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Sample records for guariba clamitans cabrera

  1. Parturition and potential infanticide in free-ranging Alouatta guariba clamitans.

    PubMed

    Martins, Valeska; Chaves, Óscar M; Neves, Mariana Beal; Bicca-Marques, Júlio César

    2015-04-01

    Parturition is a key process of mammalian reproduction that is rarely documented in New World monkeys because it often occurs at night. However, diurnal births have been recorded in several species. In howler monkeys (Alouatta spp.) they have often been observed during prolonged resting periods. Similarly, infanticide is a behavior observed quite infrequently. Infanticide in howler monkeys is often inferred from infant deaths or disappearances after group takeovers by nonresident male(s). Here we report the first observation of parturition and birth-related behaviors in the brown howler monkey (Alouatta guariba clamitans) and the likely attack on the infant that caused its death. The mother was a multiparous female that lived in a ca. 3-ha Atlantic forest fragment in southern Brazil with nine group mates. The behavior ("all occurrences") sampling method was used to record birth-related behaviors and social interactions. The parturition occurred during the day of 27 October 2013 during a feeding session. The female showed no sign of contraction or birth delivery posture. Parturition began apparently after matrix rupture and release of the amniotic fluid. Expulsion of the newborn occurred between 1 and 3 min later (the exact moment of delivery was not observed). Then, the female held and licked the newborn and began to ingest the placenta and the umbilical cord. The other group members continued feeding and had no interaction with the parturient during the preparturition and parturition events. The infant died ca. 35 days later as a consequence of injuries to his forehead and face, potentially caused by a conspecific bite. Because the adult and subadult males chased the female in the day that the infant's wounds were detected, we believe that one of them might have been the aggressor. We discuss this putative case of infanticide in light of the potential motivation of each male.

  2. Parturition and potential infanticide in free-ranging Alouatta guariba clamitans.

    PubMed

    Martins, Valeska; Chaves, Óscar M; Neves, Mariana Beal; Bicca-Marques, Júlio César

    2015-04-01

    Parturition is a key process of mammalian reproduction that is rarely documented in New World monkeys because it often occurs at night. However, diurnal births have been recorded in several species. In howler monkeys (Alouatta spp.) they have often been observed during prolonged resting periods. Similarly, infanticide is a behavior observed quite infrequently. Infanticide in howler monkeys is often inferred from infant deaths or disappearances after group takeovers by nonresident male(s). Here we report the first observation of parturition and birth-related behaviors in the brown howler monkey (Alouatta guariba clamitans) and the likely attack on the infant that caused its death. The mother was a multiparous female that lived in a ca. 3-ha Atlantic forest fragment in southern Brazil with nine group mates. The behavior ("all occurrences") sampling method was used to record birth-related behaviors and social interactions. The parturition occurred during the day of 27 October 2013 during a feeding session. The female showed no sign of contraction or birth delivery posture. Parturition began apparently after matrix rupture and release of the amniotic fluid. Expulsion of the newborn occurred between 1 and 3 min later (the exact moment of delivery was not observed). Then, the female held and licked the newborn and began to ingest the placenta and the umbilical cord. The other group members continued feeding and had no interaction with the parturient during the preparturition and parturition events. The infant died ca. 35 days later as a consequence of injuries to his forehead and face, potentially caused by a conspecific bite. Because the adult and subadult males chased the female in the day that the infant's wounds were detected, we believe that one of them might have been the aggressor. We discuss this putative case of infanticide in light of the potential motivation of each male. PMID:25739583

  3. Yellow fever impact on brown howler monkeys (Alouatta guariba clamitans) in Argentina: a metamodelling approach based on population viability analysis and epidemiological dynamics

    PubMed Central

    Moreno, Eduardo S; Agostini, Ilaria; Holzmann, Ingrid; Di Bitetti, Mario S; Oklander, Luciana I; Kowalewski, Martín M; Beldomenico, Pablo M; Goenaga, Silvina; Martínez, Mariela; Lestani, Eduardo; Desbiez, Arnaud LJ; Miller, Philip

    2015-01-01

    In South America, yellow fever (YF) is an established infectious disease that has been identified outside of its traditional endemic areas, affecting human and nonhuman primate (NHP) populations. In the epidemics that occurred in Argentina between 2007-2009, several outbreaks affecting humans and howler monkeys (Alouatta spp) were reported, highlighting the importance of this disease in the context of conservation medicine and public health policies. Considering the lack of information about YF dynamics in New World NHP, our main goal was to apply modelling tools to better understand YF transmission dynamics among endangered brown howler monkey (Alouatta guariba clamitans) populations in northeastern Argentina. Two complementary modelling tools were used to evaluate brown howler population dynamics in the presence of the disease: Vortex, a stochastic demographic simulation model, and Outbreak, a stochastic disease epidemiology simulation. The baseline model of YF disease epidemiology predicted a very high probability of population decline over the next 100 years. We believe the modelling approach discussed here is a reasonable description of the disease and its effects on the howler monkey population and can be useful to support evidence-based decision-making to guide actions at a regional level. PMID:26517499

  4. Yellow fever impact on brown howler monkeys (Alouatta guariba clamitans) in Argentina: a metamodelling approach based on population viability analysis and epidemiological dynamics.

    PubMed

    Moreno, Eduardo S; Agostini, Ilaria; Holzmann, Ingrid; Di Bitetti, Mario S; Oklander, Luciana I; Kowalewski, Martín M; Beldomenico, Pablo M; Goenaga, Silvina; Martínez, Mariela; Lestani, Eduardo; Desbiez, Arnaud L J; Miller, Philip

    2015-11-01

    In South America, yellow fever (YF) is an established infectious disease that has been identified outside of its traditional endemic areas, affecting human and nonhuman primate (NHP) populations. In the epidemics that occurred in Argentina between 2007-2009, several outbreaks affecting humans and howler monkeys (Alouatta spp) were reported, highlighting the importance of this disease in the context of conservation medicine and public health policies. Considering the lack of information about YF dynamics in New World NHP, our main goal was to apply modelling tools to better understand YF transmission dynamics among endangered brown howler monkey (Alouatta guariba clamitans) populations in northeastern Argentina. Two complementary modelling tools were used to evaluate brown howler population dynamics in the presence of the disease: Vortex, a stochastic demographic simulation model, and Outbreak, a stochastic disease epidemiology simulation. The baseline model of YF disease epidemiology predicted a very high probability of population decline over the next 100 years. We believe the modelling approach discussed here is a reasonable description of the disease and its effects on the howler monkey population and can be useful to support evidence-based decision-making to guide actions at a regional level.

  5. Yellow fever impact on brown howler monkeys (Alouatta guariba clamitans) in Argentina: a metamodelling approach based on population viability analysis and epidemiological dynamics.

    PubMed

    Moreno, Eduardo S; Agostini, Ilaria; Holzmann, Ingrid; Di Bitetti, Mario S; Oklander, Luciana I; Kowalewski, Martín M; Beldomenico, Pablo M; Goenaga, Silvina; Martínez, Mariela; Lestani, Eduardo; Desbiez, Arnaud L J; Miller, Philip

    2015-11-01

    In South America, yellow fever (YF) is an established infectious disease that has been identified outside of its traditional endemic areas, affecting human and nonhuman primate (NHP) populations. In the epidemics that occurred in Argentina between 2007-2009, several outbreaks affecting humans and howler monkeys (Alouatta spp) were reported, highlighting the importance of this disease in the context of conservation medicine and public health policies. Considering the lack of information about YF dynamics in New World NHP, our main goal was to apply modelling tools to better understand YF transmission dynamics among endangered brown howler monkey (Alouatta guariba clamitans) populations in northeastern Argentina. Two complementary modelling tools were used to evaluate brown howler population dynamics in the presence of the disease: Vortex, a stochastic demographic simulation model, and Outbreak, a stochastic disease epidemiology simulation. The baseline model of YF disease epidemiology predicted a very high probability of population decline over the next 100 years. We believe the modelling approach discussed here is a reasonable description of the disease and its effects on the howler monkey population and can be useful to support evidence-based decision-making to guide actions at a regional level. PMID:26517499

  6. First New World Primate Papillomavirus Identification in the Atlantic Forest, Brazil: Alouatta guariba papillomavirus 1.

    PubMed

    Silvestre, Rodrigo Vellasco Duarte; de Souza, Alex Junior Souza; Júnior, Edivaldo Costa Sousa; Silva, Allan Kaio; de Mello, Wyller Alencar; Nunes, Marcio Roberto T; Júnior, João Lídio S G V; Cardoso, Jedson Ferreira; de Vasconcelos, Janaina Mota; de Oliveira, Layanna Freitas; da Silva, Sandro Patroca; da Silva, Adriana Marques J; Fries, Brigida Gomes; Summa, Maria Eugênia L; de Sá, Lilian Rose M

    2016-01-01

    We report here the complete genome sequence of the first papillomavirus detected in a New World primate, howler monkey, Alouatta guariba clamitans papillomavirus 1 (AgPV1), from the Atlantic Forest in São Paulo State, Brazil.

  7. First New World Primate Papillomavirus Identification in the Atlantic Forest, Brazil: Alouatta guariba papillomavirus 1.

    PubMed

    Silvestre, Rodrigo Vellasco Duarte; de Souza, Alex Junior Souza; Júnior, Edivaldo Costa Sousa; Silva, Allan Kaio; de Mello, Wyller Alencar; Nunes, Marcio Roberto T; Júnior, João Lídio S G V; Cardoso, Jedson Ferreira; de Vasconcelos, Janaina Mota; de Oliveira, Layanna Freitas; da Silva, Sandro Patroca; da Silva, Adriana Marques J; Fries, Brigida Gomes; Summa, Maria Eugênia L; de Sá, Lilian Rose M

    2016-01-01

    We report here the complete genome sequence of the first papillomavirus detected in a New World primate, howler monkey, Alouatta guariba clamitans papillomavirus 1 (AgPV1), from the Atlantic Forest in São Paulo State, Brazil. PMID:27540053

  8. First New World Primate Papillomavirus Identification in the Atlantic Forest, Brazil: Alouatta guariba papillomavirus 1

    PubMed Central

    Silvestre, Rodrigo Vellasco Duarte; de Souza, Alex Junior Souza; Silva, Allan Kaio; de Mello, Wyller Alencar; Nunes, Marcio Roberto T.; Júnior, João Lídio S. G. V.; Cardoso, Jedson Ferreira; de Vasconcelos, Janaina Mota; de Oliveira, Layanna Freitas; da Silva, Sandro Patroca; da Silva, Adriana Marques J.; Fries, Brigida Gomes; Summa, Maria Eugênia L.; de Sá, Lilian Rose M.

    2016-01-01

    We report here the complete genome sequence of the first papillomavirus detected in a New World primate, howler monkey, Alouatta guariba clamitans papillomavirus 1 (AgPV1), from the Atlantic Forest in São Paulo State, Brazil. PMID:27540053

  9. Two cases of polydactyly in wild brown howler monkeys (Alouatta guariba clamitans).

    PubMed

    da Silva, Moira Ansolch; Steinberg, Eliana R; Paskulin, Giorgio A; Teixeira, Fábio dos Santos; Jesus, Anamélia de Souza; Mudry, Marta D; Bicca-Marques, Júlio César

    2016-02-01

    We report the first two cases of polydactyly in an atelid species: (i) a wild ca. 16-week-old infant female presenting seven digits in both feet and other bone malformations and (ii) a wild newborn male presenting six digits in both feet with the extra digit fused to the hallux.

  10. Cabrera-Mott kinetics of oxidation of metal nanowires

    NASA Astrophysics Data System (ADS)

    Zhdanov, Vladimir P.; Kasemo, Bengt

    2012-06-01

    The Cabrera-Mott model, implying that oxidation of a metal is limited by the field-facilitated activated jumps of metal ions at the metal-oxide interface, was originally proposed to interpret growth of thin oxide films on planar metal surfaces. Recently, the model was used to describe oxidation of spherical nanoparticles with small radius of curvature. Here, we analyze oxidation of nanowires. The increase of the oxide thickness with increasing time for a nanowire is shown to be slower than that for a nanoparticle with the same radius, but faster than in the case of a planar surface.

  11. The role of scent-marking in patchy and highly fragmented populations of the Cabrera vole (Microtus cabrerae Thomas, 1906).

    PubMed

    Gomes, Luis Alexandre Piteira; Mira, António Paulo Pereira; Barata, Eduardo Nuno

    2013-04-01

    Rodent scent-marking is often used for territorial defence and self-advertisement, and both functions often entail the continuous scent-marking of a large area with high costs. In species with highly-fragmented populations and low density, in which the likelihood of social encounters is low, the costs of continuous scent-marking might exceed the associated fitness benefits; therefore, less intensive scent-marking only to signal presence to the opposite sex may be used. This hypothesis was tested in captivity with the Cabrera vole, a species with highly fragmented and low-density populations. Firstly, to assess the unknown scent-marking behaviour of the Cabrera voles, we conducted an assay wherein voles could scent-mark a clean substrate. Both sexes marked with urine and faeces, but never with anogenital secretions, and the amount of scent-marks was not different between sexes. In the subsequent assay, voles of each sex were given the choice of scent-mark on clean substrates or on substrates previously scent-marked by males or females. Both sexes marked with urine a larger area on substrates pre-marked by the opposite sex than on substrates pre-marked by the same-sex and clean substrates; however, no differences were found in the frequency of fecal boli deposited on the three types of substrate, and no anogenital secretions were found. The clear preference of receivers to scent-mark with urine the substrate pre-marked by the opposite sex strongly suggests that Cabrera voles use urine scent-marking for inter-sexual communication, probably to increase mate-finding likelihood, rather than for territorial defense and/or self-advertisement.

  12. Intraspecific variation in the energetics of the Cabrera vole.

    PubMed

    Castellanos-Frías, Elena; García-Perea, Rosa; Gisbert, Julio; Bozinovic, Francisco; Virgós, Emilio

    2015-12-01

    Basal metabolic rate (BMR) is an intensively topic studied in ecophysiology for the purpose of understanding energy budgets of the species, variations of energy expenditure during their diary activities and physiological acclimatization to the environment. Establishing how the metabolism is assembled to the environment can provide valuable data to improve conservation strategies of endangered species. In this sense, metabolic differences associated to habitats have been widely reported in the interspecific level, however little is known about the intraspecific view of BMR under an environmental gradient. In this study, we researched the effect of the habitat on metabolic rate of an Iberian endemic species: Iberomys cabrerae. Animals were captured in different subpopulations of its altitudinal range and their MR was studied over a thermal gradient. MR was analyzed through a Linear Mixed Model (LMM) in which, in addition to thermal effects, the bioclimatic zone and sex also influenced the metabolism of the species. The beginning of thermoneutrality zone was set on 26.5°C and RMR was 2.3ml O2g(-1)h(-1), intermediate between both bioclimatic zones. Supramediterranean subpopulations started the Tlc earlier (24.9°C) and had higher RMR than the mesomediterranean ones (26.9°C). The thermal environment together with primary productivity conditions could explain this difference in the metabolic behaviour of the Cabrera voles. PMID:26319046

  13. Intraspecific variation in the energetics of the Cabrera vole.

    PubMed

    Castellanos-Frías, Elena; García-Perea, Rosa; Gisbert, Julio; Bozinovic, Francisco; Virgós, Emilio

    2015-12-01

    Basal metabolic rate (BMR) is an intensively topic studied in ecophysiology for the purpose of understanding energy budgets of the species, variations of energy expenditure during their diary activities and physiological acclimatization to the environment. Establishing how the metabolism is assembled to the environment can provide valuable data to improve conservation strategies of endangered species. In this sense, metabolic differences associated to habitats have been widely reported in the interspecific level, however little is known about the intraspecific view of BMR under an environmental gradient. In this study, we researched the effect of the habitat on metabolic rate of an Iberian endemic species: Iberomys cabrerae. Animals were captured in different subpopulations of its altitudinal range and their MR was studied over a thermal gradient. MR was analyzed through a Linear Mixed Model (LMM) in which, in addition to thermal effects, the bioclimatic zone and sex also influenced the metabolism of the species. The beginning of thermoneutrality zone was set on 26.5°C and RMR was 2.3ml O2g(-1)h(-1), intermediate between both bioclimatic zones. Supramediterranean subpopulations started the Tlc earlier (24.9°C) and had higher RMR than the mesomediterranean ones (26.9°C). The thermal environment together with primary productivity conditions could explain this difference in the metabolic behaviour of the Cabrera voles.

  14. Detection of Plasmodium in faeces of the New World primate Alouatta clamitans

    PubMed Central

    de Assis, Gabriela Maíra Pereira; de Alvarenga, Denise Anete Madureira; Costa, Daniela Camargos; de Souza, Júlio César; Hirano, Zelinda Maria Braga; Kano, Flora Satiko; de Sousa, Taís Nóbrega; de Brito, Cristiana Ferreira Alves

    2016-01-01

    Abstract Plasmodium falciparum and Plasmodium vivax have evolved with host switches between non-human primates (NHPs) and humans. Studies on the infection dynamics of Plasmodium species in NHPs will improve our understanding of the evolution of these parasites; however, such studies are hampered by the difficulty of handling animals in the field. The aim of this study was to detect genomic DNA of Plasmodium species from the faeces of New World monkeys. Faecal samples from 23 Alouatta clamitans from the Centre for Biological Research of Indaial (Santa Catarina, Brazil) were collected. Extracted DNA from faecal samples was used for molecular diagnosis of malaria by nested polymerase chain reaction. One natural infection with Plasmodium simium was identified by amplification of DNA extracted from the faeces of A. clamitans. Extracted DNA from a captive NHP was also used for parasite genotyping. The detection limit of the technique was evaluated in vitro using an artificial mixture of cultured P. falciparum in NHP faeces and determined to be 6.5 parasites/µL. Faecal samples of New World primates can be used to detect malaria infections in field surveys and also to monitor the genetic variability of parasites and dynamics of infection. PMID:27580347

  15. Effects of atrazine on metamorphosis, growth, and gonadal development in the green frog (Rana clamitans).

    PubMed

    Coady, Katherine; Murphy, Margaret; Villeneuve, Daniel; Hecker, Markus; Jones, Paul; Carr, James; Solomon, Keith; Smith, Ernest; Van Der Kraak, Glen; Kendall, Ronald; Giesy, John

    2004-06-25

    Embryos of the green frog (Rana clamitans) were collected from the field and exposed to 1 of 6 water-borne treatments for 273 d (mid July 2001 to mid April 2002). The treatments were 0, 10, or 25 microg/L atrazine, 0.005% ethanol (EtOH), or 0.1 mg/L estradiol or dihydrotestosterone carried in 0.005% EtOH. Treatments were applied in a static renewal system with a 50% test solution replacement approximately every 3 d. Following the exposure period, tadpoles were reared in freshwater until metamorphosis or until study termination (at d 506). Time to initiate and complete metamorphosis, stage-specific mortality, length and weight at metamorphosis, and gross morphology and histology of the gonads were examined. At environmentally relevant concentrations, atrazine did not consistently affect growth or metamorphosis. Compared to controls, the length of the larval period was greater in tadpoles exposed to 10 microg/L atrazine. However, the length of the larval period was not markedly different between tadpoles in the control and 25 microg/L atrazine treatments. Neither gross gonadal morphology nor histopathology of the gonads in postmetamorphic frogs was significantly altered in response to atrazine exposure. This study provides evidence that environmentally relevant concentrations of atrazine do not adversely affect the growth or reproductive development of R. clamitans.

  16. Characterization of gene expression endpoints during postembryonic development of the northern green frog (Rana clamitans melanota).

    PubMed

    Hammond, S Austin; Veldhoen, Nik; Kobylarz, Marek; Webber, Nicholas R; Jordan, Jameson; Rehaume, Vicki; Boone, Michelle D; Helbing, Caren C

    2013-05-01

    Postembryonic development of a larval tadpole into a juvenile frog involves the coordinated action of thyroid hormone (TH) across a diversity of tissues. Changes in the frog transcriptome represent a highly sensitive endpoint in the detection of developmental progression, and for the identification of environmental chemical contaminants that possess endocrine disruptive properties. Unfortunately, in contrast with their vital role as sentinels of environmental change, few gene expression tools currently exist for the majority of native North American frog species. We have isolated seven expressed gene sequences from the Northern green frog (Rana clamitans melanota) that encode proteins associated with TH-mediated postembryonic development and global stress response, and established a quantitative real-time polymerase chain reaction (qPCR) assay. We also obtained three additional species-specific gene sequences that functioned in the normalization of the expression data. Alterations in mRNA abundance profiles were identified in up to eight tissues during R. clamitans postembryonic development, and following exogenous administration of TH to premetamorphic tadpoles. Our results characterize tissue distribution and sensitivity to TH of select mRNA of a common North American frog species and support the potential use of this qPCR assay in identification of the presence of chemical agents in aquatic environments that modulate TH action. PMID:23647014

  17. Implications of Using the Cabrera Sequence for Diagnosing Acute Coronary Syndrome.

    PubMed

    Kosuge, Masami; Kimura, Kazuo

    2016-04-25

    The 12-lead electrocardiogram (ECG) is the important, initial examination for diagnosing acute coronary syndrome (ACS). In the traditional 12-lead ECG display, the precordial leads are displayed in their anatomically contiguous order, which makes it easy to understand the positional relationships between the precordial leads and the heart, but the limb leads are not. The "Cabrera sequence" displays the limb leads in an anatomically contiguous manner, which facilitates understanding of the positional relations between the limb leads and the heart, resulting in more rapid, easy, and accurate ECG interpretation than the traditional limb leads display. This review explores the clinical advantages of the Cabrera sequence as compared with the traditional limb leads display for the diagnosis of ACS. (Circ J 2016; 80: 1087-1096).

  18. Growth and development of larval green frogs (Rana clamitans) exposed to multiple doses of an insecticide

    USGS Publications Warehouse

    Boone, M.D.; Bridges, C.M.; Rothermel, B.B.

    2001-01-01

    Our objective was to determine how green frogs (Rana clamitans) are affected by multiple exposures to a sublethal level of the carbamate insecticide, carbaryl, in outdoor ponds. Tadpoles were added to 1,000-1 ponds at a low or high density which were exposed to carbaryl 0, 1, 2, or 3 times. Length of the larval period, mass, developmental stage, tadpole survival, and proportion metamorphosed were used to determine treatment effects. The frequency of dosing affected the proportion of green frogs that reached metamorphosis and the developmental stage of tadpoles. Generally, exposure to carbaryl increased rates of metamorphosis and development. The effect of the frequency of carbaryl exposure on development varied with the density treatment; the majority of metamorphs and the most developed tadpoles came from high-density ponds exposed to carbaryl 3 times. This interaction suggests that exposure to carbaryl later in the larval period stimulated metamorphosis, directly or indirectly, under high-density conditions. Our study indicates that exposure to a contaminant can lead to early initiation of metamorphosis and that natural biotic factors can mediate the effects of a contaminant in the environment.

  19. Effects of carbaryl on green frog (Rana clamitans) tadpoles: Timing of exposure versus multiple exposures

    USGS Publications Warehouse

    Boone, M.D.; Bridges, C.M.

    2003-01-01

    The majority of studies on pesticide impacts have evaluated the effects of single exposures. However, multiple exposures to a pesticide may be more prevalent. The objective of our study was to determine how multiple exposures versus single exposure at different times during development affected survival to metamorphosis, tadpole survival, tadpole mass, and tadpole developmental stage of green frog (Rana clamitans) tadpoles reared at low and high density in outdoor cattle tank ponds. Tadpoles were exposed to carbaryl zero, one, two, or three times at 14-d intervals. We applied single doses of carbaryl at one of three times, specifically during early, mid, or late development. Overall, we found that multiple exposures had a greater impact than single exposures during development. More individuals reached metamorphosis in ponds exposed to multiple doses of carbaryl compared with controls, indicating that the presence of carbaryl stimulated metamorphosis. The presence of carbaryl in the aquatic environment also resulted in more developed tadpoles compared with controls. Tadpoles in control ponds did not reach metamorphosis and were less developed than individuals exposed to carbaryl; this effect indicates that, under ideal conditions, green frogs could overwinter in ponds so that greater size could be attained before metamorphosis in the following spring or summer. Our study demonstrated the importance of including realistic application procedures when evaluating the effects of a pesticide and that multiple exposures to a short-lived pesticide are more likely to affect an amphibian population.

  20. Multiple sublethal chemicals negatively affect tadpoles of the green frog, Rana clamitans

    USGS Publications Warehouse

    Boone, Michelle D.; Bridges, Christine M.; Fairchild, James F.; Little, Edward E.

    2005-01-01

    Many habitats may be exposed to multiple chemical contaminants, particularly in agricultural areas where fertilizer and pesticide use are common; however, the singular and interactive effects of contaminants are not well understood. The objective of our study was to examine how realistic, sublethal environmental levels of ammonium nitrate fertilizer (0, 10, 20 mg/L and ammonium chloride control) and the common insecticide carbaryl (0 or 2.5 mg/L) individually and interactively affect the development, size, and survival of green frog (Rana clamitans) tadpoles. We reared tadpoles for 95 d in outdoor 1,000-L polyethylene ponds. We found that the combination of carbaryl and nitrate had a negative effect on development and mass of tadpoles compared to the positive effect that either contaminant had alone. Presence of carbaryl was generally associated with short-term increases in algal resources, including ponds exposed to both carbaryl and nitrate. However, with exposure to nitrate and carbaryl, tadpole mass and development were not positively affected as with one chemical stressor alone. The combination of these sublethal contaminants may reduce the ability of amphibians to benefit from food-rich environments or have metabolic costs. Our study demonstrates the importance of considering multiple stressors when evaluating population-level responses.

  1. Lead concentrations in bullfrog Rana catesbeiana and green frog R. clamitans tadpoles inhabiting highway drainages

    USGS Publications Warehouse

    Birdsall, C.W.; Grue, C.E.; Anderson, A.

    1986-01-01

    Lead concentrations were determined in sediment and tadpoles of bullfrogs Rana catesbeiana and green frogs R. clamitans from drainages along highways with different daily average traffic volumes (range, 4272 to I08,800 vehicles day-I) and from ponds >0.4 km from the nearest highway. Lead concentrations (mg kg--I dry weight) in sediment (7-8 to 940) were usually greater (4-5 times) than those in the tadpoles (bullfrog, 0,07 to 270; green frog, 0,90 to 240 mg kg-I). Lead concentrations in sediment (r =0.63) and in both species of tadpoles (bullfrog, r = 0.69; green frog, r = 0.57) were positively correlated with average daily traffic volume. Lead concentrations in both species of tadpoles (bullfrog, r = (). 76: green frog, r = 0.75) were also positively correlated with lead concentrations in sediment. At sites where both bullfrog and green frog tadpoles were collected. lead concentrations in the two species were closely related (r = 0.84). Lead concentrations in tadpoles living near highways may contribute to the elevated lead levels reported in wildlife that are potential tadpole predators. Dietary lead concentrations similar to those in our tadpoles have been associated with physiological and reproductive effects in some species of birds and mammals. However, additional data are needed to determine the hazards to predators of lead concentrations in tadpoles.

  2. Direct and Indirect Horizontal Transmission of the Antifungal Probiotic Bacterium Janthinobacterium lividum on Green Frog (Lithobates clamitans) Tadpoles

    PubMed Central

    Simonetti, Stephen J.; Shoemaker, William R.; Harris, Reid N.

    2016-01-01

    Amphibian populations worldwide are being threatened by the disease chytridiomycosis, which is caused by Batrachochytrium dendrobatidis. To mitigate the effects of B. dendrobatidis, bioaugmentation of antifungal bacteria has been shown to be a promising strategy. One way to implement bioaugmentation is through indirect horizontal transmission, defined as the transfer of bacteria from a host to the environment and to another host. In addition, direct horizontal transmission among individuals can facilitate the spread of a probiotic in a population. In this study, we tested whether the antifungal bacterium Janthinobacterium lividum could be horizontally transferred, directly or indirectly, in a laboratory experiment using Lithobates clamitans tadpoles. We evaluated the ability of J. lividum to colonize the tadpoles' skin and to persist through time using culture-dependent and culture-independent techniques. We also tested whether the addition of J. lividum affected the skin community in L. clamitans tadpoles. We found that transmission occurred rapidly by direct and indirect horizontal transmission, but indirect transmission that included a potential substrate was more effective. Even though J. lividum colonized the skin, its relative abundance on the tadpole skin decreased over time. The inoculation of J. lividum did not significantly alter the skin bacterial diversity of L. clamitans tadpoles, which was dominated by Pseudomonas. Our results show that indirect horizontal transmission can be an effective bioaugmentation method. Future research is needed to determine the best conditions, including the presence of substrates, under which a probiotic can persist on the skin so that bioaugmentation becomes a successful strategy to mitigate chytridiomycosis. PMID:26873311

  3. Exposure of juvenile green frogs (Lithobates clamitans) in littoral enclosures to a glyphosate-based herbicide.

    PubMed

    Edge, Christopher B; Gahl, Megan K; Pauli, Bruce D; Thompson, Dean G; Houlahan, Jeff E

    2011-07-01

    The majority of studies on the toxicity of glyphosate-based herbicides to amphibians have focused on larval life stages exposed in aqueous media. However, adult and juvenile amphibians may also be exposed directly or indirectly to herbicides. The potential for such exposures is of particular interest in the littoral zone surrounding wetlands as this is preferred habitat for many amphibian species. Moreover, it may be argued that potential herbicide effects on juvenile or adult amphibians could have comparatively greater influence on overall recruitment, reproductive potential and thus stability of local populations than effects on larvae. In this experiment, juvenile green frogs (Lithobates clamitans) were exposed to two concentrations (2.16 and 4.27 kg a.e./ha) of a glyphosate-based herbicide formulation (VisionMax®), which were based on typical application scenarios in Canadian forestry. The experimental design employed frogs inhabiting in situ enclosures established at the edge of small naturalized wetlands that were split in half using an impermeable plastic barrier. When analyzed using nominal target application rates, exposure to the glyphosate-based herbicide had no significant effect on survival, body condition, liver somatic index or the observed rate of Batrachochytrium dendrobatidis infection. However, there were marginal trends in both ANOVA analysis and post-hoc regressions regarding B. dendrobatidis infection rates and liver somatic index in relation to measured exposure estimates. Results from this study highlight the importance of field research and the need to include multiple endpoints when examining potential effects of a contaminant on non-target organisms. PMID:21536331

  4. Equations for the Cabrera-Mott kinetics of oxidation for spherical nanoparticles

    NASA Astrophysics Data System (ADS)

    Ermoline, Alexandre; Dreizin, Edward L.

    2011-03-01

    Equations describing formation of a spherical oxide shell according to the Cabrera-Mott mechanism are presented. Two different configurations of metal and oxidizer are considered: oxidation of a spherical metal particle in surrounding oxidizer, and reduction of a spherical oxide inclusion in a metal matrix. Equations for the former configuration were reported earlier but did not explicitly account for volume changes in the growing oxide shell and shrinking central core. For aluminum oxidation, the correction for these volume changes is significant for spherical particles with diameters less than 10 nm.

  5. Transcriptome resources for the frogs Lithobates clamitans and Pseudacris regilla, emphasizing antimicrobial peptides and conserved loci for phylogenetics

    USGS Publications Warehouse

    Robertson, Laura S.; Cornman, Robert S.

    2014-01-01

    We developed genetic resources for two North American frogs, Lithobates clamitans and Pseudacris regilla, widespread native amphibians that are potential indicator species of environmental health. For both species, mRNA from multiple tissues was sequenced using 454 technology. De novo assemblies with Mira3 resulted in 50 238 contigs (N50 = 687 bp) and 48 213 contigs (N50 = 686 bp) for L. clamitans and P. regilla, respectively, after clustering with CD-Hit-EST and purging contigs below 200 bp. We performed BLASTX similarity searches against the Xenopus tropicalis proteome and, for predicted ORFs, HMMER similarity searches against the Pfam-A database. Because there is broad interest in amphibian immune factors, we manually annotated putative antimicrobial peptides. To identify conserved regions suitable for amplicon resequencing across a broad taxonomic range, we performed an additional assembly of public short-read transcriptome data derived from two species of the genus Rana and identified reciprocal best TBLASTX matches among all assemblies. Although P. regilla, a hylid frog, is substantially more diverged from the ranid species, we identified 56 genes that were sufficiently conserved to allow nondegenerate primer design with Primer3. In addition to providing a foundation for comparative genomics and quantitative gene expression analysis, our results enable quick development of nuclear sequence-based markers for phylogenetics or population genetics.

  6. Ameliorative effects of sodium chloride on acute copper toxicity among Cope's gray tree frog (Hyla chrysoscelis) and green frog (Rana clamitans) embryos.

    PubMed

    Brown, Maria G; Dobbs, Emily K; Snodgrass, Joel W; Ownby, David R

    2012-04-01

    Urban stormwater runoff is composed of a mixture of components, including polycyclic aromatic hydrocarbons, metals, deicing agents, and many others. The fate of these chemicals is often in stormwater detention ponds that are used by amphibians for breeding. Among aquatic organisms, the toxic mechanism for many metals involves interference with active Na(+) and Cl(-) uptake. Addition of cations has been shown to reduce the toxicity of metals among some aquatic organisms through competitive inhibition, but no studies have investigated the interaction between NaCl and Cu among amphibian embryos and larvae. To determine the degree to which NaCl may ameliorate the toxicity of Cu to amphibian embryos and larvae, the authors exposed Hyla chrysoscelis (Cope's gray treefrogs) and Rana (Lithobates) clamitans (green frogs) to seven levels of Cu and NaCl in fully factorial experiments. When exposure was in artificial hard water, Cu was highly toxic to both species (96-h median lethal concentration [LC50] of 44.7 µg/L and 162.6 µg/L for H. chrysoscelis and R. clamitans, respectively). However, approximately 500 mg/L of NaCl eliminated Cu toxicity over the range of Cu concentrations used in the experiments (maximum 150 µg Cu/L for H. chrysoscelis and 325 µg Cu/L for R. clamitans). The current results suggest that NaCl is likely responsible for the toxic effects of NaCl and metal mixtures that might be typical of runoff from road surfaces in northern latitudes.

  7. The classical versus the Cabrera presentation system for resting electrocardiography: Impact on recognition and understanding of clinically important electrocardiographic changes.

    PubMed

    Lam, Anny; Wagner, Galen S; Pahlm, Olle

    2015-01-01

    The classical system for presentation of the 12-lead electrocardiogram (ECG) reflects the electrical activity of the heart as viewed in the transverse plane by 6 leads with a single anatomically ordered sequence, V1-V6; but in the frontal plane by 6 leads with dual sequences, I, II, and III, and aVR, aVL, and aVF. However, there is also a single anatomically ordered sequence of leads, called the Cabrera display that presents the six frontal plane leads in their anatomically ordered sequence of: aVL, I, -aVR, II, aVF, and III. Although it has been recognized that the Cabrera system has clinical diagnostic advantages compared to the classical display, it is currently only used in Sweden. The primary explanation of why the Cabrera system has not been adopted internationally has been that analog ECG recorders had technical limitations. Currently, however, the classical system is most often seen as a historical remnant that prevails because of conservatism within the cardiology community.

  8. Residence time and Posidonia oceanica in Cabrera Archipelago National Park, Spain

    NASA Astrophysics Data System (ADS)

    Orfila, A.; Jordi, A.; Basterretxea, G.; Vizoso, G.; Marbà, N.; Duarte, C. M.; Werner, F. E.; Tintoré, J.

    2005-07-01

    Flushing time and residence time are studied in a small inlet in Cabrera National Park, Western Mediterranean Sea. Flushing time is studied using ADCP in situ data. Observed flushing time data are compared with the simulations from a three-dimensional coastal ocean numerical model. Residence time is assessed using virtual lagrangian particles and studying the number remaining within the analyzed domain. Results show a good agreement between observations and modeling estimations of the flushing time (i.e. 6 days from the ADCP data and 5.6 days from the numerical model). Residence time estimations yield a broad range of values, from 1 h in the Bay to over 30 days depending also on the horizontal and vertical position where particles were released. A continuous stirred tank reactor (CSTR) model for the Port yields a value of 8.7 days. Results obtained for the residence time appear to have a determinant impact over the meadows of the seagrass Posidonia oceanica, present inside the Port. Recirculation patterns and complex flows in coastal environments create a non-uniform distribution of the areas of accumulation of non-conservative properties that indicate that residence time concept is the correct approach when studying the impact of water transport over biological communities.

  9. On the Connection between Kinetic Monte Carlo and the Burton-Cabrera-Frank Theory

    NASA Astrophysics Data System (ADS)

    Patrone, Paul; Margetis, Dionisios; Einstein, T. L.

    2013-03-01

    In the many years since it was first proposed, the Burton- Cabrera-Frank (BCF) model of step-flow has been experimentally established as one of the cornerstones of surface physics. However, many questions remain regarding the underlying physical processes and theoretical assumptions that give rise to the BCF theory. In this work, we formally derive the BCF theory from an atomistic, kinetic Monte Carlo model of the surface in 1 +1 dimensions with one step. Our analysis (i) shows how the BCF theory describes a surface with a low density of adsorbed atoms, and (ii) establishes a set of near-equilibrium conditions ensuring that the theory remains valid for all times. Support for PP was provided by the NIST-ARRA Fellowship Award No. 70NANB10H026 through UMD. Support for TLE and PP was also provided by the CMTC at UMD, with ancillary support from the UMD MRSEC. Support for DM was provided by NSF DMS0847587 at UMD.

  10. Petrology and geochemistry of the Eastern Loma de Cabrera Batholith, Dominican Republic

    SciTech Connect

    Cribb, J.W.; Lewis, J.F.

    1985-01-01

    The Eastern Loma de Cabrera Batholith, located in the NW Cordillera Central, Dominican Republic, is a heterogeneous intrusive complex composed of a zoned ultramafic-mafic core surrounded by tonalite and diorite. The batholith intrudes metasbasaltic rocks of the Duarte Complex of early Cretaceous age. The ultramafic-mafic core consists of peridotite, olivine-pyroxenite, pyroxenite, and augite-hypersthene gabbro-norite. Pyroxenites and gabbro-norites exhibit large scale interlayering and small scale layering involving a regular variation in the proportions of ortho- and clinopyroxene. Tonalities and diorites are mafic to leucocratic, some being porphyritic. Petrographic types include hornblende, hornblende-pyroxene, hornblende-biotite, and muscovite-biotite types. Aplites are abundant. Intrusive relations suggest that ultramafic-mafic complex is the oldest intrusive phase, and was partially amphibolitized during later intrusion of the felsic rocks. Ultramafic-mafic rocks contain 43-54% SiO/sub 2/ and MgO ranges from 8-45%. Trace and REE in these rocks are relatively depleted. Tonalitic rocks range in SiO/sub 2/ from 53-76%, with K/sub 2/O varying from 0.15-2.9%. In addition, they are LREE enriched. A small Eu anomaly is best explained by fractionation of plagioclase and hornblende. Trends shown by Rb-Sr data suggest that fractional crystallization of hornblende and plagioclase, that is high level fractionation, is the important factor in controlling chemical variation in the tonalites.

  11. Modeling of oxidation of aluminum nanoparticles by using Cabrera Mott Model

    NASA Astrophysics Data System (ADS)

    Ramazanova, Zamart; Zyskin, Maxim; Martirosyan, Karen

    2012-10-01

    Our research focuses on modeling new Nanoenergetic Gas-Generator (NGG) formulations that rapidly release a large amount of gaseous products and generates shock and pressure waves. Nanoenergetic thermite reagents include mixtures of Al and metal oxides such as bismuth trioxide and iodine pentoxide. The research problem is considered a spherically symmetric case and used the Cabrera Mott oxidation model to describe the kinetics of oxide growth on spherical Al nanoparticles for evaluating reaction time which a process of the reaction with oxidizer happens on the outer part of oxide layer of aluminum ions are getting in contact with an oxidizing agent and react. We assumed that a ball of Al of radius 20 to 50 nm is covered by a thin oxide layer 2-4 nm and is surrounded by abundant amount of oxygen stored by oxidizers. The ball is rapidly heated up to ignition temperature to initiate self-sustaining oxidation reaction. As a result highly exothermic reaction is generated. In the oxide layer of excess concentrations of electrons and ions are dependent on the electric field potential with the corresponding of the Gibbs factors and that it conducts to the solution of a nonlinear Poisson equation for the electric field potential in a moving boundary domain. Motion of the boundary is determined by the gradient of a solution on the boundary. We investigated oxidation model numerically, using the COMSOL software utilizing finite element analysis. The computing results demonstrate that oxidation rate increases with the decreasing particle radius.

  12. Effects of polychlorinated biphenyl 126 on green frog (Rana clamitans) and leopard frog (Rana pipiens) hatching success, development, and metamorphosis

    SciTech Connect

    Rosenshield, M.L.; Jofre, M.B.; Karasov, W.H.

    1999-11-01

    Although increasing evidence links plana chlorinated hydrocarbons, such as polychlorinated biphenyls (PCBs), to decreases in survival and reproduction of fish, mammals, and birds near Green Bay, Wisconsin, and the Great Lakes, USA, relatively little is known of their bioaccumulation or of their possible effects in amphibians. The authors exposed embryos and larvae of two ranid species commonly occurring in the Green Bay ecosystem, the green frog (Rana clamitans) and the leopard frog (Rana pipiens), to PCB 126, a model coplanar PCB compound. Nominal concentrations ranged from 0.005 to 50 {micro}g/L, and exposure lasted through metamorphosis. Tissue concentrations of PCB 126 in tadpoles that did not metamorphose by the end of the experiment ranged from 1.2 to 9,600 ng/g wet mass. No significant mortality of embryos occurred before hatching; however, survival of larvae was significantly reduced at the highest concentration for both species. Few deformities were observed, but the incidence of edema was significantly higher in tadpoles exposed to 50 {micro}g/L. Swimming speed and growth of tadpoles was also significantly reduced in this treatment. The percent of tadpoles that reached metamorphosis was significantly lower in green frogs at the highest concentration, and no leopard frogs survived past day 47 of the experiment in this treatment. At high concentrations, PCB 126 affected both ranid species; however, sublethal effects were not apparent for the parameters the authors measured at concentrations that occur in water in the Green Bay ecosystem.

  13. Trophic Discrimination Factors and Incorporation Rates of Carbon- and Nitrogen-Stable Isotopes in Adult Green Frogs, Lithobates clamitans.

    PubMed

    Cloyed, Carl S; Newsome, Seth D; Eason, Perri K

    2015-01-01

    Stable isotope analysis is an increasingly useful ecological tool, but its accuracy depends on quantifying the tissue-specific trophic discrimination factors (TDFs) and isotopic incorporation rates for focal taxa. Despite the technique's ubiquity, most laboratory experiments determining TDFs and incorporation rates have focused on birds, mammals, and fish; we know little about terrestrial ectotherms, and amphibians in particular are understudied. In this study we used two controlled feeding experiments to determine carbon (δ(13)C) and nitrogen (δ(15)N) isotope TDFs for skin, whole blood, and bone collagen and incorporation rates for skin and whole blood in adult green frogs, Lithobates clamitans. The mean (±SD) TDFs for δ(13)C were 0.1‰ (±0.4‰) for skin, 0.5‰ (±0.5‰) for whole blood, and 1.6‰ (0.6‰) for bone collagen. The mean (±SD) TDFs for δ(15)N were 2.3‰ (±0.5‰) for skin, 2.3‰ (±0.4‰) for whole blood, and 3.1‰ (±0.6‰) for bone collagen. A combination of different isotopic incorporation models was best supported by our data. Carbon in skin was the only tissue in which incorporation was best explained by two compartments, which had half-lives of 89 and 8 d. The half-life of carbon in whole blood was 69 d. Half-lives for nitrogen were 75 d for skin and 71 d for whole blood. Our results help fill a taxonomic gap in our knowledge of stable isotope dynamics and provide ecologists with a method to measure anuran diets. PMID:26658253

  14. Low detection of ranavirus DNA in wild postmetamorphic green frogs, Rana (Lithobates) clamitans, despite previous or concurrent tadpole mortality.

    PubMed

    Forzán, María J; Wood, John

    2013-10-01

    Ranavirus (Iridoviridae) infection is a significant cause of mortality in amphibians. Detection of infected individuals, particularly carriers, is necessary to prevent and control outbreaks. Recently, the use of toe clips to detect ranavirus infection through PCR was proposed as an alternative to the more frequently used lethal liver sampling in green frogs (Rana [Lithobates] clamitans). We attempted reevaluate the use of toe clips, evaluate the potential use of blood onto filter paper and hepatic fine needle aspirates (FNAs) as further alternatives, and explore the adequacy of using green frogs as a target-sampling species when searching for ranavirus infection in the wild. Samples were obtained from 190 postmetamorphic (≥1-yr-old) green frogs from five ponds on Prince Edward Island (PEI), Canada. Three of the ponds had contemporary or recent tadpole mortalities due to Frog Virus 3 (FV3) ranavirus. PCR testing for ranavirus DNA was performed on 190 toe clips, 188 blood samples, 72 hepatic FNAs, and 72 liver tissue samples. Only two frogs were ranavirus-positive: liver and toe clip were positive in one, liver only was positive in the other; all blood and FNAs, including those from the two positive frogs, were negative. Results did not yield a definitive answer on the efficacy of testing each type of sample, but resemble what is found in salamanders infected with Ambystoma tigrinum (rana)virus. Findings indicate a low prevalence of FV3 in postmetamorphic green frogs on PEI (≤2.78%) and suggest that green frogs are poor reservoirs (carriers) for the virus.

  15. Specific time of exposure during tadpole development influences biological effects of the insecticide carbaryl in green frogs (Lithobates clamitans).

    PubMed

    Boone, Michelle D; Hammond, S Austin; Veldhoen, Nik; Youngquist, Melissa; Helbing, Caren C

    2013-04-15

    The orchestration of anuran metamorphosis is initiated and integrated by thyroid hormones, which change dynamically during larval development and which may represent a target of disruption by environmental contaminants. Studies have found that some anurans experience increased rates of development when exposed to the insecticide carbaryl later in larval development, suggesting that this insecticide could affect thyroid hormone-associated biological pathways. However, the time in development when tadpoles are sensitive to insecticide exposure has not been clearly defined nor has the mechanism been tested. In two separate studies, we exposed recently hatched green frog (Lithobates clamitans) tadpoles to a single, three day carbaryl exposure in the laboratory at either 2, 4, 8, or 16 weeks post-hatching. We examined the impact of carbaryl exposure on mRNA abundance patterns in the brains of frogs following metamorphosis months after a single three day exposure (experiment 1) and in tadpole tails three days after exposure (experiment 2) using cDNA microarrays and quantitative real time polymerase chain reaction (QPCR) analyses. For tadpoles reared through metamorphosis, we measured tadpole growth and development, as well as time to, mass at, and survival to metamorphosis. Although carbaryl did not significantly impact tadpole development, metamorphosis, or survival, clear exposure-related alterations in both tail and brain transcript levels were evident when tadpoles were exposed to carbaryl, particularly in tadpoles exposed at weeks 8 and 16 post-hatching, indicating both short-term and long-term alterations in mRNA expression. These results indicate that carbaryl can have long-lasting effects on brain development when exposure occurs at sensitive developmental stages, which may have implications for animal fitness and function later in the life cycle.

  16. Effects of Local Habitat Variation on the Behavioral Ecology of Two Sympatric Groups of Brown Howler Monkey (Alouatta clamitans)

    PubMed Central

    Grelle, Carlos E. V.; Strier, Karen B.; Boubli, Jean P.

    2015-01-01

    Although the brown howler monkey (Alouatta clamitans) is a relatively well-studied Neotropical primate, its behavioral and dietary flexibility at the intra-population level remains poorly documented. This study presents data collected on the behavior and ecology of two closely located groups of brown howlers during the same period at the RPPN Feliciano Miguel Abdala in southeastern Brazil. One group occupied a primary valley habitat, henceforth the Valley Group (VG), and the other group occupied a regenerating hillside habitat, the Hill Group (HG). We hypothesized differences in the behavior and ecological parameters between these sympatric groups due to the predicted harsher conditions on the hillside, compared to the valley. We measured several habitat parameters within the home range of both groups and collected data on the activity budget, diet and day range lengths, from August to November 2005, between dawn and dusk. In total, behavioral data were collected for 26 (318 h) and 28 (308 h) sampling days for VG and HG, respectively. As we predicted, HG spent significantly more time feeding and consumed less fruit and more leaves than VG, consistent with our finding that the hillside habitat was of lower quality. However, HG also spent less time resting and more time travelling than VG, suggesting that the monkeys had to expend more time and energy to obtain high-energy foods, such as fruits and flowers that were more widely spaced in their hill habitat. Our results revealed that different locations in this forest vary in quality and raise the question of how different groups secure their home ranges. Fine-grained comparisons such as this are important to prioritize conservation and management areas within a reserve. PMID:26147203

  17. Origin and spread of the SRY gene on the X and Y chromosomes of the rodent Microtus cabrerae: role of L1 elements.

    PubMed

    Marchal, Juan A; Acosta, Manuel J; Bullejos, Mónica; Díaz de la Guardia, Rafael; Sánchez, Antonio

    2008-02-01

    In the rodent species Microtus cabrerae, males as well as females present several copies of the SRY gene, a single-copy gene located on the Y chromosome in most mammals. Using different PCR approaches, we have characterized the sequence, structure, and organization of the SRY copies and their flanking regions distributed on the X and Y chromosomes of this species. All copies of SRY analyzed, including those from the Y chromosome, proved to be nonfunctional pseudogenes, as they have internal stop codons. In addition, we demonstrated the association of SRY pseudogenes with different fragments of L1 and LTR retroelements in both sex chromosomes of M. cabrerae. Examining the possible origin of SRY pseudogene and retroposons association, we propose that retroposons could have been involved in the mechanism of SRY gene amplification on the Y chromosome and in the transference of the Y-linked SRY copies to the X-chromosome heterochromatin.

  18. Developmental pathway from leaves to galls induced by a sap-feeding insect on Schinus polygamus (Cav.) Cabrera (Anacardiaceae).

    PubMed

    Dias, Graciela G; Ferreira, Bruno G; Moreira, Gilson R P; Isaias, Rosy M S

    2013-03-01

    Galling sap-feeding insects are presumed to cause only minor changes in host plant tissues, because they usually do not require development of nutritive tissues for their own use. This premise was examined through comparison of the histometry, cytometry and anatomical development of non-galled leaves and galls of Calophya duvauae (Scott) (Hemiptera: Calophyidae) on Schinus polygamus (Cav.) Cabrera (Anacardiaceae). Cell fates changed from non-galled leaves to galls during the course of tissue differentiation. C. duvauae caused changes in dermal, ground, and vascular systems of the leaves of S. polygamus. Its feeding activity induced the homogenization of the parenchyma, and the neoformation of vascular bundles and trichomes. The histometric and cytometric data revealed compensatory effects of hyperplasia and cell hypertrophy in the epidermis, with hyperplasia predominating in the adaxial epidermis. There was a balance between these processes in the other tissues. Thus, we found major differences between the developmental pathways of non-galled leaves and galls. These changes were associated with phenotypic alterations related to shelter and appropriate microenvironmental conditions for the gall inducer. The nondifferentiation of a typical nutritive tissue in this case was compared to other non-phylogenetically related arthropod gall systems, and is suggested to result from convergence associated with the piercing feeding apparatus of the corresponding gall-inducer.

  19. Geomorphic analysis of the Sierra Cabrera, an active pop-up in the constrictional domain of conjugate strike-slip faults: The Palomares and Polopos fault zones (eastern Betics, SE Spain)

    NASA Astrophysics Data System (ADS)

    Giaconia, Flavio; Booth-Rea, G.; Martínez-Martínez, J. M.; Azañón, J. M.; Pérez-Peña, J. V.

    2012-12-01

    The NNE-SSW sinistral Palomares and the conjugate dextral WNW-ESE striking Polopos fault zones terminate in the Sierra Cabrera antiform. In order to test the Quaternary activity and topographic relief control in the termination of these fault zones, here we present new qualitative and quantitative geomorphic analyses supported by a new structural map of the region. The main mountain fronts of the Cabrera antiform are formed by the North and South Cabrera reverse faults that merge laterally into the Palomares and Polopos faults, respectively. These faults produce knickpoints, stream deflections, complex basin hypsometric curves, high SLk anomalies and highly eroded basins in their proximity. Furthermore, the drainage network shows an S-shaped pattern reflecting progressive anticlockwise rotation related to the sinistral Palomares fault zone. The estimated uplift rates determined by the integration between mountain front sinuosity index and valley floor width to height ratio are larger than those obtained for strike-slip faults in the eastern Betics. These larger uplift rates with our geomorphic and structural dataset indicate that the topographic relief of the Sierra Cabrera antiform is controlled by reverse faults that form a pop-up structure in the constrictional domain between the larger Palomares-Polopos conjugate strike-slip faults. Existing GPS geodetic data suggest that the North and South Cabrera reverse faults probably accommodate a large part of Africa-Iberia convergence in the region.

  20. Potential endocrine disruption of sexual development in free ranging male northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) from areas of intensive row crop agriculture.

    PubMed

    McDaniel, Tana V; Martin, Pamela A; Struger, John; Sherry, Jim; Marvin, Chris H; McMaster, Mark E; Clarence, Stacey; Tetreault, Gerald

    2008-07-30

    Intensive row crop agriculture (IRCA) for corn and soybean production is predominant in eastern and central North America. IRCA relies heavily on pesticide and nutrient inputs to maximize production under conventional systems. In 2003-2005, we assessed the occurrence of a suite of potential endocrine effects in amphibians inhabiting farm ponds and agricultural drains in IRCA areas of southwestern Ontario. Effects were compared to amphibians from two agricultural reference sites as well as four non-agricultural reference sites. Pesticide and nutrient concentrations were also determined in water samples from those sites. Atrazine and metolachlor were detected in most samples, exceeding 1 microg L(-1) at some sites. Blood samples were taken from northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) for analysis of circulating sex steroids and vitellogenin-like protein (Vtg-lp), a biomarker of exposure to environmental estrogens. Gonads were histologically examined for evidence of abnormalities. Some evidence of exposure to endocrine disrupting compounds was apparent from the data. The occurrence of testicular ovarian follicles (TOFS) in male R. pipiens was significantly higher (42%; p<0.05) at agricultural sites, particularly those in Chatham county compared to frogs from reference sites (7%). There was no difference in circulating sex steroid levels between frogs from agricultural and reference sites and sex steroid levels did not correlate with pesticide concentrations in the environment. No differences were detected in the gonadosomatic indices or stage of spermatogenesis between frogs from agricultural and non-agricultural regions (p>0.05). Plasma Vtg-lp was detected in only one male R. pipiens from an agricultural site. Neither gonad size, gonad maturity nor sex steroid levels differed between normal males and those with testicular oocytes. Although the proportion of testicular oocytes did not correlate directly with atrazine concentrations, it

  1. Assessment of RELAP5/MOD2 against a pressurizer spray valve inadverted fully opening transient and recovery by natural circulation in Jose Cabrera Nuclear Station

    SciTech Connect

    Arroyo, R.; Rebollo, L.

    1993-06-01

    This document presents the comparison between the simulation results and the plant measurements of a real event that took place in JOSE CABRERA nuclear power plant in August 30th, 1984. The event was originated by the total, continuous and inadverted opening of the pressurizer spray valve PCV-400A. JOSE CABRERA power plant is a single loop Westinghouse PWR belonging to UNION ELECTRICA FENOSA, S.A. (UNION FENOSA), an Spanish utility which participates in the International Code Assessment and Applications Program (ICAP) as a member of UNIDAD ELECTRICA, S.A. (UNESA). This is the second of its two contributions to the Program: the first one was an application case and this is an assessment one. The simulation has been performed using the RELAP5/MOD2 cycle 36.04 code, running on a CDC CYBER 180/830 computer under NOS 2.5 operating system. The main phenomena have been calculated correctly and some conclusions about the 3D characteristics of the condensation due to the spray and its simulation with a 1D tool have been got.

  2. Geomorphic analysis of the Sierra Cabrera, an active pop-up in the constriction domain of conjugate strike-slip faults: the Palomares and Polopos fault zones (eastern Betics, SE Spain)

    NASA Astrophysics Data System (ADS)

    Giaconia, F.; Booth-Rea, G.; Martínez-Martínez, J. M.; Pérez-Peña, V.; Azañón, J. M.

    2012-04-01

    Segments of the Quaternary sinistral Carboneras and Palomares fault zones, striking NE-SW and NNE-SSW, respectively, terminate in the Sierra Cabrera antiform together with the conjugate dextral WNW-ESE striking Polopos fault zone. In the constriction domain between these fault zones a pop-up structure occurs formed by the North and the South Cabrera reverse faults that bound the northern and the southern hillslopes, respectively. In order to test the Quaternary activity and relief control of these fault zones, here we present new qualitative and quantitative geomorphic analyses for the Sierra Cabrera using the following indices: mountain-front sinuosity, valley floor width-to-height ratio, drainage basin asymmetry factor, basin hypsometric curve and integral, and the SLk index. These analyses were performed with the aid of several maps such as the SLk and the minimum bulk erosion map. Qualitative observations carried out on the drainage network highlight the existence of a Late Miocene fold-related drainage network and a following late Miocene to Plio-Quaternary fault-related one. Integrating the mountain-front sinuosity and the valley floor width-to-height ratio for each mountain front we estimated the uplift rates associated to each of them. Fault-related mountain-fronts with a N50-60°E strike have reverse kinematics and uplift rates larger than 0.5 m ky-1 (e.g. North and South Cabrera reverse faults), whereas those with N20-30°E and N90-100°E strikes show oblique strike-slip kinematics and show lower uplift rates, between 0.05 and 0.5 m ky-1 (e.g. the Palomares and the Polopos fault segments). Furthermore, these faults produce knickpoints, complex basin hypsometric curves, high SLk anomalies and highly eroded basins above the fault traces. The estimated uplift rates are larger than those obtained from other authors for strike-slip faults in the eastern Betics that range between 0.1 and 0.05 m ky-1 (e.g. Palomares and southern Carboneras strike-slip fault

  3. Chromosomal aberrations induced by Dispersion Yellow 3 in Rana clamitans larvae during tail regeneration.

    PubMed

    Gray, P S; Hunter, R; Patterson, R M

    1979-01-01

    Azo dyes have been shown to be mutagenic and toxic in a variety of organisms. The azo dye, Dispersion Yellow 3 is a pollutant in the river water supply of Northern Georgia. Preliminary and definitive studies have indicated that it is mutagenic in micro-organisms and causes several malformations in chicken embryos. The present study revealed that when larvae are exposed to the dye during tail regeneration, several aberrations are seen in the squash preparations from regenerates. Included are gaps (the most frequent abnormality), dicentrics, rings and breaks. The data suggest that this azo dye deserves more detailed study to determine its mutagenicity.

  4. BIOCONCENTRATION AND METABOLISM OF ALL-TRANS RETINOIC ACID BY RANA SYLVATICA AND RANA CLAMITANS TADPOLES

    EPA Science Inventory

    Retinoids, which are Vitamin A derivatives, are important signaling molecules that regulate processes critical for development in all vertebrates. The objective of our study was to examine uptake and metabolism of all-trans retinoic acid...

  5. Notes on Interface Growth Kinetics 50 Years After Burton, Cabrera and Frank

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2003-01-01

    This is an overview of basic problems of crystal growth kinetics controlled by processes on the crystal interface with solution and melt. Included, also, are results on fundamental issues concerning morphological stability of crystal-solution interface that engage both interface kinetics and mass transport by diffusion and convection.

  6. Notes on Interface Growth Kinetics 50 Years after Burton, Cabrera and Frank

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2004-01-01

    This overview is devoted to some unresolved basic problems in crystal growth kinetics. The density wave approach to propagation of a spatially diffuse interface between a growing crystal and its simple (e.g., metallic) melt is discussed is Section 2. This approach allows for the calculation of kinetic coefficients and is an alternative to the localized interface concept in which each atom belongs to either a solid or a liquid. Sections 3 and 4 deals mainly with layer growth from solution. Mutual retardation of the growth steps via their bulk and d a c e diffusion fields is the major subject. The influence of solution flow on step bunching (Section 4) suggests the essential influence of bulk diffusion on the surface morphology. The flow within the solution boundary layer enhances step-step interaction, influences the step bunching process and the resulting step pattern morphology on the growing surface. Recent experiments on the rates at which strongly polygonized steps on protein and small molecule crystals propagate during growth from solution are analyzed in Section 5 . We have shown that the step segments may be "singular" and that "one-dimensional nucleation" may be the rate limiting stage for the segments that are shorter or comparable in length to the thermodynamically equilibrium interlink distance. In this case, the reciprocal dependence of the segment propagation rate on the segment length that follow from the Gibbs-Thompson law, should be replaced by an abrupt switch from zero to a finite constant velocity. Until recently, the Kossel crystal remained the only model used in crystal growth theory. In such Kossel Gibbs-Thomson law, should be replaced by an abrupt switch &om zero to a finite constant velocity. crystals, all kinks at the steps are identical and the kink rate is a linear function of the supersaturation. In the non-Kossel crystals, there may be several kink configurations characterized by different geometries and energies. These configurations should appear in a specific sequence when each new lattice unit cell is filled. As a result of such a cooperative interaction within the unit cell, a non-linear dependence of the kink rate on the vapor pressure or solution concentration in excess over the equilibrium value should be expected.

  7. Synteny of human chromosomes 14 and 15 in the platyrrhines (Primates, Platyrrhini)

    PubMed Central

    2009-01-01

    In order to study the intra- and interspecific variability of the 14/15 association in Platyrrhini, we analyzed 15 species from 13 genera, including species that had not been described yet. The DNA libraries of human chromosomes 14 and 15 were hybridized to metaphases of Alouatta guariba clamitans, A. caraya, A. sara, Ateles paniscus chamek, Lagothrix lagothricha, Brachyteles arachnoides, Saguinus midas midas, Leontopithecus chrysomelas, Callimico goeldii, Callithrix sp., Cebus apella, Aotus nigriceps, Cacajao melanocephalus,Chiropotes satanas and Callicebus caligatus. The 14/15 hybridization pattern was present in 13 species, but not in Alouatta sara that showed a 14/15/14 pattern and Aotus nigriceps that showed a 15/14/15/14 pattern. In the majority of the species, the HSA 14 homologue retained synteny for the entire chromosome, whereas the HSA 15 homologue displayed fragmented segments. Within primates, the New World monkeys represent the taxon with the highest variability in chromosome number (2n = 16 to 62). The presence of the HSA 14/15 association in all species and subspecies studied herein confirms that this association is the ancestral condition for platyrrhines and that this association has been retained in most platyrrhines, despite the occurrence of extensive inter- and intrachromosomal rearrangements in this infraorder of Primates. PMID:21637455

  8. Synteny of human chromosomes 14 and 15 in the platyrrhines (Primates, Platyrrhini).

    PubMed

    Gifalli-Iughetti, Cristiani; Koiffmann, Célia P

    2009-10-01

    In order to study the intra- and interspecific variability of the 14/15 association in Platyrrhini, we analyzed 15 species from 13 genera, including species that had not been described yet. The DNA libraries of human chromosomes 14 and 15 were hybridized to metaphases of Alouatta guariba clamitans, A. caraya, A. sara, Ateles paniscus chamek, Lagothrix lagothricha, Brachyteles arachnoides, Saguinus midas midas, Leontopithecus chrysomelas, Callimico goeldii, Callithrix sp., Cebus apella, Aotus nigriceps, Cacajao melanocephalus,Chiropotes satanas and Callicebus caligatus. The 14/15 hybridization pattern was present in 13 species, but not in Alouatta sara that showed a 14/15/14 pattern and Aotus nigriceps that showed a 15/14/15/14 pattern. In the majority of the species, the HSA 14 homologue retained synteny for the entire chromosome, whereas the HSA 15 homologue displayed fragmented segments. Within primates, the New World monkeys represent the taxon with the highest variability in chromosome number (2n = 16 to 62). The presence of the HSA 14/15 association in all species and subspecies studied herein confirms that this association is the ancestral condition for platyrrhines and that this association has been retained in most platyrrhines, despite the occurrence of extensive inter- and intrachromosomal rearrangements in this infraorder of Primates.

  9. VizieR Online Data Catalog: Eclipsing binaries in CoRoT-LRc01 field (Cabrera+, 2009)

    NASA Astrophysics Data System (ADS)

    Cabrera, J.; Fridlund, M.; Ollivier, M.; Gandolfi, D.; Csizmadia, Sz.; Alonso, R.; Aigrain, S.; Alapini, A.; Almenara, J.-M.; Barge, P.; Bonomo, A. S.; Borde, P.; Bouchy, F.; Bruntt, H.; Carone, L.; Carpano, S.; Deeg, H. J.; de La, Reza R.; Deleuil, M.; Dvorak, R.; Erikson, A.; Gillon, M.; Gondoin, P.; Guenther, E. W.; Guillot, T.; Hartmann, M.; Hatzes, A.; Hebrard, G.; Jorda, L.; Lammer, H.; Leger, A.; Llebaria, A.; Lovis, C.; Magain, P.; Mayor, M.; Mazeh, T.; Moutou, C.; Ofir, A.; Paetzold, M.; Pepe, F.; Pont, F.; Queloz, D.; Rabus, M.; Rauer, H.; Regulo, C.; Renner, S.; Rouan, D.; Samuel, B.; Santerne, A.; Schneider, J.; Shporer, A.; Stecklum, B.; Tingley, B.; Udry, S.; Wuchterl, G.

    2010-01-01

    The 11408 targets observed by CoRoT were selected using the information gathered in the database Exo-Dat (Deleuil et al. 2009AJ....138..649D; Meunier et al. 2007, ASP Conf., 376, 339), built with dedicated ground based photometric observations in the visible and near IR bands from 2MASS catalog. (3 data files).

  10. The complete mitochondrial genome sequence of Hepatozoon catesbianae (Apicomplexa: Coccidia: Adeleorina), a blood parasite of the green frog, Lithobates (formerly Rana) clamitans.

    PubMed

    Leveille, Alexandre N; Ogedengbe, Mosun E; Hafeez, Mian A; Tu, Hsiang-Hsien Abby; Barta, John R

    2014-10-01

    A complete mitochondrial genome for the blood parasite Hepatozoon catesbianae (Alveolata; Apicomplexa; Coccidia; Adeleorina; Hepatozoidae) was obtained through PCR amplification and direct sequencing of resulting PCR products. The mitochondrial genome of H. catesbianae is 6,397 bp in length and contains 3 protein-coding genes (cytochrome c oxidase subunit I [COI]; cytochrome c oxidase subunit III [COIII]; and cytochrome B [CytB]). Sequence similarities to previously published mitochondrial genomes of other apicomplexan parasites permitted annotation of 23 putative rDNA fragments in the mitochondrial genome of H. catesbianae, 14 large subunit rDNA fragments, and 9 small subunit rDNA fragments. Sequences corresponding to rDNA fragments RNA5, RNA8, RNA11, and RNA19 of Plasmodium falciparum were not identified in the mitrochondrial genome sequence of H. catesbianae. Although the presence of 3 protein-coding regions and numerous putative rDNA fragments is a feature typical for apicomplexan mitochondrial genomes, the mitochondrial genome of H. catesbianae possesses a structure and gene organization that is distinct among the Apicomplexa. This is the first complete mitochondrial genome sequence obtained from any apicomplexan parasite in the suborder Adeleorina.

  11. Feeding Strategies of Brown Howler Monkeys in Response to Variations in Food Availability

    PubMed Central

    Chaves, Óscar M.; Bicca-Marques, Júlio César

    2016-01-01

    Primates display varying degrees of behavioral flexibility that allow them to adjust their diet to temporal changes in food availability. This trait might be critical for the survival of folivorous-frugivorous species inhabiting small forest fragments, where the availability of food resources tends to be lower than in large fragments and continuous forests. However, the scarcity of studies addressing this issue hampers our understanding of the adaptive behaviors that favor the survival of these primates in low-quality habitats. We conducted a 36-mo study testing the hypothesis that brown howler monkeys (Alouatta guariba clamitans) are able to adjust their diet in response to local and seasonal changes in resource availability. We compared the diet of six free-ranging groups inhabiting three small (<10 ha) and three large (>90 ha) Atlantic forest fragments in southern Brazil and estimated the temporal availability of their top food species (i.e., those species that together contribute ≥80% of total feeding records). We found that brown howlers exploited similarly rich diets in small (45, 54, and 57 plant species) and large (48, 51, and 56 species) fragments. However, intermonth diet similarity was higher for groups in small fragments, where howlers also fed on plant items from nine alien species. Fruits and leaves were the most consumed plant items in both small (42% and 49% of feeding records, respectively) and large (51% and 41%, respectively) fragments. The consumption of young leaves was higher in small than in large fragments, whereas the consumption of other plant items did not show a pattern related to fragment size. Regarding the contribution of growth forms as food sources, only the exploitation of palms showed a pattern related to fragment size. Palms contributed more to the diet of groups inhabiting large fragments. The availability of seasonal food items–ripe fruits and young leaves–influenced their consumption in both habitat types. Therefore

  12. Diabrotica collicola (Coleoptera: Chrysomelidae)a new species of leaf beetle from Argentina Discussion and key to some similar species of the Diabrotica virgifera group

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The new species Diabrotica collicola Cabrera & Cabrera Walsh is described and illustrated based on specimens collected from Balcozna, Catamarca Province (Argentina). A full description is provided and includes morphological characters of the mouthparts, hind wing venation, binding patch, metendoster...

  13. On the Prepuna biogeographic province: A nomenclatural clarification.

    PubMed

    Morrone, Juan J; Ezcurra, Cecilia

    2016-06-29

    The nomenclatural status of the Prepuna province sensu Cabrera (1951) and sensu Morrone (1999) is clarified. The Prepuna province sensu Cabrera (1951) is demoted to a district of the Monte province, stat. nov. The valid name of the Prepuna province sensu Morrone (1999) is Cuyan High Andean province Cabrera, 1971, stat. nov. Diagnoses of these areas are provided and their endemic taxa are listed.

  14. 77 FR 75105 - Advisory Committee on Beginning Farmers and Ranchers; Intent To Renew and Request for Nominations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-19

    ... 31, 2012. FOR FURTHER INFORMATION CONTACT: Mrs. R. J. Cabrera, Designated Federal Official, USDA OAO...) 720-7704; Email: rj.cabrera@osec.usda.gov . ADDRESSES: Nomination packages may be sent by postal mail or commercial delivery to: Mrs. R.J. Cabrera, Designated Federal Official, USDA OAO,...

  15. 75 FR 68783 - Clean Water Act Section 303(d): Availability of List Decisions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-09

    ...: Comments on the proposed decisions should be sent to Valentina Cabrera Stagno, Water Division (WTR-2), U.S...-3434, facsimile (415) 947- 3537, e-mail cabrera-stagno.valentina@epa.gov . Oral comments will not be... or calling Valentina Cabrera Stagno. Underlying documentation comprising the record for...

  16. On the Prepuna biogeographic province: A nomenclatural clarification.

    PubMed

    Morrone, Juan J; Ezcurra, Cecilia

    2016-01-01

    The nomenclatural status of the Prepuna province sensu Cabrera (1951) and sensu Morrone (1999) is clarified. The Prepuna province sensu Cabrera (1951) is demoted to a district of the Monte province, stat. nov. The valid name of the Prepuna province sensu Morrone (1999) is Cuyan High Andean province Cabrera, 1971, stat. nov. Diagnoses of these areas are provided and their endemic taxa are listed. PMID:27395671

  17. 77 FR 77015 - Advisory Committee on Beginning Farmers and Ranchers Request for Nominations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-31

    ... Federal Register (FR DOC 2012-30471, Pages 75105-75106) a Notice of Intent To Renew and Request for... received on or before January 15, 2013. FOR FURTHER INFORMATION CONTACT: Mrs. R. J. Cabrera, Designated... (202) 720-6350; Fax (202) 720-7704; Email: rj.cabrera@osec.usda.gov . ADDRESSES: Nomination...

  18. CONFIRMATORY SURVEY OF THE DEFENSE LOGISTICS AGENCY, DEFENSE NATIONAL STOCKPILE CENTER NEW HAVEN DEPOT, NEW HAVEN, INDIANA

    SciTech Connect

    E.M. Harpenau

    2010-02-19

    The objectives of the radiological confirmatory survey were to collect adequate radiological data for use in evaluating the radiological condition of NHD land areas, warehouses, and support buildings. The data generated from the confirmatory survey activities were used to evaluate the results of the Final Status Survey Report (FSSR) submitted by Cabrera Services (Cabrera 2009). Cabrera has stated that all radioactive materials have been removed and that remediation of the open land areas and structure surfaces was complete, and that the NHD meets the criteria for unrestricted use.

  19. Taking care of your new hip joint

    MedlinePlus

    ... Cabrera AL. Total hip replacement. In: Frontera, WR, Silver JK, Rizzo TD, eds. Essentials of Physical Medicine ... Groomes TE. Total knee replacement. In: Frontera, WR, Silver JK, Rizzo TD, eds. Essentials of Physical Medicine ...

  20. Conversacion sobre "Tres tristes tigres". Una entrevista de Rita Guibert (A Conversation about "Three Sad Tigers". An Interview with Rita Guibert)

    ERIC Educational Resources Information Center

    Cabrera Infante, Guillermo

    1971-01-01

    Interview took place in London, England, on October 5, 1970 between Cuban writer Guillermo Cabrera Infante and journalist Rita Guibert. Special issue dedicated to contemporary Spanish American literature. (DS)

  1. Juvenile frogs compensate for small metamorph size with terrestrial growth: Overcoming the effects of larval density and insecticide exposure

    USGS Publications Warehouse

    Boone, M.D.

    2005-01-01

    I reared four species of anurans (Rana sphenocephala [Southern Leopard Frog], Rana blairi [Plains Leopard Frog], Rana clamitans [Green Frog], and Bufo woodhousii [Woodhouse's Toad]) for seven to 12 months in small, outdoor terrestrial enclosures (1 x 2 m) to examine the consequences of larval competition (via density) and contaminant exposure (via the insecticide carbaryl). I added six Rana clamitans, eight Rana sphenocephala, eight Rana blairi, and 10 Bufo woodhousii to terrestrial enclosures shortly after metamorphosis and recaptured them during the following spring. All anurans from low-density ponds were significantly larger than those from high-density ponds, but these size differences did not significantly affect survival to or size at spring emergence. However, R. sphenocephala, R. blairi, and R. clamitans that survived to spring had been larger at metamorphosis on average than those that did not survive; in contrast, B. woodhousii that survived the winter were smaller at metamorphosis on average than those that did not survive. Carbaryl exposure affected mass at metamorphosis of R. clamitans and B. woodhousii that were added to enclosures, but this difference disappeared or did not increase by spring emergence. Overall, exposure to carbaryl during the larval period did not have any apparent effects on survival or growth during the terrestrial phase. In my study, anurans were able to offset small size at metamorphosis with terrestrial growth, although there was a trend of reduced overwinter survival for ranid species that metamorphosed at a smaller size. Copyright 2005 Society for the Study of Amphibians and Reptiles.

  2. Incongruence in the pattern and timing of intra-specific diversification in bronze frogs and bullfrogs (Ranidae).

    PubMed

    Austin, James D; Zamudio, Kelly R

    2008-09-01

    We compare patterns of lineage divergence in mitochondrial DNA (mtDNA) sequences of two protein-encoding mitochondrial genes (cyt b and ND2) in two ecologically similar, co-distributed, and closely related ranid frogs (Rana clamitans and Rana catesbeiana), that are geographically widespread, and frequently syntopic. We identified three lineages in R. clamitans, separated by 0.5% to 2.1% net corrected sequence divergence, comparable to two R. catesbeiana lineages separated by 0.6%. The geographic pattern of lineage distribution differed notably between the two species. In R. clamitans, we found a Coastal Plain-Appalachian (CPA) lineage restricted to south and east of the Appalachian Mountains and a widespread lineage that encompassing nearly all the sampled range. A third distinct and divergent lineage was detected in one location in the southwest portion of the range (Louisiana). This pattern contrasts with the east-west pattern in R. catesbeiana, and reflects possible differences in refugial dynamics and patterns of range expansion. Although both species have undergone range expansion and population growth, coalescent reconstruction of N(e) reflects larger lineages but more recent divergence in R. clamitans relative to R. catesbeiana, reflecting significant differences in population history or divergent patterns of molecular evolution at mtDNA.

  3. A 3-D QSAR-BASED IDENTIFICATION ALGORITHM FOR POTENTIAL ESTROGEN RECEPTOR LIGANDS

    EPA Science Inventory

    Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens, R. clamitans, and R. septe...

  4. AMBIENT SOLAR UV RADIATION CAUSES MORTALITY IN LARVAE OF THREE SPECIES OF RANA

    EPA Science Inventory

    Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens, R. clamitans, and R. septe...

  5. Effect of road deicing salt on the susceptibility of amphibian embryos to infection by water molds.

    PubMed

    Karraker, Nancy E; Ruthig, Gregory R

    2009-01-01

    Some causative agents of amphibian declines act synergistically to impact individual amphibians and their populations. In particular, pathogenic water molds (aquatic oomycetes) interact with environmental stressors and increase mortality in amphibian embryos. We documented colonization of eggs of three amphibian species, the wood frog (Rana sylvatica), the green frog (Rana clamitans), and the spotted salamander (Ambystoma maculatum), by water molds in the field and examined the interactive effects of road deicing salt and water molds, two known sources of mortality for amphibian embryos, on two species, R. clamitans and A. maculatum in the laboratory. We found that exposure to water molds did not affect embryonic survivorship in either A. maculatum or R. clamitans, regardless of the concentration of road salt to which their eggs were exposed. Road salt decreased survivorship of A. maculatum, but not R. clamitans, and frequency of malformations increased significantly in both species at the highest salinity concentration. The lack of an effect of water molds on survival of embryos and no interaction between road salt and water molds indicates that observations of colonization of these eggs by water molds in the field probably represent a secondary invasion of unfertilized eggs or of embryos that had died of other causes. Given increasing salinization of freshwater habitats on several continents and the global distribution of water molds, our results suggest that some amphibian species may not be susceptible to the combined effects of these factors, permitting amphibian decline researchers to devote their attention to other potential causes.

  6. Organic carbon inputs to the sea bottom of the Mallorca continental slope

    NASA Astrophysics Data System (ADS)

    Pasqual, Catalina; Calafat, Antoni; Lopez-Fernandez, Pilar; Pusceddu, Antonio

    2015-08-01

    To assess the origin and degradation state of the organic particles sinking towards the sea bottom of the Mallorca continental slope, the major inorganic and organic components of the total mass flux and its biochemical composition (in terms of protein, carbohydrate, lipid and phytopigment contents) have been analysed. Two instrumented lines were deployed at the western (Sóller station, Balearic sub-basin) and southern (Cabrera station, Algerian sub-basin) slopes of Mallorca Island, 900 m depth from November 2009 to January 2011. The two locations are characterized by putatively different environmental settings. Settled material at Sóller station has higher lithogenic contents when compared with the Cabrera one. Such difference can be explained by the synergistic presence in the Sóller station of large inputs of resuspended material due to the mesoscale variability of the Balearic current and the impact of bottom trapped waves. On the other hand, at the Cabrera station sinking particles are characterized by OM and opal percentages higher than those recorded at the Sóller station. This result points out that organic particles reaching the sea floor at the Cabrera station have a pre-eminent pelagic origin. Based on analyses of the C and N stable isotopes of the sinking material, our results also highlight that, overall, the OM reaching the sea floor at the Mallorca slope is mostly of marine origin. In general, the OM settled at the Sóller station has a higher nutritional value than that at the Cabrera one. Such a difference, occurring across a relatively reduced spatial scale, let us hypothesizing that the nutritionally richer particles descending in the Cabrera station are exposed to a less energetic environment than that in the Sóller setting. This would lead to higher settling velocity of particles in the Sóller setting which in turn would result in lower degradation rates of particles during their descent towards the sea bottom.

  7. Alkaline single-cell gel (comet) assay and genotoxicity monitoring using two species of tadpoles.

    PubMed

    Ralph, S; Petras, M; Pandrangi, R; Vrzoc, M

    1996-01-01

    Small bodies of water (e.g., creeks, ponds, and drainage ditches) have received very little attention in genotoxicity studies, yet these areas are important because they are often the first to be affected by industrial effluents, sewage contaminants, accidental spills, internal combustion engine emissions, landfill runoffs, and pesticide uses. To address this deficiency, we examined erythrocytes in two species of tadpoles, Rana clamitans and Bufo americanus, using the alkaline single-cell gel (SCG) ("comet") assay. This approach involves detection, under alkaline conditions, of cell DNA fragments, which on electrophoresis migrate from the nuclear core, resulting in a "comet-with-tail" formation. Exposure of R. clamitans todpoles to a range of concentrations of methyl methanesulfonate (MMS) produced a linear increase in DNA length to DNA core width ratios. This is consistent with findings in a number of other species. Time-dose experiments using MMS suggest that the peak level of DNA damage in R. clamitans todpoles occurred 42 hr after exposure. B. americanus tadpoles exposed to 6.25 mg/l of MMS for 12 hours had a significant increase in DNA damage over that seen in the controls. Freshly caught R. clamitans tadpoles from Highgate and B. americanus tadpoles from Duart, both on the north shore of Lake Erie, gave ratios of 2.78 and 2.07, respectively. This region of Ontario is a prime agricultural area and pesticide use is extensive. Tadpoles from Highgate and Duart, maintained in the laboratory for 4 months and 6 weeks, respectively, gave ratios of 1.29 and 1.44. The results of the SCG procedure in tadpoles indicate that this assay is extremely sensitive and suitable for detecting genotoxicity in the environment.

  8. Flow cytometry used to assess genetic damage in frogs from farm ponds

    USGS Publications Warehouse

    Bly, B.L.; Knutson, M.G.; Sandheinrich, M.B.; Gray, B.R.; Jobe, D.A.

    2004-01-01

    Flow cytometry (FC) is a laboratory method used to detect genetic damage induced by environmental contaminants and other stressors in animals, including amphibians. We tested FC methods on three species of ranid frogs collected from farm ponds and natural wetlands in southeastern Minnesota. We compared FC metrics for Rana clamitans between ponds with direct exposure to agricultural contaminants and reference (unexposed) ponds. Concentrations of atrazine in water from our farm ponds ranged from 0.04 to 0.55 ppb. We found that R. clamitans from exposed ponds had DNA content similar to frogs from unexposed ponds. Pond-averaged C-values (a measure of DNA content) ranged from 6.53 to 7.08 for R. pipiens (n . 13), 6.55 to 6.60 for R. clamitans (n . 40) and 6.74 for R. palustris (n . 5). Among all species, the mean sample CVs ranged from 1.91 (R. palustris) to 6.31 (R. pipiens). Deformities were observed in only 2 of 796 individuals among all species and occurred in both reference and exposed ponds. Although we did not detect evidence of DNA damage associated with agriculture in our study, we demonstrated the potential of FC for screening amphibian populations for genetic damage. Metrics from a variety of amphibian species and locations as well as laboratory studies are needed to further assess the value of FC for monitoring amphibian genetic integrity in contaminated sites.

  9. Epizootiological studies of Amblyospora camposi (Microsporidia: Amblyosporidae) in Culex renatoi (Diptera: Culicidae) and Paracyclops fimbriatus fimbriatus (Copepoda: Cyclopidae) in a bromeliad habitat.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The epizootiology of Amblyospora camposi was studied in a natural population of Culex renatoi, a bromeliad-inhabiting mosquito, and its intermediate host, Paracyclops fimbriatus fimbriatus, over a 2-year period. Twenty Eryngium cabrerae plants were sampled monthly from January 2003 to January 2005 ...

  10. Mexican Americans Acquiring Bachelor's Degrees: Whose Opportunity?

    ERIC Educational Resources Information Center

    Evans, Carol

    2009-01-01

    This study offers a small, highly contextualized counter-example to several recent large-scale analyses depicting Latino underachievement in higher education (R. Fry, 2002; J. Immerwahr, 2003; S. Miller & E. Garcia, 2004; W. Swail, A. Cabrera, & C. Lee, 2004; W. S. Swail, K. E. Redd, & L. W. Perna, 2003). The purpose is to analyze results from a…

  11. Higher Education Alumni Associations and Political Advocacy

    ERIC Educational Resources Information Center

    Buchli, Richard N.

    2015-01-01

    Political advocacy is comprised of speaking on the behalf of a cause or participating as part of a political action group (Weerts, Cabrera, & Sanford, 2010). Because state financial support for public higher education has not been maintained at previous levels, higher education (HE) institutions have been recruiting alumni in an attempt to win…

  12. A note on static dyonic diholes

    NASA Astrophysics Data System (ADS)

    García-Compeán, H.; Manko, V. S.

    2015-09-01

    In this brief note we argue that a dyonic generalization of the Emparan-Teo dihole solution is described by a static diagonal metric and therefore, contrary to the claim made in a recent paper by Cabrera-Munguia et al., does not involve any "non-vanishing global angular momentum" and rotating charges.

  13. A Study of a Developmental Reading Class for Hispanic Males at a Texas University

    ERIC Educational Resources Information Center

    McMullin, Ivy Lee, II.

    2012-01-01

    Though developmental education has long been part of American post-secondary education, reliable evidence of its benefits, especially for ethnic minorities in reading, is lacking (Swail, Cabrera, Lee, & Williams, 2005). Developmental education has costs, however, in added tuition, time-to-completion, and discouragement (Bailey, 2009). Since…

  14. 77 FR 50457 - Secretary's Advisory Committee on Animal Health; Intent To Renew and Request for Nominations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-21

    ... for nominations for membership was published \\1\\ in the Federal Register on May 24, 2012 (77 FR 30993... CONTACT: Mrs. R.J. Cabrera, Designated Federal Official, VS, APHIS, 4700 River Road Unit 35, Riverdale, MD 20737-1231; (301) 8513478 (or 800-877-8339 for the hearing impaired), email:...

  15. Latino Males Degree Aspirations in Community College: A Qualitative Study

    ERIC Educational Resources Information Center

    Dorame, Francisco

    2012-01-01

    Latino males are the least likely to attend, persist, and attain a baccalaureate degree compared to other male groups in higher education. Moreover, they tend to have the lowest degree aspirations of any major race or ethnic group (Saenz & Ponjuan, 2009; Driscoll, 2007; Swail, Cabrera, & Lee, 2004; Laanan, 2000; Kao & Tienda, 1998). To…

  16. Career Decision-Making Self-Efficacy and an Integrated Model of Student Persistence.

    ERIC Educational Resources Information Center

    Sandler, Martin E.

    In response to the extraordinarily diverse adult population in college today, a new structural equation model adapted from Cabrera et al. (1993) integrated model of student retention was identified with the addition of two variables: career decision-making self-efficacy (CDMSE) and financial difficulty. The study examined the persistence/attrition…

  17. Using Scholarship Management Research to Optimize the Impact of Scholarship Funds

    ERIC Educational Resources Information Center

    James, Glenn W.; Mahajan, Shubhada S.

    2004-01-01

    Scholarship aid continues to be crucially important in attracting and retaining students in higher education institutions (Abrahamson & Hossler, 1990; Cabrera, Nora, & Castaneda, 1992; Paulsen & St. John, 1997; Schuh, 2000; St. John, 1992; St. John et al., 1994; Terkla, 1985). Although the general concept and effect of financial assistance is…

  18. The Depiction of Significant Others in Tinto's "Rites of Passage": A Reconceptualization of the Influence of Family and Community in the Persistence Process.

    ERIC Educational Resources Information Center

    Nora, Amaury

    2002-01-01

    Theorizes about interrelations between "rites of passage" in Tinto's (1993) Student Integration Model, and support from significant others in Nora and Cabrera's (1996) Student Adjustment Model. Depicts how both sets of factors impact social and academic experiences and integration, commitment levels to attainment of an educational goal and to an…

  19. A Structural Model of Student Integration, Finances, Behavior, and Career Development: An Elaborated Framework of Attitudes and Persistence. ASHE Annual Meeting Paper.

    ERIC Educational Resources Information Center

    Sandler, Martin E.

    As a response to the problems of nontraditional student attrition at two-year and four-year urban colleges, this paper introduces the constructs of career decision-making self-efficacy, perceived stress, and financial difficulty into a model built on the synthesis of Cabrera (1993). A questionnaire was administered to adult nontraditional (age 24…

  20. 75 FR 71431 - Clean Water Act Section 303(d): Availability of List Decisions Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-23

    ... Register notice that published on November 9, 2010 at 75 FR 68783 announcing the availability of EPA...: Comments on the proposed decisions should be sent to Valentina Cabrera Stagno or Dave Guiliano, Water... 94105, telephone (415) 972-3434 or (415) 947-4133, facsimile (415) 947-3537, e-mail...

  1. Sense of Belonging and Persistence in White and African American First-Year Students

    ERIC Educational Resources Information Center

    Hausmann, Leslie R. M.; Ye, Feifei; Schofield, Janet Ward; Woods, Rochelle L.

    2009-01-01

    The authors argue for the inclusion of students' subjective sense of belonging in an integrated model of student persistence (Cabrera et al., J Higher Educ 64:123-139, 1993). The effects of sense of belonging and a simple intervention designed to increase sense of belonging are tested in the context of this model. The intervention increased sense…

  2. Career Decision-Making Self-Efficacy, Perceived Stress, and an Integrated Model of Student Persistence: A Structural Model of Finances, Attitudes, Behavior, and Career Development.

    ERIC Educational Resources Information Center

    Sandler, Martin E.

    2000-01-01

    Examined the persistence of students (n=937), 24 years of age or older, studying in two- and four-year degree programs by combining data from a survey questionnaire and institutional records. The structural equation model of Cabrera et al. (1993) was adapted for this older population, with identification of three additional variables: career…

  3. Understanding Men's Prenatal Experience and the Father Involvement Connection: Assessing Baby Steps

    ERIC Educational Resources Information Center

    Marsiglio, William

    2008-01-01

    Cabrera, Fagan, and Farrie's research provides a useful springboard to encourage scholars to think broadly and productively about theoretical, substantive, methodological, and social intervention issues related to men's prenatal experiences, transitional life course events, and subsequent engagement with their young children. To their credit, the…

  4. Pleistocene history of Iberomys, an endangered endemic rodent from southwestern Europe.

    PubMed

    Cuenca-Bescós, Gloria; López-García, Juan Manuel; Galindo-Pellicena, María Angeles; García-Perea, Rosa; Gisbert, Julio; Rofes, Juan; Ventura, Jacint

    2014-08-01

    The extant Cabrera's vole, Microtus cabrerae, differs in morphology and evolutionary history from the other species of Microtus. This arvicoline has unique derived features in the cranium, mandible and dentition. Probably its most conspicuous features are its large size, the high skull in lateral view, the long and distally broad nasals, and the triangle shape of the anteroconid complex, with a marked labio-lingual asymmetry of the occlusal surface of the first lower molars. In this study, we propose a phylogenetic lineage that includes Cabrera's vole in what until now has been the Microtus subgenus Iberomys. Paleontological information and several life history traits support the elevation of Iberomys to the rank of genus. Genus Iberomys comprises species that have appeared in succession during the Quaternary: in the Early Pleistocene, the extinct I. huescarensis in the Middle Pleistocene, the extinct I. mediterraneus and in the Late Pleistocene, the extant I. cabrerae. Interestingly, the extant species shows several biological singularities, such as multiple polymorphic copies of the SRY male-specific gene in both males and females, and the lowest basal metabolic rate in relation to weight among arvicoline species. Likewise, its habitat requirement is unique among the Iberian arvicolines. Accordingly, the biological and paleontological data that we present in this work support the elevation of its taxonomic rank to that of genus. This study also suggests a modification of nomenclature: Microtus (Iberomys) brecciensis is replaced with I. mediterraneus and the common name of the extant M. (I.) cabrerae changed from 'topillo' to 'iberon' to improve conservation and protection actions. PMID:25236417

  5. The behavioral response of larval amphibians (Ranidae) to threats from predators and parasites.

    PubMed

    Szuroczki, Dorina; Richardson, Jean M L

    2012-01-01

    Organisms are exposed to strong selective pressures from several sources, including predators and pathogens. Response to such interacting selective pressures may vary among species that differ in life history and ecology in predictable ways. We consider the impact of multiple enemies (fish predators and trematode parasites) on the behavior of larvae of three anuran species (Lithobates (=Rana) sylvaticus, L. clamitans and L. catesbeianus). We show that the three ranid species differ in response to the trade-off imposed by the simultaneous presence of fish predators and trematode parasites in the environment. Two more permanent pond breeders (L. clamitans and L. catesbeianus), which commonly encounter parasites and fish, increased activity when in the combined presence of parasites and a fish predator, resulting in a relatively lower parasite encystment rate. In contrast, the temporary pond breeder (L. sylvaticus), which does not commonly encounter fish in the wild, decreased activity in the combined presence of a fish predator and parasites similar to when only the predator was present. For L. sylvaticus, this suggests that the presence of an unknown predator poses a greater threat than parasites. Further, the presence of fish along with parasites increased the susceptibility of both L. sylvaticus and L. clamitans to trematode infection, whereas parasite infection in L. catesbeianus was unaffected by the presence of fish. Unpalatability to fish may allow some species to respond more freely to attacking parasites in the presence of fish. The results from this study highlight the importance of considering multiple selective pressures faced by organisms and how this shapes their behavior.

  6. Electron stimulated oxidation of silicon surfaces

    SciTech Connect

    Munoz, M.C.; Sacedon, J.L.

    1981-04-15

    Experimental evidence of electron stimulated oxidation (ESO) has been given for Si(111) 7 x 7 surface. In a first stage, the oxide thickness as a function of time shows a linear relationship; in a second stage, the growth rate quickly decreases and a pressure dependent saturation oxide thickness is reached. During the oxidation process an electrical potential does exist across the oxide, as is required in the Cabrera--Mott theory. The linear kinetics and the electrical potential are shown to be explicable in terms of a modified coupled-current approach based on the Cabrera--Mott theory, provided a semiphenomenological pressure dependent parameter is included. This represents a contribution of the surface reaction to the transport equation. The saturation has been explained as due to the decrease of the negative surface charge (donor levels) which produces a decrease of the electron current.

  7. Growth kinetics of the (001) face of TGS below the ferroelectric transition temperature

    NASA Technical Reports Server (NTRS)

    Reiss, D. A.; Kroes, R. L.; Anderson, E. E.

    1987-01-01

    The growth rates of the (001) face of triglycine sulfate (TGS) from aqueous solutions were measured at 33.55 C in an apparatus which produced a laminar flow of solution past the crystal. The data of growth rate as a function of relative supersaturation were compared with the results of two well-known models: the Burton-Cabrera-Frank (1951) surface diffusion model and the birth-and-spreading growth model. Both models produced good fits to the growth rate data. However, on the basis of the qualitative aspects of the experimentally-observed growth, it is suggested that the correct growth model for these crystals is the Burton-Cabrera-Frank model.

  8. In-Situ Radiological Surveys to Address Nuclear Criticality Safety Requirements During Remediation Activities at the Shallow Land Disposal Area, Armstrong County, Pennsylvania - 12268

    SciTech Connect

    Norris, Phillip; Mihalo, Mark; Eberlin, John; Lambert, Mike; Matthews, Brian

    2012-07-01

    Cabrera Services Inc. (CABRERA) is the remedial contractor for the Shallow Land Disposal Area (SLDA) Site in Armstrong County Pennsylvania, a United States (US) Army Corps of Engineers - Buffalo District (USACE) contract. The remediation is being completed under the USACE's Formerly Utilized Sites Remedial Action Program (FUSRAP) which was established to identify, investigate, and clean up or control sites previously used by the Atomic Energy Commission (AEC) and its predecessor, the Manhattan Engineer District (MED). As part of the management of the FUSRAP, the USACE is overseeing investigation and remediation of radiological contamination at the SLDA Site in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), 42 US Code (USC), Section 9601 et. seq, as amended and, the National Oil and Hazardous Substance Pollution Contingency Plan (NCP), Title 40 of the Code of Federal Regulations (CFR) Section 300.430(f) (2). The objective of this project is to clean up radioactive waste at SLDA. The radioactive waste contains special nuclear material (SNM), primarily U-235, in 10 burial trenches, Cabrera duties include processing, packaging and transporting the waste to an offsite disposal facility in accordance with the selected remedial alternative as defined in the Final Record of Decision (USACE, 2007). Of particular importance during the remediation is the need to address nuclear criticality safety (NCS) controls for the safe exhumation and management of waste containing fissile materials. The partnership between Cabrera Services, Inc. and Measutronics Corporation led to the development of a valuable survey tool and operating procedure that are essential components of the SLDA Criticality Safety and Material Control and Accountability programs. Using proven existing technologies in the design and manufacture of the Mobile Survey Cart, the continued deployment of the Cart will allow for an efficient and reliable methodology to

  9. Hierarchical spatial segregation of two Mediterranean vole species: the role of patch-network structure and matrix composition.

    PubMed

    Pita, Ricardo; Lambin, Xavier; Mira, António; Beja, Pedro

    2016-09-01

    According to ecological theory, the coexistence of competitors in patchy environments may be facilitated by hierarchical spatial segregation along axes of environmental variation, but empirical evidence is limited. Cabrera and water voles show a metapopulation-like structure in Mediterranean farmland, where they are known to segregate along space, habitat, and time axes within habitat patches. Here, we assess whether segregation also occurs among and within landscapes, and how this is influenced by patch-network and matrix composition. We surveyed 75 landscapes, each covering 78 ha, where we mapped all habitat patches potentially suitable for Cabrera and water voles, and the area effectively occupied by each species (extent of occupancy). The relatively large water vole tended to be the sole occupant of landscapes with high habitat amount but relatively low patch density (i.e., with a few large patches), and with a predominantly agricultural matrix, whereas landscapes with high patch density (i.e., many small patches) and low agricultural cover, tended to be occupied exclusively by the small Cabrera vole. The two species tended to co-occur in landscapes with intermediate patch-network and matrix characteristics, though their extents of occurrence were negatively correlated after controlling for environmental effects. In combination with our previous studies on the Cabrera-water vole system, these findings illustrated empirically the occurrence of hierarchical spatial segregation, ranging from within-patches to among-landscapes. Overall, our study suggests that recognizing the hierarchical nature of spatial segregation patterns and their major environmental drivers should enhance our understanding of species coexistence in patchy environments. PMID:27167226

  10. Assessing habitat differentiation between coexisting species: The role of spatial scale

    NASA Astrophysics Data System (ADS)

    Pita, Ricardo; Mira, António; Beja, Pedro

    2011-03-01

    Although the importance of spatial scale for understanding habitat selection patterns and processes has long been recognized, little is known about its impact on the identification of habitat differentiation between sympatric species, despite its likely utility in assessing niche partitioning and thus explaining species coexistence. Here we used radio-telemetry data to examine seasonal habitat selection and differentiation by Cabrera ( n = 28) and water voles ( n = 29) within habitat patches in a highly fragmented landscape, across spatial extents and resolutions. Habitat selection was found for both species at the home-range and core-area scales, tending to be strongest for water and Cabrera voles at coarse and fine spatial resolutions, respectively. Water voles showed higher preference for humid sedge/rush and reed habitats across seasons and spatial scales. Cabrera voles consistently selected tall grass and shrub habitats during the wet season, whereas dry season preference was higher for sedge/rush and tall grass at fine and coarse spatial resolutions, respectively. Niche overlap was highest during the dry season, lowest at the core-area scale, and increased with spatial resolution. These patterns likely reflected the fine-scale, seasonal habitat preferences of the Cabrera vole, which during the dry season increased the use of small sedge/rush patches embedded in larger tall grass meadows, thereby bringing it in closer contact to the humid habitats selected at coarse spatial resolutions by the water vole throughout the year. Overall, this study suggests that spatial scale may critically influence the perception of habitat differentiation between coexisting species.

  11. Potential respiration estimated by electron transport system activity in deep-sea suprabenthic crustaceans off Balearic Islands (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Herrera, A.; Gómez, M.; Packard, T. T.; Reglero, P.; Blanco, E.; Barberá-Cebrián, C.

    2014-10-01

    ETS is an acronym for the activity of the respiratory electron transport system; the ETS assay is a biochemical method for estimating the “potential” respiration (Φ). We apply this technique to suprabenthic species captured at three depths (250 m, 650 m and 850 m) in two different locations: Cabrera (Algerian subbasin) and Sóller (Balearic subbasin) during the IDEADOS survey during summer 2010. The aim of this study was to compare specific Φ between areas and between three depths to identify differences in the suprabenthos physiological state related to nutritional conditions. Specific Φ, expressed in unit of μl O2 h- 1 mg prot- 1 was not significantly different between species. Mean values were for the decapods: Plesionika heterocarpus, 8.4 ± 7.9; Gennadas elegans, 8.3 ± 2.9; and Sergestes arcticus 7.3 ± 4.6. Within the euphausiids specific Φ averaged 6.5 ± 4.2 for Thysanopoda aequalis and 9.8 ± 5.1 for Meganyctiphanes norvegica; while for the mysids it ranged from 7.7 ± 4.4 for Boreomysis arctica and 2.1 ± 0.6 for Eucopia unguiculata. The comparison of specific potential respiration (Φ), with the pooling of the data of all the species, showed differences between the two locations, being higher in Cabrera. However, no significant differences between the different depths of each locality were found. The slope of the log Φ-log biomass plot was 0.93 ± 0.09 for Cabrera and 0.64 ± 0.11 in Sóller. We interpret these differences as indicating that the suprabenthos in the Cabrera area, as compared to the Sóller area, has been well-nourished.

  12. Blood parasites of amphibians from Algonquin Park, Ontario.

    PubMed

    Barta, J R; Desser, S S

    1984-07-01

    During a 5 wk period beginning May 25, 1983, 329 amphibians, which included specimens of Rana catesbeiana Shaw, Rana clamitans Latreille, Rana septentrionalis Baird, Rana sylvatica LeConte, Hyla crucifer Wied, Bufo americanus Holbrook, and Plethodon cinereus Green, from Lake Sasajewun, Algonquin Park, Ontario, Canada were examined for blood parasites. The prevalences of species of Trypanosoma, Haemogregarina, Lankesterella, Babesiasoma, and Thrombocytozoons in these amphibians were determined. Two species of microfilaria (probably Foleyella spp.) and two intraerythrocytic forms, inclusions of an icosahedral cytoplasmic DNA virus (ICDV) and groups of rickettsial organisms, were also observed. The following are new host records: Trypanosoma ranarum (Lankester, 1871) in B. americanus; Trypanosoma ranarum (Lankester, 1871) in R. sylvatica; Trypanosoma pipientis Diamond, 1950, Babesiasoma stableri Schmittner and McGhee, 1961 and Thrombocytozoons ranarum Tchacarof, 1963 in R. septentrionalis. The aquatic frogs generally showed a much higher prevalence of infection with blood parasites than the terrestrial frogs, toads and salamanders, which is suggestive of an aquatic vector. The leech Batracobdella picta Verrill, 1872, which was found on many of the aquatic frogs, is the most likely vector in the study area. Also, an increasing prevalence of parasites was noted with increasing sizes (ages) of Rana clamitans and R. catesbeiana suggesting that longer exposure to water makes these species more likely to acquire blood parasites. The presence of Trypanosoma ranarum in B. americanus appeared to coincide with their attainment of sexual maturity. PMID:6492319

  13. Role of sediments in modifying the toxicity of two Roundup formulations to six species of larval anurans.

    PubMed

    Fuentes, Latice; Moore, Lindsay J; Rodgers, John H; Bowerman, William W; Yarrow, Gregory K; Chao, Wayne Y

    2014-11-01

    The role of sediment in modifying the toxicity of the original formulation of Roundup® and Roundup WeatherMAX® was examined in aqueous laboratory tests. Six species of anurans (Bufo fowleri, Hyla chrysoscelis, Rana catesbeiana, Rana clamitans, Rana sphenocephala, and Rana pipiens) were exposed at Gosner stage 25 to concentrations of the 2 herbicide formulations in 96-h, static, nonrenewal experiments in the presence and absence of sediment. All species tested had lower median lethal concentration values in water-only exposures of both formulations compared with exposures with sediment. Sediment significantly altered the potency slopes in all tests with the exceptions of H. chrysoscelis and R. clamitans when exposed to the original formulation of Roundup and H. chrysoscelis and R. sphenocephala when exposed to Roundup WeatherMAX. Thresholds were significantly different in all tests, including those in which potency slopes did not differ. Based on water-sediment exposures of the original formulation of Roundup, all 6 species tested had a margin of safety when compared with the predicted environmental concentration of the highest label application rate. Of the 6 species, 5 had a margin of safety when exposed to Roundup WeatherMAX. During incidental exposures in the field, sediments and organic matter present in aquatic systems provide significant sources of environmental ligands. If used according to label instructions, both herbicides should pose minimal risk to anuran amphibians in actual field applications. Environ Toxicol Chem 2014;33:2616-2620. © 2014 SETAC.

  14. Understanding the net effects of pesticides on amphibian trematode infections.

    PubMed

    Rohr, Jason R; Raffel, Thomas R; Sessions, Stanley K; Hudson, Peter J

    2008-10-01

    Anthropogenic factors can have simultaneous positive and negative effects on parasite transmission, and thus it is important to quantify their net effects on disease risk. Net effects will be a product of changes in the survival and traits (e.g., susceptibility, infectivity) of both hosts and parasites. In separate laboratory experiments, we exposed cercariae of the trematode Echinostoma trivolvis, and its first and second intermediate hosts, snails (Planorbella trivolvis) and green frog tadpoles (Rana clamitans), respectively, to one of four common pesticides (atrazine, glyphosate, carbaryl, and malathion) at standardized, ecologically relevant concentrations (201.0, 3700.0, 33.5, and 9.6 microg/L, respectively). We measured effects of pesticide exposure on six mechanisms important to this host-parasite interaction: (1) survival of E. trivolvis cercariae over 26 hours, (2) tadpole survival over two weeks, (3) snail survival over four weeks, (4) snail growth and fecundity, (5) cercarial infectivity, and (6) tadpole susceptibility to a fixed number of cercariae. Pesticides, in general, caused significantly greater mortality of E. trivolvis cercariae than did control treatments, but atrazine was the lone chemical to significantly reduce cercarial survival (LC50 value = 267 mg/L) and then only at concentrations greater than commonly found in aquatic ecosystems (> or =200 microg/L). None of the pesticides significantly enhanced E. trivolvis virulence, decreased tadpole survival, or reduced snail survival, growth, or fecundity. Sublethal exposure of the cercariae to the pesticides (4 h) did not significantly affect trematode encystment in R. clamitans. In contrast, sublethal exposure of R. clamitans to each of the four pesticides increased their susceptibility as measured by the percentage of cercariae that encysted. The reduction in exposure to trematodes due to pesticide-induced cercarial mortality (a density-mediated effect) was smaller than the pesticide

  15. Hydrodynamic comparison between the north and south of Mallorca Island

    NASA Astrophysics Data System (ADS)

    Amores, Angel; Monserrat, Sebastià

    2014-10-01

    A hydrodynamic comparison between two zones of fishing interest, one located to the north and the other to the south of Mallorca Island (Balearic Islands, Western Mediterranean) was done. The comparison was conducted using the data from two moorings, one placed in the middle of the Balearic Current, in the Balearic subbasin (herein, Sóller) and the other in the Mallorca Channel, near the Algerian subbasin (called Cabrera). The instruments moored, continuously recorded the temperature, salinity and currents at different depths, for over 15 months. The data analysis suggests that Sóller is hydrodynamically more active than Cabrera, at least during the time of recording the measurements. The mean currents were higher at Sóller than at Cabrera at all depths, also showing greater maximum speeds and variability. In addition, the presence of more mesoscale eddies in Sóller became evident from the altimetry data. These eddies were not only significantly more energetic near the surface, they also generally reached to greater depths, affecting the velocities of the seabed currents. Subsequent to each significant eddy episode, strong changes in temperature and/or salinity were observed, along the entire water column. Spectral analysis revealed the presence of high frequency oscillations with periods of a few hours. One energy peak, with a period around 3.7 h, was observed at both locations, probably related to trapped waves around Mallorca or the Balearic Islands, while others (3 h and 2 h) were reflected only in Sóller, suggesting they could be associated with some standing resonance waves between the Iberian Peninsula and Mallorca.

  16. Heterogeneous extension and the role of transfer faults in the development of the southeastern Betic basins (SE Spain)

    NASA Astrophysics Data System (ADS)

    Giaconia, F.; Booth-Rea, G.; Martínez-Martínez, J. M.; Azañón, J. M.; Storti, F.; Artoni, A.

    2014-12-01

    Large strike-slip faults in the eastern Betics are interpreted to have developed in a transcurrent setting in response to 4-6 mm/yr of Africa-Iberia NW-SE convergence. However, here we show that some of these faults are transfer faults accommodating heterogeneous late Miocene extension. The North Cabrera dextral fault and other E-W to NE-SW strike-slip faults in the Sorbas basin were transfer faults produced under SW-NE extension. These faults together with related normal faults form the main boundaries of two sedimentary depocenters active between the Serravallian and the Tortonian. The older North Cabrera depocenter extended between the Serravallian and the early Tortonian (approximately 13.8 to 9 Ma), while the younger Gacía depocenter formed in response to late Tortonian extension (approximately 9 to 7.5 Ma). The latter formed to the west of the North Cabrera depocenter by a listric fan of normal faults with SW directed transport that are linked by dextral and sinistral transfer fault segments. These faults root on a low-angle detachment cutting into the exhumed high-pressure Nevado-Filabride complex rocks at ~0.8 km depth. The present work reveals that (1) this extension was partially coeval with and kinematically linked to sinistral displacement along the Carboneras fault farther south in the Níjar basin; (2) this westward directed extension produced elongated core complexes and tilted blocks to the north of the Carboneras fault and magmatic accretion upon thinned continental crust to the south, probably in response to slab tearing or detachment and associated edge delamination of the Iberian continental lithospheric mantle beneath the Betics.

  17. Possible Role of Fish and Frogs as Paratenic Hosts of Dracunculus medinensis, Chad

    PubMed Central

    Yabsley, Michael J.; Zirimwabagabo, Hubert; Bishop, Henry; Cleveland, Christopher A.; Maerz, John C.; Bringolf, Robert; Ruiz-Tiben, Ernesto

    2016-01-01

    Copepods infected with Dracunculus medinensis larvae collected from infected dogs in Chad were fed to 2 species of fish and tadpoles. Although they readily ingested copepods, neither species of fish, Nile tilapia (Oreochromis niloticus) nor fathead minnow (Pimephalis promelas), were found to harbor Dracunculus larvae when examined 2–3 weeks later. Tadpoles ingested copepods much more slowly; however, upon examination at the same time interval, tadpoles of green frogs (Lithobates [Rana] clamitans) were found to harbor small numbers of Dracunculus larvae. Two ferrets (Mustela putorius furo) were fed fish or tadpoles that had been exposed to infected copepods. Only the ferret fed tadpoles harbored developing Dracunculus larvae at necropsy 70–80 days postexposure. These observations confirm that D. medinensis, like other species in the genus Dracunculus, can readily survive and remain infective in potential paratenic hosts, especially tadpoles. PMID:27434418

  18. Possible Role of Fish and Frogs as Paratenic Hosts of Dracunculus medinensis, Chad.

    PubMed

    Eberhard, Mark L; Yabsley, Michael J; Zirimwabagabo, Hubert; Bishop, Henry; Cleveland, Christopher A; Maerz, John C; Bringolf, Robert; Ruiz-Tiben, Ernesto

    2016-08-01

    Copepods infected with Dracunculus medinensis larvae collected from infected dogs in Chad were fed to 2 species of fish and tadpoles. Although they readily ingested copepods, neither species of fish, Nile tilapia (Oreochromis niloticus) nor fathead minnow (Pimephalis promelas), were found to harbor Dracunculus larvae when examined 2-3 weeks later. Tadpoles ingested copepods much more slowly; however, upon examination at the same time interval, tadpoles of green frogs (Lithobates [Rana] clamitans) were found to harbor small numbers of Dracunculus larvae. Two ferrets (Mustela putorius furo) were fed fish or tadpoles that had been exposed to infected copepods. Only the ferret fed tadpoles harbored developing Dracunculus larvae at necropsy 70-80 days postexposure. These observations confirm that D. medinensis, like other species in the genus Dracunculus, can readily survive and remain infective in potential paratenic hosts, especially tadpoles. PMID:27434418

  19. Formation of micropipes in SiC under kinetic aspects

    NASA Astrophysics Data System (ADS)

    Heindl, J.; Dorsch, W.; Eckstein, R.; Hofmann, D.; Marek, T.; Müller, St. G.; Strunk, H. P.; Winnacker, A.

    1997-08-01

    We measure the radii of micropipes at the {0001} surface of modified Lely grown 6H-SiC and the total step height of the accompanying growth spirals by using atomic force microscopy. The micropipes lie in the center of spirals; the total step height ranges between one and 19 unit-cells (1.5-28.5 nm). We fit Frank's theory of hollow core dislocations as modified with regard to kinetic effects by Cabrera and Levine to these experimental results and obtain values for surface energy and supersaturation near the emergence point of the micropipe.

  20. New species, new combinations and synonymies of Neotropical Galerucini (Coleoptera, Chrysomelidae, Galerucinae).

    PubMed

    Moura, Luciano De A

    2016-01-12

    New species of Neotropical Galerucini are described and illustrated: Caraguata onca sp. nov., from southern Brazil (Rio Grande do Sul) and northern Argentina (Chaco); and Yingaresca cabrerae sp. nov., from Argentina (Misiones). Galerucella transversicollis Jacoby, 1886 is integrated to Yingaresca Bechyné. Two species originally described in Ophraella Wilcox are also transferred to Yingaresca: Yingaresca limonensis (Bechyné, 1997) comb. nov. and Yingaresca magdalia (Bechyné, 1997) comb. nov. Metrogaleruca obscura paraensis (Bechyné & Bechyné, 1961) is considered a synonym of Metrogaleruca obscura (Degeer, 1775).

  1. New species, new combinations and synonymies of Neotropical Galerucini (Coleoptera, Chrysomelidae, Galerucinae).

    PubMed

    Moura, Luciano De A

    2016-01-01

    New species of Neotropical Galerucini are described and illustrated: Caraguata onca sp. nov., from southern Brazil (Rio Grande do Sul) and northern Argentina (Chaco); and Yingaresca cabrerae sp. nov., from Argentina (Misiones). Galerucella transversicollis Jacoby, 1886 is integrated to Yingaresca Bechyné. Two species originally described in Ophraella Wilcox are also transferred to Yingaresca: Yingaresca limonensis (Bechyné, 1997) comb. nov. and Yingaresca magdalia (Bechyné, 1997) comb. nov. Metrogaleruca obscura paraensis (Bechyné & Bechyné, 1961) is considered a synonym of Metrogaleruca obscura (Degeer, 1775). PMID:27395530

  2. Chemical composition, antifungal and herbicidal effects of essential oil isolated from Chersodoma Argentina (Asteraceae).

    PubMed

    Alarcón, Rosana; Ocampos, Soledad; Pacciaroni, Adriana; Sosa, Virginia

    2012-01-01

    Analysis of the hydrodistilled essential oil of the aerial parts of Chersodoma argentina Cabrera by GC-MS and NMR spectroscopy revealed that over 80% consisted of monoterpene hydrocarbons such as alpha-thujene, alpha-pinene and beta-pinene. Contact and headspace volatile exposure assays of the essential oil demonstrated antifungal activity against Sclerotinia sclerotiorum, Sclerotium rolfsii and Rhizoctonia solani with the contact assay showing greater activity than the headspace assay. Herbicidal activity was shown by reduced root growth of Allium porrum, Solanum lycopersicon and Sorghum halepense in both assays.

  3. In situ atomic force microscopy of layer-by-layer crystal growth and key growth concepts

    NASA Astrophysics Data System (ADS)

    Rashkovich, L. N.; de Yoreo, J. J.; Orme, C. A.; Chernov, A. A.

    2006-12-01

    Contradictions that have been found recently between the representations of classical theory and experiments on crystal growth from solutions are considered. Experimental data show that the density of kinks is low in many cases as a result of the low rate of their fluctuation generation, the Gibbs-Thomson law is not always applicable in these cases, and there is inconsistency with the Cabrera-Vermilyea model. The theory of growth of non-Kossel crystals, which is to be developed, is illustrated by the analysis of the experimental dependence of the growth rate on the solution stoichiometry.

  4. Chemical composition, antifungal and herbicidal effects of essential oil isolated from Chersodoma Argentina (Asteraceae).

    PubMed

    Alarcón, Rosana; Ocampos, Soledad; Pacciaroni, Adriana; Sosa, Virginia

    2012-01-01

    Analysis of the hydrodistilled essential oil of the aerial parts of Chersodoma argentina Cabrera by GC-MS and NMR spectroscopy revealed that over 80% consisted of monoterpene hydrocarbons such as alpha-thujene, alpha-pinene and beta-pinene. Contact and headspace volatile exposure assays of the essential oil demonstrated antifungal activity against Sclerotinia sclerotiorum, Sclerotium rolfsii and Rhizoctonia solani with the contact assay showing greater activity than the headspace assay. Herbicidal activity was shown by reduced root growth of Allium porrum, Solanum lycopersicon and Sorghum halepense in both assays. PMID:22428265

  5. Phase-field modeling of epitaxial growth in stochastic systems with interacting adsorbate

    NASA Astrophysics Data System (ADS)

    Kharchenko, Dmitrii O.; Kharchenko, Vasyl O.; Lysenko, Irina O.

    2011-04-01

    We study the epitaxial growth of pyramidal patterns in stochastic systems with interacting adsorbate within the framework of the phase-field approach based on the Burton-Cabrera-Frank model. Considering the statistical criteria of pattern formation, it is shown that the system dynamics is governed by the interaction strength of adatoms and the noise intensity of the total flux fluctuations. We have shown that the noise action can crucially change the processes of pyramidal pattern formation. The scaling behavior of the height-height correlation function is discussed.

  6. Estimating hyperconcentrated flow discharge

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-02-01

    Determining flow discharge in torrential mountain floods can help in managing flood risk. However, standard methods of estimating discharge have significant uncertainties. To reduce these uncertainties, Bodoque et al. developed an iterative methodological approach to flow estimation based on a method known as the critical depth method along with paleoflood evidence. They applied the method to study a flash flood that occurred on 17 December 1997 in the Arroyo Cabrera catchment in central Spain. This large flow event, triggered by torrential rains, was complex and included hyperconcentrated flows, which are flows of water mixed with significant amounts of sediment.

  7. Phase-field model for reconstructed stepped surface

    NASA Astrophysics Data System (ADS)

    Nakamura, Kanna; Margetis, Dionisios

    2013-07-01

    We formulate a phase-field, or diffuse-interface, model for the evolution of stepped surfaces under surface diffusion in the presence of distinct material parameters across nanoscale terraces. In the sharp-interface limit, our model reduces to a Burton-Cabrera-Frank (BCF)-type theory for the motion of noninteracting steps separating inhomogeneous terraces. This setting aims to capture features of reconstructed semiconductor, e.g., Si surfaces below the roughening transition. Our work forms an extension of the phase-field construction by Hu [Physica DPDNPDT0167-278910.1016/j.physd.2011.09.004 241, 77 (2012)].

  8. Stimulated oxidation of metals (laser, electric field, etc.): Comparative studies

    NASA Astrophysics Data System (ADS)

    Nánai, László; Füle, Miklós

    2014-11-01

    In this report we demonstrate the importance of metal oxides, e.g. thin films and nanostructures, in modern science and technology. The basic laws of oxide thickness on base of diffusion of specimens versus time in different circumstances (Cabrera-Mott and Wagner laws) under the influence of external fields, e.g. electromagnetic field, static electric and magnetic field, are demonstrated. We give experimental results for various metal oxide layers over a wide range of different metals. Theoretical explanations are provided as well for the most reliable circumstances.

  9. Laboratory and field exposure of two species of juvenile amphibians to a glyphosate-based herbicide and Batrachochytrium dendrobatidis.

    PubMed

    Edge, Christopher B; Gahl, Megan K; Thompson, Dean G; Houlahan, Jeff E

    2013-02-01

    Herbicides are commonly used in agriculture and silviculture to reduce interspecific competition among plants and thereby enhance crop growth, quality, and volume. Internationally, formulations of glyphosate-based herbicides are the most widely used herbicides in both these sectors. A large amount of work has focused on the effects of these herbicides on amphibians. Several laboratory and mesocosm studies have demonstrated that various formulations of glyphosate herbicides can be acutely toxic to larval and juvenile amphibians at concentrations at the upper end of environmental realism. However, to date there has been little work done investigating such effects in natural systems, limited work on juvenile amphibians, and only a few studies have investigated interactions with other stressors. We conducted a 16 day field experiment in which juveniles of two amphibian species (Lithobates clamitans and Lithobates pipiens) were exposed to the herbicide Roundup WeatherMax™ at four application rates (0, 2.16, 4.32 and 8.64 kg a.e./ha) to investigate effects on survival, liver somatic index (LSI), body condition, and incidence of disease caused by Batrachochytrium dendrobatidis (Bd). In a separate 16 day laboratory experiment, we exposed juvenile L. clamitans to both the herbicide and Bd. Results of our studies showed that this particular herbicide formulation had no effect on juvenile survival, LSI, body condition, or disease incidence, nor was there an interaction between exposure to herbicide and exposure to the disease in tests which closely mimic real world exposure scenarios. These experiments suggest that Roundup WeatherMax as typically used in agriculture is unlikely to cause significant deleterious effects on juvenile amphibians under real world exposure conditions.

  10. A comparison of acoustic montoring methods for common anurans of the northeastern United States

    USGS Publications Warehouse

    Brauer, Corinne; Donovan, Therese; Mickey, Ruth M.; Katz, Jonathan; Mitchell, Brian R.

    2016-01-01

    Many anuran monitoring programs now include autonomous recording units (ARUs). These devices collect audio data for extended periods of time with little maintenance and at sites where traditional call surveys might be difficult. Additionally, computer software programs have grown increasingly accurate at automatically identifying the calls of species. However, increased automation may cause increased error. We collected 435 min of audio data with 2 types of ARUs at 10 wetland sites in Vermont and New York, USA, from 1 May to 1 July 2010. For each minute, we determined presence or absence of 4 anuran species (Hyla versicolor, Pseudacris crucifer, Anaxyrus americanus, and Lithobates clamitans) using 1) traditional human identification versus 2) computer-mediated identification with software package, Song Scope® (Wildlife Acoustics, Concord, MA). Detections were compared with a data set consisting of verified calls in order to quantify false positive, false negative, true positive, and true negative rates. Multinomial logistic regression analysis revealed a strong (P < 0.001) 3-way interaction between the ARU recorder type, identification method, and focal species, as well as a trend in the main effect of rain (P = 0.059). Overall, human surveyors had the lowest total error rate (<2%) compared with 18–31% total errors with automated methods. Total error rates varied by species, ranging from 4% for A. americanus to 26% for L. clamitans. The presence of rain may reduce false negative rates. For survey minutes where anurans were known to be calling, the odds of a false negative were increased when fewer individuals of the same species were calling.

  11. A simultaneous multiple species acute toxicity test comparing relative sensitivities of six aquatic organisms to HgCl{sub 2}

    SciTech Connect

    McCrary, J.E.; Heagler, M.G.

    1995-12-31

    In the last few years there has been concern in the scientific community about observed declines in some amphibian species. These population declines could be reflecting a global phenomenon due to a general class sensitivity or may be part of a natural cycle. The suggestion of an overall greater sensitivity of amphibians is not supported. Studies show that amphibians, as a class, are neither more or less susceptible than fish to environmental conditions. Mercury has been found to be one of the most toxic of the heavy metals introduced into amphibian breeding waters. Six aquatic species were simultaneously exposed in a comparative acute toxicity test with mercury chloride: three amphibians, Rana catesbeiana (bullfrog), R. clamitans (green frog), and R. sphenocephala (southern leopard frog, formally classified as R. utricularia); two fish, Gambusia affinis (mosquitofish) and Notemigonus crysoleucas (golden shiner); one aquatic aligochaete, Lumbriculus variegatus (aquatic earthworm). The five test concentrations used were 1.4, 3.9, 12.0, 110.0, and 487.0 {micro}g Hg/L respectively. Ten organisms per species were randomly placed into the six test tanks (control and five concentrations), each species in a separate chamber. The resultant LC50-96hr values produced the following rank order: R. sphenocephala, 6.59 {micro}g Hg/L; R. clamitans, 14.7 {micro}g Hg/L; N. crysoleucas, 16.75 {micro}g Hg/L; L. variegatus, 43.72,ug Hg/L; G. affinis, 52.62 {micro}g Hg/L; R. catesbeiana, 63.36 {micro}g Hg/L. No general organism class sensitivity trend, for amphibians, was developed from this data, contrary to the implicit suggestions of some researchers.

  12. A silviculture application of the glyphosate-based herbicide VisionMAX to wetlands has limited direct effects on amphibian larvae.

    PubMed

    Edge, Christopher B; Thompson, Dean G; Hao, Chunyan; Houlahan, Jeff E

    2012-10-01

    Herbicides are commonly used in agriculture and silviculture to reduce interspecific competition among plants and thereby enhance crop growth, quality, and volume. Internationally, glyphosate-based herbicides are the most widely used herbicides in both of these sectors. Laboratory and mesocosm studies have demonstrated that some formulations are toxic to amphibian larvae below concentrations that approximate predicted maximal or "worst-case" exposure scenarios. However, field studies have not found evidence of toxicity at these concentrations. The authors conducted a replicated field experiment involving 10 naturalized wetlands split in half with an impermeable plastic barrier to assess the direct toxicity of a glyphosate formulation commonly used in silviculture (VisionMAX™). The herbicide formulation was applied directly to the surface of one side of each wetland at one of two target aqueous exposure rates (high = 2,880, low = 550 µg acid equivalents [a.e.]/L), and the other side was left as an untreated control. The survival and growth of green frog larvae (Lithobates clamitans) were assessed for two years following herbicide treatment. The herbicide did not have a negative impact on survival or growth of L. clamitans larvae at either treatment level. In fact, mean larval abundance was typically greater in the treated sides than in control sides within the year of herbicide application. These results indicate that typical silviculture use of VisionMAX poses negligible risk to larval amphibians, likely because the combined effects of sorption and degradation in natural wetlands limit the exposure magnitude and duration. PMID:22833320

  13. Delayed stochastic control

    NASA Astrophysics Data System (ADS)

    Hosaka, Tadaaki; Ohira, Toru; Lucian, Christian; Milton, John

    2005-03-01

    Time-delayed feedback control becomes problematic in situations in which the time constant of the system is fast compared to the feedback reaction time. In particular, when perturbations are unpredictable, traditional feedback or feed-forward control schemes can be insufficient. Nonethless a human can balance a stick at their fingertip in the presence of fluctuations that occur on time scales shorter than their neural reaction times. Here we study a simple model of a repulsive delayed random walk and demonstrate that the interplay between noise and delay can transiently stabilize an unstable fixed-point. This observation leads to the concept of ``delayed stochastic control,'' i.e. stabilization of tasks, such as stick balancing at the fingertip, by optimally tuning the noise level with respect to the feedback delay time. References:(1)J.L.Cabrera and J.G.Milton, PRL 89 158702 (2002);(2) T. Ohira and J.G.Milton, PRE 52 3277 (1995);(3)T.Hosaka, T.Ohira, C.Lucian, J.L.Cabrera, and J.G.Milton, Prog. Theor. Phys. (to appear).

  14. Linde FUSRAP Site Remediation: Engineering Challenges and Solutions of Remedial Activities on an Active Industrial Facility - 13506

    SciTech Connect

    Beres, Christopher M.; Fort, E. Joseph; Boyle, James D.

    2013-07-01

    The Linde FUSRAP Site (Linde) is located in Tonawanda, New York at a major research and development facility for Praxair, Inc. (Praxair). Successful remediation activities at Linde combines meeting cleanup objectives of radiological contamination while minimizing impacts to Praxair business operations. The unique use of Praxair's property coupled with an array of active and abandoned utilities poses many engineering and operational challenges; each of which has been overcome during the remedial action at Linde. The U.S. Army Corps of Engineers - Buffalo District (USACE) and CABRERA SERVICES, INC. (CABRERA) have successfully faced engineering challenges such as relocation of an aboveground structure, structural protection of an active water line, and installation of active mechanical, electrical, and communication utilities to perform remediation. As remediation nears completion, continued success of engineering challenges is critical as remaining activities exist in the vicinity of infrastructure essential to business operations; an electrical substation and duct bank providing power throughout the Praxair facility. Emphasis on engineering and operations through final remediation and into site restoration will allow for the safe and successful completion of the project. (authors)

  15. Interaction of O 2 with Pd single crystals in the range 1-150 Torr: Oxygen dissolution and reaction

    NASA Astrophysics Data System (ADS)

    Han, Jinyi; Zemlyanov, Dmitry Y.; Ribeiro, Fabio H.

    2006-07-01

    The interaction of O 2 with Pd(1 1 1), Pd(1 1 0) and Pd(1 0 0) was studied in the pressure range 1-150 Torr by the techniques of temperature programmed decomposition (TPD), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The oxidation of Pd was rate-determined by oxygen diffusion into Pd metal followed by the diffusion into PdO once the bulk oxide layer was formed. The dissolution of oxygen atoms into Pd metal followed the Mott-Cabrera model with diffusion coefficient 10 -16 cm 2 s -1 at 600 K and activation energy of 60-85 kJ mol -1. The bulk oxide phase was formed when a critical oxygen concentration was reached in the near-surface region. The formation of PdO was characterized by a decrease in the oxygen uptake rate, the complete fading of the metallic Pd LEED pattern and an atomic ratio O/Pd of 0.15-0.7 as measured by AES. The diffusion of oxygen through the bulk oxide layer again conformed to the Mott-Cabrera parabolic diffusion law with diffusion coefficient 10 -18 cm 2 s -1 at 600 K and activation energy of 111-116 kJ mol -1. The values for the diffusion coefficient and apparent activation energy increased as the surface atom density of the single crystals increased.

  16. Mountain front migration and drainage captures related to fault segment linkage and growth: The Polopos transpressive fault zone (southeastern Betics, SE Spain)

    NASA Astrophysics Data System (ADS)

    Giaconia, Flavio; Booth-Rea, Guillermo; Martínez-Martínez, José Miguel; Azañón, José Miguel; Pérez-Romero, Joaquín; Villegas, Irene

    2013-01-01

    The Polopos E-W- to ESE-WNW-oriented dextral-reverse fault zone is formed by the North Alhamilla reverse fault and the North and South Gafarillos dextral faults. It is a conjugate fault system of the sinistral NNE-SSW Palomares fault zone, active from the late most Tortonian (≈7 Ma) up to the late Pleistocene (≥70 ky) in the southeastern Betics. The helicoidal geometry of the fault zone permits to shift SE-directed movement along the South Cabrera reverse fault to NW-directed shortening along the North Alhamilla reverse fault via vertical Gafarillos fault segments, in between. Since the Messinian, fault activity migrated southwards forming the South Gafarillos fault and displacing the active fault-related mountain-front from the north to the south of Sierra de Polopos; whilst recent activity of the North Alhamilla reverse fault migrated westwards. The Polopos fault zone determined the differential uplift between the Sierra Alhamilla and the Tabernas-Sorbas basin promoting the middle Pleistocene capture that occurred in the southern margin of the Sorbas basin. Continued tectonic uplift of the Sierra Alhamilla-Polopos and Cabrera anticlinoria and local subsidence associated to the Palomares fault zone in the Vera basin promoted the headward erosion of the Aguas river drainage that captured the Sorbas basin during the late Pleistocene.

  17. Inhibition of growth in solid solution-aqueous solution systems by non-incorporating impurities

    NASA Astrophysics Data System (ADS)

    Pina, Carlos M.

    2011-03-01

    Crystal growth inhibition by non-incorporating impurities has been described and quantified since 1958 by the so-called step pinning model by Cabrera and Vermilyea [1]. In the original model, as well as in its recent improvements by Weaver et al. in 2006 and 2007 [2,3], only the inhibition by the adsorption of impurities on crystal surfaces with fixed compositions is considered. However, most of the crystals found in nature are solid solutions with more or less wide chemical variability. Therefore, in order to provide more realistic models of crystal growth inhibition in natural systems, it is fundamental to study in detail the inhibition of surfaces of solid solutions by non-incorporating impurities. In this paper, the Cabrera-Vermilyea model has been generalised for the case of growth inhibition in solid solution-aqueous solution (SS-AS) systems. This generalisation was made by considering that supersaturation and the physicochemical properties of the solid solutions are functions of the solid composition. The main implication of the model is that a progressive inhibition of growth of a solid solution by increasing the concentration of an adsorbed impurity results in compositional changes on the growing surfaces.

  18. Mesoscopic Impurities Expose a Nucleation-Limited Regime of Crystal Growth

    NASA Astrophysics Data System (ADS)

    Sleutel, Mike; Lutsko, James F.; Maes, Dominique; Van Driessche, Alexander E. S.

    2015-06-01

    Nanoscale self-assembly is naturally subject to impediments at the nanoscale. The recently developed ability to follow processes at the molecular level forces us to resolve older, coarse-grained concepts in terms of their molecular mechanisms. In this Letter, we highlight one such example. We present evidence based on experimental and simulation data that one of the cornerstones of crystal growth theory, the Cabrera-Vermilyea model of step advancement in the presence of impurities, is based on incomplete physics. We demonstrate that the piercing of an impurity fence by elementary steps is not solely determined by the Gibbs-Thomson effect, as assumed by Cabrera-Vermilyea. Our data show that for conditions leading up to growth cessation, step retardation is dominated by the formation of critically sized fluctuations. The growth recovery of steps is counter to what is typically assumed, not instantaneous. Our observations on mesoscopic impurities for lysozyme expose a nucleation-dominated regime of growth that has not been hitherto considered, where the system alternates between zero and near-pure velocity. The time spent by the system in arrest is the nucleation induction time required for the step to amass a supercritical fluctuation that pierces the impurity fence.

  19. Environmental factors controlling particulate mass fluxes on the Mallorca continental slope (Western Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Pasqual, Catalina; Amores, Angel; Flexas, M. Mar; Monserrat, Sebastià; Calafat, Antoni

    2014-10-01

    Settled material recorded by two near bottom sediment traps deployed from November 2009 to February 2011 at northern (Sóller) and southern (Cabrera) slopes of Mallorca Island (Western Mediterranean) is studied with the aim of discerning their possible origin. The total settled particulate mass fluxes (TMF) at Sóller station were found to be, on average, 2.8 times greater than at Cabrera location during the deployment period, although both time series had a similar temporal evolution. It is suggested that wind episodes affecting the entire area were the common forcing, causing a primary production enhancement and being responsible of the similar temporal behavior. The greater sediment amounts collected in Sóller are explained on the basis of two physical mechanisms: 1) a number of successive eddies generated by instabilities of the Balearic Current that are regularly observed on satellite images, some of which have been reported to reach the seabed, thus increasing near bottom velocities and causing sediment resuspension. And 2) bottom trapped waves that are evidenced from a wavelet analysis in Sóller which could affect the TFM by enhancing sediment resuspension or advecting material from the surrounding areas.

  20. The feeding and diet of the deep-sea shrimp Aristeus antennatus off the Balearic Islands (Western Mediterranean): Influence of environmental factors and relationship with the biological cycle

    NASA Astrophysics Data System (ADS)

    Cartes, Joan E.; Papiol, Vanesa; Guijarro, Beatriz

    2008-10-01

    Spatio-temporal variation of feeding intensity and diet in the red shrimp Aristeus antennatus was studied at two locations around the island of Mallorca (Balearic Islands, Western Mediterraean) in August, September, and November 2003, and in February, April and June 2004 at depths between 550 and 750 m. The two areas, with different oceanographic conditions, were respectively located in the northwest (Sóller) and the south (Cabrera) of Mallorca. Off Sóller, feeding intensity of A. antennatus showed a significant increase from February to April and June 2004 in all the three size-classes studied (small shrimps: CL < 30 mm; medium: CL between 30 and 40 mm; large: CL ⩾ 40 mm). Off Cabrera, the highest fullness was recorded in November 2003 among small and medium shrimp, while only large specimens showed patterns similar to that found off Sóller. Off Sóller, the diet of both small (CL < 34 mm) and large (CL ⩾ 34 mm) A. antennatus was mainly influenced by season, with three dietary groups corresponding to August-September 2003, to November 2003/February 2004, and to hauls from April to June 2004. Off Cabrera, hauls (representing diets) were grouped by depth, never by season. The most remarkable seasonal shift in the diet of A. antennatus off Sóller was the increase of mesopelagic prey in April-June relative to other months. In all size categories there was an increase off Sóller in the energy intake of prey ingested from February to June 2004, an increase not found off Cabrera. Degree of digestion of mesopelagic prey indicated nocturnal feeding on mesopelagic fauna. These prey probably have a shallower depth distribution at night than found in our daylight sampling, and possible migratory movements among prey and A. antennatus at night would explain the lack of correlation between prey abundance in guts and in the environment found during daylight periods for most micronekton mesopelagic prey (euphausiids, myctophids and sergestids). Off Sóller, fullness and

  1. High consumption of primates by pumas and ocelots in a remnant of the Brazilian Atlantic Forest.

    PubMed

    Santos, J L; Paschoal, A M O; Massara, R L; Chiarello, A G

    2014-08-01

    We studied the diet of the ocelot and puma during the years 2007 and 2008 at the Feliciano Miguel Abdala Reserve, in Minas Gerais, south-eastern Brazil. We collected 49 faecal samples (scats) from cats, and identified the species of cat from 23 of them by the analysis of the microstructure patterns of hairs found in their faeces: 17 scats of the puma (Puma concolor) and six of the ocelot (Leopardus pardalis). In the puma scats, we identified three species of primates (Brachyteles hypoxanthus, Alouatta guariba and Sapajus nigritus), the remains of which were found in eight of 17 collected (47.1%), representing 26.7% of items consumed. For the ocelot, we detected capuchin monkey (S. nigritus) remains in three of the six scats (50%), accounting for 18.7% of items consumed by ocelot. We were unable to identify the cat species in the remaining 26 faecal samples, but we were able to analyse the food items present. Primates were found in five of these 26 faeces (19.2%) and represented 10.2% of the items found. Although the sample size is limited, our results indicate a relatively high consumption of primates by felines. We believe that this high predation may be the result of the high local density of primates as well as the greater exposure to the risks of predation in fragmented landscapes, which tends to increase the incidence of the primates using the ground.

  2. Impact of Different Salts in Soaking Water on the Cooking Time, Texture and Physical Parameters of Cowpeas.

    PubMed

    Ávila, Bianca Pio; Santos dos Santos, Magda; Nicoletti, Angélica Markus; Alves, Gabriela Dutra; Elias, Moacir Cardoso; Monks, Jander; Gularte, Márcia Arocha

    2015-12-01

    The characteristics of modern life has led consumers to seek convenience and speed in food preparation, but storage, which is often prolonged, can result in grain hardening, leading to higher energy consumption during preparation, grain with increased hardness is often discarded. Due to the increasing global demand for grain, the use of alternative techniques aimed at reducing grain waste is necessary. Therefore, we studied a method that meets consumer demand and results in better use of harvested grain. The beans studied were cowpea beans (Vigna unguiculata) of the BRS Guariba cultivar after 1 and 12 months of storage. Sodium chloride (NaCl), potassium chloride (KCl) and sodium bicarbonate (NaHCO3) were added to soaking water at different concentrations as a way to reduce cooking time. These beans were placed in soaking water for 12 h at 3 concentrations (0, 1.0 and 2.5%). The cowpeas soaked in water containing NaHCO3 presented the highest hydration coefficient, which increased with the salt concentration; these beans also had decreased hardness, chewiness and cooking time. PMID:26249219

  3. [Termites that build conspicuous nests in two areas of Atlantic Forest under different levels of anthropogenic disturbance].

    PubMed

    Vasconcellos, Alexandre; Bandeira, Adelmar G; Almeida, Waltécio O; Moura, Flávia M S

    2008-01-01

    The effects of selective logging on termite assemblages that build conspicuous nests were studied in two areas of semideciduous Atlantic Forest, located in the Reserva Biológica Guaribas, Northeastern Brazil. The two study areas went through selective logging until 1985 (A17) and 1972 (A30). In 2002, termite nests were studied in two plots of 1 ha (100 x 100 m), being one plot in each area. The nests were placed in each plot and the species were categorized in feeding groups. The structure of the study assemblages was different between the two areas. Diversity and richness of builder species were greater in the A30 area. Species that consume humus were more sensitive to selective logging. Nest abundance of humus feeding species was significantly higher in the A30 area, whereas nests of wood feeding species were significantly more abundant in the area A17. Nest ratio between humus and wood feeding species was 1:3 in the A30 area and 1:12 in the A17 area. Nests with greater volume were observed in the area A30, whereas abundance of inactive nests was significantly higher in A17. The time for habitat resilience after the selective logging influenced patterns of assemblage structure of termites in similar ways as described in other studies in tropical forests.

  4. Ochres from rituals of prehistoric human funerals at the Toca do Enoque site, Piauí, Brazil

    NASA Astrophysics Data System (ADS)

    Cavalcante, Luis Carlos Duarte; da Luz, Maria De Fátima; Guidon, Niéde; Fabris, José Domingos; Ardisson, José Domingos

    2011-11-01

    The archaeological site known as Toca do Enoque (geographical coordinates, 09° 14' 65.3″ S 43° 55' 62.5″ W) is a rock shelter located in the Serra das Andorinhas (Serra das Confusões National Park), rural area of the city of Guaribas, state of Piauí, Brazil. Several rupestrian paintings (anthropomorphic and zoomorphic motifs along with some pure graphisms), predominantly in red, are found on the sandstone walls. Charcoals, lithic materials, necklaces with teeth, animal bones, gastropod shells, ochres and human skeletons (dated from 6,220 ± 40 to 6,610 ± 40 years before present, BP) were identified in recent excavations in this shelter. Red and yellow ochre samples were collected from prehistoric funeral structures and analyzed with powder X-ray diffractometry, Fourier-transform infrared spectroscopy and 57Fe transmission Mössbauer spectroscopy at 298 K and 80 K. Mössbauer data indicate that the red ochre do contain predominantly hematite ( α-Fe2O3) whereas goethite ( α-FeOOH) is the major mineral in the yellow ochre.

  5. Impact of Different Salts in Soaking Water on the Cooking Time, Texture and Physical Parameters of Cowpeas.

    PubMed

    Ávila, Bianca Pio; Santos dos Santos, Magda; Nicoletti, Angélica Markus; Alves, Gabriela Dutra; Elias, Moacir Cardoso; Monks, Jander; Gularte, Márcia Arocha

    2015-12-01

    The characteristics of modern life has led consumers to seek convenience and speed in food preparation, but storage, which is often prolonged, can result in grain hardening, leading to higher energy consumption during preparation, grain with increased hardness is often discarded. Due to the increasing global demand for grain, the use of alternative techniques aimed at reducing grain waste is necessary. Therefore, we studied a method that meets consumer demand and results in better use of harvested grain. The beans studied were cowpea beans (Vigna unguiculata) of the BRS Guariba cultivar after 1 and 12 months of storage. Sodium chloride (NaCl), potassium chloride (KCl) and sodium bicarbonate (NaHCO3) were added to soaking water at different concentrations as a way to reduce cooking time. These beans were placed in soaking water for 12 h at 3 concentrations (0, 1.0 and 2.5%). The cowpeas soaked in water containing NaHCO3 presented the highest hydration coefficient, which increased with the salt concentration; these beans also had decreased hardness, chewiness and cooking time.

  6. Dissolution kinetics and etch pit studies of potassium aluminium sulphate

    NASA Astrophysics Data System (ADS)

    van der Hoek, B.; Van Enckevort, W. J. P.; Van Der Linden, W. H.

    1983-03-01

    The dissolution process of the {111} faces of potash alum is studied, both by microtopographic examinations of the etch pit patterns and by measurement of the dissolution kinetics in a rotating disc crystallizer. Both methods showed that the Cabrera-Levine dissolution theory holds for the two most common dislocation types ending on the {111} faces of potash alum. On the basis of the rotating disc experiments, the interfacial supersaturation of the etch pit experiments was roughly estimated. Using this, it was found that at interfacial supersaturations below -0.6% (dislocations with <110> Burgers vector) or below -0.85% (dislocations with <100> Burgers vector) numerous etch pits related to those dislocation types appeared. Below those undersaturations the dissolution process is mainly determined by volume diffusion. From the critical undersaturation, determined in the rotating disc crystallizer, the value of the edge free energy of a step was found to be approximately 0.01 J/m 2.

  7. Permanent genetic resources added to Molecular Ecology Resources Database 1 December 2010-31 January 2011.

    PubMed

    Agata, Kiyokazu; Alasaad, Samer; Almeida-Val, Vera Maria Fonseca; Alvarez-Dios, J A; Barbisan, F; Beadell, Jon S; Beltrán, J F; Benítez, M; Bino, G; Bleay, Colin; Bloor, P; Bohlmann, Jörg; Booth, Warren; Boscari, E; Caccone, Adalgisa; Campos, Tatiana; Carvalho, B M; Climaco, Gisele Torres; Clobert, Jean; Congiu, L; Cowger, Christina; Dias, G; Doadrio, I; Farias, Izeni Pires; Ferrand, N; Freitas, Patrícia D; Fusco, G; Galetti, Pedro M; Gallardo-Escárate, Cristian; Gaunt, Michael W; Ocampo, Zaneli Gomez; Gonçalves, H; Gonzalez, E G; Haye, Pilar; Honnay, O; Hyseni, Chaz; Jacquemyn, H; Jowers, Michael J; Kakezawa, Akihiro; Kawaguchi, Eri; Keeling, Christopher I; Kwan, Ye-Seul; La Spina, Michelangelo; Lee, Wan-Ok; Leśniewska, M; Li, Yang; Liu, Haixia; Liu, Xiaolin; Lopes, S; Martínez, P; Meeus, S; Murray, Brent W; Nunes, Aline G; Okedi, Loyce M; Ouma, Johnson O; Pardo, B G; Parks, Ryan; Paula-Silva, Maria Nazaré; Pedraza-Lara, C; Perera, Omaththage P; Pino-Querido, A; Richard, Murielle; Rossini, Bruno C; Samarasekera, N Gayathri; Sánchez, Antonio; Sanchez, Juan A; Santos, Carlos Henrique Dos Anjos; Shinohara, Wataru; Soriguer, Ramón C; Sousa, Adna Cristina Barbosa; Sousa, Carolina Fernandes Da Silva; Stevens, Virginie M; Tejedo, M; Valenzuela-Bustamante, Myriam; Van de Vliet, M S; Vandepitte, K; Vera, M; Wandeler, Peter; Wang, Weimin; Won, Yong-Jin; Yamashiro, A; Yamashiro, T; Zhu, Changcheng

    2011-05-01

    This article documents the addition of 238 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Alytes dickhilleni, Arapaima gigas, Austropotamobius italicus, Blumeria graminis f. sp. tritici, Cobitis lutheri, Dendroctonus ponderosae, Glossina morsitans morsitans, Haplophilus subterraneus, Kirengeshoma palmata, Lysimachia japonica, Macrolophus pygmaeus, Microtus cabrerae, Mytilus galloprovincialis, Pallisentis (Neosentis) celatus, Pulmonaria officinalis, Salminus franciscanus, Thais chocolata and Zootoca vivipara. These loci were cross-tested on the following species: Acanthina monodon, Alytes cisternasii, Alytes maurus, Alytes muletensis, Alytes obstetricans almogavarii, Alytes obstetricans boscai, Alytes obstetricans obstetricans, Alytes obstetricans pertinax, Cambarellus montezumae, Cambarellus zempoalensis, Chorus giganteus, Cobitis tetralineata, Glossina fuscipes fuscipes, Glossina pallidipes, Lysimachia japonica var. japonica, Lysimachia japonica var. minutissima, Orconectes virilis, Pacifastacus leniusculus, Procambarus clarkii, Salminus brasiliensis and Salminus hilarii. PMID:21457476

  8. Influence of doping on the etching of Si(111)

    NASA Astrophysics Data System (ADS)

    Winters, Harold F.; Haarer, D.

    1987-10-01

    Exposure of solid surfaces to reactive gases (or radicals) often leads to chemical reactions which produce volatile products. These are frequently called etching reactions. The example discussed in this paper involves the reaction of XeF2 with Si(111) to produce SiF4(gas). It will be shown that the etch rate depends strongly upon the concentration and type of dopant. It also depends upon the thickness of the fluorosilyl (SiFx) layer on the surface. The trends previously observed in plasma-assisted etching environments are shown to also occur in the XeF2-Si reaction. A simple model will be developed which indicates a strong correlation between the number of negative ions on the surface and the etch rate. The model is based upon some of the ideas originally proposed by Mott and Cabrera to describe oxide growth and on the Poisson-Boltzmann equation which describes the space charge at a semiconductor interface.

  9. Analysis of the laser oxidation kinetics process of In-In(2)O(3) MTMO photomasks by laser direct writing.

    PubMed

    Xia, Feng; Zhang, Xinzheng; Wang, Meng; Liu, Qian; Xu, Jingjun

    2015-11-01

    One kind of novel grayscale photomask based on Metal-transparent-metallic-oxides (MTMOs) system fabricated by laser direct writing was demonstrated recently. Here, a multilayer oxidation model of In-In(2)O(3) film with a glass substrate was proposed to study the pulsed laser-induced oxidation mechanism. The distribution of the electromagnetic field in the film is calculated by the transfer matrix method. Temperature fields of the model are simulated based on the heat transfer equations with the Finite-Difference Time-Domain method. The oxidation kinetics process is studied based on the laser-induced Cabrera-Mott theory. The simulated oxidation processes are consistent with the experimental results, which mean that our laser-induced oxidation model can successfully interpret the fabrication mechanism of MTMO grayscale photomasks.

  10. Implementation of a DOD ELAP Conforming Quality System at a FUSRAP Site Field Temporary Radiological Screening Laboratory - 13500

    SciTech Connect

    Winters, M.S.; McElheny, G.; Houston, L.M.; Masset, M.R.; Spector, H.L.

    2013-07-01

    A case study is presented on specific program elements that supported the transition of a temporary field radiological screening lab to an accredited operation capable of meeting client quality objectives for definitive results data. The temporary field lab is located at the Formerly Utilized Sites Remedial Action Program Linde Site in Tonawanda, NY. The site is undergoing remediation under the direction of the United States Army Corps of Engineers - Buffalo District, with Cabrera Services Inc. as the remediation contractor and operator of the on-site lab. Analysis methods employed in the on-site lab include gross counting of alpha and beta particle activity on swipes and air filters and gamma spectroscopy of soils and other solid samples. A discussion of key program elements and lessons learned may help other organizations considering pursuit of accreditation for on-site screening laboratories. (authors)

  11. Surface chemistry dependence of native oxidation formation on silicon nanocrystals

    SciTech Connect

    Liptak, R. W.; Campbell, S. A.; Kortshagen, U.

    2009-09-15

    The growth of silicon oxide on bare and SF{sub 6}-etched silicon nanocrystals (Si-NCs), which were synthesized by an all gas phase approach, was investigated by examining the surface chemistry and optical properties of the NCs over time. Consistent with previous work in the low temperature oxidation of silicon, the oxidation follows the Cabrera-Mott mechanism, and the measured data are well fitted to the Elovich equation. The use of the SF{sub 6} plasma is found to reduce the surface Si-H bond density and dramatically increase the monolayer growth rate. This is believed to be due to the much larger volatility of Si-F bonds compared to Si-H bonds on the surface of the NC.

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

    PubMed Central

    Tubée, Daniel B. Montesinos

    2014-01-01

    Abstract Three new species of the genus Senecio (Asteraceae, Senecioneae) belonging to Senecio ser. Suffruticosi subser. Caespitosi were discovered in the tributaries of the upper Tambo River, Moquegua Department, South Peru. Descriptions, diagnoses and discussions about their distribution, a table with the morphological similarities with other species of Senecio, a distribution map, conservation status assessments, and a key to the caespitose Peruvian species of Senecio subser. Caespitosi are provided. The new species are Senecio moqueguensis Montesinos, sp. nov. (Critically Endangered) which most closely resembles Senecio pucapampaensis Beltrán, Senecio sykorae Montesinos, sp. nov. (Critically Endangered) which most closely resembles Senecio gamolepis Cabrera, and Senecio tassaensis Montesinos, sp. nov. (Critically Endangered) which most closely resembles Senecio moqueguensis Montesinos. PMID:25197221

  13. Morpho-histological studies in the aromatic species of Chenopodium from Argentina.

    PubMed

    Bonzani, N E; Barboza, G E; Bugatti, M A; Ariza Espinar, L

    2003-04-01

    A morpho-histological study of the vegetative organs (stem and leaf) of the aromatic species of Chenopodium L. from Argentina [C. ambrosioides L., C. burkartii (Aellen) Vorosch., C. carinatum R. Br., C. chilense Schrad., C. graveolens Willd. var. bangii (Murr) Aellen, C. haumanii Ulbr., C. multifidum L., C. oblanceolatum (Speg.) Giusti, C. pumilio R. Br., C. retusum (Moq.) Moq., and C. venturii (Aellen) Cabrera] was carried out. Classifications for the glandular and non-glandular trichomes are established and their presence among species is presented. A variant in both the dorsiventral and isobilateral mesophyll is reported; some data are valuable for systematic purposes and for the identification of dried and smashed material used as vegetal drug.

  14. IMPROVING CONTROL ROOM DESIGN AND OPERATIONS BASED ON HUMAN FACTORS ANALYSES OR HOW MUCH HUMAN FACTORS UPGRADE IS ENOUGH ?

    SciTech Connect

    HIGGINS,J.C.; OHARA,J.M.; ALMEIDA,P.

    2002-09-19

    THE JOSE CABRERA NUCLEAR POWER PLANT IS A ONE LOOP WESTINGHOUSE PRESSURIZED WATER REACTOR. IN THE CONTROL ROOM, THE DISPLAYS AND CONTROLS USED BY OPERATORS FOR THE EMERGENCY OPERATING PROCEDURES ARE DISTRIBUTED ON FRONT AND BACK PANELS. THIS CONFIGURATION CONTRIBUTED TO RISK IN THE PROBABILISTIC SAFETY ASSESSMENT WHERE IMPORTANT OPERATOR ACTIONS ARE REQUIRED. THIS STUDY WAS UNDERTAKEN TO EVALUATE THE IMPACT OF THE DESIGN ON CREW PERFORMANCE AND PLANT SAFETY AND TO DEVELOP DESIGN IMPROVEMENTS.FIVE POTENTIAL EFFECTS WERE IDENTIFIED. THEN NUREG-0711 [1], PROGRAMMATIC, HUMAN FACTORS, ANALYSES WERE CONDUCTED TO SYSTEMATICALLY EVALUATE THE CR-LA YOUT TO DETERMINE IF THERE WAS EVIDENCE OF THE POTENTIAL EFFECTS. THESE ANALYSES INCLUDED OPERATING EXPERIENCE REVIEW, PSA REVIEW, TASK ANALYSES, AND WALKTHROUGH SIMULATIONS. BASED ON THE RESULTS OF THESE ANALYSES, A VARIETY OF CONTROL ROOM MODIFICATIONS WERE IDENTIFIED. FROM THE ALTERNATIVES, A SELECTION WAS MADE THAT PROVIDED A REASONABLEBALANCE BE TWEEN PERFORMANCE, RISK AND ECONOMICS, AND MODIFICATIONS WERE MADE TO THE PLANT.

  15. Narrowing of terrace-width distributions during growth on vicinal surfaces

    NASA Astrophysics Data System (ADS)

    Hamouda, A. BH.; Pimpinelli, A.; Einstein, T. L.

    2009-10-01

    We present analytic and numerical results for the steady-state, non-equilibrium terrace-width distribution (TWD) of steps during growth on vicinal surfaces. Kinetic Monte Carlo shows that the TWD narrows progressively with increasing flux until the model breaks down. The narrowing corresponds to kinetic repulsion between moving steps, due to the intrinsic asymmetry of the adatom diffusion current on a growing surface. With a 1-dimensional (1D) model, from a Burton-Cabrera-Frank approach, we make contact with previous work, in which the attachment asymmetry can also be due to electromigration or to asymmetry in attachment rates; we deduce an expression for the narrowing via a Fokker-Planck analysis. We illustrate how Ehrlich-Schwoebel barriers (although inducing an instability in 2D) also lead to such asymmetry and narrowing.

  16. New host records for European Acroceridae (Diptera), with discussion of species limits of Acrocera orbiculus (Fabricius) based on DNA-barcoding.

    PubMed

    Kehlmaier, Christian; Almeida, Jorge Mota

    2014-01-01

    New European host records for the Acroceridae species Acrocera orbiculus (Fabricius) and Ogcodes reginae Trojan are reported. Acrocera orbiculus was reared from Amaurobius erberi (Keyserling), and O. reginae from Clubiona leucaspis (Simon) and Evarcha jucunda (Lucas). Where possible, DNA-barcodes are presented for reared endoparasitoids and their host specimens. Based on mitochondrial COI, the intraspecific genetic variability of 15 western Palaearctic A. orbiculus is discussed. Maximum likelihood analysis reveals two clades, though they have low statistical support and no distinct barcoding gap. Therefore, we consider all barcoded specimens of A. orbiculus to be a single biological species with a high degree of phenotypic plasticity regarding body size and coloration. Based on molecular and morphological evidence, Paracrocera kaszabi Majer, Paracrocera manevali Séguy and Paracrocera minuscula Séguy are placed in synonymy with A. orbiculus. The male of the Canary Islands endemic Acrocera cabrerae Frey is described for the first time. 

  17. W.K.H. Panofsky Prize Talk: The Search for Weakly Interacting Massive Particle Dark Matter: Science Motivation and CDMS strategy

    NASA Astrophysics Data System (ADS)

    Sadoulet, Bernard

    2013-04-01

    For the last 25 years, Weakly Interacting Massive Particles (WIMPs) have remained one of the favored candidates to explain the ubiquitous dark matter in the universe. We will review the generic aspects of this class of models, and describe the complementarity between three observational approaches: the direct detection of terrestrial interactions of the halo WIMPs, the search for WIMP annihilation products in the cosmos and the attempt to produce these particles at the Large Hadron Collider. After a rapid review of the current status of these three searches, we will focus on the experimental strategy pursued by the Cryogenic Dark Matter Search as one of the leading direct detection effort in the world. We will conclude with the CDMS results obtained so far, in particular for low mass dark matter particles. In an accompanying talk, Blas Cabrera will describe the basic technology that we are using and the promise of our new generation of detectors.

  18. Late Miocene extension partitioning in the eastern Betics: from W- to E-directed extension between the Sorbas and Vera basins (SE Spain).

    NASA Astrophysics Data System (ADS)

    Giaconia, Flavio; Booth-Rea, Guillermo; Martínez-Martínez, Jose Miguel; Azañon, Jose Miguel

    2014-05-01

    Late Miocene westward-directed extension in the Betics produced elongated core-complexes like Sierra Nevada and the Sierra de Filabres, tilted-block domains and associated basins. This extension represents the superficial manifestation of the rupture of the Tethyan slab and associated edge delamination along a lithospheric transform fault beneath the northern branch of the Gibraltar Arc orogenic system. However, crustal thinning at the eastern Betics occurs progressively towards the east suggesting an eastward-directed extension, probably related to the late Miocene opening of the Algero-Balearic basin. In order to define the kinematics and timing of such a heterogeneous extension at the eastern Betics we have carefully mapped a key area at the transition between the Sorbas and Vera basins. Field data indicate that extension in the area started at the southern margin of the Vera basin during the Serravallian (13.8 Ma) and continued until the Tortonian (approximately 8 Ma). This extension was characterized by a set of NE- to E-directed normal faults to the east, in the Vera basin, and a set of SW-directed normal faults to the west, towards the Sorbas basin. This opposite-directed extension is segmented by E-W to WNW-ESE strike-slip faults like the North Cabrera dextral transfer fault that accommodates NE- to E-directed extension to the north and SW-directed extension to the south. This structure resulted in westward tilted blocks that lead to Serravallian-Tortonian depocenters deepening towards the east at the Vera basin along the northern side of Sierra Cabrera. Meanwhile, at the western termination of Sierra Cabrera, westward-directed extension migrated SW-ward forming the Sorbas basin during the Tortonian (approximately 9-7.24 Ma). This extension was characterized by a listric fan of SW-directed normal faults highly segmented by E-W to NE-SW transfer. This extensional system produced tiled-blocks defining a Tortonian depocenter at the eastern margin of the Sorbas

  19. Supersaturation in nucleus and spiral growth of GaN in metal organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Akasaka, Tetsuya; Kobayashi, Yasuyuki; Kasu, Makoto

    2010-10-01

    Nucleus and spiral growth mechanisms of GaN were experimentally studied by varying the degree of supersaturation, σ, in selective-area metal organic vapor phase epitaxy. The spiral growth rate of GaN increased proportionally to σ2 in the σ range from 0.0632 to 0.230. The nucleus growth rate of GaN was much smaller than the spiral one in the σ range. The nucleation rate was almost zero at σ lower than 0.130, suddenly increased at higher σ values, and reached ˜107 cm-2 s-1 at σ of 0.230. These results are consistent with a theoretical analysis [W. K. Burton, N. Cabrera, and F. C. Frank, Philos. Trans. R. Soc. London, Ser. A 243, 299 (1951)].

  20. Nucleus and Spiral Growth of N-face GaN(0001) Obtained by Selective-Area Metalorganic Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Hung; Akasaka, Tetsuya; Yamamoto, Hideki

    2013-03-01

    Nucleus and spiral growth mechanisms of N-face GaN(0001) were studied in selective-area metalorganic vapor phase epitaxy. An almost step-free N-face GaN surface is obtained by nucleus growth within a selective area without screw-type dislocations, while growth spirals are induced by the spiral growth mode when screw-type dislocations exist. The growth mechanism of N-face GaN is consistently explained by a theoretical analysis [W. K. Burton, N. Cabrera, and F. C. Frank: Philos. Trans. R. Soc. London, Ser. A 243 (1951) 299]. The step and activation energies are estimated to be 2.1 J/m2 and 2.15 eV, respectively.

  1. Emergence of step flow from an atomistic scheme of epitaxial growth in 1 +1 dimensions

    NASA Astrophysics Data System (ADS)

    Lu, Jianfeng; Liu, Jian-Guo; Margetis, Dionisios

    2015-03-01

    The Burton-Cabrera-Frank (BCF) model for the flow of line defects (steps) on crystal surfaces has offered useful insights into nanostructure evolution. This model has rested on phenomenological grounds. Our goal is to show via scaling arguments the emergence of the BCF theory for noninteracting steps from a stochastic atomistic scheme of a kinetic restricted solid-on-solid model in one spatial dimension. Our main assumptions are: adsorbed atoms (adatoms) form a dilute system, and elastic effects of the crystal lattice are absent. The step edge is treated as a front that propagates via probabilistic rules for atom attachment and detachment at the step. We formally derive a quasistatic step flow description by averaging out the stochastic scheme when terrace diffusion, adatom desorption, and deposition from above are present.

  2. Temperature and pressure dependent Mott potentials and their influence on self-limiting oxide film growth

    NASA Astrophysics Data System (ADS)

    Cai, Na; Zhou, Guangwen; Müller, Kathrin; Starr, David E.

    2012-10-01

    Classic Cabrera-Mott theory stipulates that the limited oxide-film growth results from electron tunneling from the metal through the oxide film to adsorbed oxygen. This leads to an electric field across the oxide film that assists ion migration for low-temperature oxide-film growth. Here, we show that the field-driven oxide-film growth can be manipulated via the temperature and pressure of oxidation. The magnitude of the self-generated electric field depends on the oxygen surface coverage that exhibits a Langmuir isotherm behavior with changes in temperature and oxygen pressure. These observations demonstrate the ability to tune an interfacial reaction via self-adaptation to its environment.

  3. Impact of surface phase coexistence on the development of step-free areas on Si(111)

    NASA Astrophysics Data System (ADS)

    Fissel, Andreas; Chaudhuri, Ayan Roy; Krügener, Jan; Gribisch, Philipp; Osten, H. Jörg

    2015-04-01

    The step-flow growth condition of Si on Si(111) near the (7×7)-"1×1" surface phase transition temperature T C are analyzed within the framework of Burton-Cabrera-Frank theory. In particular, coexistence of both surface phases well below T C and their specific influence on the step-flow growth behavior are considered. We presume that under dynamical condition of growth, the surface initially covered by only the (7×7) phase separates into domains surrounded by "1×1" areas. On such a surface, the overall supersaturation should be reduced drastically compared to a surface with only (7×7), resulting in much larger critical terrace width for nucleation.

  4. Coupling data from U-series and 10Be CRN to evaluate soil steady-state in the Betic Cordillera

    NASA Astrophysics Data System (ADS)

    Schoonejans, Jerome; Vanacker, Veerle; Opfergelt, Sophie; Granet, Mathieu; Chabaux, François

    2015-04-01

    The regolith mantel is produced by weathering of bedrock through physical and biochemical processes. At the same time, the upper part of the regolith is eroded by gravity mass movements, water and wind erosion. Feedback's between production and erosion of soil material are important for soil development, and are essential to reach long-term steady-state in soil chemical and physical properties. Nowadays, long-term denudation rates of regolith can be quantified by using in-situ cosmogenic nuclides (CRN). If the soil thickness remains constant over sufficiently long time, soil production rates can be determined. However, the a priori assumption of long-term steady-state can be questionable in highly dynamic environments. In this study, we present analytical data from two independent isotopic techniques, in-situ cosmogenic nuclides and Uranium series disequilibrium. The disequilibrium of Uranium isotopes (238U, 234U, 230Th, 226Ra) is an alternative method that allows assessing soil formation rates through isotopic analysis of weathering products. Nine soil profiles were sampled in three different mountain ranges of the Betic Cordillera (SE Spain): Sierra Estancias, Filabres, Cabrera. All soils overly fractured mica schist and are very thin (< 60cm). In each soil profile, we sampled 4 to 6 depth slices in the soil profile, the soil-bedrock interface and (weathered) bedrock. Three of the nine soil profiles were sampled for U-series isotope measurements at EOST (University of Strasbourg). The surface denudation rates (CRN) are about the same in the Sierra Estancias and Filabres (26 ± 10 mm/ky) and increase up to 103 ± 47 mm/ky in the Sierra Cabrera. The spatial variation in soil denudation rates is in agreement with the variation in catchment-wide denudation rates presented by Bellin et al. (2014) which present the highest rates in the Sierra Cabrera (104-246mm/kyr). Moreover it roughly coincides with the pattern of long-term exhumation of the Betic Cordillera. Results

  5. Influence of (7×7)-"1×1" phase transition on step-free area formation in molecular beam epitaxial growth of Si on Si (111)

    NASA Astrophysics Data System (ADS)

    Fissel, Andreas; Roy Chaudhuri, Ayan; Krügener, Jan; Jörg Osten, H.

    2015-09-01

    The step-flow growth condition of Si on Si (111) near the (7×7)-"1×1" surface phase transition temperature TC is analysed within the framework of Burton-Cabrera-Frank theory. In particular, coexistence of both surface phases well below TC and their specific influence on the step-flow growth behaviour is considered. We presume that under dynamical condition of growth, the surface initially covered by only the (7×7) phase separates into domains surrounded by "1×1" areas. On such a surface, the overall supersaturation should be reduced drastically compared to a surface with only (7×7), resulting in much larger critical terrace width for nucleation.

  6. Peculiarities of the growth of KDP single crystals with incorporated aluminium oxyhydroxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Pritula, I. M.; Kosinova, A. V.; Vorontsov, D. A.; Kolybaeva, M. I.; Bezkrovnaya, O. N.; Tkachenko, V. F.; Vovk, O. M.; Grishina, E. V.

    2012-09-01

    Grown for the first time are KH2PO4 (KDP) crystals with incorporated aluminium oxyhydroxide Al2O3·nH2O nanoparticles (n=3.5-3.6). The influence of the nanoparticles on the structure perfection and the growth kinetics of the crystal faces are studied. The presence of the nanoparticles in the crystal matrix is confirmed by the results of chemical analysis, X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The most essential inhibiting effect of the nanoparticles is observed for the {100} faces. The mechanism of influence of the nanoparticles on the {100} faces growth is explained on the base of the Cabrera-Vermilyea (C-V) model using Langmuir adsorption isotherm.

  7. Reactive self-heating model of aluminum spherical nanoparticles

    NASA Astrophysics Data System (ADS)

    Martirosyan, Karen S.; Zyskin, M.

    2013-02-01

    Aluminum-oxygen reaction is important in highly energetic and high pressure generating systems. Recent experiments with nanostructured thermites suggest that oxidation of aluminum nanoparticles occurs in a few microseconds. Such rapid reaction cannot be explained by a conventional diffusion-based mechanism. We present a rapid oxidation model of a spherical aluminum nanoparticle, using Cabrera-Mott moving boundary mechanism, and taking self-heating into account. In our model, electric potential solves the nonlinear Poisson equation. In contrast with the Coulomb potential, a "double-layer" type solution for the potential and self-heating leads to enhanced oxidation rates. At maximal reaction temperature of 2000 °C, our model predicts overall oxidation time scale in microseconds range, in agreement with the experimental evidence.

  8. Mechanism for Limiting Thickness of Thin Oxide Films on Aluminum

    NASA Astrophysics Data System (ADS)

    Baran, Jakub D.; Grönbeck, Henrik; Hellman, Anders

    2014-04-01

    A first-principles account of the observed limiting thickness of oxide films formed on aluminum during oxidizing conditions is presented. The results uncover enhanced bonding of oxygen to thin alumina films in contact with metallic aluminum that stems from charge transfer between a reconstructed oxide-metal interface and the adsorbed molecules. The first-principles results are compared with the traditional Cabrera-Mott (CM) model, which is a classical continuum model. Within the CM model, charged surface oxygen species and metal ions generate a (Mott) potential that drives oxidation. An apparent limiting thickness is observed as the oxidation rate decreases rapidly with film growth. The present results support experimental estimates of the Mott potential and film thicknesses. In contrast to the CM model, however, the calculations reveal a real limiting thickness that originates from a diminishing oxygen adsorption energy beyond a certain oxide film thickness.

  9. Comparison of the spiral growth modes of silicon-face and carbon-face silicon carbide crystals

    NASA Astrophysics Data System (ADS)

    Seiss, M.; Ouisse, T.; Chaussende, D.

    2013-12-01

    We have studied the dependence of the terrace width of growth spirals on local supersaturation during the growth of on-axis silicon carbide (SiC) crystals. Local supersaturation is adjusted by changing the residual argon gas pressure inside the sublimation growth chamber. Whereas Si-face crystals seem to partly verify the model of Burton, Cabrera and Frank, we found that on C-face crystals, the terrace width is independent of supersaturation. In contrast to previously reported data obtained from KDP crystals, we cannot ascribe our result to hollow-core dislocations or micropipes, as the observed growth spirals arose from independent and closed, unit or double-unit screw dislocations. Besides, we checked that neither the finite growth area nor the influence of the stress field of the dislocation can explain our data.

  10. Kinetics of mass crystallization of calcium carbonate at 25, 30 and 37 °C

    NASA Astrophysics Data System (ADS)

    Rosa, Silvia; Lundager Madsen, Hans E.

    2011-03-01

    Calcium carbonate crystal growth kinetics was studied by simple mass crystallization, recording pH as function of time. The phase crystallizing was vaterite at 25 °C, calcite at 30 °C and aragonite at 37 °C. Growth kinetics at the initial stage followed that of the polynuclear surface nucleation mechanism, and from the slopes of linearized graphs edge free energies of the three phases could be determined. The values were: calcite 35.4 pJ/m at 30 °C, aragonite 32.3 pJ/m at 37 °C and vaterite 24.2 pJ/m at 25 °C. These values agree reasonably well with literature values determined by other methods, and they are useful in testing the validity of the relation between step distance of a growth spiral and size of a critical surface nucleus as assumed in the Burton-Cabrera-Frank theory.

  11. Order-disorder transition in clathrate Ba6Ge25 studied by positron annihilation

    NASA Astrophysics Data System (ADS)

    Li, X. F.; Zhao, B.; Zhang, T.; He, H. F.; Zhang, Q.; Yang, D. W.; Chen, Z. Q.; Tang, X. F.

    2015-07-01

    Clathrate Ba6Ge25 is prepared by melt method and spark plasma sintering. Structural transition below room temperature is studied by positron annihilation and X-ray diffraction measurements. There is a pronounced transition in the temperature range of 200-250 K which might be involved with the movement of Ba atoms in Ge cages and result in disordered structure. This transition is further confirmed by the theoretical calculation of positron annihilation states. Thus our results confirm the structural models proposed by Carrillo-Cabrera et al. (2005). The measured specific heat capacity, electric resistivity and magnetic susceptibility all show anomalous transition in the same temperature range, indicating that the movement of Ba atoms in the cage has influence on the thermal, electric as well as magnetic properties of Ba6Ge25.

  12. Spiral and target patterns in bivalve nacre manifest a natural excitable medium from layer growth of a biological liquid crystal.

    PubMed

    Cartwright, Julyan H E; Checa, Antonio G; Escribano, Bruno; Sainz-Díaz, C Ignacio

    2009-06-30

    Nacre is an exquisitely structured biocomposite of the calcium carbonate mineral aragonite with small amounts of proteins and the polysaccharide chitin. For many years, it has been the subject of research, not just because of its beauty, but also to discover how nature can produce such a superior product with excellent mechanical properties from such relatively weak raw materials. Four decades ago, Wada [Wada K (1966) Spiral growth of nacre. Nature 211:1427] proposed that the spiral patterns in nacre could be explained by using the theory Frank [Frank F (1949) The influence of dislocations on crystal growth. Discuss Faraday Soc 5:48-54] had put forward of the growth of crystals by means of screw dislocations. Frank's mechanism of crystal growth has been amply confirmed by experimental observations of screw dislocations in crystals, but it is a growth mechanism for a single crystal, with growth fronts of molecules. However, the growth fronts composed of many tablets of crystalline aragonite visible in micrographs of nacre are not a molecular-scale but a mesoscale phenomenon, so it has not been evident how the Frank mechanism might be of relevance. Here, we demonstrate that nacre growth is organized around a liquid-crystal core of chitin crystallites, a skeleton that the other components of nacre subsequently flesh out in a process of hierarchical self-assembly. We establish that spiral and target patterns can arise in a liquid crystal formed layer by layer through the Burton-Cabrera-Frank [Burton W, Cabrera N, Frank F (1951) The growth of crystals and the equilibrium structure of their surfaces. Philos Trans R Soc London Ser A 243:299-358] dynamics, and furthermore that this layer growth mechanism is an instance of an important class of physical systems termed excitable media. Artificial liquid crystals grown in this way may have many technological applications.

  13. Gibbs-Thomson Law for Singular Step Segments: Thermodynamics Versus Kinetics

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2003-01-01

    Classical Burton-Cabrera-Frank theory presumes that thermal fluctuations are so fast that at any time density of kinks on a step is comparable with the reciprocal intermolecular distance, so that the step rate is about isotropic within the crystal plane. Such azimuthal isotropy is, however, often not the case: Kink density may be much lower. In particular, it was recently found on the (010) face of orthorhombic lysozyme that interkink distance may exceed 500-600 intermolecular distances. Under such conditions, Gibbs-Thomson law (GTL) may not be applicable: On a straight step segment between two corners, communication between the comers occurs exclusively by kink exchange. Annihilation between kinks of opposite sign generated at the comers results in the grain in step energy entering GTL. If the step segment length l much greater than D/v, where D and v are the kink diffusivity and propagation rate, respectively, the opposite kinks have practically no chance to annihilate and GTL is not applicable. The opposite condition of the GTL applicability, l much less than D/v, is equivalent to the requirement that relative supersaturation Delta(sub mu)/kT much less than alpha/l, where alpha is molecular size. Thus, GTL may be applied to a segment of 10(exp 3)alpha approx. 3 x 10(exp -5)cm approx 0.3 micron only if supersaturation is less than 0.1%, while practically used driving forces for crystallization are much larger. Relationships alternative to the GTL for different, but low, kink density have been discussed. They confirm experimental evidences that the Burton-Cabrera-Frank theory of spiral growth is growth rates twice as low as compared to the observed figures. Also, application of GTL results in unrealistic step energy while suggested kinetic law give reasonable figures.

  14. Effects of chlorinated solvents on four species of North American amphibians.

    PubMed

    McDaniel, T V; Martin, P A; Ross, N; Brown, S; Lesage, S; Pauli, B D

    2004-07-01

    Tetrachloroethylene (PCE), a dry cleaning and degreasing solvent, can enter groundwater through accidental leaks or spills, and concentrations as high as 75 mg/L have been reported in Canadian aquifers. Amphibians in wetlands receiving contaminated groundwater may be exposed to PCE and its degradation products, but little information is available on the impacts of these compounds on indigenous amphibian species. Acute (96-h static renewal) exposures to PCE and its major degradation products, trichloroethylene (TCE) and cisand trans-dichloroethylene, were conducted on embryos of four North American amphibian species: wood frogs (Rana sylvatica), green frogs (R. clamitans), American toads (Bufo americanus), and spotted salamanders (Ambystoma maculatum). Subsequently, chronic exposures to PCE and TCE were conducted with the larvae of American toads. Both PCE and TCE were teratogenic to amphibian embryos; median effective concentrations (EC50s) for developmental deformities produced by PCE and TCE exposure for wood frogs and green frogs were 12 and 40 mg/L, respectively. Embryonic survivorship, however, was not compromised at these concentrations. American toads were less sensitive; the EC50 for developmental abnormalities was not attained at the highest test concentrations, 45 and 85 mg/L PCE and TCE, respectively. These results are pertinent in assessing the impact of groundwater pollution on an aquifer-fed wetland.

  15. Effects of Terrestrial Buffer Zones on Amphibians on Golf Courses

    PubMed Central

    Puglis, Holly J.; Boone, Michelle D.

    2012-01-01

    A major cause of amphibian declines worldwide is habitat destruction or alteration. Public green spaces, such as golf courses and parks, could serve as safe havens to curb the effects of habitat loss if managed in ways to bolster local amphibian communities. We reared larval Blanchard's cricket frogs (Acris blanchardi) and green frogs (Rana clamitans) in golf course ponds with and without 1 m terrestrial buffer zones, and released marked cricket frog metamorphs at the golf course ponds they were reared in. Larval survival of both species was affected by the presence of a buffer zone, with increased survival for cricket frogs and decreased survival for green frogs when reared in ponds with buffer zones. No marked cricket frog juveniles were recovered at any golf course pond in the following year, suggesting that most animals died or migrated. In a separate study, we released cricket frogs in a terrestrial pen and allowed them to choose between mown and unmown grass. Cricket frogs had a greater probability of using unmown versus mown grass. Our results suggest that incorporating buffer zones around ponds can offer suitable habitat for some amphibian species and can improve the quality of the aquatic environment for some sensitive local amphibians. PMID:22761833

  16. Echinostome-induced mortality varies across amphibian species in the field.

    PubMed

    Holland, Manja P

    2010-10-01

    Echinostomes are receiving increased attention because of their emerging parasite status in landscapes associated with human development and their ability to infect and kill many North American larval amphibians. While laboratory experiments have shown that echinostomes can cause extensive mortality in their amphibian hosts, their effect on tadpoles in the field is less clear. I conducted a controlled-infection field-enclosure experiment in 4 ponds to compare the effects of echinostomes on green frog (Rana clamitans) and gray tree frog (Hyla versicolor) tadpoles in the field. I measured tadpole growth, development, mortality, and infection intensity. Echinostome infection resulted in high mortality in green frog tadpoles and less mortality in gray tree frogs. However, metacercariae encystment rates were higher in gray tree frog tadpoles than in green frog tadpoles. The effect of echinostomes on mortality varies across amphibian species, with the result that some species may experience more extensive echinostome-induced mortality than others. Mortality as a result of echinostome infection in green frog tadpoles was similar to mortality observed in predation experiments. PMID:20469948

  17. Drainage ditches facilitate frog movements in a hostile landscape

    USGS Publications Warehouse

    Mazerolle, M.J.

    2005-01-01

    Ditches are common in landscapes influenced by agricultural, forestry, and peat mining activities, and their value as corridors remains unassessed. Pond-breeding amphibians can encounter hostile environments when moving between breeding, summering, or hibernation sites, and are likely to benefit from the presence of ditches in the landscape. Within a system consisting of ditch networks in bogs mined for peat in eastern New Brunswick, Canada, I quantified the breeding, survival, and movements of green frogs (Rana clamitans melanota) in drainage ditches and also surveyed peat fields. Frogs rarely ventured on peat fields and most individuals frequented drainage ditches containing water, particularly in late summer. Though frogs did not breed in ditches, their survival rate in ditches was high (88%). Ditches did not hinder frog movements, as frogs moved independently of the current. Results indicate that drainage ditches containing water enable some movements between habitats isolated by peat mining, in contrast to peat surfaces, and suggest they function as amphibian movement corridors. Thus, such drainage ditches may mitigate the effects of peat extraction on amphibian populations. At the very least, these structures provide an alternative to hostile peat surfaces. This study highlights that small-scale corridors are potentially valuable in population dynamics. ?? Springer 2005.

  18. Landscape resistance to frog movements

    USGS Publications Warehouse

    Mazerolle, M.J.; Desrochers, A.

    2005-01-01

    An animal's capacity to recolonize a patch depends on at least two components: its ability to detect the patch and its ability to reach it. However, the disruption of such processes by anthropic disturbances could explain low animal abundance patterns observed by many investigators in certain landscapes. Through field experiments, we compared the orientation and homing success of northern green frogs (Rana clamitans melanota Rafinesque, 1820) and northern leopard frogs (Rana pipiens Schreber, 1782) translocated across disturbed or undisturbed surfaces. We also monitored the path selected by individuals when presented with a choice between a short distance over a disturbed surface and a longer, undisturbed route. Finally, we measured the water loss and behaviour of frogs on substrates resulting from anthropogenic disturbances and a control. When presented with a choice, 72% of the frogs avoided disturbed surfaces. Although able to orient towards the pond of capture when translocated on disturbed surfaces, frogs had a lower probability of homing successfully to the pond than when translocated at a similar distance on an undisturbed surface. Frogs lost the most water on substrates associated with disturbance and in the absence of cover. Our data illustrate that anthropically disturbed areas devoid of cover, such as mined peatlands and agricultural fields, disrupt the ability of frogs to reach habitat patches and are likely explanations to their reduced abundance patterns in such environments. ?? 2005 NRC Canada.

  19. Evaluating the effects of land use on headwater wetland amphibian assemblages in coastal Alabama

    USGS Publications Warehouse

    Alix, Diane M.; Anderson, Christopher J.; Grand, James B.; Guyer, Craig

    2014-01-01

    Anthropogenic land use is known to impact aquatic ecosystems in several ways, including increased frequency and intensity of floods, stream channel incision, sedimentation, and loss of microtopography. Amphibians are susceptible to changes in wetland and surrounding habitats. This study evaluated amphibian assemblages of fifteen headwater slope wetlands in coastal Alabama across a gradient of land uses. Amphibians were surveyed on a seasonal basis and land use was delineated within wetland watersheds and within a 200-m buffer surrounding each wetland. Amphibian presence/absence and land use data were used to develop species occupancy models. Both urban and agricultural land use were shown to influence amphibian occurrence. Species richness ranged from five to ten species across sites; however, five species only occurred in wetlands surrounded by forested lands. Many species were detected more frequently on these wetlands compared to wetlands surrounded by urban or mixed land uses. Occupancy models showed Acris gryllus was negatively associated with the amount of agriculture within a buffer around the wetland. Hyla squirella, Lithobates clamitans, and L. sphenocephalus were positively associated with agricultural land within a watershed. Anaxyrus terrestris and the non-native Eleutherodactylus planirostris were positively associated with the amount of impervious surface area within the wetland buffer.

  20. Evaluation of a waistband for attaching external radiotransmitters to anurans

    USGS Publications Warehouse

    Groff, Luke A.; Pitt, Amber L.; Baldwin, Robert F.; Calhoun, Aram J. K.; Loftin, Cyndy

    2015-01-01

    Radiotelemetry provides fine-scale temporal and spatial information about an individual's movements and habitat use; however, its use for monitoring amphibians has been restricted by transmitter mass and lack of suitable attachment techniques. We describe a novel waistband for attaching external radiotransmitters to anurans and evaluate the percentages of resulting abrasions, lacerations, and shed transmitters. We used radiotelemetry to monitor movements and habitat use of wood frogs (Lithobates sylvaticus) in 2006 and 2011–2013 in Maine, USA; American toads (Anaxyrus americanus) in 2012 in North Carolina, USA; and, wood frogs, southern leopard frogs (L. sphenocephalus), and green frogs (L. clamitans) in 2012 in South Carolina, USA. We monitored 172 anurans for 1–365 days (56.4 ± 59.4) in a single year and 1–691 days (60.5 ± 94.1) across years. Our waistband resulted in an injury percentage comparable to 7 alternative anuran waistband attachment techniques; however, 12.5% fewer anurans shed their waistband when attached with our technique. Waistband retention facilitates longer monitoring periods and, thus, provides a greater quantity of data per radiotagged individual.

  1. Effects of technical-grade active ingredient vs. commercial formulation of seven pesticides in the presence or absence of UV radiation on survival of green frog tadpoles.

    PubMed

    Puglis, Holly J; Boone, Michelle D

    2011-01-01

    Commercial formulations of pesticides contain both active and other ingredients. In some instances, the other ingredients have detrimental effects on nontarget species. Other factors such as UV radiation and predator cues have been shown to modify the toxicity of pesticides. In a laboratory study we compared the effects of technical-grade active ingredients to commercial formulations of seven common pesticides in the presence or absence of UV radiation on the survival of Rana clamitans (green frog) tadpoles over 96 h. We found a significant difference in the survival of tadpoles in technical-grade active ingredients versus commercial formulations in all of the pesticides tested. We also found that either the presence or the absence of UV radiation affected the survival of tadpoles in five of the seven pesticides tested. These results suggest that there is a need to test the effects of both active ingredients and commercial formulations of pesticides and, also, to include relevant abiotic factors like UV radiation treatments in the testing of pesticides because they can have a dramatic impact on the toxicity of some chemicals. PMID:20422168

  2. Circus movements in dissociated cells from two new hybrid frog embryos.

    PubMed

    Johnson, K E; Adelman, M R

    1984-06-01

    Circus movements are a peculiar kind of cell movement, seen in many amphibian cells, that involve the formation of a hyaline protrusion from the cell surface and rotation of this blister around the circumference of the cell. Studies of cells from normal Rana pipiens embryos have shown a close correlation between circus movements in vitro and gastrulation related cell movements in vivo. Cells from two developmentally arrested hybrid embryos (R. pipiens female X R. sylvatica male and R. pipiens female X R. catesbiana male) are deficient in circus movements to an extent that corresponds to their gastrulation deficiencies. This study reports on the preparation of two new hybrids (R. pipiens female X R. temporaria male (temp) and R. pipiens female X R. clamitans male (clam)). Cells from temp embryos show some circus movements but the proportion of cells displaying such movements does not increase with increasing developmental age to the same extent as is seen in cells from normal embryos. Cells from clam embryos show very few circus movements at any developmental age. These aberrations in the onset and extent of circus movements are discussed in relation to characteristic morphogenetic events that occur in normal embryos and in these two new arrested hybrid embryos.

  3. Circus movements in dissociated cells from two new hybrid frog embryos.

    PubMed

    Johnson, K E; Adelman, M R

    1984-06-01

    Circus movements are a peculiar kind of cell movement, seen in many amphibian cells, that involve the formation of a hyaline protrusion from the cell surface and rotation of this blister around the circumference of the cell. Studies of cells from normal Rana pipiens embryos have shown a close correlation between circus movements in vitro and gastrulation related cell movements in vivo. Cells from two developmentally arrested hybrid embryos (R. pipiens female X R. sylvatica male and R. pipiens female X R. catesbiana male) are deficient in circus movements to an extent that corresponds to their gastrulation deficiencies. This study reports on the preparation of two new hybrids (R. pipiens female X R. temporaria male (temp) and R. pipiens female X R. clamitans male (clam)). Cells from temp embryos show some circus movements but the proportion of cells displaying such movements does not increase with increasing developmental age to the same extent as is seen in cells from normal embryos. Cells from clam embryos show very few circus movements at any developmental age. These aberrations in the onset and extent of circus movements are discussed in relation to characteristic morphogenetic events that occur in normal embryos and in these two new arrested hybrid embryos. PMID:6490739

  4. Pathologic findings in larval and juvenile anurans inhabiting farm ponds in Tennessee, USA.

    PubMed

    Miller, Debra L; Gray, Matthew J; Rajeev, Sreekumari; Schmutzer, A Chandler; Burton, Elizabeth C; Merrill, Anita; Baldwin, Charles A

    2009-04-01

    Amphibian populations are declining globally, yet general pathologic surveys for free-ranging amphibians are uncommon. Pathologic surveys are necessary to provide insight into the impacts of humans on emergence of pathogens in amphibian populations. During 2005, 104 American bullfrog (Rana catesbeiana) and 80 green frog (Rana clamitans) larvae and 40 green frog juveniles were collected from farm ponds in Tennessee, and complete necropsies were performed. Diagnostic testing included bacterial culture, virus testing, fecal parasite analysis, and histologic examination. Gross and histologic examination revealed that all individuals, except one bullfrog tadpole, could be classified as clinically normal. The clinically abnormal tadpole had swollen erythemic legs, and was positive for Aeromonas hydrophila but negative for Ranavirus. Parasites were common (43%) among specimens, with myxosporidium and trematodes most often noted. Commensal and opportunistic microorganisms were cultured from the tissues. Ranavirus was detected in 29% of individuals but generally not associated with significant histopathologic changes. Myxosporidia and Ranavirus coinfections occurred in 7 and 26% of green and bullfrog tadpoles, respectively, with the highest coinfection rate (83%) in bullfrog tadpoles during winter. Protozoans were most common in fecal examination. These data can serve as a baseline to evaluate the presence of clinical disease in larval and juvenile amphibians. PMID:19395741

  5. The lethal impacts of Roundup and predatory stress on six species of North American tadpoles.

    PubMed

    Relyea, R A

    2005-04-01

    The decline in amphibians across the globe has sparked a search for the causes, and recent evidence suggests a connection with pesticides. However, for most pesticides, tests on amphibians are rare and conducted only for short durations (1 to 4 days) and without natural stressors. Recent studies have discovered that the stress of predator cues in the water can make insecticides much more lethal to larval amphibians, but it is unknown whether this phenomenon can be generalized to other types of pesticides. Using six species of North American amphibian larvae (Rana sylvatica, R. pipiens, R. clamitans, R. catesbeiana, Bufo americanus, and Hyla versicolor), I examined the impact of a globally common herbicide (Roundup) on the survival of tadpoles for 16 days with and without the chemical cues emitted by predatory newts (Notophthalmus viridescens). LC50(16-d) estimates varied from 0.55 to 2.52 mg of active ingredient (AI)/L, which was considerably lower than the few previous studies using Roundup (1.5 to 15.5 mg AI/L). Moreover, in one of the six species tested (R. sylvatica), the addition of predatory stress made Roundup twice as lethal. This discovery suggests that synergistic interactions between predatory stress and pesticides may indeed be a generalizable phenomenon in amphibians that occurs with a wide variety of pesticides. PMID:15886853

  6. Ambient solar UV radiation causes mortality in larvae of three species of Rana under controlled exposure conditions.

    PubMed

    Tietge, J E; Diamond, S A; Ankley, G T; DeFoe, D L; Holcombe, G W; Jensen, K M; Degitz, S J; Elonen, G E; Hammer, E

    2001-08-01

    Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) (290-320 nm) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens, Rana clamitans and Rana septentrionalis, were exposed to full-spectrum solar radiation and solar radiation filtered to attenuate UV-B radiation or UV-B and ultraviolet-A (UV-A) (290-380 nm) radiation to determine the effects of each wavelength range on embryo and larval survival. Ambient levels of solar radiation were found to be lethal to all three species under exposure conditions that eliminated shade and refuge. Lethality was ameliorated by filtration of UV-B radiation alone, demonstrating that ambient UV-B radiation is sufficient to cause mortality. Although several studies have qualitatively demonstrated the lethality of UV-B to early life stage amphibians this study demonstrates that the larval life stages of the three species tested are more sensitive than the embryonic stages. This suggests that previous reports that have not included the larval life stage may underestimate the risk posed to some anuran populations by increasing UV-B exposure. Furthermore, this study reports quantitative UV-B dosimetry data, collected in conjunction with the exposures, which can be used to begin the assessment of the impact of environmental changes which increase UV-B exposure of these anurans. PMID:11547564

  7. Peatlands and green frogs: A relationship regulated by acidity?

    USGS Publications Warehouse

    Mazerolle, M.J.

    2005-01-01

    The effects of site acidification on amphibian populations have been thoroughly addressed in the last decades. However, amphibians in naturally acidic environments, such as peatlands facing pressure from the peat mining industry, have received little attention. Through two field studies and an experiment, I assessed the use of bog habitats by the green frog (Rana clamitans melanota), a species sensitive to various forestry and peat mining disturbances. First, I compared the occurrence and breeding patterns of frogs in bog and upland ponds. I then evaluated frog movements between forest and bog habitats to determine whether they corresponded to breeding or postbreeding movements. Finally, I investigated, through a field experiment, the value of bogs as rehydrating areas for amphibians by offering living Sphagnum moss and two media associated with uplands (i.e., water with pH ca 6.5 and water-saturated soil) to acutely dehydrated frogs. Green frog reproduction at bog ponds was a rare event, and no net movements occurred between forest and bog habitats. However, acutely dehydrated frogs did not avoid Sphagnum. Results show that although green frogs rarely breed in bogs and do not move en masse between forest and bog habitats, they do not avoid bog substrates for rehydrating, despite their acidity. Thus, bogs offer viable summering habitat to amphibians, which highlights the value of these threatened environments in terrestrial amphibian ecology.

  8. Effects of terrestrial buffer zones on amphibians on golf courses.

    PubMed

    Puglis, Holly J; Boone, Michelle D

    2012-01-01

    A major cause of amphibian declines worldwide is habitat destruction or alteration. Public green spaces, such as golf courses and parks, could serve as safe havens to curb the effects of habitat loss if managed in ways to bolster local amphibian communities. We reared larval Blanchard's cricket frogs (Acris blanchardi) and green frogs (Rana clamitans) in golf course ponds with and without 1 m terrestrial buffer zones, and released marked cricket frog metamorphs at the golf course ponds they were reared in. Larval survival of both species was affected by the presence of a buffer zone, with increased survival for cricket frogs and decreased survival for green frogs when reared in ponds with buffer zones. No marked cricket frog juveniles were recovered at any golf course pond in the following year, suggesting that most animals died or migrated. In a separate study, we released cricket frogs in a terrestrial pen and allowed them to choose between mown and unmown grass. Cricket frogs had a greater probability of using unmown versus mown grass. Our results suggest that incorporating buffer zones around ponds can offer suitable habitat for some amphibian species and can improve the quality of the aquatic environment for some sensitive local amphibians.

  9. Responses of amphibian populations to water and soil factors in experimentally-treated aquatic macrocosms

    USGS Publications Warehouse

    Sparling, D.W.; Lowe, T.P.; Day, D.; Dolan, K.

    1995-01-01

    Survival of anuran embryos and tadpoles is reduced in acidic (pH < 5.0) waters under laboratory conditions. However, field data on the presence-absence of amphibian species and acidity are equivocal. This study attempts to reconcile some of this discrepancy by using macrocosms to examine the interaction of soil type and water acidification on free-ranging tadpole populations. Tadpoles were caught with activity traps in 24 aquatic macrocosms experimentally treated with H2SO4 and Al2(SO4)3 and lined with either comparatively high metal, Iow organic matter clay soils or lower metal, higher organic matter loams. Northern cricket frog (Acris crepitans) tadpole abundance was less in acidified macrocosms than in circumneutral ones (p < 0.05) and less in those with loam soils than in macrocosms with clay soils (p < 0.04). Gray treefrog (Hyla versicolor) abundance was affected by an interaction between soil and acidification (p < 0.07) in that treatment effects were only observed in macrocosms with clay soils (p < 0.01). No differences were observed among treatments for green frog (Rana clamitans) or southern leopard frog (R. utricularia) tadpoles. The study shows that soil type may interact with water conditions to affect amphibian populations in acidified waters

  10. When can embryos learn? A test of the timing of learning in embryonic amphibians.

    PubMed

    Sehr, Evie K; Beasley, Lindsay N; Wilson, Kurtis W; Gall, Brian G

    2016-04-01

    Learning is crucial to the survival of organisms across their life span, including during embryonic development. We set out to determine when learning becomes possible in amphibian development by exposing spotted salamander (Ambystoma maculatum) embryos to chemical stimuli from a predator (Ambystoma opacum), nonpredator (Lithobates clamitans), or control at developmental stages 16-21 or 36-38 (Harrison 1969). Once exposures were completed and embryos hatched, we recorded the number of movements and time spent moving of individuals in both groups and all treatments. There was no significant difference in number of movements or time spent moving among any of the treatments. The groups that were exposed to predator stimuli and a blank control at stages 36-38 were also tested to determine whether there was a difference in refuge preference or difference in survivorship when exposed to a predator (marbled salamander). There was no difference in survival or refuge preference between individuals; however, all individuals preferred vegetated over open areas regardless of treatment type. We discuss hypotheses for the absence of embryonic learning in this species and suggest it may be the result of the intensity of the predator-prey interaction between the predator, large marbled salamander larvae, and the prey, spotted salamander larvae. PMID:27110353

  11. Failure of tetracycline as a biomarker in batch-marking juvenile frogs

    USGS Publications Warehouse

    Hatfield, J.S.; Henry, P.F.P.; Olsen, G.H.; Paul, M.M.; Hammerschlag, R.S.

    2001-01-01

    Recent widespread amphibian declines call for better techniques to assess population dynamics. Tetracycline as a biomarker in capture-recapture studies is one technique used successfully in fish, reptiles, and mammals. A two-phase experimental study was conducted to evaluate tetracycline as a biomarker in green frogs (Rana clamitans) and pickerel frogs (Rana palustris). In the first experimental phase tadpoles were exposed to water containing either 250 mg/l or 500 mg/l tetracycline for a period of 24 hr. During the second phase, juvenile frogs were exposed to tetracycline in water at 500 mg/l or given injections of tetracycline at the dose rate of 100 mg/kg body weight. At selected times several weeks later, under tricaine methanesulfonate anesthesia, a toe was surgically excised from each animal, sectioned and viewed under an ultraviolet microscope. No significant differences were found between the various treatments and control animals (untreated). Therefore, the use of tetracycline as a biomarker in anurans using these techniques is not recommended.

  12. Naturally occurring variation in tadpole morphology and performance linked to predator regime

    PubMed Central

    Johnson, James B; Saenz, Daniel; Adams, Cory K; Hibbitts, Toby J

    2015-01-01

    Divergent natural selection drives a considerable amount of the phenotypic and genetic variation observed in natural populations. For example, variation in the predator community can generate conflicting selection on behavioral, life-history, morphological, and performance traits. Differences in predator regime can subsequently increase phenotypic and genetic variations in the population and result in the evolution of reproductive barriers (ecological speciation) or phenotypic plasticity. We evaluated morphology and swimming performance in field collected Bronze Frog larvae (Lithobates clamitans) in ponds dominated by predatory fish and those dominated by invertebrate predators. Based on previous experimental findings, we hypothesized that tadpoles from fish-dominated ponds would have small bodies, long tails, and large tail muscles and that these features would facilitate fast-start speed. We also expected to see increased tail fin depth (i.e., the tail-lure morphology) in tadpoles from invertebrate-dominated ponds. Our results support our expectations with respect to morphology in affecting swimming performance of tadpoles in fish-dominated ponds. Furthermore, it is likely that divergent natural selection is playing a role in the diversification on morphology and locomotor performance in this system. PMID:26357533

  13. Intraerythrocytic development of species of Hepatozoon infecting ranid frogs: evidence for convergence of life cycle characteristics among apicomplexans.

    PubMed

    Smith, T G; Kim, B; Hong, H; Desser, S S

    2000-06-01

    Intraerythrocytic development of the adeleorin apicomplexans Hepatozoon clamatae and Hepatozoon catesbianae were investigated in the bullfrog, Rana catesbeiana, the green frog, Rana clamitans melanota, and the Northern leopard frog, Rana pipiens. Merozoites emerging from hepatic meronts penetrated erythrocytes and underwent 1-3 rounds of binary fission to produce 2-8 merozoites. Following their release from infected erythrocytes, individual merozoites entered new cells and transformed into gamonts. Although this is the first report of intraerythrocytic development for a fully described species of Hepatozoon, a phylogenetic reanalysis of 11 species of Hepatozoon, 6 species representative of the 5 other hemogregarine taxa, 2 species of dactylosomatids, and 2 species of piroplasms, indicates that asexual reproduction of parasites within blood cells of vertebrates has arisen at least 3 times in the apicomplexan lineage that includes adeleorins and piroplasms. This method of asexual development, which is also observed in species of hemospororin genera such as Plasmodium, is discussed in the context of the evolution of apicomplexan life cycles. In addition to supporting the paraphyly of the genus Hepatozoon determined in an earlier study, this phylogenetic analysis featured a monophyletic group, consisting of the sister taxa Hemolivia and Karyolysus, that was the sister group to a clade consisting of the more derived hemogregarines, the dactylosomatids, and the piroplasms.

  14. The role of gamont entry into erythrocytes in the specificity of Hepatozoon species (Apicomplexa: Adeleida) for their frog hosts.

    PubMed

    Dickson, Cory M; Ogbuah, Christopher T; Smith, Todd G

    2013-12-01

    Hepatozoon species are apicomplexan parasites that infect blood cells and viscera of terrestrial vertebrates. One species, Hepatozoon clamatae, primarily infects green frogs, Rana clamitans , whereas another, Hepatozoon catesbianae, primarily infects bullfrogs, Rana catesbeiana , although both species of parasite are capable of infecting either species of frog. The aim of this study was to determine whether the basis for this partial host specificity is manifested at the gamont, or intraerythrocytic, stage of the parasite's life cycle. Blood was drawn from infected frogs and treated in vitro with a saline solution to induce intracellular gamonts to emerge from host erythrocytes. This treated blood was added to in vitro samples of uninfected blood of green frogs and bullfrogs. After 1 hr, samples were analyzed to determine the level of re-entry of the parasites into uninfected erythrocytes. Results obtained using multiple combinations of donor and recipient frogs indicate that extracellular gamonts of both parasite species do not exhibit preference for erythrocytes of 1 frog species over those of another. These results suggest that the basis for the observed host specificity is not determined at the gamont stage and is more likely dependent on another stage in the parasite life cycle.

  15. Phylogenetic relationships among Hepatozoon species from snakes, frogs and mosquitoes of Ontario, Canada, determined by ITS-1 nucleotide sequences and life-cycle, morphological and developmental characteristics.

    PubMed

    Smith, T G; Kim, B; Desser, S S

    1999-02-01

    The molecular biological characteristics of Hepatozoon species infecting various species of snakes, frogs and mosquitoes were investigated by determining the nucleotide sequences of the first internal transcribed spacer region. A phylogenetic analysis was performed on seven isolates of Hepatozoon infecting snakes, including Hepatozoon sipedon and four morphologically similar but not identical forms, and two isolates of Hepatozoon catesbianae infecting Green frogs (Rana clamitans melanota). This analysis, which utilised data from first internal transcribed spacer nucleotide sequences, morphological and morphometric features of gamonts, oocysts and sporocysts, and previously determined life-cycle and host-specificity characteristics, revealed that H. sipedon is a polymorphic species with a wide host and geographic range. Four synapomorphies. including two nucleotide substitutions and two morphological character state changes, supported a monophyletic group of six isolates of H. sipedon from the central region of Ontario which was the sister group for an isolate (HW1) from the southern part of the province. Based on the results of this study, an evaluation of which criteria are useful for describing species of Hepatozoon is presented, with the intent of curtailing the practice of naming species based on morphological features of gamonts or on incomplete life-cycle data.

  16. The role of habitat in structuring Halipegus occidualis metapopulations in the green frog.

    PubMed

    Zelmer, D A; Wetzel, E J; Esch, G W

    1999-02-01

    The transmission dynamics of the trematode Halipegus occidualis in its definitive host, Rana clamitans, have been examined over a 5-yr period in a North Carolina pond. The breeding season of green frogs coincides with the period of worm recruitment, during which time male frogs are territorial and females show strong site fidelity. This site fidelity allows inferences to be made regarding the suitability of a particular habitat for worm transmission based on frog infection intensities within that habitat. Four foci of infection were identified in the pond by plotting worm infrapopulation size against site of host capture. Sites within infection foci are characterized by shallow water and emergent vegetation, factors favorable for overlapping distributions of the 4 hosts in the life cycle of H. occidualis. Consistent year-to-year worm prevalences and intensities, despite fluctuations in frog population size, are thought to be the result of a relatively constant proportion of the frog population being present in infection foci each year. Removal of worms from heavily infected frogs in the fifth year resulted in further heavy worm recruitment by treated frogs suggesting that site selection can predispose a frog to heavy infection. Further, the sum of removed parasites and those recruited after parasite removal by treated frog hosts was higher than worm infrapopulations observed in previous years, indicating that worm density regulates parasite infrapopulation size in heavily infected frogs.

  17. Survivorship patterns of larval amphibians exposed to low concentrations of atrazine.

    PubMed

    Storrs, Sara I; Kiesecker, Joseph M

    2004-07-01

    Amphibians can be exposed to contaminants in nature by many routes, but perhaps the most likely route is agricultural runoff in amphibian breeding sites. This runoff results in high-level pulses of pesticides. For example, atrazine, the most widely used pesticide in the United States, can be present at several parts per million in agricultural runoff. However, pesticide levels are likely to remain in the environment at low levels for longer periods. Nevertheless, most studies designed to examine the impacts of contaminants are limited to short-term (approximately 4 days) tests conducted at relatively high concentrations. To investigate longer-term (approximately 30 days) exposure of amphibians to low pesticide levels, we exposed tadpoles of four species of frogs--spring peepers (Pseudacris crucifer), American toads (Bufo americanus, green frogs (Rana clamitans), and wood frogs (Rana sylvatica)--at early and late developmental stages to low concentrations of a commercial preparation of atrazine (3, 30, or 100 ppb; the U.S. Environmental Protection Agency drinking water standard is 3 ppb). We found counterintuitive patterns in rate of survivorship. Survival was significantly lower for all animals exposed to 3 ppb compared with either 30 or 100 ppb, except the late stages of B. americanus and R. sylvatica. These survival patterns highlight the importance of investigating the impacts of contaminants with realistic exposures and at various developmental stages. This may be particularly important for compounds that produce greater mortality at lower doses than higher doses, a pattern characteristic of many endocrine disruptors.

  18. Effects of atrazine on cercarial longevity, activity, and infectivity.

    PubMed

    Koprivnikar, Janet; Forbes, Mark R; Baker, Robert L

    2006-04-01

    Susceptibility of free-living infective stages of parasites to contaminants is relatively understudied compared with independent effects on measures of host health or immunity, but may be important in affecting prevalence and intensity of parasite infections. We investigated whether atrazine, an herbicide commonly used in North America, affected the cercariae of 4 different species of digenetic trematodes, and found that effects of atrazine concentration on mortality and activity of cercariae varied among species. Mortality of Echinostoma trivolvis increased in a 200 microg/L atrazine solution, and a species of Alaria showed both decreased activity and increased mortality. We also examined whether the ability of E. trivolvis to infect the second intermediate host, larval amphibians, was compromised by atrazine exposure. Longevity and prevalence of E. trivolvis cercariae was affected at 200 microg/L atrazine, whereas intensity of infection in Rana clamitans tadpoles was reduced at both 20 microg/L and 200 microg/L atrazine. Our results indicate that the viability of cercariae of some species is compromised by exposure to atrazine, emphasizing the importance of considering the influence of contaminants on free-living stages of parasites in addressing how environmental degradation may relate to host parasitism.

  19. Impact of atrazine on chlorpyrifos toxicity in four aquatic vertebrates.

    PubMed

    Wacksman, M N; Maul, J D; Lydy, M J

    2006-11-01

    Atrazine has been shown previously to potentiate chlorpyrifos toxicity in selected invertebrates. This study examined interactions of atrazine and chlorpyrifos in four aquatic vertebrates. Organisms were exposed to binary mixtures of atrazine and chlorpyrifos during toxicity bioassays. Inhibition of cholinesterase (ChE) enzyme activity and chlorpyrifos uptake kinetics were also examined with and without atrazine exposure. Atrazine alone did not affect organisms at concentrations up to 5000 microg/L; however, the presence of atrazine at 1000 microg/L did result in a significant increase in the acute toxicity of chlorpyrifos in Xenopus laevis. Mixed results were encountered with Pimephales promelas; some bioassays showed greater than additive toxicity, while others showed an additive response. No effect of atrazine on chlorpyrifos toxicity was observed for Lepomis macrochirus and Rana clamitans. Atrazine did not affect ChE activity or chlorpyrifos uptake rates, indicating that these toxicodynamic and toxicokinetic parameters may not be related to the mechanism of atrazine potentiation of chlorpyrifos toxicity. Based on the results of this study, it does not appear that a mixture toxicity of atrazine and chlorpyrifos at environmentally relevant concentrations presents a risk to the vertebrate organisms examined in this study.

  20. Patterns of Cranial Development in Larval Rana macrocnemis: Chondrocranial Size and Shape Relationship With Pelophylax bedriagae (Anura: Ranidae).

    PubMed

    Yildirim, Elıf; Kaya, Uğur

    2016-06-01

    Notwithstanding the abundance of amphibians, there are few descriptions about ranid cranial development. Herein, larval chondrocranial development of Uludağ frog, Rana macrocnemis (Boulenger, 1885), is described on cleared and double-stained specimens. Descriptions are related with the ontogeny of the chondrocranium and osteogenesis of the cranial skeleton. The larval chondrocranial development of R. macrocnemis is compared to those of Rana and Pelophylax larvae (Pelophylax bedriagae, Rana pipiens, R. palustris, R. sphenocephala, R. catesbeiana, R. clamitans and R. sylvatica). In R. macrocnemis, the first bones to ossify are the parasphenoid and exoccipital (Stage 33), followed by the frontoparietal and prootic (stages 35 and 40, respectively). The major reconstruction of the chondrocranium begins at Stage 41. The ossification sequence of R. macrocnemis is distinguished from other ranids. Adult cranial osteology of R. macrocnemis is compared to that of P. bedriagae. Osteologically, R. macrocnemis is different from P. bedriagae by the shape and size of the vomer and number of teeth. Additionally, geometric morphometric methods are used to analyze chondrocranial size and shape changes of ranid larva of R. macrocnemis and P. bedriagae. Anat Rec, 299:711-721, 2016. © 2016 Wiley Periodicals, Inc.

  1. Monitoring multiple species: Estimating state variables and exploring the efficacy of a monitoring program

    USGS Publications Warehouse

    Mattfeldt, S.D.; Bailey, L.L.; Grant, E.H.C.

    2009-01-01

    Monitoring programs have the potential to identify population declines and differentiate among the possible cause(s) of these declines. Recent criticisms regarding the design of monitoring programs have highlighted a failure to clearly state objectives and to address detectability and spatial sampling issues. Here, we incorporate these criticisms to design an efficient monitoring program whose goals are to determine environmental factors which influence the current distribution and measure change in distributions over time for a suite of amphibians. In designing the study we (1) specified a priori factors that may relate to occupancy, extinction, and colonization probabilities and (2) used the data collected (incorporating detectability) to address our scientific questions and adjust our sampling protocols. Our results highlight the role of wetland hydroperiod and other local covariates in the probability of amphibian occupancy. There was a change in overall occupancy probabilities for most species over the first three years of monitoring. Most colonization and extinction estimates were constant over time (years) and space (among wetlands), with one notable exception: local extinction probabilities for Rana clamitans were lower for wetlands with longer hydroperiods. We used information from the target system to generate scenarios of population change and gauge the ability of the current sampling to meet monitoring goals. Our results highlight the limitations of the current sampling design, emphasizing the need for long-term efforts, with periodic re-evaluation of the program in a framework that can inform management decisions.

  2. Mine-drainage treatment wetland as habitat for herptofaunal wildlife

    NASA Astrophysics Data System (ADS)

    Lacki, Michael J.; Hummer, Joseph W.; Webster, Harold J.

    1992-07-01

    Land reclamation techniques that incorporate habitat features for herptofaunal wildlife have received little attention. We assessed the suitability of a wetland, constructed for the treatment of mine-water drainage, for supporting herptofaunal wildlife from 1988 through 1990 using diurnal and nocturnal surveys. Natural wetlands within the surrounding watershed were also monitored for comparison. The treatment wetland supported the greatest abundance and species richness of herptofauna among the sites surveyed. Abundance was a function of the frog density, particularly green frogs ( Rana clamitans) and pickerel frogs ( R. palustris), while species richness was due to the number of snake species found. The rich mix of snake species present at the treatment wetland was believed due to a combination of an abundant frog prey base and an amply supply of den sites in rock debris left behind from earlier surface-mining activities. Nocturnal surveys of breeding male frogs demonstrated highest breeding activity at the treatment wetland, particularly for spring peepers ( Hyla crucifer). Whole-body assays of green frog and bullfrog ( R. catesbeiana) tissues showed no differences among sites in uptake of iron, aluminum, and zinc; managanese levels in samples from the treatment wetland were significantly lower than those from natural wetlands. These results suggest that wetlands established for water quality improvement can provide habitat for reptiles and amphibians, with the species composition dependent on the construction design, the proximity to source populations, and the degree of acidity and heavy-metal concentrations in drainage waters.

  3. The role of gamont entry into erythrocytes in the specificity of Hepatozoon species (Apicomplexa: Adeleida) for their frog hosts.

    PubMed

    Dickson, Cory M; Ogbuah, Christopher T; Smith, Todd G

    2013-12-01

    Hepatozoon species are apicomplexan parasites that infect blood cells and viscera of terrestrial vertebrates. One species, Hepatozoon clamatae, primarily infects green frogs, Rana clamitans , whereas another, Hepatozoon catesbianae, primarily infects bullfrogs, Rana catesbeiana , although both species of parasite are capable of infecting either species of frog. The aim of this study was to determine whether the basis for this partial host specificity is manifested at the gamont, or intraerythrocytic, stage of the parasite's life cycle. Blood was drawn from infected frogs and treated in vitro with a saline solution to induce intracellular gamonts to emerge from host erythrocytes. This treated blood was added to in vitro samples of uninfected blood of green frogs and bullfrogs. After 1 hr, samples were analyzed to determine the level of re-entry of the parasites into uninfected erythrocytes. Results obtained using multiple combinations of donor and recipient frogs indicate that extracellular gamonts of both parasite species do not exhibit preference for erythrocytes of 1 frog species over those of another. These results suggest that the basis for the observed host specificity is not determined at the gamont stage and is more likely dependent on another stage in the parasite life cycle. PMID:23829695

  4. Batrachochytrium dendrobatidis infection dynamics vary seasonally in upstate New York, USA.

    PubMed

    Lenker, Melissa A; Savage, Anna E; Becker, C Guilherme; Rodriguez, David; Zamudio, Kelly R

    2014-08-21

    The amphibian disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a major cause of worldwide amphibian declines and extinctions. Although several studies indicate that Bd prevalence and infection intensity vary seasonally, temporal variation of Bd at high-latitude sites, such as the northeastern USA, is still poorly characterized. We screened amphibians for Bd monthly at 2 study sites in New York State from April to October 2011 and used quantitative polymerase chain reaction (qPCR) to detect and quantify temporal variability in Bd infection prevalence and intensity. We found pronounced seasonal variation in both Bd infection prevalence and intensity at the community level, and our data indicate that this pattern is due to a few species (Lithobates catesbeianus, L. clamitans, and Notophthalmus viridescens) that drive temporal variability in disease dynamics. Amphibian body mass and sex were significant predictors of infection intensity but not infection prevalence. Understanding the temporal dynamics of Bd host-pathogen interactions provides important insight into regional, seasonal, and host-specific determinants of disease outbreaks. Further, our study elucidates the most relevant and informative timing for Bd surveys in temperate amphibian assemblages. Seasonal variation of infection dynamics suggests that Bd surveys from different sampling time points are not comparable, and summer surveys to evaluate chytridiomycosis may significantly underestimate Bd prevalence and intensity, leading to false conclusions about the severity of chytridiomycosis-induced amphibian mortality and population decline.

  5. The region of the Piedra Berroqueña: A potencial Global Heritage Stone Province.

    NASA Astrophysics Data System (ADS)

    Freire-Lista, David Martin; Fort, Rafael

    2015-04-01

    The Piedra Berroqueña region occupies an area of approximately 4000 km2 in the Sierra de Guadarrama, Spanish Central System, the centre of the Iberian Peninsula. This region has provided most of the building granites used in Madrid and surrounding provinces. Traditional methods of cutting and carving stone have been preserved and it is easy to locate historic quarries in its landscape in addition to mechanized quarries with large reserves of this dimension stone that is exported worldwide in the form of blocks or slabs with different finishes. The Piedra Berroqueña has been used as a building stone since before the Romans. Petrophysical and durability characteristics have allowed to endure monuments as representative as The Royal Monastery of San Lorenzo del Escorial (1563-1584), del Sol Gate (1857-1862), Royal Palace (1738-1764), Alcalá Gate (1770-1778) or Prado Museum (1785-1808) in Madrid, Spain. Also the Piedra Berroqueña is part of most residential buildings and streets of this city, as well as modern buildings around the world, such as airport terminals in Athens, Cork, the British consulate in Hong Kong and headquarters of banks in Jakarta, among others. Piedra Berroqueña province is presented in this abstract, which has many granite quarries with common characteristics such as their grey tones and the presence of darker enclaves "Gabarros or negrones". In the Piedra Berroqueña province four main types of granite can be distinguish: Peraluminous granites; with biotite and occasional cordierite, whose most representative historic quarries are in Alpedrete, Colmenar Viejo, El Boalo, El Berrocal and Collado Mediano. Biotite granites with occasional amphibole are present in historic quarries in El Berrueco, Lozoyuela-Navas-Sieteiglesias and Pelayo de la Presa, among others. Currently exploited in Valdemanco and La Cabrera and marketed under the commercial names of Aurora Blanco, Blanco Berrocal, Crema Champagne, Blanco Castilla, Crema Cabrera, Blanco Perla

  6. The significance of avulsion phenomena in the alluvial filling configuration of a mountain stream: Venero Claro (Central Spain)

    NASA Astrophysics Data System (ADS)

    Ruiz-Villanueva, V.; Díez-Herrero, A.; Bodoque, J. M.; Fernández-García, P.; Ballesteros, J. A.

    2009-04-01

    In the dynamics and evolution of large river floodplains, alluvial fans and debris cones, avulsion phenomena have been considered very important. However, traditionally, in mountain streams, avulsion phenomena have been underestimated because they are not very frequent, and usually they are restricted to little chute cut-off. Nevertheless, there are mountainous areas where the valley bottom gets wider, and the alluvial filling works like an elongated debris cone. The Cabrera Stream in the Venero Claro reach (Spanish Central System) is one of these special areas. In this case, avulsion phenomena took place triggered by flash floods, and they were usually associated with hyperconcentrated flows, which exceeded the upper level of levees and banks, redefining the sedimentary architecture of the alluvial filling. In this study, an analysis of geomorphologic and sedymentological evolution of the alluvial filling in Venero Claro have been carried out. On this way, cartography made from the 19th Century until ninety ages were compared, and a stereoscopic analysis of aerial photographs and digital ortoimages were applied. Furthermore, the sedimentary filling was studied applying classic sedimentological techniques, such as a description and interpretation of sedimentary structures and facies analysis at field. As a result of the geomorphologic evolution analysis, a straightforward evolution model is proposed. This model enhances the relevant importance of the avulsion phenomena in the geomorphologic configuration of the Cabrera Stream in the Venero Claro reach. From the river pattern point of view, the avulsion phenomena originate capture processes in the main stream and its tributaries. As a result of these processes, the drainage network pattern changes successively from dendritic to sub-parallel. On other hand, from the sedimentologic point of view, the stratigraphy is composed of channel facies (debris flow facies and fluvial-torrential gravelbars) and back

  7. Modeling And Economics Of Extreme Subduction Earthquakes: Two Case Studies

    NASA Astrophysics Data System (ADS)

    Chavez, M.; Cabrera, E.; Emerson, D.; Perea, N.; Moulinec, C.

    2008-05-01

    The destructive effects of large magnitude, thrust subduction superficial (TSS) earthquakes on Mexico City (MC) and Guadalajara (G) has been shown in the recent centuries. For example, the 7/04/1845 and the 19/09/1985, two TSS earthquakes occurred on the coast of the state of Guerrero and Michoacan, with Ms 7+ and 8.1. The economical losses for the later were of about 7 billion US dollars. Also, the largest Ms 8.2, instrumentally observed TSS earthquake in Mexico, occurred in the Colima-Jalisco region the 3/06/1932, and the 9/10/1995 another similar, Ms 7.4 event occurred in the same region, the later produced economical losses of hundreds of thousands US dollars.The frequency of occurrence of large TSS earthquakes in Mexico is poorly known, but it might vary from decades to centuries [1]. Therefore there is a lack of strong ground motions records for extreme TSS earthquakes in Mexico, which as mentioned above, recently had an important economical impact on MC and potentially could have it in G. In this work we obtained samples of broadband synthetics [2,3] expected in MC and G, associated to extreme (plausible) magnitude Mw 8.5, TSS scenario earthquakes, with epicenters in the so-called Guerrero gap and in the Colima-Jalisco zone, respectively. The economical impacts of the proposed extreme TSS earthquake scenarios for MC and G were considered as follows: For MC by using a risk acceptability criteria, the probabilities of exceedance of the maximum seismic responses of their construction stock under the assumed scenarios, and the estimated economical losses observed for the 19/09/1985 earthquake; and for G, by estimating the expected economical losses, based on the seismic vulnerability assessment of their construction stock under the extreme seismic scenario considered. ----------------------- [1] Nishenko S.P. and Singh SK, BSSA 77, 6, 1987 [2] Cabrera E., Chavez M., Madariaga R., Mai M, Frisenda M., Perea N., AGU, Fall Meeting, 2005 [3] Chavez M., Olsen K

  8. The response of amphibian larvae to exposure to a glyphosate-based herbicide (Roundup WeatherMax) and nutrient enrichment in an ecosystem experiment.

    PubMed

    Edge, Christopher; Thompson, Dean; Hao, Chunyan; Houlahan, Jeff

    2014-11-01

    Herbicides and fertilizers are widely used throughout the world and pose a threat to aquatic ecosystems. Using a replicated, whole ecosystem experiment in which 24 small wetlands were split in half with an impermeable barrier we tested whether exposure to a glyphosate-based herbicide, Roundup WeatherMax™, alone or in combination with nutrient enrichment has an effect on the survival, growth or development of amphibians. The herbicide was applied at one of two concentrations (low=210 μg a.e./L, high=2880 μg a.e./L) alone and in combination with nutrient enrichment to one side of wetlands and the other was left as an untreated control. Each treatment was replicated with six wetlands, and the experiment was repeated over two years. In the high glyphosate and nutrient enrichment treatment the survival of wood frog (Lithobates sylvaticus) larvae was lower in enclosures placed in situ on the treated sides than the control sides of wetlands. However, these results were not replicated in the second year of study and they were not observed in free swimming wood frog larvae in the wetlands. In all treatments, wood frog larvae on the treated sides of wetlands were slightly larger (<10%) than those on the control side, but no effect on development was observed. The most dramatic finding was that the abundance of green frog larvae (Lithobates clamitans) was higher on the treated sides than the control sides of wetlands in the herbicide and nutrient treatments during the second year of the study. The results observed in this field study indicate that caution is necessary when extrapolating results from artificial systems to predict effects in natural systems. In this experiment, the lack of toxicity to amphibian larvae was probably due to the fact the pH of the wetlands was relatively low and the presence of sediments and organic surfaces which would have mitigated the exposure duration.

  9. Heavy metal levels in ribbon snakes (Thamnophis sauritus) and anuran larvae from the Mobile-Tensaw River Delta, Alabama, USA.

    PubMed

    Albrecht, J; Abalos, M; Rice, T M

    2007-11-01

    The Mobile-Tensaw River Delta (MTD) drains more than 75% of the state of Alabama and leads into Mobile Bay and the Northern Gulf of Mexico. Although it is a relatively healthy watershed, the MTD is potentially impacted by inputs of contaminants such as heavy metals. The levels of lead, copper, cadmium, and mercury were measured in whole body samples of Eastern Ribbon Snakes (Thamnophis sauritus) collected from the MTD. Lead, copper, and cadmium levels were also measured in anuran larvae (Rana catesbeiana, R. clamitans, and Hyla cinerea). These organisms were chosen because they are abundant in the MTD and are underrepresented in environmental contaminant biomonitoring studies. Ribbon snakes had significantly lower levels of lead, copper, and cadmium compared to whole body levels in anuran larvae, indicating that these metals were not biomagnifying through upper trophic levels. Copper and mercury levels were significantly correlated with age/growth indices in ribbon snakes. Although detectable levels of all metals were found in anuran larvae and ribbon snakes, these levels appear to be less than body burdens that would be associated with toxic effects. Populations of ribbon snakes in our particular collection sites within the MTD appear to be at minimal risk of exposure to toxic levels of metals. However, the MTD contains low- and high-impact areas, and other populations within this watershed could be at higher risk of exposure to heavy metals. We found the Eastern Ribbon Snake to be an excellent snake model for contaminant biomonitoring because of its abundance, reasonable size, and ease of collection.

  10. Trichobothrial mediation of an aquatic escape response: directional jumps by the fishing spider, Dolomedes triton, foil frog attacks.

    PubMed

    Suter, Robert B

    2003-01-01

    Fishing spiders (Pisauridae) frequent the surfaces of ponds and streams and thereby expose themselves to predation by a variety of aquatic and semi-aquatic vertebrates. To assess the possibility that the impressive jumps of fishing spiders from the water surface function in evading attacks by frogs, attacks by bullfrogs (Rana catesbiana) and green frogs (R. clamitans) on Dolomedes triton were studied. Both the attack dynamics of the frogs and the evasive behaviors of the spiders were recorded at 250 frames per second. A freeze-dried bullfrog, propelled toward spiders with acceleration, posture, and position that approximated the natural attack posture and dynamics, was used to assess the spiders' behavior. Qualitatively, the spiders responded to these mock-attacks just as they had to attacks by live frogs: jumping (N=29 jumps, 56.9% of instances), rearing the legs nearest the attacking frog (N=15, 29.4%), or showing no visible response (N=7, 13.7%). Spiders that jumped always did so away (in the vertical plane) from the attack (mean =137 degrees vs. vertical at 90 degrees or horizontally toward the frog at 0 degrees ). The involvement of the trichobothria (leg hairs sensitive to air movements), and the eyes as sensory mediators of the evasion response was assessed. Spiders with deactivated trichobothria were significantly impaired relative to intact and sham-deactivated spiders, and relative to spiders in total darkness. Thus, functional trichobothria, unlike the eyes, are both necessary and sufficient mediators of the evasion response. Measurements of air flow during frog attacks suggest that an exponential rise in flow velocity is the airborne signature of an attack. PMID:15841235

  11. Frog virus 3 prevalence in tadpole populations inhabiting cattle-access and non-access wetlands in Tennessee, USA.

    PubMed

    Gray, Matthew J; Miller, Debra L; Schmutzer, A Chandler; Baldwin, Charles A

    2007-09-14

    Ranaviruses have been associated with most of the reported larval anuran die-offs in the United States. It is hypothesized that anthropogenically induced stress may increase pathogen prevalence in amphibian populations by compromising immunity. Cattle use of wetlands may stress resident tadpole populations by reducing water quality. We isolated a Ranavirus from green frog Rana clamitans (n = 80) and American bullfrog R. catesbeiana (n = 104) tadpoles collected at 5 cattle-access and 3 non-access wetlands on the Cumberland Plateau, Tennessee, USA. Sequencing confirmed Frog virus 3 (FV3); therefore, we compared its prevalence between tadpole populations inhabiting cattle-access and non-access wetlands, and among 3 seasons (winter, summer, and autumn) in 2005. We found FV3 in both tadpole species and cattle land-use types; however, prevalence of FV3 was greater in green frog tadpoles residing in cattle-access wetlands compared to those in non-access wetlands. No difference in FV3 prevalence was detected between cattle land uses for American bullfrog tadpoles. A seasonal trend in FV3 prevalence also existed, with prevalence greater in autumn and winter than in summer for both species. In addition, we found that FV3 prevalence decreased significantly as Gosner stage increased in American bullfrog tadpoles. No trend was detected between FV3 prevalence and developmental stage for green frog tadpoles. Our results suggest that cattle use of wetlands may increase prevalence of FV3 in Rana tadpoles, although this effect may depend on species, season, and tadpole developmental stage. PMID:17972750

  12. Relative toxicity of the components of the original formulation of Roundup to five North American anurans.

    PubMed

    Moore, Lindsay J; Fuentes, Latice; Rodgers, John H; Bowerman, William W; Yarrow, Greg K; Chao, Wayne Y; Bridges, William C

    2012-04-01

    The responses of five North American frog species that were exposed in an aqueous system to the original formulation of Roundup were compared. Carefully designed and un-confounded laboratory toxicity tests are crucial for accurate assessment of potential risks from the original formulation of Roundup to North American amphibians in aquatic environments. The formulated mixture of this herbicide as well as its components, isopropylamine (IPA) salt of glyphosate and the surfactant MON 0818 (containing polyethoxylated tallowamine (POEA)) were separately tested in 96 h acute toxicity tests with Gosner stage 25 larval anurans. Rana pipiens, R. clamitans, R. catesbeiana, Bufo fowleri, and Hyla chrysoscelis were reared from egg masses and exposed to a series of 11 concentrations of the original formulation of Roundup herbicide, nine concentrations of MON 0818 and three concentrations of IPA salt of glyphosate in static (non-renewal) aqueous laboratory tests. LC50 values are expressed as glyphosate acid equivalents (ae) or as mg/L for MON 0818 concentrations for comparison between the formulation and components. R. pipiens was the most sensitive of five species with 96 h-LC50 values for formulation tests, for the five species, ranging from 1.80 to 4.22 mg ae/L, and MON 0818 exposures with 96 h-LC50 values ranging from 0.68 to 1.32 mg/L. No significant mortality was observed during exposures of 96 h for any of the five species exposed to glyphosate IPA salt at concentrations up to 100 times the predicted environmental concentration (PEC). These results agree with previous studies which have noted that the surfactant MON 0818 containing POEA contributes the majority of the toxicity to the herbicide formulations for fish, aquatic invertebrates, and amphibians. These study results suggest that anurans are among the most sensitive species, and emphasize the importance of testing the herbicide formulation in addition to its separate components to accurately characterize the

  13. The response of amphibian larvae to exposure to a glyphosate-based herbicide (Roundup WeatherMax) and nutrient enrichment in an ecosystem experiment.

    PubMed

    Edge, Christopher; Thompson, Dean; Hao, Chunyan; Houlahan, Jeff

    2014-11-01

    Herbicides and fertilizers are widely used throughout the world and pose a threat to aquatic ecosystems. Using a replicated, whole ecosystem experiment in which 24 small wetlands were split in half with an impermeable barrier we tested whether exposure to a glyphosate-based herbicide, Roundup WeatherMax™, alone or in combination with nutrient enrichment has an effect on the survival, growth or development of amphibians. The herbicide was applied at one of two concentrations (low=210 μg a.e./L, high=2880 μg a.e./L) alone and in combination with nutrient enrichment to one side of wetlands and the other was left as an untreated control. Each treatment was replicated with six wetlands, and the experiment was repeated over two years. In the high glyphosate and nutrient enrichment treatment the survival of wood frog (Lithobates sylvaticus) larvae was lower in enclosures placed in situ on the treated sides than the control sides of wetlands. However, these results were not replicated in the second year of study and they were not observed in free swimming wood frog larvae in the wetlands. In all treatments, wood frog larvae on the treated sides of wetlands were slightly larger (<10%) than those on the control side, but no effect on development was observed. The most dramatic finding was that the abundance of green frog larvae (Lithobates clamitans) was higher on the treated sides than the control sides of wetlands in the herbicide and nutrient treatments during the second year of the study. The results observed in this field study indicate that caution is necessary when extrapolating results from artificial systems to predict effects in natural systems. In this experiment, the lack of toxicity to amphibian larvae was probably due to the fact the pH of the wetlands was relatively low and the presence of sediments and organic surfaces which would have mitigated the exposure duration. PMID:25173748

  14. Interactions of an insecticide with competition and pond drying in amphibian communities

    USGS Publications Warehouse

    Boone, M.D.; Semlitsch, R.D.

    2002-01-01

    Amphibian populations are often imbedded in agricultural landscapes. Therefore the potential for contamination of their habitat is considerable. Our study examined the effects of an insecticide (carbaryl, a neurotoxin), on larval amphibian communities experiencing natural stresses of competition for resources, predation, and pond drying. In a set of experimental ponds, tadpoles of three anuran species (southern leopard frog [Rana sphenocephala], plains leopard frog [R. blairi], and the Woodhouse's toad [Bufo woodhousii]) were added to 1000-L ponds containing leaf litter, plankton, two newts (Notophthalmus viridescens), and four overwintered green frog (R. clamitans) tadpoles. We manipulated the overall tadpole density (low or high), pond hydroperiod (constant or drying), and chemical exposure (0, 3.5, 5.0, or 7.0 mg/L carbaryl) of the ponds. We measured mass, time, and survival to metamorphosis to determine treatment effects. Carbaryl positively affected Woodhouse's toad survival, although it had a negligible effect on both leopard frog species. Tadpole density interacted with the chemical treatment: Proportionately more Woodhouse's toads survived to metamorphosis in high-density environments than in low-density or control environments. Greater survival may be an indirect effect of increased algal food resources from carbaryl exposure. Most newts lost mass over the course of the experiment, although ponds with drying hydroperiods and high anuran density were the least favorable environments. Overwintered green frogs exposed to carbaryl had longer larval periods on average than did green frogs in control ponds. Our study demonstrated that even sublethal, short-lived contaminants can alter natural communities in ways that cannot be predicted from simple, one-factor studies.

  15. Disease dynamics of red-spotted newts and their anuran prey in a montane pond community.

    PubMed

    Rothermel, Betsie B; Miller, Debra L; Travis, Emilie R; Gonynor McGuire, Jessica L; Jensen, John B; Yabsley, Michael J

    2016-02-25

    Long-term monitoring of amphibians is needed to clarify population-level effects of ranaviruses (Rv) and the fungal pathogen Batrachochytrium dendrobatidis (Bd). We investigated disease dynamics of co-occurring amphibian species and potential demographic consequences of Rv and Bd infections at a montane site in the Southern Appalachians, Georgia, USA. Our 3-yr study was unique in combining disease surveillance with intensive population monitoring at a site where both pathogens are present. We detected sub-clinical Bd infections in larval and adult red-spotted newts Notophthalmus viridescens viridescens, but found no effect of Bd on body condition of adult newts. Bd infections also occurred in larvae of 5 anuran species that bred in our fishless study pond, and we detected co-infections with Bd and Rv in adult newts and larval green frogs Lithobates clamitans. However, all mortality and clinical signs in adult newts and larval anurans were most consistent with ranaviral disease, including a die-off of larval wood frogs Lithobates sylvaticus in small fish ponds located near our main study pond. During 2 yr of drift fence monitoring, we documented high juvenile production in newts, green frogs and American bullfrogs L. catesbeianus, but saw no evidence of juvenile recruitment in wood frogs. Larvae of this susceptible species may have suffered high mortality in the presence of both Rv and predators. Our findings were generally consistent with results of Rv-exposure experiments and support the purported role of red-spotted newts, green frogs, and American bullfrogs as common reservoirs for Bd and/or Rv in permanent and semi-permanent wetlands.

  16. Chytridiomycosis widespread in Anurans of Northeastern United States

    USGS Publications Warehouse

    Longcore, J.R.; Longcore, J.E.; Pessier, Allan P.; Halteman, W.A.

    2007-01-01

    An emerging disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis has been associated with morbidity, mortality, and extinction of species. Typically, researchers have detected B. dendrobatidis only when examining amphibians for causes of mortalities; few data exist on infection rates where mortalities are lacking. During May?September 2000?2002 we obtained amphibian specimens killed by vehicles and others collected at remote off-road sites throughout Maine, USA, and from federal lands in 5 states in the Northeast. We detected infected specimens, mostly green frogs (Rana clamitans), at 5 of 7 national wildlife refuges, a federal waterfowl production area, and Acadia National Park. Seven of 9 species, including all Ranidae species, were infected throughout Maine; rates ranged from 14.6% in American toads (Bufo americanus) to 25.7% in northern leopard frogs (Rana pipiens). We did not detect any infections in 50 eastern gray tree frogs (Hyla versicolor) or 21 spring peepers (Pseudacris crucifer). Species that hibernate in terrestrial habitats seem to have lower rates of infection than species that hibernate in aquatic habitats. Infections peaked in spring and autumn and were associated with air temperatures optimal for B. dendrobatidis growth. The relatively high infection rates among species without documented die-offs suggest that either losses have occurred undetected, that the fungus is endemic and species have attained a level of resistance to infections becoming lethal, or that climatic conditions of the Northeast have a role in preventing infections from being lethal. Data on prevalence and distribution of this chytrid fungus in the Northeast may be useful in modeling its origins and predicting long-term ecosystem effects involving anurans.

  17. Relative toxicity of the components of the original formulation of Roundup to five North American anurans.

    PubMed

    Moore, Lindsay J; Fuentes, Latice; Rodgers, John H; Bowerman, William W; Yarrow, Greg K; Chao, Wayne Y; Bridges, William C

    2012-04-01

    The responses of five North American frog species that were exposed in an aqueous system to the original formulation of Roundup were compared. Carefully designed and un-confounded laboratory toxicity tests are crucial for accurate assessment of potential risks from the original formulation of Roundup to North American amphibians in aquatic environments. The formulated mixture of this herbicide as well as its components, isopropylamine (IPA) salt of glyphosate and the surfactant MON 0818 (containing polyethoxylated tallowamine (POEA)) were separately tested in 96 h acute toxicity tests with Gosner stage 25 larval anurans. Rana pipiens, R. clamitans, R. catesbeiana, Bufo fowleri, and Hyla chrysoscelis were reared from egg masses and exposed to a series of 11 concentrations of the original formulation of Roundup herbicide, nine concentrations of MON 0818 and three concentrations of IPA salt of glyphosate in static (non-renewal) aqueous laboratory tests. LC50 values are expressed as glyphosate acid equivalents (ae) or as mg/L for MON 0818 concentrations for comparison between the formulation and components. R. pipiens was the most sensitive of five species with 96 h-LC50 values for formulation tests, for the five species, ranging from 1.80 to 4.22 mg ae/L, and MON 0818 exposures with 96 h-LC50 values ranging from 0.68 to 1.32 mg/L. No significant mortality was observed during exposures of 96 h for any of the five species exposed to glyphosate IPA salt at concentrations up to 100 times the predicted environmental concentration (PEC). These results agree with previous studies which have noted that the surfactant MON 0818 containing POEA contributes the majority of the toxicity to the herbicide formulations for fish, aquatic invertebrates, and amphibians. These study results suggest that anurans are among the most sensitive species, and emphasize the importance of testing the herbicide formulation in addition to its separate components to accurately characterize the

  18. Comparative toxicity of two glyphosate formulations (original formulation of Roundup® and Roundup WeatherMAX®) to six North American larval anurans.

    PubMed

    Fuentes, Latice; Moore, Lindsay J; Rodgers, John H; Bowerman, William W; Yarrow, Gregory K; Chao, Wayne Y

    2011-12-01

    The toxicity of two glyphosate formulations (the original formulation of Roundup® and Roundup WeatherMAX®) to six species of North American larval anurans was evaluated by using 96-h static, nonrenewal aqueous exposures. The 96-h median lethal concentration values (LC50) ranged from 1.80 to 4.22 mg acid equivalent (ae)/L and 1.96 to 3.26 mg ae/L for the original formulation of Roundup and Roundup WeatherMAX, respectively. Judged by LC50 values, four species were more sensitive to Roundup WeatherMAX exposures, and two species were more sensitive to the original formulation. Two of six species, Bufo fowleri (p < 0.05, F = 14.89, degrees of freedom [df] = 1) and Rana clamitans (p < 0.05, F = 18.46, df = 1), had significantly different responses to the two formulations tested. Increased sensitivity to Roundup WeatherMAX likely was due to differences in the surfactants or relative amounts of the surfactants in the two formulations. Potency slopes for exposures of the original formulation ranged from 24.3 to 92.5% mortality/mg ae/L. Thresholds ranged from 1.31 to 3.68 mg ae/L, showing an approximately three times difference in the initiation of response among species tested. For exposures of Roundup WeatherMAX, slopes ranged from 49.3 to 84.2% mortality/mg ae/L. Thresholds ranged from 0.83 to 2.68 mg ae/L. Margins of safety derived from a simulated direct overspray were above 1, except for one species in exposures of Roundup WeatherMAX. Laboratory data based on aqueous exposures are conservative because of the lack of environmental ligands; however, these tests provide information regarding the relative toxicity between these two Roundup formulations.

  19. Estimating occupancy dynamics in an anuran assemblage from Louisiana, USA

    USGS Publications Warehouse

    Walls, Susan C.; Waddle, J. Hardin; Dorazio, Robert M.

    2011-01-01

    Effective monitoring programs are designed to track changes in the distribution, occurrence, and abundance of species. We developed an extension of Royle and Kéry's (2007) single species model to estimate simultaneously temporal changes in probabilities of detection, occupancy, colonization, extinction, and species turnover using data on calling anuran amphibians, collected from 2002 to 2006 in the Lower Mississippi Alluvial Valley of Louisiana, USA. During our 5-year study, estimates of occurrence probabilities declined for all 12 species detected. These declines occurred primarily in conjunction with variation in estimates of local extinction probabilities (cajun chorus frog [Pseudacris fouquettei], spring peeper [P. crucifer], northern cricket frog [Acris crepitans], Cope's gray treefrog [Hyla chrysoscelis], green treefrog [H. cinerea], squirrel treefrog [H. squirella], southern leopard frog [Lithobates sphenocephalus], bronze frog [L. clamitans], American bullfrog [L. catesbeianus], and Fowler's toad [Anaxyrus fowleri]). For 2 species (eastern narrowmouthed toad [Gastrophryne carolinensis] and Gulf Coast toad [Incilius nebulifer]), declines in occupancy appeared to be a consequence of both increased local extinction and decreased colonization events. The eastern narrow-mouthed toad experienced a 2.5-fold increase in estimates of occupancy in 2004, possibly because of the high amount of rainfall received during that year, along with a decrease in extinction and increase in colonization of new sites between 2003 and 2004. Our model can be incorporated into monitoring programs to estimate simultaneously the occupancy dynamics for multiple species that show similar responses to ecological conditions. It will likely be an important asset for those monitoring programs that employ the same methods to sample assemblages of ecologically similar species, including those that are rare. By combining information from multiple species to decrease the variance on estimates

  20. Landscape associations of frog and toad species in Iowa and Wisconsin, U.S.A

    USGS Publications Warehouse

    Knutson, M.G.; Sauer, J.R.; Olsen, D.A.; Mossman, M.J.; Hemesath, L.M.; Lannoo, M.J.; Kaiser, Hinrich; Casper, Gary S.; Bernstein, Neil P.

    2000-01-01

    Landscape habitat associations of frogs and toads in Iowa and Wisconsin were tested to determine whether they support or refute previous general habitat classifications. We examined which Midwestern species shared similar habitats to see if these associations were consistent across large geographic areas (states). Rana sylvatica (wood frog), Hyla versicolor (eastern gray treefrog), Pseudacris crucifer (spring peeper), and Acris crepitans (cricket frog) were identified as forest species, P. triseriata (chorus frog), H. chrysoscelis (Cope's gray treefrog), R. pipiens (leopard frog), and Bufo americanus (American toad) as grassland species, and R. catesbeiana (bullfrog), R. clamitans (green frog), R. palustris (pickerel frog), and R. septentrionalis (mink frog) as lake or stream species. The best candidates to serve as bioindicators of habitat quality were the forest species R. sylvatica, H. versicolor, and P. crucifer, the grassland species R. pipiens and P. triseriata, and a cold water wetland species, R. palustris. Declines of P. crucifer, R. pipiens, and R. palustris populations in one or both states may reflect changes in habitat quality. Habitat and community associations of some species differed between states, indicating that these relationships may change across the range of a species. Acris crepitans may have shifted its habitat affinities from open habitats, recorded historically, to the more forested habitat associations we recorded. We suggest contaminants deserve more investigation regarding the abrupt and widespread declines of this species. Interspersion of different habitat types was positively associated with several species. A larger number of wetland patches may increase breeding opportunities and increase the probability of at least one site being suitable. We noted consistently negative associations between anuran species and urban development. Given the current trend of urban growth and increasing density of the human population, declines of

  1. Prevalence of Batrachochytrium dendrobatidis in three species of wild frogs on Prince Edward Island, Canada.

    PubMed

    Forzán, M J; Vanderstichel, R; Hogan, N S; Teather, K; Wood, J

    2010-09-01

    Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has resulted in the decline or extinction of approximately 200 frog species worldwide. It has been reported throughout much of North America, but its presence on Prince Edward Island (PEI), on the eastern coast of Canada, was unknown. To determine the presence and prevalence of Bd on PEI, skin swabs were collected from 115 frogs from 18 separate sites across the province during the summer of 2009. The swabs were tested through single round end-point PCR for the presence of Bd DNA. Thirty-one frogs were positive, including 25/93 (27%) green frogs Lithobates (Rana) clamitans, 5/20 (25%) northern leopard frogs L. (R.) pipiens, and 1/2 (50%) wood frogs L. sylvaticus (formerly R. sylvatica); 12 of the 18 (67%) sites had at least 1 positive frog. The overall prevalence of Bd infection was estimated at 26.9% (7.2-46.7%, 95% CI). Prevalence amongst green frogs and leopard frogs was similar, but green frogs had a stronger PCR signal when compared to leopard frogs, regardless of age (p < 0.001) and body length (p = 0.476). Amongst green frogs, juveniles were more frequently positive than adults (p = 0.001). Green frogs may be the most reliable species to sample when looking for Bd in eastern North America. The 1 wood frog positive for Bd was found dead from chytridiomycosis; none of the other frogs that were positive for Bd by PCR showed any obvious signs of illness. Further monitoring will be required to determine what effect Bd infection has on amphibian population health on PEI.

  2. First survey for the amphibian chytrid fungus Batrachochytrium dendrobatidis in Connecticut (USA) finds widespread prevalence.

    PubMed

    Richards-Hrdlicka, Kathryn L; Richardson, Jonathan L; Mohabir, Leon

    2013-02-28

    The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) is an emerging infectious fungal pathogen of amphibians and is linked to global population declines. Until now, there has only been 1 survey for the fungus in the northeastern USA, which focused primarily on northern New England. We tested for Bd in a large number of samples (916 individuals from 116 sites) collected throughout the state of Connecticut, representing 18 native amphibian species. In addition, 239 preserved wood frog Lithobates sylvaticus tadpoles from throughout the state were screened for the fungus. Bd presence was assessed in both the fresh field swabs and the preserved samples using a sensitive quantitative PCR assay. Our contemporary survey found widespread Bd prevalence throughout Connecticut, occurring in 14 species and in 28% of all sampled animals. No preserved L. sylvaticus specimens tested positive for the fungus. Two common species, bullfrogs R. catesbeiana and green frogs R. clamitans had particularly high infection rates (0.21-0.39 and 0.33-0.42, respectively), and given their wide distribution throughout the state, we suggest they may serve as sentinels for Bd occurrence in this region. Further analyses found that several other factors increase the likelihood of infection, including life stage, host sex, and host family. Within sites, ponds with ranids, especially green frogs, increased the likelihood of Bd prevalence. By studying Bd in populations not facing mass declines, the results from this study are an important contribution to our understanding of how some amphibian species and populations remain infected yet exhibit no signs of chytridiomycosis even when Bd is widely distributed.

  3. Picillo Farm ecological risk assessment

    SciTech Connect

    Rury, P.M.; Turton, D.J.

    1995-12-31

    Under the direction of US Environmental Protection Agency, Region 1, a baseline ecological risk assessment (ERA) was conducted for terrestrial, wetland, and aquatic ecosystems located on-site and off-site/downstream of a Superfund site in Coventry, Rhode Island. Surveys of biota and ecosystems were focused in the vicinity of 26 soil, sediment, and surface water sampling locations used for the RI/FS site contamination assessment, to cross-link data on biological receptors to site-specific habitat maps. Classes of contaminants of concern (COCs), selected independently for each medium based on exceedances of ecotoxicity criteria, for which risks to one or more indicator communities and species were calculated, included VOCs, SVOCs, metals, PCBs and pesticides. Simple hazard quotients were used to estimate risks for benthic and pelagic communities of the aquatic and wetland exposure zones, using AWQC and NOAA sediment guidelines. These aquatic criteria also were applied to a site-specific exposure models for all life stages of the Green Frog (Rana clamitans). To complement the benthic invertebrate risk estimates, site-derived sediments also were used for toxicity tests of Chironomus tentans and Hyalella azteca. Published, species-specific and/or extrapolated toxicity effects endpoints were used in site-specific, mathematical food chain exposure assessment models for the Amedcan Woodcock (Scolopax minor), Short-tailed Shrew (Blarina brevicauda) and Mink (Mustela vison), to estimate organismal risks for a variety of foraging scenarios within one or more exposure zone. Incremental site contributions to risks from metals were inferred using local background data, whereas all risks from organic compounds were assumed to be site-derived.

  4. Host and parasite thermal acclimation responses depend on the stage of infection.

    PubMed

    Altman, Karie A; Paull, Sara H; Johnson, Pieter T J; Golembieski, Michelle N; Stephens, Jeffrey P; LaFonte, Bryan E; Raffel, Thomas R

    2016-07-01

    Global climate change is expected to alter patterns of temperature variability, which could influence species interactions including parasitism. Species interactions can be difficult to predict in variable-temperature environments because of thermal acclimation responses, i.e. physiological changes that allow organisms to adjust to a new temperature following a temperature shift. The goal of this study was to determine how thermal acclimation influences host resistance to infection and to test for parasite acclimation responses, which might differ from host responses in important ways. We tested predictions of three, non-mutually exclusive hypotheses regarding thermal acclimation effects on infection of green frog tadpoles (Lithobates clamitans) by the trematode parasite Ribeiroia ondatrae with fully replicated controlled-temperature experiments. Trematodes or tadpoles were independently acclimated to a range of 'acclimation temperatures' prior to shifting them to new 'performance temperatures' for experimental infections. Trematodes that were acclimated to intermediate temperatures (19-22 °C) had greater encystment success across temperatures than either cold- or warm-acclimated trematodes. However, host acclimation responses varied depending on the stage of infection (encystment vs. clearance): warm- (22-28 °C) and cold-acclimated (13-19 °C) tadpoles had fewer parasites encyst at warm and cold performance temperatures, respectively, whereas intermediate-acclimated tadpoles (19-25 °C) cleared the greatest proportion of parasites in the week following exposure. These results suggest that tadpoles use different immune mechanisms to resist different stages of trematode infection, and that each set of mechanisms has unique responses to temperature variability. Our results highlight the importance of considering thermal responses of both parasites and hosts when predicting disease patterns in variable-temperature environments. PMID:27040618

  5. Disease dynamics of red-spotted newts and their anuran prey in a montane pond community.

    PubMed

    Rothermel, Betsie B; Miller, Debra L; Travis, Emilie R; Gonynor McGuire, Jessica L; Jensen, John B; Yabsley, Michael J

    2016-02-25

    Long-term monitoring of amphibians is needed to clarify population-level effects of ranaviruses (Rv) and the fungal pathogen Batrachochytrium dendrobatidis (Bd). We investigated disease dynamics of co-occurring amphibian species and potential demographic consequences of Rv and Bd infections at a montane site in the Southern Appalachians, Georgia, USA. Our 3-yr study was unique in combining disease surveillance with intensive population monitoring at a site where both pathogens are present. We detected sub-clinical Bd infections in larval and adult red-spotted newts Notophthalmus viridescens viridescens, but found no effect of Bd on body condition of adult newts. Bd infections also occurred in larvae of 5 anuran species that bred in our fishless study pond, and we detected co-infections with Bd and Rv in adult newts and larval green frogs Lithobates clamitans. However, all mortality and clinical signs in adult newts and larval anurans were most consistent with ranaviral disease, including a die-off of larval wood frogs Lithobates sylvaticus in small fish ponds located near our main study pond. During 2 yr of drift fence monitoring, we documented high juvenile production in newts, green frogs and American bullfrogs L. catesbeianus, but saw no evidence of juvenile recruitment in wood frogs. Larvae of this susceptible species may have suffered high mortality in the presence of both Rv and predators. Our findings were generally consistent with results of Rv-exposure experiments and support the purported role of red-spotted newts, green frogs, and American bullfrogs as common reservoirs for Bd and/or Rv in permanent and semi-permanent wetlands. PMID:26912042

  6. Atrazine concentrations, gonadal gross morphology and histology in ranid frogs collected in Michigan agricultural areas.

    PubMed

    Murphy, M B; Hecker, M; Coady, K K; Tompsett, A R; Jones, P D; Du Preez, L H; Everson, G J; Solomon, K R; Carr, J A; Smith, E E; Kendall, R J; Van Der Kraak, G; Giesy, J P

    2006-03-10

    The triazine herbicide atrazine has been suggested to be a potential disruptor of normal sexual development in male frogs. The goals of this study were to collect native ranid frogs from sites in agricultural and non-agricultural areas and determine whether hypothesised atrazine effects on the gonads could be observed at the gross morphological and histological levels. Juvenile and adult green frogs (Rana clamitans), bullfrogs (R. catesbeiana) and leopard frogs (R. pipiens) were collected in the summers of 2002 and 2003. Atrazine concentrations were below the limit of quantification at non-agricultural sites, and concentrations did not exceed 2 microg/L at most agricultural sites. One concentration greater than 200 microg atrazine/L was measured once at one site in 2002. Hermaphroditic individuals with both male and female gonad tissue in either one or both gonads, were found at a low incidence at both non-agricultural and agricultural sites, and in both adults and juveniles. Testicular oocytes (TO) were found in male frogs at most of the sites, with the greatest incidence occurring in juvenile leopard frogs. TO incidence was not significantly different between agricultural and non-agricultural sites with the exception of juveniles collected in 2003. Atrazine concentrations were not significantly correlated with the incidence of hermaphroditism, but maximum atrazine concentrations were correlated with TO incidence in juvenile frogs in 2003. However, given the lack of a consistent relationship between atrazine concentrations and TO incidence, it is more likely the TOs observed in this study result from natural processes in development rather than atrazine exposure.

  7. Plasma steroid hormone concentrations, aromatase activities and GSI in ranid frogs collected from agricultural and non-agricultural sites in Michigan (USA).

    PubMed

    Murphy, M B; Hecker, M; Coady, K K; Tompsett, A R; Higley, E B; Jones, P D; Du Preez, L H; Solomon, K R; Carr, J A; Smith, E E; Kendall, R J; Van Der Kraak, G; Giesy, J P

    2006-05-01

    The triazine herbicide atrazine has been hypothesized to disrupt sexual development in frogs by up-regulating aromatase activity, resulting in greater estradiol (E2) concentrations and causing feminization in males. The goal of this study was to collect native ranid frogs from atrazine-exposed ponds and determine whether relationships exist between measured atrazine concentrations and the gonadosomatic index (GSI), plasma concentrations of testosterone (T), E2 or 11-ketotestosterone (KT), or with aromatase activity. In the summer of 2002 and 2003, adult and juvenile green frogs (Rana clamitans), bullfrogs (R. catesbeiana) and Northern leopard frogs (R. pipiens) were collected from areas with extensive corn cultivation and areas where there was little agricultural activity in south-central Michigan. Atrazine concentrations were below the limit of quantification at non-agricultural sites. Atrazine concentrations did not exceed 2 microg/L at most agricultural sites, but a concentration of 250 microg atrazine/L was measured in one sample from one site in 2002. Plasma steroid concentrations varied among locations. Aromatase activity was measurable in less than 11% of testes in adult males, and in less than 4% of testes in juvenile males. Median aromatase activities in ovaries of adult females ranged from 3 to 245 pmol/h/mg protein, and maximum activities were 2.5-fold greater in juveniles than in adults. Atrazine concentrations were not significantly correlated with any of the parameters measured in this study. These results indicate that atrazine does not up-regulate aromatase in green frogs in the wild, and does not appear to affect plasma steroid hormone concentrations.

  8. First survey for the amphibian chytrid fungus Batrachochytrium dendrobatidis in Connecticut (USA) finds widespread prevalence.

    PubMed

    Richards-Hrdlicka, Kathryn L; Richardson, Jonathan L; Mohabir, Leon

    2013-02-28

    The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) is an emerging infectious fungal pathogen of amphibians and is linked to global population declines. Until now, there has only been 1 survey for the fungus in the northeastern USA, which focused primarily on northern New England. We tested for Bd in a large number of samples (916 individuals from 116 sites) collected throughout the state of Connecticut, representing 18 native amphibian species. In addition, 239 preserved wood frog Lithobates sylvaticus tadpoles from throughout the state were screened for the fungus. Bd presence was assessed in both the fresh field swabs and the preserved samples using a sensitive quantitative PCR assay. Our contemporary survey found widespread Bd prevalence throughout Connecticut, occurring in 14 species and in 28% of all sampled animals. No preserved L. sylvaticus specimens tested positive for the fungus. Two common species, bullfrogs R. catesbeiana and green frogs R. clamitans had particularly high infection rates (0.21-0.39 and 0.33-0.42, respectively), and given their wide distribution throughout the state, we suggest they may serve as sentinels for Bd occurrence in this region. Further analyses found that several other factors increase the likelihood of infection, including life stage, host sex, and host family. Within sites, ponds with ranids, especially green frogs, increased the likelihood of Bd prevalence. By studying Bd in populations not facing mass declines, the results from this study are an important contribution to our understanding of how some amphibian species and populations remain infected yet exhibit no signs of chytridiomycosis even when Bd is widely distributed. PMID:23446966

  9. Trichobothrial mediation of an aquatic escape response: Directional jumps by the fishing spider, Dolomedes triton, foil frog attacks

    PubMed Central

    Suter, Robert. B.

    2003-01-01

    Fishing spiders (Pisauridae) frequent the surfaces of ponds and streams and thereby expose themselves to predation by a variety of aquatic and semi-aquatic vertebrates. To assess the possibility that the impressive jumps of fishing spiders from the water surface function in evading attacks by frogs, attacks by bullfrogs (Rana catesbiana) and green frogs (R. clamitans) on Dolomedes triton were studied. Both the attack dynamics of the frogs and the evasive behaviors of the spiders were recorded at 250 frames per second. A freeze-dried bullfrog, propelled toward spiders with acceleration, posture, and position that approximated the natural attack posture and dynamics, was used to assess the spiders' behavior. Qualitatively, the spiders responded to these mock-attacks just as they had to attacks by live frogs: jumping (N=29 jumps, 56.9% of instances), rearing the legs nearest the attacking frog (N=15, 29.4%), or showing no visible response (N=7, 13.7%). Spiders that jumped always did so away (in the vertical plane) from the attack (mean =137° vs. vertical at 90° or horizontally toward the frog at 0°). The involvement of the trichobothria (leg hairs sensitive to air movements), and the eyes as sensory mediators of the evasion response was assessed. Spiders with deactivated trichobothria were significantly impaired relative to intact and sham-deactivated spiders, and relative to spiders in total darkness. Thus, functional trichobothria, unlike the eyes, are both necessary and sufficient mediators of the evasion response. Measurements of air flow during frog attacks suggest that an exponential rise in flow velocity is the airborne signature of an attack. Abbreviation: a acceleration (m s−2) fps frames per second HS high-speed video v velocity (m s−1) PMID:15841235

  10. Host Density and Competency Determine the Effects of Host Diversity on Trematode Parasite Infection

    PubMed Central

    Wojdak, Jeremy M.; Edman, Robert M.; Wyderko, Jennie A.; Zemmer, Sally A.; Belden, Lisa K.

    2014-01-01

    Variation in host species composition can dramatically alter parasite transmission in natural communities. Whether diverse host communities dilute or amplify parasite transmission is thought to depend critically on species traits, particularly on how hosts affect each other’s densities, and their relative competency as hosts. Here we studied a community of potential hosts and/or decoys (i.e. non-competent hosts) for two trematode parasite species, Echinostoma trivolvis and Ribeiroia ondatrae, which commonly infect wildlife across North America. We manipulated the density of a focal host (green frog tadpoles, Rana clamitans), in concert with manipulating the diversity of alternative species, to simulate communities where alternative species either (1) replace the focal host species so that the total number of individuals remains constant (substitution) or (2) add to total host density (addition). For E. trivolvis, we found that total parasite transmission remained roughly equal (or perhaps decreased slightly) when alternative species replaced focal host individuals, but parasite transmission was higher when alternative species were added to a community without replacing focal host individuals. Given the alternative species were roughly equal in competency, these results are consistent with current theory. Remarkably, both total tadpole and per-capita tadpole infection intensity by E. trivolvis increased with increasing intraspecific host density. For R. ondatrae, alternative species did not function as effective decoys or hosts for parasite infective stages, and the diversity and density treatments did not produce clear changes in parasite transmission, although high tank to tank variation in R. ondatrae infection could have obscured patterns. PMID:25119568

  11. Host and parasite thermal acclimation responses depend on the stage of infection.

    PubMed

    Altman, Karie A; Paull, Sara H; Johnson, Pieter T J; Golembieski, Michelle N; Stephens, Jeffrey P; LaFonte, Bryan E; Raffel, Thomas R

    2016-07-01

    Global climate change is expected to alter patterns of temperature variability, which could influence species interactions including parasitism. Species interactions can be difficult to predict in variable-temperature environments because of thermal acclimation responses, i.e. physiological changes that allow organisms to adjust to a new temperature following a temperature shift. The goal of this study was to determine how thermal acclimation influences host resistance to infection and to test for parasite acclimation responses, which might differ from host responses in important ways. We tested predictions of three, non-mutually exclusive hypotheses regarding thermal acclimation effects on infection of green frog tadpoles (Lithobates clamitans) by the trematode parasite Ribeiroia ondatrae with fully replicated controlled-temperature experiments. Trematodes or tadpoles were independently acclimated to a range of 'acclimation temperatures' prior to shifting them to new 'performance temperatures' for experimental infections. Trematodes that were acclimated to intermediate temperatures (19-22 °C) had greater encystment success across temperatures than either cold- or warm-acclimated trematodes. However, host acclimation responses varied depending on the stage of infection (encystment vs. clearance): warm- (22-28 °C) and cold-acclimated (13-19 °C) tadpoles had fewer parasites encyst at warm and cold performance temperatures, respectively, whereas intermediate-acclimated tadpoles (19-25 °C) cleared the greatest proportion of parasites in the week following exposure. These results suggest that tadpoles use different immune mechanisms to resist different stages of trematode infection, and that each set of mechanisms has unique responses to temperature variability. Our results highlight the importance of considering thermal responses of both parasites and hosts when predicting disease patterns in variable-temperature environments.

  12. LETTER REPORT. INDEPENDENT CONFIRMATORY SURVEY RESULTS OF SOILS ASSOCIATED WITH THE ARGYLE STREET SEWER LINE AT THE UNITED NUCLEAR CORPORATION NAVAL PRODUCTS SITE, NEW HAVEN, CONNECTICUT

    SciTech Connect

    Adams, Wade C.

    2012-01-24

    Oak Ridge Institute for Science and Education (ORISE) personnel visited the United Nuclear Corporation (UNC) Naval Products site on three separate occasions during the months of October and November 2011. The purpose of these visits was to conduct confirmatory surveys of soils associated with the Argyle Street sewer line that was being removed. Soil samples were collected from six different, judgmentally determined locations in the Argyle Street sewer trench. In addition to the six soil samples collected by ORISE, four replicate soil samples were collected by Cabrera Services, Inc. (CSI) for analysis by the ORISE laboratory. Replicate samples S0010 and S0011 were final status survey (FSS) bias samples; S0012 was an FSS systematic sample; and S0015 was a waste characterization sample. Six soil samples were also collected for background determination. Uranium-235 and uranium-238 concentrations were determined via gamma spectroscopy; the spectra were also reviewed for other identifiable photopeaks. Radionuclide concentrations for these soil samples are provided. In addition to the replicate samples and the samples collected by ORISE, CSI submitted three soil samples for inter-laboratory comparison analyses. One sample was from the background reference area, one was from waste characterization efforts (material inside the sewer line), and one was a FSS sample. The inter-laboratory comparison analyses results between ORISE and CSI were in agreement, except for one sample collected in the reference area. Smear results For Argyle Street sewer pipes are tabulated.

  13. Face-by-face growth of sucrose crystals from aqueous solutions in the presence of raffinose. I. Experiments and kinetic-adsorption model

    NASA Astrophysics Data System (ADS)

    Sgualdino, G.; Aquilano, D.; Cincotti, A.; Pastero, L.; Vaccari, G.

    2006-06-01

    Experimental growth kinetics of {1 0 0}, {1 0 1¯}, {1 1 0} and {1¯ 1¯ 0}, the four most important F (flat) forms of sucrose crystal, has been investigated within a range of low supersaturations ( 0.040⩽σ⩽0.080) and under varying raffinose concentrations (0.0 ⩽Craff⩽8.0% H 2O). The comparison with growth isotherms determined in pure solution confirms that raffinose dramatically slows down the growth rates of the first three forms, which still go on growing by the screw dislocation mechanism. Further, dead zones occur for both the {1 0 1¯} and {1 1 0} forms. On the contrary the {1¯ 1¯ 0} form is weakly affected, at least up to Craff≈3% H 2O, owing to the low structural compatibility between its surface sites and the adsorbed raffinose molecules. Both Cabrera-Vermilyea and Kubota-Mullin models, associated with Langmuir-type equilibrium isotherms, are tested to find the more suitable description of the kinetic behaviour in the presence of raffinose. The Kubota-Mullin model resulting the better one, we concluded that adsorption occurs at kink sites of all the interested forms. The predictive power of α h k l , the effectiveness coefficient of this model, is outlined as well. Finally, the disagreements between the model predictions and the experimental behaviour of the {1 0 0} form are attributed to the peculiar structure of its surface.

  14. Coleopterans associated with plants that form phytotelmata in subtropical and temperate Argentina, South America.

    PubMed

    Campos, Raúl E; Fernández, Liliana A

    2011-01-01

    A list of the most common plants that form phytotelmata and their associated coleopterans (aquatic, semi-aquatic and terrestrial) from the northeastern subtropical and temperate area of Argentina, South America with biological and behavioral observations is presented in this study. Species of Poaceae (n = 3), Bromeliaceae (5), Apiaceae (6), Araceae (2), Urticaceae (1), Marantaceae (1), Arecaceae (1), Dipsacaceae (1) and Cyperaceae (1) were identified as phytotelmata. Aquatic species of Scirtidae (2), Dytiscidae (2), and Hydrophilidae (4), semi-aquatic Chelonariidae (2), and terrestrial species of Carabidae (3), Staphylinidae (5), Histeridae (1), Elateridae (1), Cantharidae (1), Cleridae (1), Tenebrionidae (1), Meloidae (1), Anthicidae (1), Chrysomelidae (3), Curculionidae (7) and Apionidae (1) were identified from six species of Eryngium L. (Apiales: Apiaceae), two species of Guadua Kunth (Poales: Poaceae), Aechmea distichantha Lemaire (Poales: Bromeliaceae), and from fallen leaves of Euterpe edulis Martius (Arecales: Arecaceae) from the temperate and subtropical area. The highest species richness was recorded in Eryngium phytotelmata. Fifteen species of beetles inhabit Eryngium cabrerae Pontiroli, 11 in E. horridum Malme, 7 in E. stenophyllum Urban, 4 in E. aff. serra Chamisso and Schlechtendal., 3 in E. elegans Chamisso and Schlechtendal, 2 in E. eburneum Decne and E. pandanifolium Chamisso and Schlechtendal. From bamboo, 6 species of coleopterans were collected from Guadua trinii (Nees) Nees ex Ruprecht and 4 from G. chacoensis (Rojas) Londoño and Peterson. Three species of aquatic coleopterans were recorded from A. distichantha and only one from E. edulis.

  15. Coleopterans Associated with Plants that form Phytotelmata in Subtropical and Temperate Argentina, South America

    PubMed Central

    Campos, Raúl E.; Fernández, Liliana A.

    2011-01-01

    A list of the most common plants that form phytotelmata and their associated coleopterans (aquatic, semi-aquatic and terrestrial) from the northeastern subtropical and temperate area of Argentina, South America with biological and behavioral observations is presented in this study. Species of Poaceae (n = 3), Bromeliaceae (5), Apiaceae (6), Araceae (2), Urticaceae (1), Marantaceae (1), Arecaceae (1), Dipsacaceae (1) and Cyperaceae (1) were identified as phytotelmata. Aquatic species of Scirtidae (2), Dytiscidae (2), and Hydrophilidae (4), semi-aquatic Chelonariidae (2), and terrestrial species of Carabidae (3), Staphylinidae (5), Histeridae (1), Elateridae (1), Cantharidae (1), Cleridae (1), Tenebrionidae (1), Meloidae (1), Anthicidae (1), Chrysomelidae (3), Curculionidae (7) and Apionidae (1) were identified from six species of Eryngium L. (Apiales: Apiaceae), two species of Guadua Kunth (Poales: Poaceae), Aechmea distichantha Lemaire (Poales: Bromeliaceae), and from fallen leaves of Euterpe edulis Martius (Arecales: Arecaceae) from the temperate and subtropical area. The highest species richness was recorded in Eryngium phytotelmata. Fifteen species of beetles inhabit Eryngium cabrerae Pontiroli, 11 in E. horridum Malme, 7 in E. stenophyllum Urban, 4 in E. aff. serra Chamisso and Schlechtendal., 3 in E. elegans Chamisso and Schlechtendal, 2 in E. eburneum Decne and E. pandanifolium Chamisso and Schlechtendal. From bamboo, 6 species of coleopterans were collected from Guadua trinii (Nees) Nees ex Ruprecht and 4 from G. chacoensis (Rojas) Londoño and Peterson. Three species of aquatic coleopterans were recorded from A. distichantha and only one from E. edulis. PMID:22236084

  16. Steps in Solution Growth: Revised Gibbs-Thomson Law, Turbulence and Morphological Stability

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.; Rashkovich, L. N.; Vekilov, P. G.

    2004-01-01

    Two groups of new phenomena revealed by AFM and high resolution optical interferometry on crystal faces growing from solutions will be discussed. 1. Spacing between strongly polygonized spiral steps with low less than 10(exp -2) kink density on lysozyme and K- biphtalate do not follow the Burton-cabrera-Frank theory. The critical length of the yet immobile first Short step segment adjacent to a pinning defect (dislocation, stacking fault) is many times longer than that following from the step free energy. The low-kink density steps are typical of many growth conditions and materials, including low temperature gas phase epitaxy and MBE. 2. The step bunching pattern on the approx. 1 cm long { 110) KDP face growing from the turbulent solution flow (Re (triple bonds) 10(exp 4), solution flow rate approx. 1 m/s) suggests that the step bunch height does not increase infinitely as the bunch path on the crystal face rises, as is usually observed on large KDP crystals. The mechanism controlling the maximal bunch width and height is based on the drag of the solution depleted by the step bunch down thc solution stream. It includes splitting, coagulation and interlacing of bunches

  17. THE POSSIBLE MOON OF KEPLER-90g IS A FALSE POSITIVE

    SciTech Connect

    Kipping, D. M.; Torres, G.; Buchhave, L. A.; Huang, X.; Bakos, G. Á.; Nesvorný, D.; Schmitt, A. R.

    2015-01-20

    The discovery of an exomoon would provide deep insights into planet formation and the habitability of planetary systems, with transiting examples being particularly sought after. Of the hundreds of Kepler planets now discovered, the seven-planet system Kepler-90 is unusual for exhibiting an unidentified transit-like signal in close proximity to one of the transits of the long-period gas-giant Kepler-90g, as noted by Cabrera et al. As part of the ''Hunt for Exomoons with Kepler'' project, we investigate this possible exomoon signal and find it passes all conventional photometric, dynamical, and centroid diagnostic tests. However, pixel-level light curves indicate that the moon-like signal occurs on nearly all of the target's pixels, which we confirm using a novel way of examining pixel-level data which we dub the ''transit centroid''. This test reveals that the possible exomoon to Kepler-90g is likely a false positive, perhaps due to a cosmic ray induced sudden pixel sensitivity dropout. This work highlights the extreme care required for seeking non-periodic low-amplitude transit signals, such as exomoons.

  18. Interactions of salicylic acid derivatives with calcite crystals.

    PubMed

    Ukrainczyk, Marko; Gredičak, Matija; Jerić, Ivanka; Kralj, Damir

    2012-01-01

    Investigation of basic interactions between the active pharmaceutical compounds and calcium carbonates is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of salicylic acid and its amino acid derivates, chosen as pharmaceutically relevant model compounds, with calcite crystals are described. Therefore, the crystal growth kinetics of well defined rhombohedral calcite seed crystals in the systems containing salicylic acid (SA), 5-amino salicylic acid (5-ASA), N-salicyloil-l-aspartic acid (N-Sal-Asp) or N-salicyloil-l-glutamic acid (N-Sal-Glu), were investigated. The precipitation systems were of relatively low initial supersaturation and of apparently neutral pH. The data on the crystal growth rate reductions in the presence of the applied salicylate molecules were analyzed by means of Cabrera & Vermileya's, and Kubota & Mullin's models of interactions of the dissolved additives and crystal surfaces. The crystal growth kinetic experiments were additionally supported with the appropriate electrokinetic, spectroscopic and adsorption measurements. The Langmuir adsorption constants were determined and they were found to be in a good correlation with values obtained from crystal growth kinetic analyses. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The values of average spacing between the adjacent salicylate adsorption active sites and the average distance between the neighboring adsorbed salicylate molecules were also estimated. PMID:21963207

  19. Vertical and temporal distribution of pelagic decapod crustaceans over the shelf-break and middle slope in two contrasting zones around Mallorca (western Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Simão, Daniela S.; Torres, Asvin P.; Olivar, M. Pilar; Abelló, Pere

    2014-10-01

    The pelagic decapod crustacean fauna of two different zones (Sóller and Cabrera) with different hydrographic dynamics and oligotrophy levels was studied around Mallorca (western Mediterranean), the latter with a higher degree of oligotrophy than the former. Samples were taken with a Pelagic Trawl and an IKMT in the upper 600 m of the water column, targeting larger and middle-sized nektonic species, respectively. Fourteen species were collected: five dendrobranchiate shrimps, eight caridean shrimps and one scyllarid lobster. Some species were restricted to the shelf-break: Chlorotocus crassicornis and Plesionika heterocarpus. Others were exclusive of the middle slope: Pasiphaea multidentata, and Sergia robusta. Pasiphaea sivado and Gennadas elegans occurred in all pelagic strata. Multivariate analyses showed several distinct assemblages related to bathymetry and sampling depth. No significant differences were found concerning zone or sampled seasons. Bathymetrically, Deep Scattering Layers showed the highest diversity. No decapod crustaceans occurred in epipelagic daytime samples. The pelagic decapod community sampled was structured by both the geomorphology (and associated hydrographic characteristics over the shelf-break) and the influence of light in the water column. Size analysis showed species-specific patterns concerning size/age movements into the water column throughout the day-night cycle.

  20. Refined BCF-type boundary conditions for mesoscale surface step dynamics

    SciTech Connect

    Zhao, Renjie; Ackerman, David M.; Evans, James W.

    2015-06-24

    Deposition on a vicinal surface with alternating rough and smooth steps is described by a solid-on-solid model with anisotropic interactions. Kinetic Monte Carlo (KMC) simulations of the model reveal step pairing in the absence of any additional step attachment barriers. We explore the description of this behavior within an analytic Burton-Cabrera-Frank (BCF)-type step dynamics treatment. Without attachment barriers, conventional kinetic coefficients for the rough and smooth steps are identical, as are the predicted step velocities for a vicinal surface with equal terrace widths. However, we determine refined kinetic coefficients from a two-dimensional discrete deposition-diffusion equation formalism which accounts for step structure. These coefficients are generally higher for rough steps than for smooth steps, reflecting a higher propensity for capture of diffusing terrace adatoms due to a higher kink density. Such refined coefficients also depend on the local environment of the step and can even become negative (corresponding to net detachment despite an excess adatom density) for a smooth step in close proximity to a rough step. Incorporation of these refined kinetic coefficients into a BCF-type step dynamics treatment recovers quantitatively the mesoscale step-pairing behavior observed in the KMC simulations.

  1. Refined BCF-type boundary conditions for mesoscale surface step dynamics

    DOE PAGESBeta

    Zhao, Renjie; Ackerman, David M.; Evans, James W.

    2015-06-24

    Deposition on a vicinal surface with alternating rough and smooth steps is described by a solid-on-solid model with anisotropic interactions. Kinetic Monte Carlo (KMC) simulations of the model reveal step pairing in the absence of any additional step attachment barriers. We explore the description of this behavior within an analytic Burton-Cabrera-Frank (BCF)-type step dynamics treatment. Without attachment barriers, conventional kinetic coefficients for the rough and smooth steps are identical, as are the predicted step velocities for a vicinal surface with equal terrace widths. However, we determine refined kinetic coefficients from a two-dimensional discrete deposition-diffusion equation formalism which accounts for stepmore » structure. These coefficients are generally higher for rough steps than for smooth steps, reflecting a higher propensity for capture of diffusing terrace adatoms due to a higher kink density. Such refined coefficients also depend on the local environment of the step and can even become negative (corresponding to net detachment despite an excess adatom density) for a smooth step in close proximity to a rough step. Incorporation of these refined kinetic coefficients into a BCF-type step dynamics treatment recovers quantitatively the mesoscale step-pairing behavior observed in the KMC simulations.« less

  2. Understanding the effects of strain on morphological instabilities of a nanoscale island during heteroepitaxial growth

    SciTech Connect

    Feng, Lu; Wang, Jing; Wang, Shibin; Li, Linan; Shen, Min; Wang, Zhiyong; Chen, Zhenfei; Zhao, Yang

    2015-07-21

    A comprehensive morphological stability analysis of a nanoscale circular island during heteroepitaxial growth is presented based on continuum elasticity theory. The interplay between kinetic and thermodynamic mechanisms is revealed by including strain-related kinetic processes. In the kinetic regime, the Burton-Cabrera-Frank model is adopted to describe the growth front of the island. Together with kinetic boundary conditions, various kinetic processes including deposition flow, adatom diffusion, attachment-detachment kinetics, and the Ehrlich-Schwoebel barrier can be taken into account at the same time. In the thermodynamic regime, line tension, surface energy, and elastic energy are considered. As the strain relief in the early stages of heteroepitaxy is more complicated than commonly suggested by simple consideration of lattice mismatch, we also investigate the effects of external applied strain and elastic response due to perturbations on the island shape evolution. The analytical expressions for elastic fields induced by mismatch strain, external applied strain, and relaxation strain are presented. A systematic approach is developed to solve the system via a perturbation analysis which yields the conditions of film morphological instabilities. Consistent with previous experimental and theoretical work, parametric studies show the kinetic evolution of elastic relaxation, island morphology, and film composition under various conditions. Our present work offers an effective theoretical approach to get a comprehensive understanding of the interplay between different growth mechanisms and how to tailor the growth mode by controlling the nature of the crucial factors.

  3. Analytic formulations for one-dimensional decay of rectangular homoepitaxial islands during coarsening on anisotropic fcc (110) surfaces

    SciTech Connect

    Wang, Chi-Jen; Han, Yong; Walen, Holly; Russell, Selena M.; Thiel, Patricia A.; Evans, James W.

    2013-10-01

    Submonolayer homoepitaxial fcc (110) systems display behavior reflecting strong anisotropy at lower temperatures, including one-dimensional decay during Ostwald ripening of rectangular islands maintaining constant width in the (001) direction. To appropriately describe this behavior, we first develop a refined continuum Burton-Cabrera-Frank formalism, which accounts for a lack of equilibration of island shape and importantly also for inhibited incorporation of adatoms at almost-faceted (1¯10) island edges through effective kinetic coefficients. This formalism is shown to describe accurately the adatom diffusion fluxes between islands and thus island evolution for a complex experimental island configuration, as confirmed by matching results from realistic atomistic simulations for this configuration. This approach also elucidates basic dependencies of flux on island geometry and temperature. Second, a further refinement is presented incorporating separate terrace and edge adatom density fields either in a continuum setting or alternatively in a spatially discrete diffusion equation setting. The second approach allows more flexibility and accuracy in accounting for edge-diffusion kinetics including corner rounding, a lack of equilibration of the edge adatom density at (1¯10) island edges, and the effect of rare kinks on (1¯10) island edges. Finally and significantly, it suggests facile two-way corner rounding at the island periphery during island decay, contrasting the previous picture.

  4. Microcalorimetry of oxygen adsorption on fcc Co{110}.

    PubMed

    Liao, Kristine; Fiorin, Vittorio; Jenkins, Stephen J; King, David A

    2012-05-28

    The coverage dependent heats of adsorption and sticking probabilities for oxygen on fcc Co{110} have been measured at 300 K using single crystal adsorption calorimetry (SCAC). Initial adsorption is consistent with dissociative chemisorption at low coverage followed by oxide formation above 0.6 ML coverage. The initial heat of adsorption of 633 kJ mol(-1) is similar to heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron. As the coverage increases, the heat of adsorption and sticking probability drop very rapidly up to the onset of oxidation. As already observed for other oxygen-metal surface systems, strong lateral adatom repulsions are responsible for the transition from the chemisorption regime to oxide film formation at higher coverage. The heat of oxide formation at the onset is 475 kJ mol(-1), which is consistent with the formation of CoO crystallites. The oxide film formation is discussed in terms of nucleation and island growth, and the Mott-Cabrera mechanisms, the latter being evidenced by the relatively constant heat of adsorption and sticking probability in contrast to the nickel and iron oxidation cases.

  5. Numerical Simulation of Nanostructure Growth

    NASA Technical Reports Server (NTRS)

    Hwang, Helen H.; Bose, Deepak; Govindan, T. R.; Meyyappan, M.

    2004-01-01

    Nanoscale structures, such as nanowires and carbon nanotubes (CNTs), are often grown in gaseous or plasma environments. Successful growth of these structures is defined by achieving a specified crystallinity or chirality, size or diameter, alignment, etc., which in turn depend on gas mixture ratios. pressure, flow rate, substrate temperature, and other operating conditions. To date, there has not been a rigorous growth model that addresses the specific concerns of crystalline nanowire growth, while demonstrating the correct trends of the processing conditions on growth rates. Most crystal growth models are based on the Burton, Cabrera, and Frank (BCF) method, where adatoms are incorporated into a growing crystal at surface steps or spirals. When the supersaturation of the vapor is high, islands nucleate to form steps, and these steps subsequently spread (grow). The overall bulk growth rate is determined by solving for the evolving motion of the steps. Our approach is to use a phase field model to simulate the growth of finite sized nanowire crystals, linking the free energy equation with the diffusion equation of the adatoms. The phase field method solves for an order parameter that defines the evolving steps in a concentration field. This eliminates the need for explicit front tracking/location, or complicated shadowing routines, both of which can be computationally expensive, particularly in higher dimensions. We will present results demonstrating the effect of process conditions, such as substrate temperature, vapor supersaturation, etc. on the evolving morphologies and overall growth rates of the nanostructures.

  6. Coleopterans associated with plants that form phytotelmata in subtropical and temperate Argentina, South America.

    PubMed

    Campos, Raúl E; Fernández, Liliana A

    2011-01-01

    A list of the most common plants that form phytotelmata and their associated coleopterans (aquatic, semi-aquatic and terrestrial) from the northeastern subtropical and temperate area of Argentina, South America with biological and behavioral observations is presented in this study. Species of Poaceae (n = 3), Bromeliaceae (5), Apiaceae (6), Araceae (2), Urticaceae (1), Marantaceae (1), Arecaceae (1), Dipsacaceae (1) and Cyperaceae (1) were identified as phytotelmata. Aquatic species of Scirtidae (2), Dytiscidae (2), and Hydrophilidae (4), semi-aquatic Chelonariidae (2), and terrestrial species of Carabidae (3), Staphylinidae (5), Histeridae (1), Elateridae (1), Cantharidae (1), Cleridae (1), Tenebrionidae (1), Meloidae (1), Anthicidae (1), Chrysomelidae (3), Curculionidae (7) and Apionidae (1) were identified from six species of Eryngium L. (Apiales: Apiaceae), two species of Guadua Kunth (Poales: Poaceae), Aechmea distichantha Lemaire (Poales: Bromeliaceae), and from fallen leaves of Euterpe edulis Martius (Arecales: Arecaceae) from the temperate and subtropical area. The highest species richness was recorded in Eryngium phytotelmata. Fifteen species of beetles inhabit Eryngium cabrerae Pontiroli, 11 in E. horridum Malme, 7 in E. stenophyllum Urban, 4 in E. aff. serra Chamisso and Schlechtendal., 3 in E. elegans Chamisso and Schlechtendal, 2 in E. eburneum Decne and E. pandanifolium Chamisso and Schlechtendal. From bamboo, 6 species of coleopterans were collected from Guadua trinii (Nees) Nees ex Ruprecht and 4 from G. chacoensis (Rojas) Londoño and Peterson. Three species of aquatic coleopterans were recorded from A. distichantha and only one from E. edulis. PMID:22236084

  7. The Physical Tourist

    NASA Astrophysics Data System (ADS)

    Sánchez-Ron, José M.

    2006-09-01

    I provide a tour of Madrid, focusing especially on physical institutions that were created during the 19th and 20th centuries.These include the Astronomical Observatory close to the Prado Museum, which itself was conceived as a home for the Royal Academy of Sciences but became instead a world-famous art museum in 1819, leaving the Royal Academy of Sciences without a permanent home until 1866.The Laboratory of Physical Researches was created in 1910, and under the direction of Blas Cabrera (1878 1945), who also held a professorship at the Universidad Central, it fostered most of the Spanish research in physics at the time, in particular the famous spectroscopic researches of Miguel A. Catalán (1894 1957). Nearby were the so-called Transatlantico building and the Students’ Residence where Albert Einstein (1879 1955), for example, lectured in 1923, and which together continue to serve as a major cultural center in Madrid. Later, the physical laboratory was replaced by the National Institute of Physics and Chemistry, which was constructed with funds from the Rockefeller Foundation and inaugurated in 1932. A new University City with its Faculty of Sciences also was constructed on the northwestern outskirts of Madrid, but almost all of its buildings were totally destroyed during the devastating Spanish Civil War of 1936 1939. It was reconstructed after the war and became home, for example, to Spain’s first nuclear reactor, which achieved criticality in 1958.

  8. Interactions of salicylic acid derivatives with calcite crystals.

    PubMed

    Ukrainczyk, Marko; Gredičak, Matija; Jerić, Ivanka; Kralj, Damir

    2012-01-01

    Investigation of basic interactions between the active pharmaceutical compounds and calcium carbonates is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of salicylic acid and its amino acid derivates, chosen as pharmaceutically relevant model compounds, with calcite crystals are described. Therefore, the crystal growth kinetics of well defined rhombohedral calcite seed crystals in the systems containing salicylic acid (SA), 5-amino salicylic acid (5-ASA), N-salicyloil-l-aspartic acid (N-Sal-Asp) or N-salicyloil-l-glutamic acid (N-Sal-Glu), were investigated. The precipitation systems were of relatively low initial supersaturation and of apparently neutral pH. The data on the crystal growth rate reductions in the presence of the applied salicylate molecules were analyzed by means of Cabrera & Vermileya's, and Kubota & Mullin's models of interactions of the dissolved additives and crystal surfaces. The crystal growth kinetic experiments were additionally supported with the appropriate electrokinetic, spectroscopic and adsorption measurements. The Langmuir adsorption constants were determined and they were found to be in a good correlation with values obtained from crystal growth kinetic analyses. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The values of average spacing between the adjacent salicylate adsorption active sites and the average distance between the neighboring adsorbed salicylate molecules were also estimated.

  9. Surface kinetics in AlN growth: A universal model for the control of surface morphology in III-nitrides

    NASA Astrophysics Data System (ADS)

    Bryan, Isaac; Bryan, Zachary; Mita, Seiji; Rice, Anthony; Tweedie, James; Collazo, Ramón; Sitar, Zlatko

    2016-03-01

    AlN epitaxial thin films were grown on both vicinal (0001)-oriented native single crystal AlN substrates and AlN templates grown on vicinal (0001)-oriented sapphire to develop a surface kinetic framework for the control of surface morphology. A Burton, Cabrera, and Frank (BCF) theory-based model is formulated and utilized to understand the dependence of the surface kinetics on the vapor supersaturation, σ, and substrate misorientation angle, α. The surface energy of the Al-polar surface of AlN was experimentally determined using BCF theory to be 149±8 meV/Å2. The critical misorientation angle for the onset of step-bunching was determined to be ~0.25° for a growth rate of 500 nm/h and temperature of 1250 °C. Transitioning from a surface with 2D nuclei to one with bilayer steps required a decrease in σ or an increase in α, whereas the suppression of step-bunching required an increase in σ or a decrease in α.

  10. From atoms to steps: The microscopic origins of crystal evolution

    NASA Astrophysics Data System (ADS)

    Patrone, Paul N.; Einstein, T. L.; Margetis, Dionisios

    2014-07-01

    The Burton-Cabrera-Frank (BCF) theory of crystal growth has been successful in describing a wide range of phenomena in surface physics. Typical crystal surfaces are slightly misoriented with respect to a facet plane; thus, the BCF theory views such systems as composed of staircase-like structures of steps separating terraces. Adsorbed atoms (adatoms), which are represented by a continuous density, diffuse on terraces, and steps move by absorbing or emitting these adatoms. Here we shed light on the microscopic origins of the BCF theory by deriving a simple, one-dimensional (1D) version of the theory from an atomistic, kinetic restricted solid-on-solid (KRSOS) model without external material deposition. We define the time-dependent adatom density and step position as appropriate ensemble averages in the KRSOS model, thereby exposing the non-equilibrium statistical mechanics origins of the BCF theory. Our analysis reveals that the BCF theory is valid in a low adatom-density regime, much in the same way that an ideal gas approximation applies to dilute gasses. We find conditions under which the surface remains in a low-density regime and discuss the microscopic origin of corrections to the BCF model.

  11. One-dimensional model of interacting-step fluctuations on vicinal surfaces: Analytical formulas and kinetic Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Patrone, Paul N.; Einstein, T. L.; Margetis, Dionisios

    2010-12-01

    We study analytically and numerically a one-dimensional model of interacting line defects (steps) fluctuating on a vicinal crystal. Our goal is to formulate and validate analytical techniques for approximately solving systems of coupled nonlinear stochastic differential equations (SDEs) governing fluctuations in surface motion. In our analytical approach, the starting point is the Burton-Cabrera-Frank (BCF) model by which step motion is driven by diffusion of adsorbed atoms on terraces and atom attachment-detachment at steps. The step energy accounts for entropic and nearest-neighbor elastic-dipole interactions. By including Gaussian white noise to the equations of motion for terrace widths, we formulate large systems of SDEs under different choices of diffusion coefficients for the noise. We simplify this description via (i) perturbation theory and linearization of the step interactions and, alternatively, (ii) a mean-field (MF) approximation whereby widths of adjacent terraces are replaced by a self-consistent field but nonlinearities in step interactions are retained. We derive simplified formulas for the time-dependent terrace-width distribution (TWD) and its steady-state limit. Our MF analytical predictions for the TWD compare favorably with kinetic Monte Carlo simulations under the addition of a suitably conservative white noise in the BCF equations.

  12. One-dimensional model of interacting-step fluctuations on vicinal surfaces: Analytical formulas and kinetic Monte-Carlo simulations

    NASA Astrophysics Data System (ADS)

    Patrone, Paul; Einstein, T. L.; Margetis, Dionisios

    2011-03-01

    We study a 1+1D, stochastic, Burton-Cabrera-Frank (BCF) model of interacting steps fluctuating on a vicinal crystal. The step energy accounts for entropic and nearest-neighbor elastic-dipole interactions. Our goal is to formulate and validate a self-consistent mean-field (MF) formalism to approximately solve the system of coupled, nonlinear stochastic differential equations (SDEs) governing fluctuations in surface motion. We derive formulas for the time-dependent terrace width distribution (TWD) and its steady-state limit. By comparison with kinetic Monte-Carlo simulations, we show that our MF formalism improves upon models in which step interactions are linearized. We also indicate how fitting parameters of our steady state MF TWD may be used to determine the mass transport regime and step interaction energy of certain experimental systems. PP and TLE supported by NSF MRSEC under Grant DMR 05-20471 at U. of Maryland; DM supported by NSF under Grant DMS 08-47587.

  13. Distinguishing the effects of convective and diffusive O₂ delivery on VO₂ on-kinetics in skeletal muscle contracting at moderate intensity.

    PubMed

    Spires, Jessica; Gladden, L Bruce; Grassi, Bruno; Goodwin, Matthew L; Saidel, Gerald M; Lai, Nicola

    2013-09-01

    With current techniques, experimental measurements alone cannot characterize the effects of oxygen blood-tissue diffusion on muscle oxygen uptake (Vo₂) kinetics in contracting skeletal muscle. To complement experimental studies, a computational model is used to quantitatively distinguish the contributions of convective oxygen delivery, diffusion into cells, and oxygen utilization to Vo₂ kinetics. The model is validated using previously published experimental Vo₂ kinetics in response to slowed blood flow (Q) on-kinetics in canine muscle (τQ = 20 s, 46 s, and 64 s) [Goodwin ML, Hernández A, Lai N, Cabrera ME, Gladden LB. J Appl Physiol. 112:9-19, 2012]. Distinctive effects of permeability-surface area or diffusive conductance (PS) and Q on Vo₂ kinetics are investigated. Model simulations quantify the relationship between PS and Q, as well as the effects of diffusion associated with PS and Q dynamics on the mean response time of Vo₂. The model indicates that PS and Q are linearly related and that PS increases more with Q when convective delivery is limited by slower Q dynamics. Simulations predict that neither oxygen convective nor diffusive delivery are limiting Vo₂ kinetics in the isolated canine gastrocnemius preparation under normal spontaneous conditions during transitions from rest to moderate (submaximal) energy demand, although both operate close to the tipping point.

  14. Molecular survey of Apicomplexa in Podarcis wall lizards detects Hepatozoon, Sarcocystis, and Eimeria species.

    PubMed

    Harris, D James; Maia, João P M C; Perera, Ana

    2012-06-01

    The occurrence of apicomplexan parasites in Podarcis sp. wall lizards from the Iberian Peninsula and Balearic islands was studied by amplification and sequencing of the 18S rRNA gene. Species from 3 genera, Hepatozoon , Sarcocystis , and Eimeria , were found. The phylogenetic analysis of the 18S rRNA gene provides unexpected insights into the evolutionary history of these parasites. All Hepatozoon spp. specimens were recovered as part of a clade already identified in lizards from North Africa. The Sarcocystis species, detected in Podarcis lilfordi from Cabrera Island in the Balearic Islands, appears related to Sarcocystis gallotiae , known only from endemic Gallotia sp. lizards from the Canary Islands. Based on the lack of snake predators on this island, this parasite presumably presents an atypical transmission cycle that uses the same host species as both intermediate and final host through cannibalism, like S. gallotiae . Eimeria sp. is reported for the first time from Podarcis spp. lizards. This study shows the power of detecting multiple different apicomplexan parasites through screening of tail tissue samples and blood drops that are often collected in reptiles for other purposes. PMID:22746392

  15. Oxidation Behavior of In-Flight Molten Aluminum Droplets in the Twin-Wire Electric Arc Thermal Spray Process

    SciTech Connect

    Donna Post Guillen; Brian G. Williams

    2005-05-01

    This paper examines the in-flight oxidation of molten aluminum sprayed in air using the twin-wire electric arc (TWEA) thermal spray process. The oxidation reaction of aluminum in air is highly exothermic and is represented by a heat generation term in the energy balance. Aerodynamic shear at the droplet surface enhances the amount of in-flight oxidation by: (1) promoting entrainment and mixing of the surface oxides within the droplet, and (2) causing a continuous heat generation effect that increases droplet temperature over that of a droplet without internal circulation. This continual source of heat input keeps the droplets in a liquid state during flight. A linear rate law based on the Mott-Cabrera theory was used to estimate the growth of the surface oxide layer formed during droplet flight. The calculated oxide volume fraction of an average droplet at impact agrees well with the experimentally determined oxide content for a typical TWEA-sprayed aluminum coating, which ranges from 3.3 to 12.7%. An explanation is provided for the elevated, nearly constant surface temperature (~ 2000 oC) of the droplets during flight to the substrate and shows that the majority of oxide content in the coating is produced during flight, rather than after deposition.

  16. Spiral waves in nematic liquid crystals:mExperimental analysis of selection rules

    NASA Astrophysics Data System (ADS)

    Vierheilig, A.; Chevallard, C.; Gilli, J. M.

    1997-06-01

    Archimedian spiral waves develop around umbilics, in an homeotropically anchored nematic sample. They are observed under the influence of a rotating magnetic field in the plane of the glass plates, and in presence of a destabilizing electric field. The geometrical characteristics of these experimental spirals (pitch, rotation frequency, etc.) are analyzed in parameter space. These spiral waves are numerically fitted with Archimedian spirals to good degree of accuracy. The transverse speed of zero curvature Bloch walls are deduced from these measurements. The existing domain of these spiral waves is limited, respectively, toward large (low) magnetic-field rotation speed, or low (large) magnetic-field intensities, by the asynchronous regime (by a Bloch-Ising transition of the walls). These experimental results are compared to two-dimensional interactive simulations of a Ginzburg-Landau equation. The measurements made in the low-field domain (which is a validity condition for the model derivation) confirm the applicability of the same selection criterion deduced by Burton, Cabrera, and Frank [Philos. Trans. R. Soc. London Ser. A 243, 299 (1951)] for the description of spiral shaped steps in cristalline growth, and more recently for the fronts of excitable media.

  17. Composition and anti-insect activity of essential oils from Tagetes L. species (Asteraceae, Helenieae) on Ceratitis capitata Wiedemann and Triatoma infestans Klug.

    PubMed

    López, Sandra B; López, María L; Aragón, Liliana M; Tereschuk, María L; Slanis, Alberto C; Feresin, Gabriela E; Zygadlo, Julio A; Tapia, Alejandro A

    2011-05-25

    Essential oils from four species of the genus Tagetes L. (Asteraceae, Helenieae) collected in Tucumán province, Argentina, were evaluated for their chemical composition, toxicity, and olfactory activity on Mediterranean fruit fly Ceratitis capitata Wiedemann adults and for repellent properties on Triatoma infestans (Klug) (Chagas disease vector). Yields of essential oils range from 0.2 to 0.8% (v/w). The same main constituents among Tagetes minuta L., Tagestes rupestris Cabrera, and Tagetes terniflora Kunth, (cis-trans)-ocimenes, (cis-trans)-tagetones, and (cis-trans)-ocimenones showed important differences in their relative compositions. Tagetes filifolia Lag. was characterized by the recognized phenylpropanoids methylchavicol and trans-anethole as the main components. LD(50) was ≤20 μg/insect in topical bioassays. T. rupestris was the most toxic to C. capitata females, whereas the other oils presented similar toxicities against males and females. Tagetes rupestris oil attracted both sexes of C. capitata at 5 μg, whereas T. minuta showed opposite activities between males (attractant) and females (repellent). Oils from T. minuta and T. filifolia were the most repellent to T. infestans. The results suggest that compositions of essential oils influence their insecticidal and olfactory properties. The essential oils from Tagetes species show an important potential as infochemical agents on insects' behaviors. This study highlights the chemical variability of essential oils as a source of variation of anti-insect properties. PMID:21469658

  18. Mean field approach to fluctuations of surface line defects

    NASA Astrophysics Data System (ADS)

    Margetis, Dionisios

    2011-03-01

    Below the roughening transition temperature, the dynamics of crystal surfaces are driven by the motion of line defects (steps) of atomic size. According to the celebrated Burton Cabrera-Frank (BCF) model, the steps move by mass conservation, as adsorbed atoms (adatoms) diffuse on terraces and attach/detach at step edges. The resulting deterministic equations of motion incorporate nonlinear couplings due to entropic and elastic-dipole step-step interactions. In this talk, I will discuss a formal theory for stochastic aspects of step motion by adding noise to the BCF model in 1+1 dimensions. I will define systematically a ``mean field'' that enables the conversion of the coupled, nonlinear stochastic equations for the distance between neighboring steps (terrace widths) to a single Langevin-type equation for an effective terrace width. In the course of my study, I invoke the Bogoliubov-Born-Green Kirkwood-Yvon (BBGKY) hierarchy for joint terrace-width probability densities and a decorrelation ansatz for terrace widths. By using an example drawn from epitaxial growth (with material deposition from above), I will compare the mean field approach to an exact result from a linearized growth model. [D. Margetis, J. Phys A: Math. Theor. 43, 065003 (2010).] This work was supported by NSF under Grant DMS-0847587.

  19. The Possible Moon of Kepler-90g is a False Positive

    NASA Astrophysics Data System (ADS)

    Kipping, D. M.; Huang, X.; Nesvorný, D.; Torres, G.; Buchhave, L. A.; Bakos, G. Á.; Schmitt, A. R.

    2015-01-01

    The discovery of an exomoon would provide deep insights into planet formation and the habitability of planetary systems, with transiting examples being particularly sought after. Of the hundreds of Kepler planets now discovered, the seven-planet system Kepler-90 is unusual for exhibiting an unidentified transit-like signal in close proximity to one of the transits of the long-period gas-giant Kepler-90g, as noted by Cabrera et al. As part of the "Hunt for Exomoons with Kepler" project, we investigate this possible exomoon signal and find it passes all conventional photometric, dynamical, and centroid diagnostic tests. However, pixel-level light curves indicate that the moon-like signal occurs on nearly all of the target's pixels, which we confirm using a novel way of examining pixel-level data which we dub the "transit centroid." This test reveals that the possible exomoon to Kepler-90g is likely a false positive, perhaps due to a cosmic ray induced sudden pixel sensitivity dropout. This work highlights the extreme care required for seeking non-periodic low-amplitude transit signals, such as exomoons.

  20. Homogenization of composite vicinal surfaces: Evolution laws in 1+1 dimensions

    NASA Astrophysics Data System (ADS)

    Margetis, Dionisios; Nakamura, Kanna

    2012-07-01

    We apply classical homogenization to derive macroscopic relaxation laws for crystal surfaces with distinct inhomogeneities at the microscale. The proposed method relies on a formal multiscale expansion in one spatial coordinate. This approach transcends the coarse graining applied previously via Taylor expansions. Our work offers an extension of the static homogenization formulated in a brief report [D. Margetis, Homogenization of reconstructed crystal surfaces: Fick’s law of diffusion, Phys. Rev. E 79 (2009) 052601] to account for surface evolution. The starting point is the Burton-Cabrera-Frank (BCF) model for the motion of line defects (steps) separating nanoscale terraces. We enrich this model with sequences of distinct material parameters, i.e., disparate diffusivities of adsorbed atoms (adatoms) across terraces, kinetic sticking rates at step edges, and step energy parameters for elastic-dipole interactions. Multiscale expansions for the adatom concentration and flux are used, with a slow diffusive time scale consistent with the quasi-steady regime for terrace diffusion. The ensuing macroscopic, nonlinear evolution laws incorporate averages of the microscale parameters.

  1. From crystal steps to continuum laws: Behavior near large facets in one dimension

    NASA Astrophysics Data System (ADS)

    Margetis, Dionisios; Nakamura, Kanna

    2011-06-01

    The passage from discrete schemes for surface line defects (steps) to nonlinear macroscopic laws for crystals is studied via formal asymptotics in one space dimension. Our goal is to illustrate by explicit computations the emergence from step motion laws of continuum-scale power series expansions for the slope near the edges of large, flat surface regions (facets). We consider surface diffusion kinetics via the Burton, Cabrera and Frank (BCF) model by which adsorbed atoms diffuse on terraces and attach-detach at steps. Nearest-neighbor step interactions are included. The setting is a monotone train of N steps separating two semi-infinite facets at fixed heights. We show how boundary conditions for the continuum slope and flux, and expansions in the height variable near facets, may emerge from the algebraic structure of discrete schemes as N→∞. Our technique relies on the use of self-similar discrete slopes, conversion of discrete schemes to sum equations, and their reduction to nonlinear integral equations for the continuum-scale slope. Approximate solutions to the continuum equations near facet edges are constructed formally by direct iterations. For elastic-dipole and multipole step interactions, the continuum slope is found in agreement with a previous hypothesis of ‘local equilibrium’.

  2. Phase-field modeling of epitaxial growth: Applications to step trains and island dynamics

    NASA Astrophysics Data System (ADS)

    Hu, Zhengzheng; Lowengrub, John S.; Wise, Steven M.; Voigt, Axel

    2012-01-01

    In this paper, we present a new phase-field model including combined effects of edge diffusion, the Ehrlich-Schwoebel barrier, deposition and desorption to simulate epitaxial growth. A new free energy function together with a correction to the initial phase variable profile is used to efficiently capture the morphological evolution when a large deposition flux is imposed. A formal matched asymptotic analysis is performed to show the reduction of the phase-field model to the classical sharp interface Burton-Cabrera-Frank model for step flow when the interfacial thickness vanishes. The phase-field model is solved by a semi-implicit finite difference scheme, and adaptive block-structured Cartesian meshes are used to dramatically increase the efficiency of the solver. The numerical scheme is used to investigate the evolution of perturbed circularly shaped small islands. The effect of edge diffusion is investigated together with the Ehrlich-Schwoebel barrier. We also investigate the linear and nonlinear regimes of a step meandering instability. We reproduce the predicted scaling law for the growth of the meander amplitude, which was based on an analysis of a long wavelength regime. New nonlinear behavior is observed when the meander wavelength is comparable to the terrace width. In particular, a previously unobserved regime of coarsening dynamics is found to occur when the meander wavelength is comparable to the terrace width.

  3. Nucleus and spiral growth mechanisms of nitride semiconductors in metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Akasaka, Tetsuya; Yamamoto, Hideki

    2014-10-01

    Nucleus and spiral growth mechanisms of GaN and InN are investigated using the selective-area metalorganic vapor phase epitaxy (SA-MOVPE) technique on GaN bulk substrates. Nucleus growth of GaN occurs within selective areas having no screw-type dislocations, while spiral growth occurs within selective areas having screw-type dislocations. These growth modes are simultaneously observed on a single substrate in a single growth run. The nucleus and spiral growths of GaN result in the formation of step-free surfaces and growth spirals, respectively, wherein the interstep distance of growth spirals enables us to estimate the degree of surface supersaturation (σ). The σ dependences of nucleus and spiral growth rates of GaN are experimentally investigated. We found that these dependences are well explained by the classical crystal growth theories advocated by Burton, Cabrera, and Frank. We also investigate nucleation of InN using step-free GaN surfaces as an ideal platform.

  4. Step bunching process induced by the flow of steps at the sublimated crystal surface

    NASA Astrophysics Data System (ADS)

    Załuska-Kotur, Magdalena A.; KrzyŻewski, Filip

    2012-06-01

    Stepped GaN(0001) surface is studied by the kinetic Monte Carlo method and compared with the model based on Burton-Cabrera-Frank equations. Successive stages of surface pattern evolution during high temperature sublimation process are discussed. At low sublimation rates, clear, well defined step bunches form. The process happens in the absence or for very low Schwoebel barriers. Bunches of several steps are well separated, move slowly and stay straight. Character of the process changes for more rapid sublimation process where double step formations become dominant and together with meanders and local bunches assemble into the less ordered surface pattern. Solution of the analytic equations written for one dimensional system confirms that step bunching is induced by the particle advection caused by step movement. Relative particle flow towards moving steps becomes important when due to the low Schwoebel barrier both sides of the step are symmetric. Simulations show that in the opposite limit of very high Schwoebel barrier steps fracture and rough surface builds up.

  5. Synthesis and oxidation of luminescent silicon nanocrystals from silicon tetrachloride by very high frequency nonthermal plasma

    NASA Astrophysics Data System (ADS)

    Gresback, Ryan; Nozaki, Tomohiro; Okazaki, Ken

    2011-07-01

    Silicon nanocrystals have recently attracted significant attention for applications in electronics, optoelectronics, and biological imaging due to their size-dependent optical and electronic properties. Here a method for synthesizing luminescent silicon nanocrystals from silicon tetrachloride with a nonthermal plasma is described. Silicon nanocrystals with mean diameters of 3-15 nm are synthesized and have a narrow size distribution with the standard deviation being less than 20% of the mean size. Control over crystallinity is achieved for plasma pressures of 1-12 Torr and hydrogen gas concentrations of 5-70% through adjustment of the plasma power. The size of nanocrystals, and resulting optical properties, is mainly dependent on the gas residence time in the plasma region. Additionally the surface of the nanocrystals is covered by both hydrogen and chlorine. Oxidation of the nanocrystals, which is found to follow the Cabrera-Mott mechanism under ambient conditions, is significantly faster than hydrogen terminated silicon due to partial termination of the nanocrystal surface by chlorine.

  6. Understanding the effects of strain on morphological instabilities of a nanoscale island during heteroepitaxial growth

    NASA Astrophysics Data System (ADS)

    Feng, Lu; Wang, Jing; Wang, Shibin; Li, Linan; Shen, Min; Wang, Zhiyong; Chen, Zhenfei; Zhao, Yang

    2015-07-01

    A comprehensive morphological stability analysis of a nanoscale circular island during heteroepitaxial growth is presented based on continuum elasticity theory. The interplay between kinetic and thermodynamic mechanisms is revealed by including strain-related kinetic processes. In the kinetic regime, the Burton-Cabrera-Frank model is adopted to describe the growth front of the island. Together with kinetic boundary conditions, various kinetic processes including deposition flow, adatom diffusion, attachment-detachment kinetics, and the Ehrlich-Schwoebel barrier can be taken into account at the same time. In the thermodynamic regime, line tension, surface energy, and elastic energy are considered. As the strain relief in the early stages of heteroepitaxy is more complicated than commonly suggested by simple consideration of lattice mismatch, we also investigate the effects of external applied strain and elastic response due to perturbations on the island shape evolution. The analytical expressions for elastic fields induced by mismatch strain, external applied strain, and relaxation strain are presented. A systematic approach is developed to solve the system via a perturbation analysis which yields the conditions of film morphological instabilities. Consistent with previous experimental and theoretical work, parametric studies show the kinetic evolution of elastic relaxation, island morphology, and film composition under various conditions. Our present work offers an effective theoretical approach to get a comprehensive understanding of the interplay between different growth mechanisms and how to tailor the growth mode by controlling the nature of the crucial factors.

  7. Oxidation of freestanding silicon nanocrystals probed with electron spin resonance of interfacial dangling bonds

    NASA Astrophysics Data System (ADS)

    Pereira, R. N.; Rowe, D. J.; Anthony, R. J.; Kortshagen, U.

    2011-04-01

    The oxidation of freestanding silicon nanocrystals (Si-NCs) passivated with Si-H bonds has been investigated for a wide range of oxidation times (from a few minutes to several months) by means of electron spin resonance (ESR) of dangling bonds (DBs) naturally incorporated at the interface between the NC core and the developing oxide shell. These measurements are complemented with surface chemistry analysis from Fourier transform infrared spectroscopy. Two surface phenomena with initiation time thresholds of 15 min and 30 h are inferred from the dependence of ESR spectra on oxidation time. The first initiates before oxidation of surface Si-Si bonds and destruction of the NC hydrogen termination takes place (induction period) and results in a decrease of the DB density and a localization of the DB orbital at the central Si atom. Within the Cabrera-Mott oxidation mechanism, we associate this process with the formation of intermediate interfacial configurations, resulting from surface adsorption of water and oxygen molecules. The second surface phenomenon leads to a steep increase of the defect density and correlates with the formation of surface Si-O-Si bridges, lending experimental support to theoretically proposed mechanisms for interfacial defect formation involving the emission of Si interstitials at the interface between crystalline Si and the growing oxide.

  8. Effect of the crystalline constitution of TiO2 substrates on the growth of ultrathin Mo layer

    NASA Astrophysics Data System (ADS)

    Noirfalise, X.; Renaux, F.; Cossement, D.; Sebaihi, Noham; Lazzaroni, Roberto; Snyders, R.

    2012-11-01

    Metallic molybdenum was deposited by magnetron sputtering on amorphous and (110) rutile TiO2 substrates. An interfacial reaction between the deposited Mo and the TiO2 substrates generating Ti3 +, Ti2 + oxidation states is evidenced by X-ray photoelectron spectroscopy. Our XPS data suggest, as compared to the (110) rutile substrate, a higher reactivity of the amorphous TiO2 leading to a stronger Mo oxidation. In both cases, this reaction, leads to the formation of MoOx nanostructures at the interfaces. The growth mechanism of the Mo deposit as a function of the crystalline constitution of the TiO2 substrate was analyzed by processing the XPS data using the Quases ® software. The data reveal a layer-by-layer growth of the Mo deposit on the (110) rutile substrate and a Stranski-Krastanov growth on the amorphous one. We explain these different growth modes based on the TiO2 surface reactivity and electronic structure using the Cabrera-Mott theory. This explanation is supported by Time-of-Flight Secondary Ion Mass spectrometry profiling.

  9. Multiplicative-cascade dynamics in pole balancing

    NASA Astrophysics Data System (ADS)

    Harrison, Henry S.; Kelty-Stephen, Damian G.; Vaz, Daniela V.; Michaels, Claire F.

    2014-06-01

    Pole balancing is a key task for probing the prospective control that organisms must engage in for purposeful action. The temporal structure of pole-balancing behaviors will reflect the on-line operation of control mechanisms needed to maintain an upright posture. In this study, signatures of multifractality are sought and found in time series of the vertical angle of a pole balanced on the fingertip. Comparisons to surrogate time series reveal multiplicative-cascade dynamics and interactivity across scales. In addition, simulations of a pole-balancing model generating on-off intermittency [J. L. Cabrera and J. G. Milton, Phys. Rev. Lett. 89, 158702 (2002), 10.1103/PhysRevLett.89.158702] were analyzed. Evidence of multifractality is also evident in simulations, though comparing simulated and participant series reveals a significantly greater contribution of cross-scale interactivity for the latter. These findings suggest that multiplicative-cascade dynamics are an extension of on-off intermittency and play a role in prospective coordination.

  10. Numerical Simulation of Ejected Molten Metal Nanoparticles Liquified by Laser Irradiation: Interplay of Geometry and Dewetting

    NASA Astrophysics Data System (ADS)

    Afkhami, S.; Kondic, L.

    2013-07-01

    Metallic nanoparticles, liquified by fast laser irradiation, go through a rapid change of shape attempting to minimize their surface energy. The resulting nanodrops may be ejected from the substrate when the mechanisms leading to dewetting are sufficiently strong, as in the experiments involving gold nanoparticles [Habenicht et al., Science 309, 2043 (2005)]. We use a direct continuum-level approach to accurately model the process of liquid nanodrop formation and the subsequent ejection from the substrate. Our computations show a significant role of inertial effects and an elaborate interplay of initial geometry and wetting properties: e.g., we can control the direction of ejection by prescribing appropriate initial shape and/or wetting properties. The basic insight regarding ejection itself can be reached by considering a simple effective model based on an energy balance. We validate our computations by comparing directly with the experiments specified above involving the length scales measured in hundreds of nanometers and with molecular dynamics simulations on much shorter scales measured in tens of atomic diameters, as by M. Fuentes-Cabrera et al. [Phys. Rev. E 83, 041603 (2011)]. The quantitative agreement, in addition to illustrating how to control particle ejection, shows utility of continuum-based simulation in describing dynamics on nanoscale quantitatively, even in a complex setting as considered here.

  11. Compressional tectonic inversion of the Algero-Balearic basin: Latemost Miocene to present oblique convergence at the Palomares margin (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Giaconia, Flavio; Booth-Rea, Guillermo; Ranero, César R.; Gràcia, Eulàlia; Bartolome, Rafael; Calahorrano, Alcinoe; Lo Iacono, Claudio; Vendrell, Montserrat G.; Cameselle, Alejandra L.; Costa, Sergio; Gómez de la Peña, Laura; Martínez-Loriente, Sara; Perea, Hector; Viñas, Marina

    2015-07-01

    Interpretation of new multichannel seismic reflection profiles indicates that the Palomares margin was formed by crustal-scale extension and coeval magmatic accretion during middle to late Miocene opening of the Algero-Balearic basin. The margin formed at the transition between thinned continental crust intruded by arc volcanism and back-arc oceanic crust. Deformation produced during the later positive inversion of the margin offshore and onshore is partitioned between ~N50°E striking reverse faults and associated folds like the Sierra Cabrera and Abubacer anticlines and N10-20°E sinistral strike-slip faults like Palomares and Terreros faults. Parametric subbottom profiles and multibeam bathymetry offshore, structural analysis, available GPS geodetic displacement data, and earthquake focal mechanisms jointly indicate that tectonic inversion of the Palomares margin is currently active. The Palomares margin shows a structural pattern comparable to the north Maghrebian margins where Africa-Eurasia plate convergence is accommodated by NE-SW reverse faults, NNW-SSE sinistral faults, and WNW-ESE dextral ones. Contractive structures at this margin contribute to the general inversion of the Western Mediterranean since ~7 Ma, coeval to inversion at the Algerian margin. Shortening at the Alboran ridge and Al-Idrisi faults occurred later, since 5 Ma, indicating a westward propagation of the compressional inversion of the Western Mediterranean.

  12. Influence of some foreign metal ions on crystal growth kinetics of brushite (CaHPO 4·2H 2O)

    NASA Astrophysics Data System (ADS)

    Rosa, Silvia; Lundager Madsen, Hans E.

    2010-10-01

    Brushite, CaHPO 4·2H 2O, has been precipitated at 25 °C in the presence of Mg 2+, Ba 2+ or Cu 2+ at concentrations up to 0.5 mM. When initial pH is sufficiently low to exclude nanocrystalline apatite as the initial solid phase, overall crystal growth rate may be determined from simple mass crystallization by recording pH as function of time. A combination of surface nucleation (birth-and-spread) and spiral (BCF) growth was found. Edge free energy was determined from the former contribution and was found to be a linear function of chemical potential of the additive, indicating constant adsorption over a wide range of additive concentrations. Average distances between adsorbed additive ions as calculated from slopes of plots are compatible with lattice parameters of brushite: 0.54 nm for Mg 2+, 0.43 nm for Ba 2+ and 0.86 nm for Cu 2+. With the latter a sharp decrease in growth rate occurred early in the crystallization process, followed by an equally sharp increase to the previous level. When interpreted in terms of the Cabrera-Vermilyea theory of crystal growth inhibition, the results are consistent with an average distance between Cu ions of 0.88 nm, in perfect agreement with the above value.

  13. Effect of electron-nuclei interaction on internuclear motions in slow ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Tolstikhina, Inga Yu.; Tolstikhin, Oleg I.

    2015-10-01

    The electron-nuclei interaction affects the internuclear motion in slow ion-atom collisions, which in turn affects theoretical results for the cross sections of various collision processes. The results are especially sensitive to the details of the internuclear dynamics in the presence of a strong isotope effect on the cross sections, as is the case, e.g., for the charge transfer in low-energy collisions of He2+ with H, D, and T. By considering this system as an example, we show that internuclear trajectories defined by the Born-Oppenheimer (BO) potential in the entrance collision channel, which effectively accounts for the electron-nuclei interaction, are in much better agreement with trajectories obtained in the ab initio electron-nuclear dynamics approach [R. Cabrera-Trujillo et al., Phys. Rev. A 83, 012715 (2011), 10.1103/PhysRevA.83.012715] than the corresponding Coulomb trajectories. We also show that the use of the BO trajectory instead of the Coulomb trajectory in the calculations of the charge-transfer cross sections within the adiabatic approach improves the agreement of the results with ab initio calculations.

  14. Refined BCF-type boundary conditions for mesoscale surface step dynamics

    NASA Astrophysics Data System (ADS)

    Zhao, Renjie; Ackerman, David M.; Evans, James W.

    2015-06-01

    Deposition on a vicinal surface with alternating rough and smooth steps is described by a solid-on-solid model with anisotropic interactions. Kinetic Monte Carlo (KMC) simulations of the model reveal step pairing in the absence of any additional step attachment barriers. We explore the description of this behavior within an analytic Burton-Cabrera-Frank (BCF)-type step dynamics treatment. Without attachment barriers, conventional kinetic coefficients for the rough and smooth steps are identical, as are the predicted step velocities for a vicinal surface with equal terrace widths. However, we determine refined kinetic coefficients from a two-dimensional discrete deposition-diffusion equation formalism which accounts for step structure. These coefficients are generally higher for rough steps than for smooth steps, reflecting a higher propensity for capture of diffusing terrace adatoms due to a higher kink density. Such refined coefficients also depend on the local environment of the step and can even become negative (corresponding to net detachment despite an excess adatom density) for a smooth step in close proximity to a rough step. Our key observation is that incorporation of these refined kinetic coefficients into a BCF-type step dynamics treatment recovers quantitatively the mesoscale step-pairing behavior observed in the KMC simulations.

  15. A multi-step reaction model for ignition of fully-dense Al-CuO nanocomposite powders

    NASA Astrophysics Data System (ADS)

    Stamatis, D.; Ermoline, A.; Dreizin, E. L.

    2012-12-01

    A multi-step reaction model is developed to describe heterogeneous processes occurring upon heating of an Al-CuO nanocomposite material prepared by arrested reactive milling. The reaction model couples a previously derived Cabrera-Mott oxidation mechanism describing initial, low temperature processes and an aluminium oxidation model including formation of different alumina polymorphs at increased film thicknesses and higher temperatures. The reaction model is tuned using traces measured by differential scanning calorimetry. Ignition is studied for thin powder layers and individual particles using respectively the heated filament (heating rates of 103-104 K s-1) and laser ignition (heating rate ∼106 K s-1) experiments. The developed heterogeneous reaction model predicts a sharp temperature increase, which can be associated with ignition when the laser power approaches the experimental ignition threshold. In experiments, particles ignited by the laser beam are observed to explode, indicating a substantial gas release accompanying ignition. For the heated filament experiments, the model predicts exothermic reactions at the temperatures, at which ignition is observed experimentally; however, strong thermal contact between the metal filament and powder prevents the model from predicting the thermal runaway. It is suggested that oxygen gas release from decomposing CuO, as observed from particles exploding upon ignition in the laser beam, disrupts the thermal contact of the powder and filament; this phenomenon must be included in the filament ignition model to enable prediction of the temperature runaway.

  16. Oxidation studies of niobium thin films at room temperature by X-ray reflectivity

    NASA Astrophysics Data System (ADS)

    Sokhey, K. J. S.; Rai, S. K.; Lodha, G. S.

    2010-10-01

    We report the results of growth kinetics of oxidation process on niobium thin film surfaces exposed to air at room temperature by using a surface sensitive non-destructive X-ray reflectivity technique. The oxidation process follows a modified Cabrera-Mott model of thin films. We have shown that the oxide growth is limited by the internal field due to the contact potential which develops during the initial stage of oxidation. The calculated contact potential for 100 and 230 Å thick films is 0.81 ± 0.14 and 1.20 ± 0.11 V respectively. We report that 40% increase in the contact potential increases the growth rate for the first few mono layers of Nb 2O 5 from ˜2.18 to ˜2790 Å/s. The growth rates of oxidation on these samples become similar after the oxide thicknesses of ˜25 Å are reached. We report on the basis of our studies that a protective layer should be grown in situ to avoid oxidation of Nb thin film surface of Nb/Cu cavities.

  17. Geometer energy unified field theory

    NASA Astrophysics Data System (ADS)

    Rivera, Susana; Rivera, Anacleto

    GEOMETER - ENERGY UNIFIED FIELD THEORY Author: Anacleto Rivera Nivón Co-author: Susana Rivera Cabrera This work is an attempt to find the relationship between the Electromagnetic Field and the Gravitational Field. Despite it is based on the existence of Strings of Energy, it is not the same kind of strings that appears on other theories like Superstring Theory, Branas Theory, M - Theory, or any other related string theories. Here, the Strings are concentrated energy lines that vibrates, and experiences shrinking and elongations, absorbing and yielding on each contraction and expansion all that is found in the Universe: matter and antimatter, waves and energy in all manifestations. In contrast to superstring theory, which strings are on the range of the Length of Planck, these Strings can be on the cosmological size, and can contain many galaxies, or clusters, or groups of galaxies; but also they can reach as small sizes as subatomic levels. Besides, and contrary to what it is stated in some other string theories that need the existence of ten or more dimensions, the present proposal sustains in only four particular dimensions. It has been developed a mathematical support that will try to help to improve the understanding of the phenomena that take place at the Universe.

  18. Landau-Zener and Rabi oscillations in the spin-dependent conductance

    NASA Astrophysics Data System (ADS)

    Fernández-Alcázar, L. J.; Pastawski, H. M.

    2014-01-01

    We describe the spin-dependent quantum conductance in a wire where a magnetic field is spatially modulated. The change in direction and intensity of the magnetic field acts as a perturbation that mixes spin projections. This is exemplified by a ferromagnetic nanowire. There the local field varies smoothly its direction generating a domain wall (DW) as described by the well-known Cabrera-Falicov model. Here, we generalize this model to include also a strength modulation. We identify two striking diabatic regimes that appear when such magnetic inhogeneity occurs. 1) If the field strength at the DW is weak enough, the local Zeeman energies result in an avoided crossing. Thus, the spin-flip probability follows the Landau-Zener formula. 2) For strong fields, the spin-dependent conductance shows oscillations as a function of the DW width. We interpret them in terms of Rabi oscillations. Time and length scales obtained from this simplified view show an excellent agreement with the exact dynamical solution of the spin-dependent transport. These results remain valid for other situations involving modulated magnetic structures and thus they open new prospects for the use of quantum interferences in spin-based devices. This paper is dedicated to the memory of the lifelong collaborator Patricia Rebeca Levstein.

  19. Step dynamics in the homoepitaxial growth of 6H-SiC by chemical vapor deposition on 1° offcut substrate using dichlorosilane as Si precursor

    NASA Astrophysics Data System (ADS)

    Omar, Sabih U.; Chandrashekhar, M. V. S.; Chowdhury, Iftekhar A.; Rana, Tawhid A.; Sudarshan, Tangali S.

    2013-05-01

    Step flow epitaxial growth was achieved on 1° offcut 6H-SiC substrate using dichlorosilane (DCS) as the Si precursor. High crystal quality and polytype uniformity were verified by XRD and Raman spectroscopy. Mirror-like surfaces with very few triangular and carrot defects were obtained over a wide range of C/Si ratios. Surface step bunching and step crossover were observed and rms roughness values were measured to be 2-4 nm. N-type doping was achieved by site-competition epitaxy at low C/Si ratios. Growth rates of 0.5-4 μm/h was obtained over a temperature range of 1470-1550 °C. The surface diffusion length of the adatoms on the step terraces was calculated using a model based on the Burton-Cabrera-Frank theory of epigrowth on stepped surfaces. In the experimental temperature range, the surface diffusion length varied from 5 to 13 nm, which is significantly shorter than those reported in literature for epigrowth using the conventional silane precursor. The short diffusion lengths for DCS imply a strong desorption process at the growth front, which is ideal for polytype-matched step-flow growth on low offcut substrates. The understanding of these step dynamics issues is critical for crystal growers using chlorinated gas precursors.

  20. Well-posedness of a two-scale model for liquid phase epitaxy with elasticity

    NASA Astrophysics Data System (ADS)

    Kutter, Michael; Rohde, Christian; Sändig, Anna-Margarete

    2015-08-01

    Epitaxy, a special form of crystal growth, is a technically relevant process for the production of thin films and layers. It can generate microstructures of different morphologies, such as steps, spirals or pyramids. These microstructures are influenced by elastic effects in the epitaxial layer. There are different epitaxial techniques, one being liquid phase epitaxy. Thereby, single particles are deposited out of a supersaturated liquid solution on a substrate where they contribute to the growth process. This article studies a two-scale model including elasticity, introduced in Eck et al. (Eur Phys J Special Topics 177:5-21, 2009) and extended in Eck et al. (2006). It consists of a macroscopic Navier-Stokes system and a macroscopic convection-diffusion equation for the transport of matter in the liquid, and a microscopic problem that combines a phase field approximation of a Burton-Cabrera-Frank model for the evolution of the epitaxial layer, a Stokes system for the fluid flow near the layer and an elasticity system for the elastic deformation of the solid film. Suitable conditions couple the single parts of the model. As the main result, existence and uniqueness of a solution are proven in suitable function spaces. Furthermore, an iterative solving procedure is proposed, which reflects, on the one hand, the strategy of the proof of the main result via fixed point arguments and, on the other hand, can be the basis for a numerical algorithm.

  1. Analytic formulations for one-dimensional decay of rectangular homoepitaxial islands during coarsening on anisotropic fcc (110) surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Chi-Jen; Han, Yong; Walen, Holly; Russell, Selena M.; Thiel, Patricia A.; Evans, James W.

    2013-10-01

    Submonolayer homoepitaxial fcc (110) systems display behavior reflecting strong anisotropy at lower temperatures, including one-dimensional decay during Ostwald ripening of rectangular islands maintaining constant width in the <001> direction. To appropriately describe this behavior, we first develop a refined continuum Burton-Cabrera-Frank formalism, which accounts for a lack of equilibration of island shape and importantly also for inhibited incorporation of adatoms at almost-faceted <1¯10> island edges through effective kinetic coefficients. This formalism is shown to describe accurately the adatom diffusion fluxes between islands and thus island evolution for a complex experimental island configuration, as confirmed by matching results from realistic atomistic simulations for this configuration. This approach also elucidates basic dependencies of flux on island geometry and temperature. Second, a further refinement is presented incorporating separate terrace and edge adatom density fields either in a continuum setting or alternatively in a spatially discrete diffusion equation setting. The second approach allows more flexibility and accuracy in accounting for edge-diffusion kinetics including corner rounding, a lack of equilibration of the edge adatom density at <1¯10> island edges, and the effect of rare kinks on <1¯10> island edges. Significantly, it suggests facile two-way corner rounding at the island periphery during island decay, contrasting the previous picture.

  2. The uptake and effects of lead in small mammals and frogs at a trap and skeet range.

    PubMed

    Stansley, W; Roscoe, D E

    1996-02-01

    This study was performed to evaluate the bioavailability and effects of lead in wildlife at a trap and skeet range. The total lead concentration in a composite soil sample (pellets removed) was 75,000 micrograms/g dry weight. Elevated tissue lead concentrations and depressed ALAD activities in small mammals and frogs indicate that some of the lead deposited at the site is bioavailable. Mean tissue lead concentrations (micrograms/g dry wt.) in white-footed mice (Peromyscus leucopus) at the range liver = 4.98, kidney = 34.9, femur = 245) were elevated (P < 0.01) 5- to 64-fold relative to concentrations in mice from a control area. Tissue lead concentrations in the only shorttail shrew (Blarina brevicauda) captured at the range (liver = 34.1, kidney = 1506, femur = 437) were elevated 35- to 1038-fold. Femur lead concentrations in green frogs (Rana clamitans) at the range (1,728 micrograms/g) were elevated nearly 1000-fold, and the lead concentration in a pooled kidney sample (96.2 micrograms/g) was elevated 67-fold. There was significant depression of blood ALAD activity in mice (P = 0.0384) and depression of blood and liver ALAD activity in frogs (P < 0.001). Hematological and histopathological lesions associated with lead toxicosis were observed in some animals. Hemoglobin concentrations were reduced 6.7% in mice (P = 0.0249), but hematocrit was not significantly affected in mice or frogs. Intranuclear inclusions were present in the renal proximal tubular epithelium of two of the mice and the shrew that were captured at the range, and necrosis of the tubular epithelium was also evident in one of the mice. Kidney:body weight ratios were similar in range and control mice. Soil ingestion may be a significant route of lead uptake in small mammals at the range. However, the tendency of lead to concentrate in the bones rather than in more digestible soft tissues may minimize food chain uptake of lead by predators, especially raptors that regurgitate undigestible material

  3. Sediment TCDD-EQs and EROD and MROD activities in Ranid frogs from agricultural and nonagricultural sites in Michigan (USA).

    PubMed

    Murphy, M B; Hecker, M; Coady, K K; Tompsett, A R; Jones, P D; Newsted, J L; Wong, H L; du Preez, L H; Solomon, K R; Carr, J A; Smith, E E; Kendall, R J; Van der Kraak, G; Giesy, J P

    2006-10-01

    In vitro studies have demonstrated atrazine-mediated induction of 7-ethoxyresorufin O-deethylase (EROD) activity. EROD is an enzyme active in the metabolism of many compounds, including many xenobiotics. These studies have suggested that atrazine may affect reproductive function by altering steroid metabolism. The goal of this study was to determine whether relationships could be detected between measured atrazine concentrations in surface waters and the liver-somatic index (LSI) and EROD and 7-methoxyresorufin O-deethylase (MROD) activities in the livers of ranid frogs. In addition, sediment dioxin toxic equivalents (TCDD-EQs) were determined using the H4IIE-luc cell bioassay. Adult and juvenile green frogs (Rana clamitans), bullfrogs (R. catesbeiana), and Northern leopard frogs (R. pipiens) were collected from areas with extensive corn cultivation and areas where there was little agricultural activity in south central Michigan in the summer of 2003. Atrazine concentrations at nonagricultural sites ranged from less than the limit of quantification (0.17 microg atrazine/L) to 0.23 microg atrazine/L and did not exceed 1.2 microg atrazine/L at agricultural sites. Sediment TCDD-EQs were measurable only at one agricultural site. Of the measured parameters, only LSI values in adult male frogs differed significantly between agricultural and nonagricultural sites, with greater values observed at agricultural sites. In green frogs, EROD and MROD activities were measurable in both adult and juvenile frogs and were similar among sites. Median EROD activities ranged from 13 to 21 pmol/min/mg protein in adult male green frogs and from 5 to 13 pmol/min/mg protein in adult female green frogs. Juvenile frogs had greater EROD and MROD activities than adult frogs. Bullfrogs and leopard frogs had greater activities than did green frogs. Atrazine concentrations were significantly and negatively correlated with MROD activity in adult male green frogs (Spearman R = -0.800). LSI and

  4. Effects of timber harvesting on pond-breeding amphibian persistence: testing the evacuation hypothesis.

    PubMed

    Semlitsch, Raymond D; Conner, Christopher A; Hocking, Daniel J; Rittenhouse, Tracy A G; Harper, Elizabeth B

    2008-03-01

    Numerous studies have documented the decline of amphibians following timber harvest. However, direct evidence concerning the mechanisms of population decline is lacking and hinders attempts to develop conservation or recovery plans and solutions for forest species. We summarized the mechanisms by which abundance of amphibians may initially decline following timber harvest into three testable hypotheses: (1) mortality, (2) retreat, and (3) evacuation. Here, we tested the evacuation hypothesis within a large-scale, replicated experiment. We used drift fences with pitfall traps to capture pond-breeding amphibians moving out of experimental clearcut quadrants and into control quadrants at four replicate arrays located within the Daniel Boone Conservation Area on the upper Ozark Plateau in Warren County, Missouri, USA. During the preharvest year of 2004, only 51.6% of the 312 individuals captured were moving out of pre-clearcut quadrants, and movement did not differ from random. In contrast, during both postharvest years of 2005 and 2006, the number of captures along the quadrant edge increased, and a higher proportion of individuals (59.9% and 56.6%, respectively, by year) were moving out of clearcut quadrants than entering. Salamanders moved out of clearcuts in large percentages (Ambystoma annulatum, 78.2% in 2005, 78.2% in 2006; A. maculatum, 64.0% in 2005, 57.1% in 2006). Frogs and toads also moved out of clearcut quadrants, but in lower percentages (Bufo americanus, 59.6% in 2005, 53.3% in 2006; Rana clamitans, 52.7% in 2006). Salamanders moved out of clearcuts with low-wood treatments more than out of clearcuts with high-wood treatments. Movement of salamanders out of clearcuts was independent of sex. Estimated movement out of clearcuts represented between 8.7% and 35.0% of the total breeding adults captured for two species of salamanders. Although we recognize that some portion of the amphibian population may retreat underground for short periods and others may

  5. Dynamics of suprabenthos-zooplankton communities around the Balearic Islands (western Mediterranean): Influence of environmental variables and effects on the biological cycle of Aristeus antennatus

    NASA Astrophysics Data System (ADS)

    Cartes, J. E.; Madurell, T.; Fanelli, E.; López-Jurado, J. L.

    Dynamics of suprabenthos and zooplankton were analyzed in two areas located in the NW (off Sóller harbour) and S (off Cabrera Archipelago) of Mallorca (Balearic Islands, western Mediterranean) at depths ranging between 135-780 m. Four stations situated respectively at 150 m (shelf-slope break), and at bathyal depths of 350, 650 and 750 m were sampled at bi-monthly intervals during six cruises performed between August 2003 and June 2004. Suprabenthos showed maximum biomass in both areas from late spring to summer (April to August), while minimum biomass was found in autumn (September-November). Though variable, temporal dynamics of zooplankton showed peaks of biomass in late winter and summer (February and June), while minimals occurred in autumn (August-September) and, at bathyal depths, in April. Suprabenthos (abundance; MDS analyses) showed a sample aggregation as a function of depth (3 groups corresponding to the shelf-slope break, upper slope — over 350 m; and the middle, deeper part of the slope — over 650-750 m), without any separation of hauls by season. By contrast, zooplankton samples were separated by season and not by depth. There was evidence of three seasonal groups corresponding to summer (June 2004-August 2003), autumn-winter (September and November 2003, February 2004), and spring (April 2004), being especially well established off Sóller. In general, suprabenthos was significantly correlated with the sediment variables (e.g. total organic matter content (% OM), potential REDOX), whereas zooplankton was almost exclusively dependent on Chl a at the surface, which suggests two different food sources for suprabenthos and zooplankton. The increase of suprabenthos abundance in April-June was paralleled by a sharp increase ( ca. 2.8 times) in the %OM on sediment during the same period, coupled ca. 1-2 months of delay with the peak of surface Chl a recorded in February-March (from satellite imagery data). Suprabenthos biomass was also correlated with

  6. Extreme Subduction Earthquake Scenarios and their Economical Consequences for Mexico City and Guadalajara, Jalisco, Mexico

    NASA Astrophysics Data System (ADS)

    Chavez, M.; Cabrera, E.; Perea, N.

    2007-05-01

    to date seismotectonic, seismological, geophysical, and geotechnical information for the mentioned subduction zones and for MC and G. The economical impacts of the proposed extreme TSS earthquake scenarios for MC and G are fully discussed. We acknowledge the support of DGSCA, UNAM, for using its supercomputer facilities. ----------------------- [1] Nishenko S.P. and Singh SK, BSSA 77, 6, 1987 [2] Chavez M. and Ramirez R., 12th World Conf. Earthq. Eng., 2000 [3] Cabrera E., Chavez M., Madariaga R., Mai M, Frisenda M., Perea N., AGU, Fall Meeting, 2005 [4] Chavez M., Olsen K.B., Cabrera E., 13th World Conf. Earthq. Eng., 2004

  7. Fault segment linkage and growth of the Polopos transpressive fault zone and its influence on Pleistocene drainage captures (southeastern Betics).

    NASA Astrophysics Data System (ADS)

    Giaconia, F.; Booth-Rea, G.; Martínez-Martínez, J. M.; Azañón, J. M.; Villegas, I.

    2012-04-01

    The Polopos fault zoneis a dextral-reverse fault-system that developed under Neogene to Quaternary N/S to NNW/SSE convergence between Africa and Iberia. This fault zone is formed by three main fault segments, the North and South Gafarillos dextral strike-slip faults, and the North Alhamilla reverse fault. The whole fault zone with an approximate length of 30 km has an E/W to ESE/WNW orientation and helicoidal geometry that permits the transfer of oblique SE-directed shortening in Sierra Cabrera to NW-directed shortening along the North Alhamilla reverse fault via vertical dextral Gafarillos fault segments, in between. The north Alhamilla reverse fault to the west of the system produces a fault-propagation fold in the hangingwall and an overturned fold in the footwall cutting through early Tortonian turbidites and folded Quaternary alluvial fans at the north Alhamilla mountain front. The Quaternary paleo-topographic surface formed by the alluvial fan has been displaced approximately 100 m by reverse faulting after 400 - 70 ky with a slip rate ranging between 0.25 and 1.4 mm yr-1. The South Gafarillos fault includes several N90°-110°E-striking segments with dextral and reverse-dextral kinematics. This fault cuts through the southeastern limb of the Alhamilla anticline by a fault segment that separates the basement from Messinian sediments, meanwhile other segments in the Nijar basin further south cut through Pleistocene river strath-terraces.. During the late Miocene the locus of dextral displacement occurred along the North Gafarillos fault segment that linked to a reverse fault segment at the northeast of the Sierra Alhamilla . The North Gafarillos fault segment and its associated mountain front was sealed by Messinian reefs. Since the Messinian, recent fault activity migrated towards the south forming the South Gafarillos fault segments. Fault segment migration displaced the active oblique strike-slip-related mountain fronts from the north towards the southeast

  8. Multifunctional reactive nanocomposite materials

    NASA Astrophysics Data System (ADS)

    Stamatis, Demitrios

    (DSC), were established between MIC and ARM-prepared materials. However, the materials behaved similarly to each other in the ignition experiments. It is proposed that the ignition of both MIC and ARM-prepared materials at the same temperature can be explained by a thermodynamically driven transformation of a protective amorphous alumina into a crystalline polymorph. Low temperature redox reactions in ARM-prepared Al-CuO nanocomposites were characterized using DSC and isothermal microcalorimetry. The results were interpreted using a Cabrera-Mott reaction model. Simultaneous processing of both experimental data sets identified the parameters for the respective Cabrera-Mott kinetics. The low temperature kinetic model was coupled with a multi-step oxidation model describing diffusion-controlled growth of amorphous and gamma-Al2O3 polymorphs. The kinetic parameters for the multistep oxidation model from previous research were adjusted based on DSC measurements. The combined heterogeneous reactions model was used to interpret results of ignition experiments. It is proposed that the heterogeneous reactions considered serve as ignition triggers and ensuing gas release processes contributes to additional heat release and temperature runaway.

  9. Spiral and target patterns in bivalve nacre manifest a natural excitable medium from layer growth of a biological liquid crystal

    PubMed Central

    Cartwright, Julyan H. E.; Checa, Antonio G.; Escribano, Bruno; Sainz-Díaz, C. Ignacio

    2009-01-01

    Nacre is an exquisitely structured biocomposite of the calcium carbonate mineral aragonite with small amounts of proteins and the polysaccharide chitin. For many years, it has been the subject of research, not just because of its beauty, but also to discover how nature can produce such a superior product with excellent mechanical properties from such relatively weak raw materials. Four decades ago, Wada [Wada K (1966) Spiral growth of nacre. Nature 211:1427] proposed that the spiral patterns in nacre could be explained by using the theory Frank [Frank F (1949) The influence of dislocations on crystal growth. Discuss Faraday Soc 5:48–54] had put forward of the growth of crystals by means of screw dislocations. Frank's mechanism of crystal growth has been amply confirmed by experimental observations of screw dislocations in crystals, but it is a growth mechanism for a single crystal, with growth fronts of molecules. However, the growth fronts composed of many tablets of crystalline aragonite visible in micrographs of nacre are not a molecular-scale but a mesoscale phenomenon, so it has not been evident how the Frank mechanism might be of relevance. Here, we demonstrate that nacre growth is organized around a liquid-crystal core of chitin crystallites, a skeleton that the other components of nacre subsequently flesh out in a process of hierarchical self-assembly. We establish that spiral and target patterns can arise in a liquid crystal formed layer by layer through the Burton–Cabrera–Frank [Burton W, Cabrera N, Frank F (1951) The growth of crystals and the equilibrium structure of their surfaces. Philos Trans R Soc London Ser A 243:299–358] dynamics, and furthermore that this layer growth mechanism is an instance of an important class of physical systems termed excitable media. Artificial liquid crystals grown in this way may have many technological applications. PMID:19528636

  10. Functional regulation of P-glycoprotein at the blood-brain barrier in proton-coupled folate transporter (PCFT) mutant mice

    PubMed Central

    Wang, Xueqian; Cabrera, Robert M.; Li, Yue; Miller, David S.; Finnell, Richard H.

    2013-01-01

    Folate deficiency has been associated with many adverse clinical manifestations. The blood-brain barrier (BBB), formed by brain capillary endothelial cells, protects the brain from exposure to neurotoxicants. The function of BBB is modulated by multiple ABC transporters, particularly P-glycoprotein. A proton-coupled folate transporter (PCFT)-deficient mouse has been previously described as a model for systemic folate deficiency. Herein, we demonstrate that exposing mouse brain capillaries to the antiepileptic drug, valproic acid (VPA; 5 μM), significantly increased P-glycoprotein transport function in the wild-type animals. A ligand to the aryl hydrocarbon receptor, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), produced a similar induction of P-glycoprotein, which tightened the BBB, thereby increasing the neuroprotection. However, VPA- or TCDD-induced P-glycoprotein transport was blocked in the PCFT-nullizygous mice, indicating that multiple neuroprotective mechanisms are compromised under folate-deficient conditions. Brain capillaries from S-folinic acid (SFA; 40 mg/kg)-treated PCFT-nullizygous mice exhibited increased P-glycoprotein transport following VPA exposure. This suggests that SFA supplementation restored the normal BBB function. In addition, we show that tight-junction proteins are disintegrated in the PCFT mutant mice. Taken together, these findings strongly suggest that folate deficiency disrupts the BBB function by targeting the transporter and tight junctions, which may contribute to the development of neurological disorders.—Wang, X., Cabrera, R. M., Li, Y., Miller, D. S., Finnell, R. H. Functional regulation of P-glycoprotein at the blood-brain barrier in proton-coupled folate transporter (PCFT) mutant mice. PMID:23212123

  11. Aspen Winter Conferences on High Energy

    SciTech Connect

    multiple speakers, presenters listed on link below

    2011-02-12

    The 2011 Aspen Winter Conference on Particle Physics was held at the Aspen Center for Physics from February 12 to February 18, 2011. Ninety-four participants from ten countries, and several universities and national labs attended the workshop titled, �New Data From the Energy Frontier.� There were 54 formal talks, and a considerable number of informal discussions held during the week. The week�s events included a public lecture (�The Hunt for the Elusive Higgs Boson� given by Ben Kilminster from Ohio State University) and attended by 119 members of the public, and a physics caf� geared for high schoolers that is a discussion with physicists. The 2011 Aspen Winter Conference on Astroparticle physics held at the Aspen Center for Physics was �Indirect and Direct Detection of Dark Matter.� It was held from February 6 to February 12, 2011. The 70 participants came from 7 countries and attended 53 talks over five days. Late mornings through the afternoon are reserved for informal discussions. In feedback received from participants, it is often these unplanned chats that produce the most excitement due to working through problems with fellow physicists from other institutions and countries or due to incipient collaborations. In addition, Blas Cabrera of Stanford University gave a public lecture titled �What Makes Up Dark Matter.� There were 183 members of the general public in attendance. Before the lecture, 45 people attended the physics caf� to discuss dark matter. This report provides the attendee lists, programs, and announcement posters for each event.

  12. Iron oxidation kinetics for H-2 and CO production via chemical looping

    SciTech Connect

    Stehle, RC; Bobek, MM; Hahn, DW

    2015-01-30

    Solar driven production of fuels by means of an intermediate reactive metal for species splitting has provided a practical and potentially efficient pathway for disassociating molecules at significantly lower thermal energies. The fuels of interest are of or derive from the separation of oxygen from H2O and CO2 to form hydrogen and carbon monoxide, respectively. The following study focuses on iron oxidation through water and CO2 splitting to explore the fundamental reaction kinetics and kinetic rates that are relevant to these processes. In order to properly characterize the reactive metal potential and to optimize a scaled-up solar reactor system, a monolith-based laboratory reactor was implemented to investigate reaction temperatures over a range from 990 to 1400 K. The presence of a single, solid monolith as a reacting surface allowed for a limitation in mass transport effects in order to monitor kinetically driven reaction steps. The formation of oxide layers on the iron monoliths followed Cabrera-Mott models for oxidation of metals with kinetic rates being measured using real-time mass spectrometry to calculate kinetic constants and estimate oxide layer thicknesses. Activation energies of 47.3 kJ/mol and 32.8 kJ/mol were found for water-splitting and CO2 splitting, respectively, and the conclusions of the independent oxidation reactions where applied to experimental results for syngas (H-2-CO) production to explore ideal process characteristics. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  13. Kinetic model of impurity poisoning during growth of calcite

    SciTech Connect

    DeYoreo, J; Wasylenki, L; Dove, P; Wilson, D; Han, N

    2004-05-18

    The central role of the organic component in biologically controlled mineralization is widely recognized. These proteins are characterized by a high proportion of acidic amino acid residues, especially aspartate, Asp. At the same time, biomineralization takes place in the presence of a number of naturally-occurring, inorganic impurities, particularly Mg and Sr. In an attempt to decipher the controls on calcite growth imposed by both classes of modifiers, we have used in situ AFM to investigate the dependence of growth morphology and step kinetics on calcite in the presence of Sr{sup 2+}, as well as a wide suite of Aspartic acid-bearing polypeptides. In each case, we observe a distinct and step-specific modification. Most importantly, we find that the step speed exhibits a characteristic dependence on impurity concentration not predicted by existing crystal growth models. While all of the impurities clearly induce appearance of a 'dead zone,' neither the width of that dead zone nor the dependence of step speed on activity or impurity content can be explained by invoking the Gibbs-Thomson effect, which is the basis for the Cabrera-Vermilyea model of impurity poisoning. Common kink-blocking models also fail to explain the observed dependencies. Here we propose a kinetic model of inhibition based on a 'cooperative' effect of impurity adsorption at adjacent kink sites. The model is in qualitative agreement with the experimental results in that it predicts a non-linear dependence of dead zone width on impurity concentration, as well as a sharp drop in step speed above a certain impurity content. However, a detailed model of impurity adsorption kinetics that give quantitative agreement with the data has yet to be developed.

  14. The SOFeX Group

    NASA Astrophysics Data System (ADS)

    Coale, K. H.

    2002-12-01

    The SOFeX Group is comprised of the following institutions and individuals, all of whose participation resulted in a successful experiment. Moss Landing Marine Laboratories: K. Coale, C. Hunter, M. Gordon, S. Tanner, W. Wang, N. Ladizinsky, D. Cooper, G. Smith, J. Brewster; Monterey Bay Aquarium Research Institute: K. Johnson, F. Chavez, S. Fitzwater, P. Strutton, G. Elrod, Z. Chase, E. Drake, J. Plant; Oregon State University: B. Hales, J. Barth, L.Bandstra, P. Covert, D. Hubbard, J. Jennings, S. Pierce, E. Scholz; Lamont Doherty Earth Observatory: T. Takahashi; Duke University: R. Barber, V. Lance, D. Stube, A. Hilting, M. Hiscock, A. Apprill, C. Van Hilst, ; Virginia Institute of Marine Science: W. Smith, H. Ducklow, L. Delizo, J. Oliver, E. Bailey, J. Peloquin, R. Daniels, J. Bauer; University Of Hawaii: M. Landry, R. Bidigare, S. Brown, N. Cassar, B. Twining, K. Selph, C. Sheridan; NOAA Atlantic Oceanographic and Meteorological Laboratory: R. Wanninkhof, K. Sullivan, C. Neill; University of Miami: F. Millero, X. Zhu, W. Hiscock, V. Koehler, A. Cabrera; University of Calif. Lawrence Berkeley National Laboratory: J. Bishop, T. Wood, C. Guay, P. Lam; Rutgers University: P. Falkowski, Z. Kolber, R. Nicolayson, S. Tozzi, M. Gorbunov, M. Koblizek; University of Massachusets: M. Altabet, M. McIlvan, D. Timothy; New Mexico Tech.: Oliver Wingenter; San Francisco State Univ. - Romberg Tiburon Center: W. Cochlan, J. Herndon; University of Calif. Santa Cruz: R. Kudela, A. Roberts; Univ. of Calif. Santa Barbara: M. Brezinski, J. Jones, M. Demarest; Massachusets Inst. of Technology: S. Chisolm, Z. Johnson; Woods Hole Oceanographic Institute: K. Buesseler, J. Andrews, G. Crossin, S. Pike, J. Tegeder, C. Herbold, K. Mahoney, M.Coggeshell ; University of East Anglia: L. Houghton, L. Goldson, A. Watson, J. Ledwell; Institute of Marine Research, Kiel: Peter Croot; University of Otago: R. Frew, E. Abraham, P. Boyd.

  15. A Cantilever-based apparatus for detecting micron-scale deviations from Newtonian gravity

    NASA Astrophysics Data System (ADS)

    Kapitulnik, Aharon

    2009-03-01

    To test new theories of physics beyond the Standard Model, we have built a low temperature probe to measure forces as small as 10-18 N between masses separated by distances on the order of 20 microns. Our experiment is fundamentally a Cavendish-type experiment in the sense that its purpose is to directly measure the force between two masses [1]. A cryogenic helium gas bearing is used to rotate a disc containing a drive mass pattern of alternating density under a small test mass mounted on a micromachined cantilever. Any mass-dependent force between the two will produce a time-varying force on the test mass, and consequently a time-varying displacement of the cantilever. This displacement is read out with a laser interferometer, and the position of the drive mass is simultaneously recorded using an optical encoder. The displacement is then averaged over many cycles and converted to a force using measured properties of the cantilever. This AC ``lock-in'' type measurement enables significant noise rejection and allows us to operate on resonance to take advantage of the cantilever's high quality factor. A novel feature of the apparatus is the utilization of feedback regulation of the response of the microcantilever using the radiation pressure of a laser. Our approach does not require a high-finesse cavity, and the feedback force is due solely to the momentum of the photons in the second laser. [4pt] [1] D.M. Weld, J. Xia, B. Cabrera, and A. Kapitulnik, Phys. Rev. D 77, 062006 (2008).

  16. Acute Effects of Contract-Relax Stretching vs. TENS in Young Subjects With Anterior Knee Pain: A Randomized Controlled Trial.

    PubMed

    Valenza, Marie C; Torres-Sánchez, Irene; Cabrera-Martos, Irene; Valenza-Demet, Gerald; Cano-Cappellacci, Marcelo

    2016-08-01

    Valenza, MC, Torres-Sánchez, I, Cabrera-Martos, I, Valenza-Demet, G, and Cano-Cappellacci, M. Acute effects of contract-relax stretching vs. TENS in young subjects with anterior knee pain: A randomized controlled trial. J Strength Cond Res 30(8): 2271-2278, 2016-The aim of this study was to examine the immediate effects on pressure point tenderness, range of motion (ROM), and vertical jump (VJ) of contract-relax stretching vs. transcutaneous electrical nerve stimulation (TENS) therapy in individuals with anterior knee pain (AKP). Eighty-four subjects with AKP were randomly assigned to 1 of 3 different intervention groups: a contract-relax stretching group (n = 28), a TENS intervention group (n = 28), and a control group (n = 28). The participants included in the sample were both sex (37.5% men vs. 62.5% women) at a mean age of 21 years, with mean values of height and weight of 169 cm and 64 kg, respectively. The main outcome measures were knee ROM, pressure pain threshold (PPT), and VJ. The participants were assessed at baseline and immediately after treatment. In the case of VJ, at baseline, immediately after the intervention, at 3 and at 6 minutes posttreatment. The data analysis showed that PPT scores of participants in the stretching and TENS group significantly increased from pretest to posttest (p ≤ 0.05). A significant increase pre- to posttreatment in ROM (p < 0.001) was also observed in both treatment groups. In VJ measures, TENS and stretching groups showed significant differences between preintervention and all postintervention values (p ≤ 0.05), whereas no significant differences were found in the control group. In conclusion, the results show significant pre-to-post-treatment effects in PPT, ROM, and VJ from both contract-relax stretching and TENS in young subjects with AKP. PMID:27457916

  17. Size-Expanded yDNA bases: An Ab Initio Study

    SciTech Connect

    Fuentes-Cabrera, Miguel A; Sumpter, Bobby G; Lipkowski, Pawel; Wells, Jack C

    2006-01-01

    xDNA and yDNA are new classes of synthetic nucleic acids characterized by having base-pairs with one of the bases larger than the natural congeners. Here these larger bases are called x- and y-bases. We recently investigated and reported the structural and electronic properties of the x-bases (Fuentes-Cabrera et al. J. Phys. Chem. B 2005, 109, 21135-21139). Here we extend this study by investigating the structure and electronic properties of the y-bases. These studies are framed within our interest that xDNA and yDNA could function as nanowires, for they could have smaller HOMO-LUMO gaps than natural DNA. The limited amount of experimental structural data in these synthetic duplexes makes it necessary to first understand smaller models and, subsequently, to use that information to build larger models. In this paper, we report the results on the chemical and electronic structure of the y-bases. In particular, we predict that the y-bases have smaller HOMO-LUMO gaps than their natural congeners, which is an encouraging result for it indicates that yDNA could have a smaller HOMO-LUMO gap than natural DNA. Also, we predict that the y-bases are less planar than the natural ones. Particularly interesting are our results corresponding to yG. Our studies show that yG is unstable because it is less aromatic and has a Coulombic repulsion that involves the amino group, as compared with a more stable tautomer. However, yG has a very small HOMO-LUMO gap, the smallest of all the size-expanded bases we have considered. The results of this study provide useful information that may allow the synthesis of an yG-mimic that is stable and has a small HOMO-LUMO gap.

  18. Simulation and experiment of substrate aluminum grain orientation dependent self-ordering in anodic porous alumina

    NASA Astrophysics Data System (ADS)

    Cheng, Chuan; Ng, K. Y.; Aluru, N. R.; Ngan, A. H. W.

    2013-05-01

    Recent experiments have indicated a strong influence of the substrate grain orientation on the self-ordering in anodic porous alumina. Anodic porous alumina with straight pore channels grown in a stable, self-ordered manner is formed on (001) oriented Al grain, while disordered porous pattern is formed on (101) oriented Al grain with tilted pore channels growing in an unstable manner. In this work, numerical simulation of the pore growth process is carried out to understand this phenomenon. The rate-determining step of the oxide growth is assumed to be the Cabrera-Mott barrier at the oxide/electrolyte (o/e) interface, while the substrate is assumed to determine the ratio β between the ionization and oxidation reactions at the metal/oxide (m/o) interface. By numerically solving the electric field inside a growing porous alumina during anodization, the migration rates of the ions and hence the evolution of the o/e and m/o interfaces are computed. The simulated results show that pore growth is more stable when β is higher. A higher β corresponds to more Al ionized and migrating away from the m/o interface rather than being oxidized, and hence a higher retained O:Al ratio in the oxide. Experimentally measured oxygen content in the self-ordered porous alumina on (001) Al is indeed found to be about 3% higher than that in the disordered alumina on (101) Al, in agreement with the theoretical prediction. The results, therefore, suggest that ionization on (001) Al substrate is relatively easier than on (101) Al, and this leads to the more stable growth of the pore channels on (001) Al.

  19. Oxidation mechanism in metal nanoclusters: Zn nanoclusters to ZnO hollow nanoclusters

    NASA Astrophysics Data System (ADS)

    Mahapatra, A. K.; Bhatta, U. M.; Som, T.

    2012-10-01

    Zn nanoclusters (NCs) are deposited by the low-energy cluster beam deposition technique. The mechanism of oxidation is studied by analysing their compositional and morphological evolution over a long span of time (three years) due to exposure to ambient atmosphere. It is concluded that the mechanism proceeds in two steps. In the first step, the shell of ZnO forms over Zn NCs rapidly up to a certain limiting thickness: within a few days—depending upon the size—Zn NCs are converted to Zn-ZnO (core-shell), Zn-void-ZnO, or hollow ZnO type NCs. Bigger than ˜15 nm become Zn-ZnO (core-shell) type: among them, NCs above ˜25 nm could retain their initial geometrical shapes (namely triangular, hexagonal, rectangular and rhombohedral), but ˜25 to 15 nm size NCs become irregular or distorted geometrical shapes. NCs between ˜15 to 5 nm become Zn-void-ZnO type, and smaller than ˜5 nm become ZnO hollow sphere type, i.e. ZnO hollow NCs. In the second step, all Zn-void-ZnO and Zn-ZnO (core-shell) structures are converted to hollow ZnO NCs in a slow and gradual process, and the mechanism of conversion proceeds through expansion in size by incorporating ZnO monomers inside the shell. The observed oxidation behaviour of NCs is compared with theory of Cabrera-Mott on low-temperature oxidation of metal.

  20. On the mechanisms of cation injection in conducting bridge memories: The case of HfO2 in contact with noble metal anodes (Au, Cu, Ag)

    NASA Astrophysics Data System (ADS)

    Saadi, M.; Gonon, P.; Vallée, C.; Mannequin, C.; Grampeix, H.; Jalaguier, E.; Jomni, F.; Bsiesy, A.

    2016-03-01

    Resistance switching is studied in HfO2 as a function of the anode metal (Au, Cu, and Ag) in view of its application to resistive memories (resistive random access memories, RRAM). Current-voltage (I-V) and current-time (I-t) characteristics are presented. For Au anodes, resistance transition is controlled by oxygen vacancies (oxygen-based resistive random access memory, OxRRAM). For Ag anodes, resistance switching is governed by cation injection (Conducting Bridge random access memory, CBRAM). Cu anodes lead to an intermediate case. I-t experiments are shown to be a valuable tool to distinguish between OxRRAM and CBRAM behaviors. A model is proposed to explain the high-to-low resistance transition in CBRAMs. The model is based on the theory of low-temperature oxidation of metals (Cabrera-Mott theory). Upon electron injection, oxygen vacancies and oxygen ions are generated in the oxide. Oxygen ions are drifted to the anode, and an interfacial oxide is formed at the HfO2/anode interface. If oxygen ion mobility is low in the interfacial oxide, a negative space charge builds-up at the HfO2/oxide interface. This negative space charge is the source of a strong electric field across the interfacial oxide thickness, which pulls out cations from the anode (CBRAM case). Inversely, if oxygen ions migration through the interfacial oxide is important (or if the anode does not oxidize such as Au), bulk oxygen vacancies govern resistance transition (OxRRAM case).

  1. Long-term records of trace metal content of western Mediterranean seagrass (Posidonia oceanica) meadows: Natural and anthropogenic contributions

    NASA Astrophysics Data System (ADS)

    Tovar-SáNchez, Antonio; Serón, Juan; Marbã, Núria; Arrieta, Jesús M.; Duarte, Carlos M.

    2010-06-01

    We discuss Al, Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn contents in seagrass Posidonia oceanica rhizomes from the Balearic Archipelago for the last 3 decades. Time series of metal concentration in P. oceanica were measured by dating rhizomes using retrospective procedures. The highest concentrations of Al (174.73 μg g-1), Cd (3.56 μg g-1), Cr (1.34 μg g-1), Cu (32.15 μg g-1), Pb (8.51 μg g-1), and Zn (107.14 μg g-1) were measured in meadows located around the largest and most densely populated island (Mallorca Island). There was a general tendency for Ag concentration to decrease with time (up to 80% from 1990 to 2005 in sample from Mallorca Island), which could be attributed to a reduction of the anthropogenic sources. Nickel and Zn concentrations were the unique elements that showed a consistent temporal trend in all samples, increasing their concentrations since year 1996 at all studied stations; this trend matched with the time series of UV-absorbing aerosols particles in the air (i.e., aerosols index) over the Mediterranean region (r2: 0.78, p < 0.001 for Cabrera Island), suggesting that P. oceanica could be an efficient recorder of dust events. A comparison of enrichment factors in rhizomes relative to average crustal material indicates that suspended aerosol is also the most likely source for Cr and Fe to P. oceanica.

  2. Passive Microwave Spectral Imaging of Amospheric Structure

    NASA Technical Reports Server (NTRS)

    Staelin, David H.; Rosenkranz, Philip W.

    1998-01-01

    The primary objective of this research was to improve the scientific foundation necessary to full realization of the meteorological potential of the NOAA Advanced Microwave Sounding Unit (AMSU) recently first launched on the NOAA-15 satellite in May, 1998. These advances were made in four main areas: (1) improvements, based on aircraft observations, in the atmospheric transmittance expressions used for interpreting AMSU and similar data; (2) development of neural network retrieval methods for cloud top altitude estimates of approximately 1-km accuracy under cirrus shields--the altitude is that of the larger ice particles aloft, which is related to precipitation rate; (3) analysis of early AMSU flight data with respect to its precipitation sensitivity and fine-scale thermal structure; and (4) improvements to the 54-GHz and 118-GHz MTS aircraft imaging spectrometer now operating on the NASA ER-2 aircraft. More specifically, the oxygen transmittance expressions near 118 GHz were in better agreement with aircraft data when the temperature dependence exponent of the 118.75-GHz linewidth was increased from the MPM92 value (Liebe et al., 1992) of 0.8 to 0.97+/-0.03. In contrast, the observations 52.5-55.8 GHz were consistent with the MPM92 model. Neural networks trained on comparisons of 118-GHz spectral data and coincident stereoscopic video images of convective cells observed from 20-km altitude yielded agreement in their peak altitudes within as little as 1.36 km rms, much of which is stereoscopic error. Imagery using these methods produced useful characterizations for Cyclone Oliver in 1993 and other storms (Schwartz et al., 1996; Spina et al., 1998). Similar neural network techniques yielded simulated rms errors in relative humidity retrievals of 6-14 percent over ocean and 6-15 percent over land at pressure levels from 1013 to 131 mbar (Cabrera-Mercader and Staelin, 1995).

  3. Utilization of Anodized Aluminum Oxide Substrate for the Growth of ZnO Microcrystals on Polygonized Spirals

    NASA Astrophysics Data System (ADS)

    Deulkar, Sundeep H.; Bhosale, C. H.; Huang, Jow-Lay

    2015-04-01

    Anodized Aluminum Oxide (AAO) has been utilized as a substrate for the screw dislocation assisted growth of polygonize spirals (PS) of ZnO with diameter of the order of 230 μm by Chemical Vapour Deposition (CVD) process. Stoichiometric ZnO microcrystals nucleated on the terraces and tops of these polygonized spirals. Stress inherent in the ZnO polygonized spiral morphology ( 3.57 GPa) was deciphered from the values of the magnitude of shift in observed 2θ values of Glancing Incidence angle XRD (GIXRD) peaks from the standard values (JCPDS 36-1451) for hexagonal Zincite. The growth mechanism of these PS was explained albeit to a limited extent on the basis of the Burton, Cabrera and Frank (BCF) theory and its later modification, wherein data obtained from exsitu SEM measurements concomitant with numerical analysis was utilized to decipher values of the critical radius and supersaturation ratios. Nucleation of ZnO microcrystals on the PS was explained on the basis of the supersaturation ratio and the plausible values of diffusion lengths, existent on the summits of these PS. Retardation of the step rotation of the PS, due to elastic stress around the dislocation source and the Gibbs-Thomson effect, was explained on the basis of numerical coefficient ω0, the dimensionless frequency of spiral rotation. Role of stress in inhibition of ZnO nucleation on PS of smaller heights and with larger supersaturation ratio, has been discussed albeit qualitatively. The optical characteristics of a single ZnO microcrystal has been analyzed by room temperature CL measurements in the wavelength range 350 nm to 650 nm, revealing a single high intensity peak at 382 nm corresponding to a excitonic bandgap of 3.25 eV.

  4. Long-lived radionuclides in residues from operation and decommissioning of nuclear power plants

    NASA Astrophysics Data System (ADS)

    López-Gutiérrez, J. M.; Gómez-Guzmán, J. M.; Chamizo, E.; Peruchena, J. I.; García-León, M.

    2013-01-01

    Radioactive residues, in order to be classified as Low-Level Waste (LLW), need to fulfil certain conditions; the limitation of the maximum activity from long-lived radionuclides is one of these requirements. In order to verify compliance to this limitation, the abundance of these radionuclides in the residue must be determined. However, performing this determination through radiometric methods constitutes a laborious task. In this work, 129I concentrations, 239+240Pu activities, and 240Pu/239Pu ratios are determined in low-level radioactive residues, including resins and dry sludge, from nuclear power plants in Spain. The use of Accelerator Mass Spectrometry (AMS) enables high sensitivities to be achieved, and hence these magnitudes can be re determined with good precision. Results present a high dispersion between the 129I and 239+240Pu activities found in various aliquots of the same sample, which suggests the existence of a mixture of resins with a variety of histories in the same container. As a conclusion, it is shown that activities and isotopic ratios can provide information on the processes that occur in power plants throughout the history of the residues. Furthermore, wipes from the monitoring of surface contamination of the José Cabrera decommissioning process have been analyzed for 129I determination. The wide range of measured activities indicates an effective dispersal of 129I throughout the various locations within a nuclear power plant. Not only could these measurements be employed in the contamination monitoring of the decommissioning process, but also in the modelling of the presence of other iodine isotopes.

  5. Nanostructured silicon via metal assisted catalyzed etch (MACE): chemistry fundamentals and pattern engineering.

    PubMed

    Toor, Fatima; Miller, Jeffrey B; Davidson, Lauren M; Nichols, Logan; Duan, Wenqi; Jura, Michael P; Yim, Joanne; Forziati, Joanne; Black, Marcie R

    2016-10-14

    There are a range of different methods to generate a nanostructured surface on silicon (Si) but the most cost effective and optically interesting is the metal assisted wet chemical etching (MACE) (Koynov et al 2006 Appl. Phys. Lett. 88 203107). MACE of Si is a controllable, room-temperature wet-chemical technique that uses a thin layer of metal to etch the surface of Si, leaving behind various nano- and micro-scale surface features or 'black silicon'. MACE-fabricated nanowires (NWs) provide improved antireflection and light trapping functionality (Toor et al 2016 Nanoscale 8 15448-66) compared with the traditional 'iso-texturing' (Campbell and Green 1987 J. Appl. Phys. 62 243-9). The resulting lower reflection and improved light trapping can lead to higher short circuit currents in NW solar cells (Toor et al 2011 Appl. Phys. Lett. 99 103501). In addition, NW cells can have higher fill factors and voltages than traditionally processed cells, thus leading to increased solar cell efficiencies (Cabrera et al 2013 IEEE J. Photovolt. 3 102-7). MACE NW processing also has synergy with next generation Si solar cell designs, such as thin epitaxial-Si and passivated emitter rear contact (Toor et al 2016 Nanoscale 8 15448-66). While several companies have begun manufacturing black Si, and many more are researching these techniques, much of the work has not been published in traditional journals and is publicly available only through conference proceedings and patent publications, which makes learning the field challenging. There have been three specialized review articles published recently on certain aspects of MACE or black Si, but do not present a full review that would benefit the industry (Liu et al 2014 Energy Environ. Sci. 7 3223-63; Yusufoglu et al 2015 IEEE J. Photovolt. 5 320-8; Huang et al 2011 Adv. Mater. 23 285-308). In this feature article, we review the chemistry of MACE and explore how changing parameters in the wet etch process effects the resulting texture

  6. Pressure Changes before and after Explosive Rhyolitic Bomb Ejection at Chaiten, Chile Recorded By Water Diffusion Profiles Around Tuffisite Veins

    NASA Astrophysics Data System (ADS)

    Tuffen, H.; McGowan, E.; Castro, J. M.; Berlo, K.; James, M. R.; Owen, J.; Schipper, C. I.; Wadsworth, F. B.; Saubin, E.; Wehbe, K.

    2014-12-01

    seismicity at lava domes[4], but with vein formation arguably driven by hydrofracture[5], rather than shear failure. 1 Schipper CI et al, 2013 JVGR 262, 25-37. 2 Castro JM et al 2012, EPSL 333-334, 63-69. 3 Cabrera A et al 2011, Geology 39, 67-70. 4 Neuberg JW et al 2006, JVGR 153, 37-50. 5 Heiken G et al 1988, JGR 93, 4335-4350.

  7. Inhibition of calcium oxalate monohydrate growth by citrate and the effect of the background electrolyte

    NASA Astrophysics Data System (ADS)

    Weaver, Matthew L.; Qiu, S. Roger; Hoyer, John R.; Casey, William H.; Nancollas, George H.; De Yoreo, James J.

    2007-08-01

    Pathological mineralization is a common phenomenon in broad range of plants and animals. In humans, kidney stone formation is a well-known example that afflicts approximately 10% of the population. Of the various calcium salt phases that comprise human kidney stones, the primary component is calcium oxalate monohydrate (COM). Citrate, a naturally occurring molecule in the urinary system and a common therapeutic agent for treating stone disease, is a known inhibitor of COM. Understanding the physical mechanisms of citrate inhibition requires quantification of the effects of both background electrolytes and citrate on COM step kinetics. Here we report the results of an in situ AFM study of these effects, in which we measure the effect of the electrolytes LiCl, NaCl, KCl, RbCl, and CsCl, and the dependence of step speed on citrate concentration for a range of COM supersaturations. We find that varying the background electrolyte results in significant differences in the measured step speeds and in step morphology, with KCl clearly producing the smallest impact and NaCl the largest. The kinetic coefficient for the former is nearly three times larger than for the latter, while the steps change from smooth to highly serrated when KCl is changed to NaCl. The results on the dependence of step speed on citrate concentration show that citrate produces a dead zone whose width increases with citrate concentration as well as a continual reduction in kinetic coefficient with increasing citrate level. We relate these results to a molecular-scale view of inhibition that invokes a combination of kink blocking and step pinning. Furthermore, we demonstrate that the classic step-pinning model of Cabrera and Vermilyea (C-V model) does an excellent job of predicting the effect of citrate on COM step kinetics provided the model is reformulated to more realistically account for impurity adsorption, include an expression for the Gibbs-Thomson effect that is correct for all supersaturations

  8. Nanostructured silicon via metal assisted catalyzed etch (MACE): chemistry fundamentals and pattern engineering

    NASA Astrophysics Data System (ADS)

    Toor, Fatima; Miller, Jeffrey B.; Davidson, Lauren M.; Nichols, Logan; Duan, Wenqi; Jura, Michael P.; Yim, Joanne; Forziati, Joanne; Black, Marcie R.

    2016-10-01

    There are a range of different methods to generate a nanostructured surface on silicon (Si) but the most cost effective and optically interesting is the metal assisted wet chemical etching (MACE) (Koynov et al 2006 Appl. Phys. Lett. 88 203107). MACE of Si is a controllable, room-temperature wet-chemical technique that uses a thin layer of metal to etch the surface of Si, leaving behind various nano- and micro-scale surface features or ‘black silicon’. MACE-fabricated nanowires (NWs) provide improved antireflection and light trapping functionality (Toor et al 2016 Nanoscale 8 15448-66) compared with the traditional ‘iso-texturing’ (Campbell and Green 1987 J. Appl. Phys. 62 243-9). The resulting lower reflection and improved light trapping can lead to higher short circuit currents in NW solar cells (Toor et al 2011 Appl. Phys. Lett. 99 103501). In addition, NW cells can have higher fill factors and voltages than traditionally processed cells, thus leading to increased solar cell efficiencies (Cabrera et al 2013 IEEE J. Photovolt. 3 102-7). MACE NW processing also has synergy with next generation Si solar cell designs, such as thin epitaxial-Si and passivated emitter rear contact (Toor et al 2016 Nanoscale 8 15448-66). While several companies have begun manufacturing black Si, and many more are researching these techniques, much of the work has not been published in traditional journals and is publicly available only through conference proceedings and patent publications, which makes learning the field challenging. There have been three specialized review articles published recently on certain aspects of MACE or black Si, but do not present a full review that would benefit the industry (Liu et al 2014 Energy Environ. Sci. 7 3223-63 Yusufoglu et al 2015 IEEE J. Photovolt. 5 320-8 Huang et al 2011 Adv. Mater. 23 285-308). In this feature article, we review the chemistry of MACE and explore how changing parameters in the wet etch process effects the resulting

  9. Aragonian stratigraphy reconsidered, and a re-evaluation of the middle Miocene mammal biochronology in Europe

    NASA Astrophysics Data System (ADS)

    Daams, R.; van der Meulen, A. J.; Alvarez Sierra, M. A.; Peláez-Campomanes, P.; Krijgsman, W.

    1999-02-01

    The recently collected fauna of Armantes 1A in Chron C5Br of the Armantes section necessitates reinterpretation of the previous bio- and magnetostratigraphical correlations between the Armantes and Vargas sections (Calatayud-Daroca Basin, Central Spain) [W. Krijgsman, M. Garcés, C.G. Langereis, R. Daams, J. van Dam, A.J. van der Meulen, J. Agustı´, L. Cabrera, A new chronology for the Middle to Late Miocene continental record in Spain, Earth Planet. Sci. Lett. 142 (1996) 367-380]. The long reversal in the Vargas section is now correlated to C5Br, instead of to C5Cr, on the basis of the biostratigraphical correlation of Armantes 1A to the faunas of Fuente Sierra 2 and 3 (in the Vargas section), which are situated in the basal part of the Middle Aragonian (MN5). This leads to the revised age of 16.0 Ma for the Early-Middle Aragonian (MN 4/5) boundary. Our age estimate of the MN5/6 boundary is maintained at ca. 13.75 Ma. The Vargas section is now considered to start in Chron C5Cn.2r and to end in C5Bn.1n. As a result of the revised correlation the duration of the time gap between the fossiliferous parts of Vargas and the younger Aragón section, previously estimated as ca. 1.5 Myr, is now reduced to less than 200,000 years. The tie points of the European mammal units (MN4-MN6) to the geomagnetic polarity time scale [F.F. Steininger, W.A. Berggren, D.V. Kent, R.L. Bernor, S. Sen, J. Agustı´, Circum-Mediterranean Neogene (Miocene and Pliocene) marine-continental chronologic correlations of European mammal units, in: R.L Bernor, V. Fahlbusch, H.-W. Mittmann (Eds.), The Evolution of Western Eurasian Neogene Mammal Faunas, Columbia Univ. Press, New York, 1996, pp. 7-46] are evaluated. Our age estimates of the MN4/5 and MN5/6 boundaries are compatible with the new magnetostratigraphic calibration of middle Miocene mammal zones in the Swiss Molasse basin [O. Kempf, T. Bolliger, D. Kälin, B. Engesser, A. Matter, New magnetostratigraphic calibration of Early to Middle

  10. Characterization and remediation of 91B radioactive waste sites under performance based contracts at Lackland Air Force Base, San Antonio, Texas

    SciTech Connect

    Trujillo, P.A.; Anderson, K.D.

    2007-07-01

    This paper describes the challenges behind the implementation of the characterization, remediation, and the Site Closure for three 91b Radioactive Wastes under a Performance Based Contract at Lackland Air Force Base, San Antonio, Texas. The Defense Environmental Restoration Program (DERP) was established by Section 211 of the Superfund Amendments and Reauthorization Act of 1986 (SARA). A part of the DERP provides for the cleanup of hazardous substances associated with past Department of Defense (DoD) activities and is consistent with the provisions of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). It is the Air Force Installation Restoration Program (IRP) that has responsibility for the cleanup activities associated with CERCLA. Under contract to the Air Force Center for Environmental Excellence (AFCEE), the ECC Project Team, that included ECC, Cabrera Services, and Malcolm Pirnie, was responsible for the implementation of the actions at three sites. The three IRP (91b) sites included RW015, a 0.02 square kilometer (5.5 acre) site, RW017 a 0.003 square kilometer (0.9 acre) site, and RW033 an 0.356 square kilometer (88 acre) site. Adding to the complexities of the project were issues of archaeological areas of interest, jurisdictional wetlands, land open to hunting, issues of security as well as compliance to the myriad of air force base rules, regulations, and Air Force Instructions (AFI). The award of the project task order was July of 2005, the project plan phase started in July of 2005 followed by the remedy implementation that included characterization and remediation as required reached completion in June of 2006. The project closure including the development and approval final status survey reports, proposed plans, and decision documents that parallel the CERCLA process was initiated in June of 2006 and is expected to reach completion in August of 2007. This paper will focus on the issues of working to achieve radiological

  11. Tsunami deposits related to Fogo flank failure (Cape Verde Islands)

    NASA Astrophysics Data System (ADS)

    Paris, Raphael; Chevalier, Joel; Lavigne, Franck

    2010-05-01

    Oceanic shield volcanoes are prone to massive flank failures involving dozens to hundreds of km³. Fogo active volcano (Cape Verde Islands) is nested in a large horseshoe shaped caldera opened to the east. This volcano-tectonic structure could be the result of past failures of the edifice (Day et al., 1999). Debris avalanche deposits were identified offshore (Masson et al., 2008). The volume of the last collapse (> 62 ka) ranges between 130 and 160 km³, making the hypothesis for a past giant tsunami highly probable. Santiago island is located 50 km east of Fogo island. The west coast of Santiago may have been severely affected by the tsunami. A field survey was carried out in March 2009. Surprisingly, tsunami deposits were found only in Tarrafal, where a large bay may have amplified the wave and provided sediments. Elsewhere, no evidences of tsunami were found. The tsunami deposits appear as marine conglomerate in discontinuity above a reddish to yellowish paleo-soil. Nice cross-sections were found along the coast, in the northern part of the Tarrafal Bay. The thickness apparently increases landward (up to 4 m). The deposits consist in stacked units of pebbles or boulders, with numerous marine bioclasts (shells, corals, coralline algae). The basal contact with the paleo-soil displays scour-and-fill features. These tsunami deposits are similar to those previously described by Pérez-Torrado et al. (2006) in the Canary Islands. References Day, S.J., Heleno da Silva, S.I.N., Fonseca, J.F.B.D., 1999. A past giant lateral collapse and present-day flank instability of Fogo, Cape Verde Islands. Journal of Volcanology and Geothermal Research 99, 191-218. Masson, D.G., Le Bas, T.P., Grevemeyer, I., Weinrebe, W., 2008. Flank collapse and large-scale landsliding in the Cape Verde Islands, off West Africa. Geochemistry, Geophysics, Geosystems 9 (7). Pérez Torrado, F.J., Paris, R., Cabrera, M.C., Schneider, J.L., Wassmer, P., Carracedo, J.C., Rodriguez Santana, A., Santana, F

  12. Geometry of the Cocos Plate Under North American Plate

    NASA Astrophysics Data System (ADS)

    Perez-Campos, X.

    2015-12-01

    The Cocos plate subducts under the North American plate with a complex geometry, and previous seismicity studies revealed some of this complexity. However, details of the geometry and the depth that the plate penetrates werelargely unknown. Since 2004, temporary experiments and the expansion of the permanent network of the Servicio Sismológico Nacional (SSN, Mexican National Seismological Service) have improved resolution of the plate geometry and have helped to map its descent into the upper mantle. Going from northwest to southeast, the Cocos plate appears to be fragmenting into north and south segments. The north segment subducts with an angle of ~30º and the south with an angle of ~10-15º. The transition is smooth near the trench and progresses to a tear at depth; this coincides with the projection of the Orozco Fracture Zone to depth. Also, this transition marks the limit of the presence to the south of an ultra slow velocity layer (USL) on top of the slab.South of this transition, the Cocos plate subducts horizontally , underplating the North American plate for a distance of ~140 to ~300 km from the trench. Along this horizontal region, silent slow events (SSE) and tectonic tremor (TT) have been observed. At a distance of 300 km from the trench (beneath central Mexico), the plate dives into the mantle with an angle of 76º to a depth of 500 km. This geometry changes abruptly to the south, marking the eastern limit of the USL. This change seems to be also characterized by a tear on the slab. Finally to the south, the Cocos plate subducts with a constant angle of 26º. This presentation summarizes the work of many contributors including A. Arciniega-Ceballos, M. Brudzinski, E. Cabral-Cano, T. Chen, R. Clayton,F. Cordoba-Montiel,P. Davis,S. Dougherty,F. Green, M. Gurnis, D. V. Helmberger, A. Husker,A. Iglesias, Y. Kim, V. Manea, D. Melgar, M. Rodríguez-Domínguez,S. K. Singh, T.-R. A. Song, C. M. Valdés-González, D. Valencia-Cabrera

  13. Nanostructured silicon via metal assisted catalyzed etch (MACE): chemistry fundamentals and pattern engineering.

    PubMed

    Toor, Fatima; Miller, Jeffrey B; Davidson, Lauren M; Nichols, Logan; Duan, Wenqi; Jura, Michael P; Yim, Joanne; Forziati, Joanne; Black, Marcie R

    2016-10-14

    There are a range of different methods to generate a nanostructured surface on silicon (Si) but the most cost effective and optically interesting is the metal assisted wet chemical etching (MACE) (Koynov et al 2006 Appl. Phys. Lett. 88 203107). MACE of Si is a controllable, room-temperature wet-chemical technique that uses a thin layer of metal to etch the surface of Si, leaving behind various nano- and micro-scale surface features or 'black silicon'. MACE-fabricated nanowires (NWs) provide improved antireflection and light trapping functionality (Toor et al 2016 Nanoscale 8 15448-66) compared with the traditional 'iso-texturing' (Campbell and Green 1987 J. Appl. Phys. 62 243-9). The resulting lower reflection and improved light trapping can lead to higher short circuit currents in NW solar cells (Toor et al 2011 Appl. Phys. Lett. 99 103501). In addition, NW cells can have higher fill factors and voltages than traditionally processed cells, thus leading to increased solar cell efficiencies (Cabrera et al 2013 IEEE J. Photovolt. 3 102-7). MACE NW processing also has synergy with next generation Si solar cell designs, such as thin epitaxial-Si and passivated emitter rear contact (Toor et al 2016 Nanoscale 8 15448-66). While several companies have begun manufacturing black Si, and many more are researching these techniques, much of the work has not been published in traditional journals and is publicly available only through conference proceedings and patent publications, which makes learning the field challenging. There have been three specialized review articles published recently on certain aspects of MACE or black Si, but do not present a full review that would benefit the industry (Liu et al 2014 Energy Environ. Sci. 7 3223-63; Yusufoglu et al 2015 IEEE J. Photovolt. 5 320-8; Huang et al 2011 Adv. Mater. 23 285-308). In this feature article, we review the chemistry of MACE and explore how changing parameters in the wet etch process effects the resulting texture

  14. Mechanisms of growth and defect properties of epitaxial SiC

    NASA Astrophysics Data System (ADS)

    La Via, F.; Camarda, M.; La Magna, A.

    2014-09-01

    In the last ten years, large improvements in the epitaxial silicon carbide processes have been made. The introduction of chloride precursors, the epitaxial growth on large area substrate with low defect density, the improvement of the surface morphology, the understanding of the chemical vapour deposition (CVD) reactions, and epitaxial mechanisms by advanced simulations are just the main results obtained in the homo-epitaxy process of 4H-SiC. After this large stride in the process of SiC epitaxial growth, it is time to collect this knowledge in a review that can be a reference point for the future work in this interesting field. The structure of the review is the following. After an introduction on the evolution and history of the epitaxial growth of 4H-SiC, the main physics parameter of this epitaxial growth process is explained in detail using the traditional Burton-Cabrera-Franck theory and the experimental observations of the surface instability due to the off-axis growths. Then the introduction of chlorinated precursors in the epitaxial process is reviewed and the effect of this new process on Schottky diodes characteristics is shown. The improvement of the epitaxy process is strictly related to the improvement of the simulation of the growth that helps the researchers to understand the effect of different parameters on such complex system. Then, a large part of the review is devoted to the simulations of the CVD systems, the reaction in the gas phase of the different precursors and the surface reaction models. Also, some important results obtained by Monte Carlo simulation on the study of different growth parameters that influence the formation of defects and their evolution are reported. Finally, the influence of different process parameters and in particular of the growth rate on the formation or the reduction of the principal defects that are observed in the epitaxial layer is reviewed. We have divided these defects in four categories: 3D defects (epi

  15. Physical Mechanisms of Crystal Growth Modification by Biomolecules

    NASA Astrophysics Data System (ADS)

    De Yoreo, James J.

    2010-07-01

    During the process of biomineralization, living organisms use macromolecules to direct the nucleation and growth of a variety of inorganic materials. Because biomineral structures exhibit complex topologies, hierarchical design, and unique materials properties, an understanding of the underlying mechanisms of biomolecular controls over mineral growth presents an opportunity to develop new strategies towards synthesis of novel materials for applications across a wide range of technologies. Herein the results from a combination of in situ atomic force microscopy (AFM) and molecular modeling (MM) studies to investigate the effect of specific interactions between carboxylate-rich biomolecules and atomic steps on calcium carbonate and calcium oxalate crystal surfaces during the growth are reviewed. The results show how the stereochemical relationships between additive and atomic step leads to modifications of crystal shape. In some cases, the inhibitory effects of strong binders are well-explained by a model of growth inhibition based on the classic Cabrera-Vermilyea theory, but updated to take into account the particular nature of biomolecular adsorption dynamics. The consequences include a positive feedback between peptide adsorption and step inhibition that results in bistable growth with rapid switching from fast to near-zero growth rates for very small changes in supersaturation. The phenomenon of biomolecule-induced growth acceleration is also reviewed and shown to be common to both the oxalate and carbonate systems. The source of acceleration is related to the activation barrier for solute attachment to steps. Finally, experimental and theoretical results are presented that suggest most biomineral phases can not be described by conventional models in which kink formation due to thermal fluctuations at step edges is rapid enough to ensure the availability of kinks. Instead, growth is kink-limited. As a consequence, biomolecule-step interactions cannot be

  16. Contrasting Modern and 10Be- derived erosion rates for the Southern Betic Cordillera, Spain

    NASA Astrophysics Data System (ADS)

    Bellin, N.; Vanacker, V.; Kubik, P.

    2012-04-01

    In Europe, Southeast Spain was identified as one of the regions with major treat of desertification in the context of future land use and climate change. During the last years, significant progress has been made to understand spatial patterns of modern erosion rates in these semi-arid degraded environments. Numerous European projects have contributed to the collection of modern erosion data at different spatial scales for Southeast Spain. However, these data are rarely analysed in the context of long-term changes in vegetation, climate and human occupation. In this paper, we present Modern and Holocene denudation rates for small river basins (1 to 10 km2) located in the Spanish Betic Cordillera. Long-term erosion data were derived from cosmogenic nuclide analyses of river-borne sediment. Modern erosion data were quantified through analysis of sediment deposition volumes behind check dams, and represent average erosion rates over the last 10 to 40 years. Modern erosion rates are surprisingly low (mean erosion rate = 0.048 mm y-1; n=36). They indicate that the steep, sparsely vegetated hillslopes in the Betic Cordillera cannot directly be associated with high erosion rates. 10Be -derived erosion rates integrate over the last 37500 to 3500 years, and are roughly of the same magnitude. They range from 0.013 to 0.243 mm y-1 (mean denudation rate = 0.062 mm y-1 ± 0.054; n=20). Our data suggest that the modern erosion rates are similar to the long-term erosion rates in this area. This result is in contrast with the numerous reports on human-accelerated modern erosion rates for Southeast Spain. Interestingly, our new data on long-term erosion rates show a clear spatial pattern, with higher erosion rates in the Sierra Cabrera and lower erosion rates in Sierra de las Estancias, and Sierra Torrecilla. Preliminary geomorphometric analyses suggest that the spatial variation that we observe in long-term erosion rates is related to the gradient in uplift rates of the Betic

  17. Spatial gradient of chemical weathering and its coupling with physical erosion in the soils of the Betic Cordillera (SE Spain)

    NASA Astrophysics Data System (ADS)

    Schoonejans, Jerome; Vanacker, Veerle; Opfergelt, Sophie; Ameijeiras-Mariño, Yolanda; Kubik, Peter

    2015-04-01

    The production and denudation of soil material are controlled by chemical weathering and physical erosion which influence one another. Better understanding and quantification of this relationship is critical to understand biogeochemical cycles in the critical zone. The intense silicate weathering that is taking place in young mountain ranges is often cited to be a negative feedback that involves a long-term reduction of the atmospheric CO2 and the temperature cooling. However the possible (de)coupling between weathering and erosion is not fully understood for the moment and could reduce the effect of the feedback. This study is conducted in the eastern Betic Cordillera located in southeast Spain. The Betic Cordillera is composed by several mountains ranges or so-called Sierras that are oriented E-W to SE-NW and rise to 2000m.a.s.l. The Sierras differ in topographic setting, tectonic activity, and slightly in climate and vegetation. The mountain ranges located in the northwest, such as the Sierra Estancias, have the lowest uplift rates ( ~20-30 mm/kyr); while those in the southeast, such as the Sierra Cabrera, have the highest uplift rates ( >150mm/kyr). The sampling was realised into four small catchments located in three different Sierras. In each of them, two to three soil profiles were excavated on exposed ridgetops, and samples were taken by depth slices. The long-term denudation rate at the sites is inferred from in-situ 10Be CRN measurements. The chemical weathering intensity is constrained using a mass balance approach that is based on the concentration of immobile elements throughout the soil profile (CDF). Our results show that the soil depth decreases with an increase of the denudation rates. Chemical weathering accounts for 5 to 35% of the total mass lost due to denudation. Higher chemical weathering intensities (CDFs) are observed in sites with lower denudation rates (and vice versa). The data suggest that chemical weathering intensities are strongly

  18. Structure of the Palomares margin from preliminary results of the TOPOMED-GASSIS seismic survey (Algero-Balearic basin, Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Giaconia, F.; Guzman Vendrell, M.; Booth-Rea, G.; Ranero, C. R.; Grácia, E.; Lo Iacono, C.

    2012-04-01

    We present two deep seismic reflection lines acquired during the TOPOMED-GASSIS seismic survey across the Palomares margin at the northwestern side of the Algero-Balearic basin. Simultaneously 3.5 kHz multi parametric echo-sounder profiles and bathymetric data were acquired, in order to obtain information of the most recent sedimentary/tectonic records, to relate tectonic structure with seafloor features and find out a possible tectonic control on them. The deep seismic reflection and the 3.5 kHz multi parametric echo-sounder profiles evidence anticlines and synclines affecting the Quaternary sediments. The southeastern limbs of the anticlines are cut by reverse faults suggesting a fault propagation origin for the folds. The recent to present character of these structures is confirmed by the congruence between structural and bathymetric highs and lows. Indeed, the submarine channels that cut across the margin are deflected by the folds flowing parallel to the major synclines, although cutting and incising into one of the anticlines. The folds have a N40-50°E orientation oblique to the Palomares active N20°E sinistral strike-slip fault zone. The data obtained from the TOPOMED-GASSIS seismic survey highlight the presence of contractive structures along the Palomares margin oriented perpendicular to the present NW-SE shortening stress field and according with the present GPS geodetic displacements. This preliminary result depicts a contractive Palomares margin where NW-SE shortening is accommodated by Quaternary NE-SW folds and thrusts. In the coastline and on land the shortening is also accommodated by reverse faults that cut both limbs of the Sierra Cabrera anticline. These faults and folds accommodate the sinistral displacement of the more northerly striking Palomares fault zone. Thus, the Palomares fault zone probably terminates close to the coast line to the south of the Vera basin by merging into these more northeasterly oriented structures. These folds

  19. Si-adatom kinetics in defect mediated growth of multilayer epitaxial graphene films on 6H-SiC

    NASA Astrophysics Data System (ADS)

    Shetu, Shamaita S.; Omar, S. U.; Daniels, K. M.; Daas, B.; Andrews, J.; Ma, S.; Sudarshan, T. S.; Chandrashekhar, M. V. S.

    2013-10-01

    We present a quantitative study on the growth of multilayer epitaxial graphene (EG) by solid-state decomposition of SiC on polar (c-plane Si and C-face) and non-polar (a and m planes) 6H-SiC faces, with distinctly different defect profiles. The growth rates are slower than expected from a mechanism that involves Si loss from an open and free surface, and much faster than expected for the nucleation of a defect-free EG layer, implying that defects in the EG play a critical role in determining the growth kinetics. We show that a Deal-Grove growth model, which assumes vertical diffusion of Si through these defects as the limiting factor for EG growth, is unsuitable for describing multilayer growth. Instead, we introduce a lateral "adatom" diffusion mechanism for Si out-diffusion, based on a modified Burton, Cabrera, and Frank model. In this model, defects in epitaxial graphene serve as sinks for Si desorption loss, taking the place of reactive sites, such as step edges for nucleation and growth of crystals produced with external precursors. This analysis shows that the surface diffusion of Si atoms to the grain boundaries of EG limits the growth on c-plane C-face and non-polar faces, rather than the purely vertical diffusion of Si through the grain boundaries described in the Deal-Grove model. However, for Si-face c-plane growth, diffusion of Si to the defects, as well as desorption of Si at the grain boundaries are both relevant, leading to a different temperature trend compared with the other faces. This distinct qualitative difference is ascribed to point-defects in Si-face growth, as contrasted with line defects/grain boundaries on the other faces. The size of the EG grains correlates with the surface diffusion length extracted from this model. The longer a Si adatom diffuses, the higher the quality of the grown EG film, an insight that provides valuable information on Si adatom kinetics for optimizing EG growth. We discuss the applicability of this model to

  20. Kinetics of gypsum crystal growth from high ionic strength solutions: A case study of Dead Sea - seawater mixtures

    NASA Astrophysics Data System (ADS)

    Reznik, Itay J.; Gavrieli, Ittai; Antler, Gilad; Ganor, Jiwchar

    2011-04-01

    Gypsum precipitation kinetics were examined from a wide range of chemical compositions (11Cabrera and Frank (BCF) crystal growth theory ( Burton et al., 1951) and other layer-by-layer growth mechanisms ( Goto and Ridge, 1967; Van Rosmalen et al., 1981; Bosbach and Rammensee, 1994). Under further-away-from-equilibrium conditions, the reaction is dominated by an apparent 10th order reaction. A conceptual model for gypsum growth kinetics is presented. The model is based on the 2nd order kinetic coefficients determined in the present study and data from the literature and is valid under a wide range of ionic strengths and Ca/SO42- ratios. According to this model, the integration of SO42- to kinks on the surface of the growing crystals is the rate-limiting step in the precipitation reaction. At ionic strengths above 8.5 m the precipitation rate of gypsum is enhanced, possibly due to the formation of CaSO4° ion pairs and/or a decrease in hydration frequencies.

  1. Fundamental studies of solution and gaseous reactions at transition metal surfaces

    NASA Astrophysics Data System (ADS)

    Qiu, Siping

    Redox reactions at metal surfaces have many important applications. For example, they are used to remove contaminants from solution for environmental remediation, and are also used for the growth of dielectric thin films. This dissertation investigates surface chemical reactions at the liquid-solid and vapor-solid interfaces. Chemical reactions at the solid-liquid interface were investigated in an effort to bridge the gap between conventional bulk solution chemical studies and UHV gas phase surface reactions studies. Such reactions have not been studied extensively at the fundamental level due to the inherent complexity of the systems. Saline solutions containing selenate, chromate and uranyl contaminant ions were reacted with Fe and Fe oxide surfaces. Scanning tunneling microscopy (STM) images collected in situ were used to monitor the changes in surface morphology during reaction. X-ray photoelectron spectroscopy (XPS) was used to identify the surface products following reaction. The foil surfaces become smoother due to both etching of the substrate and the deposition of material. Selenium and chromium are deposited onto the surface in a partially reduced form, while uranium is deposited without reduction. The amount of material deposited is dependent on the presence of dissolved gases, such as O2 and CO2, in the solution. Gaseous SeF6 was reacted with atomically clean iron and iron oxide surfaces in vacuum in order to model the reduction of selenate. The resulting surfaces were examined with XPS. It was found that SeF6 dissociatively chemisorbs onto iron, i.e., the selenium is completely reduced. In the reaction with a clean Fe surface, a thin film of FeF2 is formed. Surface oxide inhibits the adsorption of SeF6. The growth of the FeF2 film initially follows MottCabrera kinetics, but then abruptly stops. It is suggested that the shutdown is due to the inability of electrons from the substrate to transport through the film when it becomes too thick. These

  2. Growth from Solutions: Kink dynamics, Stoichiometry, Face Kinetics and stability in turbulent flow

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.; DeYoreo, J. J.; Rashkovich, L. N.; Vekilov, P. G.

    2005-01-01

    1. Kink dynamics. The first segment of a polygomized dislocation spiral step measured by AFM demonstrates up to 60% scattering in the critical length l*- the length when the segment starts to propagate. On orthorhombic lysozyme, this length is shorter than that the observed interkink distance. Step energy from the critical segment length based on the Gibbs-Thomson law (GTL), l* = 20(omega)alpha/(Delta)mu is several times larger than the energy from 2D nucleation rate. Here o is tine building block specific voiume, a is the step riser specific free energy, Delta(mu) is the crystallization driving force. These new data support our earlier assumption that the classical Frenkel, Burton -Cabrera-Frank concept of the abundant kink supply by fluctuations is not applicable for strongly polygonized steps. Step rate measurements on brushite confirms that statement. This is the1D nucleation of kinks that control step propagation. The GTL is valid only if l*

  3. Contribution of wastes and biochar amendment to the sorption capacity of heavy metals by a minesoil

    NASA Astrophysics Data System (ADS)

    Forján, Rubén; Asensio, Verónica; Vega, Flora A.; Andrade, Luisa; Covelo, Emma F.

    2013-04-01

    (A) sorbed element is preferably Pb and Cu is the least sorbed (P <0.05). References Asensio, V.; Vega, F.A.; Singh, B.R.; Covelo, E.F. 2013. Science of the Total Environment. 443:446-453. Pérez-de-Mora, A.; Madrid, F.; Cabrera, F.; Madejón, E. 2007. Geoderma. 139: 1-10 Vega, F.A.; Covelo, E.F.; Andrade, M.L. 2009. J. Hazard. Mater. 169: 36-45. Vega, F.A.; Covelo, E.F.; Andrade, M.L. 2008. J. Colloid. Interface Sci. 327: 275-286.

  4. Food-web structure and trophodynamics of mesopelagic-suprabenthic bathyal macrofauna of the Algerian Basin based on stable isotopes of carbon and nitrogen

    NASA Astrophysics Data System (ADS)

    Fanelli, E.; Cartes, J. E.; Rumolo, P.; Sprovieri, M.

    2009-09-01

    The trophodynamics of mesopelagic (macrozooplankton/micronekton) and benthic boundary layer (suprabenthos=hyperbenthos) faunas from the Algerian Basin were characterized on a seasonal scale through stable carbon and nitrogen isotopic analyses of a total of 34 species and two broad taxa (Copepoda and Cumacea). This is the first study simultaneously focused on trophodynamics of deep-sea zooplankton and suprabenthos. Samples were collected southeast of Mallorca (Algerian Basin, Western Mediterranean), on the continental slope close to Cabrera Archipelago, at 650-780 m depths, ca. bi-monthly between August 2003 and June 2004. Mean δ 13C values of suprabenthos ranged from -21.1‰ ( Munnopsurus atlanticus) to -16.7‰ ( Cyclaspis longicaudata). Values of δ 15N ranged from 2.8‰ ( Lepechinella manco) to 9.9‰ (larvae of Gnathia sp.). The stable isotope ratios of suprabenthic fauna displayed a continuum of values, confirming a wide spectrum of feeding guilds (from filter feeders/surface deposit feeders to predators). According to the available information on diets for suprabenthic species, the highest annual mean δ 15N values were found for the hematophagous isopod Gnathia sp. parasite on fish (represented by Praniza larvae) and carnivorous amphipods (e.g. Rhachotropis spp., Nicippe tumida) consuming copepods, and the lowest δ 15N values were found for two cumaceans ( Cyclaspis longicaudata and Platysympus typicus) feeding on detritus. Assuming a 15N-enrichment factor of 2.5‰ and deposit feeders as baseline, we found three trophic levels in suprabenthic food webs. δ 13C ranges were particularly wide among deposit feeders (ranging from -21.8% to -17.3‰) and omnivores (from -20.5% to -18.8‰), suggesting exploitation of particulate organic matter (POM) of different characteristics. Our isotopic analyses revealed lower ranges of δ 13C and δ 15N for macrozooplankton/micronekton, compared with suprabenthos. δ 13C values of zooplankton taxa ranged from -21.1

  5. The Southern Part of the Southern Volcanic Zone (SSVZ; 42-46S) of the Andes: History of Medium and Large Explosive Holocene Eruptions

    NASA Astrophysics Data System (ADS)

    Stern, C. R.; Naranjo, J. A.

    2008-12-01

    Chaitén volcano is one of 13 large volcanic centers, and numerous small cones, comprising the southern part of the Andean Southern Volcanic Zone (SVZ), that results from the subduction of the Nazca plate (at 7.8 cm/yr) between the landward extension of the Chiloé FZ at 42S and the Chile Rise - Trench triple junction at 46S. Chaitén is a rhyolite dome inside a 3 km diameter caldera located 15 km west of the larger Michinmahuida stratovolcano. Other stratovolcanoes in the SSVZ include Yate, Hornopirén, Corcovado, Yanteles, Melimoyu, Mentolat, Cay and Macá. Hudson volcano, the southernmost in the Southern SVZ, is a large 10 km caldera, while Huequi and Hualaihué - Cordón Cabrera are a group of small aligned cinder cones possibly related to a larger eroded volcanic complex. Prior to the May 2008 eruption of Chaitén, the only well documented historic eruptions in this segment of the Andean arc were the explosive eruption of Hudson in August 1991 (Naranjo et al. 1993), and two eruptions of Michinmahuida in 1742 and 1834-35. Tephra deposits provide evidence of 11 prehistoric explosive Holocene eruptions of the southernmost SSVZ Hudson volcano, including two large eruptions near <6700 and <3600 BP (Naranjo and Stern 1998). The 6700 BP eruption produced greater than 18 km3 of andesitic tephra, possibly the largest Holocene eruption in all the southern Andes. Although Hudson is clearly the most active of the Southern SVZ volcanoes in terms of both volume and frequency of explosive eruptions, tephra deposits indicate that seven of the other SSVZ volcanoes, including Chaitén, also have had medium to large Holocene explosive eruptions (Naranjo and Stern 2004). Three of these eruptions were from Corcovado at approximately <9190, <7980 and <6870 BP, one from Yanteles at <9180 BP, two from Melimoyu at <2740 and <1750 BP, one from Mentolat at <6960 and one from Macá at <1540 BP. Two other eruptions, at <6350 and <3820 BP, we interpret as having been produced by

  6. Changes in the diet and feeding of the hake Merluccius merluccius at the shelf-break of the Balearic Islands: Influence of the mesopelagic-boundary community

    NASA Astrophysics Data System (ADS)

    Cartes, Joan E.; Hidalgo, Manuel; Papiol, Vanesa; Massutí, Enric; Moranta, Joan

    2009-03-01

    Short spatio-temporal variations in the feeding intensity and the diet of the European hake, Merluccius merluccius, together with the abundance of their potential prey were studied between August 2003 and June 2004 at two locations, northwest (Sóller) and south (Cabrera), off the island of Mallorca (Balearic Islands, Western Mediterranean) at depths between 150 and 750 m. The two areas present different oceanographic conditions. Hake was mainly distributed along the shelf-slope break and the upper slope (between 166 and 350 m) where recruits (TL<18 cm) were dominant. The hake's diet varied as a function of size. Recruits fed mainly on micronektonic prey, and the diet was influenced primarily by seasonality, with two dietary patterns (identified by MDS analyses) corresponding to August-September 2003 (summer) and to November 2003/February-April 2004 (autumn-winter). The summer pattern was consistent with a thermally stratified water column, while November and April were consistent with homogenized temperature and salinity throughout all the water column. The main prey of recruits were the euphausiid Meganyctiphanes norvegica and the midwater fish Maurolicus muelleri in autumn-winter and myctophids (mainly Ceratoscopelus maderensis) in summer. In contrast to recruits, the geographic factor (NW vs. S) was the main factor influencing the diets of post-recruits (TL between 18 and 21.9 cm) and adults (TL⩾22 cm). Hake recruits (and to a lesser extent post-recruits) and their preferred prey occupied different depth ranges during daylight periods. Meganyctiphanes norvegica and Ceratoscopelus maderensis were, for instance, distributed as much as 500 m deeper than hake that had eaten them. All these trends were especially obvious at NW, an area with a more abrupt slope and with a greater influence by northern winter intermediate water (WIW) inflow in early spring than the S area. These factors probably enhanced micronekton aggregation in April, when feeding intensity

  7. In-flight gas phase passivation of silicon nanocrystals for novel inorganic-silicon nanocrystal based electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Liptak, Richard William

    fluorocarbon passivation layer, although stable, prevents further functionalization of the NCs. To counteract this problem another silicon-based dry etch chemistry, SF6 was investigated. Full-color emission was observed from SF6 etched NCs, with QY 2X higher than that of CF 4-etched NCs. A maximum QY of nearly 55% at 700 nm was observed after several weeks in air, comparable to that observed with alkyl passivation. The native oxidation of the bare oxidized and SF6-etched NCs were also studied. Results show that the NC oxidation follows the Cabrera-Mott mechanism for low temperature oxidation. Inorganic-NC based LED structures were then investigated. Fabrication processes for the inorganic hole and electron transport layers were developed by RF sputtering and atomic layer deposition (ALD). Thorough characterization was performed on the metal-oxide films (ZnO, TiO2, NiO) to verify their stoichiometry as well as study their optical and electrical properties. Novel inorganic-NC device structures were fabricated. Inorganic NC devices which use a metal-oxide HTL but no ETL, emit light, however their emission is so weak. The addition of an ETL increases the light output by a factor of 4, but the device reproducibility is poor. To improve efficiency two insulating matrix layers were investigated. In both cases, the film deposited on the top of the NC is rough, porous, discontinuous, and potentially full of traps -- certainly not the ideal film for a device. Therefore, more work is needed, specifically on the NC layer to improve the structure of the as-deposited NC film, but efficient device structures appear to be possible.

  8. Late Miocene extensional tectonics in the evolution of the eastern Betics and Neogene-Quaternary basins, an example from the Sorbas basin (SE Spain).

    NASA Astrophysics Data System (ADS)

    Giaconia, Flavio; Booth-Rea, Guillermo; Martínez-Martínez, José Miguel; Azañón, José Miguel

    2013-04-01

    Neogene to Quaternary basins in the eastern Betics occur in synclines among near E/W-elongated antiformal ridges where the metamorphic basement crops out. These antiforms are related to or cut by large-scale strike-slip faults, both developed in response of the NW-SE Africa-Iberia convergence. Most literature associated the origin and evolution of the Neogene-Quaternary eastern Betics basins with this transpressional strike-slip regime. However, recent work showed the great importance of extensional tectonics in the development and evolution of these basins during the middle to late Miocene. In order to define the role of Miocene extensional tectonics in the origin and evolution of Neogene - Quaternary basins, we have carefully mapped a key area in the southeastern Betics, the western termination of Sierra Cabrera. We analyzed the age and linking relationships between brittle fault segments, and finally we constructed a balanced cross section. We identified a NW-SE listric normal fault system that was active during the Tortonian producing southwestward hanging-wall displacement. These normal faults show hard linkage relationships with E-W to N70E vertical strike-slip and oblique-slip extensional transfer faults that show both dextral and sinistral kinematics. The balanced cross section shows that listric faults probably join together into a basal detachment (about 1 km depth) inside the metamorphic basement (Nevado-Filabride complex). The fault system influenced the Tortonian sedimentary evolution of the Sorbas Basin controlling the sediments thickness. The early Tortonian sedimentary unit is missed in the hangingwall of the fault system, meanwhile the thickness of late Tortonian sediments deposited between 11 and 8 Ma change across the main faults from approximately 200 m thick in the footwall of the system to up to 800 m in the main depocentre. Furthermore, the fault system controlled the Tortonian sedimentary facies shifting from continental and deltaic

  9. Improving plot- and regional-scale crop models for simulating impacts of climate variability and extremes

    NASA Astrophysics Data System (ADS)

    Tao, F.; Rötter, R.

    2013-12-01

    better informed decision-making on adaptation strategies. References 1. Coumou, D. & Rahmstorf, S. A decade of extremes. Nature Clim. Change, 2, 491-496 (2012). 2. Rötter, R. P., Carter, T. R., Olesen, J. E. & Porter, J. R. Crop-climate models need an overhaul. Nature Clim. Change, 1, 175-177 (2011). 3. Asseng, S. et al., Uncertainty in simulating wheat yields under climate change. Nature Clim. Change. 10.1038/nclimate1916. (2013). 4. Porter, J.R., & Semenov, M., Crop responses to climatic variation . Trans. R. Soc. B., 360, 2021-2035 (2005). 5. Porter, J.R. & Christensen, S. Deconstructing crop processes and models via identities. Plant, Cell and Environment . doi: 10.1111/pce.12107 (2013). 6. Boogaard, H.L., van Diepen C.A., Rötter R.P., Cabrera J.M. & van Laar H.H. User's guide for the WOFOST 7.1 crop growth simulation model and Control Center 1.5, Alterra, Wageningen, The Netherlands. (1998) 7. Tao, F. & Zhang, Z. Climate change, wheat productivity and water use in the North China Plain: a new super-ensemble-based probabilistic projection. Agric. Forest Meteorol., 170, 146-165. (2013).

  10. NARRATIVE: A short history of my life in science A short history of my life in science

    NASA Astrophysics Data System (ADS)

    Manson, Joseph R.

    2010-08-01

    I earned a modest income playing there as well as in the Norfolk Symphony and several other ensembles. After four years in Richmond and graduating with a degree in physics and mathematics I enrolled as a graduate student in the Physics Department of the University of Virginia. At Virginia I went to work with the well-known Professor Nicholas Cabrera who was then also the department Chair. After a little more than a year, Cabrera took a temporary leave of absence to take a position in Mexico, but this temporary departure later became permanent when he answered a call to return to Spain to establish and lead the Department of Physics at the new Universidad Autonoma de Madrid. Before leaving Virginia, however, Cabrera hired a new Assistant Professor who had already made quite a name for himself, and this was Vittorio Celli. Celli and I immediately hit it off and I continued my studies with him. He is the person to whom I owe the greatest debt as a teacher and mentor who instilled the highest standards of scientific research. We began work on some problems in superconductivity and surface magnetism which I found very interesting, but one day we had a meeting with Professor Sam Fisher of the Department of Aeronautical Engineering at Virginia that totally changed the direction of our research. Sam and his graduate students had carried out a series of experiments on the scattering of high-quality jet beams of helium atoms off of clean, cleaved lithium fluoride surfaces under high-vacuum conditions. Essentially, Sam was repeating experiments originally performed by Otto Stern and coworkers in Frankfurt and Hamburg in the late 1920s, but he had not realized the fact that he was seeing diffraction patterns. We immediately recognized that he was measuring diffraction, and not long thereafter we recognized that his measurements should be sufficiently precise to measure energy transfers due to single quantum excitations of vibrations at the surface. Both Vittorio and I quickly

  11. PREFACE Particles, Strings and Cosmology (PASCOS)

    NASA Astrophysics Data System (ADS)

    Cabrera, Susana; Hirsch, Martin; Mitsou, Vasiliki; Muñoz, Carlos; Pastor, Sergio; Amparo Tórtola, María; Valle, José W. F.; Vives, Óscar

    2010-11-01

    traditionally been aimed mainly at theorists, PASCOS2010 had a stronger emphasis on new results and future experiments. The venue for PASCOS 2010 was the Fundación Universidad Empresa (ADEIT), a modern building, located in the historical city centre of Valencia and very close to the conference hotels and to most historic buildings and monuments. The scientific programme consisted of 26 invited Plenary Talks and 99 contributions, all available online at http://pascos2010.astroparticles.es/. Young researchers were encouraged to submit abstracts, many of which were subsequently selected by the organizing committee for oral presentation in parallel sessions. This year's symposium, attended by over 160 participants from all over the globe, was of particular significance, as it came in the wake of first data from the LHC as well as the Planck satellite. In general, plenary sessions were held in the mornings, with afternoons devoted to parallel sessions focussing on the three areas of particles, strings and cosmology. Official Inauguration and Public Talk The Opening of the Symposium took place in the main Auditorium of ADEIT, starting with a brief welcome address by Professor José W F Valle, Chair of the Organizing Committee, followed by addresses of Professor Pedro Carrasco, Research Vice-Rector of the University of València, Professor José Pío Beltran, representing the President of the CSIC, and Professor Francisco Botella, Director of IFIC. There was also a very successful popular science talk by Professor Carlos Frenk, Director of the Institute for Computational Cosmology at Durham University in the United Kingdom on 'The Structure of the Universe'. This as well as the opening of the PASCOS2010 conference was covered by the local media, and a short summary is also published in the CERN Courier. Valencia, October 2010 The Editors Susana Cabrera, Martin Hirsch,Vasiliki Mitsou, Carlos Mu~oz, Sergio Pastor, María Amparo Tórtola, José W. F. Valle and Óscar Vives The PDF

  12. PREFACE: International Conference on Topics in Astroparticle and Underground Physics (TAUP 2011)

    NASA Astrophysics Data System (ADS)

    Oberauer, Lothar; Raffelt, Georg; Wagner, Robert

    2012-07-01

    The 12th edition of the International Conference on Topics in Astroparticle and Underground Physics (TAUP 2011) was held 5-9 September 2011 in Munich (and for the first time in Germany). It was organized by the Max Planck Institute for Physics (MPP), the Technical University Munich (TUM) and the Cluster of Excellence 'Origin and Structure of the Universe'. The conference was held in the 'Künstlerhaus', a traditional downtown location for artistic festivities. The meeting attracted 317 participants (61 of which were women) from 29 countries, see figure below. The topics covered by the meeting were Cosmology and particle physics, Dark matter and its detection, Neutrino physics and astrophysics, Gravitational waves and High-energy astrophysics and cosmic rays, and the various interfaces between these areas. The scientific sessions consisted of five mornings of plenary talks, four afternoons of parallel sessions, and an evening poster session. The co-founder of the conference series, Alessandro Bottino, has decided to retire from the position of chairman of the TAUP Steering Committee after the completion of TAUP 2011. On behalf of all followers of this series, we thank him for having started these inspiring events and his many years of dedicated service. We thank all speakers, conveners and participants as well as the members of the organizing, steering and international advisory committee for making this a successful and memorable meeting. Lothar Oberauer, Georg Raffelt, Robert Wagner Proceedings editors Figure Committees International Advisory Committee G AntonUniversity of Erlangen E AprileColumbia University M Baldo-CeolinUniversity of Padova R BattistonUniversity of Perugia & INFN L BergströmUniversity Stockholm R BernabeiUniversity of Rome 'Tor Vergata' A BettiniLSC Canfranc P BinetruyAPC Paris J BlümerKarlsruhe Institute of Technology B CabreraStanford University A CaldwellMax Planck Institute for Physics M ChenQueens University E CocciaUniversity of Rome

  13. Control of the geomorphic evolution of an active crater: Popocatpetl (Mexico) 1994-2003.

    NASA Astrophysics Data System (ADS)

    Andrés, N.; Zamorano, J. J.; Palacios, D.; Macias, J. L.; Sanjosé, J. J.

    2009-04-01

    . References.- Cruz-Reyna, S. de la; Meli, R.; Macías, J.L.; Castillo, F.; & Cabrera, B., 1998

  14. PREFACE Particles, Strings and Cosmology (PASCOS)

    NASA Astrophysics Data System (ADS)

    Cabrera, Susana; Hirsch, Martin; Mitsou, Vasiliki; Muñoz, Carlos; Pastor, Sergio; Amparo Tórtola, María; Valle, José W. F.; Vives, Óscar

    2010-11-01

    traditionally been aimed mainly at theorists, PASCOS2010 had a stronger emphasis on new results and future experiments. The venue for PASCOS 2010 was the Fundación Universidad Empresa (ADEIT), a modern building, located in the historical city centre of Valencia and very close to the conference hotels and to most historic buildings and monuments. The scientific programme consisted of 26 invited Plenary Talks and 99 contributions, all available online at http://pascos2010.astroparticles.es/. Young researchers were encouraged to submit abstracts, many of which were subsequently selected by the organizing committee for oral presentation in parallel sessions. This year's symposium, attended by over 160 participants from all over the globe, was of particular significance, as it came in the wake of first data from the LHC as well as the Planck satellite. In general, plenary sessions were held in the mornings, with afternoons devoted to parallel sessions focussing on the three areas of particles, strings and cosmology. Official Inauguration and Public Talk The Opening of the Symposium took place in the main Auditorium of ADEIT, starting with a brief welcome address by Professor José W F Valle, Chair of the Organizing Committee, followed by addresses of Professor Pedro Carrasco, Research Vice-Rector of the University of València, Professor José Pío Beltran, representing the President of the CSIC, and Professor Francisco Botella, Director of IFIC. There was also a very successful popular science talk by Professor Carlos Frenk, Director of the Institute for Computational Cosmology at Durham University in the United Kingdom on 'The Structure of the Universe'. This as well as the opening of the PASCOS2010 conference was covered by the local media, and a short summary is also published in the CERN Courier. Valencia, October 2010 The Editors Susana Cabrera, Martin Hirsch,Vasiliki Mitsou, Carlos Mu~oz, Sergio Pastor, María Amparo Tórtola, José W. F. Valle and Óscar Vives The PDF

  15. Modelling soil organic carbon stocks along topographic transects under climate change scenarios using CarboSOIL

    NASA Astrophysics Data System (ADS)

    Kotb Abd-Elmabod, Sameh; Muñoz-Rojas, Miriam; Jordán, Antonio; Anaya-Romero, María; de la Rosa, Diego

    2014-05-01

    section. On the other hand, lowest SOC stock values have been observed on sections 0-25 and 25-50 cm from Aquic Haploxeralf under wheat, cotton and other annual crops and vineyards, respectively. The lowest SOC values were determined in section 50-75 cm from Typic Ochraqualfs under olive groves. CarboSOIL predicted increases of SOC stocks in future climate scenarios in the upper soil section (0-25 cm) for areas under rotating wheat, cotton and other annual crops. In this case, SOC stocks increases are considerably larger in the areas above 400 masl. In the 25-50 cm soil section, SOC stocks are expected to decrease in the 2040 scenario and then increase in the following 2070 and 2100 scenarios, particularly in olive-cropped areas. Oppositely, SOC stocks from olive-cropped soils will decrease in the 50-75 soil section in the 2070 scenario. Key words: Carbon sequestration, Global change, Land evaluation, MicroLEIS DSS, Topography. References Abd-Elmabod, S.K., Ali, R.R., Anaya-Romero, M., De la Rosa, D. 2010. Evaluating soil contamination risks using MicroLEIS DSS in El-Fayoum province, Egypt. In: 2nd International Conference on Chemical, Biological and Environmental Engineering (ICBEE), 2-4 November, 2010. Cairo. Pp.: 1-5. DOI: 10.1109/ICBEE.2010.5651591. Abd-Elmabod, S.K., Ali, R.R., Anaya-Romero, M., Jordán, A., Muñoz-Rojas, M., Abdelmageed, T.A., Zavala, L.M., De la Rosa, D. 2012. Evaluating soil degradation under different scenarios of agricultural land management in Mediterranean región. Nature and Science 10, 103-116. De la Rosa, D., Mayol, F., Moreno, F., Cabrera, F., Díaz-Pereira, E., Antoine, J. 2002. A multilingual soil profile database (SDBm Plus) as an essential part of land resources information systems. Environmental Modelling & Software 17, 721-730. DOI: 10.1016/S1364-8152(02)00031-2 Muñoz-Rojas, M., De la Rosa, D., Zavala, L.M., Jordán, A., Anaya-Romero, M. 2011. Changes in land cover and vegetation carbon stocks in Andalusia, Southern Spain (1956

  16. Potential soil organic carbon stocks in semi arid areas under climate change scenarios: an application of CarboSOIL model in northern Egypt

    NASA Astrophysics Data System (ADS)

    Muñoz-Rojas, Miriam; Abd-Elmabod, Sameh K.; Jordán, Antonio; Zavala, Lorena M.; Anaya-Romero, Maria; De la Rosa, Diego

    2014-05-01

    crops, and fruit trees and berries). 3. RESULTS AND CONCLUSIONS According to results, considerable decreases of SOC stocks are expected in the 25-50 cm soil section under all considered land use types and all projected scenarios, in particular in Vertic Torrifluvents and Typic Torrifluvents under wheat, cotton and other annual crops. Oppositely, SOC stocks tend to increase in the deeper soil section (50-75 cm), mostly in Typic Haplocalcids under permanently irrigated areas and olive groves in the 2100 scenario. In the upper layer (0-25 cm), slight increases have been predicted under all considered land use types. The methodology used in this research could be applied to other semi arid areas with available soil, land use and climate data. Moreover, the information developed in this study might support decision-making for land use planning, agricultural management and climate adaptation strategies in semi arid regions. REFERENCES Abd-Elmabod, S.K., Ali, R.R., Anaya-Romero, M., Jordán, A., Muñoz-Rojas, M., Abdelmageed, T.A., Zavala, L.M., De la Rosa, D. 2012. Evaluating soil degradation under different scenarios of agricultural land management in Mediterranean region. Nature and Science 10, 103-116. Agrawala, S., A. Moehner, M. El Raey, D. Conway, M. van Aalst, M. Hagenstad and J. Smith. 2004. Development and Climate Change In Egypt: Focus on Coastal Resources and the Nile. Organisation for Economic Co-operation and Development. De la Rosa, D., Mayol, F., Moreno, F., Cabrera, F., Díaz-Pereira, E., Antoine, J. 2002. A multilingual soil profile database (SDBm Plus) as an essential part of land resources information systems. Environmental Modelling & Software 17, 721-730. DOI: 10.1016/S1364-8152(02)00031-2. IPCC. 2007. Climate Change 2007: The Physical Science Basis. Cambridge/New York: Cambridge University Press Jones, C., McConnell, C., Coleman, K., Cox, P., Falloon, P., Jenkinson, D. and Powlson, D. 2005. Global climate change and soil carbon stocks; predictions from

  17. First Temperate Exoplanet Sized Up

    NASA Astrophysics Data System (ADS)

    2010-03-01

    (Hawaii), the Isaac Newton Telescope (Roque de los Muchachos Observatory), Wise Observatory (Israel), the Faulkes North Telescope of the Las Cumbres Observatory Global Telescope Network (Hawaii) and the ESO 3.6-metre telescope (Chile). More information This research was presented in a paper published this week in Nature ("A transiting giant planet with a temperature between 250 K and 430 K"), by H. J. Deeg et al. The team is composed of H.J. Deeg, B. Tingley, J.M. Almenara, and M. Rabus (Instituto de Astrofısica de Canarias, Tenerife, Spain), C. Moutou, P. Barge, A. S. Bonomo, M. Deleuil, J.-C. Gazzano, L. Jorda, and A. Llebaria (Laboratoire d'Astrophysique de Marseille, Université de Provence, CNRS, OAMP, France), A. Erikson, Sz. Csizmadia, J. Cabrera, P. Kabath, H. Rauer (Institute of Planetary Research, German Aerospace Center, Berlin, Germany), H. Bruntt, M. Auvergne, A. Baglin, D. Rouan, and J. Schneider (Observatoire de Paris-Meudon, France), S. Aigrain and F. Pont (University of Exeter, UK), R. Alonso, C. Lovis, M. Mayor, F. Pepe, D. Queloz, and S. Udry (Observatoire de l'Université de Genève, Switzerland), M. Barbieri (Università di Padova, Italia), W. Benz (Universität Bern, Switzerland), P. Bordé, A. Léger, M. Ollivier, and B. Samuel (Institut d'Astrophysique Spatiale, Université Paris XI, Orsay, France), F. Bouchy and G. Hébrard (IAP, Paris, France), L. Carone and M. Pätzold (Rheinisches Institut für Umweltforschung an der Universität zu Köln, Germany), S. Carpano, M. Fridlund, P. Gondoin, and R. den Hartog (ESTEC/ESA, Noordwijk, The Netherlands), D. Ciardi (NASA Exoplanet Science Institute/Caltech, USA), R. Dvorak (University of Vienna, Austria), S. Ferraz-Mello (Universidade de São Paulo, Brasil), D. Gandolfi, E. Guenther, A. Hatzes, G. Wuchterl, B. Stecklum (Thüringer Landessternwarte, Tautenburg, Germany), M. Gillon (University of Liège, Belgium), T. Guillot and M. Havel (Observatoire de la Côte d' Azur, Nice, France), M. Hidas, T. Lister

  18. PREFACE: Atom-surface scattering Atom-surface scattering

    NASA Astrophysics Data System (ADS)

    Miret-Artés, Salvador

    2010-08-01

    It has been a privilege and a real pleasure to organize this special issue or festschrift in the general field of atom-surface scattering (and its interaction) in honor of J R Manson. This is a good opportunity and an ideal place to express our deep gratitude to one of the leaders in this field for his fundamental and outstanding scientific contributions. J R Manson, or Dick to his friends and colleagues, is one of the founding fathers, together with N Cabrera and V Celli, of the 'Theory of surface scattering and detection of surface phonons'. This is the title of the very well-known first theoretical paper by Dick published in Physical Review Letters in 1969. My first meeting with Dick was around twenty years ago in Saclay. J Lapujoulade organized a small group seminar about selective adsorption resonances in metal vicinal surfaces. We discussed this important issue in surface physics and many other things as if we had always known each other. This familiarity and warm welcome struck me from the very beginning. During the coming years, I found this to be a very attractive aspect of his personality. During my stays in Göttingen, we had the opportunity to talk widely about science and life at lunch or dinner time, walking or cycling. During these nice meetings, he showed, with humility, an impressive cultural background. It is quite clear that his personal opinions about history, religion, politics, music, etc, come from considering and analyzing them as 'open dynamical systems'. In particular, with good food and better wine in a restaurant or at home, a happy cheerful soirée is guaranteed with him, or even with only a good beer or espresso, and an interesting conversation arises naturally. He likes to listen before speaking. Probably not many people know his interest in tractors. He has an incredible collection of very old tractors at home. In one of my visits to Clemson, he showed me the collection, explaining to me in great detail, their technical properties

  19. Control of the geomorphic evolution of an active crater: Popocatpetl (Mexico) 1994-2003.

    NASA Astrophysics Data System (ADS)

    Andrés, N.; Zamorano, J. J.; Palacios, D.; Macias, J. L.; Sanjosé, J. J.

    2009-04-01

    . References.- Cruz-Reyna, S. de la; Meli, R.; Macías, J.L.; Castillo, F.; & Cabrera, B., 1998. Cyclical dome extrusions that by late 1997 filled one-third of crater capacity, In Smithsonian-GVP Monthly Reports, Popocatépetl, Smithsonian Institution. Bull. Glob. Volcanism Netw, (GVN) 23 (2), 2 - 4. Donnadieu, F.; Kelfoun, K.; Van Wyk de Vries, B.; Decchi, E.; & Merle, O., 2003. Digital photogrammetry as a tool in analogue modelling: applications to volcano instability, Journal of Volcanology and Geothermal Research, 123 (1-2), 161-180. Macías, J.L. & Siebe, C., 2005. Popocatépetl crater filled to the brim: significance for hazard evaluation, Journal of Volcanology and Geothermal Research (141) 327-330. Martín-Del Pozzo, A.L.; Cifuentes-Nava, G.; Cabral-Cano, E.; Bonifaz, F.; Correa, I.; & Mendiola, I.F., 2003. Timing magma ascent at Popocatepetl Volcano, Mexico, 2000-2001, Journal of Volcanology and Geothermal Research ,125, 107-120. Matiella, M.A.; Watson, I.M.; Delgado, H.; Rose, W.I.; , Cárdenas, L.; & Realmuro, V.J., 2008, Volcanic emissions from Popocatépetl volcano, Mexico, quantified using Moderate Resolution Imaging Spectroradiometer (MODIS) infrared data: A case study of the December 2000-January 2001 emissions, Journal of Volcanology and Geothermal Research, 170, 1-2, 76-85. Procter, J.N.; Platz, T.; & Cronin, S.J., 2006. A remnant summit lava dome and its influence on future eruptive hazards, Geophysical Research Abstracts, Vol. 8, 10211. Schilling, S.P.; Ramsey, D.W.; Messerich, J.A.; & Thompson, R.A., 2006. Map: Rebuilding Mount St. Helens. U.S. Geological Survey Scientific Investigations Map 2928. Tanarro, L. M.; Zamorano, J.J.; & Palacios, D., 2005. Glacier degradation and lahar formation on the Popocatépetl volcano (Mexico) during the last eruptive period (1994-2003), Zeitschrift Geomorphologie (140) 73-92. Zamorano, J.J., Gómez, A. 1996 "Análisis geomorfoloógico a detalle,1:10 000 del cráter del volcán Popocatépetl (1989-1996)" IV Reuni