Fenger Benwell in Culturas del Mundo. Colecciones del Museo Nacional de Dinamarca, ed. Silvia Sauquet, Fundación "la Caixa", Barcelona 2006, pp. 31-39......’Culturas del mundo. Colecciones del Museo Nacional de Dinamarca’ with Ann Fenger Benwell in Culturas del Mundo. Colecciones del Museo Nacional de Dinamarca, ed. Silvia Sauquet, Fundación "la Caixa", Barcelona 2006, pp. 31-39...

  1. High gradient RF breakdown study

    International Nuclear Information System (INIS)

    Laurent, L.; Luhmann, N.C. Jr.; Scheitrum, G.; Hanna, S.; Pearson, C.; Phillips, R.

    1998-01-01

    Stanford Linear Accelerator Center and UC Davis have been investigating high gradient RF breakdown and its effects on pulse shortening in high energy microwave devices. RF breakdown is a critical issue in the development of high power microwave sources and next generation linear accelerators since it limits the output power of microwave sources and the accelerating gradient of linacs. The motivation of this research is to find methods to increase the breakdown threshold level in X-band structures by reducing dark current. Emphasis is focused on improved materials, surface finish, and cleanliness. The test platform for this research is a traveling wave resonant ring. A 30 MW klystron is employed to provide up to 300 MW of traveling wave power in the ring to trigger breakdown in the cavity. Five TM 01 cavities have previously been tested, each with a different combination of surface polish and/or coating. The onset of breakdown was extended up to 250 MV/m with a TiN surface finish, as compared to 210 MV/m for uncoated OFE copper. Although the TiN coating was helpful in depressing the field emission, the lowest dark current was obtained with a 1 microinch surface finish, single-point diamond-turned cavity

  2. NIF optics phase gradient specfication

    International Nuclear Information System (INIS)

    Williams, W.; Auerbach, J.; Hunt, J.; Lawson, L.; Manes, K.; Orth, C.; Sacks, R.; Trenholme, J.; Wegner, P.

    1997-01-01

    A root-mean-square (rms) phase gradient specification seems to allow a good connection between the NIP optics quality and focal spot requirements. Measurements on Beamlet optics individually, and as a chain, indicate they meet the assumptions necessary to use this specification, and that they have a typical rms phase gradient of ∼80 angstrom/cm. This may be sufficient for NIP to meet the proposed Stockpile Stewardship Management Program (SSMP) requirements of 80% of a high- power beam within a 200-250 micron diameter spot. Uncertainties include, especially, the scale length of the optics phase noise, the ability of the adaptive optic to correct against pump-induced distortions and optics noise, and the possibility of finding mitigation techniques against whole-beam self-focusing (e.g. a pre- correction optic). Further work is needed in these areas to better determine the NIF specifications. This memo is a written summary of a presentation on this topic given by W. Williams 24 April 1997 to NIP and LS ampersand T personnel

  3. The impact of distance and a shifting temperature gradient on genetic connectivity across a heterogeneous landscape

    Directory of Open Access Journals (Sweden)

    Offord Catherine A

    2011-05-01

    Full Text Available Abstract Background Inter-population distance and differences in breeding times are barriers to reproduction that can contribute to genotypic differentiation between populations. Temporal changes in environmental conditions and local selective processes can further contribute to the establishment of reproductive barriers. Telopea speciosissima (Proteaceae is an excellent subject for studying the effect of geographic, edaphic and phenological heterogeneity on genotypic differentiation because previous studies show that these factors are correlated with morphological variation. Molecular, morphological and environmental datasets were combined to characterise the relative influence of these factors on inter-population differentiation, and Bayesian analyses were used to investigate current levels of admixture between differentiated genomes. Results A landscape genetic approach involving molecular and morphological analyses identified three endpoints of differentiated population groups: coastal, upland and southern. The southern populations, isolated from the other populations by an edaphic barrier, show low migration and no evidence of admixture with other populations. Amongst the northern populations, coastal and upland populations are connected along a skewed altitudinal gradient by genetically intermediate populations. The strong association between temperature and flowering time in Telopea speciosissima was shown to maintain a temporally unstable reproductive barrier between coastal and upland populations. Conclusions Substrate-mediated allopatry appears to be responsible for long-term genetic isolation of the southern populations. However, the temperature-dependent reproductive barrier between upland and coastal populations bears the genetic signature of temporal adjustments. The extreme climatic events of the last glacial maximum are likely to have caused more complete allochronic isolation between upland and coastal populations, as well as

  4. Strength gradient enhances fatigue resistance of steels

    Science.gov (United States)

    Ma, Zhiwei; Liu, Jiabin; Wang, Gang; Wang, Hongtao; Wei, Yujie; Gao, Huajian

    2016-02-01

    Steels are heavily used in infrastructure and the transportation industry, and enhancing their fatigue resistance is a major challenge in materials engineering. In this study, by introducing a gradient microstructure into 304 austenitic steel, which is one of the most widely used types of stainless steel, we show that a strength gradient substantially enhances the fatigue life of the material. Pre-notched samples with negative strength gradients in front of the notch’s tip endure many more fatigue cycles than do samples with positive strength gradients during the crack initiation stage, and samples with either type of gradient perform better than do gradient-free samples with the same average yield strength. However, as a crack grows, samples with positive strength gradients exhibit better resistance to fatigue crack propagation than do samples with negative gradients or no gradient. This study demonstrates a simple and promising strategy for using gradient structures to enhance the fatigue resistance of materials and complements related studies of strength and ductility.

  5. Mitochondrial DNA markers reveal high genetic diversity but low genetic differentiation in the black fly Simulium tani Takaoka & Davies along an elevational gradient in Malaysia.

    Directory of Open Access Journals (Sweden)

    Van Lun Low

    Full Text Available The population genetic structure of Simulium tani was inferred from mitochondria-encoded sequences of cytochrome c oxidase subunits I (COI and II (COII along an elevational gradient in Cameron Highlands, Malaysia. A statistical parsimony network of 71 individuals revealed 71 haplotypes in the COI gene and 43 haplotypes in the COII gene; the concatenated sequences of the COI and COII genes revealed 71 haplotypes. High levels of genetic diversity but low levels of genetic differentiation were observed among populations of S. tani at five elevations. The degree of genetic diversity, however, was not in accordance with an altitudinal gradient, and a Mantel test indicated that elevation did not have a limiting effect on gene flow. No ancestral haplotype of S. tani was found among the populations. Pupae with unique structural characters at the highest elevation showed a tendency to form their own haplotype cluster, as revealed by the COII gene. Tajima's D, Fu's Fs, and mismatch distribution tests revealed population expansion of S. tani in Cameron Highlands. A strong correlation was found between nucleotide diversity and the levels of dissolved oxygen in the streams where S. tani was collected.

  6. Variability of Lepidoptera communities (moths and butterflies) along an altitudinal gradient of peat bogs from the Třeboň Basin up to the Bohemian Forest (South Bohemia, Central Europe)

    Czech Academy of Sciences Publication Activity Database

    Jaroš, Josef; Spitzer, Karel; Zikmundová, Hana

    2014-01-01

    Roč. 20, č. 2 (2014), s. 55-95 ISSN 1211-7420 Institutional support: RVO:60077344 Keywords : moths and butterflies * peatlands * communities Subject RIV: EH - Ecology, Behaviour http://www.npsumava.cz/gallery/27/8381-sg_20_2_jarosetal.pdf

  7. Thermal conduction down steep temperature gradients

    International Nuclear Information System (INIS)

    Bell, A.R.; Evans, R.G.; Nicholas, D.J.

    1980-08-01

    The Fokker-Planck equation has been solved numerically in one spatial and two velocity dimensions in order to study thermal conduction in large temperature gradients. An initially cold plasma is heated at one end of the spatial grid producing temperature gradients with scale lengths of a few times the electron mean free path. The heat flow is an order of magnitude smaller than that predicted by the classical theory which is valid in the limit of small temperature gradients. (author)

  8. Testing the limits of gradient sensing.

    Directory of Open Access Journals (Sweden)

    Vinal Lakhani

    2017-02-01

    Full Text Available The ability to detect a chemical gradient is fundamental to many cellular processes. In multicellular organisms gradient sensing plays an important role in many physiological processes such as wound healing and development. Unicellular organisms use gradient sensing to move (chemotaxis or grow (chemotropism towards a favorable environment. Some cells are capable of detecting extremely shallow gradients, even in the presence of significant molecular-level noise. For example, yeast have been reported to detect pheromone gradients as shallow as 0.1 nM/μm. Noise reduction mechanisms, such as time-averaging and the internalization of pheromone molecules, have been proposed to explain how yeast cells filter fluctuations and detect shallow gradients. Here, we use a Particle-Based Reaction-Diffusion model of ligand-receptor dynamics to test the effectiveness of these mechanisms and to determine the limits of gradient sensing. In particular, we develop novel simulation methods for establishing chemical gradients that not only allow us to study gradient sensing under steady-state conditions, but also take into account transient effects as the gradient forms. Based on reported measurements of reaction rates, our results indicate neither time-averaging nor receptor endocytosis significantly improves the cell's accuracy in detecting gradients over time scales associated with the initiation of polarized growth. Additionally, our results demonstrate the physical barrier of the cell membrane sharpens chemical gradients across the cell. While our studies are motivated by the mating response of yeast, we believe our results and simulation methods will find applications in many different contexts.

  9. Biological soil crusts in Chile along the precipitation gradient

    Science.gov (United States)

    Samolov, Elena; Glaser, Karin; Baumann, Karen; Leinweber, Peter; Jung, Patrick; Büdel, Burkhard; Mikhailyuk, Tatiana; Karsten, Ulf

    2017-04-01

    Biological soil crusts in Chile along a precipitation gradient Elena Samolov* (1), Karin Glaser (1), Karen Baumann (2), Peter Leinweber (2), Patrick Jung (3), Burkhard Büdel (3), Tatiana Mikhailyuk (4) and Ulf Karsten (1) (1) Institute of Biological Sciences - Applied Ecology and Phycology, University of Rostock, Rostock, Germany, (2) Faculty of Agricultural and Environmental Sciences - Soil Sciences, University of Rostock, Rostock, Germany (3) University of Kaiserslautern, Kaiserslautern, Germany (4) M.H. Kholodny Institute of Botany, National Academy of Science of Ukraine, Kyiv, Ukraine * elena.samolov@uni-rostock.de Biological soil crusts (BSCs) are an association of different microorganisms and soil particles in the top millimeters of the soil. They are formed by algae, cyanobacteria, microfungi, bacteria, bryophytes and lichens in various compositions; together with their by-products they create a micro-ecosystem that performs important ecological functions, e.g. primary production, nitrogen fixation, mineralization and stabilization of soils. These top-soil assemblages are almost unstudied in South America (Büdel et al. 2016). Therefore, our aim is to investigate for the first time biodiversity of the key photosynthetic organisms, green algae and cyanobacteria following a precipitation gradient along the west coast of Chile. We are applying polyphasic approach - a combination of microscopy, culture dependent (16S and 18S rRNA, ITS) and culture independent molecular techniques (NGS). First results, based on culturing and light microscopy, showed high diversity of eukaryotic algae in biocrusts from humid regions, followed by semi-arid regions. Lichen dominated biocrusts from arid regions were characterized by a high diversity of green algae, while cyanobacteria were scarcely present. The functional role of the BSCs in the biogeochemical cycle of phosphorous (P) was evaluated using state of the art analytical methods including 31P-NMR (nuclear magnetic

  10. Gradient Flow Convolutive Blind Source Separation

    DEFF Research Database (Denmark)

    Pedersen, Michael Syskind; Nielsen, Chinton Møller

    2004-01-01

    Experiments have shown that the performance of instantaneous gradient flow beamforming by Cauwenberghs et al. is reduced significantly in reverberant conditions. By expanding the gradient flow principle to convolutive mixtures, separation in a reverberant environment is possible. By use...... of a circular four microphone array with a radius of 5 mm, and applying convolutive gradient flow instead of just applying instantaneous gradient flow, experimental results show an improvement of up to around 14 dB can be achieved for simulated impulse responses and up to around 10 dB for a hearing aid...

  11. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2003-01-01

    By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter...... the tangent moduli governing increments of stress and strain. It is shown that the modification is far from benign from a mathematical standpoint, changing the qualitative character of solutions and leading to a new type of localization that is at odds with what is expected from a strain gradient theory....... The findings raise questions about the physical acceptability of this class of strain gradient theories....

  12. Community and ecosystem responses to elevational gradients

    DEFF Research Database (Denmark)

    Sundqvist, Maja K.; Sanders, Nate; Wardle, David A.

    2013-01-01

    Community structure and ecosystem processes often vary along elevational gradients. Their responses to elevation are commonly driven by changes in temperature, and many community- and ecosystem-level variables therefore frequently respond similarly to elevation across contrasting gradients...... elevational gradients for understanding community and ecosystem responses to global climate change at much larger spatial and temporal scales than is possible through conventional ecological experiments. However, future studies that integrate elevational gradient approaches with experimental manipulations...... will provide powerful information that can improve predictions of climate change impacts within and across ecosystems....

  13. STOCHASTIC GRADIENT METHODS FOR UNCONSTRAINED OPTIMIZATION

    Directory of Open Access Journals (Sweden)

    Nataša Krejić

    2014-12-01

    Full Text Available This papers presents an overview of gradient based methods for minimization of noisy functions. It is assumed that the objective functions is either given with error terms of stochastic nature or given as the mathematical expectation. Such problems arise in the context of simulation based optimization. The focus of this presentation is on the gradient based Stochastic Approximation and Sample Average Approximation methods. The concept of stochastic gradient approximation of the true gradient can be successfully extended to deterministic problems. Methods of this kind are presented for the data fitting and machine learning problems.

  14. Evidence of Facilitation Cascade Processes as Drivers of Successional Patterns of Ecosystem Engineers at the Upper Altitudinal Limit of the Dry Puna.

    Science.gov (United States)

    Malatesta, Luca; Tardella, Federico Maria; Piermarteri, Karina; Catorci, Andrea

    2016-01-01

    Facilitation processes constitute basic elements of vegetation dynamics in harsh systems. Recent studies in tropical alpine environments demonstrated how pioneer plant species defined as "ecosystem engineers" are capable of enhancing landscape-level richness by adding new species to the community through the modification of microhabitats, and also provided hints about the alternation of different ecosystem engineers over time. Nevertheless, most of the existing works analysed different ecosystem engineers separately, without considering the interaction of different ecosystem engineers. Focusing on the altitudinal limit of Peruvian Dry Puna vegetation, we hypothesized that positive interactions structure plant communities by facilitation cascades involving different ecosystem engineers, determining the evolution of the microhabitat patches in terms of abiotic resources and beneficiary species hosted. To analyze successional mechanisms, we used a "space-for-time" substitution to account for changes over time, and analyzed data on soil texture, composition, and temperature, facilitated species and their interaction with nurse species, and surface area of engineered patches by means of chemical analyses, indicator species analysis, and rarefaction curves. A successional process, resulting from the dynamic interaction of different ecosystem engineers, which determined a progressive amelioration of soil conditions (e.g. nitrogen and organic matter content, and temperature), was the main driver of species assemblage at the community scale, enhancing species richness. Cushion plants act as pioneers, by starting the successional processes that continue with shrubs and tussocks. Tussock grasses have sometimes been found to be capable of creating microhabitat patches independently. The dynamics of species assemblage seem to follow the nested assemblage mechanism, in which the first foundation species to colonize a habitat provides a novel substrate for colonization by other

  15. Evidence of Facilitation Cascade Processes as Drivers of Successional Patterns of Ecosystem Engineers at the Upper Altitudinal Limit of the Dry Puna.

    Directory of Open Access Journals (Sweden)

    Luca Malatesta

    Full Text Available Facilitation processes constitute basic elements of vegetation dynamics in harsh systems. Recent studies in tropical alpine environments demonstrated how pioneer plant species defined as "ecosystem engineers" are capable of enhancing landscape-level richness by adding new species to the community through the modification of microhabitats, and also provided hints about the alternation of different ecosystem engineers over time. Nevertheless, most of the existing works analysed different ecosystem engineers separately, without considering the interaction of different ecosystem engineers. Focusing on the altitudinal limit of Peruvian Dry Puna vegetation, we hypothesized that positive interactions structure plant communities by facilitation cascades involving different ecosystem engineers, determining the evolution of the microhabitat patches in terms of abiotic resources and beneficiary species hosted. To analyze successional mechanisms, we used a "space-for-time" substitution to account for changes over time, and analyzed data on soil texture, composition, and temperature, facilitated species and their interaction with nurse species, and surface area of engineered patches by means of chemical analyses, indicator species analysis, and rarefaction curves. A successional process, resulting from the dynamic interaction of different ecosystem engineers, which determined a progressive amelioration of soil conditions (e.g. nitrogen and organic matter content, and temperature, was the main driver of species assemblage at the community scale, enhancing species richness. Cushion plants act as pioneers, by starting the successional processes that continue with shrubs and tussocks. Tussock grasses have sometimes been found to be capable of creating microhabitat patches independently. The dynamics of species assemblage seem to follow the nested assemblage mechanism, in which the first foundation species to colonize a habitat provides a novel substrate for

  16. Risk Factors for the Presence of Chikungunya and Dengue Vectors (Aedes aegypti and Aedes albopictus), Their Altitudinal Distribution and Climatic Determinants of Their Abundance in Central Nepal

    Science.gov (United States)

    Dhimal, Meghnath; Gautam, Ishan; Joshi, Hari Datt; O’Hara, Robert B.; Ahrens, Bodo; Kuch, Ulrich

    2015-01-01

    Background The presence of the recently introduced primary dengue virus vector mosquito Aedes aegypti in Nepal, in association with the likely indigenous secondary vector Aedes albopictus, raises public health concerns. Chikungunya fever cases have also been reported in Nepal, and the virus causing this disease is also transmitted by these mosquito species. Here we report the results of a study on the risk factors for the presence of chikungunya and dengue virus vectors, their elevational ceiling of distribution, and climatic determinants of their abundance in central Nepal. Methodology/Principal Findings We collected immature stages of mosquitoes during six monthly cross-sectional surveys covering six administrative districts along an altitudinal transect in central Nepal that extended from Birgunj (80 m above sea level [asl]) to Dhunche (highest altitude sampled: 2,100 m asl). The dengue vectors Ae. aegypti and Ae. albopictus were commonly found up to 1,350 m asl in Kathmandu valley and were present but rarely found from 1,750 to 2,100 m asl in Dhunche. The lymphatic filariasis vector Culex quinquefasciatus was commonly found throughout the study transect. Physiographic region, month of collection, collection station and container type were significant predictors of the occurrence and co-occurrence of Ae. aegypti and Ae. albopictus. The climatic variables rainfall, temperature, and relative humidity were significant predictors of chikungunya and dengue virus vectors abundance. Conclusions/Significance We conclude that chikungunya and dengue virus vectors have already established their populations up to the High Mountain region of Nepal and that this may be attributed to the environmental and climate change that has been observed over the decades in Nepal. The rapid expansion of the distribution of these important disease vectors in the High Mountain region, previously considered to be non-endemic for dengue and chikungunya fever, calls for urgent actions to

  17. Especies, distribución y hospedantes del género Anastrepha Schiner en el departamento del Tolima, Colombia

    Directory of Open Access Journals (Sweden)

    Castañeda Marìa del Rosario

    2010-08-01

    Full Text Available Las moscas del género Anastrepha constituyen una de las principales
    plagas de la fruticultura colombiana. El conocimiento
    de la diversidad de especies presentes en un área es el primer
    paso en el diseño de estudios tendientes a establecer tecnologías
    apropiadas de manejo. Además de un listado de las especies de
    Anastrepha identificadas en el Laboratorio de Entomología de
    la Universidad
    del Tolima desde 1988 hasta la fecha a través de
    diversos estudios realizados en este departamento, el presente
    trabajo incluye también la distribución y hospederos de dichas
    especies provenientes de diez municipios del departamento,
    con alturas entre 300 y 2.500 msnm. Se identificaron 60.688
    especímenes pertenecientes a 24 especies de Anastrepha.
    Mediante la recolección de frutos se asociaron 16 especies de
    hospederos (incluyendo
    cinco nuevos reportes a nueve especies
    de Anastrepha. Las especies A. distincta Greene, A. sororcula
    Zucchi y A. striata Schiner fueron las que presentaron una
    distribución altitudinal más amplia (300 a 2.200 msnm. Por
    su parte, A. obliqua solo se encontró desde los 300 hasta los
    1.550 msnm. Especies de importancia cuarentenaria como A.
    fraterculus (Wiedemann, A. grandis Macquart y A. serpentina
    (Wiedemann se encontraron por arriba de los 1.100, 960 y 900
    msnm, respectivamente.

  18. Capture-zone design in an aquifer influenced by cyclic fluctuations in hydraulic gradients

    Science.gov (United States)

    Zawadzki, Willy; Chorley, Don; Patrick, Guy

    2002-10-01

    alors réalisées sur la base du gradient hydraulique moyen déterminé au moyen de techniques de filtrage sur des mesures continues de la piézométrie. Lorsque la période de la fluctuation cyclique dans le gradient hydraulique est proche de ou supérieure au temps de parcours du contaminant, les variations résultantes de gradient hydraulique ne peuvent plus être ignorées. Dans ces cas-là, des procédures ont été mises au point pour prendre en compte ces fluctuations dans la conception de la zone d'extraction. Celles-ci prennent en considération la caractérisation propre du régime de la nappe, l'évaluation du temps de parcours moyen et de la période des fluctuations cycliques, et des techniques numériques qui permettent de considérer les fluctuations cycliques dans la conception de la zone d'extraction. Resumen. El diseño de un sistema de bombeo y tratamiento de aguas subterráneas para una instalación de manufactura de madera que está próxima al estuario del río Fraser, sometido a la influencia de las mareas, ha requerido el desarrollo de metodologías para tener en cuenta las variaciones cíclicas de los gradientes hidráulicos. El diseño de tales sistemas debe considerar los efectos de las fluctuaciones cíclicas en la captura de contaminantes en fase disuelta. Cuando el período de la fluctuación cíclica es mucho menor que el tiempo de tránsito del contaminante disuelto entre el punto de entrada y el de descarga, se puede ignorar las variaciones del gradiente hidráulico provocadas por dichos ciclos. Las zonas de captura se diseñan entonces en función del gradiente hidráulico promedio, que se determina mediante técnicas de filtrado de medidas continuas del nivel piezométrico. Cuando el período de la fluctuación cíclica del gradiente hidráulico es comparable o mayor que el tiempo de tránsito del contaminante, no puede ignorarse las variaciones resultantes en el gradiente hidráulico. En ese caso, se tiene que desarrollar

  19. Gravity gradient preprocessing at the GOCE HPF

    Science.gov (United States)

    Bouman, J.; Rispens, S.; Gruber, T.; Schrama, E.; Visser, P.; Tscherning, C. C.; Veicherts, M.

    2009-04-01

    One of the products derived from the GOCE observations are the gravity gradients. These gravity gradients are provided in the Gradiometer Reference Frame (GRF) and are calibrated in-flight using satellite shaking and star sensor data. In order to use these gravity gradients for application in Earth sciences and gravity field analysis, additional pre-processing needs to be done, including corrections for temporal gravity field signals to isolate the static gravity field part, screening for outliers, calibration by comparison with existing external gravity field information and error assessment. The temporal gravity gradient corrections consist of tidal and non-tidal corrections. These are all generally below the gravity gradient error level, which is predicted to show a 1/f behaviour for low frequencies. In the outlier detection the 1/f error is compensated for by subtracting a local median from the data, while the data error is assessed using the median absolute deviation. The local median acts as a high-pass filter and it is robust as is the median absolute deviation. Three different methods have been implemented for the calibration of the gravity gradients. All three methods use a high-pass filter to compensate for the 1/f gravity gradient error. The baseline method uses state-of-the-art global gravity field models and the most accurate results are obtained if star sensor misalignments are estimated along with the calibration parameters. A second calibration method uses GOCE GPS data to estimate a low degree gravity field model as well as gravity gradient scale factors. Both methods allow to estimate gravity gradient scale factors down to the 10-3 level. The third calibration method uses high accurate terrestrial gravity data in selected regions to validate the gravity gradient scale factors, focussing on the measurement band. Gravity gradient scale factors may be estimated down to the 10-2 level with this method.

  20. Diversidad y distribución de mariposas Satyrinae (Lepidoptera: Nymphalidae en la cuenca del río Coello, Colombia

    Directory of Open Access Journals (Sweden)

    Jack F García-Perez

    2007-06-01

    Full Text Available Este estudio describe los patrones de diversidad y distribución de la subfamilia Satyrinae en la cuenca del río Coello (4º 17’ 08’’ N y 74º 35´ 36" W; 1 899.31 km², en un gradiente altitudinal de 433 a 3 600 m.s.n.m, con el fin de determinar la diversidad y composición regional y local de este grupo de mariposas y su posible uso como indicador biológico de zonas montanas y de Páramo. Se establecieron 11 estaciones de muestreo las cuales incluyen distintas zonas de vida. Las muestras se recolecciónron durante un periodo de 11 días en marzo, mayo, julio y octubre de 2003, en tres tipos de hábitat (bosque, borde de bosque y pradera. La recolección fue al azar en transectos de longitud no definida, entre las 09:00 y las 15:00 hr, empleando para ello redes lepidopterológicas de 0.5 m de diámetro y 1.20 m de longitud. Para el análisis de datos se calculó el índice de riqueza de Margalef (D y se registró el porcentaje de abundancia relativa para las especies. La diversidad total por localidad y por hábitat se analizó a través del índice de Shannon (H’. De las matrices de presencia-ausencia se obtuvo índices de similitud entre estaciones, según coeficiente de Jaccard. Se recolectó un total de 239 individuos de 13 géneros y 34 especies. Las especies más abundantes fueron especialmente del género Pedaliodes, representando el 41.4%. La riqueza y diversidad, presentaron un comportamiento similar, mostrando altos valores en zonas montanas y de Páramo (> 2000 m.s.n.m. En cuanto a la diversidad por hábitat, se observó la mayor diversidad en el borde de bosque. El análisis de similitud evidenció dos grupos claramente definidos. El primer grupo contempla especies propias de zonas cálidas (Euptychia hesione y Hermeuptychia hermes y templadas (Pseudohaetera hypaesia y Taygetis celia, mientras el segundo presenta especies exclusivas de zonas montanas y de Páramo (Lymanopoda obsoleta, Pedaliodes polusca y Eretris calisto

  1. Estructura poblacional y relaciones ambientales del árbol tropical Nectandra rudis (Lauraceae, una especie rara en el occidente de México

    Directory of Open Access Journals (Sweden)

    Ramón Cuevas Guzmán

    2008-03-01

    Full Text Available Nectandra rudis es una especie rara en el occidente de México. Analizamos la población y la comunidad donde se desarrolla, en la Sierra de Manantlan, Jalisco, México. Establecimos cuatro parcelas de 60x48 m con diferencias altitudinales de 100 m entre sí. En cada una seleccionamos aleatoriamente diez círculos de 100 m² cada uno, en los cuales medimos los diámetros normales y las alturas de las especies leñosas con diámetro 2.5 cm. Para cada especie y por parcela determinamos el área basal, la densidad, la frecuencia, la riqueza de especies y los valores de importancia. Establecimos la estructura vertical y diamétrica de N. rudis. Hicimos una ordenación directa con la matriz de especies y las variables edáficas y ambientales. El registro de N. rudis en la Sierra de Manantlán representa el primer registro para el occidente de México y el más septentrional del taxon. La población se estructura en cinco categorías diamétricas y genera una curva en forma de "J" invertida. La riqueza de especies en las parcelas donde se encuentra N. rudis, varía de 27 a 39, y los mayores valores de importancia son para Urera verrucosa, N. rudis y Ficus sp. La ordenación directa permite postular a la presencia de árboles caídos, la cobertura, la profundidad del horizonte superficial y el magnesio soluble, como los factores ambientales de mayor influencia en la distribución y abundancia de N. rudis.Population structure and environmental relationships of the tropical tree Nectandra rudis (Lauraceae, a rare species in western Mexico. The tree N. rudis is a rare species from western Mexico of which community and population features are unknown. We studied a population in an altitudinal gradient, from 550-1 850 m above sea level in the Sierra de Manantlan, Jalisco, Mexico. We established four 60x48 m sample sites at vertical distances of 100 m along this altitudinal gradient. Within each plot, ten 100 m² circular sub-sampling units were randomly

  2. Canonical trivialization of gravitational gradients

    International Nuclear Information System (INIS)

    Niedermaier, Max

    2017-01-01

    A one-parameter family of canonical transformations is constructed that reduces the Hamiltonian form of the Einstein–Hilbert action to its strong coupling limit where dynamical spatial gradients are absent. The parameter can alternatively be viewed as the overall scale of the spatial metric or as a fractional inverse power of Newton’s constant. The generating function of the canonical transformation is constructed iteratively as a powerseries in the parameter to all orders. The algorithm draws on Lie–Deprit transformation theory and defines a ‘trivialization map’ with several bonus properties: (i) Trivialization of the Hamiltonian constraint implies that of the action while the diffeomorphism constraint is automatically co-transformed. (ii) Only a set of ordinary differential equations needs to be solved to drive the iteration via a homological equation where no gauge fixing is required. (iii) In contrast to (the classical limit of) a Lagrangian trivialization map the algorithm also produces series solutions of the field equations. (iv) In the strong coupling theory temporal gauge variations are abelian, nevertheless the map intertwines with the respective gauge symmetries on the action, the field equations, and their solutions. (paper)

  3. Canonical trivialization of gravitational gradients

    Science.gov (United States)

    Niedermaier, Max

    2017-06-01

    A one-parameter family of canonical transformations is constructed that reduces the Hamiltonian form of the Einstein-Hilbert action to its strong coupling limit where dynamical spatial gradients are absent. The parameter can alternatively be viewed as the overall scale of the spatial metric or as a fractional inverse power of Newton’s constant. The generating function of the canonical transformation is constructed iteratively as a powerseries in the parameter to all orders. The algorithm draws on Lie-Deprit transformation theory and defines a ‘trivialization map’ with several bonus properties: (i) Trivialization of the Hamiltonian constraint implies that of the action while the diffeomorphism constraint is automatically co-transformed. (ii) Only a set of ordinary differential equations needs to be solved to drive the iteration via a homological equation where no gauge fixing is required. (iii) In contrast to (the classical limit of) a Lagrangian trivialization map the algorithm also produces series solutions of the field equations. (iv) In the strong coupling theory temporal gauge variations are abelian, nevertheless the map intertwines with the respective gauge symmetries on the action, the field equations, and their solutions.

  4. Rank gradient and p-gradient of amalgamated free products and HNN extensions

    OpenAIRE

    Pappas, Nathaniel

    2013-01-01

    We calculate the rank gradient and p-gradient of free products, free products with amalgamation over an amenable subgroup, and HNN extensions with an amenable associated subgroup. The notion of cost is used to compute the rank gradient of amalgamated free products and HNN extensions. For the p-gradient the Kurosh subgroup theorems for amalgamated free products and HNN extensions will be used.

  5. Records of new or poorly known migratory birds from Laguna del Otun, Los Nevados National Natural Park, Risaralda, Colombia

    International Nuclear Information System (INIS)

    Acevedo Charry, Orlando; Matta Camacho, Nubia E; Moncada Alvarez, Ligia Ines

    2013-01-01

    Colombia is important for migratory birds. Despite this, we do not know where they are during their crossing or residency in the country, and which species use paramo. We registered new migratory bird species for Laguna Del Otun, immersed in a complex of wetlands declared a Ramsar site since 2008. The lagoon is located in the Los Nevados National Natural Park at 3932 m asl, in paramo ecosystems of the Central Andes of Colombia. During five field trips between 2010-2012 we recorded four new migratory bird species for the park: Anas acuta, Pandion haliaetus, Riparia riparia, and Dendroica petechia. We also registered an altitudinal range extension for two additional migratory species which had only been recorded below 3500 m: Tringa flavipes and Hirundo rustica. These findings suggest these species could tolerate high mountain conditions and use the paramo. It's needed inquiry about migratory dynamics and high mountain habitat use by migratory birds.

  6. Preconditioning the modified conjugate gradient method ...

    African Journals Online (AJOL)

    In this paper, the convergence analysis of the conventional conjugate Gradient method was reviewed. And the convergence analysis of the modified conjugate Gradient method was analysed with our extension on preconditioning the algorithm. Convergence of the algorithm is a function of the condition number of M-1A.

  7. Structures and Strength of Gradient Nanostructures

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

    distance from the surface forming a gradient structure. In this study [2], by shot peening of a low carbon steel a gradient structure has been produced extending to about 1 mm below the surface. A number of strengthening mechanisms have been analyzed as a basis for a calculation of the stress and strain...

  8. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2002-01-01

    By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter...

  9. Ultra-high gradient compact accelerator developments

    NARCIS (Netherlands)

    Brussaard, G.J.H.; Wiel, van der M.J.

    2004-01-01

    Continued development of relatively compact, although not quite 'table-top', lasers with peak powers in the range up to 100 TW has enabled laser-plasma-based acceleration experiments with amazing gradients of up to 1 TV/m. In order to usefully apply such gradients to 'controlled' acceleration,

  10. An Inexpensive Digital Gradient Controller for HPLC.

    Science.gov (United States)

    Brady, James E.; Carr, Peter W.

    1983-01-01

    Use of gradient elution techniques in high performance liquid chromatography (HPLC) is often essential for direct separation of complex mixtures. Since most commercial controllers have features that are of marginal value for instructional purposes, a low-cost controller capable of illustrating essential features of gradient elution was developed.…

  11. 40 CFR 230.25 - Salinity gradients.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Salinity gradients. 230.25 Section 230.25 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING SECTION 404(b... Physical and Chemical Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity...

  12. Microinstabilities in weak density gradient tokamak systems

    International Nuclear Information System (INIS)

    Tang, W.M.; Rewoldt, G.; Chen, L.

    1986-04-01

    A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient

  13. Patterns of macromycete community assemblage along an elevation gradient: options for fungal gradient and metacommunity analyse

    Science.gov (United States)

    Marko Gómez-Hernández; Guadalupe Williams-Linera; Roger Guevara; D. Jean Lodge

    2012-01-01

    Gradient analysis is rarely used in studies of fungal communities. Data on macromycetes from eight sites along an elevation gradient in central Veracruz, Mexico, were used to demonstrate methods for gradient analysis that can be applied to studies of communities of fungi. Selected sites from 100 to 3,500 m altitude represent tropical dry forest, tropical montane cloud...

  14. Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

    International Nuclear Information System (INIS)

    Ren, Y.; Kaye, S.M.; Mazzucato, E.; Guttenfelder, W.; Bell, R.E.; Domier, C.W.; LeBlanc, B.P.; Lee, K.C.; Luhmann, N.C. Jr.; Smith, D.R.; Yuh, H.

    2011-01-01

    In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k (perpendicular) ρ s ∼< 10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

  15. Dual fuel gradients in uranium silicide plates

    Energy Technology Data Exchange (ETDEWEB)

    Pace, B.W. [Babock and Wilcox, Lynchburg, VA (United States)

    1997-08-01

    Babcock & Wilcox has been able to achieve dual gradient plates with good repeatability in small lots of U{sub 3}Si{sub 2} plates. Improvements in homogeneity and other processing parameters and techniques have allowed the development of contoured fuel within the cladding. The most difficult obstacles to overcome have been the ability to evaluate the bidirectional fuel loadings in comparison to the perfect loading model and the different methods of instilling the gradients in the early compact stage. The overriding conclusion is that to control the contour of the fuel, a known relationship between the compact, the frames and final core gradient must exist. Therefore, further development in the creation and control of dual gradients in fuel plates will involve arriving at a plausible gradient requirement and building the correct model between the compact configuration and the final contoured loading requirements.

  16. Approximate error conjugation gradient minimization methods

    Science.gov (United States)

    Kallman, Jeffrey S

    2013-05-21

    In one embodiment, a method includes selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, calculating an approximate error using the subset of rays, and calculating a minimum in a conjugate gradient direction based on the approximate error. In another embodiment, a system includes a processor for executing logic, logic for selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, logic for calculating an approximate error using the subset of rays, and logic for calculating a minimum in a conjugate gradient direction based on the approximate error. In other embodiments, computer program products, methods, and systems are described capable of using approximate error in constrained conjugate gradient minimization problems.

  17. Protein gradient films of fibroin and gelatine.

    Science.gov (United States)

    Claussen, Kai U; Lintz, Eileen S; Giesa, Reiner; Schmidt, Hans-Werner; Scheibel, Thomas

    2013-10-01

    Gradients are a natural design principle in biological systems that are used to diminish stress concentration where materials of differing mechanical properties connect. An interesting example of a natural gradient material is byssus, which anchors mussels to rocks and other hard substrata. Building upon previous work with synthetic polymers and inspired by byssal threads, protein gradient films are cast using glycerine-plasticized gelatine and fibroin exhibiting a highly reproducible and smooth mechanical gradient, which encompasses a large range of modulus from 160 to 550 MPa. The reproducible production of biocompatible gradient films represents a first step towards medical applications. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Il dono del racconto

    DEFF Research Database (Denmark)

    Polito, Paola

    1998-01-01

    L'articolo indaga a vari livelli strutturali del romanzo "Il coraggio del pettirosso" (rete metaforica, dialogismo diegetico, dialogismo come fenomeno di voce, strategie discorsive messe in atto dalla voce narrante, stile colloquiale) la complessa realizzazione testuale del genere narrativo...

  19. Gradient pre-emphasis to counteract first-order concomitant fields on asymmetric MRI gradient systems.

    Science.gov (United States)

    Tao, Shengzhen; Weavers, Paul T; Trzasko, Joshua D; Shu, Yunhong; Huston, John; Lee, Seung-Kyun; Frigo, Louis M; Bernstein, Matt A

    2017-06-01

    To develop a gradient pre-emphasis scheme that prospectively counteracts the effects of the first-order concomitant fields for any arbitrary gradient waveform played on asymmetric gradient systems, and to demonstrate the effectiveness of this approach using a real-time implementation on a compact gradient system. After reviewing the first-order concomitant fields that are present on asymmetric gradients, we developed a generalized gradient pre-emphasis model assuming arbitrary gradient waveforms to counteract their effects. A numerically straightforward, easily implemented approximate solution to this pre-emphasis problem was derived that was compatible with the current hardware infrastructure of conventional MRI scanners for eddy current compensation. The proposed method was implemented on the gradient driver subsystem, and its real-time use was tested using a series of phantom and in vivo data acquired from two-dimensional Cartesian phase-difference, echo-planar imaging, and spiral acquisitions. The phantom and in vivo results demonstrated that unless accounted for, first-order concomitant fields introduce considerable phase estimation error into the measured data and result in images with spatially dependent blurring/distortion. The resulting artifacts were effectively prevented using the proposed gradient pre-emphasis. We have developed an efficient and effective gradient pre-emphasis framework to counteract the effects of first-order concomitant fields of asymmetric gradient systems. Magn Reson Med 77:2250-2262, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  20. Intracellular chemical gradients: morphing principle in bacteria

    Directory of Open Access Journals (Sweden)

    Endres Robert G

    2012-09-01

    Full Text Available Abstract Advances in computational biology allow systematic investigations to ascertain whether internal chemical gradients can be maintained in bacteria – an open question at the resolution limit of fluorescence microscopy. While it was previously believed that the small bacterial cell size and fast diffusion in the cytoplasm effectively remove any such gradient, a new computational study published in BMC Biophysics supports the emerging view that gradients can exist. The study arose from the recent observation that phosphorylated CtrA forms a gradient prior to cell division in Caulobacter crescentus, a bacterium known for its complicated cell cycle. Tropini et al. (2012 postulate that such gradients can provide an internal chemical compass, directing protein localization, cell division and cell development. More specifically, they describe biochemical and physical constraints on the formation of such gradients and explore a number of existing bacterial cell morphologies. These chemical gradients may limit in vitro analyses, and may ensure timing control and robustness to fluctuations during critical stages in cell development.

  1. The straight-chain lipid biomarker composition of plant species responsible for the dominant biomass production along two altitudinal transects in the Ecuadorian Andes

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, Boris; Nierop, Klaas G.J.; Verstraten, Jacobus M.; Cleef, Antoine M. [Amsterdam Univ., Center for Geo-ecological Research (ICG), Amsterdam (Netherlands); Hageman, Jos A. [Amsterdam Univ., Swammerdam Inst. for Life Sciences (SILS), Amsterdam (Netherlands)

    2006-11-15

    For a detailed reconstruction of historic upper forest line (UFL) positions, new proxies in addition to traditional pollen and vegetation analyses are needed. If the straight-chain lipid composition in plant leaves and roots is specific enough to allow distinction, their records in soils and peat bogs might be used for this purpose. We tested for such distinctiveness by analyzing the n-alkane, n-alcohol, n-aldehyde and wax ester composition in lipid extracts from the leaves and roots of the 19 plant species responsible for the dominant biomass input into soils and peat bogs along two altitudinal transects in the Ecuadorian Andes. We found the combined n-alkane and n-alcohol composition of the leaves of the studied plants to be unique enough in theory to allow for a distinction of the various plant species. The extractable straight-chain lipid concentrations in the roots were generally much lower than in the leaves of the same species, and were in many cases less specific. The n-fatty acids, n-aldehydes and wax ester compositions in leaves as well as roots appeared to be less suited as biomarkers, due to a lower specificity of the n-fatty acids and the absence of the n-aldehydes and wax ester from a significant number of plant species. Furthermore, using cluster analysis we found the combination of n-alkanes and n-alcohols from leaves to give the most meaningful clustering from the point of view of an UFL reconstruction, with all but one paramo grassland species and all but one peat bog species clustering separately from forest species. In addition, a large C{sub 31} /C{sub 27} n-alkane ratio as well as a large C{sub 26} /C{sub 30} n-alcohol ratio were found to be indicative of paramo vegetation (grasses). Both clustering and ratios can help reconstruct past UFL positions if discerning individual species from soil or peat records proves unfeasible. The preservation of the straight-chain lipid signal was tested in soil and peat samples from the study area predating

  2. Sound beam manipulation based on temperature gradients

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Feng [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); School of Physics & Electronic Engineering, Changshu Institute of Technology, Changshu 215500 (China); Quan, Li; Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-10-28

    Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking.

  3. del cambio

    Directory of Open Access Journals (Sweden)

    Alejandro Canales

    2006-01-01

    Full Text Available El artículo analiza las propuestas y los compromisos en materia de cobertura y de financiamiento en el periodo 2000-2006. En particular, revisa las modificaciones y los ajustes de los tres principales documentos en los que se expresaron las iniciativas: el de la Asociación Nacional de Universidades e Instituciones de Educación Superior, el del equipo de la transición y el programa sectorial. Los resultados muestran que las cifras de atención a la demanda educativa e inversión quedaron lejos de las metas autoimpuestas por el gobierno federal y que será necesario realizar mayores esfuerzos para atender tales desafíos.

  4. Unimodal and crossmodal gradients of spatial attention

    DEFF Research Database (Denmark)

    Föcker, J.; Hötting, K.; Gondan, Matthias

    2010-01-01

    Behavioral and event-related potential (ERP) studies have shown that spatial attention is gradually distributed around the center of the attentional focus. The present study compared uni- and crossmodal gradients of spatial attention to investigate whether the orienting of auditory and visual...... spatial attention is based on modality specific or supramodal representations of space. Auditory and visual stimuli were presented from five speaker locations positioned in the right hemifield. Participants had to attend to the innermost or outmost right position in order to detect either visual...... or auditory deviant stimuli. Detection rates and event-related potentials (ERPs) indicated that spatial attention is distributed as a gradient. Unimodal spatial ERP gradients correlated with the spatial resolution of the modality. Crossmodal spatial gradients were always broader than the corresponding...

  5. Full Gradient Solution to Adaptive Hybrid Control

    Science.gov (United States)

    Bean, Jacob; Schiller, Noah H.; Fuller, Chris

    2017-01-01

    This paper focuses on the adaptation mechanisms in adaptive hybrid controllers. Most adaptive hybrid controllers update two filters individually according to the filtered reference least mean squares (FxLMS) algorithm. Because this algorithm was derived for feedforward control, it does not take into account the presence of a feedback loop in the gradient calculation. This paper provides a derivation of the proper weight vector gradient for hybrid (or feedback) controllers that takes into account the presence of feedback. In this formulation, a single weight vector is updated rather than two individually. An internal model structure is assumed for the feedback part of the controller. The full gradient is equivalent to that used in the standard FxLMS algorithm with the addition of a recursive term that is a function of the modeling error. Some simulations are provided to highlight the advantages of using the full gradient in the weight vector update rather than the approximation.

  6. Continuous spray forming of functionally gradient materials

    International Nuclear Information System (INIS)

    McKechnie, T.N.; Richardson, E.H.

    1995-01-01

    Researchers at Plasma Processes Inc. have produced a Functional Gradient Material (FGM) through advanced vacuum plasma spray processing for high heat flux applications. Outlined in this paper are the manufacturing methods used to develop a four component functional gradient material of copper, tungsten, boron, and boron nitride. The FGM was formed with continuous gradients and integral cooling channels eliminating bondlines and providing direct heat transfer from the high temperature exposed surface to a cooling medium. Metallurgical and x-ray diffraction analyses of the materials formed through innovative VPS (vacuum plasma spray) processing are also presented. Applications for this functional gradient structural material range from fusion reactor plasma facing components to missile nose cones to boilers

  7. Vegetation patterns and environmental gradients in Benin

    NARCIS (Netherlands)

    Adomou, A.

    2005-01-01

    Key words: West Africa, Benin, vegetation patterns, floristic areas, phytogeography, chorology, floristic gradients, climatic factors, water availability, Dahomey Gap, threatened plants, biodiversity, conservation.Understanding plant species distribution patterns and the underlying factors is a

  8. Coreless Concept for High Gradient Induction Cell

    International Nuclear Information System (INIS)

    Krasnykh, Anatoly

    2008-01-01

    An induction linac cell for a high gradient is discussed. The proposed solid state coreless approach for the induction linac topology (SLIM(reg s ign)) is based on nanosecond mode operation. This mode may have an acceleration gradient comparable with gradients of rf- accelerator structures. The discussed induction system has the high electric efficiency. The key elements are a solid state semiconductor switch and a high electric density dielectric with a thin section length. The energy in the induction system is storied in the magnetic field. The nanosecond current break-up produces the high voltage. The induced voltage is used for acceleration. This manner of an operation allows the use of low voltage elements in the booster part and achieves a high accelerating gradient. The proposed topology was tested in POP (proof of principle) experiments

  9. Flexoelectricity: strain gradient effects in ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Ma Wenhui [Department of Physics, Shantou Unversity, Shantou, Guangdong 515063 (China)

    2007-12-15

    Mechanical strain gradient induced polarization effect or flexoelectricity in perovskite-type ferroelectric and relaxor ferroelectric ceramics was investigated. The flexoelectric coefficients measured at room temperature ranged from about 1 {mu} C m{sup -1} for lead zirconate titanate to 100 {mu} C m{sup -1} for barium strontium titanate. Flexoelectric effects were discovered to be sensitive to chemical makeup, phase symmetry, and domain structures. Based on phenomenological discussion and experimental data on flexoelectricity, the present study proposed that mechanical strain gradient field could influence polarization responses in a way analogous to electric field. Flexoelectric coefficients were found to be nonlinearly enhanced by dielectric permittivity and strain gradient. Interfacial mismatch in epitaxial thin films can give rise to high strain gradients, enabling flexoelectric effects to make a significant impact in properly engineered ferroelectric heterostructure systems.

  10. On fracture in finite strain gradient plasticity

    DEFF Research Database (Denmark)

    Martínez Pañeda, Emilio; Niordson, Christian Frithiof

    2016-01-01

    In this work a general framework for damage and fracture assessment including the effect of strain gradients is provided. Both mechanism-based and phenomenological strain gradient plasticity (SGP) theories are implemented numerically using finite deformation theory and crack tip fields are invest......In this work a general framework for damage and fracture assessment including the effect of strain gradients is provided. Both mechanism-based and phenomenological strain gradient plasticity (SGP) theories are implemented numerically using finite deformation theory and crack tip fields...... are investigated. Differences and similarities between the two approaches within continuum SGP modeling are highlighted and discussed. Local strain hardening promoted by geometrically necessary dislocations (GNDs) in the vicinity of the crack leads to much higher stresses, relative to classical plasticity...... in the multiple parameter version of the phenomenological SGP theory. Since this also dominates the mechanics of indentation testing, results suggest that length parameters characteristic of mode I fracture should be inferred from nanoindentation....

  11. TEK twisted gradient flow running coupling

    CERN Document Server

    Pérez, Margarita García; Keegan, Liam; Okawa, Masanori

    2014-01-01

    We measure the running of the twisted gradient flow coupling in the Twisted Eguchi-Kawai (TEK) model, the SU(N) gauge theory on a single site lattice with twisted boundary conditions in the large N limit.

  12. Integral Field Spectroscopy Surveys: Oxygen Abundance Gradients

    Science.gov (United States)

    Sánchez, S. F.; Sánchez-Menguiano, L.

    2017-07-01

    We present here the recent results on our understanding of oxygen abundance gradients derived using Integral Field Spectroscopic surveys. In particular we analyzed more than 2124 datacubes corresponding to individual objects observed by the CALIFA (˜ 734 objects) and the public data by MaNGA (˜ 1390 objects), deriving the oxygen abundance gradient for each galaxy. We confirm previous results that indicate that the shape of this gradient is very similar for all galaxies with masses above 109.5M⊙, presenting in average a very similar slope of ˜ -0.04 dex within 0.5-2.0 re, with a possible drop in the inner regions (r109.5M⊙) the gradient seems to be flatter than for more massive ones. All these results agree with an inside-out growth of massive galaxies and indicate that low mass ones may still be growing in an outside in phase.

  13. Stability of gradient semigroups under perturbations

    Science.gov (United States)

    Aragão-Costa, E. R.; Caraballo, T.; Carvalho, A. N.; Langa, J. A.

    2011-07-01

    In this paper we prove that gradient-like semigroups (in the sense of Carvalho and Langa (2009 J. Diff. Eqns 246 2646-68)) are gradient semigroups (possess a Lyapunov function). This is primarily done to provide conditions under which gradient semigroups, in a general metric space, are stable under perturbation exploiting the known fact (see Carvalho and Langa (2009 J. Diff. Eqns 246 2646-68)) that gradient-like semigroups are stable under perturbation. The results presented here were motivated by the work carried out in Conley (1978 Isolated Invariant Sets and the Morse Index (CBMS Regional Conference Series in Mathematics vol 38) (RI: American Mathematical Society Providence)) for groups in compact metric spaces (see also Rybakowski (1987 The Homotopy Index and Partial Differential Equations (Universitext) (Berlin: Springer)) for the Morse decomposition of an invariant set for a semigroup on a compact metric space).

  14. Stability of gradient semigroups under perturbations

    International Nuclear Information System (INIS)

    Aragão-Costa, E R; Carvalho, A N; Caraballo, T; Langa, J A

    2011-01-01

    In this paper we prove that gradient-like semigroups (in the sense of Carvalho and Langa (2009 J. Diff. Eqns 246 2646–68)) are gradient semigroups (possess a Lyapunov function). This is primarily done to provide conditions under which gradient semigroups, in a general metric space, are stable under perturbation exploiting the known fact (see Carvalho and Langa (2009 J. Diff. Eqns 246 2646–68)) that gradient-like semigroups are stable under perturbation. The results presented here were motivated by the work carried out in Conley (1978 Isolated Invariant Sets and the Morse Index (CBMS Regional Conference Series in Mathematics vol 38) (RI: American Mathematical Society Providence)) for groups in compact metric spaces (see also Rybakowski (1987 The Homotopy Index and Partial Differential Equations (Universitext) (Berlin: Springer)) for the Morse decomposition of an invariant set for a semigroup on a compact metric space)

  15. Gradient High Performance Liquid Chromatography Method ...

    African Journals Online (AJOL)

    Purpose: To develop a gradient high performance liquid chromatography (HPLC) method for the simultaneous determination of phenylephrine (PHE) and ibuprofen (IBU) in solid ..... nimesulide, phenylephrine. Hydrochloride, chlorpheniramine maleate and caffeine anhydrous in pharmaceutical dosage form. Acta Pol.

  16. Ultimate gradient in solid-state accelerators

    International Nuclear Information System (INIS)

    Whittum, D.H.

    1998-08-01

    The authors recall the motivation for research in high-gradient acceleration and the problems posed by a compact collider. They summarize the phenomena known to appear in operation of a solid-state structure with large fields, and research relevant to the question of the ultimate gradient. They take note of new concepts, and examine one in detail, a miniature particle accelerator based on an active millimeter-wave circuit and parallel particle beams

  17. Quasistatic nonlinear viscoelasticity and gradient flows

    OpenAIRE

    Ball, John M.; Şengül, Yasemin

    2014-01-01

    We consider the equation of motion for one-dimensional nonlinear viscoelasticity of strain-rate type under the assumption that the stored-energy function is λ-convex, which allows for solid phase transformations. We formulate this problem as a gradient flow, leading to existence and uniqueness of solutions. By approximating general initial data by those in which the deformation gradient takes only finitely many values, we show that under suitable hypotheses on the stored-energy function the d...

  18. Tolman temperature gradients in a gravitational field

    OpenAIRE

    Santiago, Jessica; Visser, Matt

    2018-01-01

    Tolman's relation for the temperature gradient in an equilibrium self-gravitating general relativistic fluid is broadly accepted within the general relativity community. However, the concept of temperature gradients in thermal equilibrium continues to cause confusion in other branches of physics, since it contradicts naive versions of the laws of classical thermodynamics. In this paper we discuss the crucial role of the universality of free fall, and how thermodynamics emphasises the great di...

  19. Tearing modes with pressure gradient effect in pair plasmas

    International Nuclear Information System (INIS)

    Cai Huishan; Li Ding; Zheng Jian

    2009-01-01

    The general dispersion relation of tearing mode with pressure gradient effect in pair plasmas is derived analytically. If the pressure gradients of positron and electron are not identical in pair plasmas, the pressure gradient has significant influence at tearing mode in both collisionless and collisional regimes. In collisionless regime, the effects of pressure gradient depend on its magnitude. For small pressure gradient, the growth rate of tearing mode is enhanced by pressure gradient. For large pressure gradient, the growth rate is reduced by pressure gradient. The tearing mode can even be stabilized if pressure gradient is large enough. In collisional regime, the growth rate of tearing mode is reduced by the pressure gradient. While the positron and electron have equal pressure gradient, tearing mode is not affected by pressure gradient in pair plasmas.

  20. La superaci??n del modelo del ??ngel del hogar:

    OpenAIRE

    Hurtado Mu??oz, M??nica

    2012-01-01

    La Tesis Doctoral titulada "La superaci??n del modelo del "??ngel del hogar". Recuperaci??n de la escritora Leonor Canalejas y Fustegueras (1869-1945)" aborda, en primer lugar, un an??lisis sociol??gico de las circunstancias que rodearon a la mujer espa??ola en el cambio de siglo en el ??mbito social y educativo, en un intento de esclarecer las caracter??sticas propias del contexto en el que la mujer accede a la intelectualidad en general y a la literatura en particular. Esta parte concluye q...

  1. Magnetoelectric Transverse Gradient Sensor with High Detection Sensitivity and Low Gradient Noise

    OpenAIRE

    Zhang, Mingji; Or, Siu Wing

    2017-01-01

    We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME vo...

  2. Full magnetic gradient tensor from triaxial aeromagnetic gradient measurements: Calculation and application

    Science.gov (United States)

    Luo, Yao; Wu, Mei-Ping; Wang, Ping; Duan, Shu-Ling; Liu, Hao-Jun; Wang, Jin-Long; An, Zhan-Feng

    2015-09-01

    The full magnetic gradient tensor (MGT) refers to the spatial change rate of the three field components of the geomagnetic field vector along three mutually orthogonal axes. The tensor is of use to geological mapping, resources exploration, magnetic navigation, and others. However, it is very difficult to measure the full magnetic tensor gradient using existing engineering technology. We present a method to use triaxial aeromagnetic gradient measurements for deriving the full MGT. The method uses the triaxial gradient data and makes full use of the variation of the magnetic anomaly modulus in three dimensions to obtain a self-consistent magnetic tensor gradient. Numerical simulations show that the full MGT data obtained with the proposed method are of high precision and satisfy the requirements of data processing. We selected triaxial aeromagnetic gradient data from the Hebei Province for calculating the full MGT. Data processing shows that using triaxial tensor gradient data allows to take advantage of the spatial rate of change of the total field in three dimensions and suppresses part of the independent noise in the aeromagnetic gradient. The calculated tensor components have improved resolution, and the transformed full tensor gradient satisfies the requirement of geological mapping and interpretation.

  3. Examining Environmental Gradients with satellite data in permafrost regions - the current state of the ESA GlobPermafrost initative

    Science.gov (United States)

    Grosse, G.; Bartsch, A.; Kääb, A.; Westermann, S.; Strozzi, T.; Wiesmann, A.; Duguay, C. R.; Seifert, F. M.; Obu, J.; Nitze, I.; Heim, B.; Haas, A.; Widhalm, B.

    2017-12-01

    Permafrost cannot be directly detected from space, but many surface features of permafrost terrains and typical periglacial landforms are observable with a variety of EO sensors ranging from very high to medium resolution at various wavelengths. In addition, landscape dynamics associated with permafrost changes and geophysical variables relevant for characterizing the state of permafrost, such as land surface temperature or freeze-thaw state can be observed with spaceborne Earth Observation. Suitable regions to examine environmental gradients across the Arctic have been defined in a community white paper (Bartsch et al. 2014, hdl:10013/epic.45648.d001). These transects have been revised and adjusted within the DUE GlobPermafrost initiative of the European Space Agency. The ESA DUE GlobPermafrost project develops, validates and implements Earth Observation (EO) products to support research communities and international organisations in their work on better understanding permafrost characteristics and dynamics. Prototype product cases will cover different aspects of permafrost by integrating in situ measurements of subsurface and surface properties, Earth Observation, and modelling to provide a better understanding of permafrost today. The project will extend local process and permafrost monitoring to broader spatial domains, support permafrost distribution modelling, and help to implement permafrost landscape and feature mapping in a GIS framework. It will also complement active layer and thermal observing networks. Both lowland (latitudinal) and mountain (altitudinal) permafrost issues are addressed. The status of the Permafrost Information System and first results will be presented. Prototypes of GlobPermafrost datasets include: Modelled mean annual ground temperature by use of land surface temperature and snow water equivalent from satellites Land surface characterization including shrub height, land cover and parameters related to surface roughness Trends from

  4. Income inequality and socioeconomic gradients in mortality.

    Science.gov (United States)

    Wilkinson, Richard G; Pickett, Kate E

    2008-04-01

    We investigated whether the processes underlying the association between income inequality and population health are related to those responsible for the socioeconomic gradient in health and whether health disparities are smaller when income differences are narrower. We used multilevel models in a regression analysis of 10 age- and cause-specific US county mortality rates on county median household incomes and on state income inequality. We assessed whether mortality rates more closely related to county income were also more closely related to state income inequality. We also compared mortality gradients in more- and less-equal states. Mortality rates more strongly associated with county income were more strongly associated with state income inequality: across all mortality rates, r= -0.81; P=.004. The effect of state income inequality on the socioeconomic gradient in health varied by cause of death, but greater equality usually benefited both wealthier and poorer counties. Although mortality rates with steep socioeconomic gradients were more sensitive to income distribution than were rates with flatter gradients, narrower income differences benefit people in both wealthy and poor areas and may, paradoxically, do little to reduce health disparities.

  5. Jupiter's evolution with primordial composition gradients

    Science.gov (United States)

    Vazan, Allona; Helled, Ravit; Guillot, Tristan

    2018-02-01

    Recent formation and structure models of Jupiter suggest that the planet can have composition gradients and not be fully convective (adiabatic). This possibility directly affects our understanding of Jupiter's bulk composition and origin. In this Letter we present Jupiter's evolution with a primordial structure consisting of a relatively steep heavy-element gradient of 40 M⊕. We show that for a primordial structure with composition gradients, most of the mixing occurs in the outer part of the gradient during the early evolution (several 107 yr), leading to an adiabatic outer envelope (60% of Jupiter's mass). We find that the composition gradient in the deep interior persists, suggesting that 40% of Jupiter's mass can be non-adiabatic with a higher temperature than the one derived from Jupiter's atmospheric properties. The region that can potentially develop layered convection in Jupiter today is estimated to be limited to 10% of the mass. Movies associated to Figs. 1-3 are available at http://https://www.aanda.org

  6. Gradient dissimilation in Mongolian: Implications for diachrony

    DEFF Research Database (Denmark)

    Jatteau, Adèle; Hejná, Michaela

    2018-01-01

    This paper explores the implications of ‘gradient dissimilation’ (Jatteau & Hejná 2016) for the diachronic implementation of dissimilation. Since this sound change is usually considered as typically sporadic, lexically regular cases should result from lexical diffusion. In contrast with this ass......This paper explores the implications of ‘gradient dissimilation’ (Jatteau & Hejná 2016) for the diachronic implementation of dissimilation. Since this sound change is usually considered as typically sporadic, lexically regular cases should result from lexical diffusion. In contrast...... with this assumption, we explore the hypothesis that gradient dissimilation may represent the phonetic precursor of completed, regular dissimilatory processes. Such cases of dissimilation might then be reanalysed as Neogrammarian types of change. To assess this question, we gather and analyse new data from Halh...... Mongolian, a language reported to show gradient dissimilation (Svantesson et al. 2005), and compare it to two completed patterns of dissimilation reconstructed within the Mongolic family: Mongolian Chahar and Monguor. The results suggest that the gradient dissimilation in Halh may represent the phonetic...

  7. Gradient algorithm applied to laboratory quantum control

    International Nuclear Information System (INIS)

    Roslund, Jonathan; Rabitz, Herschel

    2009-01-01

    The exploration of a quantum control landscape, which is the physical observable as a function of the control variables, is fundamental for understanding the ability to perform observable optimization in the laboratory. For high control variable dimensions, trajectory-based methods provide a means for performing such systematic explorations by exploiting the measured gradient of the observable with respect to the control variables. This paper presents a practical, robust, easily implemented statistical method for obtaining the gradient on a general quantum control landscape in the presence of noise. In order to demonstrate the method's utility, the experimentally measured gradient is utilized as input in steepest-ascent trajectories on the landscapes of three model quantum control problems: spectrally filtered and integrated second harmonic generation as well as excitation of atomic rubidium. The gradient algorithm achieves efficiency gains of up to approximately three times that of the standard genetic algorithm and, as such, is a promising tool for meeting quantum control optimization goals as well as landscape analyses. The landscape trajectories directed by the gradient should aid in the continued investigation and understanding of controlled quantum phenomena.

  8. BURMEISTERA DIAZII(CAMPANULACEAE: LOBELIOIDEAE, UNA ESPECIE NUEVA DE LOS ANDES DE ANTIOQUIA, Y NOTAS ACERCA DEL NUEVO REGISTRO DE B. LOEJTNANTII PARA COLOMBIA

    Directory of Open Access Journals (Sweden)

    JAVIER GARZÓN VENEGAS

    2014-12-01

    Full Text Available Burmeistera diazii (Campanulaceae: Lobelioideae, de la Cordillera Central de Colombia, en la franja altitudinal entre 1,800 y 2,750 m en los municipios de Sonsón y Guatapé (Antioquia, es descrita como una especie nueva. Se discuten en detalle las semejanzas morfológicas con sus especies afines (B. obtusifolia, de Costa Rica y Panamá, B. killipii y B. serraniaguae, de Colombia y B. crassifolia y B. loejtnantii, de Colombia y Ecuador, las cuales se caracterizan por tener hojas ovadas a ovado-lanceoladas, pedúnculo ebracteado y lóbulos del cáliz largos. Se registra B. loejtnantii por primera vez para la flora de Colombia.

  9. Diversity and feeding strategies of soil microfauna along elevation gradients in Himalayan cold deserts.

    Directory of Open Access Journals (Sweden)

    Miloslav Devetter

    Full Text Available High-elevation cold deserts in Tibet and Himalaya are one of the most extreme environments. One consequence is that the diversity of macrofauna in this environment is often limited, and soil microorganisms have a more influential role in governing key surface and subsurface bioprocesses. High-elevation soil microfauna represent important components of cold ecosystems and dominant consumers of microbial communities. Still little is known about their diversity and distribution on the edge of their reproductive and metabolic abilities. In this study, we disentangle the impact of elevation and soil chemistry on diversity and distribution of rotifers, nematodes and tardigrades and their most frequent feeding strategies (microbial filter-feeders, bacterivores, fungivores, root-fungal feeders, omnivores along two contrasting altitudinal gradients in Indian NW Himalaya (Zanskar transect from 3805 to 4714 m a.s.l. and southwestern Tibet (Tso Moriri transect from 4477 to 6176 m a.s.l., using a combination of multivariate analysis, variation partitioning and generalized additive models. Zanskar transect had higher precipitation, soil moisture, organic matter and available nutrients than dry Tso Moriri transect. In total, 40 species of nematodes, 19 rotifers and 1 tardigrade were discovered. Species richness and total abundance of rotifers and nematodes showed mid-elevation peaks in both investigated transects. The optimum for rotifers was found at higher elevation than for nematodes. Diversity and distribution of soil microfauna was best explained by soil nitrogen, phosphorus and organic matter. More fertile soils hosted more diverse and abundant faunal communities. In Tso Moriri, bacterivores represented 60% of all nematodes, fungivores 35%, root-fungal feeders 1% and omnivores 3%. For Zanskar the respective proportions were 21%, 13%, 56% and 9%. Elevational optima of different feeding strategies occurred in Zanskar in one elevation zone (4400-4500 m

  10. An implicit tensorial gradient plasticity model - formulation and comparison with a scalar gradient model

    NARCIS (Netherlands)

    Poh, L.H.; Peerlings, R.H.J.; Geers, M.G.D.; Swaddiwudhipong, S.

    2011-01-01

    Many rate-independent models for metals utilize the gradient of effective plastic strain to capture size-dependent behavior. This enhancement, sometimes termed as "explicit" gradient formulation, requires higher-order tractions to be imposed on the evolving elasto-plastic boundary and the resulting

  11. Evidence of counter-gradient growth in western pond turtles (Actinemys marmorata) across thermal gradients

    Science.gov (United States)

    Snover, Melissa; Adams, Michael J.; Ashton, Donald T.; Bettaso, Jamie B.; Welsh, Hartwell H.

    2015-01-01

    Counter-gradient growth, where growth per unit temperature increases as temperature decreases, can reduce the variation in ectothermic growth rates across environmental gradients. Understanding how ectothermic species respond to changing temperatures is essential to their conservation and management due to human-altered habitats and changing climates.

  12. Momentum-weighted conjugate gradient descent algorithm for gradient coil optimization.

    Science.gov (United States)

    Lu, Hanbing; Jesmanowicz, Andrzej; Li, Shi-Jiang; Hyde, James S

    2004-01-01

    MRI gradient coil design is a type of nonlinear constrained optimization. A practical problem in transverse gradient coil design using the conjugate gradient descent (CGD) method is that wire elements move at different rates along orthogonal directions (r, phi, z), and tend to cross, breaking the constraints. A momentum-weighted conjugate gradient descent (MW-CGD) method is presented to overcome this problem. This method takes advantage of the efficiency of the CGD method combined with momentum weighting, which is also an intrinsic property of the Levenberg-Marquardt algorithm, to adjust step sizes along the three orthogonal directions. A water-cooled, 12.8 cm inner diameter, three axis torque-balanced gradient coil for rat imaging was developed based on this method, with an efficiency of 2.13, 2.08, and 4.12 mT.m(-1).A(-1) along X, Y, and Z, respectively. Experimental data demonstrate that this method can improve efficiency by 40% and field uniformity by 27%. This method has also been applied to the design of a gradient coil for the human brain, employing remote current return paths. The benefits of this design include improved gradient field uniformity and efficiency, with a shorter length than gradient coil designs using coaxial return paths. Copyright 2003 Wiley-Liss, Inc.

  13. Inversion gradients for acoustic VTI wavefield tomography

    KAUST Repository

    Li, Vladimir; Wang, Hui; Tsvankin, Ilya; Dí az, Esteban; Alkhalifah, Tariq Ali

    2017-01-01

    Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a generalized pseudospectral operator based on a separable approximation for the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified image-power objective functions. We also obtain the gradient expressions for a data-domain objective function that can more easily incorporate borehole information necessary for stable VTI velocity analysis. These gradients are similar to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations but the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show the potential advantages of the modified image-power objective function in estimating the anellipticity parameter η.

  14. Gradient pattern analysis applied to galaxy morphology

    Science.gov (United States)

    Rosa, R. R.; de Carvalho, R. R.; Sautter, R. A.; Barchi, P. H.; Stalder, D. H.; Moura, T. C.; Rembold, S. B.; Morell, D. R. F.; Ferreira, N. C.

    2018-06-01

    Gradient pattern analysis (GPA) is a well-established technique for measuring gradient bilateral asymmetries of a square numerical lattice. This paper introduces an improved version of GPA designed for galaxy morphometry. We show the performance of the new method on a selected sample of 54 896 objects from the SDSS-DR7 in common with Galaxy Zoo 1 catalogue. The results suggest that the second gradient moment, G2, has the potential to dramatically improve over more conventional morphometric parameters. It separates early- from late-type galaxies better (˜ 90 per cent) than the CAS system (C˜ 79 per cent, A˜ 50 per cent, S˜ 43 per cent) and a benchmark test shows that it is applicable to hundreds of thousands of galaxies using typical processing systems.

  15. Dynamics of gradient formation by intracellular shuttling

    Energy Technology Data Exchange (ETDEWEB)

    Berezhkovskii, Alexander M. [Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892 (United States); Shvartsman, Stanislav Y. [Department of Chemical and Biological Engineering and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544 (United States)

    2015-08-21

    A number of important cellular functions rely on the formation of intracellular protein concentration gradients. Experimental studies discovered a number of mechanisms for the formation of such gradients. One of the mechanisms relies on the intracellular shuttling of a protein that interconverts between the two states with different diffusivities, under the action of two enzymes, one of which is localized to the plasma membrane, whereas the second is uniformly distributed in the cytoplasm. Recent work reported an analytical solution for the steady state gradient in this mechanism, obtained in the framework of a one-dimensional reaction-diffusion model. Here, we study the dynamics in this model and derive analytical expressions for the Laplace transforms of the time-dependent concentration profiles in terms of elementary transcendental functions. Inverting these transforms numerically, one can obtain time-dependent concentration profiles of the two forms of the protein.

  16. Relativistic klystrons for high-gradient accelerators

    International Nuclear Information System (INIS)

    Westenskow, G.A.; Aalberts, D.P.; Boyd, J.K.; Deis, G.A.; Houck, T.L.; Orzechowski, T.J.; Ryne, R.D.; Yu, S.S.; Allen, M.A.; Callin, R.S.; Deruyter, H.; Eppley, K.R.; Fant, K.S.; Fowkes, W.R.; Hoag, H.A.; Koontz, R.F.; Lavine, T.L.; Loew, G.A.; Miller, R.H.; Ruth, R.D.; Vlieks, A.E.; Wang, J.W.; Hopkins, D.B.; Sessler, A.M.; Haimson, J.; Mecklenburg, B.

    1991-01-01

    Experimental work is being performed by collaborators at LLNL, SLAC, and LBL to investigate relativistic klystrons as a possible rf power source for future high-gradient accelerators. The authors have learned how to overcome their previously reported problem of high power rf pulse shortening and have achieved peak rf power levels of 330 MW using an 11.4-GHz high-gain tube with multiple output structures. In these experiments the rf pulse is of the same duration as the beam current pulse. In addition, experiments have been performed on two short sections of a high-gradient accelerator using the rf power from a relativistic klystron. An average accelerating gradient of 84 MV/m has been achieved with 80-MW of rf power

  17. Substrate curvature gradient drives rapid droplet motion.

    Science.gov (United States)

    Lv, Cunjing; Chen, Chao; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

    2014-07-11

    Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of 0.42  m/s, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over 100  m/s on tapered surfaces.

  18. Nonlinear conjugate gradient methods in micromagnetics

    Directory of Open Access Journals (Sweden)

    J. Fischbacher

    2017-04-01

    Full Text Available Conjugate gradient methods for energy minimization in micromagnetics are compared. The comparison of analytic results with numerical simulation shows that standard conjugate gradient method may fail to produce correct results. A method that restricts the step length in the line search is introduced, in order to avoid this problem. When the step length in the line search is controlled, conjugate gradient techniques are a fast and reliable way to compute the hysteresis properties of permanent magnets. The method is applied to investigate demagnetizing effects in NdFe12 based permanent magnets. The reduction of the coercive field by demagnetizing effects is μ0ΔH = 1.4 T at 450 K.

  19. Inversion gradients for acoustic VTI wavefield tomography

    KAUST Repository

    Li, Vladimir

    2017-03-21

    Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a generalized pseudospectral operator based on a separable approximation for the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified image-power objective functions. We also obtain the gradient expressions for a data-domain objective function that can more easily incorporate borehole information necessary for stable VTI velocity analysis. These gradients are similar to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations but the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show the potential advantages of the modified image-power objective function in estimating the anellipticity parameter η.

  20. Vertical gradients of sunspot magnetic fields

    Science.gov (United States)

    Hagyard, M. J.; Teuber, D.; West, E. A.; Tandberg-Hanssen, E.; Henze, W., Jr.; Beckers, J. M.; Bruner, M.; Hyder, C. L.; Woodgate, B. E.

    1983-01-01

    The results of a Solar Maximum Mission (SMM) guest investigation to determine the vertical gradients of sunspot magnetic fields for the first time from coordinated observations of photospheric and transition-region fields are described. Descriptions are given of both the photospheric vector field of a sunspot, derived from observations using the NASA Marshall Space Flight Center vector magnetograph, and of the line-of-sight component in the transition region, obtained from the SMM Ultraviolet Spectrometer and Polarimeter instrument. On the basis of these data, vertical gradients of the line-of-sight magnetic field component are calculated using three methods. It is found that the vertical gradient of Bz is lower than values from previous studies and that the transition-region field occurs at a height of approximately 4000-6000 km above the photosphere.

  1. Conjugate gradient algorithms using multiple recursions

    Energy Technology Data Exchange (ETDEWEB)

    Barth, T.; Manteuffel, T.

    1996-12-31

    Much is already known about when a conjugate gradient method can be implemented with short recursions for the direction vectors. The work done in 1984 by Faber and Manteuffel gave necessary and sufficient conditions on the iteration matrix A, in order for a conjugate gradient method to be implemented with a single recursion of a certain form. However, this form does not take into account all possible recursions. This became evident when Jagels and Reichel used an algorithm of Gragg for unitary matrices to demonstrate that the class of matrices for which a practical conjugate gradient algorithm exists can be extended to include unitary and shifted unitary matrices. The implementation uses short double recursions for the direction vectors. This motivates the study of multiple recursion algorithms.

  2. METALLICITY GRADIENTS OF THICK DISK DWARF STARS

    Energy Technology Data Exchange (ETDEWEB)

    Carrell, Kenneth; Chen Yuqin; Zhao Gang, E-mail: carrell@nao.cas.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2012-12-01

    We examine the metallicity distribution of the Galactic thick disk using F, G, and K dwarf stars selected from the Sloan Digital Sky Survey, Data Release 8. Using the large sample of dwarf stars with proper motions and spectroscopically determined stellar parameters, metallicity gradients in the radial direction for various heights above the Galactic plane and in the vertical direction for various radial distances from the Galaxy center have been found. In particular, we find a vertical metallicity gradient of -0.113 {+-} 0.010 (-0.125 {+-} 0.008) dex kpc{sup -1} using an isochrone (photometric) distance determination in the range 1 kpc <|Z| < 3 kpc, which is the vertical height range most consistent with the thick disk of our Galaxy. In the radial direction, we find metallicity gradients between +0.02 and +0.03 dex kpc{sup -1} for bins in the vertical direction between 1 kpc <|Z| < 3 kpc. Both of these results agree with similar values determined from other populations of stars, but this is the first time a radial metallicity gradient for the thick disk has been found at these vertical heights. We are also able to separate thin and thick disk stars based on kinematic and spatial probabilities in the vertical height range where there is significant overlap of these two populations. This should aid further studies of the metallicity gradients of the disk for vertical heights lower than those studied here but above the solar neighborhood. Metallicity gradients in the thin and thick disks are important probes into possible formation scenarios for our Galaxy and a consistent picture is beginning to emerge from results using large spectroscopic surveys, such as the ones presented here.

  3. Review of new shapes for higher gradients

    International Nuclear Information System (INIS)

    Geng, R.L.

    2006-01-01

    High-gradient superconducting RF (SRF) cavities are needed for energy frontier superconducting accelerators. Progress has been made over the past decades and the accelerating gradient E acc has been increased from a few MV/m to ∼42 MV/m in SRF niobium cavities. The corresponding peak RF magnetic field H pk on the niobium cavity surface is approaching the intrinsic RF critical magnetic field H crit,RF , a hard physical limit at which superconductivity breaks down. Pushing the gradient envelope further by adopting new cavity shapes with a lower ratio of H pk /E acc has been recently proposed. For a reduced H pk /E acc , a higher ultimate E acc is sustained when H pk finally strikes H crit,RF . The new cavity geometry include the re-entrant shape conceived at Cornell University and the so-called 'Low-loss' shape proposed by a DESY/JLAB/KEK collaboration. Experimental work is being pursued at Cornell, KEK and JLAB. Results of single-cell cavities are encouraging. A record gradient of 47 MV/m was first demonstrated in a 1.3 GHz re-entrant niobium cavity at Cornell University. At the time of writing, a new record of 52 MV/m has been realized with another 1.3 GHz re-entrant cavity, designed and built at Cornell and processed and tested at KEK. Single-cell low-loss cavities have reached equally high gradients in the range of 45-51 MV/m at KEK and JLAB. Owing to their higher gradient potential and the encouraging single-cell cavity results, the new cavity shapes are becoming attractive for their possible use in the international linear collider (ILC). Experimental work on multi-cell niobium cavities of new shapes is currently under active exploration

  4. Review of new shapes for higher gradients

    Science.gov (United States)

    Geng, R. L.

    2006-07-01

    High-gradient superconducting RF (SRF) cavities are needed for energy frontier superconducting accelerators. Progress has been made over the past decades and the accelerating gradient Eacc has been increased from a few MV/m to ∼42 MV/m in SRF niobium cavities. The corresponding peak RF magnetic field Hpk on the niobium cavity surface is approaching the intrinsic RF critical magnetic field Hcrit,RF, a hard physical limit at which superconductivity breaks down. Pushing the gradient envelope further by adopting new cavity shapes with a lower ratio of Hpk/ Eacc has been recently proposed. For a reduced Hpk/ Eacc, a higher ultimate Eacc is sustained when Hpk finally strikes Hcrit,RF. The new cavity geometry include the re-entrant shape conceived at Cornell University and the so-called “Low-loss” shape proposed by a DESY/JLAB/KEK collaboration. Experimental work is being pursued at Cornell, KEK and JLAB. Results of single-cell cavities are encouraging. A record gradient of 47 MV/m was first demonstrated in a 1.3 GHz re-entrant niobium cavity at Cornell University. At the time of writing, a new record of 52 MV/m has been realized with another 1.3 GHz re-entrant cavity, designed and built at Cornell and processed and tested at KEK. Single-cell low-loss cavities have reached equally high gradients in the range of 45-51 MV/m at KEK and JLAB. Owing to their higher gradient potential and the encouraging single-cell cavity results, the new cavity shapes are becoming attractive for their possible use in the international linear collider (ILC). Experimental work on multi-cell niobium cavities of new shapes is currently under active exploration.

  5. Frequency Analysis of Gradient Estimators in Volume Rendering

    NARCIS (Netherlands)

    Bentum, Marinus Jan; Lichtenbelt, Barthold B.A.; Malzbender, Tom

    1996-01-01

    Gradient information is used in volume rendering to classify and color samples along a ray. In this paper, we present an analysis of the theoretically ideal gradient estimator and compare it to some commonly used gradient estimators. A new method is presented to calculate the gradient at arbitrary

  6. Lactate uptake against a concentration gradient

    DEFF Research Database (Denmark)

    Nordström, Carl-Henrik; Nielsen, Troels Halfeld; Nielsen, Hans Boye

    2014-01-01

    The recently published article by Jalloh et al (Jalloh I, Helmy A, Shannon RJ, Gallagher CN, Menon D, Carpenter K, Hutchinson P. Lactate uptake by the injured human brain - evidence from an arterio-venous gradient and cerebral microdialysis study. J Neurotrauma. 2013 Aug 22. [Epub ahead of print......]) concludes that lactate may be transported across the blood brain barrier into the brain against a concentration gradient. Unfortunately the authors have misinterpreted the concept of analytical imprecision and their conclusion is based on analytical artifact. As the topic of lactate transport into the brain...

  7. Measurement of gradient magnetic field temporal characteristics

    International Nuclear Information System (INIS)

    Bartusek, K.; Jflek, B.

    1994-01-01

    We describe a technique of measuring the time dependence and field distortions of magnetic fields due to eddy currents (EC) produced by time-dependent magnetic field gradients. The EC measuring technique makes use of a large volume sample and selective RF excitation pulses and free induction decay (FID) (or a spin or gradient echo) to measure the out-of-phase component of the FID, which is proportional to γδB, i.e. the amount the signal is off resonance. The measuring technique is sensitive, easy to implement and interpret, and used for determining pre-emphasis compensation parameters

  8. Magnetic field of longitudinal gradient bend

    Science.gov (United States)

    Aiba, Masamitsu; Böge, Michael; Ehrlichman, Michael; Streun, Andreas

    2018-06-01

    The longitudinal gradient bend is an effective method for reducing the natural emittance in light sources. It is, however, not a common element. We have analyzed its magnetic field and derived a set of formulae. Based on the derivation, we discuss how to model the longitudinal gradient bend in accelerator codes that are used for designing electron storage rings. Strengths of multipole components can also be evaluated from the formulae, and we investigate the impact of higher order multipole components in a very low emittance lattice.

  9. CFRMF neutron flux gradient and spectral determinations

    International Nuclear Information System (INIS)

    Rogers, J.W.; Turk, E.H.; Hogg, C.H.

    1976-01-01

    Recently more accurate and complete measurements of the flux gradient have been measured by the activation of 235 U and Au samples. Neutron spectrum characteristics were studied by making activation measurements with and without the ends of the CFRMF test region plugged with 10 B. These measurements define the flux gradient to +-1 to 2% and indicate there is no detectable streaming of thermal or resonance neutrons from the ends in the central 30 cm of the CFRMF test region. Measurements of the Cd ratio of Au foil activations were conducted and these results also indicate there is no streaming of thermal and resonance neutrons into the CFRMF test region

  10. The effect of density gradients on hydrometers

    Science.gov (United States)

    Heinonen, Martti; Sillanpää, Sampo

    2003-05-01

    Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we studied the effect of non-uniform density of liquid on a hydrometer reading. The effect induced by vertical temperature gradients was investigated theoretically and experimentally. A method for compensating for the effect mathematically was developed and tested with experimental data obtained with the MIKES hydrometer calibration system. In the tests, the method was found reliable. However, the reliability depends on the available information on the hydrometer dimensions and density gradients.

  11. Relativistic klystron research for high gradient accelerators

    International Nuclear Information System (INIS)

    Allen, M.A.; Callin, R.S.; Deruyter, H.

    1988-06-01

    Relativistic klystrons are being developed as a power source for high gradient accelerator applications which include large linear electron--positron colliders, compact accelerators, and FEL sources. We have attained 200MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here on the design of our first klystrons, the results of our experiments so far, and some of our plans for the near future. 5 refs., 7 figs

  12. Gradient Learning Algorithms for Ontology Computing

    Science.gov (United States)

    Gao, Wei; Zhu, Linli

    2014-01-01

    The gradient learning model has been raising great attention in view of its promising perspectives for applications in statistics, data dimensionality reducing, and other specific fields. In this paper, we raise a new gradient learning model for ontology similarity measuring and ontology mapping in multidividing setting. The sample error in this setting is given by virtue of the hypothesis space and the trick of ontology dividing operator. Finally, two experiments presented on plant and humanoid robotics field verify the efficiency of the new computation model for ontology similarity measure and ontology mapping applications in multidividing setting. PMID:25530752

  13. Gradient Learning Algorithms for Ontology Computing

    Directory of Open Access Journals (Sweden)

    Wei Gao

    2014-01-01

    Full Text Available The gradient learning model has been raising great attention in view of its promising perspectives for applications in statistics, data dimensionality reducing, and other specific fields. In this paper, we raise a new gradient learning model for ontology similarity measuring and ontology mapping in multidividing setting. The sample error in this setting is given by virtue of the hypothesis space and the trick of ontology dividing operator. Finally, two experiments presented on plant and humanoid robotics field verify the efficiency of the new computation model for ontology similarity measure and ontology mapping applications in multidividing setting.

  14. Transplantation of subalpine wood-pasture turfs along a natural climatic gradient reveals lower resistance of unwooded pastures to climate change compared to wooded ones.

    Science.gov (United States)

    Gavazov, Konstantin; Spiegelberger, Thomas; Buttler, Alexandre

    2014-04-01

    Climate change could impact strongly on cold-adapted mountain ecosystems, but little is known about its interaction with traditional land-use practices. We used an altitudinal gradient to simulate a year-round warmer and drier climate for semi-natural subalpine grasslands across a landscape of contrasting land-use management. Turf mesocosms from three pasture-woodland land-use types-unwooded pasture, sparsely wooded pasture, and densely wooded pasture-spanning a gradient from high to low management intensity were transplanted downslope to test their resistance to two intensities of climate change. We found strong overall effects of intensive (+4 K) experimental climate change (i.e., warming and reduced precipitation) on plant community structure and function, while moderate (+2 K) climate change did not substantially affect the studied land-use types, thus indicating an ecosystem response threshold to moderate climate perturbation. The individual land-use types were affected differently under the +4 K scenario, with a 60% decrease in aboveground biomass (AGB) in unwooded pasture turfs, a 40% decrease in sparsely wooded pasture turfs, and none in densely wooded ones. Similarly, unwooded pasture turfs experienced a 30% loss of species, advanced (by 30 days) phenological development, and a mid-season senescence due to drought stress, while no such effects were recorded for the other land-use types. The observed contrasting effects of climate change across the pasture-woodland landscape have important implications for future decades. The reduced impact of climate change on wooded pastures as compared to unwooded ones should promote the sustainable land use of wooded pastures by maintaining low management intensity and a sparse forest canopy, which buffer the immediate impacts of climate change on herbaceous vegetation.

  15. Zonación de peligros por procesos gravitacionales en el flanco suroccidental del volcán Pico de Orizaba, México.

    Directory of Open Access Journals (Sweden)

    Gabriel Legorreta Paulín

    2013-09-01

    Full Text Available Resumen. La cuenca del río Chiquito-Barranca del Muerto, de 111 km2 de superficie, ubicada en el flanco suroccidental del volcán Pico de Orizaba (5675 msnm, se estudió utilizando fotografías aéreas de diversos años y trabajo de campo, con una adaptación del Protocolo de zonificación del peligro de remoción en masa del Departamento de Recursos Naturales, del Estado de Washington, EUA. Se reconocieron 571 procesos gravitacionales de seis tipos: superficial, de escombros-avalancha y profundo, flujos de escombros y de tierra, y caída de rocas. Se definieron doce formas principales del relieve en las que ocurren procesos gravitacionales: barrancos, cabeceras, escarpes de cabeceras de deslizamiento profundo, meandros, planicies, además de tres tipos de laderas clasificadas por su gradiente (véase Tabla 2: bajo, moderado y alto, caída de rocas, barrancas no reguladas, cabeceras no reguladas y laderas convergentes no reguladas. Los procesos gravitacionales potenciales se clasifican en tres rangos de peligro: bajo, alto y muy alto. Los procesos gravitacionales se presentan principalmente en laderas con gradiente moderado, en barrancas no reguladas, en barrancas y en laderas con gradiente bajo. Mientras que el rango de estabilidad es bajo en planicies y en laderas de gradiente menor, es alto en las laderas de gradiente moderado y mayor, en las ocho restantes es muy alto.

  16. Up-gradient transport in a probabilistic transport model

    DEFF Research Database (Denmark)

    Gavnholt, J.; Juul Rasmussen, J.; Garcia, O.E.

    2005-01-01

    The transport of particles or heat against the driving gradient is studied by employing a probabilistic transport model with a characteristic particle step length that depends on the local concentration or heat gradient. When this gradient is larger than a prescribed critical value, the standard....... These results supplement recent works by van Milligen [Phys. Plasmas 11, 3787 (2004)], which applied Levy distributed step sizes in the case of supercritical gradients to obtain the up-gradient transport. (c) 2005 American Institute of Physics....

  17. Magnetoelectric Transverse Gradient Sensor with High Detection Sensitivity and Low Gradient Noise.

    Science.gov (United States)

    Zhang, Mingji; Or, Siu Wing

    2017-10-25

    We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME voltage between the two ME composites and is calibrated against transverse MFGs to give a high detection sensitivity of 0.4-30.6 V/(T/m), a strong common-mode magnetic field noise rejection rate of gradient noise of 0.16-620 nT/m/ Hz in a broad frequency range of 1 Hz-170 kHz under a small baseline of 35 mm. An analysis of experimental gradient noise spectra obtained in a magnetically-unshielded laboratory environment reveals the domination of the pink (1/ f ) noise, dielectric loss noise, and power-frequency noise below 3 kHz, in addition to the circuit noise above 3 kHz, in the gradient sensor. The high detection performance, together with the added merit of passive and direct ME conversion by the large ME effect in the ME composites, makes the gradient sensor suitable for the passive, direct, and broadband detection of transverse MFGs.

  18. Large Airborne Full Tensor Gradient Data Inversion Based on a Non-Monotone Gradient Method

    Science.gov (United States)

    Sun, Yong; Meng, Zhaohai; Li, Fengting

    2018-03-01

    Following the development of gravity gradiometer instrument technology, the full tensor gravity (FTG) data can be acquired on airborne and marine platforms. Large-scale geophysical data can be obtained using these methods, making such data sets a number of the "big data" category. Therefore, a fast and effective inversion method is developed to solve the large-scale FTG data inversion problem. Many algorithms are available to accelerate the FTG data inversion, such as conjugate gradient method. However, the conventional conjugate gradient method takes a long time to complete data processing. Thus, a fast and effective iterative algorithm is necessary to improve the utilization of FTG data. Generally, inversion processing is formulated by incorporating regularizing constraints, followed by the introduction of a non-monotone gradient-descent method to accelerate the convergence rate of FTG data inversion. Compared with the conventional gradient method, the steepest descent gradient algorithm, and the conjugate gradient algorithm, there are clear advantages of the non-monotone iterative gradient-descent algorithm. Simulated and field FTG data were applied to show the application value of this new fast inversion method.

  19. Energy Transfer Using Gradient Index Metamaterial

    Directory of Open Access Journals (Sweden)

    Boopalan Ganapathy

    2018-01-01

    Full Text Available The gradient refractive index structure in this paper is used to increase the quantum of energy transfer. This is done by improving the directive gain of the pyramidal horn antenna at a frequency of 10 GHz. A three-dimensional array of closed square rings is placed in front of the horn antenna aperture to form a gradient refractive index structure. This structure increases the directive gain by 1.6 dB as compared to that of the conventional horn antenna. The structure nearly doubles the wireless power transfer quantum between the transmitter and the receiver when placed at both ends. The increase in the directivity is achieved by converting the spherical wave emanating from the horn to a plane wave once it passes through the structure. This transformation is realized by the gradient refractive index structure being placed perpendicular to the direction of propagation. The gradient refractive index is constructed by changing the dimensions of a closed square ring placed in the unit cell of the array. The change in the refractive index gives rise to an improvement of the half power beam width and side lobe level compared to that of the normal horn. The design and simulation were done using CST Studio software.

  20. Crack Tip Mechanics in Distortion Gradient Plasticity

    DEFF Research Database (Denmark)

    Fuentes-Alonso, Sandra; Martínez Pañeda, Emilio

    2017-01-01

    Gradient Plasticity (DGP), the influence on crack tip mechanics of DGP's distinguishing features that entail superior modelling capabilities has not been investigated yet. In this work crack tip fields are thoroughly examined by implementing the higher order theory of DGP in an implicit finite element...

  1. Discrete gradients in discrete classical mechanics

    International Nuclear Information System (INIS)

    Renna, L.

    1987-01-01

    A simple model of discrete classical mechanics is given where, starting from the continuous Hamilton equations, discrete equations of motion are established together with a proper discrete gradient definition. The conservation laws of the total discrete momentum, angular momentum, and energy are demonstrated

  2. Gradient based filtering of digital elevation models

    DEFF Research Database (Denmark)

    Knudsen, Thomas; Andersen, Rune Carbuhn

    We present a filtering method for digital terrain models (DTMs). The method is based on mathematical morphological filtering within gradient (slope) defined domains. The intention with the filtering procedure is to improbé the cartographic quality of height contours generated from a DTM based...

  3. Gradient Space under Orthography and Perspective

    Science.gov (United States)

    1982-05-24

    surfaceorientation to image geometry [8, 9, 10, 13, 15]. The descriptions of important gradient space properties, however, have been scattered throughout...Kanade, T. A Theory of Origami World. Artificial Intelligence 13:279-311, 1980. *[8] Kanade, T. and Kender, J. Mapping Image Properies into Shape

  4. Joining of Tungsten Armor Using Functional Gradients

    International Nuclear Information System (INIS)

    John Scott O'Dell

    2006-01-01

    The joining of low thermal expansion armor materials such as tungsten to high thermal expansion heat sink materials has been a major problem in plasma facing component (PFC) development. Conventional planar bonding techniques have been unable to withstand the high thermal induced stresses resulting from fabrication and high heat flux testing. During this investigation, innovative functional gradient joints produced using vacuum plasma spray forming techniques have been developed for joining tungsten armor to copper alloy heat sinks. A model was developed to select the optimum gradient architecture. Based on the modeling effort, a 2mm copper rich gradient was selected. Vacuum plasma pray parameters and procedures were then developed to produce the functional gradient joint. Using these techniques, dual cooling channel, medium scale mockups (32mm wide x 400mm length) were produced with vacuum plasma spray formed tungsten armor. The thickness of the tungsten armor was up to 5mm thick. No evidence of debonding at the interface between the heat sink and the vacuum plasma sprayed material was observed.

  5. Mass balance gradients and climatic change

    NARCIS (Netherlands)

    Oerlemans, J.; Hoogendoorn, N.C.

    1989-01-01

    It is generally assumed that the mass-balance gradient on glaciers is more or less conserved under climatic change. In studies of the dynamic response of glaciers to climatic change, one of the following assumptions is normally made: (i) the mass-balance perturbation is independent of altitude

  6. Considerations of ion temperature gradient driven turbulence

    International Nuclear Information System (INIS)

    Cowley, S.C.; Kulsrud, R.M.

    1991-02-01

    The ion temperature gradient driven instability is considered in this paper. Physical pictures are presented to clarify the nature of the instability. The saturation of a single eddy is modeled by a simple nonlinear equation. We show that eddies which are elongated in the direction of the temperature gradient are the most unstable and have the highest saturation amplitudes. In a sheared magnetic field, such elongated eddies twist with the field lines. This structure is shown to be alternative to the usual Fourier mode picture in which the mode is localized around the surface where k parallel = 0. We show how these elongated twisting eddies, which are an integral part of the ''ballooning mode'' structure, could survive in a torus. The elongated eddies are shown to be unstable to secondary instabilities that are driven by the large gradients in the long eddy. We argue that this mechanism isotropizes ion temperature gradient turbulence. We further argue that the ''mixing length'' is set by this nonlinear process, not by a linear eigenmode width. 17 refs., 6 figs

  7. Analysis of magnetic gradients to study gravitropism.

    Science.gov (United States)

    Hasenstein, Karl H; John, Susan; Scherp, Peter; Povinelli, Daniel; Mopper, Susan

    2013-01-01

    Gravitropism typically is generated by dense particles that respond to gravity. Experimental stimulation by high-gradient magnetic fields provides a new approach to selectively manipulate the gravisensing system. The movement of corn, wheat, and potato starch grains in suspension was examined with videomicroscopy during parabolic flights that generated 20 to 25 s of weightlessness. During weightlessness, a magnetic gradient was generated by inserting a wedge into a uniform, external magnetic field that caused repulsion of starch grains. The resultant velocity of movement was compared with the velocity of sedimentation under 1 g conditions. The high-gradient magnetic fields repelled the starch grains and generated a force of at least 0.6 g. Different wedge shapes significantly affected starch velocity and directionality of movement. Magnetic gradients are able to move diamagnetic compounds under weightless or microgravity conditions and serve as directional stimulus during seed germination in low-gravity environments. Further work can determine whether gravity sensing is based on force or contact between amyloplasts and statocyte membrane system.

  8. Gradient computation for VTI acoustic wavefield tomography

    KAUST Repository

    Li, Vladimir

    2016-09-06

    Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a pseudospectral operator that employes a separable approximation of the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified stack-power objective functions. We also obtain the gradient expressions for the data-domain objective function, which can incorporate borehole information necessary for stable VTI velocity analysis. These gradients are compared to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations. Whereas the kernels computed with the two wave-equation operators are similar, the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show that the modified stack-power objective function produces cleaner gradients than the more conventional DSO operator.

  9. Conjugate Gradient Algorithms For Manipulator Simulation

    Science.gov (United States)

    Fijany, Amir; Scheid, Robert E.

    1991-01-01

    Report discusses applicability of conjugate-gradient algorithms to computation of forward dynamics of robotic manipulators. Rapid computation of forward dynamics essential to teleoperation and other advanced robotic applications. Part of continuing effort to find algorithms meeting requirements for increased computational efficiency and speed. Method used for iterative solution of systems of linear equations.

  10. Examining the Education Gradient in Chronic Illness

    Science.gov (United States)

    Chatterji, Pinka; Joo, Heesoo; Lahiri, Kajal

    2015-01-01

    We examine the education gradient in diabetes, hypertension, and high cholesterol. We take into account diagnosed as well as undiagnosed cases and use methods accounting for the possibility of unmeasured factors that are correlated with education and drive both the likelihood of having illness and the propensity to be diagnosed. Data come from the…

  11. Subspace learning from image gradient orientations

    NARCIS (Netherlands)

    Tzimiropoulos, Georgios; Zafeiriou, Stefanos; Pantic, Maja

    2012-01-01

    We introduce the notion of subspace learning from image gradient orientations for appearance-based object recognition. As image data is typically noisy and noise is substantially different from Gaussian, traditional subspace learning from pixel intensities fails very often to estimate reliably the

  12. Acerca del moho

    Science.gov (United States)

    El moho forma parte del medio ambiente natural. Afuera del hogar, el moho juega un papel en la naturaleza al desintegrar materias organicas tales como las hojas que se han caido o los arboles muertos. El moho puede crecer adentro del hogar cuando las espor

  13. Del bit al qubit

    OpenAIRE

    Torras Font, Josep

    2011-01-01

    Aquest document pretén donar una visió del desenvolupament dels computadors electrònics i dels components que els han fet possibles. Dintre de les opcions de futur en computació, també intenta donar una visió de les bases en que es fonamenta la computació quàntica.

  14. Amortización de Intangibles con cargos variables y gradiente aritmético predeterminado

    OpenAIRE

    Zans Arimana, Walter

    2014-01-01

    En este trabajo el objetivo general de la investigación ha sido construir un método que permita amortizar un activo intangible con un procedimiento nuevo, basado en cargos anuales que varían con un gradiente aritmético previamente establecido por la gerencia. La metodología ha sido numérica, aplicando las propiedades de las progresiones aritméticas. Los resultados han llevado a la construcción del mencionado método, concluyendo dicho procedimiento cumple con la definición de amortización que ...

  15. Screening for mutations in the uroporphyrinogen decarboxylase gene using denaturing gradient gel electrophoresis

    DEFF Research Database (Denmark)

    Christiansen, L; Ged, C; Hombrados, I

    1999-01-01

    to exon skipping, and a 2-bp deletion (415-416delTA) resulting in a frameshift and the introduction of a premature stop codon. Heterologous expression and enzymatic studies of the mutant proteins demonstrate that the three mutations leading to shortening or truncation of the UROD protein have no residual......, confirming the heterogeneity of the underlying genetic defects of these diseases. We have established a denaturing gradient gel electrophoresis (DGGE) assay for mutation detection in the UROD gene, enabling the simultaneous screening for known and unknown mutations. The established assay has proved able...

  16. Processes affecting altitudinal distribution of invasive Ageratina adenophora in western Himalaya: The role of local adaptation and the importance of different life-cycle stages.

    Science.gov (United States)

    Datta, Arunava; Kühn, Ingolf; Ahmad, Mustaqeem; Michalski, Stefan; Auge, Harald

    2017-01-01

    The spread of invasive plants along elevational gradients is considered a threat to fragile mountain ecosystems, but it can also provide the opportunity to better understand some of the basic processes driving the success of invasive species. Ageratina adenophora (Asteraceae) is an invasive plant of global importance and has a broad distribution along elevational gradients in the Western Himalayas. Our study aimed at understanding the role of evolutionary processes (e.g. local adaptation and clinal differentiation) and different life history stages in shaping the distribution pattern of the invasive plant along an elevational gradient in the Western Himalaya. We carried out extensive distributional surveys, established a reciprocal transplant experiment with common gardens at three elevational levels, and measured a suite of traits related to germination, growth, reproduction and phenology. Our results showed a lack of local adaptation, and we did not find any evidence for clinal differentiation in any measured trait except a rather weak signal for plant height. We found that seed germination was the crucial life-cycle transition in determining the lower range limit while winter mortality of plants shaped the upper range limit in our study area, thus explaining the hump shaped distribution pattern. Differences in trait values between gardens for most traits indicated a high degree of phenotypic plasticity. Possible causes such as apomixis, seed dispersal among sites, and pre-adaptation might have confounded evolutionary processes to act upon. Our results suggest that the success and spread of Ageratina adenophora are dependent on different life history stages at different elevations that are controlled by abiotic conditions.

  17. Anfibios andinos del Perú fuera de Áreas Naturales Protegidas: amenazas y estado de conservación

    Directory of Open Access Journals (Sweden)

    César Aguilar

    2011-05-01

    Full Text Available Presentamos una lista actualizada de los anfibios presentes en Perú y para las especies andinas (con distribución altitudinal sobre los 1000 m de altitud se informa sobre su categoría según la UICN, los endémicos de Perú, sus amenazas y su presencia dentro del SINANPE. Hasta el año 2010 se conocen 538 especies de anfibios; 110 especies fueron registradas entre el año 2003 y el 2010; aproximadamente una especie descrita por mes. De las 110 especies descritas desde el 2003, 77 fueron andinas y 64% de éstas se encuentran fuera del SINANPE. En total son reconocidas 235 especies andinas, el 80% son endémicas de Perú y 58% de éstas se encuentran fuera del SINANPE. Noventaiun especies andinas están en categorías de amenaza y en la categoría de Casi Amenazado, y 53% de éstas se encuentran fuera del SINANPE. Los géneros Telmatobius y Atelopus, así como las familias Centrolenidae y Strabomantidae, presentan los porcentajes más altos de especies andinas con categorías de amenaza y Casi Amenazado. Para 83 (36% especies de anfibios andinos presentes en Perú, la principal amenaza es la pérdida del hábitat. Otras amenazas que se presentan en menores porcentajes son la quitridiomicosis, degradación del hábitat y sobrexplotación. Se recomienda el fomento de áreas de conservación privadas para las especies de anfibios andinos presentes en Perú con categorías de amenaza, endémicas y que no están dentro del SINANPE.

  18. Paleoecología y gestión del combustible en la ocupación del Auriñaciense arcaico de la cueva de El Castillo (Puente Viesgo, Cantabria

    Directory of Open Access Journals (Sweden)

    Victoria Cabrera Valdés

    1999-01-01

    Full Text Available El análisis antracológico correspondiente al nivel 18 (Auriñaciense arcaico de la cueva del Castillo (Cantabria, Norte de España, ha puesto en evidencia una flora compuesta por Betu\\a, P'mus t. sylvestris y Sorbus aria. Las dataciones "C en espectrometría de masa por acelerador obtenidas sobre carbón, sitúan este nivel en el Pleniglaciar medio (37-40Ka.. Las estimaciones paleoambientales obtenidas a través de los estudios de los glaciares de las montañas cantábricas y del Pirineo occidental, nos han permitido correlacionar la Antracología y el Glaciarismo. El paisaje vegetal alrededor del habitat prehistórico estaría compuesto esencialmente por especies pioneras que tian coionizado unos sueios Ubres de hieios pero sometidos a condiciones periglaciares debido a que este iiabitat estaba próximo de ia cota aititudinal aicanzada por ios giaciares de montaña. Estos serian responsabies en parte dei desfase aititudinai y zonai de ia vegetación si io comparamos con ias condiciones actuaies. Los trayectos diarios recorridos por ios grupos liumanos a ia búsqueda de recursos económicos diversos, entre ellos la leña para encender fuego, se verían infiuídos en gran parte por estos condicionantes ambientaies.Charcoal analysis from archaeological levéis oí El Castillo (Cantabria, Northern Spain, have yielded Betula; Pinus t. sylvestris and Sorbus aria. The AMS C obtained on the same samples place these levéis on the Middie Pleniglacial (37-40Ka.. Palaeoenvironmental results obtained in glacial deposits from Cantabrian mountains and western Pyrenees let us to compare charcoal analysis and glaciation patterns. Landscape around this prehistoric settiement is formed essentially by pioneer vegetation cover along free-glace areas but under periglacial conditions. Altitudinal position of this site and ttie glaciai zones are similar. This particuiarity explain the altitudinal gap of the vegetation in tiiis área. Diary routes tallen by humans

  19. Effects of Gradient Coil Noise and Gradient Coil Replacement on the Reproducibility of Resting State Networks.

    Science.gov (United States)

    Bagarinao, Epifanio; Tsuzuki, Erina; Yoshida, Yukina; Ozawa, Yohei; Kuzuya, Maki; Otani, Takashi; Koyama, Shuji; Isoda, Haruo; Watanabe, Hirohisa; Maesawa, Satoshi; Naganawa, Shinji; Sobue, Gen

    2018-01-01

    The stability of the MRI scanner throughout a given study is critical in minimizing hardware-induced variability in the acquired imaging data set. However, MRI scanners do malfunction at times, which could generate image artifacts and would require the replacement of a major component such as its gradient coil. In this article, we examined the effect of low intensity, randomly occurring hardware-related noise due to a faulty gradient coil on brain morphometric measures derived from T1-weighted images and resting state networks (RSNs) constructed from resting state functional MRI. We also introduced a method to detect and minimize the effect of the noise associated with a faulty gradient coil. Finally, we assessed the reproducibility of these morphometric measures and RSNs before and after gradient coil replacement. Our results showed that gradient coil noise, even at relatively low intensities, could introduce a large number of voxels exhibiting spurious significant connectivity changes in several RSNs. However, censoring the affected volumes during the analysis could minimize, if not completely eliminate, these spurious connectivity changes and could lead to reproducible RSNs even after gradient coil replacement.

  20. Gradient waveform pre-emphasis based on the gradient system transfer function.

    Science.gov (United States)

    Stich, Manuel; Wech, Tobias; Slawig, Anne; Ringler, Ralf; Dewdney, Andrew; Greiser, Andreas; Ruyters, Gudrun; Bley, Thorsten A; Köstler, Herbert

    2018-02-25

    The gradient system transfer function (GSTF) has been used to describe the distorted k-space trajectory for image reconstruction. The purpose of this work was to use the GSTF to determine the pre-emphasis for an undistorted gradient output and intended k-space trajectory. The GSTF of the MR system was determined using only standard MR hardware without special equipment such as field probes or a field camera. The GSTF was used for trajectory prediction in image reconstruction and for a gradient waveform pre-emphasis. As test sequences, a gradient-echo sequence with phase-encoding gradient modulation and a gradient-echo sequence with a spiral read-out trajectory were implemented and subsequently applied on a structural phantom and in vivo head measurements. Image artifacts were successfully suppressed by applying the GSTF-based pre-emphasis. Equivalent results are achieved with images acquired using GSTF-based post-correction of the trajectory as a part of image reconstruction. In contrast, the pre-emphasis approach allows reconstruction using the initially intended trajectory. The artifact suppression shown for two sequences demonstrates that the GSTF can serve for a novel pre-emphasis. A pre-emphasis based on the GSTF information can be applied to any arbitrary sequence type. © 2018 International Society for Magnetic Resonance in Medicine.

  1. Degraded character recognition based on gradient pattern

    Science.gov (United States)

    Babu, D. R. Ramesh; Ravishankar, M.; Kumar, Manish; Wadera, Kevin; Raj, Aakash

    2010-02-01

    Degraded character recognition is a challenging problem in the field of Optical Character Recognition (OCR). The performance of an optical character recognition depends upon printed quality of the input documents. Many OCRs have been designed which correctly identifies the fine printed documents. But, very few reported work has been found on the recognition of the degraded documents. The efficiency of the OCRs system decreases if the input image is degraded. In this paper, a novel approach based on gradient pattern for recognizing degraded printed character is proposed. The approach makes use of gradient pattern of an individual character for recognition. Experiments were conducted on character image that is either digitally written or a degraded character extracted from historical documents and the results are found to be satisfactory.

  2. Voltammetry under a Controlled Temperature Gradient

    Directory of Open Access Journals (Sweden)

    Jan Krejci, Jr.

    2010-07-01

    Full Text Available Electrochemical measurements are generally done under isothermal conditions. Here we report on the application of a controlled temperature gradient between the working electrode surface and the solution. Using electrochemical sensors prepared on ceramic materials with extremely high specific heat conductivity, the temperature gradient between the electrode and solution was applied here as a second driving force. This application of the Soret phenomenon increases the mass transfer in the Nernst layer and enables more accurate control of the electrode response enhancement by a combination of diffusion and thermal diffusion. We have thus studied the effect of Soret phenomenon by cyclic voltammetry measurements in ferro/ferricyanide. The time dependence of sensor response disappears when applying the Soret phenomenon, and the complicated shape of the cyclic voltammogram is replaced by a simple exponential curve. We have derived the Cotrell-Soret equation describing the steady-state response with an applied temperature difference.

  3. Anisotropic gradients in the upper mantle

    International Nuclear Information System (INIS)

    Garmany, J.

    1981-01-01

    Pn amplitudes in some widely spaced sets of orthogonal marine refraction lines on young oceanic crust are greater in the fast direction than in the slow direction. This is inconsistent with the predicted amplitude behavior for simple head waves, but can be explained by an increase in anisotropy with depth. It appears that these gradients are due to increasing olivine crystal orientation, although changes in the relative abundance of two anisotropic minerals without variable tectonization could also account for the observations. Depth variation of tectonization most probably indicates very high temperature gradients at the Moho. This would imply a substantial amount of convective heat transport in the whole oceanic crust near mid-ocean rises

  4. Model predictive control for wind power gradients

    DEFF Research Database (Denmark)

    Hovgaard, Tobias Gybel; Boyd, Stephen; Jørgensen, John Bagterp

    2015-01-01

    We consider the operation of a wind turbine and a connected local battery or other electrical storage device, taking into account varying wind speed, with the goal of maximizing the total energy generated while respecting limits on the time derivative (gradient) of power delivered to the grid. We...... ranges. The system dynamics are quite non-linear, and the constraints and objectives are not convex functions of the control inputs, so the resulting optimal control problem is difficult to solve globally. In this paper, we show that by a novel change of variables, which focuses on power flows, we can...... wind data and modern wind forecasting methods. The simulation results using real wind data demonstrate the ability to reject the disturbances from fast changes in wind speed, ensuring certain power gradients, with an insignificant loss in energy production....

  5. Entanglement-Gradient Routing for Quantum Networks.

    Science.gov (United States)

    Gyongyosi, Laszlo; Imre, Sandor

    2017-10-27

    We define the entanglement-gradient routing scheme for quantum repeater networks. The routing framework fuses the fundamentals of swarm intelligence and quantum Shannon theory. Swarm intelligence provides nature-inspired solutions for problem solving. Motivated by models of social insect behavior, the routing is performed using parallel threads to determine the shortest path via the entanglement gradient coefficient, which describes the feasibility of the entangled links and paths of the network. The routing metrics are derived from the characteristics of entanglement transmission and relevant measures of entanglement distribution in quantum networks. The method allows a moderate complexity decentralized routing in quantum repeater networks. The results can be applied in experimental quantum networking, future quantum Internet, and long-distance quantum communications.

  6. Social gradients in periodontal diseases among adolescents.

    Science.gov (United States)

    López, Rodrigo; Fernández, Olaya; Baelum, Vibeke

    2006-06-01

    To investigate the association between socioeconomic position and periodontal diseases among adolescents. Data were obtained from 9203 Chilean high school students. Clinical examinations included direct recordings of clinical attachment level and the necrotizing ulcerative gingival lesions. Students answered a questionnaire on various dimensions of socioeconomic position. Seven periodontal outcomes were analyzed. Logistic regression analyses were used to identify socioeconomic variables associated with the periodontal outcomes. The occurrence of all periodontal outcomes investigated followed social gradients, and paternal income and parental education were the most influential variables. The study demonstrates the existence of significant social gradients in periodontal diseases already among adolescents. This is worrying, and indicates a new potential for further insight into the mechanisms of periodontal disease causation.

  7. Opinion formation models on a gradient.

    Directory of Open Access Journals (Sweden)

    Michael T Gastner

    Full Text Available Statistical physicists have become interested in models of collective social behavior such as opinion formation, where individuals change their inherently preferred opinion if their friends disagree. Real preferences often depend on regional cultural differences, which we model here as a spatial gradient g in the initial opinion. The gradient does not only add reality to the model. It can also reveal that opinion clusters in two dimensions are typically in the standard (i.e., independent percolation universality class, thus settling a recent controversy about a non-consensus model. However, using analytical and numerical tools, we also present a model where the width of the transition between opinions scales proportional g(-1/4, not proportional g(-4/7 as in independent percolation, and the cluster size distribution is consistent with first-order percolation.

  8. Superconducting niobium cavities with high gradients

    International Nuclear Information System (INIS)

    Kneisel, P.; Saito, K.

    1992-01-01

    Present accelerator projects making use of superconducting cavity technology are constructed with design accelerating gradients E acc ranging between 5 MV/m and 8 MV/m and Q-values of several 10 9 . Future plans for upgrades of existing accelerators or for linear colliders call for gradients greater than 15 MV/m corresponding to peak surface electric fields above 30 MV/m. These demands challenge state-of-the-art production technology and require improvements in processing and handling of these cavities to overcome the major performance limitation of field emission loading. This paper reports on efforts to improve the performance of cavities made from niobium from different suppliers by using improved cleaning techniques after processing and ultrahigh vacuum annealing at temperatures of 1400 C. In single cell L-band cavities peak surface electric fields as high as 50 MV/m have been measured without significant field emission loading. (Author) 8 refs., fig

  9. Optimizing sampling approaches along ecological gradients

    DEFF Research Database (Denmark)

    Schweiger, Andreas; Irl, Severin D. H.; Steinbauer, Manuel

    2016-01-01

    1. Natural scientists and especially ecologists use manipulative experiments or field observations along gradients to differentiate patterns driven by processes from those caused by random noise. A well-conceived sampling design is essential for identifying, analysing and reporting underlying...... patterns in a statistically solid and reproducible manner, given the normal restrictions in labour, time and money. However, a technical guideline about an adequate sampling design to maximize prediction success under restricted resources is lacking. This study aims at developing such a solid...... and reproducible guideline for sampling along gradients in all fields of ecology and science in general. 2. We conducted simulations with artificial data for five common response types known in ecology, each represented by a simple function (no response, linear, exponential, symmetric unimodal and asymmetric...

  10. Spectrum of resistivity gradient driven turbulence

    International Nuclear Information System (INIS)

    Terry, P.W.; Diamond, P.H.; Shaing, K.C.; Garcia, L.; Carreras, B.A.

    1986-01-01

    The resistivity fluctuation correlation function and electrostatic potential spectrum of resistivity gradient driven turbulence are calculated analytically and compared to the results of three dimensional numerical calculations. Resistivity gradient driven turbulence is characterized by effective Reynolds' numbers of order unity. Steady-state solution of the renormalized spectrum equations yields an electrostatic potential spectrum (circumflex phi 2 )/sub ktheta/ approx. k/sub theta//sup -3.25/. Agreement of the analytically calculated potential spectrum and mean-square radial velocity with the results of multiple helicity numerical calculations is excellent. This comparison constitutes a quantitative test of the analytical turbulence theory used. The spectrum of magnetic fluctuations is also calculated, and agrees well with that obtained from the numerical computations. 13 refs., 8 figs

  11. Diseño de un sistema de recirculación y enfriamiento del agua para la destilación del mezcal

    OpenAIRE

    Caballero Caballero, Magdaleno; Silva Santos, Luis; Montes Bernabé, José Luis

    2012-01-01

    El presente trabajo muestra una propuesta para hacer mas eficiente la etapa de destilación dentro del proceso de producción artesanal de mezcal, enfocándose al enfriamiento del agua utilizada en esta etapa. Para identificar la problemática, fue necesario hacer un seguimiento del proceso, poniendo especial énfasis en la operación de condensación. El proceso actual tiene una ineficiencia de 73.25%, provocado por la falta de un gradiente de temperatura, al sobrecalentarse el agua de enfriamiento...

  12. Algunas aclaraciones acerca del conocimiento del singular.

    Directory of Open Access Journals (Sweden)

    Carlos Llano Cifuentes

    2013-11-01

    Full Text Available Llano tries to explain the main purpose of El Conocimiento del Singular, showing how the individuals about which the book is concerned are basically human individuals: people as decision makers.

  13. Transport due to ion pressure gradient turbulence

    International Nuclear Information System (INIS)

    Connor, J.W.

    1986-01-01

    Turbulent transport due to the ion pressure gradient (or temperature drift) instability is thought to be significant when etasub(i)=d(ln Tsub(i))/d(ln n)>1. The invariance properties of the governing equations under scale transformations are used to discuss the characteristics of this turbulence. This approach not only clarifies the relationships between earlier treatments but also, in certain limits, completely determines the scaling properties of the fluctuations and the consequent thermal transport. (author)

  14. Radial oxygen gradients over rat cortex arterioles

    OpenAIRE

    Galler, Michael

    2011-01-01

    Purpose: We present the results of the visualisation of radial oxygen gradients in rats’ cortices and their use in neurocritical management. Methods: PO2 maps of the cortex of 10 wistar rats were obtained with a camera (SensiMOD, PCO, Kehlheim, Germany). Those pictures were analyzed and edited by a custom-made software. We chose a vessel for examination. A matrix, designed to evaluate the cortical O2 partial pressure, was placed vertically to the artery and afterwards multiple regio...

  15. Sodium setpoint and gradient in bicarbonate hemodialysis.

    Science.gov (United States)

    Basile, Carlo; Libutti, Pasquale; Lisi, Piero; Vernaglione, Luigi; Casucci, Francesco; Losurdo, Nicola; Teutonico, Annalisa; Lomonte, Carlo

    2013-01-01

    The demonstration of an individual osmolar setpoint in hemodialysis (HD) is crucial to individualize dialysate sodium concentrations. Furthermore, the diffusive gradient between plasma and dialysate sodium is important in the "fine tuning" of the intradialytic sodium mass balance (MB). The design of this study included part A: a retrospective analysis of predialysis plasma sodium concentrations extracted from a 6-year database in our HD population (147 prevalent white anuric patients); and part B: study of intradialytic sodium kinetics in 48 patients undergoing one 4-hour bicarbonate HD session. Direct potentiometry with an ion-selective electrode was used for sodium measurements. Study part A: the mean number of plasma sodium measurements per patient was 16.06 ± 14.03 over a mean follow-up of 3.55 ± 1.76 years. The mean of the averaged plasma sodium concentrations was 136.7 ± 2.1 mmol/L, with a low mean intraindividual coefficient of variation (1.39 ± 0.4). Study part B: mean predialysis and postdialysis plasma sodium concentrations were 135.8 ± 0.9 and 138.0 ± 0.9 mmol/L (p<0.001). Mean inlet dialyzer sodium concentration was 138.7 ± 1.1 mmol/L; the hourly diffusion concentration gradients showed a statistically significant transfer from dialysate to plasma (Wilks ? <0.0001). A statistically significant relationship was found between sodium MB and diffusion gradient (p<0.02), and between sodium MB and ultrafiltration volume (p<0.01). A relatively "fixed" and individual osmolar setpoint in HD patients was shown for the first time in a long-term follow-up. A dialysate sodium concentration of 140 mmol/L determined a dialysate to plasma sodium gradient.

  16. High gradient accelerators for linear light sources

    International Nuclear Information System (INIS)

    Barletta, W.A.

    1988-01-01

    Ultra-high gradient radio frequency linacs powered by relativistic klystrons appear to be able to provide compact sources of radiation at XUV and soft x-ray wavelengths with a duration of 1 picosecond or less. This paper provides a tutorial review of the physics applicable to scaling the present experience of the accelerator community to the regime applicable to compact linear light sources. 22 refs., 11 figs., 21 tabs

  17. CERN/KEK: Very high accelerating gradients

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1993-01-15

    Full text: A world-wide effort is under way to develop linear electron-positron colliders so that physics experiments can be extended into a range of energies where circular machines (necessarily much larger than CERN's 27-kilometre LEP machine) would be crippled by synchrotron radiation. CERN is studying the feasibility of building a 2 TeV machine called CLIC powered not by individual klystrons, but by a high intensity electron 'drive' linac running parallel to the main linac (November 1990, page 7). This drive linac will itself be powered by similar superconducting cavities to those developed for LEP. A high gradient is an obvious design aim for any future high energy linear collider because it makes it shorter and therefore cheaper - the design figure for the CLIC machine is 80 MV/m. The CLIC study group has taken a significant step forward in demonstrating the technical feasibility of their machine by achieving peak and average accelerating gradients of 137 MV/m and 84 MV/m respectively in a short section of accelerating structure during high gradient tests at the Japanese KEK Laboratory last year. This result obtained within the framework of a CERN/KEK collaboration on linear colliders was obtained using a 20-cell accelerating section built at CERN using state-of the- art technology which served both as a model for CLIC studies as well as a prototype for the Japanese Linear Collider studies. The operating frequency of the model accelerating section is 2.6 times lower than the CLIC frequency but was chosen because a high power r.f. source and pulse compression scheme has been developed for this frequency at KEK. Testing CLIC models at 11.4 GHz is however more stringent than at 30 GHz because the chance of electrical breakdown increases as the frequency is lowered. This recent result clearly demonstrates that a gradient of 80 MV/m is feasible.

  18. Error Estimation in Preconditioned Conjugate Gradients

    Czech Academy of Sciences Publication Activity Database

    Strakoš, Zdeněk; Tichý, Petr

    2005-01-01

    Roč. 45, - (2005), s. 789-817 ISSN 0006-3835 R&D Projects: GA AV ČR 1ET400300415; GA AV ČR KJB1030306 Institutional research plan: CEZ:AV0Z10300504 Keywords : preconditioned conjugate gradient method * error bounds * stopping criteria * evaluation of convergence * numerical stability * finite precision arithmetic * rounding errors Subject RIV: BA - General Mathematics Impact factor: 0.509, year: 2005

  19. Conjugate gradient optimization programs for shuttle reentry

    Science.gov (United States)

    Powers, W. F.; Jacobson, R. A.; Leonard, D. A.

    1972-01-01

    Two computer programs for shuttle reentry trajectory optimization are listed and described. Both programs use the conjugate gradient method as the optimization procedure. The Phase 1 Program is developed in cartesian coordinates for a rotating spherical earth, and crossrange, downrange, maximum deceleration, total heating, and terminal speed, altitude, and flight path angle are included in the performance index. The programs make extensive use of subroutines so that they may be easily adapted to other atmospheric trajectory optimization problems.

  20. M-step preconditioned conjugate gradient methods

    Science.gov (United States)

    Adams, L.

    1983-01-01

    Preconditioned conjugate gradient methods for solving sparse symmetric and positive finite systems of linear equations are described. Necessary and sufficient conditions are given for when these preconditioners can be used and an analysis of their effectiveness is given. Efficient computer implementations of these methods are discussed and results on the CYBER 203 and the Finite Element Machine under construction at NASA Langley Research Center are included.

  1. Pressure gradient turbulent transport and collisionless reconnection

    International Nuclear Information System (INIS)

    Connor, J.W.

    1993-01-01

    The scale invariance technique is employed to discuss pressure gradient driven turbulent transport when an Ohm's law with electron inertia, rather than resistivity, is relevant. An expression for thermal diffusivity which has many features appropriate to L-mode transport in tokamaks, is seen to have greater generality than indicated by their particular calculation. The results of applying the technique to a more appropriate collisionless Ohm's law are discussed. (Author)

  2. CERN/KEK: Very high accelerating gradients

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    Full text: A world-wide effort is under way to develop linear electron-positron colliders so that physics experiments can be extended into a range of energies where circular machines (necessarily much larger than CERN's 27-kilometre LEP machine) would be crippled by synchrotron radiation. CERN is studying the feasibility of building a 2 TeV machine called CLIC powered not by individual klystrons, but by a high intensity electron 'drive' linac running parallel to the main linac (November 1990, page 7). This drive linac will itself be powered by similar superconducting cavities to those developed for LEP. A high gradient is an obvious design aim for any future high energy linear collider because it makes it shorter and therefore cheaper - the design figure for the CLIC machine is 80 MV/m. The CLIC study group has taken a significant step forward in demonstrating the technical feasibility of their machine by achieving peak and average accelerating gradients of 137 MV/m and 84 MV/m respectively in a short section of accelerating structure during high gradient tests at the Japanese KEK Laboratory last year. This result obtained within the framework of a CERN/KEK collaboration on linear colliders was obtained using a 20-cell accelerating section built at CERN using state-of the- art technology which served both as a model for CLIC studies as well as a prototype for the Japanese Linear Collider studies. The operating frequency of the model accelerating section is 2.6 times lower than the CLIC frequency but was chosen because a high power r.f. source and pulse compression scheme has been developed for this frequency at KEK. Testing CLIC models at 11.4 GHz is however more stringent than at 30 GHz because the chance of electrical breakdown increases as the frequency is lowered. This recent result clearly demonstrates that a gradient of 80 MV/m is feasible

  3. Designing optimal nanofocusing with a gradient hyperlens

    Directory of Open Access Journals (Sweden)

    Shen Lian

    2017-11-01

    Full Text Available We report the design of a high-throughput gradient hyperbolic lenslet built with real-life materials and capable of focusing a beam into a deep sub-wavelength spot of λ/23. This efficient design is achieved through high-order transformation optics and circular effective-medium theory (CEMT, which are used to engineer the radially varying anisotropic artificial material based on the thin alternating cylindrical metal and dielectric layers. The radial gradient of the effective anisotropic optical constants allows for matching the impedances at the input and output interfaces, drastically improving the throughput of the lenslet. However, it is the use of the zeroth-order CEMT that enables the practical realization of a gradient hyperlens with realistic materials. To illustrate the importance of using the CEMT versus the conventional planar effective-medium theory (PEMT for cylindrical anisotropic systems, such as our hyperlens, both the CEMT and PEMT are adopted to design gradient hyperlenses with the same materials and order of elemental layers. The CEMT- and PEMT-based designs show similar performance if the number of metal-dielectric binary layers is sufficiently large (9+ pairs and if the layers are sufficiently thin. However, for the manufacturable lenses with realistic numbers of layers (e.g. five pairs and thicknesses, the performance of the CEMT design continues to be practical, whereas the PEMT-based design stops working altogether. The accurate design of transformation optics-based layered cylindrical devices enabled by CEMT allow for a new class of robustly manufacturable nanophotonic systems, even with relatively thick layers of real-life materials.

  4. Calibration of a rotating accelerometer gravity gradiometer using centrifugal gradients

    Science.gov (United States)

    Yu, Mingbiao; Cai, Tijing

    2018-05-01

    The purpose of this study is to calibrate scale factors and equivalent zero biases of a rotating accelerometer gravity gradiometer (RAGG). We calibrate scale factors by determining the relationship between the centrifugal gradient excitation and RAGG response. Compared with calibration by changing the gravitational gradient excitation, this method does not need test masses and is easier to implement. The equivalent zero biases are superpositions of self-gradients and the intrinsic zero biases of the RAGG. A self-gradient is the gravitational gradient produced by surrounding masses, and it correlates well with the RAGG attitude angle. We propose a self-gradient model that includes self-gradients and the intrinsic zero biases of the RAGG. The self-gradient model is a function of the RAGG attitude, and it includes parameters related to surrounding masses. The calibration of equivalent zero biases determines the parameters of the self-gradient model. We provide detailed procedures and mathematical formulations for calibrating scale factors and parameters in the self-gradient model. A RAGG physical simulation system substitutes for the actual RAGG in the calibration and validation experiments. Four point masses simulate four types of surrounding masses producing self-gradients. Validation experiments show that the self-gradients predicted by the self-gradient model are consistent with those from the outputs of the RAGG physical simulation system, suggesting that the presented calibration method is valid.

  5. Self-organization of intracellular gradients during mitosis

    Directory of Open Access Journals (Sweden)

    Fuller Brian G

    2010-01-01

    Full Text Available Abstract Gradients are used in a number of biological systems to transmit spatial information over a range of distances. The best studied are morphogen gradients where information is transmitted over many cell lengths. Smaller mitotic gradients reflect the need to organize several distinct events along the length of the mitotic spindle. The intracellular gradients that characterize mitosis are emerging as important regulatory paradigms. Intracellular gradients utilize intrinsic auto-regulatory feedback loops and diffusion to establish stable regions of activity within the mitotic cytosol. We review three recently described intracellular mitotic gradients. The Ran GTP gradient with its elaborate cascade of nuclear transport receptors and cargoes is the best characterized, yet the dynamics underlying the robust gradient of Ran-GTP have received little attention. Gradients of phosphorylation have been observed on Aurora B kinase substrates both before and after anaphase onset. In both instances the phosphorylation gradient appears to result from a soluble gradient of Aurora B kinase activity. Regulatory properties that support gradient formation are highlighted. Intracellular activity gradients that regulate localized mitotic events bare several hallmarks of self-organizing biologic systems that designate spatial information during pattern formation. Intracellular pattern formation represents a new paradigm in mitotic regulation.

  6. Variable high gradient permanent magnet quadrupole (QUAPEVA)

    Science.gov (United States)

    Marteau, F.; Ghaith, A.; N'Gotta, P.; Benabderrahmane, C.; Valléau, M.; Kitegi, C.; Loulergue, A.; Vétéran, J.; Sebdaoui, M.; André, T.; Le Bec, G.; Chavanne, J.; Vallerand, C.; Oumbarek, D.; Cosson, O.; Forest, F.; Jivkov, P.; Lancelot, J. L.; Couprie, M. E.

    2017-12-01

    Different applications such as laser plasma acceleration, colliders, and diffraction limited light sources require high gradient quadrupoles, with strength that can reach up to 200 T/m for a typical 10 mm bore diameter. We present here a permanent magnet based quadrupole (so-called QUAPEVA) composed of a Halbach ring and surrounded by four permanent magnet cylinders. Its design including magnetic simulation modeling enabling us to reach 201 T/m with a gradient variability of 45% and mechanical issues are reported. Magnetic measurements of seven systems of different lengths are presented and confirmed the theoretical expectations. The variation of the magnetic center while changing the gradient strength is ±10 μm. A triplet of QUAPEVA magnets is used to efficiently focus a beam with large energy spread and high divergence that is generated by a Laser Plasma Acceleration source for a free electron laser demonstration and has enabled us to perform beam based alignment and control the dispersion of the beam.

  7. Air temperature gradient in large industrial hall

    Science.gov (United States)

    Karpuk, Michał; Pełech, Aleksander; Przydróżny, Edward; Walaszczyk, Juliusz; Szczęśniak, Sylwia

    2017-11-01

    In the rooms with dominant sensible heat load, volume airflow depends on many factors incl. pre-established temperature difference between exhaust and supply airflow. As the temperature difference is getting higher, airflow volume drops down, consequently, the cost of AHU is reduced. In high industrial halls with air exhaust grids located under the ceiling additional temperature gradient above working zone should be taken into consideration. In this regard, experimental research of the vertical air temperature gradient in high industrial halls were carried out for the case of mixing ventilation system The paper presents the results of air temperature distribution measurements in high technological hall (mechanically ventilated) under significant sensible heat load conditions. The supply airflow was delivered to the hall with the help of the swirl diffusers while exhaust grids were located under the hall ceiling. Basing on the air temperature distribution measurements performed on the seven pre-established levels, air temperature gradient in the area between 2.0 and 7.0 m above the floor was calculated and analysed.

  8. Crosswind Shear Gradient Affect on Wake Vortices

    Science.gov (United States)

    Proctor, Fred H.; Ahmad, Nashat N.

    2011-01-01

    Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.

  9. Gradient Dynamics and Entropy Production Maximization

    Science.gov (United States)

    Janečka, Adam; Pavelka, Michal

    2018-01-01

    We compare two methods for modeling dissipative processes, namely gradient dynamics and entropy production maximization. Both methods require similar physical inputs-how energy (or entropy) is stored and how it is dissipated. Gradient dynamics describes irreversible evolution by means of dissipation potential and entropy, it automatically satisfies Onsager reciprocal relations as well as their nonlinear generalization (Maxwell-Onsager relations), and it has statistical interpretation. Entropy production maximization is based on knowledge of free energy (or another thermodynamic potential) and entropy production. It also leads to the linear Onsager reciprocal relations and it has proven successful in thermodynamics of complex materials. Both methods are thermodynamically sound as they ensure approach to equilibrium, and we compare them and discuss their advantages and shortcomings. In particular, conditions under which the two approaches coincide and are capable of providing the same constitutive relations are identified. Besides, a commonly used but not often mentioned step in the entropy production maximization is pinpointed and the condition of incompressibility is incorporated into gradient dynamics.

  10. Diffusiophoresis in one-dimensional solute gradients

    Energy Technology Data Exchange (ETDEWEB)

    Ault, Jesse T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Warren, Patrick B. [Unilever R& D Port Sunlight, Bebington (United Kingdom); Shin, Sangwoo [Univ. of Hawaii at Manoa, Honolulu, HI (United States); Stone, Howard A. [Princeton Univ., Princeton, NJ (United States)

    2017-11-06

    Here, the diffusiophoretic motion of suspended colloidal particles under one-dimensional solute gradients is solved using numerical and analytical techniques. Similarity solutions are developed for the injection and withdrawal dynamics of particles into semi-infinite pores. Furthermore, a method of characteristics formulation of the diffusion-free particle transport model is presented and integrated to realize particle trajectories. Analytical solutions are presented for the limit of small particle diffusiophoretic mobility Γp relative to the solute diffusivity Ds for particle motions in both semi-infinite and finite domains. Results confirm the build up of local maxima and minima in the propagating particle front dynamics. The method of characteristics is shown to successfully predict particle motions and the position of the particle front, although it fails to accurately predict suspended particle concentrations in the vicinity of sharp gradients, such as at the particle front peak seen in some injection cases, where particle diffusion inevitably plays an important role. Results inform the design of applications in which the use of applied solute gradients can greatly enhance particle injection into and withdrawal from pores.

  11. Diffusiophoresis in one-dimensional solute gradients

    International Nuclear Information System (INIS)

    Ault, Jesse T.; Warren, Patrick B.; Shin, Sangwoo; Stone, Howard A.

    2017-01-01

    Here, the diffusiophoretic motion of suspended colloidal particles under one-dimensional solute gradients is solved using numerical and analytical techniques. Similarity solutions are developed for the injection and withdrawal dynamics of particles into semi-infinite pores. Furthermore, a method of characteristics formulation of the diffusion-free particle transport model is presented and integrated to realize particle trajectories. Analytical solutions are presented for the limit of small particle diffusiophoretic mobility Γ p relative to the solute diffusivity D s for particle motions in both semi-infinite and finite domains. Results confirm the build up of local maxima and minima in the propagating particle front dynamics. The method of characteristics is shown to successfully predict particle motions and the position of the particle front, although it fails to accurately predict suspended particle concentrations in the vicinity of sharp gradients, such as at the particle front peak seen in some injection cases, where particle diffusion inevitably plays an important role. Results inform the design of applications in which the use of applied solute gradients can greatly enhance particle injection into and withdrawal from pores.

  12. Growth of fibroblasts and endothelial cells on wettability gradient surfaces

    NARCIS (Netherlands)

    Ruardy, TG; Moorlag, HE; Schakenraad, JM; VanderMei, HC; Busscher, HJ

    1997-01-01

    The growth, spreading, and shape of human skin fibroblasts (PK 84) and human umbilical cord endothelial cells on dichlorodimethylsilane (DDS) and dimethyloctadecylchlorosilane (DOGS) gradient surfaces were investigated in the presence of serum proteins. Gradient surfaces were prepared on glass using

  13. A strain gradient plasticity theory with application to wire torsion

    KAUST Repository

    Liu, J. X.; El Sayed, Tamer S.

    2014-01-01

    Based on the framework of the existing strain gradient plasticity theories, we have examined three kinds of relations for the plastic strain dependence of the material intrinsic length scale, and thus developed updated strain gradient plasticity

  14. Psicodrama del duelo.

    OpenAIRE

    José Antonio Espina Barrio; Marisol Filgueira Bouza

    1997-01-01

    La pérdida de rituales agrava y alarga la reacción del duelo. Se define el Psicodrama Antropológico y su intervención en el proceso del duelo. El Psicodrama Focal del Duelo es una psicoterapia breve centrada en el proceso de Duelo. Se comentan varios casos y resultados. Se concluye con un programa sencillo para el duelo en Atención Primaria.

  15. Recognition of handwritten characters using local gradient feature descriptors

    NARCIS (Netherlands)

    Surinta, Olarik; Karaaba, Mahir F.; Schomaker, Lambert R.B.; Wiering, Marco A.

    2015-01-01

    Abstract In this paper we propose to use local gradient feature descriptors, namely the scale invariant feature transform keypoint descriptor and the histogram of oriented gradients, for handwritten character recognition. The local gradient feature descriptors are used to extract feature vectors

  16. Fractura triple del complejo suspensorio del hombro

    Directory of Open Access Journals (Sweden)

    Eraclio Delgado Rifá

    2015-06-01

    Full Text Available El complejo suspensorio del hombro es una estructura sumamente importante, compuesta por un anillo de huesos y tejidos blandos. Las lesiones aisladas de este complejo anatómico son frecuentes y no afectan su estabilidad. La interrupción doble conduce a la inestabilidad de esta estructura y usualmente requiere tratamiento quirúrgico. La triple interrupción, por su parte, es sumamente rara y es encontrada en casos de trauma de alta energía a menudo en asociación con otras lesiones. Se presenta una triple lesión del complejo suspensorio del hombro en un paciente de 46 años de edad, con una fractura de la glenoides, del acromion tipo III de Kuhn y de la coracoides tipo II de Ogawa. En este caso, la fractura del acromion fue tratada con fijación percutánea con alambres de Kirschner, por tener asociado lesiones de partes blandas que contraindicaron la reducción abierta. La fractura de la glenoides y de la apófisis coracoides fueron tratadas conservadoramente. Después de 6 meses de evolución, el paciente tuvo un resultado funcional aceptable, con una abducción de 90 grados, los 30 grados de rotación externa y 70 de rotación interna, además asintomático y consolidación de todas las fracturas. A pesar de ser catalogada de una lesión grave del cinturón escapular y estar asociada a otras lesiones se obtuvo un resultado satisfactorio al final del tratamiento.

  17. L'area faunistica del camoscio appenninico (Rupicapra pyrenaica ornata di Lama dei Peligni. Evoluzione del nucleo e problemi gestionali

    Directory of Open Access Journals (Sweden)

    L. Gentile

    2003-10-01

    Full Text Available L'Area Faunistica del Camoscio appenninico di Lama dei Peligni (CH nel Parco Nazionale della Majella è stata istituita nel 1990 con lo scopo principale di fungere da serbatoio di animali da utilizzare per operazioni di rinforzo della popolazione di Camosci in natura. Inoltre è stata ed è un notevole strumento per sensibilizzare la popolazione ed il pubblico alla conservazione della specie nonché una forte attrazione turistica per l'intera Valle dell'Aventino nel Parco Nazionale della Majella. L'Area Faunistica è ubicata nei pressi del centro abitato di Lama dei Peligni (CH sul versante Orientale della Majella ad un'altitudine che va dai 750 agli 850 m s.l.m. ed ha un'astensione complessiva di 4,2 ettari. Nel corso degli anni è stato necessario suddividere il recinto in 4 subrecinti per poter disporre di spazi separati utili per la gestione sanitaria del nucleo di animali ospitati. Inizialmente la responsabilità tecnica amministrativa è stata curata dal Parco Nazionale d'Abruzzo in collaborazione con il WWF Italia, successivamente è stata curata dalla Riserva Regionale "Majella Orientale" per passare dal 2000 all'Ente Parco Nazionale della Majella. L'area faunistica di Lama dei Peligni è stata attivata con l'immissione di un maschio prelevato in natura dalla popolazione della Val di Rose nel Parco Nazionale d'Abruzzo, Lazio e Molise e 5 femmine provenienti dal'Area Faunistica di Bisegna nel medesimo Parco. Nel periodo dal 1990 al 2002 sono nati 37 camosci e ne sono deceduti 20. Inoltre si sono verificati 14 rientri di animali provenienti dalla popolazione in natura e dall'Area Faunistica sono stati reimmessi 25 capi sul massiccio della Majella. L'Area di Lama dei Peligni ha consentito l'attivazione di un'ulteriore Area Faunistica nel Parco Nazionale del Gran Sasso Monti della Laga fornendo 1 femmina. Lo scopo principale del presente lavoro è di analizzare criticamente i dati raccolti in un database e di individuare un protocollo di

  18. Vigencia del Darwinismo

    OpenAIRE

    Lessa, Enrique P

    2009-01-01

    En este ensayo se presenta una revisión histórica del signifcado y legado del darwinismo, con énfasis en el último siglo. La principal conclusión es que la visión darwiniana de la evolución, con las modifcaciones requeridas para dar cuenta de los grandes desarrollos de la disciplina, se ha impuesto y mantiene vigencia en nuestros días. En particular, el papel del azar, la evolución como proceso de “descendencia con modifcación” a lo largo de diversas ramas del árbol de la vida, el pensamiento...

  19. Is the temperature gradient or the derivative of the density gradient responsible for drift solitons?

    International Nuclear Information System (INIS)

    Salat, A.

    1990-01-01

    In conventional drift wave theory the density gradient κ n =d lnn/dχ determines the linear phase velocity, and the (electron) temperature gradient κ T =d lnT/dχ gives rise to a nonlinear term which leads to the existence of soliton-type solutions and solitary waves. LAKHIN, MIKHAILOVSKI and ONISHCHENKO, Phys. Lett. A 119, 348 (1987) and Plasma Phys. and Contr. Fus. 30, 457 (1988), recently claimed that it is not κ T but essentially the derivative of the density gradient, dκ n /dχ, that is relevant. This claim is refuted by means of an expansion scheme in ε=eΦ/T≤1, where Φ is the drift wave potential. (orig.)

  20. TASAS DE RECAMBIO FLORÍSTICO DE GÉNEROS EN BOSQUES MONTANOS DEL NEOTRÓPICO

    Directory of Open Access Journals (Sweden)

    López Wilson

    2010-06-01

    Full Text Available Se evaluó la tasa de recambio fl orístico en bosques de alta montaña (por encima delos 1500 m.s.n.m. al nivel taxonómico de géneros en dos áreas geográfi cas y surelación con factores espaciales, climáticos y históricos. Las áreas defi nidas fueron:1 Colombia, la cual se defi ne para los sitios en este país localizados alrededor delEcuador geográfi co; y 2 Neotrópico: sitios externos a Colombia más distantesdel Ecuador geográfi co. Las preguntas a responder fueron: ¿Qué tan comparablesson las tasas de recambio fl orístico de géneros en las diferentes áreas geográfi cas?y ¿Qué tan similares son los factores que controlan la distribución de géneros?La diversidad beta fue diferente según el área geográfi ca. La variación climática,representada por la precipitación, fue más relevante a escala del neotrópico, mientrasque la variación altitudinal lo fue a escala de Colombia. Los patrones de distribuciónal nivel de género, fueron poco congruentes con los reportados a nivel de especiesen bosques montanos del neotrópico, especialmente cuando se consideraron datoscercanos alrededor del Ecuador geográfi co en Colombia.

  1. Tunable high-gradient permanent magnet quadrupoles

    CERN Document Server

    Shepherd, B J A; Marks, N; Collomb, N A; Stokes, D G; Modena, M; Struik, M; Bartalesi, A

    2014-01-01

    A novel type of highly tunable permanent magnet (PM) based quadrupole has been designed by the ZEPTO collaboration. A prototype of the design (ZEPTO-Q1), intended to match the specification for the CLIC Drive Beam Decelerator, was built and magnetically measured at Daresbury Laboratory and CERN. The prototype utilises two pairs of PMs which move in opposite directions along a single vertical axis to produce a quadrupole gradient variable between 15 and 60 T/m. The prototype meets CLIC's challenging specification in terms of the strength and tunability of the magnet.

  2. Stereo vision with distance and gradient recognition

    Science.gov (United States)

    Kim, Soo-Hyun; Kang, Suk-Bum; Yang, Tae-Kyu

    2007-12-01

    Robot vision technology is needed for the stable walking, object recognition and the movement to the target spot. By some sensors which use infrared rays and ultrasonic, robot can overcome the urgent state or dangerous time. But stereo vision of three dimensional space would make robot have powerful artificial intelligence. In this paper we consider about the stereo vision for stable and correct movement of a biped robot. When a robot confront with an inclination plane or steps, particular algorithms are needed to go on without failure. This study developed the recognition algorithm of distance and gradient of environment by stereo matching process.

  3. Higher-order force gradient symplectic algorithms

    Science.gov (United States)

    Chin, Siu A.; Kidwell, Donald W.

    2000-12-01

    We show that a recently discovered fourth order symplectic algorithm, which requires one evaluation of force gradient in addition to three evaluations of the force, when iterated to higher order, yielded algorithms that are far superior to similarly iterated higher order algorithms based on the standard Forest-Ruth algorithm. We gauge the accuracy of each algorithm by comparing the step-size independent error functions associated with energy conservation and the rotation of the Laplace-Runge-Lenz vector when solving a highly eccentric Kepler problem. For orders 6, 8, 10, and 12, the new algorithms are approximately a factor of 103, 104, 104, and 105 better.

  4. Impact of Ozone Gradient on Grapevine Leaves

    Science.gov (United States)

    Alebic-Juretic, Ana; Bokan-Vucelic, Itana; Mifka, Boris; Zatezalo, Marija; Zubak, Velimir

    2017-04-01

    Due to complex orography and air mass circulation, the Rijeka Bay area is characterized by O3 gradient, with concentrations risen with the altitude (1). Therefore AOT40 values were often exceeded and should result in harmful effects on vegetation. Based on previous controlled experiments (2), we examined the possible effect of atmospheric ozone on grape leaves under natural O3 gradient. Grapevine leaves (2-5) were collected from May to September 2016 at two sampling points in the proximity of two AQM stations: Site 1 in the city centre (20m asl) and Site 2 (186m asl) in the suburban settlement. Subsequent to weighing and determination of surface area, the leaves (0,5 g) were extracted in 95% ethanol and analysed on chlorophyl a (Chla), chlorophyl b (Chlb) and carotene (Car) content by UV-VIS spectrometry on 3 wavelengths (664, 649, 470 nm) (3) In summer 2016 O3 gradient was not that pronounced as usual (1), but stil the concentrations differed by approx. 20%, exceeding national AOT40 value at both sites (22.360 and 28.061 μg m-3 h, respectively, at Sites 1 and 2). The concentrations of other pollutants were bellow limit values (LV). The Cha and Chb in a sample leaves collected at the end of May at Site 2 are equal to that with filtered O3 in control experiment (2), i.e. without damage caused by ozone, while the Car content is lower approx. 50% and is kept at the same level. The con-centrations of pigments obtained in July prooved the possible damage by O3, while in subsequent months could speed up natural ageing. This is the first evidence of O3 damage on plants in the Rijeka Bay area, in spite of weaker O3 gradient and lacking visible signs of damage. Preliminary results indicate the need for more frequent sampling, particularly in the period included in AOT40 (May-July). References: 1. Alebić-Juretić A (2012) Int J Remote Sensing, 33(2): 335-345 2. Britvec M, Reichenauer T, Soja G., Ljubešić N, Pećina M (2001) Biologia (Bratislava),56/4: 417-424 3. Sumanata

  5. Gradient-index optics fundamentals and applications

    CERN Document Server

    Gomez-Reino, Carlos; Bao, Carmen

    2010-01-01

    Gradient-Index (GRIN) optics provides a comprehensive and thorough treatment on fundamentals and applications of light propagation through inhomogeneous media. The book can be used both as a classroom text for students in physics and engineering and as a reference for specialists. A description of the phenomena, components and technology used in GRIN Optics are presented. The relationship to lenses, waveguides, optical connections, spatial solitons and vision is demonstrated. Applications of GRIN components and hybrid structures for optical connections, optical sensing and Talbot effect are analyzed.

  6. Microfluidic high gradient magnetic cell separation

    Science.gov (United States)

    Inglis, David W.; Riehn, Robert; Sturm, James C.; Austin, Robert H.

    2006-04-01

    Separation of blood cells by native susceptibility and by the selective attachment of magnetic beads has recently been demonstrated on microfluidic devices. We discuss the basic principles of how forces are generated via the magnetic susceptibility of an object and how microfluidics can be combined with micron-scale magnetic field gradients to greatly enhance in principle the fractionating power of magnetic fields. We discuss our efforts and those of others to build practical microfluidic devices for the magnetic separation of blood cells. We also discuss our attempts to integrate magnetic separation with other microfluidic features for developing handheld medical diagnostic tools.

  7. Quasi parton distributions and the gradient flow

    International Nuclear Information System (INIS)

    Monahan, Christopher; Orginos, Kostas

    2017-01-01

    We propose a new approach to determining quasi parton distribution functions (PDFs) from lattice quantum chromodynamics. By incorporating the gradient flow, this method guarantees that the lattice quasi PDFs are finite in the continuum limit and evades the thorny, and as yet unresolved, issue of the renormalization of quasi PDFs on the lattice. In the limit that the flow time is much smaller than the length scale set by the nucleon momentum, the moments of the smeared quasi PDF are proportional to those of the lightfront PDF. Finally, we use this relation to derive evolution equations for the matching kernel that relates the smeared quasi PDF and the light-front PDF.

  8. Human impact gradient on mammalian biodiversity

    Directory of Open Access Journals (Sweden)

    Mariana Munguía

    2016-04-01

    Full Text Available Drastic changes have been caused by human influence in natural landscapes, which may exert an intensive effect on species loss. However, species loss from human pressure is not random but depends on a series of environmentally associated factors. Linking species traits to environmental attributes may allow us to detect the ecological impacts of habitat so that meaningful habitat degradation gradients can be identified. The relationships between environmental factors and species traits provide the basis for identifying those biological traits that make species more sensitive to disturbance. These relationships are also helpful to detect the geographic distribution of latent risk to reveal areas where biodiversity is threatened. Here, we identify a “Human Impact Gradient for Biodiversity (HIGB” based on a three-table ordination method (RLQ analysis and fourth-corner analysis to identify key species traits that are associated with environmental gradient. Species distribution and environmental geographic data were gathered nationwide to analyze 68 localities, which represent 27% of Mexico’s surface, including 211 species of mammals. Nine environmental variables (including biophysical, geophysical and land-use impacts were analyzed by using the Geographic Information System. Three types of species’ traits were evaluated: locomotion, trophic habit and body size. We identified a human impact gradient, which was mainly determined by the percentage of the area that was covered by seedlings, the plant richness, the understory coverage percentage and the human settlement index. The most important species traits that are associated with non-human-impacted sites were carnivores, frugivores–herbivores and a body size that was greater than 17.8 kg; 25 species were selected by the decision criteria framework for species that were sensitive to degradation based on ecological function information. Conversely, granivores, fossorial and semifossorial

  9. PET regularization by envelope guided conjugate gradients

    International Nuclear Information System (INIS)

    Kaufman, L.; Neumaier, A.

    1996-01-01

    The authors propose a new way to iteratively solve large scale ill-posed problems and in particular the image reconstruction problem in positron emission tomography by exploiting the relation between Tikhonov regularization and multiobjective optimization to obtain iteratively approximations to the Tikhonov L-curve and its corner. Monitoring the change of the approximate L-curves allows us to adjust the regularization parameter adaptively during a preconditioned conjugate gradient iteration, so that the desired solution can be reconstructed with a small number of iterations

  10. Theory of resistivity-gradient-driven turbulence

    International Nuclear Information System (INIS)

    Garcia, L.; Carreras, B.A.; Diamond, P.H.; Callen, J.D.

    1984-10-01

    A theory of the nonlinear evolution and saturation of resistivity-driven turbulence, which evolves from linear rippling instabilities, is presented. The nonlinear saturation mechanism is identified both analytically and numerically. Saturation occurs when the turbulent diffusion of the resistivity is large enough so that dissipation due to parallel electron thermal conduction balances the nonlinearly modified resistivity gradient driving term. The levels of potential, resistivity, and density fluctuations at saturation are calculated. A combination of computational modeling and analytic treatment is used in this investigation

  11. Mullite-alumina functionally gradient ceramics

    International Nuclear Information System (INIS)

    Pena, P.; Bartolome, J.; Requena, J.; Moya, J.S.

    1993-01-01

    Cracks free mullite-alumina Functionally Gradient Ceramics (FGC) have been obtained by sequential slip casting of Mullite-alumina slurries with different mullite/alumina ratios. These slurries were prepared with 65 % solids content and viscosities ranging from 10 to 40 mPa.s. The presence of cracks perpendicular to the FGC layers have been attributed to residual stresses developed because of the mismatch in thermal expansion between layers. The microstructure of the different layers, and de residual stress value σ R in each layer was also determined. (orig.)

  12. A method for easily customizable gradient gel electrophoresis.

    Science.gov (United States)

    Miller, Andrew J; Roman, Brandon; Norstrom, Eric

    2016-09-15

    Gradient polyacrylamide gel electrophoresis is a powerful tool for the resolution of polypeptides by relative mobility. Here, we present a simplified method for generating polyacrylamide gradient gels for routine analysis without the need for specialized mixing equipment. The method allows for easily customizable gradients which can be optimized for specific polypeptide resolution requirements. Moreover, the method eliminates the possibility of buffer cross contamination in mixing equipment, and the time and resources saved with this method in place of traditional gradient mixing, or the purchase of pre-cast gels, are noteworthy given the frequency with which many labs use gradient gel SDS-PAGE. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Role of the vertical pressure gradient in wave boundary layers

    DEFF Research Database (Denmark)

    Jensen, Karsten Lindegård; Sumer, B. Mutlu; Vittori, Giovanna

    2014-01-01

    By direct numerical simulation (DNS) of the flow in an oscillatory boundary layer, it is possible to obtain the pressure field. From the latter, the vertical pressure gradient is determined. Turbulent spots are detected by a criterion involving the vertical pressure gradient. The vertical pressure...... gradient is also treated as any other turbulence quantity like velocity fluctuations and statistical properties of the vertical pressure gradient are calculated from the DNS data. The presence of a vertical pressure gradient in the near bed region has significant implications for sediment transport....

  14. Structural and compositional gradients: basic idea, preparation, applications

    International Nuclear Information System (INIS)

    Ilschner, B.

    1993-01-01

    The term gradient materials refers to gradients of chemical composition and/or microstructural parameters which are intentionally introduced into components of any kind of homogeneous or heterogeneous materials, including metallic alloys, ceramics, glasses, polymers, and composites. After a short review of the development of the gradient materials technology since 1972, some fundamental aspects concerning the effects of such gradients on physical or mechanical properties are discussed. A selection of technical applications which have been discussed recently is presented. Finally, different methods for the preparation of gradients from gaseous, liquid or powder precursors are reviewed. (orig.)

  15. SINOPSIS DE LOS ESCARABAJOS COPRÓFAGOS (COLEOPTERA: SCARABAEINAE DEL CARIBE COLOMBIANO

    Directory of Open Access Journals (Sweden)

    JORGE ARI NORIEGA

    2013-12-01

    Full Text Available La subfamilia Scarabaeinae (Coleoptera: Scarabaeidae es un grupo de gran importancia en los ecosistemas por su significativa participación en el proceso de reciclaje de nutrientes. Para Colombia existen algunos acercamientos al análisis de su diversidad en ciertas regiones biogeográficas. Sin embargo, existen zonas que necesitan un mayor estudio, como es el caso de la región Caribe. Con el fin de llenar el vacío de información se realizó una revisión de la información depositada en 16 colecciones a nivel nacional y de la literatura en esta zona. Se registran 90 especies pertenecientes a 24 géneros, agrupadas en seis tribus. Se reportan 20 nuevas especies para el departamento de La Guajira, 18 para Sucre, once para Magdalena, nueve para Bolívar, nueve para Córdoba, tres para Atlántico y dos para Cesar. El departamento con la mayor riqueza es Magdalena ya que es el mejor muestreado incluyendo su rango altitudinal. Al analizar la composición de especies, la región Caribe presenta pocos endemismos, exceptuando las zonas altas del Macizo de la Sierra Nevada de Santa Marta. El género Onthophagus es el más diverso en la región y la especie que presenta el mayor rango altitudinal es Ontherus sanctaemartae (700 hasta 2500 m . La región es homogénea en las zonas bajas, presentándose una mayor afinidad con el Chocó biogeográfico. Se establecen en la región cuatro grandes franjas altitudinales: planicies (0- 500 m , colinas altas (>500- 900 m , zona subandina-andina (> 900 a 2500 m y alta montaña (> 2500 m . Es posible que con el incremento de muestreos en zonas poco estudiadas la homogeneidad específica aumente. Finalmente, es necesario ampliar e intensificar los estudios en esta región, especialmente en los sistemas montañosos aislados.

  16. La luz del origen del universo

    Directory of Open Access Journals (Sweden)

    Casas, Alberto

    2015-10-01

    Full Text Available Penzias and Wilson discovered the cosmic microwave background, a luminous echo of the Big Bang, in 1965. The amount of information encoded in this relic of the early universe is truly extraordinary. At present, the most precise data about the origin and structure of the universe comes from the study of this primordial light, the full potential of which has yet to be explored.En 1965 se descubrió el fondo de radiación de microondas, un eco luminoso de la Gran Explosión (Big Bang. La cantidad de información contenida en esta reliquia del universo primitivo es verdaderamente extraordinaria. En la actualidad los datos más precisos sobre el origen y estructura del universo provienen del estudio de esta luz primigenia, que aún no ha sido explorada en todo su potencial.

  17. A substrate independent approach for generation of surface gradients

    Energy Technology Data Exchange (ETDEWEB)

    Goreham, Renee V. [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia); Mierczynska, Agnieszka; Pierce, Madelene [Ian Wark Research Institute, University of South Australia, Mawson Lakes 5095 (Australia); Short, Robert D.; Taheri, Shima; Bachhuka, Akash; Cavallaro, Alex; Smith, Louise E. [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia); Vasilev, Krasimir, E-mail: krasimir.vasilev@unisa.edu.au [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia)

    2013-01-01

    Recently, surface gradients have attracted significant interest for various research and technological applications. In this paper, we report a facile and versatile method for generating surface gradients of immobilized nanoparticles, nanotopography and ligands that is independent from the substrate material. The method consists of first depositing a functional polymer layer on a substrate and subsequent time controlled immersion of this functionalized substrate in solution gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) or poly (styrenesulfonate) (PSS). Chemical characterization by X-ray Photoelectron Spectroscopy (XPS) and morphological analysis by Atomic Force Microscopy (AFM) show that the density of nanoparticles and the concentration of PSS across the surface increases in a gradient manner. As expected, time of immersion determines the concentration of surface bound species. We also demonstrate the generation of surface gradients of pure nanotopography. This is achieved by depositing a 5 nm thick plasma polymer layer on top of the number density gradient of nanoparticles to achieve a homogeneous surface chemistry. The surface independent approach for generation of surface gradients presented in this paper may open opportunities for a wider use of surface gradient in research and in various technologies. - Highlights: ► We present a substrate independent approach for generation of surface gradients. ► We demonstrate well-defined density gradients of gold and silver nanoparticles. ► We provide an example of pure surface nanotopography gradients. ► We demonstrate concentration gradients of bound ligands.

  18. A substrate independent approach for generation of surface gradients

    International Nuclear Information System (INIS)

    Goreham, Renee V.; Mierczynska, Agnieszka; Pierce, Madelene; Short, Robert D.; Taheri, Shima; Bachhuka, Akash; Cavallaro, Alex; Smith, Louise E.; Vasilev, Krasimir

    2013-01-01

    Recently, surface gradients have attracted significant interest for various research and technological applications. In this paper, we report a facile and versatile method for generating surface gradients of immobilized nanoparticles, nanotopography and ligands that is independent from the substrate material. The method consists of first depositing a functional polymer layer on a substrate and subsequent time controlled immersion of this functionalized substrate in solution gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) or poly (styrenesulfonate) (PSS). Chemical characterization by X-ray Photoelectron Spectroscopy (XPS) and morphological analysis by Atomic Force Microscopy (AFM) show that the density of nanoparticles and the concentration of PSS across the surface increases in a gradient manner. As expected, time of immersion determines the concentration of surface bound species. We also demonstrate the generation of surface gradients of pure nanotopography. This is achieved by depositing a 5 nm thick plasma polymer layer on top of the number density gradient of nanoparticles to achieve a homogeneous surface chemistry. The surface independent approach for generation of surface gradients presented in this paper may open opportunities for a wider use of surface gradient in research and in various technologies. - Highlights: ► We present a substrate independent approach for generation of surface gradients. ► We demonstrate well-defined density gradients of gold and silver nanoparticles. ► We provide an example of pure surface nanotopography gradients. ► We demonstrate concentration gradients of bound ligands

  19. Cell orientation gradients on an inverse opal substrate.

    Science.gov (United States)

    Lu, Jie; Zou, Xin; Zhao, Ze; Mu, Zhongde; Zhao, Yuanjin; Gu, Zhongze

    2015-05-20

    The generation of cell gradients is critical for understanding many biological systems and realizing the unique functionality of many implanted biomaterials. However, most previous work can only control the gradient of cell density and this has no effect on the gradient of cell orientation, which has an important role in regulating the functions of many connecting tissues. Here, we report on a simple stretched inverse opal substrate for establishing desired cell orientation gradients. It was demonstrated that tendon fibroblasts on the stretched inverse opal gradient showed a corresponding alignment along with the elongation gradient of the substrate. This "random-to-aligned" cell gradient reproduces the insertion part of many connecting tissues, and thus, will have important applications in tissue engineering.

  20. Archivo del Duelo

    OpenAIRE

    Ferrera, Tamara

    2010-01-01

    Photos taken from the Archive of Mourning following the March 11 terrorist attacks El Archivo del Duelo. Creación de un archivo etnográfico de los Atentados del 11 de marzo en Madrid. Ministerio de Educación y Ciencia HUM2005-03490.

  1. Displasias del seno

    Directory of Open Access Journals (Sweden)

    Ernesto Andrade Valderrama

    1971-04-01

    Full Text Available En general, las Displasias no se presentan antes de la iniciación del estímulo Gonadal y tienden a desaparecer con el climaterio. Se definen entonces como las afecciones benignas del Seno, de origen endocrino.

  2. Asymmetric Uncertainty Expression for High Gradient Aerodynamics

    Science.gov (United States)

    Pinier, Jeremy T

    2012-01-01

    When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.

  3. Adaptive Gradient Multiobjective Particle Swarm Optimization.

    Science.gov (United States)

    Han, Honggui; Lu, Wei; Zhang, Lu; Qiao, Junfei

    2017-10-09

    An adaptive gradient multiobjective particle swarm optimization (AGMOPSO) algorithm, based on a multiobjective gradient (stocktickerMOG) method and a self-adaptive flight parameters mechanism, is developed to improve the computation performance in this paper. In this AGMOPSO algorithm, the stocktickerMOG method is devised to update the archive to improve the convergence speed and the local exploitation in the evolutionary process. Meanwhile, the self-adaptive flight parameters mechanism, according to the diversity information of the particles, is then established to balance the convergence and diversity of AGMOPSO. Attributed to the stocktickerMOG method and the self-adaptive flight parameters mechanism, this AGMOPSO algorithm not only has faster convergence speed and higher accuracy, but also its solutions have better diversity. Additionally, the convergence is discussed to confirm the prerequisite of any successful application of AGMOPSO. Finally, with regard to the computation performance, the proposed AGMOPSO algorithm is compared with some other multiobjective particle swarm optimization algorithms and two state-of-the-art multiobjective algorithms. The results demonstrate that the proposed AGMOPSO algorithm can find better spread of solutions and have faster convergence to the true Pareto-optimal front.

  4. The phenotypic variance gradient - a novel concept.

    Science.gov (United States)

    Pertoldi, Cino; Bundgaard, Jørgen; Loeschcke, Volker; Barker, James Stuart Flinton

    2014-11-01

    Evolutionary ecologists commonly use reaction norms, which show the range of phenotypes produced by a set of genotypes exposed to different environments, to quantify the degree of phenotypic variance and the magnitude of plasticity of morphometric and life-history traits. Significant differences among the values of the slopes of the reaction norms are interpreted as significant differences in phenotypic plasticity, whereas significant differences among phenotypic variances (variance or coefficient of variation) are interpreted as differences in the degree of developmental instability or canalization. We highlight some potential problems with this approach to quantifying phenotypic variance and suggest a novel and more informative way to plot reaction norms: namely "a plot of log (variance) on the y-axis versus log (mean) on the x-axis, with a reference line added". This approach gives an immediate impression of how the degree of phenotypic variance varies across an environmental gradient, taking into account the consequences of the scaling effect of the variance with the mean. The evolutionary implications of the variation in the degree of phenotypic variance, which we call a "phenotypic variance gradient", are discussed together with its potential interactions with variation in the degree of phenotypic plasticity and canalization.

  5. The multigrid preconditioned conjugate gradient method

    Science.gov (United States)

    Tatebe, Osamu

    1993-01-01

    A multigrid preconditioned conjugate gradient method (MGCG method), which uses the multigrid method as a preconditioner of the PCG method, is proposed. The multigrid method has inherent high parallelism and improves convergence of long wavelength components, which is important in iterative methods. By using this method as a preconditioner of the PCG method, an efficient method with high parallelism and fast convergence is obtained. First, it is considered a necessary condition of the multigrid preconditioner in order to satisfy requirements of a preconditioner of the PCG method. Next numerical experiments show a behavior of the MGCG method and that the MGCG method is superior to both the ICCG method and the multigrid method in point of fast convergence and high parallelism. This fast convergence is understood in terms of the eigenvalue analysis of the preconditioned matrix. From this observation of the multigrid preconditioner, it is realized that the MGCG method converges in very few iterations and the multigrid preconditioner is a desirable preconditioner of the conjugate gradient method.

  6. Performance evaluation of matrix gradient coils.

    Science.gov (United States)

    Jia, Feng; Schultz, Gerrit; Testud, Frederik; Welz, Anna Masako; Weber, Hans; Littin, Sebastian; Yu, Huijun; Hennig, Jürgen; Zaitsev, Maxim

    2016-02-01

    In this paper, we present a new performance measure of a matrix coil (also known as multi-coil) from the perspective of efficient, local, non-linear encoding without explicitly considering target encoding fields. An optimization problem based on a joint optimization for the non-linear encoding fields is formulated. Based on the derived objective function, a figure of merit of a matrix coil is defined, which is a generalization of a previously known resistive figure of merit for traditional gradient coils. A cylindrical matrix coil design with a high number of elements is used to illustrate the proposed performance measure. The results are analyzed to reveal novel features of matrix coil designs, which allowed us to optimize coil parameters, such as number of coil elements. A comparison to a scaled, existing multi-coil is also provided to demonstrate the use of the proposed performance parameter. The assessment of a matrix gradient coil profits from using a single performance parameter that takes the local encoding performance of the coil into account in relation to the dissipated power.

  7. A comparative assessment of the biological properties of soils in the cultural and native cenoses of the Central Caucasus (using the example of the Terskii variant of altitudinal zonality in Kabardino-Balkaria)

    Science.gov (United States)

    Gorobtsova, O. N.; Gedgafova, F. V.; Uligova, T. S.; Tembotov, R. Kh.

    2016-01-01

    The biological properties of the most widespread automorphic and hydromorphic soils of cultural and native cenoses in the Terskii variant of the altitudinal zonality (Kabardino-Balkaria) are compared. The data on the humus reserves in the 0- to 20-cm soil layer and those on the carbon content in the microbial biomass calculated on the basis of the results of substrate-induced respiration measurements are presented. The share of carbon in the microbial biomass of the total organic carbon in the soils was determined. Long-term (more than 70 years) farming on the studied soils significantly changed their biological properties. The humus content and its reserves became lower by 25-40%. The physiological activity of the microbial biomass in the cultural soils decreased by more than 60%. Presently, the soils of the cultural cenoses function as an entire natural system, but at a lower level of fertility; the loss of more than 30% of the bioorganic potential (the critical threshold of soil system stability) indicates the disturbance of soil ecological functions, their stability, and the capability of self-restoration.

  8. Three gradients and the perception of flat and curved surfaces.

    Science.gov (United States)

    Cutting, J E; Millard, R T

    1984-06-01

    Researchers of visual perception have long been interested in the perceived slant of a surface and in the gradients that purportedly specify it. Slant is the angle between the line of sight and the tangent to the planar surface at any point, also called the surface normal. Gradients are the sources of information that grade, or change, with visual angle as one looks from one's feet upward to the horizon. The present article explores three gradients--perspective, compression, and density--and the phenomenal impression of flat and curved surfaces. The perspective gradient is measured at right angles to the axis of tilt at any point in the optic array; that is, when looking down a hallway at the tiles of a floor receding in the distance, perspective is measured by the x-axis width of each tile projected on the image plane orthogonal to the line of sight. The compression gradient is the ratio of y/x axis measures on the projected plane. The density gradient is measured by the number of tiles per unit solid visual angle. For flat surfaces and many others, perspective and compression gradients decrease with distance, and the density gradient increases. We discuss the manner in which these gradients change for various types of surfaces. Each gradient is founded on a different assumption about textures on the surfaces around us. In Experiment 1, viewers assessed the three-dimensional character of projections of flat and curved surfaces receding in the distance. They made pairwise judgments of preference and of dissimilarity among eight stimuli in each of four sets. The presence of each gradient was manipulated orthogonally such that each stimulus had zero, one, two, or three gradients appropriate for either a flat surface or a curved surface. Judgments were made were made for surfaces with both regularly shaped and irregularly shaped textures scattered on them. All viewer assessment were then scaled in one dimension. Multiple correlation and regression on the scale values

  9. CARACTERIZACIÓN MOLECULAR PARCIAL DEL VIRUS DEL MOTEADO DEL CLAVEL (CarMV PRESENTE EN LA SABANA DE BOGOTÁ

    Directory of Open Access Journals (Sweden)

    Ana Yervid Rodríguez

    2000-12-01

    Full Text Available En el presente trabajo se realizó un estudio del virus moteado del clavel (CarMV, en el cual se analizaron con la prueba de ELISA muestras de clavel de diferentes variedades de la Sabana de Bogotá. Esta prueba indicó que el82% de las muestras analizadas eran positivas para el CarMV. El CarMV presente en las muestras positivas fue inoculado mecánicamente en plantas de clavel certificadas libres de virus. La partícula viral se purificó utilizando centrifugación en gradientes y colchones de sacarosa. La proteína de la cápside fue analizada por electroforesis SDS-PAGE, encontrándose una banda de proteína de masa molecular relativa aproximada de 38kDa. El tejido infectado con el CarMV se sometió a un proceso de extracción de RNA de doble cadena (dsRNA encontrándose de 3 a5 componentes electroforéticos cuyos tamaños fluctuaron aproximadamente entre 8.0 y 0.9 kpb. Este patrón de dsRNA pennitió diferenciar al menos 3 aislamientos virales. El análisis electroforético en geles de agarosa del RNA genómico de varios aislamientos virales, mostró una banda de peso molecular aproximado de 4.0 kb. El análisis del RNA genómico digerido con RNAsa TI pennitió diferenciar 2 grupos de patrones electroforéticos de los aislamientosestudiados.

  10. L’herbari de l’Institut Botànic de Barcelona com una eina per la conservació dels tàxons endèmics i amenaçats de Catalunya

    Directory of Open Access Journals (Sweden)

    Gavioli, L.

    2012-12-01

    Full Text Available The herbarium of the Botanic Institute of Barcelona (BC is the largest collection of plants of Catalonia and the second of Spain due to its volume, and it is representative of the flora of the western Mediterranean region. It includes, apart from the general collection, other historical collections (from 17th to early 20th century. The main objectives of this study were to evaluate if the endemic and threatened taxa of Catalonia are represented in the herbarium. We also provide chronological and geographical information of herborization intensity, as well as altitudinal, chorological, chronological, phenological and over-collection risk new data. We analyzed the general collection and part of informatized historical herbaria (Cadevall, Hieraciotheca Gallica et Hispanica, Institució Catalana d’Història Natural, Salvador, Societat Botànica Barcelonesa and Trèmols [volumes I-XXI]. Specimens collected from Catalonia have been found to represent 82.24% of the 304 endemic and threatened taxa. The areas with more herborization pressure were Ribes Valley, Montserrat, Port Massif, Cardó Mountains, Montseny and Montsec Mountains. The new chorological data provided expands the distribution of Berberis vulgaris L. subsp. seroi O. Bolòs & Vigo and Stachys maritima Gouan. New altitudinal and phenological data are provided for nine and 40 taxa, respectively.

    El herbario del Instituto Botánico de Barcelona (BC es la colección de plantas más importante de Cataluña y la segunda de España y es representativo de la flora de la región mediterránea occidental. Incluye la colección general y otras colecciones históricas (desde el siglo XVII hasta principios del XX. Los objetivos principales de este trabajo han sido evaluar la representatividad de los táxones endémicos y amenazados de Cataluña en el herbario así como aportar información de tipo cronológico y geográfico de intensidad de recolección y

  11. La crisi del diritto del lavoro

    Directory of Open Access Journals (Sweden)

    Alessandro Garilli

    2012-01-01

    Full Text Available Riassunto - L’Autore ripercorre in chiave critica l’evoluzione delle politiche legislative in materia di lavoro, alla luce dell’attuale fase di crisi economico finanziaria. Nell’esaminare i principali interventi normativi attuati da inizio secolo, l’Autore mette in evidenza le scelte di metodo e gli elementi di continuità che accomunano i vari provvedimenti, individuandoli nell’affannosa ricerca del punto di equilibrio tra flessibilità e garantismo. La riflessione si chiude con alcuni interrogativi sulle ultime linee di riforma del mercato del lavoro e con l’auspicio che, anche al cospetto delle imprescindibili ragioni dell’economia, il diritto del lavoro possa continuare a svolgere il proprio tradizionale ruolo di disciplina di tutela della persona.   Abstract - The author analyzes, with a critically oriented approach, the development of the employment law, in the light of the current economic and financial crisis. In examining the main regulatory measures implemented since the beginning of the century, the author highlights the methodological choices and the elements of continuity that unite the various measures, focusing them in a hard research of a point of balance between flexibility and security. The discussion concludes with some questions about the last lines of the reform of the labor market and with the hope that, even in the face of compelling reasons of economy, labor law can continue to play its traditional role of governing the protection of person.

  12. OBJETIVO DEL DESARROLLO DEL MILENIO 7

    Directory of Open Access Journals (Sweden)

    Margarita M. Pérez O.

    2013-10-01

    Full Text Available Los Objetivos de Desarrollo del Milenio, también conocidos como los Objetivos del Milenio, constituyeron las metas finales que aprobaron los dirigentes mundiales, 189 jefes de estado y de gobierno en la Cumbre del Milenio de las Naciones Unidas celebrada en Nueva York en el año 2000, en la cual los Estados miembros de la organización reafirmaron su compromiso de luchar por un mundo en el que el desarrollo sostenible y la eliminación de la pobreza tuvieran máxima prioridad1 . En la cumbre se definió la Declaración del Milenio, la cual detalla los objetivos, principios, valores, metas y acciones para erradicar la pobreza Mundial hacia el año 2015, todos ellos ratificados con alto interés y acción estratégica de carácter global, como marco para la medición de los progresos en materia de desarrollo.

  13. Elementos del sistema electoral del Congreso Mexicano

    Directory of Open Access Journals (Sweden)

    Aldo Medina García

    2013-08-01

    Full Text Available El presente artículo es un estudio de los componentes del sistema electoral, diseñado por el legislador mexicano para integrar al parlamento federal. Estudio desarrollado a sabiendas de la importancia que reviste el sistema electoral como un medio que permite a los ciudadanos convertir su voto expresado en las urnas en escaños a favor de determinado candidato o partido. En dicho análisis tomamos en cuenta la evolución constitucional del sistema electoral mexicano, la participación de las fuerzas minoritarias en la integración del Senado y de la Cámara de Diputados, la división que se hace del territorio en circunscripciones electorales, la barrera electoral que se fija a los partidos políticos para acceder a la representación en el Parlamento, la fórmula de asignación que se aplica a la votación obtenida, para finalmente concluir que el sistema electoral mexicano es esencialmente mayoritario aun cuando se vista de proporcional.

  14. Advanced compositional gradient and compartmentalization analysis

    Energy Technology Data Exchange (ETDEWEB)

    Canas, Jesus A.; Petti, Daniela; Mullins, Oliver [Schlumberger Servicos de Petroleo Ltda., Rio de Janeiro, RJ (Brazil)

    2008-07-01

    Acquisition of hydrocarbons samples from the reservoir prior to oil or gas production is essential in order to design production strategies and production facilities. In addition, reservoir compartmentalization and hydrocarbon compositional grading magnify the necessity to map fluid properties vertically and laterally in the reservoir prior to production. Formation testers supply a wealth of information to observe and predict the state of fluids in hydrocarbon reservoirs, through detailed pressure and fluid analysis measurements. With the correct understanding of the state of fluids in the reservoirs, reserve calculations and adequate development plans can be prepared. Additionally, flow barriers may then be revealed. This paper describes a new Downhole Fluid Analysis technology (DFA) for improved reservoir management. DFA is a unique process that combines new fluid identification sensors, which allow real time monitoring of a wide range of parameters as GOR, fluid density, viscosity, fluorescence and composition (CH{sub 4}, C2- C5, C6 +, CO{sub 2}), free gas and liquid phases detection, saturation pressure, as well WBM and OBM filtrate differentiation and pH. This process is not limited to light fluid evaluation and we extended to heavy oil (HO) reservoirs analysis successfully. The combination of DFA Fluid Profiling with pressure measurements has shown to be very effective for compartmentalization characterization. The ability of thin barriers to hold off large depletion pressures has been established, as the gradual variation of hydrocarbon quality in biodegraded oils. In addition, heavy oils can show large compositional variation due to variations in source rock charging but without fluid mixing. Our findings indicates that steep gradients are common in gas condensates or volatile oils, and that biodegradation is more common in HO than in other hydrocarbons, which generate fluid gradients and heavy ends tars near the OWC, limiting the aquifer activity and

  15. Composition gradients across spiral galaxies II. The stellar mass limit

    International Nuclear Information System (INIS)

    Shields, G.A.; Tinsley, B.M.

    1976-01-01

    The equivalent width of the Hβ emission from H ii regions in spiral galaxies increases with distance from the nucleus. This W (Hβ) gradient is interpreted in terms of a radial gradient in the temperature of the hottest exciting stars. (T/subu/). From Searle's observations of M101, an increase Δ log T/subu/=0.02--0.13 from the intermediate to outermost spiral arms of M101 is inferred. There is also a radial decrease in the metal abundance (Z) across M101, and the T/subu/ gradient is consistent with the prediction of Kahn's recent theory that the upper mass limit for star formation should be smaller in regions of high Z. It is noted also that, even in the absence of changes in the upper mass limit, a T/subu/ gradient is expected because metal-rich stars of given mass have smaller effective temperatures. Several observational and theoretical improvements are needed before firm conclusions can be drawn, but it is clear that the presence of a T/subu/ gradient may lead to several important systematic changes in the interpretation of gradients in the properties of H ii regions across galaxies. A T/subu/ gradient reduces the Z gradient that is inferred from emission-line ratios, and it may help to explain why O ii is strong in the innermost regions where O iii is weak. A T/subu/ gradient may also partly camouflage a helium abundance gradient

  16. B1 gradient coherence selection using a tapered stripline.

    Science.gov (United States)

    van Meerten, S G J; Tijssen, K C H; van Bentum, P J M; Kentgens, A P M

    2018-01-01

    Pulsed-field gradients are common in modern liquid state NMR pulse sequences. They are often used instead of phase cycles for the selection of coherence pathways, thereby decreasing the time required for the NMR experiment. Soft off-resonance pulses with a B 1 gradient result in a spatial encoding similar to that created by pulsed-field (B 0 ) gradients. In this manuscript we show that pulse sequences with pulsed-field gradients can easily be converted to one which uses off-resonance B 1 field gradient (OFFBEAT) pulses. The advantage of B 1 gradient pulses for coherence selection is that the chemical shift evolution during the pulses is (partially) suppressed. Therefore no refocusing echos are required to correct for evolution during the gradient pulses. A tapered stripline is shown to be a convenient tool for creating a well-defined gradient in the B 1 field strength. B 1 gradient coherence selection using a tapered stripline is a simple and cheap alternative to B 0 pulsed-field gradients. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Fano resonances from gradient-index metamaterials.

    Science.gov (United States)

    Xu, Yadong; Li, Sucheng; Hou, Bo; Chen, Huanyang

    2016-01-27

    Fano resonances - resonant scattering features with a characteristic asymmetric profile - have generated much interest, due to their extensive and valuable applications in chemical or biological sensors, new types of optical switches, lasers and nonlinear optics. They have been observed in a wide variety of resonant optical systems, including photonic crystals, metamaterials, metallic gratings and nanostructures. In this work, a waveguide structure is designed by employing gradient-index metamaterials, supporting strong Fano resonances with extremely sharp spectra. As the changes in the transmission spectrum originate from the interaction of guided modes from different channels, instead of resonance structures or metamolecules, the Fano resonances can be observed for both transverse electric and transverse magnetic polarizations. These findings are verified by fine agreement with analytical calculations and experimental results at microwave, as well as simulated results at near infrared frequencies.

  18. Ultimate-gradient accelerators physics and prospects

    CERN Document Server

    Skrinsky, Aleksander Nikolayevich

    1995-01-01

    As introduction, the needs and ways for ultimate acceleration gradients are discussed briefly. The Plasma Wake Field Acceleration is analized in the most important details. The structure of specific plasma oscillations and "high energy driver beam SP-plasma" interaction is presented, including computer simulation of the process. Some pratical ways to introduce the necessary mm-scale bunching in driver beam and to arrange sequential energy multiplication are dicussed. The influence of accelerating beam particle - plasma binary collisions is considered, also. As applications of PWFA, the use of proton super-colliders beams (LHC and Future SC) to drive the "multi particle types" accelerator, and the arrangements for the electron-positron TeV range collider are discussed.

  19. High gradient lens for charged particle beam

    Science.gov (United States)

    Chen, Yu-Jiuan

    2014-04-29

    Methods and devices enable shaping of a charged particle beam. A dynamically adjustable electric lens includes a series of alternating a series of alternating layers of insulators and conductors with a hollow center. The series of alternating layers when stacked together form a high gradient insulator (HGI) tube to allow propagation of the charged particle beam through the hollow center of the HGI tube. A plurality of transmission lines are connected to a plurality of sections of the HGI tube, and one or more voltage sources are provided to supply an adjustable voltage value to each transmission line of the plurality of transmission lines. By changing the voltage values supplied to each section of the HGI tube, any desired electric field can be established across the HGI tube. This way various functionalities including focusing, defocusing, acceleration, deceleration, intensity modulation and others can be effectuated on a time varying basis.

  20. Fractional calculus and morphogen gradient formation

    Science.gov (United States)

    Yuste, Santos Bravo; Abad, Enrique; Lindenberg, Katja

    2012-12-01

    Some microscopic models for reactive systems where the reaction kinetics is limited by subdiffusion are described by means of reaction-subdiffusion equations where fractional derivatives play a key role. In particular, we consider subdiffusive particles described by means of a Continuous Time Random Walk (CTRW) model subject to a linear (first-order) death process. The resulting fractional equation is employed to study the developmental biology key problem of morphogen gradient formation for the case in which the morphogens are subdiffusive. If the morphogen degradation rate (reactivity) is constant, we find exponentially decreasing stationary concentration profiles, which are similar to the profiles found when the morphogens diffuse normally. However, for the case in which the degradation rate decays exponentially with the distance to the morphogen source, we find that the morphogen profiles are qualitatively different from the profiles obtained when the morphogens diffuse normally.

  1. Molecular evolution and the latitudinal biodiversity gradient.

    Science.gov (United States)

    Dowle, E J; Morgan-Richards, M; Trewick, S A

    2013-06-01

    Species density is higher in the tropics (low latitude) than in temperate regions (high latitude) resulting in a latitudinal biodiversity gradient (LBG). The LBG must be generated by differential rates of speciation and/or extinction and/or immigration among regions, but the role of each of these processes is still unclear. Recent studies examining differences in rates of molecular evolution have inferred a direct link between rate of molecular evolution and rate of speciation, and postulated these as important drivers of the LBG. Here we review the molecular genetic evidence and examine the factors that might be responsible for differences in rates of molecular evolution. Critical to this is the directionality of the relationship between speciation rates and rates of molecular evolution.

  2. Accelerated gradient methods for constrained image deblurring

    International Nuclear Information System (INIS)

    Bonettini, S; Zanella, R; Zanni, L; Bertero, M

    2008-01-01

    In this paper we propose a special gradient projection method for the image deblurring problem, in the framework of the maximum likelihood approach. We present the method in a very general form and we give convergence results under standard assumptions. Then we consider the deblurring problem and the generality of the proposed algorithm allows us to add a energy conservation constraint to the maximum likelihood problem. In order to improve the convergence rate, we devise appropriate scaling strategies and steplength updating rules, especially designed for this application. The effectiveness of the method is evaluated by means of a computational study on astronomical images corrupted by Poisson noise. Comparisons with standard methods for image restoration, such as the expectation maximization algorithm, are also reported.

  3. Error analysis of stochastic gradient descent ranking.

    Science.gov (United States)

    Chen, Hong; Tang, Yi; Li, Luoqing; Yuan, Yuan; Li, Xuelong; Tang, Yuanyan

    2013-06-01

    Ranking is always an important task in machine learning and information retrieval, e.g., collaborative filtering, recommender systems, drug discovery, etc. A kernel-based stochastic gradient descent algorithm with the least squares loss is proposed for ranking in this paper. The implementation of this algorithm is simple, and an expression of the solution is derived via a sampling operator and an integral operator. An explicit convergence rate for leaning a ranking function is given in terms of the suitable choices of the step size and the regularization parameter. The analysis technique used here is capacity independent and is novel in error analysis of ranking learning. Experimental results on real-world data have shown the effectiveness of the proposed algorithm in ranking tasks, which verifies the theoretical analysis in ranking error.

  4. Simulation studies on high-gradient experiments

    International Nuclear Information System (INIS)

    Yamaguchi, S.

    1992-12-01

    Computer simulation of the characteristics of the dark current emitted from a 0.6 m long S-band accelerating structure has been made. The energy spectra and the dependence of the dark current on the structure length were simulated. By adjusting the secondary electron emission (SEE) coefficients, the simulated energy spectra qualitatively reproduced the observed ones. It was shown that the dark current increases exponentially with the structure length. The measured value of the multiplication factor of the dark current per unit cell can be explained if the SEE coefficient is set to 1.2. The critical gradient for dark current capture E cri has been calculated for two structures of 180 cells. They are E cri [MV/m] = 13.1 f and 8.75 f for a/λ = 0.089 and 0.16, respectively, where f is the frequency in GHz, a the iris diameter and λ the wave length

  5. Eigen-Gradients for Traffic Sign Recognition

    Directory of Open Access Journals (Sweden)

    Sheila Esmeralda Gonzalez-Reyna

    2013-01-01

    Full Text Available Traffic sign detection and recognition systems include a variety of applications like autonomous driving, road sign inventory, and driver support systems. Machine learning algorithms provide useful tools for traffic sign identification tasks. However, classification algorithms depend on the preprocessing stage to obtain high accuracy rates. This paper proposes a road sign characterization method based on oriented gradient maps and the Karhunen-Loeve transform in order to improve classification performance. Dimensionality reduction may be important for portable applications on resource constrained devices like FPGAs; therefore, our approach focuses on achieving a good classification accuracy by using a reduced amount of attributes compared to some state-of-the-art methods. The proposed method was tested using German Traffic Sign Recognition Benchmark, reaching a dimensionality reduction of 99.3% and a classification accuracy of 95.9% with a Multi-Layer Perceptron.

  6. Dynamic pulsed-field-gradient NMR

    CERN Document Server

    Sørland, Geir Humborstad

    2014-01-01

    Dealing with the basics, theory and applications of dynamic pulsed-field-gradient NMR NMR (PFG NMR), this book describes the essential theory behind diffusion in heterogeneous media that can be combined with NMR measurements to extract important information of the system being investigated. This information could be the surface to volume ratio, droplet size distribution in emulsions, brine profiles, fat content in food stuff, permeability/connectivity in porous materials and medical applications currently being developed. Besides theory and applications it will provide the readers with background knowledge on the experimental set-ups, and most important, deal with the pitfalls that are numerously present in work with PFG-NMR. How to analyze the NMR data and some important basic knowledge on the hardware will be explained, too.

  7. Magnon dark modes and gradient memory.

    Science.gov (United States)

    Zhang, Xufeng; Zou, Chang-Ling; Zhu, Na; Marquardt, Florian; Jiang, Liang; Tang, Hong X

    2015-11-16

    Extensive efforts have been expended in developing hybrid quantum systems to overcome the short coherence time of superconducting circuits by introducing the naturally long-lived spin degree of freedom. Among all the possible materials, single-crystal yttrium iron garnet has shown up recently as a promising candidate for hybrid systems, and various highly coherent interactions, including strong and even ultrastrong coupling, have been demonstrated. One distinct advantage in these systems is that spins form well-defined magnon modes, which allows flexible and precise tuning. Here we demonstrate that by dissipation engineering, a non-Markovian interaction dynamics between the magnon and the microwave cavity photon can be achieved. Such a process enables us to build a magnon gradient memory to store information in the magnon dark modes, which decouple from the microwave cavity and thus preserve a long lifetime. Our findings provide a promising approach for developing long-lifetime, multimode quantum memories.

  8. A fast, preconditioned conjugate gradient Toeplitz solver

    Science.gov (United States)

    Pan, Victor; Schrieber, Robert

    1989-01-01

    A simple factorization is given of an arbitrary hermitian, positive definite matrix in which the factors are well-conditioned, hermitian, and positive definite. In fact, given knowledge of the extreme eigenvalues of the original matrix A, an optimal improvement can be achieved, making the condition numbers of each of the two factors equal to the square root of the condition number of A. This technique is to applied to the solution of hermitian, positive definite Toeplitz systems. Large linear systems with hermitian, positive definite Toeplitz matrices arise in some signal processing applications. A stable fast algorithm is given for solving these systems that is based on the preconditioned conjugate gradient method. The algorithm exploits Toeplitz structure to reduce the cost of an iteration to O(n log n) by applying the fast Fourier Transform to compute matrix-vector products. Matrix factorization is used as a preconditioner.

  9. Formulating viscous hydrodynamics for large velocity gradients

    International Nuclear Information System (INIS)

    Pratt, Scott

    2008-01-01

    Viscous corrections to relativistic hydrodynamics, which are usually formulated for small velocity gradients, have recently been extended from Navier-Stokes formulations to a class of treatments based on Israel-Stewart equations. Israel-Stewart treatments, which treat the spatial components of the stress-energy tensor τ ij as dynamical objects, introduce new parameters, such as the relaxation times describing nonequilibrium behavior of the elements τ ij . By considering linear response theory and entropy constraints, we show how the additional parameters are related to fluctuations of τ ij . Furthermore, the Israel-Stewart parameters are analyzed for their ability to provide stable and physical solutions for sound waves. Finally, it is shown how these parameters, which are naturally described by correlation functions in real time, might be constrained by lattice calculations, which are based on path-integral formulations in imaginary time

  10. Gradient Measurements of Nitrous Acid (hono)

    Science.gov (United States)

    Kleffmann, J.; Kurtenbach, R.; Lörzer, J.; Wiesen, P.; Kalthoff, N.; Vogel, B.; Vogel, H.

    Nitrous acid (HONO) plays an important role in photochemical air pollution due to its photodissociation by solar UV radiation into hydroxyl radicals and thus significantly enhances photooxidation processes. Furthermore, HONO is an important indoor pol- lutant, which can react with amines leading to nitrosamines, which are known to be carcinogenic. Despite its importance in atmospheric chemistry the mechanisms lead- ing to HONO formation are still not completely understood at present. Although it is commonly proposed that HONO is formed by heterogeneous processes, i.e. by the conversion of NO2 on wet surfaces, it is still under discussion whether HONO produc- tion is dominated by the surface of particles or by the ground surface. Simultaneous vertical profile measurements of HONO, the precursor NO2 and the aerosol surface area, which could answer this question are not available at present. Accordingly, in the present study night-time HONO, NO2 and particle surface area gradients in the altitude range 10-190 m were measured on the meteorological tower at the Forschungszentrum Karlsruhe/Germany using a new, very sensitive HONO in- strument (LOPAP), a commercial NOx monitor and a SMPS system. For all gradient measurements during the campaign it was observed that the [HONO]/[NO2] ratio decreased with increasing altitude. In contrast, the particle sur- face area was found to be more or less constant. Accordingly, no correlation between the [HONO]/[NO2] ratio and the particle surface area was observed showing that HONO formation was dominated by processes on ground surfaces and that signifi- cant HONO formation on particle surfaces could be excluded for the measurement site.

  11. High-gradient compact linear accelerator

    Science.gov (United States)

    Carder, Bruce M.

    1998-01-01

    A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter.

  12. Castillo del Real. Olocau

    OpenAIRE

    AUÑÓN VALLEJO, JONATAN

    2012-01-01

    El objetivo que se quiere alcanzar con este proyecto es el de realizar un estudio lo más cercano posible del Catillo del Real, de manera que se pueda conocer su origen, su evolución a lo largo de la historia, así como las diferentes técnicas y sistemas constructivos utilizados en su construcción. Auñón Vallejo, J. (2011). Castillo del Real. Olocau. http://hdl.handle.net/10251/14244. Archivo delegado

  13. La Representabilidad del Genocidio

    OpenAIRE

    Cardona González, Lorena

    2012-01-01

    El presente artículo intenta hacer una aproximación histórica y analítica al fenómeno del Genocidio, sus implicaciones sociales y culturales que dieron como resultado la reformulación analítica y conceptual de hechos que hasta entonces superaban el conocimiento y la moral humana. De este modo, se hace un trayecto histórico de la paulatina aparición del asesinato masivo como practica de Estado, enmarcado en las experiencias del genocidio armenio y el alemán. A su vez, se hace una mirada sobre ...

  14. Significado presente del CSIC

    OpenAIRE

    Garrido Gallardo, Miguel Angel

    2000-01-01

    Not available

    Este artículo, elaborado en 1999, ofrece una panorámica de la realidad del Consejo Superior de Investigaciones Científicas en la actualidad. Repasa su organización, su volumen de publicaciones, sus indicadores de productividad, su capacidad de obtener recursos y, en suma, su lugar en el conjunto del sistema español de Ciencia y Tecnología, considerado en sí mismo y en relación con la Universidad. Como conclusión del repaso de datos, se afirma que, aunque la fó...

  15. Tratamiento del pie equino

    OpenAIRE

    Robles, Fernanda

    2012-01-01

    El pie equino varo es una patología frecuente en los pacientes con Encefalopatía crónica no evolutiva (ECNE).Se observó que existe una mayor frecuencia en el sexo masculino. Se realizó un estudio descriptivo, comparativo y secundario, durante el periodo de septiembre del 2006 a septiembre del 2011, con un total de 125 pacientes con Ecne, de los cuales se encontraron 101 con pie equino varo congénito. Objetivo: observar los resultados obtenidos en la rehabilitación del pie equino, en niños de ...

  16. Del Pasadismo al Futurismo

    OpenAIRE

    Agudo-Martínez, M. J.

    2003-01-01

    Uno de los habituales prejuicios a la hora de abordar el análisis del movimiento futurista, al igual que sucede con el constructivismo, es la consideración del contexto político en el que se desarrollaron ambas vanguardias. Sin embargo, y dejando a un lado un enfoque del arte con finalidad política de signo diverso, habría que insistir en el hecho de que posiblemente sean tanto el futurismo italiano como el constructivismo ruso, los movimientos que con mayor entusiasmo se manifestaron, en un ...

  17. Self-induced temperature gradients in Brownian dynamics

    Science.gov (United States)

    Devine, Jack; Jack, M. W.

    2017-12-01

    Brownian systems often surmount energy barriers by absorbing and emitting heat to and from their local environment. Usually, the temperature gradients created by this heat exchange are assumed to dissipate instantaneously. Here we relax this assumption to consider the case where Brownian dynamics on a time-independent potential can lead to self-induced temperature gradients. In the same way that externally imposed temperature gradients can cause directed motion, these self-induced gradients affect the dynamics of the Brownian system. The result is a coupling between the local environment and the Brownian subsystem. We explore the resulting dynamics and thermodynamics of these coupled systems and develop a robust method for numerical simulation. In particular, by focusing on one-dimensional situations, we show that self-induced temperature gradients reduce barrier-crossing rates. We also consider a heat engine and a heat pump based on temperature gradients induced by a Brownian system in a nonequilibrium potential.

  18. Modified conjugate gradient method for diagonalizing large matrices.

    Science.gov (United States)

    Jie, Quanlin; Liu, Dunhuan

    2003-11-01

    We present an iterative method to diagonalize large matrices. The basic idea is the same as the conjugate gradient (CG) method, i.e, minimizing the Rayleigh quotient via its gradient and avoiding reintroducing errors to the directions of previous gradients. Each iteration step is to find lowest eigenvector of the matrix in a subspace spanned by the current trial vector and the corresponding gradient of the Rayleigh quotient, as well as some previous trial vectors. The gradient, together with the previous trial vectors, play a similar role as the conjugate gradient of the original CG algorithm. Our numeric tests indicate that this method converges significantly faster than the original CG method. And the computational cost of one iteration step is about the same as the original CG method. It is suitable for first principle calculations.

  19. COMPARISON OF GKS CALCULATED CRITICAL ION TEMPERATURE GRADIENTS AND ITG GROWTH RATES TO DIII-D MEASURED GRADIENTS AND DIFFUSIVITIES

    International Nuclear Information System (INIS)

    BAKER, DR; STAEBLER, GM; PETTY, CC; GREENFIELD, CM; LUCE, TC

    2003-01-01

    OAK-B135 The gyrokinetic equations predict that various drift type waves or modes can be unstable in a tokamak. For some of these modes, such as the ion temperature gradient (ITG) mode and the electron temperature gradient mode, there exists a critical gradient, above which the mode is unstable. Since the existence of unstable modes can cause increased transport, plasmas which are centrally heated tend to increase in temperature gradient until the modes become unstable. Under some conditions the increased transport can fix the gradient at the critical value. here they present a comparison between the measured ion temperature gradients and the critical gradient as calculated by a gyrokinetic linear stability (GKS) code. They also present the maximum linear growth rate as calculated by this code for comparison to experimentally derived transport coefficients. The results show that for low confinement mode (L-mode) discharges, the measured ion temperature gradient is significantly greater than the GKS calculated critical gradient over a large region of the plasma. This is the same region of the plasma where the ion thermal diffusivity is large. For high confinement mode (H-mode) discharges the ion temperature gradient is closer to the critical gradient, but often still greater than the critical gradient over some region. For the best H-mode discharges, the ion temperature is less than or equal to the critical gradient over the whole plasma. In general they find that the position in the plasma where the ion thermal diffusivity starts to increase rapidly is where the maximum linear growth rate is greater than the E x B shearing rate

  20. Gradient porous hydroxyapatite ceramics fabricated by freeze casting method

    International Nuclear Information System (INIS)

    Zuo Kaihui; Zhang Yuan; Jiang Dongliang; Zeng Yuping

    2011-01-01

    By controlling the cooling rates and the composition of slurries, the gradient porous hydroxyapatite ceramics are fabricated by the freeze casting method. According to the different cooling rate, the pores of HAP ceramics fabricated by gradient freeze casting are divided into three parts: one is lamellar pores, another is column pore and the last one is fine round pores. The laminated freeze casting is in favour of obtaining the gradient porous ceramics composed of different materials and the ceramics have unclear interfaces.