HLA-DRB1 alleles in four Amerindian populations from Argentina and Paraguay

PubMed Central

2009-01-01

The major histocompatibility complex (MHC) is one of the biological systems of major polymorphisms. The study of HLA class II variability has allowed the identification of several alleles that are characteristic to Amerindian populations, and it is an excellent tool to define the relations and biological affinities among them. In this work, we analyzed the allelic distribution of the HLA-DRB1 class II locus in four Amerindian populations: Mapuche (n = 34) and Tehuelche (n = 23) from the Patagonian region of Argentina, and Wichi SV (n = 24) and Lengua (n = 17) from the Argentinean and Paraguayan Chaco regions, respectively. In all of these groups, relatively high frequencies of Amerindian HLA-DRB1 alleles were observed (DRB1*0403, DRB1*0407, DRB1*0411, DRB1*0417, DRB1*0802, DRB1*0901, DRB1*1402, DRB1*1406 and DRB1*1602). However, we also detected the presence of non-Amerindian variants in Mapuche (35%) and Tehuelche (22%). We compared our data with those obtained in six indigenous groups of the Argentinean Chaco region and in a sample from Buenos Aires City. The genetic distance dendrogram showed a clear-cut division between the Patagonian and Chaco populations, which formed two different clusters. In spite of their linguistic differences, it can be inferred that the biological affinities observed are in concordance with the geographic distributions and interethnic relations established among the groups studied. PMID:21637670

Susceptibility to deltamethrin of wild and domestic populations of Triatoma infestans of the Gran Chaco and the Inter-Andean Valleys of Bolivia.

PubMed

Gomez, Marinely Bustamante; D'Avila, Grasielle Caldas Pessoa; Orellana, Ana Lineth Garcia; Cortez, Mirko Rojas; Rosa, Aline Cristine Luiz; Noireau, François; Diotaiuti, Liléia Gonçalves

2014-11-14

The persistence of Triatoma infestans and the continuous transmission of Trypanosoma cruzi in the Inter-Andean Valleys and in the Gran Chaco of Bolivia are of great significance. Coincidentally, it is in these regions the reach of the vector control strategies is limited, and reports of T. infestans resistance to insecticides, including in wild populations, have been issued. This study aims to characterize the susceptibility to deltamethrin of wild and domestic populations of T. infestans from Bolivia, in order to better understand the extent of this relevant problem. Susceptibility to deltamethrin was assessed in nine, wild and domestic, populations of T. infestans from the Gran Chaco and the Inter-Andean Valleys of Bolivia. Serial dilutions of deltamethrin in acetone (0.2 μL) were topically applied in first instar nymphs (F1, five days old, fasting, weight 1.2 ± 0.2 mg). Dose response results were analyzed with PROBIT version 2, determining the lethal doses, slope and resistance ratios (RR). Qualitative tests were also performed. Three wild T. infestans dark morph samples of Chaco from the Santa Cruz Department were susceptible to deltamethrin with RR50 of <2, and 100% mortality to the diagnostic dose (DD); however, two domestic populations from the same region were less susceptible than the susceptibility reference lineage (RR50 of 4.21 and 5.04 respectively and 93% DD). The domestic population of Villa Montes from the Chaco of the Tarija Department presented high levels of resistance (RR50 of 129.12 and 0% DD). Moreover, the domestic populations from the Valleys of the Cochabamba Department presented resistance (RR50 of 8.49 and 62% DD), the wild populations were less susceptible than SRL and T. infestans dark morph populations (RR50 < 5). The elimination of T. infestans with pyrethroid insecticides in Brazil, Uruguay, Chile, and its drastic reduction in large parts of Paraguay and Argentina, clearly indicates that pyrethroid resistance was very uncommon in non-Andean regions. The pyrethroid susceptibility of non-Andean T. infestans dark morph population, and the resistance towards it, of Andean T. infestans wild and domestic populations, indicates that the Andean populations from Bolivia are less susceptible.

Trypanosoma cruzi diversity in the Gran Chaco: mixed infections and differential host distribution of TcV and TcVI.

PubMed

Monje-Rumi, María M; Brandán, Cecilia Pérez; Ragone, Paula G; Tomasini, Nicolás; Lauthier, Juan J; Alberti D'Amato, Anahí M; Cimino, Rubén O; Orellana, Viviana; Basombrío, Miguel A; Diosque, Patricio

2015-01-01

The transmission cycles of Trypanosoma cruzi in the Gran Chaco are complex networks involving domestic and wild components, whose interrelationships are not well understood. Knowing the circuit of transmission of the different Discrete Typing Units (DTUs) of T. cruzi in the complex environment of the Chaco region is relevant to understanding how the different components (reservoirs, vectors, ecotopes) interact. In the present study we identified the DTUs infecting humans and dogs in two rural areas of the Gran Chaco in Argentina, using molecular methods which avoid parasite culture. Blood samples of humans and dogs were typified by PCR-DNA blotting and hybridization assays with five specific DNA probes (TcI, TcII, TcIII, TcV and TcVI). PCR analyses were performed on seropositive human and dog samples and showed the presence of T. cruzi DNA in 41.7% (98/235) and 53% (35/66) samples, respectively. The identification of infective DTUs was determined in 83.6% (82/98) and 91.4% (32/35) in human and dog samples, respectively. Single infections (36.7% - 36/98) and a previously not detected high proportion of mixed infections (47.9% - 47/98) were found. In a 15.3% (15/98) of samples the infecting DTU was not identified. Among the single infections TcV was the most prevalent DTU (30.6% - 30/98) in human samples; while TcVI (42.8% - 15/35) showed the highest prevalence in dog samples. TcV/TcVI was the most prevalent mixed infection in humans (32.6% - 32/98); and TcI/TcVI (14.3% - 5/35) in dogs. Significant associations between TcV with humans and TcVI with dogs were detected. For the first time, the presence of TcIII was detected in humans from this region. The occurrence of one human infected whit TcIII (a principally wild DTU) could be suggested the emergence of this, in domestic cycles in the Gran Chaco. Copyright © 2014 Elsevier B.V. All rights reserved.

Seroepidemiological trend of strongyloidiasis in the Bolivian Chaco (1987-2013) in the absence of disease-specific control measures.

PubMed

Spinicci, Michele; Macchioni, Fabio; Mantella, Antonia; Gabrielli, Simona; Roselli, Mimmo; Rojo Mayaregua, David; Monasterio Pinckert, Joaquín; Gamboa Barahona, Herlan; Paredes, Grover Adolfo; Halkyer, Percy; Cancrini, Gabriella; Olliaro, Piero; Montresor, Antonio; Bartoloni, Alessandro

2017-11-01

The prevalence of Strongyloides stercoralis infections is grossly underestimated because infections go mostly undetected, although they can persist for a lifetime due to the auto-infective cycle. In the Bolivian Chaco, the prevalence of soil-transmitted nematodes dropped dramatically in the past 25 years, but the mebendazole used for preventive chemotherapy has no effect on S. stercoralis. Meanwhile, the prevalence of intestinal protozoan infections remains unchanged. We compared S. stercoralis seroprevalence in rural communities of the Bolivian Chaco from 1987 to 2013. Sera collected during two previous serosurveys, conducted in the Chaco region in 1987 and 2013, were tested for S. stercoralis using a commercial assay (Bordier-ELISA, Bordier Affinity Products, Switzerland). Overall, 355 sera were analysed, 122 from the 1987 survey and 233 from the 2013 survey. Seropositivity for S. stercoralis was significantly more prevalent in 1987 (19/122, 16% in 1987 vs. 15/233, 6% in 2013, P = 0.006), accounted for by a drop from 17% to 3% in people under 26 years of age. Multivariate analysis showed a significant association between seropositivity for S. stercoralis and age in the 2013 population (OR 1.03 for each one-year increase, 95%CI 1.00-1.05, P = 0.04), but none in 1987. The significant reduction in S. stercoralis seroprevalence in Bolivian Chaco cannot be explained by preventive chemotherapy or improved social-sanitary conditions. As the drop is seen in younger generations, it is consistent with little transmission occurring. However, the risk of transmission still exists, as prevalence is persistently high in older individuals, who present a potential reservoir due to the lifelong nature of S. stercoralis infections. © 2017 John Wiley & Sons Ltd.

Kdr mutations in Triatoma infestans from the Gran Chaco are distributed in two differentiated foci: Implications for pyrethroid resistance management.

PubMed

Sierra, Ivana; Capriotti, Natalia; Fronza, Georgina; Mougabure-Cueto, Gastón; Ons, Sheila

2016-06-01

Point mutations in the voltage-gated sodium channel, the primary target of pyrethroid insecticides, have been associated with the resistance in Triatoma infestans, an important vector of Chagas' disease. Hence, the sustainability of vector control programs requires the implementation of resistance management strategies. We determined the sensitivity of the molecular assays previously designed for early resistance detection to be used in pooled samples from a wide area of the endemic region, and validated them for their routine use in control campaigns for the monitoring of insecticide resistance in T. infestans. Consequently, we used these methods to examine the distribution of resistance-associated mutations in the sodium channel gene in populations of T. infestans from the Argentinean and Bolivian Gran Chaco. The PASA and REA assays tested proved sensitive enough to detect kdr SNPs in pooled samples, indicating these assays are suitable for routine screening in insecticide resistance surveillance. Two geographically differentiated foci were detected in T. infestans populations from the Argentinean and Bolivian Gran Chaco, with populations on the Bolivian-Argentinean border carrying L1014F mutation, and those from the Argentinean Chaco carrying L925I mutation. In all highly resistant populations analyzed, one of both kdr mutations was present, and toxicological assays determined that all pyrethroid resistant populations analyzed herein were sensitive to fenitrothion. The principal cause of pyrethroid resistance in T. infestans from the Gran Chaco ecoregion is kdr mutations in the sodium channel. Different levels of resistance occur in different populations carrying identical mutation, suggesting the existence of contributory mechanisms. Copyright © 2016 Elsevier B.V. All rights reserved.

First Report of Colonies of Sylvatic Triatoma infestans (Hemiptera: Reduviidae) in the Paraguayan Chaco, Using a Trained Dog

PubMed Central

Rolón, Miriam; Vega, María Celeste; Román, Fabiola; Gómez, Ana; Rojas de Arias, Antonieta

2011-01-01

In the Gran Chaco region, control of Triatoma infestans has been limited by persistent domestic infestations despite the efforts of the Vector Control Services. In Paraguay, this region is the highest endemic area in the country, showing high levels of indoor and outdoor infestation. Although sylvatic T. infestans have been found in the Bolivian and Argentine Chaco, similar searches for sylvatic populations of this species in Paraguay had been unsuccessful over the last 20 years. Here we present a new approach to detecting sylvatic Triatominae, using a trained dog, which has successfully confirmed sylvatic populations of T. infestans and other triatomine species in Paraguay. A total of 22 specimens corresponding to dark morph forms of T. infestans were collected, and 14 were confirmed as T. infestans by the mitochondrial cytochrome B gene analysis. Through this analysis, one of which were previously reported and a second that was a new haplotype. Triatomines were captured from amongst vegetation such as dry branches and hollows trees of different species such Aspidosperma quebracho-blanco, Bulnesia sarmientoi and Stetsonia coryne. The colonies found have been small and without apparent infection with Trypanosoma cruzi. During the study, Triatoma sordida and Triatoma guasayana have also been found in ecotopes close to those of T. infestans. PMID:21572522

Considerations on the Species Complex of the Cortelezzii series (Diptera: Psychodidae) and Description of Evandromyia chacuensis sp. nov., a New Phlebotomine Species of the Chaco Region, Argentina.

PubMed

Szelag, Enrique A; Rosa, Juan R; Galati, Eunice A B; Andrade Filho, José D; Salomón, Oscar D

2018-04-06

A new species of phlebotomine sand fly is described and illustrated based on male and female specimens collected in rural and semi-urban areas of the Chaco Province, Argentina. A separation of the Cortelezzii series in two species complexes is proposed, as is a species key for its identification. The morphological characters of the new species permit its inclusion in the Cortelezzii series of genus Evandromyia, subgenus Barrettomyia (Diptera: Psychodidae). The species is named Evandromyia chacuensis sp. nov. Szelag, Rosa, Galati, Andrade Fhilo & Salomón (Diptera: Psychodidae).

"Chiriguano" Astronomy - Venus and a Guarani New Year

NASA Astrophysics Data System (ADS)

Pereira, Gonzalo

A Supreme Decree emitted by the government of Bolivia instituted the celebration of the June solstices in view of the fact that the indigenous people, both the Andean highlands and the Amazon and Chaco, "have commemorated this event for thousands of years" (Gobierno del Estado Plurinacional de Bolivia, Decreto Supremo N° 0173, June16, 2009, La Paz). In the case of the lowlands' indigenous, particularly the Guarani people, the decree mentions the planet Venus as the argument for this celebration. In this case of study and in light of astronomical and ethnographic evidence, we analyze the relevance of this decree in the case of the Guarani people of the Bolivian Chaco region, known as "Chiriguanos".

Land-Use Planning in the Chaco Plain (Burruyacú, Argentina): Part 2: Generating a Consensus Plan to Mitigate Land-Use Conflicts and Minimize Land Degradation

NASA Astrophysics Data System (ADS)

Recatalá Boix, Luis; Zinck, Joseph Alfred

2008-08-01

The Burruyacú district (Tucumán province, Northwest Argentina) has been traditionally an area with rural activities based on the exploitation of the Chaco forest for timber and livestock browsing. Since the 1960s, local institutions started promoting soybean due to favorable land conditions and good market prices. Soybean extension, as from the 1970s, has resulted in important reduction of the Chaco forest and also caused physical soil degradation, especially soil compaction and erosion. A land-use-planning exercise was carried out using the Land-Use Planning and Information System (LUPIS) as a spatial decision support system. LUPIS facilitates the generation of alternative land-use plans by adjusting the relative importance attributed by multiple stakeholders to preference and avoidance policies. The system leads to the allocation of competing land uses to land map units in accordance with their preferred resource requirements, conditional upon the resource base of the area and the stakeholders’ demands. After generating a land use plan for each stakeholder category identified in the study area, including commercial farmers, conservative/conventional farmers, and conservationists, a consensus plan was established to address the land-use conflicts between mechanized agriculture, traditional agriculture and forest conservation, and to mitigate soil degradation caused by extensive dry-farming. Although the planning exercise did not directly involve the stakeholders, the results are sufficiently practical and realistic to suggest that the approach could be extended to the entire Chaco plain region.

Experimental Evidence of Biological Interactions among Different Isolates of Trypanosoma cruzi from the Chaco Region

PubMed Central

Ragone, Paula G.; Pérez Brandán, Cecilia; Monje Rumi, Mercedes; Tomasini, Nicolás; Lauthier, Juan J.; Cimino, Rubén O.; Uncos, Alejandro; Ramos, Federico; Alberti D´Amato, Anahí M.; Basombrío, Miguel A.; Diosque, Patricio

2015-01-01

Many infectious diseases arise from co-infections or re-infections with more than one genotype of the same pathogen. These mixed infections could alter host fitness, the severity of symptoms, success in pathogen transmission and the epidemiology of the disease. Trypanosoma cruzi, the etiological agent of Chagas disease, exhibits a high biological variability often correlated with its genetic diversity. Here, we developed an experimental approach in order to evaluate biological interaction between three T. cruzi isolates belonging to different Discrete Typing Units (DTUs TcIII, TcV and TcVI). These isolates were obtained from a restricted geographical area in the Chaco Region. Different mixed infections involving combinations of two isolates (TcIII + TcV, TcIII + TcVI and TcV + TcVI) were studied in a mouse model. The parameters evaluated were number of parasites circulating in peripheral blood, histopathology and genetic characterization of each DTU in different tissues by DNA hybridization probes. We found a predominance of TcVI isolate in blood and tissues respect to TcIII and TcV; and a decrease of the inflammatory response in heart when the damage of mice infected with TcVI and TcIII + TcVI mixture were compared. In addition, simultaneous presence of two isolates in the same tissue was not detected. Our results show that biological interactions between isolates with different biological behaviors lead to changes in their biological properties. The occurrence of interactions among different genotypes of T. cruzi observed in our mouse model suggests that these phenomena could also occur in natural cycles in the Chaco Region. PMID:25789617

Soil analysis in discussions of agricultural feasibility for ancient civilizations: A critical review and reanalysis of the data and debate from Chaco Canyon, New Mexico.

PubMed

McCool, Jon-Paul P; Fladd, Samantha G; Scarborough, Vernon L; Plog, Stephen; Dunning, Nicholas P; Owen, Lewis A; Watson, Adam S; Bishop, Katelyn J; Crowley, Brooke E; Haussner, Elizabeth A; Tankersley, Kenneth B; Lentz, David; Carr, Christopher; Thress, Jessica L

2018-01-01

Questions about how archaeological populations obtained basic food supplies are often difficult to answer. The application of specialist techniques from non-archaeological fields typically expands our knowledge base, but can be detrimental to cultural interpretations if employed incorrectly, resulting in problematic datasets and erroneous conclusions not easily caught by the recipient archaeological community. One area where this problem has failed to find resolution is Chaco Canyon, New Mexico, the center of one of the New World's most vibrant ancient civilizations. Discussions of agricultural feasibility and its impact on local population levels at Chaco Canyon have been heavily influenced by studies of soil salinity. A number of researchers have argued that salinized soils severely limited local agricultural production, instead suggesting food was imported from distant sources, specifically the Chuska Mountains. A careful reassessment of existing salinity data as measured by electrical conductivity reveals critical errors in data conversion and presentation that have misrepresented the character of the area's soil and its potential impact on crops. We combine all available electrical conductivity data, including our own, and apply multiple established conversion methods in order to estimate soil salinity values and evaluate their relationship to agricultural productivity potential. Our results show that Chacoan soils display the same salinity ranges and spatial variability as soils in other documented, productive fields in semi-arid areas. Additionally, the proposed large-scale importation of food from the Chuska Mountains region has serious social implications that have not been thoroughly explored. We consider these factors and conclude that the high cost and extreme inflexibility of such a system, in combination with material evidence for local agriculture within Chaco Canyon, make this scenario highly unlikely. Both the soil salinity and archaeological data suggest that there is no justification for precluding the practice of local agriculture within Chaco Canyon.

Chaco Chachalaca (Ortalis canicollis, Wagler, 1830) feeding ecology in a gallery forest in the South Pantanal (Brazil).

PubMed

Ragusa-Netto, J

2015-01-01

Cracids are generalist frugivores, which often exploit plant food resources such as flowers and leaves, mainly when fruit production declines. The Chaco chachalaca (Ortalis canicollis) is the most abundant cracid in the Pantanal (Brazil), and particularly common in the gallery forests. However, the factors related to their occurrence in this habitat type are unclear. In this study I describe the feeding habits and feeding niche breadth fluctuations of the Chaco chachalaca in relation to food resources abundance and diversity at the Miranda river gallery forest (Southern Pantanal). I also analyzed the relationships between Chaco chachalacas feeding activity and food resources abundance. This parameter (flowers and fruits) exhibited significant seasonal differences of abundance in which flowers were plentiful at the end of the dry, while fruits were abundant during the early wet season. However, food resources diversity to Chaco chachalacas exhibited no seasonal difference. Their feeding activity paralleled the availability of food resources, so that when some items were massively available an enhanced number of Chaco chachalacas foraged in the gallery forest, particularly during the prolonged dry season when they extensively used flowers and Genipa americana fruits. In fact, the Chaco chachalaca feeding niche breadth value presented low values in this period, while high values were common in the rest of the year. The flexible diet of this cracid, potentially favors their year round presence in the gallery forest, mainly during the prolonged dry season when the propensity for famine might be high. Since the Chaco chachalaca is among the largest and most abundant canopy frugivores in the gallery forest, it may contribute to forest regeneration, an underscored role due to the impact of annual floods and meandering dynamics on tree loss.

Rainwater harvesting in the South American Dry Chaco

NASA Astrophysics Data System (ADS)

Magliano, P. N.; Baldi, G.; Murray, F.; Aurand, S.; Paez, R. A.; Jobbagy, E. G.

2014-12-01

A vast fraction of the South American Dry Chaco ecoregion still relies on rainwater harvesting (RWH) to support, not only livestock production, but domestic and industrial uses as well. As a result, water capture and storage infrastructure is widely disseminated throughout the region. In this work we characterized the most typical RWH systems in two contrastingly developed sub-regions of Dry Chaco ranging from extensive ranching to intensive beef and dairy production (central Argentina and western Paraguay, respectively). In each sub-region, we quantified RWH density, spatial distribution and associations with landscape features; by other hand, we illustrated how the daily dynamic of water stock in a typical RWH system contributes to assess their capture and storage efficiency. We found that randomly distributed, low-tech RWH systems prevail in central Argentina, while clustered and hi-tech systems do it in western Paraguay. Their density was highly contrasting between sub-regions (0.098 vs. 0.94 units/ km2 in central Argentina and western Paraguay, respectively), being exponentially associated with land cleared fraction and proximity to villages. The daily monitoring of water level suggested a positive but complex response of water capture to precipitation. The elongated catchment area, created by roads and trails, could have partially decoupled local precipitation and water yield of the impoundment, favouring the capture of remote precipitation events and generating highly variable water yield under large local precipitation events. Once stored, the rates of water level decline suggested that infiltration exceeded evaporation as a water output pathway (59 vs. 41%, respectively, of total losses). Across both study areas, RWH accounts for less than 1% of the annual precipitation, playing a minor role on the regional water balance; however at a local level, they can affect several hydrological fluxes including the onset of groundwater recharge and the mitigation of extreme runoff events along roads and trails.

What happened in the South American Gran Chaco? Diversification of the endemic frog genus Lepidobatrachus Budgett, 1899 (Anura: Ceratophryidae).

PubMed

Brusquetti, Francisco; Netto, Flavia; Baldo, Diego; Haddad, Célio F B

2018-06-01

The Chaco is one the most neglected and least studied regions of the world. This highly-seasonal semiarid biome is an extensive continuous plain without any geographic barrier, and in spite of its high species diversity, the events and processes responsible have never been assessed. Miocene marine introgressions and Pleistocene glaciations have been mentioned as putative drivers of diversification for some groups of vertebrates in adjacent biomes of southern South America. Here we used multilocus data (one mitochondrial and six nuclear loci) from the three species of the endemic frog genus Lepidobatrachus (Lepidobatrachus asper, Lepidobatrachus laevis, and Lepidobatrachus llanensis) to determine if any of the historical events suggested as drivers of vertebrate diversification in southern South America are related to the diversification of the genus and if the Chaco is indeed a biome without barriers. Using fossil calibration in a coalescent framework we estimated that the genus diversified in the second half of the Miocene, coinciding with marine introgressions. Genetic patterns and historical demography suggest an important role of old archs and cratons as refuges during floods. In one species of the genus, L. llanensis, genetic structure reveals some breaks along the landscape, the main one of which corresponds to an area of the central Chaco that may act as a climatic barrier. Additionally, we found differential effects of the main Chacoan rivers on species of Lepidobatrachus that could be related to the time of persistence of populations in the areas influenced by these rivers. Copyright © 2018 Elsevier Inc. All rights reserved.

A Microsatellite-Based Analysis of House Infestation With Triatoma Infestans (Hemiptera: Reduviidae) After Insecticide Spraying in the Argentine Chaco.

PubMed

Piccinali, Romina V; Gaunt, Michael W; Gürtler, Ricardo E

2018-05-04

Prevention of vector-borne transmission of Chagas disease mainly relies on residual insecticide spraying. Despite significant success at a regional scale, house infestation with Triatoma infestans (Klug) (Hemiptera: Reduviidae) still persists in the Gran Chaco ecoregion. One key aspect is the identification of the sources of reinfestant triatomines. After detecting fine-scale genetic structure in two rural villages of Pampa del Indio, Argentine Chaco, we tested hypotheses on the putative origins of the triatomines collected at 4, 8, and 12 mo after insecticide house spraying. We genotyped 10 microsatellite loci in 262 baseline and 83 postspraying triatomines from different houses. Genetic variability was similar between baseline and postspraying populations, but 13 low-frequency alleles were not detected at postspraying. FSTs were not significant between insects collected before and after insecticide spraying at the same house in all but one case, and they clustered together in a neighbor-joining tree. A clustering algorithm detected seven genetic groups, four of them mainly composed of baseline and postspraying insects from the same house. Assignment tests suggested multiple putative sources (including the house of collection) for most postspraying insects but excluded a house located more than 9 km from the study area. The origin of three triatomines was attributed to immigration from other unaccounted sources. Our study is compatible with the hypothesis that house reinfestations in the Argentine Chaco are mostly related to residual foci (i.e., survival of insects within the same community), in agreement with field observations, spatial analysis, and morphometric studies previously published.

Twentieth century arroyo changes in Chaco Culture National Historical Park

USGS Publications Warehouse

Gellis, Allen C.

2002-01-01

Chaco Wash arroyo channel changes in the 20th century have become a major concern of the National Park Service. Several archeologic and cultural sites are located in the Chaco Wash corridor; thus, increased erosional activity of Chaco Wash, such as channel incision and increased meandering, may affect these sites. Through field surveys, photogrammetric analyses, and reviews of existing reports and maps, arroyo changes at Chaco Culture National Historic Park were documented. Arroyo changes were documented for the inner active channel and the entire arroyo cross section. The inner channel of Chaco Wash evolved from a wide, braided channel in the 1930's to a narrower channel with a well-developed flood plain by the 1970's. From 1934 to 1973 the active channel narrowed an average of 26 meters, and from the 1970's to 2000 the channel narrowed an average of 9 meters. Overall from 1934 to 2000, the inner channel narrowed an average of 30 meters. From 1934 to 2000, the top of Chaco Wash widened at four cross sections, narrowed at one, and remained the same at another. The top of Chaco Wash widened at a rate of 0.4 meter per year from the 1970's to 2000 compared with 0.2 meter per year from 1934 to 1973. At 50-percent depth or halfway down the arroyo channel, four cross sections widened and two cross sections narrowed from 1934 to 2000. Rates of widening at 50-percent depth decreased from 0.2 meter per year from 1934 to 1973 to 0.1 meter per year from the 1970's to 2000. From 1934 to 2000, arroyo depth decreased at five of six cross sections and increased at one cross section. Arroyo depth between 1934 and 1973 decreased an average 1.4 meters from aggradation and between the 1970's and 2000 increased an average 0.4 meter from channel scour. From 1934 to 2000, arroyo cross-sectional area decreased at all six cross sections. Cross-sectional areas in Chaco Wash decreased from 1934 to 1973 as a result of sediment deposition and both decreased and increased from the 1970's to 2000. The cross-sectional area decreased by the 1970's due to channel narrowing and flood-plain formation. Increases in cross-sectional area are from channel scour and channel widening. Photogrammetric analyses of volumetric changes for a 1.7-kilometer reach of Chaco Wash showed sediment deposition from 1934 to 1973 of 64 square meters per unit length of channel over 1.7 kilometers to erosion from 1973 to 2000 of 7 square meters per unit length of channel. Chaco Wash evolved from a braided channel in the 1930's to a narrow, sinuous inner channel by the 1970's. Chaco Wash was widening in the 1930's, leading to sediment deposition and formation of an inner flood plain. Channel narrowing resulted from increased sediment deposition on the flood plain. Sediment deposition may be related to a decrease in peak flows, an increase in flood-plain vegetation, or an increase in the transport of fine-grained sediment. Increases in bankfull depth of Chaco Wash between the 1970's and 2000 were due to aggradation of the flood plain and channel scour. Thus, rates of aggradation and cross-sectional filling were greater from 1934 to the 1970's than from the 1970's to 2000.

Agriculture on the Chaco Plain, Paraguay, South America

NASA Technical Reports Server (NTRS)

1990-01-01

This view of extensive agriculture on the Chaco Plain, Paraguay, (22.5S, 60.5W) depicts the fertility of the soils between the Andes Mountains and the Paraguay - Parana Rivers in the northwestern Paraguay. The Gran Chaco Plain is flat landscape built up by sediments. Frontier settlements like Marsical Estigarribia, seen in the image, are dominated by agriculture along the stream courses that abound in the area.

The ticks (Acari: Ixodida: Argasidae, Ixodidae) of Paraguay

DTIC Science & Technology

2007-01-01

comprises the Amazonic and Chaco domains. The Amazonic domain is represented by the Cerrado phyto–geographical province (CePP) in the north–east and by the...geographical provinces of Cerrado and Paranaense belong to the Amazonic domain whereas Chaco province is within the Chaco domain. 258 NAVA ET AL. RESULTS...Ecuador, Panama, Peru and Venezuela. Ornithodoros talaje (Guérin-Méneville)/ Ornithodoros puertoricensis Fox. Cordero et al. (1928) found adults of Orn

Chaco astronomies

NASA Astrophysics Data System (ADS)

Martín López, Alejandro

2015-08-01

This presentation discusses the result of 18 years of ethnographic and ethnohistorical studies on Chaco astronomies. The main features of the systems of astronomical knowledge of the Chaco Aboriginal groups will be discussed. In particular we will discuss the relevance of the Milky Way, the role of the visibility of the Pleiades, the ways in which the celestial space is represented, the constitution of astronomical orientations in geographic space, etc. We also address a key feature of their vision of the cosmos: the universe is seen by these groups as a socio-cosmos, where humans and non-humans are related. These are therefore actually socio-cosmologies. We will link this to the theories of Chaco Aboriginal groups about power and political relations.We will discuss how the study of Aboriginal astronomies must be performed along with the studies about astronomies of Creole people and European migrants, as well as anthropological studies about the science teaching in the formal education system and by the mass media. In this form we will discuss the relevance of a very complex system of interethnic relations for the conformation of these astronomical representations and practices.We will also discuss the general methodological implications of this case for the ethnoastronomy studies. In particular we will talk about the advantages of a study of regional scope and about the key importance of put in contact the ethnoastronomy with contemporary issues in social sciences.We also analyze the importance of ethnoastronomy studies in relation to studies of sociology of science, especially astronomy. We also study the potential impact on improving formal and informal science curricula and in shaping effective policies to protect the tangible and intangible astronomical heritage in a context of respect for the rights of Aboriginal groups.

Genetic variability, phylogenetic relationships and gene flow in Triatoma infestans dark morphs from the Argentinean Chaco

PubMed Central

Piccinali, R. V.; Marcet, P. L.; Ceballos, L. A.; Kitron, U.; Gürtler, R. E.; Dotson, E. M.

2011-01-01

The recent discovery of sylvatic populations of Triatoma infestans outside the Andean Valleys of Bolivia prompted an evolutionary question about the putative ancestral area of origin and dispersal of the species, and an epidemiological question regarding the possible role of these sylvatic populations in the recolonization process of insecticide-treated houses. The finding of a population of sylvatic melanic T. infestans (dark morphs) in the Argentinean dry Chaco at 7 km from a peridomestic bug population of typical coloration gave us the opportunity to test both questions simultaneously by employing phylogenetic and population genetic approaches. For this purpose we analyzed sylvatic and peridomestic bugs using sequence-based mitochondrial and nuclear markers (mtCOI and ITS-1) and microsatellites. Sylvatic bugs were confirmed to be T. infestans and not hybrids, and showed high levels of genetic variability and departures from neutral expectations for mtCOI variation. New ITS-1 and mtCOI haplotypes were recorded, as well as haplotypes shared with peridomestic and/or domestic bugs from previous records. The peridomestic population was invariant for ITS-1 and mtCOI, but showed variability for microsatellites and signatures of a population bottleneck, probably due to a limited number of founders. Phylogenetic analyses were consistent with the presence of ancestral haplotypes in sylvatic bugs. According to F-statistics and assignment methods there was a significant differentiation between sylvatic and peridomestic bugs and gene flow was low and asymmetric, with more bugs moving from the peridomicile to the sylvatic environment. These results support the hypothesis of the Chaco region as the area of origin of T. infestans, and a limited role of sylvatic melanic T. infestans in peridomestic infestation in the Argentinean Chaco. PMID:21352954

The sylvatic transmission cycle of Trypanosoma cruzi in a rural area in the humid Chaco of Argentina.

PubMed

Alvarado-Otegui, J A; Ceballos, L A; Orozco, M M; Enriquez, G F; Cardinal, M V; Cura, C; Schijman, A G; Kitron, U; Gürtler, R E

2012-10-01

Little is known about the sylvatic transmission cycle of Trypanosoma cruzi in the Gran Chaco ecoregion. We conducted surveys to identify the main sylvatic hosts of T. cruzi, parasite discrete typing units and vector species involved in Pampa del Indio, a rural area in the humid Argentinean Chaco. A total of 44 mammals from 14 species were captured and examined for infection by xenodiagnosis and polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNA-PCR). Ten (22.7%) mammals were positive by xenodiagnosis or kDNA-PCR. Four of 11 (36%) Didelphis albiventris (white-eared opossums) and six of nine (67%) Dasypus novemcinctus (nine-banded armadillos) were positive by xenodiagnosis and or kDNA-PCR. Rodents, other armadillo species, felids, crab-eating raccoons, hares and rabbits were not infected. Positive animals were highly infectious to the bugs that fed upon them as determined by xenodiagnosis. All positive opossums were infected with T. cruzi I and all positive nine-banded armadillos with T. cruzi III. Extensive searches in sylvatic habitats using 718 Noireau trap-nights only yielded Triatoma sordida whereas no bug was collected in 26 light-trap nights. Four armadillos or opossums fitted with a spool-and-line device were successfully tracked to their refuges; only one Panstrongylus geniculatus was found in an armadillo burrow. No sylvatic triatomine was infected with T. cruzi by microscopical examination or kDNA-PCR. Our results indicate that two independent sylvatic transmission cycles of T. cruzi occur in the humid Chaco. The putative vectors of both cycles need to be identified conclusively. Copyright © 2012 Elsevier B.V. All rights reserved.

The sylvatic transmission cycle of Trypanosoma cruzi in a rural area in the humid Chaco of Argentina

PubMed Central

Alvarado-Otegui, J.A.; Ceballos, L.A.; Orozco, M.M.; Enriquez, G.F.; Cardinal, M.V.; Cura, C.; Schijman, A.G.; Kitron, U.; Gürtler, R.E.

2012-01-01

Little is known about the sylvatic transmission cycle of Trypanosoma cruzi in the Gran Chaco ecoregion. We conducted surveys to identify the main sylvatic hosts of T. cruzi, parasite discrete typing units and vector species involved in Pampa del Indio, a rural area in the humid Argentinean Chaco. A total of 44 mammals from 14 species was captured and examined for infection by xenodiagnosis and polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNA-PCR). Ten (22.7%) mammals were positive by xenodiagnosis or kDNA-PCR. Four of 11 (36%) Didelphis albiventris (white-eared opossums) and six of nine (67%) Dasypus novemcinctus (nine-banded armadillos) were positive by xenodiagnosis and or kDNA-PCR. Rodents, other armadillo species, felids, crab-eating raccoons, hares and rabbits were not infected. Positive animals were highly infectious to the bugs that fed upon them as determined by xenodiagnosis. All positive opossums were infected with T. cruzi I and all positive nine-banded armadillos with T. cruzi III. Extensive searches in sylvatic habitats using 718 Noireau trap-nights only yielded Triatoma sordida whereas no bug was collected in 26 light-trap nights. Four armadillos or opossums fitted with a spool-and-line device were successfully tracked to their refuges; only one Panstrongylus geniculatus was found in an armadillo burrow. No sylvatic triatomine was infected with T. cruzi by microscopical examination or kDNA-PCR. Our results indicate that two independent sylvatic transmission cycles of T. cruzi occur in the humid Chaco. The putative vectors of both cycles need to be identified conclusively. PMID:22771688

mtDNA diversity in Azara's owl monkeys (Aotus azarai azarai) of the Argentinean Chaco.

PubMed

Babb, Paul L; Fernandez-Duque, Eduardo; Baiduc, Caitlin A; Gagneux, Pascal; Evans, Sian; Schurr, Theodore G

2011-10-01

Owl monkeys (Aotus spp.) inhabit much of South America yet represent an enigmatic evolutionary branch among primates. While morphological, cytogenetic, and immunological evidence suggest that owl monkey populations have undergone isolation and diversification since their emergence in the New World, problems with adjacent species ranges, and sample provenance have complicated efforts to characterize genetic variation within the genus. As a result, the phylogeographic history of owl monkey species and subspecies remains unclear, and the extent of genetic diversity at the population level is unknown. To explore these issues, we analyzed mitochondrial DNA (mt DNA) variation in a population of wild Azara's owl monkeys (Aotus azarai azarai) living in the Gran Chaco region of Argentina. We sequenced the complete mitochondrial genome from one individual (16,585 base pairs (bp)) and analyzed 1,099 bp of the hypervariable control region (CR) and 696 bp of the cytochrome oxidase II (COII) gene in 117 others. In addition, we sequenced the mitochondrial genome (16,472 bp) of one Nancy Ma's owl monkey (A. nancymaae). Based on the whole mtDNA and COII data, we observed an ancient phylogeographic discontinuity among Aotus species living north, south, and west of the Amazon River that began more than eight million years ago. Our population analyses identified three major CR lineages and detected a high level of haplotypic diversity within A. a. azarai. These data point to a recent expansion of Azara's owl monkeys into the Argentinean Chaco. Overall, we provide a detailed view of owl monkey mtDNA variation at genus, species, and population levels. Copyright © 2011 Wiley-Liss, Inc.

Strontium isotopes reveal distant sources of architectural timber in Chaco Canyon, New Mexico

USGS Publications Warehouse

English, N.B.; Betancourt, J.L.; Dean, J.S.; Quade, Jay

2001-01-01

Between A.D. 900 and 1150, more than 200,000 conifer trees were used to build the prehistoric great houses of Chaco Canyon, New Mexico, in what is now a treeless landscape. More than one-fifth of these timbers were spruce (Picea) or fir (Abies) that were hand-carried from isolated mountaintops 75-100 km away. Because strontium from local dust, water, and underlying bedrock is incorporated by trees, specific logging sites can be identified by comparing 87Sr/86Sr ratios in construction beams from different ruins and building periods to ratios in living trees from the surrounding mountains. 87Sr/86Sr ratios show that the beams came from both the Chuska and San Mateo (Mount Taylor) mountains, but not from the San Pedro Mountains, which are equally close. Incorporation of logs from two sources in the same room, great house, and year suggest stockpiling and intercommunity collaboration at Chaco Canyon. The use of trees from both the Chuska and San Mateo mountains, but not from the San Pedro Mountains, as early as A.D. 974 suggests that selection of timber sources was driven more by regional socioeconomic ties than by a simple model of resource depletion with distance and time.

Strontium isotopes reveal distant sources of architectural timber in Chaco Canyon, New Mexico.

PubMed

English, N B; Betancourt, J L; Dean, J S; Quade, J

2001-10-09

Between A.D. 900 and 1150, more than 200,000 conifer trees were used to build the prehistoric great houses of Chaco Canyon, New Mexico, in what is now a treeless landscape. More than one-fifth of these timbers were spruce (Picea) or fir (Abies) that were hand-carried from isolated mountaintops 75-100 km away. Because strontium from local dust, water, and underlying bedrock is incorporated by trees, specific logging sites can be identified by comparing (87)Sr/(86)Sr ratios in construction beams from different ruins and building periods to ratios in living trees from the surrounding mountains. (87)Sr/(86)Sr ratios show that the beams came from both the Chuska and San Mateo (Mount Taylor) mountains, but not from the San Pedro Mountains, which are equally close. Incorporation of logs from two sources in the same room, great house, and year suggest stockpiling and intercommunity collaboration at Chaco Canyon. The use of trees from both the Chuska and San Mateo mountains, but not from the San Pedro Mountains, as early as A.D. 974 suggests that selection of timber sources was driven more by regional socioeconomic ties than by a simple model of resource depletion with distance and time.

The niche and phylogeography of a passerine reveal the history of biological diversification between the Andean and the Atlantic forests.

PubMed

Trujillo-Arias, Natalia; Dantas, Gisele P M; Arbeláez-Cortés, Enrique; Naoki, Kazuya; Gómez, Maria I; Santos, Fabricio R; Miyaki, Cristina Y; Aleixo, Alexandre; Tubaro, Pablo L; Cabanne, Gustavo S

2017-07-01

The Atlantic Forest is separated from the Andean tropical forest by dry and open vegetation biomes (Chaco and Cerrado). Despite this isolation, both rainforests share closely related lineages, which suggest a past connection. This connection could have been important for forest taxa evolution. In this study, we used the Saffron-billed Sparrow (Arremon flavirostris) as a model to evaluate whether the Andean and the Atlantic forests act as a refugia system, as well as to test for a history of biogeographic connection between them. In addition, we evaluated the molecular systematic of intraspecific lineages of the studied species. We modeled the current and past distribution of A. flavirostris, performed phylogeographic analyses based on mitochondrial and nuclear genes, and used Approximate Bayesian Computation (ABC) analyses to test for biogeographic scenarios. The major phylogeographic disjunction within A. flavirostris was found between the Andean and the Atlantic forests, with a divergence that occurred during the Mid-Pleistocene. Our paleodistribution models indicated a connection between these forest domains in different periods and through both the Chaco and Cerrado. Additionally, the phylogeographic and ABC analyses supported that the Cerrado was the main route of connection between these rainforests, but without giving decisive evidence against a Chaco connection. Our study with A. flavirostris suggest that the biodiversity of the Andean and of the Atlantic forests could have been impacted (and perhaps enriched?) by cycles of connections through the Cerrado and Chaco. This recurrent cycle of connection between the Andean and the Atlantic Forest could have been important for the evolution of Neotropical forest taxa. In addition, we discussed taxonomic implications of the results and proposed to split the studied taxon into two full species. Copyright © 2017 Elsevier Inc. All rights reserved.

Two new species of Chaco Tullgren from the Atlantic coast of Uruguay (Araneae, Mygalomorphae, Nemesiidae).

PubMed

de Oca, Laura Montes; Pérez-Miles, Fernando

2013-01-01

We describe two new species of the nemesiid spider genus Chaco from Rocha Province, Uruguay. These new species are diagnosed based on genital morphology, male tibial apophysis spination, and burrow entrance. We test cospecificity of one species, Chaco costai,via laboratory mating experiments. The new species are diagnosed and illustrated and habitat characteristics, and capture behavior are described. We conduct a cladistic analysis based on a previously published morphological character matrix that now includes the newly described species.

Environment or beekeeping management: What explains better the prevalence of honey bee colonies with high levels of Varroa destructor?

PubMed

Giacobino, Agostina; Pacini, Adriana; Molineri, Ana; Bulacio Cagnolo, N; Merke, J; Orellano, E; Bertozzi, E; Masciangelo, G; Pietronave, H; Signorini, M

2017-06-01

Varroa destructor is one of the major threats to honey bee colonies. The mite abundance in the colonies is affected by environmental conditions as well as by beekeeping management. The aim of this study was to recognize the main drivers associated with autumn V. destructor infestation in honey bee colonies when different regions from Argentina are compared. A total of 361 colonies distributed in five Argentinean eco-regions were examined to evaluate Varroa mite infestation rate during autumn and Nosema sp. presence. Regions were different regarding annual temperature, precipitation and especially vegetation landscape. In addition, beekeeping management practices were obtained from a checklist questionnaire answered by the beekeepers. The prevalence of colonies with high infestation level was lower in semi-arid Chaco followed by humid and transition Chaco regions. Also, colonies that were positive for Nosema sp. showed a higher Varroa infestation rate. The "environmental" effect was stronger compared with the influence of secondary drivers associated with beekeeping activities. As well, a significant association between V. destructor infestation rates and Nosema presence was identified. Under contrasting natural conditions, environment seems a predominant driver on Varroa destructor infestation level in honey bee colonies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Eleventh-century shift in timber procurement areas for the great houses of Chaco Canyon

PubMed Central

Guiterman, Christopher H.; Dean, Jeffrey S.

2016-01-01

An enduring mystery from the great houses of Chaco Canyon is the origin of more than 240,000 construction timbers. We evaluate probable timber procurement areas for seven great houses by applying tree-ring width-based sourcing to a set of 170 timbers. To our knowledge, this is the first use of tree rings to assess timber origins in the southwestern United States. We found that the Chuska and Zuni Mountains (>75 km distant) were the most likely sources, accounting for 70% of timbers. Most notably, procurement areas changed through time. Before 1020 Common Era (CE) nearly all timbers originated from the Zunis (a previously unrecognized source), but by 1060 CE the Chuskas eclipsed the Zuni area in total wood imports. This shift occurred at the onset of Chaco florescence in the 11th century, a time with substantial expansion of existing great houses and the addition of seven new great houses in the Chaco Core area. It also coincides with the proliferation of Chuskan stone tools and pottery in the archaeological record of Chaco Canyon, further underscoring the link between land use and occupation in the Chuska area and the peak of great house construction. Our findings, based on the most temporally specific and replicated evidence of Chacoan resource procurement obtained to date, corroborate the long-standing but recently challenged interpretation that large numbers of timbers were harvested and transported from distant mountain ranges to build the great houses at Chaco Canyon. PMID:26644552

Eleventh-century shift in timber procurement areas for the great houses of Chaco Canyon.

PubMed

Guiterman, Christopher H; Swetnam, Thomas W; Dean, Jeffrey S

2016-02-02

An enduring mystery from the great houses of Chaco Canyon is the origin of more than 240,000 construction timbers. We evaluate probable timber procurement areas for seven great houses by applying tree-ring width-based sourcing to a set of 170 timbers. To our knowledge, this is the first use of tree rings to assess timber origins in the southwestern United States. We found that the Chuska and Zuni Mountains (>75 km distant) were the most likely sources, accounting for 70% of timbers. Most notably, procurement areas changed through time. Before 1020 Common Era (CE) nearly all timbers originated from the Zunis (a previously unrecognized source), but by 1060 CE the Chuskas eclipsed the Zuni area in total wood imports. This shift occurred at the onset of Chaco florescence in the 11th century, a time with substantial expansion of existing great houses and the addition of seven new great houses in the Chaco Core area. It also coincides with the proliferation of Chuskan stone tools and pottery in the archaeological record of Chaco Canyon, further underscoring the link between land use and occupation in the Chuska area and the peak of great house construction. Our findings, based on the most temporally specific and replicated evidence of Chacoan resource procurement obtained to date, corroborate the long-standing but recently challenged interpretation that large numbers of timbers were harvested and transported from distant mountain ranges to build the great houses at Chaco Canyon.

Human Babesiosis, Bolivia, 2013.

PubMed

Gabrielli, Simona; Totino, Valentina; Macchioni, Fabio; Zuñiga, Freddy; Rojas, Patricia; Lara, Yuni; Roselli, Mimmo; Bartoloni, Alessandro; Cancrini, Gabriella

2016-08-01

To investigate human babesiosis in the Bolivian Chaco, in 2013 we tested blood samples from 271 healthy persons living in 2 rural communities in this region. Microscopy and PCR indicated that 3.3% of persons were positive for Babesia microti parasites (US lineage); seroprevalence was 45.7%. Appropriate screening should mitigate the risk for transfusion-associated babesiosis.

[Urban development and the demographic situation in Chaco and its capital between 1960 and 1990].

PubMed

Foschiatti De Dell'orto, A M

1992-01-01

"The large demographic growth registered in the Chaco province [of Argentina] at the beginning of this Century slowed down since the 1950s as a result of the successive economic crisis undergone by this province. The demographic response was the outmigration toward the more developed areas of the country and to the capital city of Chaco. A large share of Resistencia demographic growth is provided by this internal migration. This rapid increase makes inadequate the functional and the service structure of the city." (SUMMARY IN ENG) excerpt

Two new species of Chaco Tullgren from the Atlantic coast of Uruguay (Araneae, Mygalomorphae, Nemesiidae)

PubMed Central

de Oca, Laura Montes; Pérez-Miles, Fernando

2013-01-01

Abstract We describe two new species of the nemesiid spider genus Chaco from Rocha Province, Uruguay. These new species are diagnosed based on genital morphology, male tibial apophysis spination, and burrow entrance. We test cospecificity of one species, Chaco costai,via laboratory mating experiments. The new species are diagnosed and illustrated and habitat characteristics, and capture behavior are described. We conduct a cladistic analysis based on a previously published morphological character matrix that now includes the newly described species. PMID:24146579

Geographical Variation of Deltamethrin Susceptibility of Triatoma infestans (Hemiptera: Reduviidae) in Argentina With Emphasis on a Resistant Focus in the Gran Chaco.

PubMed

Fronza, G; Toloza, A C; Picollo, M I; Spillmann, C; Mougabure-Cueto, G A

2016-07-01

Chagas disease is one of the most important parasitic infections in Latin America. The main vector of the protozoan Trypanosoma cruzi in America is Triatoma infestans, a blood-sucking triatomine bug who is widely distributed in the Gran Chaco ecoregion. Control programs in endemic countries are focused in the elimination of triatomine vectors with pyrethroid insecticides. However, chemical control has failed in the Gran Chaco over the last two decades because of several factors. Previous studies have reported the evolution of different levels of resistance to deltamethrin in Tri. infestans Recently, very high resistance has been found in the central area of the Argentine Gran Chaco. However, the origin and the extension of this remarkably resistant focus remain unknown. The aim of this study was to evaluate the geographical variation of deltamethrin susceptibility of Tri. infestans in different endemic provinces of Argentina, with emphasis in the center of the Argentine Gran Chaco ecoregion where this main vector has not been reduced. Populations of Mendoza, San Juan, Santiago del Estero, and Tucumán provinces were all susceptible. Resistant populations were only detected in the province of Chaco, where a mosaic resistant focus was described at the Güemes Department. It was characterized into three pyrethroid resistance categories: susceptible, low, and highly resistant populations. We found the populations with the highest resistance levels to deltamethrin, with resistant ratios over 1000. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Seroprevalence of Hepatitis A Virus, Hepatitis E Virus, and Helicobacter pylori in Rural Communities of the Bolivian Chaco, 2013.

PubMed

Campolmi, Irene; Spinicci, Michele; Mayaregua, David Rojo; Barahona, Herlan Gamboa; Mantella, Antonia; Lara, Yunni; Roselli, Mimmo; Strohmeyer, Marianne; Corti, Giampaolo; Tolari, Francesco; Pinckert, Joaquín Monasterio; Dalton, Harry R; Bartoloni, Alessandro

2018-05-01

In the Bolivian Chaco, south-east of Bolivia, studies conducted over the past three decades reported hepatitis A virus (HAV) and Helicobacter pylori seroprevalences above 90% and 60%, respectively. Hepatitis E virus (HEV) prevalence was previously found to be 6-7% but is probably an underestimate because of the poor sensitivity of the assays used. In November 2013, we conducted a cross-sectional study of 263 healthy volunteers from two rural communities of the Bolivian Chaco, aiming to reassess HAV, HEV, and H. pylori seroprevalence 10-20 years following the previous surveys. Hepatitis A virus seroprevalence was 95%, with universal exposure after the first decade of life; HEV seroprevalence was considerably higher (31-35%) than that previously reported; H. pylori seroprevalence was 59%, with an age-dependent distribution. The high prevalence of these infections suggests that major efforts are still needed to reduce fecal-oral transmission and to improve human health in the Bolivian Chaco.

Lg and Other Regional Phases in South America

DTIC Science & Technology

1991-10-23

de la dispersi6n de ondas superficiales, Tesis de Grado, Universidad de Chile, Santiago, Chile. Herrmann, R. B. (1980). Q estimates...Altiplanoa; Cordillera de la Costa; Pianicie Costera; Cuenca Superior del Amazonias ; Lianuras Chaco-Benianas; Escudo Brasilego y el La cordillera de ...BrasileRo a partir de la duspersi6r de las ondas superficiales, resis de Grado, Universidad de Chile,

Dramatic Decrease in Prevalence of Soil-Transmitted Helminths and New Insights Into Intestinal Protozoa in Children Living in the Chaco Region, Bolivia

PubMed Central

Macchioni, Fabio; Segundo, Higinio; Gabrielli, Simona; Totino, Valentina; Gonzales, Patricia Rojas; Salazar, Esteban; Bozo, Ricardo; Bartoloni, Alessandro; Cancrini, Gabriella

2015-01-01

We assessed the prevalence of intestinal parasites among 268 2–12-year-old children living in rural areas, small villages, and semi-urban areas of the Chaco region, south-eastern Bolivia. The overall parasitism was 69%. Only protozoa, helminths, or co-infections were observed in 89.2%, 5.9%, or 4.9% of the positive children, respectively. A significant progressive increase in overall parasite prevalence was found when passing from rural areas to small villages and semi-urban areas. The most commonly found species were Entamoeba coli (38.4%), Giardia intestinalis (37.7%), and Blastocystis spp. (16%). Hymenolepis nana was the most prevalent helminth (5.6%), followed by Ascaris lumbricoides and hookworms (1.5% and 0.4%) evidenced only in rural areas and in villages. Molecular diagnostics identified Blastocystis subtypes 9 and 2, and 5 infections by Entamoeba histolytica and 4 by Entamoeba dispar. The dramatic decrease in prevalence of soil-transmitted helminths with respect to that observed about 20 years ago (> 40%) evidences the success of the preventive chemotherapy intervention implemented in 1986. Health education and improved sanitation should be intensified to control protozoan infections. PMID:25711609

Participatory, Multi-Criteria Evaluation Methods as a Means to Increase the Legitimacy and Sustainability of Land Use Planning Processes. The Case of the Chaco Region in Salta, Argentina.

PubMed

Seghezzo, Lucas; Venencia, Cristian; Buliubasich, E Catalina; Iribarnegaray, Martín A; Volante, José N

2017-02-01

Conflicts over land use and ownership are common in South America and generate frequent confrontations among indigenous peoples, small-scale farmers, and large-scale agricultural producers. We argue in this paper that an accurate identification of these conflicts, together with a participatory evaluation of their importance, will increase the social legitimacy of land use planning processes, rendering decision-making more sustainable in the long term. We describe here a participatory, multi-criteria conflict assessment model developed to identify, locate, and categorize land tenure and use conflicts. The model was applied to the case of the "Chaco" region of the province of Salta, in northwestern Argentina. Basic geographic, cadastral, and social information needed to apply the model was made spatially explicit on a Geographic Information System. Results illustrate the contrasting perceptions of different stakeholders (government officials, social and environmental non-governmental organizations, large-scale agricultural producers, and scholars) on the intensity of land use conflicts in the study area. These results can help better understand and address land tenure conflicts in areas with different cultures and conflicting social and enviornmental interests.

Participatory, Multi-Criteria Evaluation Methods as a Means to Increase the Legitimacy and Sustainability of Land Use Planning Processes. The Case of the Chaco Region in Salta, Argentina

NASA Astrophysics Data System (ADS)

Seghezzo, Lucas; Venencia, Cristian; Buliubasich, E. Catalina; Iribarnegaray, Martín A.; Volante, José N.

2017-02-01

Conflicts over land use and ownership are common in South America and generate frequent confrontations among indigenous peoples, small-scale farmers, and large-scale agricultural producers. We argue in this paper that an accurate identification of these conflicts, together with a participatory evaluation of their importance, will increase the social legitimacy of land use planning processes, rendering decision-making more sustainable in the long term. We describe here a participatory, multi-criteria conflict assessment model developed to identify, locate, and categorize land tenure and use conflicts. The model was applied to the case of the "Chaco" region of the province of Salta, in northwestern Argentina. Basic geographic, cadastral, and social information needed to apply the model was made spatially explicit on a Geographic Information System. Results illustrate the contrasting perceptions of different stakeholders (government officials, social and environmental non-governmental organizations, large-scale agricultural producers, and scholars) on the intensity of land use conflicts in the study area. These results can help better understand and address land tenure conflicts in areas with different cultures and conflicting social and enviornmental interests.

Environmental, land cover and land use constraints on the distributional patterns of anurans: Leptodacylus species (Anura, Leptodactylidae) from Dry Chaco

PubMed Central

Medina, Regina Gabriela; Aráoz, Ezequiel

2016-01-01

Subtropical dry forests are among the most vulnerable biomes to land transformation at a global scale. Among them, the Dry Chaco suffers an accelerated change due to agriculture expansion and intensification. The Dry Chaco ecoregion is characterized by high levels of endemisms and species diversity, which are the result of a variety of climates and reliefs, allowing a wide variety of environments. The amphibian group exhibits a high richness in the Dry Chaco, which has been barely studied in relation to land cover changes. We used ecological niche models (ENMs) to assess the potential geographic distribution of 10 Leptodactylus species (Anura, Leptodactylidae), which are mainly distributed within the Dry Chaco. We characterized these distributions environmentally, analyzed their overlap with land cover classes, and assessed their diversity of ecoregions. Also, we evaluated how these species potential distribution is affected by the transformation of land, and quantified the proportional area of the potential distribution in protected areas. We found that temperature seasonality is the main constraint to the occurrence of the species studied, whose main habitats are savannas, grasslands and croplands. The main threats to these species are the effects of climate change over spatial patterns of seasonality, which could affect their breeding and reproduction mode; the loss of their natural habitat; the exposure to contaminants used by intensive agriculture and their underrepresentation in protected areas. PMID:27833796

Environmental, land cover and land use constraints on the distributional patterns of anurans: Leptodacylus species (Anura, Leptodactylidae) from Dry Chaco.

PubMed

Medina, Regina Gabriela; Ponssa, Maria Laura; Aráoz, Ezequiel

2016-01-01

Subtropical dry forests are among the most vulnerable biomes to land transformation at a global scale. Among them, the Dry Chaco suffers an accelerated change due to agriculture expansion and intensification. The Dry Chaco ecoregion is characterized by high levels of endemisms and species diversity, which are the result of a variety of climates and reliefs, allowing a wide variety of environments. The amphibian group exhibits a high richness in the Dry Chaco, which has been barely studied in relation to land cover changes. We used ecological niche models (ENMs) to assess the potential geographic distribution of 10 Leptodactylus species (Anura, Leptodactylidae), which are mainly distributed within the Dry Chaco. We characterized these distributions environmentally, analyzed their overlap with land cover classes, and assessed their diversity of ecoregions. Also, we evaluated how these species potential distribution is affected by the transformation of land, and quantified the proportional area of the potential distribution in protected areas. We found that temperature seasonality is the main constraint to the occurrence of the species studied, whose main habitats are savannas, grasslands and croplands. The main threats to these species are the effects of climate change over spatial patterns of seasonality, which could affect their breeding and reproduction mode; the loss of their natural habitat; the exposure to contaminants used by intensive agriculture and their underrepresentation in protected areas.

Trypanosoma cruzi infection in Triatoma sordida before and after community-wide residual insecticide spraying in the Argentinean Chaco.

PubMed

Macchiaverna, Natalia P; Gaspe, María S; Enriquez, Gustavo F; Tomassone, Laura; Gürtler, Ricardo E; Cardinal, Marta V

2015-03-01

Triatoma sordida is a secondary vector of Trypanosoma cruzi in the Gran Chaco and Cerrado eco-regions where it frequently infests peridomestic and domestic habitats. In a well-defined area of the humid Argentine Chaco, very few T. sordida were found infected when examined by optical microscopic examination (OM). In order to further assess the role of T. sordida and the relative magnitude of subpatent bug infections, we examined the insects for T. cruzi infection, parasite Discrete Typing Units (DTUs) and bloodmeal sources using various molecular techniques. Among 205 bugs with a negative or no OM-based diagnosis, the prevalence of infection determined by kDNA-PCR was nearly the same in bugs captured before (6.3%) and 4 months after insecticide spraying (6.4%). On average, these estimates were sixfold higher than the prevalence of infection based on OM (1.1%). Only TcI was identified, a DTU typically associated with opossums and rodents. Chickens and turkeys were the only bloodmeal sources identified in the infected specimens and the main local hosts at the bugs' capture sites. As birds are refractory to T. cruzi infection, further studies are needed to identify the infectious bloodmeal hosts. The persistent finding of infected T. sordida after community-wide insecticide spraying highlights the need of sustained vector surveillance to effectively prevent T. cruzi transmission in the domestic and peridomestic habitats. Copyright © 2014 Elsevier B.V. All rights reserved.

[Detection of virulence genes of the enteroaggregative pathotype in Escherichia coli strains isolated from groundwater sources in the province of Chaco, Argentina].

PubMed

Lösch, Liliana S; Gariboglio Vázquez, María L; Rivas, Marta; Merino, Luis A

2015-01-01

Groundwater is an important source of drinking water for many communities in Northern Argentina; particularly, in the province of Chaco, where about 14% of households use this natural resource. Enteroaggregative Escherichia coli is an emerging pathogen whose global importance in public health has increased in recent years. Despite the significant risk of disease linked to contaminated water exposure, the prevalence of E. coli pathotypes in aquatic environments is still not so well defined. The aim of the present study was to detect the presence of typical enteroaggregative E. coli through the recognition of its virulence factors aap, AA probe and aggR by molecular techniques. A total of 93 water samples from different small communities of Chaco were analyzed. E. coli was identified in 36 (38.7%) of the tested samples. Six strains isolated from different samples harbored the studied genes. Of these 6 isolates, 3 carried the aap gene, 2 the AA probe and the last one the combination of aap/aggR genes. The prevalence of E. coli isolates harboring enteroaggregative virulence genes in groundwater sources was 6.4%. This work represents the first contribution to the study of the presence and distribution of virulence genes of EAEC in groundwater sources in this region of Argentina. Copyright © 2014 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

[Water and health-related problems, local perception and quality of water sources in a Toba (qom) community in the Impenetrable (Chaco, Argentina)].

PubMed

Martínez, Gustavo J; Beccaglia, Ana M; Llinares, Analía

2014-08-01

We present a transdisciplinary study centering on aspects of environmental health of the Toba (qom) communities that relate to water and health problems of the Impenetrable Chaco region. Information was obtained through the methods and tools of participatory research, household participant observation, and ethnobotanical documentation of species related to water management and use. Vernacular terms referring to the suitability and taste of the water, as well as representations, attitudes and practices related to water collection and purification were recorded. In addition, a microbiological and physicochemical analysis of the water was performed and compared with the perceptual categories. It was observed that perceptual aspects were in tension with the hygienic quality of water. We documented phreatophyte plants, indicative of the presence of water, as well as plants that store water, act as flocculants, refresh the water or improve taste. The results of this research are discussed from an ecosystem approach and its relationship to the development of proposals for intervention.

Deforestation of "degraded" rangelands: The Argentine Chaco enters the next stage of the Anthropocene

USDA-ARS?s Scientific Manuscript database

Twenty years ago I completed my Master’s work in the Chaco forests of northern Argentina. The native forests are, in fact, rangelands. In addition to livestock grazing, there is timber extraction, wildlife harvest (think tegu lizard cowboy boots), and charcoal production. I took part in a project co...

[The "Chaco": eatable medicinal clay in the Peruvian highlands and his properties in digestive diseases].

PubMed

Castillo Contreras, Ofelia; Frisancho Velarde, Oscar

2015-01-01

The inhabitants of the peruvian-bolivian plateau consume a natural substance known as "Chaco", widespread since pre-Columbian era and appreciated for its digestive properties. The Chaco is an edible medicinal clay that is used as slurry with water to restrain dyspeptic discomfort or acid-peptic manifestations. In this contribution we present physicochemical aspects of the composition of the Chaco, experimental animal studies that evaluate its antiulcer effect and in vitro test that studies the antacid property. The proposed mechanism of therapeutic action is due to a cytoprotective effect on the gastric mucosa by independent mechanisms of acid secretion inhibition, as it has no antacid property in vitro. Also it has an adsorptivity to different organic molecules due to their large surface area and tetrahedral charge that makes it to interact with polar substances such as water and toxins. The other purpose of this special contribution is to recognize the coexistence of "Traditional Medicine" and "Western Medicine", a situation which leads to the need for preclinical research of various natural resources.

Temporal Changes in Forest Contexts at Multiple Extents: Three Decades of Fragmentation in the Gran Chaco (1979-2010), Central Argentina.

PubMed

Frate, Ludovico; Acosta, Alicia T R; Cabido, Marcelo; Hoyos, Laura; Carranza, Maria Laura

2015-01-01

The context in which a forest exists strongly influences its function and sustainability. Unveiling the multi-scale nature of forest fragmentation context is crucial to understand how human activities affect the spatial patterns of forests across a range of scales. However, this issue remains almost unexplored in subtropical ecosystems. In this study, we analyzed temporal changes (1979-2010) in forest contexts in the Argentinean dry Chaco at multiple extents. We classified forests over the last three decades based on forest context amount (Pf) and structural connectivity (Pff), which were measured using a moving window approach fixed at eight different extents (from local, ~ 6 ha, to regional, ~ 8300 ha). Specific multi-scale forest context profiles (for the years 1979 and 2010) were defined by projecting Pf vs. Pff mean values and were compared across spatial extents. The distributions of Pf across scales were described by scalograms and their shapes over time were compared. The amount of agricultural land and rangelands across the scales were also analyzed. The dry Chaco has undergone an intensive process of fragmentation, resulting in a shift from landscapes dominated by forests with gaps of rangelands to landscapes where small forest patches are embedded in agricultural lands. Multi-scale fragmentation analysis depicted landscapes in which local exploitation, which perforates forest cover, occurs alongside extensive forest clearings, reducing forests to small and isolated patches surrounded by agricultural lands. In addition, the temporal diminution of Pf's variability along with the increment of the mean slope of the Pf 's scalograms, indicate a simplification of the spatial pattern of forest over time. The observed changes have most likely been the result of the interplay between human activities and environmental constraints, which have shaped the spatial patterns of forests across scales. Based on our results, strategies for the conservation and sustainable management of the dry Chaco should take into account both the context of each habitat location and the scales over which a forest pattern might be preserved, altered or restored.

Temporal Changes in Forest Contexts at Multiple Extents: Three Decades of Fragmentation in the Gran Chaco (1979-2010), Central Argentina

PubMed Central

Frate, Ludovico; Acosta, Alicia T. R.; Cabido, Marcelo; Hoyos, Laura; Carranza, Maria Laura

2015-01-01

The context in which a forest exists strongly influences its function and sustainability. Unveiling the multi-scale nature of forest fragmentation context is crucial to understand how human activities affect the spatial patterns of forests across a range of scales. However, this issue remains almost unexplored in subtropical ecosystems. In this study, we analyzed temporal changes (1979–2010) in forest contexts in the Argentinean dry Chaco at multiple extents. We classified forests over the last three decades based on forest context amount (P f) and structural connectivity (P ff), which were measured using a moving window approach fixed at eight different extents (from local, ~ 6 ha, to regional, ~ 8300 ha). Specific multi-scale forest context profiles (for the years 1979 and 2010) were defined by projecting P f vs. P ff mean values and were compared across spatial extents. The distributions of P f across scales were described by scalograms and their shapes over time were compared. The amount of agricultural land and rangelands across the scales were also analyzed. The dry Chaco has undergone an intensive process of fragmentation, resulting in a shift from landscapes dominated by forests with gaps of rangelands to landscapes where small forest patches are embedded in agricultural lands. Multi-scale fragmentation analysis depicted landscapes in which local exploitation, which perforates forest cover, occurs alongside extensive forest clearings, reducing forests to small and isolated patches surrounded by agricultural lands. In addition, the temporal diminution of P f’s variability along with the increment of the mean slope of the P f ‘s scalograms, indicate a simplification of the spatial pattern of forest over time. The observed changes have most likely been the result of the interplay between human activities and environmental constraints, which have shaped the spatial patterns of forests across scales. Based on our results, strategies for the conservation and sustainable management of the dry Chaco should take into account both the context of each habitat location and the scales over which a forest pattern might be preserved, altered or restored. PMID:26630387

The freshwater lens of Benjamín Aceval, Chaco, Paraguay: a terrestrial analogue of an oceanic island lens

NASA Astrophysics Data System (ADS)

Houben, Georg; Noell, Ursula; Vassolo, Sara; Grissemann, Christoph; Geyh, Mebus; Stadler, Susanne; Dose, Eduardo J.; Vera, Sofia

2014-12-01

The occurrence of a freshwater lens in the Paraguayan Chaco, 900 km away from the ocean, is reported. It is located underneath sandstone hills, surrounded by lowlands with predominantly saline groundwater. Its geometry was delineated using geoelectrical and electromagnetic investigations. The unusual height of the fresh groundwater level can be attributed to the presence of a confining layer at depth. The lens receives its recharge exclusively from rainfall during the hot and humid summer months. It predominantly contains water predating the atmospheric atomic bomb tests, some of it probably up to a thousand or more years old. The water balance shows that extraction currently does not exceed recharge in normal years. However, the available volume of groundwater leaves little room for a further increase of extraction in the future. Recharge is augmented by return flow from thousands of latrines and cess pits, and this has lead to widespread contamination of the groundwater by faecal bacteria.

Indigenous Starter Cultures to Improve Quality of Artisanal Dry Fermented Sausages from Chaco (Argentina).

PubMed

Palavecino Prpich, Noelia Z; Castro, Marcela P; Cayré, María E; Garro, Oscar A; Vignolo, Graciela M

2015-01-01

Lactic acid bacteria (LAB) and coagulase negative cocci (CNC) were isolated from artisanal dry sausages sampled from the northeastern region of Chaco, Argentina. In order to evaluate their performance in situ and considering technological features of the isolated strains, two mixed selected autochthonous starter cultures (SAS) were designed: (i) SAS-1 (Lactobacillus sakei 487 + Staphylococcus vitulinus C2) and (ii) SAS-2 (L. sakei 442 + S. xylosus C8). Cultures were introduced into dry sausage manufacturing process at a local small-scale facility. Microbiological and physicochemical parameters were monitored throughout fermentation and ripening periods, while sensory attributes of the final products were evaluated by a trained panel. Lactic acid bacteria revealed their ability to colonize and adapt properly to the meat matrix, inhibiting the growth of spontaneous microflora and enhancing safety and hygienic profile of the products. Both SAS showed a beneficial effect on lipid oxidation and texture of the final products. Staphylococcus vitulinus C2, from SAS-1, promoted a better redness of the final product. Sensory profile revealed that SAS addition preserved typical sensory attributes. Introduction of these cultures could provide an additional tool to standardize manufacturing processes aiming to enhance safety and quality while keeping typical sensory attributes of regional dry fermented sausages.

Experimental control of Triatoma infestans in poor rural villages of Bolivia through community participation

PubMed Central

Lardeux, Frédéric; Depickère, Stéphanie; Aliaga, Claudia; Chavez, Tamara; Zambrana, Lilian

2015-01-01

Background Triatoma infestans is the main vector of Chagas disease in the southern cone countries. Present control strategies based on indoor and outdoor residual insecticide spraying are not sufficient to control disease transmission, particularly in Bolivia. Techniques based on the management of the human environment may be good alternatives or supplements. Methods Social and entomological surveys were carried out in four villages of Bolivia situated in the dry inter-Andean Valleys and the Chaco region. Risk factors for house infestation by T. infestans were identified, and an eco-health intervention based on education and community participation was carried out to reduce the risks of house infestation. It consisted of implementing simple and low cost vector control techniques such as coating of mud walls, cleaning activities and removal of poultry that enter rooms to lay eggs. Results The eco-health intervention significantly reduced the number of infested bedrooms, the mean abundance of T. infestans in bedrooms and beds, especially in the Chaco region. Mud wall coating was well accepted and could be proposed as a supplementary tool to the National Program of Chagas Disease Control to enhance the effects of insecticide sprayings. Conclusions Even if cleaning activities were still neglected, community participation proved to be effective in reducing house infestation. PMID:25604766

Dramatic decrease in prevalence of soil-transmitted helminths and new insights into intestinal protozoa in children living in the Chaco region, Bolivia.

PubMed

Macchioni, Fabio; Segundo, Higinio; Gabrielli, Simona; Totino, Valentina; Gonzales, Patricia Rojas; Salazar, Esteban; Bozo, Ricardo; Bartoloni, Alessandro; Cancrini, Gabriella

2015-04-01

We assessed the prevalence of intestinal parasites among 268 2-12-year-old children living in rural areas, small villages, and semi-urban areas of the Chaco region, south-eastern Bolivia. The overall parasitism was 69%. Only protozoa, helminths, or co-infections were observed in 89.2%, 5.9%, or 4.9% of the positive children, respectively. A significant progressive increase in overall parasite prevalence was found when passing from rural areas to small villages and semi-urban areas. The most commonly found species were Entamoeba coli (38.4%), Giardia intestinalis (37.7%), and Blastocystis spp. (16%). Hymenolepis nana was the most prevalent helminth (5.6%), followed by Ascaris lumbricoides and hookworms (1.5% and 0.4%) evidenced only in rural areas and in villages. Molecular diagnostics identified Blastocystis subtypes 9 and 2, and 5 infections by Entamoeba histolytica and 4 by Entamoeba dispar. The dramatic decrease in prevalence of soil-transmitted helminths with respect to that observed about 20 years ago (> 40%) evidences the success of the preventive chemotherapy intervention implemented in 1986. Health education and improved sanitation should be intensified to control protozoan infections. © The American Society of Tropical Medicine and Hygiene.

Prehistoric deforestation at Chaco Canyon?

PubMed Central

Wills, W. H.; Drake, Brandon L.; Dorshow, Wetherbee B.

2014-01-01

Ancient societies are often used to illustrate the potential problems stemming from unsustainable land-use practices because the past seems rife with examples of sociopolitical “collapse” associated with the exhaustion of finite resources. Just as frequently, and typically in response to such presentations, archaeologists and other specialists caution against seeking simple cause-and effect-relationships in the complex data that comprise the archaeological record. In this study we examine the famous case of Chaco Canyon, New Mexico, during the Bonito Phase (ca. AD 860–1140), which has become a prominent popular illustration of ecological and social catastrophe attributed to deforestation. We conclude that there is no substantive evidence for deforestation at Chaco and no obvious indications that the depopulation of the canyon in the 13th century was caused by any specific cultural practices or natural events. Clearly there was a reason why these farming people eventually moved elsewhere, but the archaeological record has not yet produced compelling empirical evidence for what that reason might have been. Until such evidence appears, the legacy of Ancestral Pueblo society in Chaco should not be used as a cautionary story about socioeconomic failures in the modern world. PMID:25071220

The Role of Small Woodland Remnants on Ground Dwelling Insect Conservation in Chaco Serrano, Central Argentina

PubMed Central

Moreno, María Laura; Fernández, María Guadalupe; Molina, Silvia Itati; Valladares, Graciela

2013-01-01

Many terrestrial ecosystems are changing due to extensive land use and habitat fragmentation, posing a major threat to biodiversity. In this study, the effects of patch size, isolation, and edge/interior localization on the ground dwelling insect communities in the Chaco Serrano woodland remnants in central Argentina were examined. Sampling was carried out in December 2003 and March 2004 in nine remnants (0.57 to 1000 hectares) using pitfall traps. In total, 7071 individuals representing 12 orders and 79 families were recorded. The taxonomic composition of these communities was linked to remnant size. Insect abundance increased (as did their richness, albeit marginally) as remnant area decreased, with no significant effects of isolation or edge/interior localization on abundance, richness, or diversity. No differential area effects were observed when abundance and richness of predators, scavengers, and herbivores were compared. Thus, ground insect communities in fragmented Chaco Serrano seem to respond mainly to patch level, rather than to within-patch (edge effects) or landscape (isolation) level variables. These results suggest that small Chaco Serrano remnants, by supporting larger ground-dwelling insect assemblages, may play an important role from a conservation viewpoint. PMID:23902409

The role of small woodland remnants on ground dwelling insect conservation in Chaco Serrano, Central Argentina.

PubMed

Moreno, María Laura; Fernández, María Guadalupe; Molina, Silvia Itati; Valladares, Graciela

2013-01-01

Many terrestrial ecosystems are changing due to extensive land use and habitat fragmentation, posing a major threat to biodiversity. In this study, the effects of patch size, isolation, and edge/interior localization on the ground dwelling insect communities in the Chaco Serrano woodland remnants in central Argentina were examined. Sampling was carried out in December 2003 and March 2004 in nine remnants (0.57 to 1000 hectares) using pitfall traps. In total, 7071 individuals representing 12 orders and 79 families were recorded. The taxonomic composition of these communities was linked to remnant size. Insect abundance increased (as did their richness, albeit marginally) as remnant area decreased, with no significant effects of isolation or edge/interior localization on abundance, richness, or diversity. No differential area effects were observed when abundance and richness of predators, scavengers, and herbivores were compared. Thus, ground insect communities in fragmented Chaco Serrano seem to respond mainly to patch level, rather than to within-patch (edge effects) or landscape (isolation) level variables. These results suggest that small Chaco Serrano remnants, by supporting larger ground-dwelling insect assemblages, may play an important role from a conservation viewpoint.

Plant antiherbivore defenses in Fabaceae species of the Chaco.

PubMed

Lima, T E; Sartori, A L B; Rodrigues, M L M

2017-01-01

The establishment and maintenance of plant species in the Chaco, one of the widest continuous areas of forests in the South American with sharp climatic variations, are possibly related to biological features favoring plants with particular defenses. This study assesses the physical and chemical defenses mechanisms against herbivores of vegetative and reproductive organs. Its analyses of 12 species of Fabaceae (Leguminosae) collected in remnants of Brazilian Chaco shows that 75% present structural defense characters and 50% have chemical defense - defense proteins in their seeds, like protease inhibitors and lectins. Physical defenses occur mainly on branches (78% of the species), leaves (67%), and reproductive organs (56%). The most common physical characters are trichomes and thorns, whose color represents a cryptic character since it does not contrast with the other plant structures. Defense proteins occur in different concentrations and molecular weight classes in the seeds of most species. Protease inhibitors are reported for the first time in seeds of: Albizia niopoides, Anadenanthera colubrina, Mimosa glutinosa, Prosopis rubriflora, and Poincianella pluviosa. The occurrence of physical and chemical defenses in members of Fabaceae indicate no associations between defense characters in these plant species of the Chaco.

Geographic variation of Trypanosoma cruzi discrete typing units from Triatoma infestans at different spatial scales.

PubMed

Fernández, María Del Pilar; Cecere, María Carla; Lanati, Leonardo Alejandro; Lauricella, Marta Alicia; Schijman, Alejandro Gabriel; Gürtler, Ricardo Esteban; Cardinal, Marta Victoria

2014-12-01

We assessed the diversity and distribution of Trypanosoma cruzi discrete typing units (DTU) in Triatoma infestans populations and its association with local vector-borne transmission levels at various geographic scales. At a local scale, we found high predominance (92.4%) of TcVI over TcV in 68 microscope-positive T. infestans collected in rural communities in Santiago del Estero province in northern Argentina. TcV was more often found in communities with higher house infestation prevalence compatible with active vector-borne transmission. Humans and dogs were the main bloodmeal sources of the TcV- and TcVI-infected bugs. At a broader scale, the greatest variation in DTU diversity was found within the Argentine Chaco (227 microscope-positive bugs), mainly related to differences in equitability between TcVI and TcV among study areas. At a country-wide level, a meta-analysis of published data revealed clear geographic variations in the distribution of DTUs across countries. A correspondence analysis showed that DTU distributions in domestic T. infestans were more similar within Argentina (dominated by TcVI) and within Bolivia (where TcI and TcV had similar relative frequencies), whereas large heterogeneity was found within Chile. DTU diversity was lower in the western Argentine Chaco region and Paraguay (D=0.14-0.22) than in the eastern Argentine Chaco, Bolivia and Chile (D=0.20-0.68). Simultaneous DTU identifications of T. cruzi-infected hosts and triatomines across areas differing in epidemiological status are needed to shed new light on the structure and dynamics of parasite transmission cycles. Copyright © 2014 Elsevier B.V. All rights reserved.

Photometric Assessment of Night Sky Quality over Chaco Culture National Historical Park

NASA Astrophysics Data System (ADS)

Hung, Li-Wei; Duriscoe, Dan M.; White, Jeremy M.; Meadows, Bob; Anderson, Sharolyn J.

2018-06-01

The US National Park Service (NPS) characterizes night sky conditions over Chaco Culture National Historical Park using measurements in the park and satellite data. The park is located near the geographic center of the San Juan Basin of northwestern New Mexico and the adjacent Four Corners state. In the park, we capture a series of night sky images in V-band using our mobile camera system on nine nights from 2001 to 2016 at four sites. We perform absolute photometric calibration and determine the image placement to obtain multiple 45-million-pixel mosaic images of the entire night sky. We also model the regional night sky conditions in and around the park based on 2016 VIIRS satellite data. The average zenith brightness is 21.5 mag/arcsec2, and the whole sky is only ~16% brighter than the natural conditions. The faintest stars visible to naked eyes have magnitude of approximately 7.0, reaching the sensitivity limit of human eyes. The main impacts to Chaco’s night sky quality are the light domes from Albuquerque, Rio Rancho, Farmington, Bloomfield, Gallup, Santa Fe, Grants, and Crown Point. A few of these light domes exceed the natural brightness of the Milky Way. Additionally, glare sources from oil and gas development sites are visible along the north and east horizons. Overall, the night sky quality at Chaco Culture National Historical Park is very good. The park preserves to a large extent the natural illumination cycles, providing a refuge for crepuscular and nocturnal species. During clear and dark nights, visitors have an opportunity to see the Milky Way from nearly horizon to horizon, complete constellations, and faint astronomical objects and natural sources of light such as the Andromeda Galaxy, zodiacal light, and airglow.

Soil moisture and excavation behaviour in the Chaco leaf-cutting ant (Atta vollenweideri): digging performance and prevention of water inflow into the nest.

PubMed

Pielström, Steffen; Roces, Flavio

2014-01-01

The Chaco leaf-cutting ant Atta vollenweideri is native to the clay-heavy soils of the Gran Chaco region in South America. Because of seasonal floods, colonies are regularly exposed to varying moisture across the soil profile, a factor that not only strongly influences workers' digging performance during nest building, but also determines the suitability of the soil for the rearing of the colony's symbiotic fungus. In this study, we investigated the effects of varying soil moisture on behaviours associated with underground nest building in A. vollenweideri. This was done in a series of laboratory experiments using standardised, plastic clay-water mixtures with gravimetric water contents ranging from relatively brittle material to mixtures close to the liquid limit. Our experiments showed that preference and group-level digging rate increased with increasing water content, but then dropped considerably for extremely moist materials. The production of vibrational recruitment signals during digging showed, on the contrary, a slightly negative linear correlation with soil moisture. Workers formed and carried clay pellets at higher rates in moist clay, even at the highest water content tested. Hence, their weak preference and low group-level excavation rate observed for that mixture cannot be explained by any inability to work with the material. More likely, extremely high moistures may indicate locations unsuitable for nest building. To test this hypothesis, we simulated a situation in which workers excavated an upward tunnel below accumulated surface water. The ants stopped digging about 12 mm below the interface soil/water, a behaviour representing a possible adaptation to the threat of water inflow field colonies are exposed to while digging under seasonally flooded soils. Possible roles of soil water in the temporal and spatial pattern of nest growth are discussed.

Traditions of the Sun, One Model for Expanding Audience Access

NASA Astrophysics Data System (ADS)

Hawkins, I.; Paglierani, R.

2006-12-01

The Internet is a powerful tool with which to expand audience access, bringing students, teachers and the public to places and resources they might not otherwise visit or make use of. We will present Traditions of the Sun, an experiential Web site that invites exploration of the world's ancient observatories with special emphasis on Chaco Culture National Historic Park in the Four Corners region of the US and several sites in the Yucatan Peninsula in Mexico. Traditions of the Sun includes resources in English and Spanish along with a unique trilingual on-line book, "Traditions of the Sun, A Photographic Journal," containing explanatory text in Yucatec Maya as well. Traditions of the Sun offers rich opportunities for virtual visits to ancient sites used for solar observing while learning about current NASA research on the Sun and indigenous solar practices within a larger historical and cultural context. The site contains hundreds of photographs, historic images and rich multimedia to help tell the story of the Sun-Earth Connection. Visitors to the site can zoom in on the great Mayan cities of Chichen Itza, Uxmal, Dzibilchaltun, and Mayapan to learn about Mayan astronomy, history, culture, and science. They can also visit Chaco Canyon to watch sunrise over Pueblo Bonito on the summer solstice, take a virtual reality tour of the great kiva at Casa Rinconada or see panoramic vistas from Fajada Butte, an area which, for preservation purposes, is restricted to the public. Traditions of the Sun provides one model of how exploration and discovery can come to life for both formal and informal audiences via the Internet. Traditions of the Sun is a collaborative project between NASA's Sun-Earth Connection Education Forum, the National Park Service, Instituto National de Antropologia e Historia, Universidad Nacional Autonoma de Mexico, and Ideum.

Early procurement of scarlet macaws and the emergence of social complexity in Chaco Canyon, NM.

PubMed

Watson, Adam S; Plog, Stephen; Culleton, Brendan J; Gilman, Patricia A; LeBlanc, Steven A; Whiteley, Peter M; Claramunt, Santiago; Kennett, Douglas J

2015-07-07

High-precision accelerator mass spectrometer (AMS) (14)C dates of scarlet macaw (Ara macao) skeletal remains provide the first direct evidence from Chaco Canyon in northwestern New Mexico that these Neotropical birds were procured from Mesoamerica by Pueblo people as early as ∼ A.D. 900-975. Chaco was a prominent prehistoric Pueblo center with a dense concentration of multistoried great houses constructed from the 9th through early 12th centuries. At the best known great house of Pueblo Bonito, unusual burial crypts and significant quantities of exotic and symbolically important materials, including scarlet macaws, turquoise, marine shell, and cacao, suggest societal complexity unprecedented elsewhere in the Puebloan world. Scarlet macaws are known markers of social and political status among the Pueblos. New AMS (14)C-dated scarlet macaw remains from Pueblo Bonito demonstrate that these birds were acquired persistently from Mesoamerica between A.D. 900 and 1150. Most of the macaws date before the hypothesized apogeal Chacoan period (A.D. 1040-1110) to which they are commonly attributed. The 10th century acquisition of these birds is consistent with the hypothesis that more formalized status hierarchies developed with significant connections to Mesoamerica before the post-A.D. 1040 architectural florescence in Chaco Canyon.

Early procurement of scarlet macaws and the emergence of social complexity in Chaco Canyon, NM

PubMed Central

Watson, Adam S.; Plog, Stephen; Culleton, Brendan J.; Gilman, Patricia A.; LeBlanc, Steven A.; Whiteley, Peter M.; Claramunt, Santiago; Kennett, Douglas J.

2015-01-01

High-precision accelerator mass spectrometer (AMS) 14C dates of scarlet macaw (Ara macao) skeletal remains provide the first direct evidence from Chaco Canyon in northwestern New Mexico that these Neotropical birds were procured from Mesoamerica by Pueblo people as early as ∼A.D. 900–975. Chaco was a prominent prehistoric Pueblo center with a dense concentration of multistoried great houses constructed from the 9th through early 12th centuries. At the best known great house of Pueblo Bonito, unusual burial crypts and significant quantities of exotic and symbolically important materials, including scarlet macaws, turquoise, marine shell, and cacao, suggest societal complexity unprecedented elsewhere in the Puebloan world. Scarlet macaws are known markers of social and political status among the Pueblos. New AMS 14C-dated scarlet macaw remains from Pueblo Bonito demonstrate that these birds were acquired persistently from Mesoamerica between A.D. 900 and 1150. Most of the macaws date before the hypothesized apogeal Chacoan period (A.D. 1040–1110) to which they are commonly attributed. The 10th century acquisition of these birds is consistent with the hypothesis that more formalized status hierarchies developed with significant connections to Mesoamerica before the post-A.D. 1040 architectural florescence in Chaco Canyon. PMID:26100874

Myth and catastrophic reality: using cosmogonic mythology to identify cosmic impacts and massive plinian eruptions in holocene South America.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masse, W. B.

Major natural catastrophes (e.g., 'universal' floods, fire, darkness, and sky falling down) are prominently reflected in traditional South American creation myths, cosmology, religion, and worldview. We are now beginning to recognize that cosmogonic myths represent a rich and largely untapped data set concerning the most dramatic natural events and processes experienced by each cultural group during the past several thousand years. Observational details regarding specific catastrophes are encoded in myth storylines, typically cast in terms of supernatural characters and actions. Not only are the myths amenable to scientific analysis, but also some sets of myths encode multiple catastrophes in meaningfulmore » relative chronological order. The present study considers more than 4200 myths, including more than 260 'universal' catastrophe myths from cultural groups throughout South America. These myths are examined in light of available geological, paleoenvironmental, archeological, and documentary evidence. Our analysis reveals three possible ultra-plinian volcanic eruptions, two in Columbia and the other in the Gran Chaco, the latter likely associated with a poorly dated late Holocene eruption of Nuevo Mundo in central Bolivia. Our analysis also identifies a set of traditions likely linked with the well-known Campo del Cielo iron meteorite impact in northern Argentina originally hypothesized to have occurred around 4000 years ago. Intriguingly, these traditions strongly suggest that the Campo del Cielo impact triggered widespread mass fires in the Gran Chaco region and possibly in the Brazilian Highlands. Several other potential cosmic impacts, distinct from Campo del Cielo, are hinted at in the mythology of other locations in South America. The numerous catastrophe myths in the Gran Chaco region exhibit the most coherent chronological sequence of any South American region. The sequence begins with a 'Great Flood,' by far the most widespread catastrophe myth in South America, typically represented as the beginning of our modern world. The great flood is followed 'many generations' later by the 'Great Fire' (hypothesized as the Campo del Cielo impact) with the 'Great Darkness' and 'sky falling down' (hypothesized as the Nuevo Mundo eruption) being the most recent catastrophe, occurring 'many generations' after the great fire. We draw upon the physical record to suggest rough calendrical dates for these witnessed catastrophic events.« less

Experimental control of Triatoma infestans in poor rural villages of Bolivia through community participation.

PubMed

Lardeux, Frédéric; Depickère, Stéphanie; Aliaga, Claudia; Chavez, Tamara; Zambrana, Lilian

2015-02-01

Triatoma infestans is the main vector of Chagas disease in the southern cone countries. Present control strategies based on indoor and outdoor residual insecticide spraying are not sufficient to control disease transmission, particularly in Bolivia. Techniques based on the management of the human environment may be good alternatives or supplements. Social and entomological surveys were carried out in four villages of Bolivia situated in the dry inter-Andean Valleys and the Chaco region. Risk factors for house infestation by T. infestans were identified, and an eco-health intervention based on education and community participation was carried out to reduce the risks of house infestation. It consisted of implementing simple and low cost vector control techniques such as coating of mud walls, cleaning activities and removal of poultry that enter rooms to lay eggs. The eco-health intervention significantly reduced the number of infested bedrooms, the mean abundance of T. infestans in bedrooms and beds, especially in the Chaco region. Mud wall coating was well accepted and could be proposed as a supplementary tool to the National Program of Chagas Disease Control to enhance the effects of insecticide sprayings. Even if cleaning activities were still neglected, community participation proved to be effective in reducing house infestation. © The author 2015. The World Health Organization has granted Oxford University Press permission for the reproduction of this article.

Ñuagapua (Chaco, Bolivia): Evidence for the latest occurrence of megafauna in association with human remains in South America

NASA Astrophysics Data System (ADS)

Coltorti, Mauro; Della Fazia, Jacopo; Paredes Rios, Freddy; Tito, Giuseppe

2012-02-01

Quebrada (stream) Ñuagapua, which is located in the Bolivian Chaco in the Andean foothill generates an alluvial fan many kilometres in length. Three major lithostratigraphic units characterise the sedimentary sequence in this region. The lower and upper parts are formed from predominantly sandy sediments that demonstrate rapid growth of the alluvial fan, associated with an intense erosion of barren slopes. The intermediate unit consists of forest soil that seals deep channels containing bones together with a forest association. The remains of a wooden plank, dated 140 yr BP, were found at the top of this soil, which laterally contains charcoals, ash layers and large charred trunks, sometimes in growth positions. Roots localised in this layer also sustain a number of very large still living trees. These findings are evidence of a recent phase of alluvial fan sedimentation resulting from slope erosion activated by forest clearing. The Chaco has been intensively settled for agricultural and pastoral purposes since the 18th century. The lower unit contains a hearth, scattered burnt bones, flint flakes and ceramic artefacts. Radiometric dating indicates a middle Holocene human occupation, between ca. 7.79 and 6.65 ka cal yr BP. We suggest that the sedimentary unit is associated with intense soil erosion processes triggered by early Neolithic deforestation. A sandy layer of the lower unit, slightly above the archaeological remains, contains transported bones of megafaunal elements that apparently represent the South American latest occurrence of some extinct taxa. The mammal association is highly heterogeneous, containing species living in aquatic, forest, prairie and savannah environments from a very specific layer that represents the almost simultaneous burial of animals killed slightly up-valley. This anomalous association is probably the result of human impact as opening the forest favoured the introduction of open environment fauna that had previously survived on the southernmost part of the continent. Therefore, humans may have played a role in mammalian extinctions in this region, either directly, due to hunting, or due to changing the paleoenvironmental conditions on a wider scale.

Trees, chemistry, and prehistory in the American Southwest

USGS Publications Warehouse

Durand, S.R.; Shelley, P.H.; Antweiler, Ronald C.; Taylor, Howard E.

1999-01-01

At least 200 000 trees were used in the building construction in Chaco Canyon, New Mexico, from about (AD) 850-1150. A large portion of these construction timbers were transported 50 km or more and the harvesting location(s) is not known. We argue that a feasible method for determining the wood source areas is to chemically characterize the possible source areas using modern wood and then attempt to match the prehistoric timbers to the modern signatures. This paper establishes the feasibility of this method. ICP-AES was employed to obtain element concentration values for 29 elements, from 62 trees, on three bedrock types. We conclude that it is possible to isolate the variation due to lithology if one controls for wood type (bark, sapwood, heartwood). In addition, ICP-MS was used for the analysis of a small sample of ancient wood. Data from these determinations are presented and the results indicate that the elemental variation is consistent with the most current model of wood use practices in Chaco Canyon. The methods pioneered here should be broadly applicable for determining wood source areas.

The presence of species of Pseudochironomus Malloch 1915 (Diptera: Chironomidae) in watercourses of Chaco Serrano Ecoregion (Argentina, South America).

PubMed

Paggi, Analía C; Rodriguez Garay, Gretel N

2015-05-15

Male imagos of Pseudochironomus viridis (Kieffer) are redescribed, the immature stages are described and figured for the first time. During this study, larva and pupal exuviae associated to P. richardsoni (Malloch) were recorded for the first time for South America. The specimens were collected from a stream and a river in the Pampasic Hills System in the Chaco Serrano ecoregion of Argentina.

Centers of control: Revealing elites among the Ancestral Pueblo during the "Chaco Phenomenon".

PubMed

Harrod, Ryan P

The use of violence as a means of social control among higher status members of the Ancestral Pueblo is explored by using data derived from the burials and the burial context of several sites between AD 850 and 1300. High-status burials, while relatively rare in the archeological record, are of interest because of the role the individuals are assumed to have played in the culture. It has been suggested that there were "elites" among the Ancestral Pueblo during a particularly volatile period that corresponds with the growth, development, and decline of Chacon Canyon and to a lesser extent Aztec Ruins, two major political and ritual centers. Using a bioarchaeological approach that integrates the human remains with the archeological context, burials from Chaco Canyon were compared with burials from other sites in the region based on demographic (age and sex), nutritional (stature), activity (robusticity and entheses), health (pathological conditions), violence (cranial trauma), and cultural (mortuary pattern) patterns. Crucial for expanding our understanding of the role of hierarchy and social control in the Pueblo world, these data suggest that there were high-status individuals who functioned as political and ceremonial leaders. Copyright © 2012 Elsevier Inc. All rights reserved.

Over Six Thousand Trypanosoma cruzi Strains Classified into Discrete Typing Units (DTUs): Attempt at an Inventory.

PubMed

Brenière, Simone Frédérique; Waleckx, Etienne; Barnabé, Christian

2016-08-01

Trypanosoma cruzi, the causative agent of Chagas disease, presents wide genetic diversity. Currently, six discrete typing units (DTUs), named TcI to TcVI, and a seventh one called TcBat are used for strain typing. Beyond the debate concerning this classification, this systematic review has attempted to provide an inventory by compiling the results of 137 articles that have used it. A total of 6,343 DTU identifications were analyzed according to the geographical and host origins. Ninety-one percent of the data available is linked to South America. This sample, although not free of potential bias, nevertheless provides today's picture of T. cruzi genetic diversity that is closest to reality. DTUs were genotyped from 158 species, including 42 vector species. Remarkably, TcI predominated in the overall sample (around 60%), in both sylvatic and domestic cycles. This DTU known to present a high genetic diversity, is very widely distributed geographically, compatible with a long-term evolution. The marsupial is thought to be its most ancestral host and the Gran Chaco region the place of its putative origin. TcII was rarely sampled (9.6%), absent, or extremely rare in North and Central America, and more frequently identified in domestic cycles than in sylvatic cycles. It has a low genetic diversity and has probably found refuge in some mammal species. It is thought to originate in the south-Amazon area. TcIII and TcIV were also rarely sampled. They showed substantial genetic diversity and are thought to be composed of possible polyphyletic subgroups. Even if they are mostly associated with sylvatic transmission cycles, a total of 150 human infections with these DTUs have been reported. TcV and TcVI are clearly associated with domestic transmission cycles. Less than 10% of these DTUs were identified together in sylvatic hosts. They are thought to originate in the Gran Chaco region, where they are predominant and where putative parents exist (TcII and TcIII). Trends in host-DTU specificities exist, but generally it seems that the complexity of the cycles and the participation of numerous vectors and mammal hosts in a shared area, maintains DTU diversity.

How does a viviparous semifossorial lizard reproduce? Ophiodes intermedius (Squamata: Anguidae) from subtropical climate in the Wet Chaco region of Argentina.

PubMed

Ortiz, Martín A; Boretto, Jorgelina M; Ibargüengoytía, Nora R

2017-04-01

The best predictors of reproductive patterns are commonly associated with climate factors, but evolutionary history also plays an important role. The semifossorial and viviparous lizard Ophiodes intermedius from the Wet Chaco region of Argentina showed an annual cycle with asynchrony between males and females and an unusual pattern for subtropical climates, with vitellogenesis beginning in autumn, ovulation and copulation in spring, and births occurring in summer. Males exhibited annual variation of testicular size associated with spermatogenic activity, reaching their maximum gonadal activity in late summer (March), but sperm storage in the epididymis and/or deferent duct occurred throughout the year. Females showed an extended reproductive cycle beginning in mid-autumn (May) with vitellogenesis and finishing with births from late spring to mid-summer (December to February). Litter size varied from 4 to 9 offspring. Females reached sexual maturity at a larger snout-vent length and, overall, showed greater body size than males, while males exhibited larger heads than females. Fat body cycles indicated that females use lipid reserves to support vitellogenesis and embryo development, while males allocate lipid resources to the search for females, courtship and copulation rather than to gametogenesis. Ophiodes intermedius differed from other species of the genus in litter size, gestation period, timing of birth and the minimum size at sexual maturity, probably as a result of the influence of ecological, historical and phylogenetic factors. Copyright © 2017 Elsevier GmbH. All rights reserved.

Lama guanicoe remains from the Chaco ecoregion (Córdoba, Argentina): An osteological approach to the characterization of a relict wild population

PubMed Central

Barri, Fernando

2018-01-01

Guanacos (Lama guanicoe) are large ungulates that have been valued by human populations in South America since the Late Pleistocene. Even though they were very abundant until the end of the 19th century (before the high deforestation rate of the last decades), guanacos have nearly disappeared in the Gran Chaco ecoregion, with relicts and isolated populations surviving in some areas, such as the shrubland area near the saline depressions of Córdoba province, Argentina. In this report, we present the first data from a locally endangered guanaco wild population, through the study of skeletal remains recovered in La Providencia ranch. Our results showed that most of the elements belonged to adults aged between 36 and 96 months; sex evaluation showed similar numbers of males and females. Statistical analysis of the body size of modern samples from Córdoba demonstrated that guanacos from the Chaco had large dimensions and presented lower size variability than the modern and archaeological specimens in our database. Moreover, they exhibited dimensions similar to those of modern guanacos from Patagonia and San Juan, and to archaeological specimens from Ongamira and Cerro Colorado, although further genetic studies are needed to corroborate a possible phylogenetic relationship. Finally, we used archaeozoological techniques to provide a first characterization of a relict guanaco population from the Chaco ecoregion, demonstrating its value to the study of modern skeletal remains and species conservation biology. PMID:29641579

Scaling down of a deworming programme among school-age children after a thirty-year successful intervention in the Bolivian Chaco.

PubMed

Spinicci, Michele; Macchioni, Fabio; Rojo, David; Gamboa, Herlan; Villagrán, Ana Liz; Vallejos, Yolanda; Strohmeyer, Marianne; Roselli, Mimmo; Gabrielli, Simona; Cancrini, Gabriella; Monasterio, Joaquín; Castellanos, Paul; Paredes, Grover Adolfo; Maury, Sdenka; Zárate, Adolfo; Rocabado, Rodolfo; Olliaro, Piero; Montresor, Antonio; Bartoloni, Alessandro

2018-04-16

Preventive chemotherapy is the WHO-recommended control method for soil-transmitted helminthiases. In the Bolivian Chaco, 6-monthly single-dose mebendazole delivery to school-age children achieved a dramatic decrease in soil-transmitted helminthiases prevalence between 1987 and 2013. Consequently, in September 2016, preventive chemotherapy delivery was interrupted in nine rural communities. In compliance with WHO recommendations, we intensified surveillance to monitor soil-transmitted helminthiases prevalence and detect potential changes that would require interventions. We conducted two cross-sectional parasitology surveys 12 months apart (September 2016-2017) among school-age children living in the communities where preventive chemotherapy delivery had been halted. Study design, methods of sampling and sample analysis technique (direct microscopy, Kato-Katz technique) followed WHO recommendations, aiming to obtain data representative of the Bolivian Chaco ecological zone. We collected 426 samples in 2016 and 520 in 2017. Soil-transmitted helminthiasis prevalence was unremarkable: 0.7% (95% CI 0-1.5%) in 2016 and 0.8% (0-1.5%) in 2017. Conversely, the prevalence of tapeworms (13% in 2016, 12% in 2017) and intestinal protozoan infections (81% in 2016 and 75% in 2017) continued to be high. Our findings support the role of preventive chemotherapy in reducing soil-transmitted helminthiases transmission, as otherwise poor hygienic and health conditions persist in the Bolivian Chaco. A national survey, involving areas from all the ecological zones of Bolivia, is now warranted. © 2018 John Wiley & Sons Ltd.

Chagas' disease in Aboriginal and Creole communities from the Gran Chaco Region of Argentina: Seroprevalence and molecular parasitological characterization.

PubMed

Lucero, R H; Brusés, B L; Cura, C I; Formichelli, L B; Juiz, N; Fernández, G J; Bisio, M; Deluca, G D; Besuschio, S; Hernández, D O; Schijman, A G

2016-07-01

Most indigenous ethnias from Northern Argentina live in rural areas of "the Gran Chaco" region, where Trypanosoma cruzi is endemic. Serological and parasitological features have been poorly characterized in Aboriginal populations and scarce information exist regarding relevant T. cruzi discrete typing units (DTU) and parasitic loads. This study was focused to characterize T. cruzi infection in Qom, Mocoit, Pit'laxá and Wichi ethnias (N=604) and Creole communities (N=257) inhabiting rural villages from two highly endemic provinces of the Argentinean Gran Chaco. DNA extracted using Hexadecyltrimethyl Ammonium Bromide reagent from peripheral blood samples was used for conventional PCR targeted to parasite kinetoplastid DNA (kDNA) and identification of DTUs using nuclear genomic markers. In kDNA-PCR positive samples from three rural Aboriginal communities of "Monte Impenetrable Chaqueño", minicircle signatures were characterized by Low stringency single primer-PCR and parasitic loads calculated using Real-Time PCR. Seroprevalence was higher in Aboriginal (47.98%) than in Creole (27.23%) rural communities (Chi square, p=4.e(-8)). A low seroprevalence (4.3%) was detected in a Qom settlement at the suburbs of Resistencia city (Fisher Exact test, p=2.e(-21)).The kDNA-PCR positivity was 42.15% in Aboriginal communities and 65.71% in Creole populations (Chi square, p=5.e(-4)). Among Aboriginal communities kDNA-PCR positivity was heterogeneous (Chi square, p=1.e(-4)). Highest kDNA-PCR positivity (79%) was detected in the Qom community of Colonia Aborigen and the lowest PCR positivity in two different surveys at the Wichi community of Misión Nueva Pompeya (33.3% in 2010 and 20.8% in 2014). TcV (or TcII/V/VI) was predominant in both Aboriginal and Creole communities, in agreement with DTU distribution reported for the region. Besides, two subjects were infected with TcVI, one with TcI and four presented mixed infections of TcV plus TcII/VI. Most minicircle signatures clustered according to their original localities, but in a few cases, signatures from one locality clustered with signatures from other village, suggesting circulation of the same strains in the area. Parasitic loads ranged from undetectable to around 50 parasite equivalents/mL, showing higher values than those generally observed in chronic Chagas disease patients living in urban centers of Argentina. Our findings reveal the persistence of high levels of infection in these neglected populations. Copyright © 2016. Published by Elsevier B.V.

Factors Affecting Infestation by Triatoma infestans in a Rural Area of the Humid Chaco in Argentina: A Multi-Model Inference Approach

PubMed Central

Gurevitz, Juan M.; Ceballos, Leonardo A.; Gaspe, María Sol; Alvarado-Otegui, Julián A.; Enríquez, Gustavo F.; Kitron, Uriel; Gürtler, Ricardo E.

2011-01-01

Background Transmission of Trypanosoma cruzi by Triatoma infestans remains a major public health problem in the Gran Chaco ecoregion, where understanding of the determinants of house infestation is limited. We conducted a cross-sectional study to model factors affecting bug presence and abundance at sites within house compounds in a well-defined rural area in the humid Argentine Chaco. Methodology/Principal Findings Triatoma infestans bugs were found in 45.9% of 327 inhabited house compounds but only in 7.4% of the 2,584 sites inspected systematically on these compounds, even though the last insecticide spraying campaign was conducted 12 years before. Infested sites were significantly aggregated at distances of 0.8–2.5 km. The most frequently infested ecotopes were domiciles, kitchens, storerooms, chicken coops and nests; corrals were rarely infested. Domiciles with mud walls and roofs of thatch or corrugated tarred cardboard were more often infested (32.2%) than domiciles with brick-and-cement walls and corrugated metal-sheet roofs (15.1%). A multi-model inference approach using Akaike's information criterion was applied to assess the relative importance of each variable by running all possible (17,406) models resulting from all combinations of variables. Availability of refuges for bugs, construction with tarred cardboard, and host abundance (humans, dogs, cats, and poultry) per site were positively associated with infestation and abundance, whereas reported insecticide use showed a negative association. Ethnic background (Creole or Toba) adjusted for other factors showed little or no association. Conclusions/Significance Promotion and effective implementation of housing improvement (including key peridomestic structures) combined with appropriate insecticide use and host management practices are needed to eliminate infestations. Fewer refuges are likely to result in fewer residual foci after insecticide spraying, and will facilitate community-based vector surveillance. A more integrated perspective that considers simultaneously social, economic and biological processes at local and regional scales is needed to attain effective, sustainable vector and disease control. PMID:22028941

Factors affecting infestation by Triatoma infestans in a rural area of the humid Chaco in Argentina: a multi-model inference approach.

PubMed

Gurevitz, Juan M; Ceballos, Leonardo A; Gaspe, María Sol; Alvarado-Otegui, Julián A; Enríquez, Gustavo F; Kitron, Uriel; Gürtler, Ricardo E

2011-10-01

Transmission of Trypanosoma cruzi by Triatoma infestans remains a major public health problem in the Gran Chaco ecoregion, where understanding of the determinants of house infestation is limited. We conducted a cross-sectional study to model factors affecting bug presence and abundance at sites within house compounds in a well-defined rural area in the humid Argentine Chaco. Triatoma infestans bugs were found in 45.9% of 327 inhabited house compounds but only in 7.4% of the 2,584 sites inspected systematically on these compounds, even though the last insecticide spraying campaign was conducted 12 years before. Infested sites were significantly aggregated at distances of 0.8-2.5 km. The most frequently infested ecotopes were domiciles, kitchens, storerooms, chicken coops and nests; corrals were rarely infested. Domiciles with mud walls and roofs of thatch or corrugated tarred cardboard were more often infested (32.2%) than domiciles with brick-and-cement walls and corrugated metal-sheet roofs (15.1%). A multi-model inference approach using Akaike's information criterion was applied to assess the relative importance of each variable by running all possible (17,406) models resulting from all combinations of variables. Availability of refuges for bugs, construction with tarred cardboard, and host abundance (humans, dogs, cats, and poultry) per site were positively associated with infestation and abundance, whereas reported insecticide use showed a negative association. Ethnic background (Creole or Toba) adjusted for other factors showed little or no association. Promotion and effective implementation of housing improvement (including key peridomestic structures) combined with appropriate insecticide use and host management practices are needed to eliminate infestations. Fewer refuges are likely to result in fewer residual foci after insecticide spraying, and will facilitate community-based vector surveillance. A more integrated perspective that considers simultaneously social, economic and biological processes at local and regional scales is needed to attain effective, sustainable vector and disease control.

Soil Moisture and Excavation Behaviour in the Chaco Leaf-Cutting Ant (Atta vollenweideri): Digging Performance and Prevention of Water Inflow into the Nest

PubMed Central

Pielström, Steffen; Roces, Flavio

2014-01-01

The Chaco leaf-cutting ant Atta vollenweideri is native to the clay-heavy soils of the Gran Chaco region in South America. Because of seasonal floods, colonies are regularly exposed to varying moisture across the soil profile, a factor that not only strongly influences workers' digging performance during nest building, but also determines the suitability of the soil for the rearing of the colony's symbiotic fungus. In this study, we investigated the effects of varying soil moisture on behaviours associated with underground nest building in A. vollenweideri. This was done in a series of laboratory experiments using standardised, plastic clay-water mixtures with gravimetric water contents ranging from relatively brittle material to mixtures close to the liquid limit. Our experiments showed that preference and group-level digging rate increased with increasing water content, but then dropped considerably for extremely moist materials. The production of vibrational recruitment signals during digging showed, on the contrary, a slightly negative linear correlation with soil moisture. Workers formed and carried clay pellets at higher rates in moist clay, even at the highest water content tested. Hence, their weak preference and low group-level excavation rate observed for that mixture cannot be explained by any inability to work with the material. More likely, extremely high moistures may indicate locations unsuitable for nest building. To test this hypothesis, we simulated a situation in which workers excavated an upward tunnel below accumulated surface water. The ants stopped digging about 12 mm below the interface soil/water, a behaviour representing a possible adaptation to the threat of water inflow field colonies are exposed to while digging under seasonally flooded soils. Possible roles of soil water in the temporal and spatial pattern of nest growth are discussed. PMID:24748382

Hidden Sylvatic Foci of the Main Vector of Chagas Disease Triatoma infestans: Threats to the Vector Elimination Campaign?

PubMed Central

Schachter-Broide, Judith; Dujardin, Jean-Pierre; Dotson, Ellen M.; Kitron, Uriel; Gürtler, Ricardo E.

2011-01-01

Background Establishing the sources of reinfestation after residual insecticide spraying is crucial for vector elimination programs. Triatoma infestans, traditionally considered to be limited to domestic or peridomestic (abbreviated as D/PD) habitats throughout most of its range, is the target of an elimination program that has achieved limited success in the Gran Chaco region in South America. Methodology/Principal Findings During a two-year period we conducted semi-annual searches for triatomine bugs in every D/PD site and surrounding sylvatic habitats after full-coverage spraying of pyrethroid insecticides of all houses in a well-defined rural area in northwestern Argentina. We found six low-density sylvatic foci with 24 T. infestans in fallen or standing trees located 110–2,300 m from the nearest house or infested D/PD site detected after insecticide spraying, when house infestations were rare. Analysis of two mitochondrial gene fragments of 20 sylvatic specimens confirmed their species identity as T. infestans and showed that their composite haplotypes were the same as or closely related to D/PD haplotypes. Population studies with 10 polymorphic microsatellite loci and wing geometric morphometry consistently indicated the occurrence of unrestricted gene flow between local D/PD and sylvatic populations. Mitochondrial DNA and microsatellite sibship analyses in the most abundant sylvatic colony revealed descendents from five different females. Spatial analysis showed a significant association between two sylvatic foci and the nearest D/PD bug population found before insecticide spraying. Conclusions Our study shows that, despite of its high degree of domesticity, T. infestans has sylvatic colonies with normal chromatic characters (not melanic morphs) highly connected to D/PD conspecifics in the Argentinean Chaco. Sylvatic habitats may provide a transient or permanent refuge after control interventions, and function as sources for D/PD reinfestation. The occurrence of sylvatic foci of T. infestans in the Gran Chaco may pose additional threats to ongoing vector elimination efforts. PMID:22039559

Changes in Species Richness and Composition of Tiger Moths (Lepidoptera: Erebidae: Arctiinae) among Three Neotropical Ecoregions.

PubMed

Beccacece, Hernán Mario; Zeballos, Sebastián Rodolfo; Zapata, Adriana Inés

Paraná, Yungas and Chaco Serrano ecoregions are among the most species-rich terrestrial habitats at higher latitude. However, the information for tiger moths, one of the most speciose groups of moths, is unknown in these ecoregions. In this study, we assess their species richness and composition in all three of these ecoregions. Also we investigated whether the species composition of tiger moths is influenced by climatic factors and altitude. Tiger moth species were obtained with samples from 71 sites using standardized protocols (21 sites were in Yungas, 19 in Paraná and 31 in Chaco Serrano). Rarefaction-extrapolation curves, non-parametric estimators for incidence and sample coverage indices were performed to assess species richness in the ecoregions studied. Non metric multidimensional scaling and adonis tests were performed to compare the species composition of tiger moths among ecoregions. Permutest analysis and Pearson correlation were used to evaluate the relationship among species composition and annual mean temperature, annual temperature range, annual precipitation, precipitation seasonality and altitude. Among ecoregions Paraná was the richest with 125 species, followed by Yungas with 63 species and Chaco Serrano with 24 species. Species composition differed among these ecoregions, although Yungas and Chaco Serrano were more similar than Paraná. Species composition was significantly influenced by climatic factors and altitude. This study showed that species richness and species composition of tiger moths differed among the three ecoregions assessed. Furthermore, not only climatic factors and altitude influence the species composition of tiger moths among ecoregions, but also climatic seasonality at higher latitude in Neotropical South America becomes an important factor.

Near Real Time Change-Point detection in Optical and Thermal Infrared Time Series Using Bayesian Inference over the Dry Chaco Forest

NASA Astrophysics Data System (ADS)

Barraza Bernadas, V.; Grings, F.; Roitberg, E.; Perna, P.; Karszenbaum, H.

2017-12-01

The Dry Chaco region (DCF) has the highest absolute deforestation rates of all Argentinian forests. The most recent report indicates a current deforestation rate of 200,000 Ha year-1. In order to better monitor this process, DCF was chosen to implement an early warning program for illegal deforestation. Although the area is intensively studied using medium resolution imagery (Landsat), the products obtained have a yearly pace and therefore unsuited for an early warning program. In this paper, we evaluated the performance of an online Bayesian change-point detection algorithm for MODIS Enhanced Vegetation Index (EVI) and Land Surface Temperature (LST) datasets. The goal was to to monitor the abrupt changes in vegetation dynamics associated with deforestation events. We tested this model by simulating 16-day EVI and 8-day LST time series with varying amounts of seasonality, noise, length of the time series and by adding abrupt changes with different magnitudes. This model was then tested on real satellite time series available through the Google Earth Engine, over a pilot area in DCF, where deforestation was common in the 2004-2016 period. A comparison with yearly benchmark products based on Landsat images is also presented (REDAF dataset). The results shows the advantages of using an automatic model to detect a changepoint in the time series than using only visual inspection techniques. Simulating time series with varying amounts of seasonality and noise, and by adding abrupt changes at different times and magnitudes, revealed that this model is robust against noise, and is not influenced by changes in amplitude of the seasonal component. Furthermore, the results compared favorably with REDAF dataset (near 65% of agreement). These results show the potential to combine LST and EVI to identify deforestation events. This work is being developed within the frame of the national Forest Law for the protection and sustainable development of Native Forest in Argentina in agreement with international legislation (REDD+).

Deforestation impacts on soil organic carbon stocks in the Semiarid Chaco Region, Argentina.

PubMed

Villarino, Sebastián Horacio; Studdert, Guillermo Alberto; Baldassini, Pablo; Cendoya, María Gabriela; Ciuffoli, Lucía; Mastrángelo, Matias; Piñeiro, Gervasio

2017-01-01

Land use change affects soil organic carbon (SOC) and generates CO 2 emissions. Moreover, SOC depletion entails degradation of soil functions that support ecosystem services. Large areas covered by dry forests have been cleared in the Semiarid Chaco Region of Argentina for cropping expansion. However, deforestation impacts on the SOC stock and its distribution in the soil profile have been scarcely reported. We assessed these impacts based on the analysis of field data along a time-since-deforestation-for-cropping chronosequence, and remote sensing indices. Soil organic C was determined up to 100cm depth and physically fractionated into mineral associated organic carbon (MAOC) and particulate organic C (POC). Models describing vertical distribution of SOC were fitted. Total SOC, POC and MAOC stocks decreased markedly with increasing cropping age. Particulate organic C was the most sensitive fraction to cultivation. After 10yr of cropping SOC loss was around 30%, with greater POC loss (near 60%) and smaller MAOC loss (near 15%), at 0-30cm depth. Similar relative SOC losses were observed in deeper soil layers (30-60 and 60-100cm). Deforestation and subsequent cropping also modified SOC vertical distribution. Soil organic C loss was negatively associated with the proportion of maize in the rotation and total crop biomass inputs, but positively associated with the proportion of soybean in the rotation. Without effective land use polices, deforestation and agricultural expansion can lead to rapid soil degradation and reductions in the provision of important ecosystem services. Copyright © 2016 Elsevier B.V. All rights reserved.

Seasonal dynamics, geographical range size, hosts, genetic diversity and phylogeography of Amblyomma sculptum in Argentina.

PubMed

Tarragona, Evelina L; Sebastian, Patrick S; Saracho Bottero, María N; Martinez, Emilia I; Debárbora, Valeria N; Mangold, Atilio J; Guglielmone, Alberto A; Nava, Santiago

2018-04-27

The aim of this work was to generate knowledge on ecological aspects of Amblyomma sculptum in Argentina, such as seasonal dynamics, geographical range size, hosts, genetic diversity and phylogeography. Adult and immature A. sculptum ticks were collected in different localities of Argentina to know the geographical range size and hosts. The genetic diversity of this tick was studied through analyses of 16S rDNA sequences. To describe the seasonal dynamics, free-living ticks were monthly collected from October 2013 to October 2015. A. sculptum shows a marked ecological preference for Chaco Húmedo eco-region and "Albardones" forest of the great rivers in the wetlands in the Chaco Biogeographical Province, and for Selvas Pedemontanas and Selva Montana in the Yungas Biogeographical Province. This species has low host specificity, and it has large wild and domestic mammals as principal hosts to both immature and adult stages. Amblyomma sculptum is characterized by a one-year life cycle. Larvae peak in early winter, nymphs peaked during mid-spring, and adults during late summer and mid-summer. The genetic divergence was low and the total genetic variability was attributable to differences among populations. This fact could be associated to stochastics process linked to micro-habitat variations that could produce a partial restriction to gene flow among populations. The geographic regions do not contribute much to explain the A. sculptum population genetic structure, with an ancestral haplotype present in most populations, which gives rise to the rest of the haplotypes denoting a rapid population expansion. Copyright © 2018. Published by Elsevier GmbH.

Knowledge, attitudes, and practices towards epilepsy among general practitioners in rural Bolivia: Results before and after a training program on epilepsy.

PubMed

Giuliano, Loretta; Cicero, Calogero Edoardo; Padilla, Sandra; Camargo, Mario; Sofia, Vito; Zappia, Mario; Bartoloni, Alessandro; Crespo Gómez, Elizabeth Blanca; Nicoletti, Alessandra

2018-04-22

Epilepsy represents a major health problem in low- and middle-income countries where treatment gap (TG) levels are high. The reduction of epilepsy TG in the rural area of the Chaco region, Plurinational State of Bolivia, has been the aim of many projects based on the reinforcement of the primary care setting. To plan educational campaigns directed to the healthcare professionals, it is necessary to establish their baseline knowledge level. The objective of our study was to assess the baseline level of knowledge, attitudes, and practices (KAP) towards epilepsy among general practitioners (GPs) of the rural communities of the Chaco region. The study was conducted in three departments of Bolivia. All the GPs living in these areas were invited to participate in the study consisting of two training modules six months apart from each other, each with two-day duration. They answered a validated questionnaire to evaluate the KAP towards epilepsy before and after the courses. Fifty GPs [30 men (60%); mean age: 32.1±5.8years] participated in the first training course. After six months, 31 GPs (62%) [19 men (61.3%); mean age: 33±5.0years] participated in the second module. Before the training, the majority of GPs declared a low level of satisfaction about their epilepsy knowledge, which improved after the courses. A change in practices was recorded after the training, with an increased confidence to manage antiepileptic treatment. Our study showed the significant impact of specific training programs on epilepsy among GPs. Copyright © 2017 Elsevier Inc. All rights reserved.

Impact of community-based vector control on house infestation and Trypanosoma cruzi infection in Triatoma infestans, dogs and cats in the Argentine Chaco.

PubMed

Cardinal, M V; Lauricella, M A; Marcet, P L; Orozco, M M; Kitron, U; Gürtler, R E

2007-09-01

The relative impact of two community-based vector control strategies on house infestation by Triatoma infestans and Trypanosoma cruzi infection in bugs, domestic dogs and cats was assessed in two neighboring rural areas comprising 40 small villages and 323 houses in one of the regions most endemic for Chagas disease in northern Argentina. The prevalence and abundance of domestic infestation were 1.5- and 6.5-fold higher, respectively, in the area under pulsed, non-supervised control actions operating under the guidelines of the National Vector Control Program (NCVP) than in the area under sustained, supervised surveillance carried out jointly by the UBA research team and NCVP. The prevalence of infestation and infection varied widely among village groups within each area. In the pulsed control area, the prevalence of infection in bugs, dogs and cats was two- to three-fold higher than in the area under sustained surveillance, most of the infected animals qualified as autochthonous cases, and evidence of recent transmission was observed. Infection was highly aggregated at the household level and fell close to the 80/20 rule. Using multiple logistic regression analysis clustered by household, infection in dogs was associated positively and significantly with variables reflecting local exposure to infected T. infestans, thus demonstrating weak performance of the vector surveillance system. For high-risk areas in the Gran Chaco region, interruption of vector-mediated domestic transmission of T. cruzi requires residual insecticide spraying that is more intense, of a higher quality and sustained in time, combined with community participation and environmental management measures.

Mitochondrial lineage A2ah found in a pre-Hispanic individual from the Andean region.

PubMed

Russo, M G; Dejean, C B; Avena, S A; Seldes, V; Ramundo, P

2018-05-10

The aim of this study was to contribute to the knowledge of pre-Hispanic Andean mitochondrial diversity by analyzing an individual from the archaeological site Pukara de La Cueva (North-western Argentina). The date of the discovery context (540 ± 60 BP) corresponds to the Regional Developments II period. Two separate DNA extractions were performed from dentin powder of one tooth. HVR I was amplified by PCR from each extract in three overlapping fragments and the haplotype was determined by consensus among all obtained sequences. The procedures were carried out under strict protocols developed for working with ancient DNA. The individual belonged to the A2ah lineage due to the presence of the 16097C and 16098G transitions, which constitute its distinctive motif. This lineage is very rare in Native American populations and was described in four individuals from current groups inhabiting the Bolivian Llanos, two from South-eastern Brazil, and one from the Gran Chaco region. In addition, two other mutations (16260T and 16286T) were shared with one of the individuals from the Bolivian Llanos region. Considering that the origin of this lineage was postulated for the South American lowlands, the present pre-Hispanic discovery in the Andean area could be taken as a new evidence of gene flow between these regions. Also, it allows the questioning of the geographical origin of this mitochondrial lineage. © 2018 Wiley Periodicals, Inc.

Changes in Species Richness and Composition of Tiger Moths (Lepidoptera: Erebidae: Arctiinae) among Three Neotropical Ecoregions

PubMed Central

Beccacece, Hernán Mario; Zeballos, Sebastián Rodolfo; Zapata, Adriana Inés

2016-01-01

Paraná, Yungas and Chaco Serrano ecoregions are among the most species-rich terrestrial habitats at higher latitude. However, the information for tiger moths, one of the most speciose groups of moths, is unknown in these ecoregions. In this study, we assess their species richness and composition in all three of these ecoregions. Also we investigated whether the species composition of tiger moths is influenced by climatic factors and altitude. Tiger moth species were obtained with samples from 71 sites using standardized protocols (21 sites were in Yungas, 19 in Paraná and 31 in Chaco Serrano). Rarefaction-extrapolation curves, non-parametric estimators for incidence and sample coverage indices were performed to assess species richness in the ecoregions studied. Non metric multidimensional scaling and adonis tests were performed to compare the species composition of tiger moths among ecoregions. Permutest analysis and Pearson correlation were used to evaluate the relationship among species composition and annual mean temperature, annual temperature range, annual precipitation, precipitation seasonality and altitude. Among ecoregions Paraná was the richest with 125 species, followed by Yungas with 63 species and Chaco Serrano with 24 species. Species composition differed among these ecoregions, although Yungas and Chaco Serrano were more similar than Paraná. Species composition was significantly influenced by climatic factors and altitude. This study showed that species richness and species composition of tiger moths differed among the three ecoregions assessed. Furthermore, not only climatic factors and altitude influence the species composition of tiger moths among ecoregions, but also climatic seasonality at higher latitude in Neotropical South America becomes an important factor. PMID:27681478

Carbon emissions from agricultural expansion and intensification in the Chaco.

PubMed

Baumann, Matthias; Gasparri, Ignacio; Piquer-Rodríguez, María; Gavier Pizarro, Gregorio; Griffiths, Patrick; Hostert, Patrick; Kuemmerle, Tobias

2017-05-01

Carbon emissions from land-use changes in tropical dry forest systems are poorly understood, although they are likely globally significant. The South American Chaco has recently emerged as a hot spot of agricultural expansion and intensification, as cattle ranching and soybean cultivation expand into forests, and as soybean cultivation replaces grazing lands. Still, our knowledge of the rates and spatial patterns of these land-use changes and how they affected carbon emissions remains partial. We used the Landsat satellite image archive to reconstruct land-use change over the past 30 years and applied a carbon bookkeeping model to quantify how these changes affected carbon budgets. Between 1985 and 2013, more than 142 000 km 2 of the Chaco's forests, equaling 20% of all forest, was replaced by croplands (38.9%) or grazing lands (61.1%). Of those grazing lands that existed in 1985, about 40% were subsequently converted to cropland. These land-use changes resulted in substantial carbon emissions, totaling 824 Tg C between 1985 and 2013, and 46.2 Tg C for 2013 alone. The majority of these emissions came from forest-to-grazing-land conversions (68%), but post-deforestation land-use change triggered an additional 52.6 Tg C. Although tropical dry forests are less carbon-dense than moist tropical forests, carbon emissions from land-use change in the Chaco were similar in magnitude to those from other major tropical deforestation frontiers. Our study thus highlights the urgent need for an improved monitoring of the often overlooked tropical dry forests and savannas, and more broadly speaking the value of the Landsat image archive for quantifying carbon fluxes from land change. © 2016 John Wiley & Sons Ltd.

First Finding of Melanic Sylvatic Triatoma infestans (Hemiptera: Reduviidae) Colonies in the Argentine Chaco

PubMed Central

CEBALLOS, L. A.; PICCINALI, R. V.; BERKUNSKY, I.; KITRON, U.; GÜRTLER, R. E.

2009-01-01

Triatoma infestans (Klug), the most important vector of Chagas disease in southern South America, is a highly domiciliated species with well-known sylvatic foci only in the Bolivian Andean valleys and in the Bolivian Chaco, where melanic insects designated as “dark morphs” were found. After the tentative identification of two melanic bugs collected from parrot nests in a forest reserve in the Argentine Chaco as T. infestans, we conducted an intensive search there using mouse-baited sticky traps in summer 2006 and 2007. Four live T. infestans bugs were collected in trees without parrot nests in 288 trap-nights, whereas no bug was collected from inside trees with active parrot nests in 51 trap-nights. To increase bug captures, hollow tree trunks that recently had had Amazona aestiva (Berlepsch) and Aratinga acuticaudata (Vieillot) parrot nests were treated with insecticide fumigant canisters exhibiting strong knockdown power. Four (22%) of 18 trees were positive for T. infestans with a dark phenotype. A fragment of the mitochondrial gene COI of 8 of the 14 triatomine bugs collected was successfully sequenced and confirmed as T. infestans. Most of the bugs were captured from Aspidosperma quebracho-blanco (Schlechter) hollow tree trunks harboring parrot nests. All of the T. infestans collected from the nearest house located at 10 km from the sylvatic foci displayed normal chromatic characters. The repeated finding of T. infestans in sylvatic habitats, albeit at very low density, shows that this species is capable of maintaining viable sylvatic foci in the absence of human hosts and immigration from domestic populations. These are the first confirmed findings of sylvatic T. infestans colonies in Argentina and of dark morphs in the Argentine Chaco. PMID:19769054

Reduced population variance in strontium isotope values informs domesticated turkey use at Chaco Canyon, New Mexico, USA

USGS Publications Warehouse

Grimstead, Deanna N; Reynolds, Amanda C; Hudson, Adam M; Akins, Nancy J; Betancourt, Julio L.

2016-01-01

Traditionally strontium isotopes (87Sr/86Sr) have been used as a sourcing tool in numerous archaeological artifact classes. The research presented here demonstrates that 87Sr/86Srbioapatite ratios also can be used at a population level to investigate the presence of domesticated animals and methods of management. The proposed methodology combines ecology, isotope geochemistry, and behavioral ecology to assess the presence and nature of turkey (Meleagris gallopavo) domestication. This case study utilizes 87Sr/86Srbioapatite ratios from teeth and bones of archaeological turkey, deer (Odocoileus sp.), lagomorph (Lepus sp. and Sylvilagus sp.), and prairie-dog (Cynomys sp.) from Chaco Canyon, New Mexico, U.S.A. (ca. A.D. 800 – 1250). Wild deer and turkey from the southwestern U.S.A. have much larger home ranges and dispersal behaviors (measured in kilometers) when compared to lagomorphs and prairie dogs (measured in meters). Hunted deer and wild turkey from archaeological contexts at Chaco Canyon are expected to have a higher variance in their 87Sr/86Srbioapatite ratios, when compared to small range taxa (lagomorphs and prairie dogs). Contrary to this expectation, 87Sr/86Srbioapatite values of turkey bones from Chacoan assemblages have a much lower variance than deer and are similar to that of smaller mammals. The sampled turkey values show variability most similar to lagomorphs and prairie dogs, suggesting the turkeys from Chaco Canyon were consuming a uniform diet and/or were constrained within a limited home range, indicating at least proto-domestication. The population approach has wide applicability for evaluating the presence and nature of domestication when combined with paleoecology and behavioral ecology in a variety of animals and environments.

Differences in production, carbon stocks and biodiversity outcomes of land tenure regimes in the Argentine Dry Chaco

NASA Astrophysics Data System (ADS)

Marinaro, Sofía; Grau, H. Ricardo; Gasparri, Néstor Ignacio; Kuemmerle, Tobias; Baumann, Matthias

2017-04-01

Rising global demand for agricultural products results in agricultural expansion and intensification, with substantial environmental trade-offs. The South American Dry Chaco contains some of the fastest expanding agricultural frontiers worldwide, and includes diverse forms of land management, mainly associated with different land tenure regimes; which in turn are segregated along environmental gradients (mostly rainfall). Yet, how these regimes impact the environment and how trade-offs between production and environmental outcomes varies remains poorly understood. Here, we assessed how biodiversity, biomass stocks, and agricultural production, measured in meat-equivalents, differ among land tenure regimes in the Dry Chaco. We calculated a land-use outcome index (LUO) that combines indices comparing actual vs. potential values of ‘preservation of biodiversity’ (PI), ‘standing biomass’ (BI) and ‘meat production’ (MI). We found land-use outcomes to vary substantially among land-tenure regimes. Protected areas showed a biodiversity index of 0.75, similar to that of large and medium-sized farms (0.72 in both farming systems), and higher than in the other tenure regimes. Biomass index was similar among land tenure regimes, whereas we found the highest median meat production index on indigenous lands (MI = 0.35). Land-use outcomes, however, varied more across different environmental conditions than across land tenure regimes. Our results suggest that in the Argentine Dry Chaco, there is no single land tenure regime that better minimizes the trade-offs between production and environmental outcomes. A useful approach to manage these trade-offs would be to develop geographically explicit guidelines for land-use zoning, identifying the land tenure regimes more appropriate for each zone.

New discoveries of sylvatic Triatoma infestans (Hemiptera: Reduviidae) throughout the Bolivian Chaco.

PubMed

Waleckx, Etienne; Depickère, Stéphanie; Salas, Renata; Aliaga, Claudia; Monje, Marcelo; Calle, Hiber; Buitrago, Rosio; Noireau, François; Brenière, Simone Frédérique

2012-03-01

Sylvatic populations of Triatoma infestans might be involved in the recolonization of human dwellings. We report here the discoveries of new T. infestans sylvatic foci in the Bolivian Chaco. Eighty-one triatomines were caught, 38 of which were identified as T. infestans. Triatoma sordida and Panstrongylus geniculatus were the other species collected. One T. infestans and one T. sordida were infected with Trypanosoma cruzi TcI; one T. infestans was infected with TcII. These discoveries add to the debate on the geographic distribution of sylvatic T. infestans populations, the geographic origin of the species, and the epidemiological role of these populations.

New Discoveries of Sylvatic Triatoma infestans (Hemiptera: Reduviidae) Throughout the Bolivian Chaco

PubMed Central

Waleckx, Etienne; Depickère, Stéphanie; Salas, Renata; Aliaga, Claudia; Monje, Marcelo; Calle, Hiber; Buitrago, Rosio; Noireau, François; Brenière, Simone Frédérique

2012-01-01

Sylvatic populations of Triatoma infestans might be involved in the recolonization of human dwellings. We report here the discoveries of new T. infestans sylvatic foci in the Bolivian Chaco. Eighty-one triatomines were caught, 38 of which were identified as T. infestans. Triatoma sordida and Panstrongylus geniculatus were the other species collected. One T. infestans and one T. sordida were infected with Trypanosoma cruzi TcI; one T. infestans was infected with TcII. These discoveries add to the debate on the geographic distribution of sylvatic T. infestans populations, the geographic origin of the species, and the epidemiological role of these populations. PMID:22403316

Archeological Surveys

NASA Technical Reports Server (NTRS)

1978-01-01

NASA remote sensing technology is being employed in archeological studies of the Anasazi Indians, who lived in New Mexico one thousand years ago. Under contract with the National Park Service, NASA's Technology Applications Center at the University of New Mexico is interpreting multispectral scanner data and demonstrating how aerospace scanning techniques can uncover features of prehistoric ruins not visible in conventional aerial photographs. The Center's initial study focused on Chaco Canyon, a pre-Columbia Anasazi site in northeastern New Mexico. Chaco Canyon is a national monument and it has been well explored on the ground and by aerial photography. But the National Park Service was interested in the potential of multispectral scanning for producing evidence of prehistoric roads, field patterns and dwelling areas not discernible in aerial photographs. The multispectral scanner produces imaging data in the invisible as well as the visible portions of the spectrum. This data is converted to pictures which bring out features not visible to the naked eye or to cameras. The Technology Applications Center joined forces with Bendix Aerospace Systems Division, Ann Arbor, Michigan, which provided a scanner-equipped airplane for mapping the Chaco Canyon area. The NASA group processed the scanner images and employed computerized image enhancement techniques to bring out additional detail.

Toward linking maize chemistry to archaeological agricultural sites in the North American Southwest

USGS Publications Warehouse

Cordell, L.S.; Durand, S.R.; Antweiler, Ronald C.; Taylor, Howard E.

2001-01-01

Maize (Zea mays L.) was the staple domestic food crop for Ancestral Pueblo people throughout the northern American Southwest. It is thought to have been the basic food of the inhabitants of Chaco Canyon. New Mexico, a location that was a major centre of Ancestral Pueblo building and population during the 11th and early 12th centuries AD. Modern heirloom varieties of Native American corn have been difficult to grow in experimental fields in Chaco Canyon. Given an abundance of apparent storage structures in Chacoan buildings, it is possible that some corn recovered from archaeological contexts, was imported from surrounding areas. The ultimate goal of this research is to determine whether the corn in Chaco Canyon was grown locally or imported. This paper establishes the feasibility of a method to accomplish this goal. This study reports the results of using inductively coupled plasma-mass spectrometric (ICP-MS) instrumentation to determine chemical constituents of experimental fields and modern heirloom varieties of Native American corn. Analysis of 19 elements is adequate to differentiate soil and corn from three field areas. These results are promising: however, a number of problems, including post-depositional alterations in maize, remain to be solved. ?? 2001 Academic Press.

Development and application of methods used to source prehistoric Southwestern maize: a review

USGS Publications Warehouse

Benson, Larry V.

2012-01-01

Archaeological cobs free of mineral contaminants should be used to source the soils in which they were grown. Mineral contaminants often contain much higher concentrations of metals than vegetal materials and can alter a cob’s apparent metal and heavy-isotope content. Cleaning a cob via immersion in an acid solution for more than a few minutes will result in the incongruent and sometimes complete leaching of metals, including strontium (Sr), from the cob. When using 87Sr/Sr to determine the location of potential agriculture fields, it is best to either integrate several depth-integrated soil samples or to integrate several vegetation samples from individual fields. Biologically labile Sr in semi-arid Southwestern soils largely originates from eolian source or sources and usually is not derived from underlying bedrock. Existing Sr-isotope data indicate that archaeological cobs from Aztec Ruins came from either the Mesa Verde-McElmo Dome or Totah areas, that Pueblo Bonito and Chetro Ketl cobs, from Chaco Canyon that predate A.D. 1130, probably came from the Rio Chaco corridor, and that cobs from Chaco Canyon, that postdate A.D. 1130, probably came from either the Totah or Zuni areas.

Over Six Thousand Trypanosoma cruzi Strains Classified into Discrete Typing Units (DTUs): Attempt at an Inventory

PubMed Central

Brenière, Simone Frédérique; Waleckx, Etienne; Barnabé, Christian

2016-01-01

Trypanosoma cruzi, the causative agent of Chagas disease, presents wide genetic diversity. Currently, six discrete typing units (DTUs), named TcI to TcVI, and a seventh one called TcBat are used for strain typing. Beyond the debate concerning this classification, this systematic review has attempted to provide an inventory by compiling the results of 137 articles that have used it. A total of 6,343 DTU identifications were analyzed according to the geographical and host origins. Ninety-one percent of the data available is linked to South America. This sample, although not free of potential bias, nevertheless provides today’s picture of T. cruzi genetic diversity that is closest to reality. DTUs were genotyped from 158 species, including 42 vector species. Remarkably, TcI predominated in the overall sample (around 60%), in both sylvatic and domestic cycles. This DTU known to present a high genetic diversity, is very widely distributed geographically, compatible with a long-term evolution. The marsupial is thought to be its most ancestral host and the Gran Chaco region the place of its putative origin. TcII was rarely sampled (9.6%), absent, or extremely rare in North and Central America, and more frequently identified in domestic cycles than in sylvatic cycles. It has a low genetic diversity and has probably found refuge in some mammal species. It is thought to originate in the south-Amazon area. TcIII and TcIV were also rarely sampled. They showed substantial genetic diversity and are thought to be composed of possible polyphyletic subgroups. Even if they are mostly associated with sylvatic transmission cycles, a total of 150 human infections with these DTUs have been reported. TcV and TcVI are clearly associated with domestic transmission cycles. Less than 10% of these DTUs were identified together in sylvatic hosts. They are thought to originate in the Gran Chaco region, where they are predominant and where putative parents exist (TcII and TcIII). Trends in host-DTU specificities exist, but generally it seems that the complexity of the cycles and the participation of numerous vectors and mammal hosts in a shared area, maintains DTU diversity. PMID:27571035

Diversification and biogeography of the Neotropical caviomorph lineage Octodontoidea (Rodentia: Hystricognathi).

PubMed

Upham, Nathan S; Patterson, Bruce D

2012-05-01

The rodent superfamily Octodontoidea comprises 6 families, 38 genera, and 193 living species of spiny rats, tuco-tucos, degus, hutias, and their relatives. All are endemic to the Neotropical Region where they represent roughly three-quarters of extant caviomorphs. Although caviomorph monophyly is well established and phylogenetic hypotheses exist for several families, understanding of octodontoid relationships is clouded by sparse taxon sampling and single-gene analyses. We examined sequence variation in one mitochondrial (12S rRNA) and three nuclear genes (vWF, GHR, and RAG1) across all caviomorph families (including 47 octodontoid species), all phiomorph families, and the sole remaining hystricognath family, using the gundi (Ctenodactylus) and springhaas (Pedetes) as outgroups. Our analyses support the monophyly of Phiomorpha, Caviomorpha, and the caviomorph superfamilies Cavioidea (Dasyproctidae, Cuniculidae, and Caviidae, the latter including Hydrochoerus), Erethizontoidea, Chinchilloidea (including Dinomyidae), and Octodontoidea. Cavioids and erethizontoids are strongly supported as sisters, whereas chinchilloids appear to be sister to octodontoids. Among octodontoids, Abrocomidae is consistently recovered as the basal element, sister to a pair of strongly supported clades; one includes Octodontidae and Ctenomyidae as reciprocally monophyletic lineages, whereas the other includes taxa currently allocated to Echimyidae, Capromyidae and Myocastoridae. Capromys appears near the base of this clade, in keeping with current classification, but Myocastor is nested securely inside a clade of Echimyidae that also contains eumysopines, echimyines and dactylomyines. Another, more weakly supported clade of Echimyidae contains fossorial and scansorial taxa from the Chaco-Cerrado-Caatinga and the Atlantic Forest. Biogeographic analyses robustly recover the Patagonia-Southern Andes complex as ancestral for the Octodontoidea, with three component lineages emerging by the Oligocene-Miocene boundary (∼23Ma): (1) stem abrocomids in the Central and Southern Andes; (2) a lineage leading to octodontids plus ctenomyids in Patagonia, later dispersing into the Chaco-Cerrado-Caatinga; and (3) a lineage leading to echimyids, capromyids, and myocastorids that subsequently radiated in more mesic biomes, including Amazonia, Atlantic Forest, and the Antilles. This reconstruction refutes earlier ideas that the diverse, generalized, mainly lowland family Echimyidae, which appears early in the fossil record, gave rise to the Andean lineages of octodontoids-instead, the reverse derivation appears to be true. We recommend formal synonymy of Myocastoridae with Echimyidae but defer a similar treatment of Capromyidae until additional hutia taxa and sequences can be analyzed. Copyright © 2012 Elsevier Inc. All rights reserved.

Provenance and fate of arsenic and other solutes in the Chaco-Pampean Plain of the Andean foreland, Argentina: From perspectives of hydrogeochemical modeling and regional tectonic setting

NASA Astrophysics Data System (ADS)

Raychowdhury, Nilasree; Mukherjee, Abhijit; Bhattacharya, Prosun; Johannesson, Karen; Bundschuh, Jochen; Sifuentes, Gabriela Bejarano; Nordberg, Erika; Martin, Raúl A.; Storniolo, Angel del Rosario

2014-10-01

Extensive arsenic (As) enriched groundwater is known to occur in the aquifers of the Chaco-Pampean Plain of Argentina. Previous studies speculated that the As mobilization in these groundwaters was a direct result of their elevated pH and oxidative conditions. The volcanic glass layers present in the aquifer matrix were hypothesized as one of the possible sources of As to the groundwaters. Here, we examine the groundwater chemistry of the Santiago del Estero province of Chaco-Pampean Plains of Argentina, and test these hypotheses by using hydrogeochemical modeling within the framework of the regional geologic-tectonic setting. The study area is located in the active foreland of the Andean orogenic belt, which forms a continental arc setting, and is dotted with several hot springs. Rhyolitic volcanic glass fragments derived from arc volcanism are abundant within the aeolian-fluvial aquifer sediments, and are related to the paleo-igneous extrusion in the vicinity. Hydrogeochemical analyses show that the groundwater is in predominantly oxidative condition. In addition, some of the groundwaters exhibit very high Na, Cl- and SO42- concentrations. It is hypothesized in this study that the groundwater chemistry has largely evolved by dissolution of rhyolitic volcanic glass fragments contained within the aquifer sediments along with mixing with saline surface waters from, adjoining salinas, which are thought to be partially evaporated remnants of a paleo inland sea. Flow path modeling, stability diagrams, and thermodynamic analyses undertaken in this study indicate that the dominant evolutionary processes include ion exchange reactions, chemical weathering of silicate and evaporites, in monosialitization-dominated weathering. Geochemical modeling predicts that plagioclase feldspar and volcanic glass are the major solids phases that contribute metal cations and dissolved silica to the local groundwaters. Co-influxed oxyanions, with similar ionic radii and structure (e.g. Mo, Si, V, PO43-), compete with As for mineral surface site, leading to As mobilization to the groundwaters (without considering the influence of microbial activities). Further, the transition of the Ca-rich groundwater to Na-rich groundwater, by mixing with water from the salinas and/or evaporative concentration, might also have led to counter-ion effects (a type of ion exchange reactions), and hence, further enrichment of groundwater by As. Some of the As may also have been contributed from mixing of meteoric water with magmatic-sourced water in the geothermal springs.

Natural contamination with arsenic and other trace elements in groundwater of the Central-West region of Chaco, Argentina.

PubMed

Blanes, Patricia S; Buchhamer, Edgar E; Giménez, María C

2011-01-01

This study covered the central agricultural region of the Chaco province, which lacks a permanent river networks. However, during the rainy period there is localized groundwater recharge. About 84 groundwater samples were taken during the period April-December 2007. These groundwater samples were collected from two different depths: 62 samples from shallow wells (4 to 20 m) and 24 samples from deep wells (20 to 100 m). Chemical variables were determined: pH, specific conductance, total dissolved solid, hardness, alkalinity, HCO(3)-, CO(3)(2-), SO(4)(2-), Cl-, NO(3)-, NO(2) -, NH(4)+, F-, As((tot)), Na+, K+, Ca2+, Mg2+, Fe, Cu, Ni, Pb and Zn. The chemical composition of groundwater in the study area is dominantly sodium bicarbonate and sodium chloride bicarbonate, comprising more than 60% (52/86) of shallow and deep groundwater samples. Of the 86 analyzed groundwater samples, 88% exceeded the WHO (World Health Organization) and CAA (Código Alimentario Argentino) standards (10 μg/L) for As (arsenic) and 9% exceeded the WHO standard (1.5 mg/L) for F(-).Groundwater highly contaminated with As (max. 1,073 μg/L) and F- (max. 4.2 mg/L) was found in shallow aquifer. The contaminated groundwater is characterized by high pH (max. 8.9), alkalinity (max. HCO(3)- 1,932 mg/L), SO(4)(2-) (max. 11,862 mg/L), Na(+) (max. 3,158 mg/L), Cl(-) (max. 10,493 mg/L) and electric conductivity greater than 33.3 μS/cm. Other associated elements (Ni, Pb, Cu and Zn) are present in low concentrations, except for Fe that in 32% of samples exceeded the guideline value of 0.3 mg/L suggested by the CAA.

Archaeoastronomy in the New World

NASA Astrophysics Data System (ADS)

Aveni, Anthony F.

2010-01-01

List of contributors; 1. Introduction A. F. Aveni; 2. Archaeoastronomy in the Maya region A. F. Aveni; 3. Historical archaeoastronomy: the Hopi example S. C. McCluskey; 4. The Sidereal Lunar Calendar of the Incas R. T. Zuidema; 5. Astronomical norms in Mesoamerican rituals and time-reckoning G. Brotherston; 6. Astronomical knowledge and its uses at Bonampak, Mexico F. G. Lounsbury; 7. Lunar markings of Fajada Butte, Chaco Canyon A. Sofaer, R. M. Sinclair and L. E. Doggett; 8. The Skidi Pawnee earth lodge as an observatory V. D. Chamberlain; 9. Caldendrical petroglyphs of Northern Mexico W. B. Murray; 10. Casa Rinconada, twelfth-century Anasazi Kiva R. A. Williamson.

Taxonomic status of Paraguay's only endemic bird, the Chaco Nothura Nothura chacoensis (Aves: Tinamidae).

PubMed

Hayes, Floyd E; RodrÍguez, Oscar; Thalman, Erika R; Castellanos, Emily A; Sterling, John

2018-03-08

The Chaco Nothura Nothura chacoensis Conover is endemic to the Chaco of western Paraguay. Originally described as a subspecies of the Spotted Nothura N. maculosa (Temminck), it has been regarded by many authorities as a distinct species based on alleged sympatry with N. maculosa. However, an earlier study revealed no differences in cytochrome b sequences between the two taxa. We reanalyzed the geographic distribution and morphological variation of N. chacoensis and N. maculosa in western Paraguay based on museum specimens. There is no locality where specimens of both taxa were collected, thus there is no evidence for sympatry. Morphologically the two taxa did not differ in any size or shape variable. Plumage characters overlapped in a few specimens. We recorded vocalizations from at least four individuals of N. chacoensis within its known range. Its typical territorial song was a very rapid, relatively monotone trill that was virtually identical with the most frequent territorial song of N. maculosa in length, number of notes, rate of notes, and emphasized frequency, and differed substantially from the songs of other species of Nothura. Based on distributional, morphological, biochemical, and especially vocalization data, we conclude that N. chacoensis should be regarded as a subspecies of N. maculosa.

The evolutionary history of Lygodactylus lizards in the South American open diagonal.

PubMed

Lanna, Flávia M; Werneck, Fernanda P; Gehara, Marcelo; Fonseca, Emanuel M; Colli, Guarino R; Sites, Jack W; Rodrigues, Miguel T; Garda, Adrian A

2018-06-12

The Pleistocenic Arc Hypothesis (PAH) posits that South American Seasonally Dry Tropical Forests (SDTF) were interconnected during Pleistocene glacial periods, enabling the expansion of species ranges that were subsequently fragmented in interglacial periods, promoting speciation. The lizard genus Lygodactylus occurs in Africa, Madagascar, and South America. Compared to the high diversity of African Lygodactylus, only two species are known to occur in South America, L. klugei and L. wetzeli, distributed in SDTFs and the Chaco, respectively. We use a phylogenetic approach based on mitochondrial (ND2) and nuclear (RAG-1) markers covering the known range of South American Lygodactylus to investigate (i) if they are monophyletic relative to their African congeners, (ii) if their divergence is congruent with the fragmentation of the PAH, and (iii) if cryptic diversity exists within currently recognized species. Maximum likelihood and Bayesian phylogenetic analyses recovered a well-supported monophyletic South American Lygodactylus, presumably resulting from a single trans-Atlantic dispersal event 29 Mya. Species delimitation analyses supported the existence of five putative species, three of them undescribed. Divergence times among L. klugei and the three putative undescribed species, all endemic to the SDTFs, are not congruent with the fragmentation of the PAH. However, fragmentation of the once broader and continuous SDTFs likely influenced the divergence of L. wetzeli in the Chaco and Lygodactylus sp. 3 (in a SDTF enclave in the Cerrado). Copyright © 2018. Published by Elsevier Inc.

Deforestation changes land-atmosphere interactions across South American biomes

NASA Astrophysics Data System (ADS)

Salazar, Alvaro; Katzfey, Jack; Thatcher, Marcus; Syktus, Jozef; Wong, Kenneth; McAlpine, Clive

2016-04-01

South American biomes are increasingly affected by land use/land cover change. However, the climatic impacts of this phenomenon are still not well understood. In this paper, we model vegetation-climate interactions with a focus on four main biomes distributed in four key regions: The Atlantic Forest, the Cerrado, the Dry Chaco, and the Chilean Matorral ecosystems. We applied a three member ensemble climate model simulation for the period 1981-2010 (30 years) at 25 km resolution over the focus regions to quantify the changes in the regional climate resulting from historical deforestation. The results of computed modelling experiments show significant changes in surface fluxes, temperature and moisture in all regions. For instance, simulated temperature changes were stronger in the Cerrado and the Chilean Matorral with an increase of between 0.7 and 1.4 °C. Changes in the hydrological cycle revealed high regional variability. The results showed consistent significant decreases in relative humidity and soil moisture, and increases in potential evapotranspiration across biomes, yet without conclusive changes in precipitation. These impacts were more significant during the dry season, which resulted to be drier and warmer after deforestation.

Pueblo Folklore, Landscape Phenomenology and the Visual Poetics of Fajada Butte

NASA Astrophysics Data System (ADS)

Carey, C.

2009-08-01

In the interest of reexamining the site of Fajada Butte in Chaco Canyon, this paper seeks to recontextualize discussions of its controversial spiral petroglyphs and astronomical phenomena (Sun Daggers) with reference to landscape phenomenology, visual and literary poetics, and the astronomical orientation of contemporary Pueblo ceremonial practices. The dearth of recent scholarship on Fajada Butte may have arisen from the many controversial arguments about its function from a variety of disciplinary locations including archaeology, anthropology, geology, and archeoastronomy. Via an emphasis on the physical landscape, storytelling, contemporary ceremonial practices and ancestral ties to Chaco Canyon, the Zuni and Hopi pueblos provide a context for re-examining the astronomical phenomena of Fajada Butte as a natural shrine of the of Chacoan culture and repository of an array of symbolic content.

The Strontium Fingerprint and Footprint: Using 87Sr/86Sr to Find the Sources and Range of Architectural Timber Acquisition of Great House Construction at Chaco Canyon, New Mexico

NASA Astrophysics Data System (ADS)

English, N. B.; Reynolds, A. C.; Quade, J.; Betancourt, J. L.

2006-12-01

We describe the spatial and temporal patterns of timber acquisition by great house builders in Chaco Canyon, New Mexico. The 87Sr/86Sr ratios from annually-dated, architectural logs in 10^{th} to 12^{th} century structures are compared to the 87Sr/86Sr of modern tree stands from the surrounding mountains. Although not a stable isotope system, the long half-life of the 87Sr parent (87Rb, t1/2 = 48.8 Ga) yields a stable isotope system on the timescales used to determine the geographic origin of ecosystem resources. The small mass difference among strontium's isotopes eliminates measurable biologic or kinetic fractionation at earth surface conditions. Strontium tracer studies, however, do require distinct end-member ratios to be feasible. Strontium isotopes, alone or in combination with other isotopes, provide a simple way to study and trace the geographic origin of ecosystem resources. Over the 150 km-wide Chaco Basin, 87Sr/86Sr ratios of modern trees range from 0.7055 to 0.7192. 87Sr/86Sr ratios from this and other studies show that during great house construction Chaco Canyon was provisioned with plant materials that came from more than 75 km away in all directions. This includes (1) corn (Zea mays) grown on the eastern flanks of the Chuska Mountains and floodplain of the San Juan River to the west and north, (2) spruce (Picea sp.) and fir (Abies sp.) architectural beams from the high crests of the Chuska and San Mateo Mountains to the west and south, and (3) ponderosa pine (Pinus ponderosa) from the low slopes of the La Platas and San Juan Mountains to the north, the San Pedro Mountains to the east, the Chuska and San Mateo Mountains and nearby mesas. There are no systematic patterns in spruce/fir or ponderosa provenance by great house (Pueblo Bonito, Chetro Ketl, Pueblo del Arroyo) or by time, suggesting the use of stockpiles from a few preferred sources from the beginning of large scale construction in or around Chaco Canyon. This is contrary to the view that Chacoan's travelled further for timber as nearby stands of timber were depleted. The multiple and distant sources for food and timber, now based on hundreds of isotopic values from modern and archeological samples, confirm conventional wisdom about the geographic footprint of the larger Chacoan system. While our study addresses ancient resource procurement patterns, the strontium method is suitable for many modern studies including ecological and forensic applications.

Checklist of vascular plants of the Department of Ñeembucú, Paraguay

PubMed Central

Egea, Juana De; Peña-Chocarro, Maria; Espada, Cristina; Knapp, Sandra

2012-01-01

Abstract The Department of Ñeembucú is one of the least well-documented areas of eastern Paraguay, and the flora is composed of a mixture of forest and Chaco elements. Regions like Ñeembucú are often considered of lower diversity and interest that more forested regions; this results from both actual species richness figures and from under-collecting due to perception as uninteresting. We present here a checklist of the vascular plants of Ñeembucú, which includes 676 taxa (including infraspecific taxa and collections identified only to genus) in 100 families and 374 genera. Four hundred and thirty nine (439) of these are new records for Ñeembucú and of these, 4 are new published records for Paraguay. Synonyms, distribution details within Paraguay and a voucher specimen or literature record are provided for each taxon, and a brief analysis of the diversity and importance of the flora is presented. PMID:22371688

Archaeogenomic evidence reveals prehistoric matrilineal dynasty.

PubMed

Kennett, Douglas J; Plog, Stephen; George, Richard J; Culleton, Brendan J; Watson, Adam S; Skoglund, Pontus; Rohland, Nadin; Mallick, Swapan; Stewardson, Kristin; Kistler, Logan; LeBlanc, Steven A; Whiteley, Peter M; Reich, David; Perry, George H

2017-02-21

For societies with writing systems, hereditary leadership is documented as one of the hallmarks of early political complexity and governance. In contrast, it is unknown whether hereditary succession played a role in the early formation of prehistoric complex societies that lacked writing. Here we use an archaeogenomic approach to identify an elite matriline that persisted between 800 and 1130 CE in Chaco Canyon, the centre of an expansive prehistoric complex society in the Southwestern United States. We show that nine individuals buried in an elite crypt at Pueblo Bonito, the largest structure in the canyon, have identical mitochondrial genomes. Analyses of nuclear genome data from six samples with the highest DNA preservation demonstrate mother-daughter and grandmother-grandson relationships, evidence for a multigenerational matrilineal descent group. Together, these results demonstrate the persistence of an elite matriline in Chaco for ∼330 years.

Archaeogenomic evidence reveals prehistoric matrilineal dynasty

PubMed Central

Kennett, Douglas J.; Plog, Stephen; George, Richard J.; Culleton, Brendan J.; Watson, Adam S.; Skoglund, Pontus; Rohland, Nadin; Mallick, Swapan; Stewardson, Kristin; Kistler, Logan; LeBlanc, Steven A.; Whiteley, Peter M.; Reich, David; Perry, George H.

2017-01-01

For societies with writing systems, hereditary leadership is documented as one of the hallmarks of early political complexity and governance. In contrast, it is unknown whether hereditary succession played a role in the early formation of prehistoric complex societies that lacked writing. Here we use an archaeogenomic approach to identify an elite matriline that persisted between 800 and 1130 CE in Chaco Canyon, the centre of an expansive prehistoric complex society in the Southwestern United States. We show that nine individuals buried in an elite crypt at Pueblo Bonito, the largest structure in the canyon, have identical mitochondrial genomes. Analyses of nuclear genome data from six samples with the highest DNA preservation demonstrate mother–daughter and grandmother–grandson relationships, evidence for a multigenerational matrilineal descent group. Together, these results demonstrate the persistence of an elite matriline in Chaco for ∼330 years. PMID:28221340

Anatomy of the Chaco cryogenic project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milios, P.B.; Harris, R.A.

1997-12-31

In the first quarter of 1996 El Paso Field Services (EPFS) began operation of a new Chaco liquids extraction plant. The plant, located in northwest New Mexico, has the capacity to extract more natural gas liquids (NGL) than any other turboexpander plant in the lower 48 states; 50,000 b/d of NGL from 600 MMscfd of gas. Its existence is the result of El Paso`s desire to combine state-of-the-art processing with processing rates that align EPFS`s interests with the interests of the producers, in order to secure a long term competitive position in the San Juan Basin. All the project stakeholders,more » the producers, the liquids transporter, the construction contractor, and the processor have benefited from the project. Without regulatory reform the project would not have happened.« less

Methicillin-resistant Staphylococcus aureus in hospitalized patients from the Bolivian Chaco.

PubMed

Bartoloni, Alessandro; Riccobono, Eleonora; Magnelli, Donata; Villagran, Ana Liz; Di Maggio, Tiziana; Mantella, Antonia; Sennati, Samanta; Revollo, Carmen; Strohmeyer, Marianne; Giani, Tommaso; Pallecchi, Lucia; Rossolini, Gian Maria

2015-01-01

Information is lacking on the methicillin-resistant Staphylococcus aureus (MRSA) clonal lineages circulating in Bolivia. We investigated the prevalence and molecular epidemiology of S. aureus colonization in hospitalized patients from the Bolivian Chaco, and compared their features with those of the few clinical isolates available from that setting. S. aureus nasal/inguinal colonization was investigated in 280 inpatients from eight hospitals in two point prevalence surveys (2012, n=90; 2013, n=190). Molecular characterization included genotyping (spa typing, multilocus sequence typing, and pulsed-field gel electrophoresis), detection of virulence genes, and SCCmec typing. Forty-one inpatients (14.6%) were S. aureus nasal/inguinal carriers, of whom five were colonized by MRSA (1.8%). MRSA isolates mostly belonged to spa-type t701, harboured SCCmec IVc, and were negative for Panton-Valentine leukocidin (PVL) genes. However, a USA300-related isolate was also detected, which showed the characteristics of the USA300 Latin American variant (USA300-LV; i.e., ST8, spa-type t008, SCCmec IVc, presence of PVL genes, absence of arcA). Notably, all the available MRSA clinical isolates (n=5, collected during 2011-2013) were also identified as USA300-LV. Overall, MRSA colonization in inpatients from the Bolivian Chaco was low. However, USA300-LV-related isolates were detected in colonization and infections, emphasizing the importance of implementing control measures to limit their further dissemination in this resource-limited area. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

The peri-urban interface and house infestation with Triatoma infestans in the Argentine Chaco: an underreported process?

PubMed Central

Provecho, Yael M; Gaspe, M Sol; del Pilar Fernández, M; Enriquez, Gustavo F; Weinberg, Diego; Gürtler, Ricardo E

2014-01-01

Peri-urban infestations with triatomine bugs, their sources and their dynamics have rarely been investigated. Here, we corroborated the reported occurrence of Triatoma infestans in a peri-urban area and in neighbouring rural houses in Pampa del Indio, in the Argentine Chaco, and identified its putative sources using spatial analysis and demographic questionnaires. Peri-urban householders reported that 10% of their premises had triatomines, whereas T. infestans was collected by timed manual searches or community-based surveillance in only nine (3%) houses. Trypanosoma cruzi-infected T. infestans and Triatoma sordida were collected indoors only in peri-urban houses and were infected with TcV and TcI, respectively. The triatomines fed on chickens, cats and humans. Peri-urban infestations were most frequent in a squatter settlement and particularly within the recently built mud houses of rural immigrants, with large-sized households, more dogs and cats and more crowding. Several of the observed infestations were most likely associated with passive bug transport from other sources and with active bug dispersal from neighbouring foci. Thus, the households in the squatter settlement were at a greater risk of bug invasion and colonisation. In sum, the incipient process of domestic colonisation and transmission, along with persistent rural-to-urban migratory flows and unplanned urbanisation, indicate the need for active vector surveillance and control actions at the peri-urban interface of the Gran Chaco. PMID:25410997

Environmental risk assessment of arsenic and fluoride in the Chaco Province, Argentina: research advances.

PubMed

Buchhamer, Edgar E; Blanes, Patricia S; Osicka, Rosa M; Giménez, M Cecilia

2012-01-01

The arsenic (As) and fluoride (F⁻) concentration in groundwater and potential adverse human health risk was investigated in the Central-West Region of the Chaco Province, northern Argentina. The mean concentration of As in shallow groundwater was 95 μg/L, where 76% of samples exceeded the World Health Organization (WHO) guideline value of 10 μg/L, while in deep groundwater it was 90 μg/L, where 63% samples exceeded 10 μg/L. For As health risk assessment, the average daily dose, hazard quotient (HQ), and cancer risk were calculated. The values of HQ were found to be >1 in 77% of samples. This level of contamination is considered to constitute a high chronic risk compared with U.S. Environmental Protection Agency (EPA) guidelines. Further, a significant portion of the population has lifetime carcinogenic risk >10⁻⁴ and may suffer from cancer. A positive correlation was observed between As and F⁻ in groundwater. The Código Alimentario Argentino (CAA) suggested a limit of F⁻ in drinking water as low as 0.8 mg/L under tropical environmental conditions; however, in shallow (39%) and deep groundwater (32%), samples exceeded these values. Exposure to F⁻ was calculated and compared with the adequate intake of minimal safe level exposure dose of 0.05 mg/kg/d and it was noted that 42% of population may be at high risk of fluorosis. Chronic exposure to high As and F⁻ levels in this population represents a concern due to possible adverse health effects attributed to these elements.

Improved Chemical Control of Chagas Disease Vectors in the Dry Chaco Region

PubMed Central

CECERE, MARÍA CARLA; VAZQUEZ-PROKOPEC, GONZALO M.; CEBALLOS, LEONARDO A.; BORAGNO, SILVANA; ZÁRATE, JOAQUÍN E.; KITRON, URIEL; GÜRTLER, RICARDO E.

2013-01-01

The effectiveness of two doses of suspension concentrate (SC) pyrethroid insecticides in suppressing peridomestic populations of Triatoma infestans (Klug) was evaluated in 28 rural communities located in Santiago del Estero province, northwestern Argentina, including 388 houses and 1,516 identified sites. Four treatments were randomly assigned to peridomiciles within each community: 5% SC β-cypermethrin at standard (S, 50 mg active ingredient [AI]/m2) and double dose (2S), and 2.5% SC deltamethrin at standard (D, 25 mg [AI]/m2) and double dose (2D). Simultaneously, we assessed the effects of both pyrethroids applied at standard doses against domestic infestations. Bug infestation at the site level was assessed by timed manual collections with a dislodging agent at baseline, 13 and 21 mo postspraying (MPS). In domiciles, D and S nearly suppressed all T. infestans infestations up to 21 MPS. In peridomestic sites infested before interventions, multiple logistic regression analysis showed that site-level reinfestation at 13 MPS was significantly lower for treatment 2D (1%) than for other treatments, whereas 2S (6%), D (5%), and S (14%) did not differ significantly between them. The risk of reinfestation after spraying was significantly greater in goat or pig corrals than in other peridomestic ecotopes (in which treatments did not differ significantly), and in sites infested before interventions than in uninfested sites. The application of SC deltamethrin at double dose in goat or pig corrals may suppress T. infestans foci and achieve more sustained effects in the dry Chaco. PMID:23540129

The ecology of anemia: Anemia prevalence and correlated factors in adult indigenous women in Argentina.

PubMed

Goetz, Laura G; Valeggia, Claudia

2017-05-06

The Toba/Qom of Namqom are an indigenous community native to the Gran Chaco region of northern Argentina. Historically seminomadic foragers, the diet of peri-urban community members has rapidly changed from high-protein, high-fiber to hypercaloric, processed. This study aims to understand the impact of this nutritional transition on aspects of women's health by exploring the relationship between prevalence of anemia and current diet composition, place of birth, and reproductive history. We measured the capillary hemoglobin (Hb) levels of 153 adult women. Each participant was also given two interviews characterizing reproductive history and a 24-hour food recall. The average Hb level was 12.6 g/dL (range 5.8-15.7 g/dL). In our sample, 28% of participants were anemic and 31% were borderline anemic. Iron and vitamin C consumption were negatively associated with Hb levels. Body mass index was marginally associated with Hb levels. Being born in a peri-urban setting, a proxy for early Westernized diet was associated with higher risk of anemia, suggesting developmental experience may play a role. Pregnant and lactating women had lower Hb levels than menstruating and menopausal women. Age, height, parity, and age at first pregnancy were not found to be statistically significant predictors of anemia. Iron deficiency represents a serious health concern for women, particularly pregnant ones. Our results suggest that both past and current nutritional ecology variables may be associated with the risk of anemia. These findings inform public health interventions, since reproductive history may be more difficult to modify than current diet. © 2017 Wiley Periodicals, Inc.

The Bolivian source rocks: Sub Andean Zone-Madre de Dios-Chaco

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moretti, I.; Montemurro, G.; Aguilera, E.

A complete study of source rocks has been carried out in the Bolivian foothills and foreland (Sub Andean Zone, Chaco and Madre de Dios) in order to quantify the petroleum potential of the area. Besides the classical mid-Devonian source rocks (Tequeje Formation in the north, Limoncito Formation in the center and Los Monos Formation in the south), others are important: the Tomachi Formation (late Devonian) in the north and the Copacabana Formation (Upper Carboniferous-lower Permian) in the northern Sub Andean Zone. Both show an excellent potential with S{sub 2} over 50 mg HC/g and average values higher than 10 mgmore » HC/g over few hundred meters. The Latest Cretaceous Flora Formation present locally a high potential but is very thin. Almost all the source rocks matured during the Neogene due to the subsidence in the Andean foreland and in the piggyback basins, and are thus involved on the current petroleum system. Silurian and Lower Paleozoic units also contain thick shale beds, but these source rocks were mature before the Jurassic in the south of the country. In the center, the Silurian is not nowadays overmature and may play an important role. The different zones are compared based on their Source Potential Index which indicates that the richest areas are the northern Sub Andean Zone and the Madre de Dios basin with SPI greater than 10 t/m{sup 2}. Since these two areas remain almost unexplored, these results allow us to be optimistic about the possibilities for future exploration.« less

[Presence of Legionella spp. in household drinking water reservoirs in Resistencia, Chaco, Argentina. Preliminary report].

PubMed

Lösch, Liliana S; Merino, Luis A

Legionella spp. is an environmental bacterium that can survive in a wide range of physicochemical conditions and may colonize distribution systems of drinking water and storage tanks. Legionella pneumophila is the major waterborne pathogen that can cause 90% of Legionnaires' disease cases. The aim of this study was to detect the presence of Legionella spp. in household drinking water tanks in the city of Resistencia, Chaco. The detection of Legionella in water samples was performed by culture methods as set out in ISO 11731:1998. Thirty two water samples were analyzed and Legionella spp. was recovered in 12 (37.5%) of them. The monitoring of this microorganism in drinking water is the first step towards addressing the control of its spread to susceptible hosts. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Ancient maize from Chacoan great houses: Where was it grown?

PubMed Central

Benson, Larry; Cordell, Linda; Vincent, Kirk; Taylor, Howard; Stein, John; Farmer, G. Lang; Futa, Kiyoto

2003-01-01

In this article, we compare chemical (87Sr/86Sr and elemental) analyses of archaeological maize from dated contexts within Pueblo Bonito, Chaco Canyon, New Mexico, to potential agricultural sites on the periphery of the San Juan Basin. The oldest maize analyzed from Pueblo Bonito probably was grown in an area located 80 km to the west at the base of the Chuska Mountains. The youngest maize came from the San Juan or Animas river floodplains 90 km to the north. This article demonstrates that maize, a dietary staple of southwestern Native Americans, was transported over considerable distances in pre-Columbian times, a finding fundamental to understanding the organization of pre-Columbian southwestern societies. In addition, this article provides support for the hypothesis that major construction events in Chaco Canyon were made possible because maize was brought in to support extra-local labor forces. PMID:14563925

Ancient maize from Chacoan great houses: Where was it grown?

USGS Publications Warehouse

Benson, L.; Cordell, L.; Vincent, K.; Taylor, Howard E.; Stein, J.; Farmer, G.L.; Futa, K.

2003-01-01

In this article, we compare chemical (87Sr/86Sr and elemental) analyses of archaeological maize from dated contexts within Pueblo Bonito, Chaco Canyon, New Mexico, to potential agricultural sites on the periphery of the San Juan Basin. The oldest maize analyzed from Pueblo Bonito probably was grown in an area located 80 km to the west at the base of the Chuska Mountains. The youngest maize came from the San Juan or Animas river floodplains 90 km to the north. This article demonstrates that maize, a dietary staple of southwestern Native Americans, was transported over considerable distances in pre-Columbian times, a finding fundamental to understanding the organization of pre-Columbian southwestern societies. In addition, this article provides support for the hypothesis that major construction events in Chaco Canyon were made possible because maize was brought in to support extra-local labor forces.

Intraplate Stress Field in South America Derived from Earthquake Focal Mechanisms

NASA Astrophysics Data System (ADS)

Dias, F. L.; Assumpcao, M.

2017-12-01

We present an updated compilation of earthquake focal mechanisms in Brazil together with the sub-Andean region through more obtained solutions together with published results from the literature and catalogs of international agencies. Stress orientations from breakouts and in-situ measurements were also compiled. The focal mechanisms were classified according to WSM (World Stress Map) criteria.For Brazil, we have 82 earthquakes with the mechanism that has been determined since 1978, begin that three new from this study. Focal mechanisms in Brazil show reverse, strike-slip and normal faulting while all events in the sub-Andean region have reverse (majority) or strike-slip mechanisms. For sub-Andean region have reverse (majority) or strike-slip mechanisms. Normal mechanisms can be found only in high attitudes. The mechanisms were grouped by proximity to be inverted for the stress tensor. We use the bootstrap technique to analyze the stability of the tensor. In SE Brazil and the Chaco-Pantanal basins, S1 tends to be oriented roughly E-W with S2 approximately equal to S3. This stress pattern changes to purely compressional (both SHmax and Shmin larger than Sv) in the São Francisco craton. A rotation of SHmax from E-W to SE-NW is suggested towards the Amazon region. Along the Atlantic margin, the regional stresses are affected by coastal effects. This coastal effect tends to make SHmax parallel to the coastline and Shmin (usually S3) perpendicular to the coastline. Few breakout data and in-situ measurements are available in Brazil and are generally consistent with the pattern derived from the earthquake focal mechanisms. In the sub-Andean region, the intermediate principal stress (S2) is also compressional, a feature that is not always reproduced in numerical models published in the literature. In mid-plate South America stresses seem to vary in nature and orientation. Although numerical models of global lithospheric stresses tend to reproduce the main large-scale features in most mid-plate areas, the S1 rotation from E-W in SE Brazil to SE-NW in the Amazon region are not well explained by the current numerical models. This means that the observed stress pattern in mid-plate South America should provide new insights into upper mantle dynamics, distinct from current global convection models.

Central Andes mountains, Chile/Argentina as seen from STS-67

NASA Technical Reports Server (NTRS)

1995-01-01

The Chilean coastline and the arid Atacama Desert stretch the length of the view with the high Andes on the eastern margin where hundreds of volcanoes dot the landscape. The wider (250-350 kilometers) Altiplano ('plains') sector of the Andes appears in the top half of the view, and the narrow (120 kilometers) 'mountain-chain-dominated' sector to the bottom. The northern half of Chile can be seen, with the 'hammer-head' peninsula at the city of Antofagasta, top left. Up welling of cold water as the Humboldt Current immediately offshore gives rise to low stratus cloud. The extensive cloud mass on the right lies beyond the Andes in the low country of Argentina's 'pampas' grasslands and Chaco semi-desert.

Positive selection of AS3MT to arsenic water in Andean populations

PubMed Central

Eichstaedt, Christina A.; Antao, Tiago; Cardona, Alexia; Pagani, Luca; Kivisild, Toomas; Mormina, Maru

2016-01-01

Arsenic is a carcinogen associated with skin lesions and cardiovascular diseases. The Colla population from the Puna region in Northwest Argentinean is exposed to levels of arsenic in drinking water exceeding the recommended maximum by a factor of 20. Yet, they thrive in this challenging environment since thousands of years and therefore we hypothesize strong selection signatures in genes involved in arsenic metabolism. We analyzed genome-wide genotype data for 730,000 loci in 25 Collas, considering 24 individuals of the neighbouring Calchaquíes and 24 Wichí from the Gran Chaco region in the Argentine province of Salta as control groups. We identified a strong signal of positive selection in the main arsenic methyltransferase AS3MT gene, which has been previously associated with lower concentrations of the most toxic product of arsenic metabolism monomethylarsonic acid. This study confirms recent studies reporting selection signals in the AS3MT gene albeit using different samples, tests and control populations. PMID:26366667

Epidemiology of and impact of insecticide spraying on Chagas disease in communities in the Bolivian Chaco.

PubMed

Samuels, Aaron M; Clark, Eva H; Galdos-Cardenas, Gerson; Wiegand, Ryan E; Ferrufino, Lisbeth; Menacho, Silvio; Gil, Jose; Spicer, Jennifer; Budde, Julia; Levy, Michael Z; Bozo, Ricardo W; Gilman, Robert H; Bern, Caryn

2013-01-01

Chagas disease control campaigns relying upon residual insecticide spraying have been successful in many Southern American countries. However, in some areas, rapid reinfestation and recrudescence of transmission have occurred. We conducted a cross-sectional survey in the Bolivian Chaco to evaluate prevalence of and risk factors for T. cruzi infection 11 years after two rounds of blanket insecticide application. We used a cubic B-spline model to estimate change in force of infection over time based on age-specific seroprevalence data. Overall T. cruzi seroprevalence was 51.7%. The prevalence was 19.8% among children 2-15, 72.7% among those 15-30 and 97.1% among participants older than 30 years. Based on the model, the estimated annual force of infection was 4.3% over the two years before the first blanket spray in 2000 and fell to 0.4% for 2001-2002. The estimated annual force of infection for 2004-2005, the 2 year period following the second blanket spray, was 4.6%. However, the 95% bootstrap confidence intervals overlap for all of these estimates. In a multivariable model, only sleeping in a structure with cracks in the walls (aOR = 2.35; 95% CI = 1.15-4.78), age and village of residence were associated with infection. As in other areas in the Chaco, we found an extremely high prevalence of Chagas disease. Despite evidence that blanket insecticide application in 2000 may have decreased the force of infection, active transmission is ongoing. Continued spraying vigilance, infestation surveillance, and systematic household improvements are necessary to disrupt and sustain interruption of infection transmission.

Epidemiology of and Impact of Insecticide Spraying on Chagas Disease in Communities in the Bolivian Chaco

PubMed Central

Galdos-Cardenas, Gerson; Wiegand, Ryan E.; Ferrufino, Lisbeth; Menacho, Silvio; Gil, Jose; Spicer, Jennifer; Budde, Julia; Levy, Michael Z.; Bozo, Ricardo W.; Gilman, Robert H.; Bern, Caryn

2013-01-01

Background Chagas disease control campaigns relying upon residual insecticide spraying have been successful in many Southern American countries. However, in some areas, rapid reinfestation and recrudescence of transmission have occurred. Methodology/Principal Findings We conducted a cross-sectional survey in the Bolivian Chaco to evaluate prevalence of and risk factors for T. cruzi infection 11 years after two rounds of blanket insecticide application. We used a cubic B-spline model to estimate change in force of infection over time based on age-specific seroprevalence data. Overall T. cruzi seroprevalence was 51.7%. The prevalence was 19.8% among children 2–15, 72.7% among those 15–30 and 97.1% among participants older than 30 years. Based on the model, the estimated annual force of infection was 4.3% over the two years before the first blanket spray in 2000 and fell to 0.4% for 2001–2002. The estimated annual force of infection for 2004–2005, the 2 year period following the second blanket spray, was 4.6%. However, the 95% bootstrap confidence intervals overlap for all of these estimates. In a multivariable model, only sleeping in a structure with cracks in the walls (aOR = 2.35; 95% CI = 1.15–4.78), age and village of residence were associated with infection. Conclusions/Significance As in other areas in the Chaco, we found an extremely high prevalence of Chagas disease. Despite evidence that blanket insecticide application in 2000 may have decreased the force of infection, active transmission is ongoing. Continued spraying vigilance, infestation surveillance, and systematic household improvements are necessary to disrupt and sustain interruption of infection transmission. PMID:23936581

Evidence of cacao use in the Prehispanic American Southwest

PubMed Central

Crown, Patricia L.; Hurst, W. Jeffrey

2009-01-01

Chemical analyses of organic residues in fragments of ceramic vessels from Pueblo Bonito in Chaco Canyon, New Mexico, reveal theobromine, a biomarker for cacao. With an estimated 800 rooms, Pueblo Bonito is the largest archaeological site in Chaco Canyon and was the center of a large number of interconnected towns and villages spread over northwestern New Mexico. The cacao residues come from pieces of vessels that are likely cylinder jars, special containers occurring almost solely at Pueblo Bonito and deposited in caches at the site. This first known use of cacao drinks north of the Mexican border indicates exchange with cacao cultivators in Mesoamerica in a time frame of about A.D. 1000–1125. The association of cylinder jars and cacao beverages suggests that the Chacoan ritual involving the drinking of cacao was tied to Mesoamerican rituals incorporating cylindrical vases and cacao. The importance of Pueblo Bonito within the Chacoan world likely lies in part with the integration of Mesoamerican ritual, including critical culinary ingredients. PMID:19188605

Plant diversity of the Pantanal wetland.

PubMed

Pott, A; Oliveira, A K M; Damasceno-Junior, G A; Silva, J S V

2011-04-01

This is a review of current studies in diversity of the flora and main vegetation types in the Brazilian Pantanal. The flora of this wetland, nearly 2,000 species, constitutes a pool of elements of wide distribution and from more or less adjacent phytogeographic provinces, such as Cerrado, dry seasonal forests, Chaco, Amazonia and Atlantic Forest. The most numerous group includes wide-distribution species, mainly herbs, while the second contingent comes from the Cerrado. Endemic plants are rare, numbering only seven. The vegetation of the sedimentary floodplain is a mosaic of aquatics, floodable grasslands, riparian forests, savannas (cerrados), cerrado woodlands, dry forests, and a large area of mono-dominant savannas, and pioneer woodlands. The main vegetation types are briefly described with their characteristic species, and their estimated areas are given according to the latest mapping.

Recognition of Culex Bidens Dyar and Culex Interfor Dyar (Diptera: Culicidae) as Separate Species

DTIC Science & Technology

1986-01-01

genitalia. ARGENTINA. Corrientes : locality not specified, 6 specimens. Jujuy: Ledesma, 1 specimen. Santa fe: Calchaqui’, 1 specimen; Humboldt, 2 specimens...close to surface of lateral plate. MATERIAL EXAHINED: 42 male genitalia. ARGENTINA. Chaco: locality not specified, 2 specimens. Corrientes

Biogeography of the Lizard Genus Tropidurus Wied-Neuwied, 1825 (Squamata: Tropiduridae): Distribution, Endemism, and Area Relationships in South America

PubMed Central

de Carvalho, André Luiz Gomes; de Britto, Marcelo Ribeiro; Fernandes, Daniel Silva

2013-01-01

Based on comprehensive distributional records of the 23 species currently assigned to the lizard genus Tropidurus, we investigated patterns of endemism and area relationships in South America. Two biogeographic methods were applied, Parsimony Analysis of Endemicity (PAE) and Brooks Parsimony Analysis (BPA). Two areas of endemism were detected by PAE: the first within the domains of the semiarid Brazilian Caatinga, which includes seven endemic species, and the second in the region of the Serranía de Huanchaca, eastern Bolivia, in which three endemic species are present. The area cladograms recovered a close relationship between the Atlantic Forest and areas of the South American open corridor. The results revealed a close relationship among the provinces Caatinga (Cerrado, Parana Forest (Pantanal+Chaco)). The uplift of the Brazilian Central Plateau in the Late Pliocene-Early Pleistocene (4-2 Myr BP) has been interpreted as a major event responsible for isolation and differentiation of biotas along these areas. However, we emphasize that without the establishment of a temporal framework concerning the diversification history of Tropidurus it is premature to correlate cladogenetic events with specific time periods or putative vicariant scenarios. The limiting factors hampering the understanding of the biogeographic history of this genus include (1) the absence of temporal references in relation to the diversification of distinct clades within Tropidurus; (2) the lack of an appropriate taxonomic resolution of the species complexes currently represented by widely distributed forms; and (3) the need for a comprehensive phylogenetic hypothesis. We suggest that these three important aspects should be prioritized in future investigations. PMID:23527261

Environmental drivers of anuran calling phenology in a seasonal neotropical ecosystem

Treesearch

Christopher M. Schalk; Dan Saenz

2015-01-01

Temporal variation represents an important component in understanding the structure of ecological communities and species coexistence. We examined calling phenology of an assemblage of anurans in the Gran Chaco ecoregion of Bolivia by deploying automated recording devices to document nocturnally vocalizing amphibians nightly at seven...

"Inhabitants of the Earth": Reasoning about Folkbiological Concepts in Wichi Children and Adults

ERIC Educational Resources Information Center

Taverna, Andrea S.; Medin, Douglas L.; Waxman, Sandra R.

2016-01-01

Across the world, people form folkbiological categories to capture their commonsense organization of the natural world. Structured in accordance with universal principles, folkbiological categories are also shaped by experience. Here we provide new evidence from the Wichi--an understudied indigenous community who live in the Chaco rainforest and…

Language Dispute and Social Change in New Multilingual Institutions in Chaco, Argentina

ERIC Educational Resources Information Center

Unamuno, Virginia

2014-01-01

Intercultural bilingual education (IBE) programmes in Latin America pose interesting questions for sociolinguistics, since their implementation interrogates the link between language and the nation resulting from the emergence of nation-states, but also from processes of decolonization. In the case of Argentina, a new legal framework and the…

Effects of the herbicide glyphosate on non-target plant native species from Chaco forest (Argentina).

PubMed

Florencia, Ferreira María; Carolina, Torres; Enzo, Bracamonte; Leonardo, Galetto

2017-10-01

Agriculture based on transgenic crops has expanded in Argentina into areas formerly occupied by Chaco forest. Even though glyphosate is the herbicide most widely used in the world, increasing evidence indicates severe ecotoxicological effects on non-target organisms as native plants. The aim of this work is to determine glyphosate effects on 23 native species present in the remaining Chaco forests immersed in agricultural matrices. This is a laboratory/greenhouse approach studying acute effects on seedlings after 21 days. A gradient of glyphosate rates (525, 1050, 2100, 4200, and 8400g ai/Ha; recommended field application rate (RFAR) = 2100g ai/Ha) was applied on four-week seedlings cultivated in a greenhouse and response variables (phytotoxicity, growth reduction, and sensitivity to the herbicide) were measured. This gradient of herbicide rates covers realistic rates of glyphosate applications in the crop field and also those that can reach vegetation of forest relicts by off-target drift and overspray. Testing was performed following guidelines for vegetative vigour (post-germination spray). All species showed lethal or sublethal effects after the application of the 25% of RFAR (50% of species showed severe phytotoxicity or death and 70% of species showed growth reduction). The results showed a gradient of sensitivity to glyphosate by which some of the studied species are very sensitive to glyphosate and seedlings died with 25% of RFAR while other species can be classified as herbicide-tolerant. Thus, the vegetation present in the forest relicts could be strongly affected by glyphosate application on crops. Lethal and sublethal effects of glyphosate on non-target plants could promote both the loss of biodiversity in native forest relicts immersed in the agroecosystems and the selection of new crop weeds considering that some biotypes are continuously exposed to low doses of glyphosate. Copyright © 2017 Elsevier Inc. All rights reserved.

Application of techniques to identify coal-mine and power-generation effects on surface-water quality, San Juan River basin, New Mexico and Colorado

USGS Publications Warehouse

Goetz, C.L.; Abeyta, Cynthia G.; Thomas, E.V.

1987-01-01

Numerous analytical techniques were applied to determine water quality changes in the San Juan River basin upstream of Shiprock , New Mexico. Eight techniques were used to analyze hydrologic data such as: precipitation, water quality, and streamflow. The eight methods used are: (1) Piper diagram, (2) time-series plot, (3) frequency distribution, (4) box-and-whisker plot, (5) seasonal Kendall test, (6) Wilcoxon rank-sum test, (7) SEASRS procedure, and (8) analysis of flow adjusted, specific conductance data and smoothing. Post-1963 changes in dissolved solids concentration, dissolved potassium concentration, specific conductance, suspended sediment concentration, or suspended sediment load in the San Juan River downstream from the surface coal mines were examined to determine if coal mining was having an effect on the quality of surface water. None of the analytical methods used to analyzed the data showed any increase in dissolved solids concentration, dissolved potassium concentration, or specific conductance in the river downstream from the mines; some of the analytical methods used showed a decrease in dissolved solids concentration and specific conductance. Chaco River, an ephemeral stream tributary to the San Juan River, undergoes changes in water quality due to effluent from a power generation facility. The discharge in the Chaco River contributes about 1.9% of the average annual discharge at the downstream station, San Juan River at Shiprock, NM. The changes in water quality detected at the Chaco River station were not detected at the downstream Shiprock station. It was not possible, with the available data, to identify any effects of the surface coal mines on water quality that were separable from those of urbanization, agriculture, and other cultural and natural changes. In order to determine the specific causes of changes in water quality, it would be necessary to collect additional data at strategically located stations. (Author 's abstract)

Ecological and Sociodemographic Determinants of House Infestation by Triatoma infestans in Indigenous Communities of the Argentine Chaco

PubMed Central

Gaspe, M. Sol; Provecho, Yael M.; Cardinal, M. Victoria; del Pilar Fernández, M.; Gürtler, Ricardo E.

2015-01-01

Background The Gran Chaco ecoregion, a hotspot for Chagas and other neglected tropical diseases, is home to >20 indigenous peoples. Our objective was to identify the main ecological and sociodemographic determinants of house infestation and abundance of Triatoma infestans in traditional Qom populations including a Creole minority in Pampa del Indio, northeastern Argentina. Methods A cross-sectional survey determined house infestation by timed-manual searches with a dislodging aerosol in 386 inhabited houses and administered questionnaires on selected variables before full-coverage insecticide spraying and annual vector surveillance. We fitted generalized linear models to two global models of domestic infestation and bug abundance, and estimated coefficients via multimodel inference with model averaging. Principal Findings Most Qom households were larger and lived in small-sized, recently-built, precarious houses with fewer peridomestic structures, and fewer livestock and poultry than Creoles’. Qom households had lower educational level and unexpectedly high residential mobility. House infestation (31.9%) was much lower than expected from lack of recent insecticide spraying campaigns and was spatially aggregated. Nearly half of the infested houses examined had infected vectors. Qom households had higher prevalence of domestic infestation (29.2%) than Creoles’ (10.0%), although there is large uncertainty around the adjusted OR. Factors with high relative importance for domestic infestation and/or bug abundance were refuge availability, distance to the nearest infested house, domestic insecticide use, indoor presence of poultry, residential overcrowding, and household educational level. Conclusions and Significance Our study highlights the importance of sociodemographic determinants of domestic infestation such as overcrowding, education and proximity to the nearest infested house, and corroborates the role of refuge availability, domestic use of insecticides and household size. These factors may be used for designing improved interventions for sustainable disease control and risk stratification. Housing instability, household mobility and migration patterns are key to understanding the process of house (re)infestation in the Gran Chaco. PMID:25785439

Ecological and sociodemographic determinants of house infestation by Triatoma infestans in indigenous communities of the Argentine Chaco.

PubMed

Sol Gaspe, M; Provecho, Yael M; Cardinal, M Victoria; del Pilar Fernández, M; Gürtler, Ricardo E

2015-03-01

The Gran Chaco ecoregion, a hotspot for Chagas and other neglected tropical diseases, is home to >20 indigenous peoples. Our objective was to identify the main ecological and sociodemographic determinants of house infestation and abundance of Triatoma infestans in traditional Qom populations including a Creole minority in Pampa del Indio, northeastern Argentina. A cross-sectional survey determined house infestation by timed-manual searches with a dislodging aerosol in 386 inhabited houses and administered questionnaires on selected variables before full-coverage insecticide spraying and annual vector surveillance. We fitted generalized linear models to two global models of domestic infestation and bug abundance, and estimated coefficients via multimodel inference with model averaging. Most Qom households were larger and lived in small-sized, recently-built, precarious houses with fewer peridomestic structures, and fewer livestock and poultry than Creoles'. Qom households had lower educational level and unexpectedly high residential mobility. House infestation (31.9%) was much lower than expected from lack of recent insecticide spraying campaigns and was spatially aggregated. Nearly half of the infested houses examined had infected vectors. Qom households had higher prevalence of domestic infestation (29.2%) than Creoles' (10.0%), although there is large uncertainty around the adjusted OR. Factors with high relative importance for domestic infestation and/or bug abundance were refuge availability, distance to the nearest infested house, domestic insecticide use, indoor presence of poultry, residential overcrowding, and household educational level. Our study highlights the importance of sociodemographic determinants of domestic infestation such as overcrowding, education and proximity to the nearest infested house, and corroborates the role of refuge availability, domestic use of insecticides and household size. These factors may be used for designing improved interventions for sustainable disease control and risk stratification. Housing instability, household mobility and migration patterns are key to understanding the process of house (re)infestation in the Gran Chaco.

Aridity and grazing as convergent selective forces: an experiment with an Arid Chaco bunchgrass.

PubMed

Quiroga, R Emiliano; Golluscio, Rodolfo A; Blanco, Lisandro J; Fernández, Roberto J

2010-10-01

It has been proposed that aridity and grazing are convergent selective forces: each one selects for traits conferring resistance to both. However, this conceptual model has not yet been experimentally validated. The aim of this work was to experimentally evaluate the effect of aridity and grazing, as selective forces, on drought and grazing resistance of populations of Trichloris crinita, a native perennial forage grass of the Argentinean Arid Chaco region. We collected seeds in sites with four different combinations of aridity and grazing history (semiarid/ subhumid x heavily grazed/lightly grazed), established them in pots in a common garden, and subjected the resulting plants to different combinations of drought and defoliation. Our results agreed with the convergence model. Aridity has selected T. crinita genotypes that respond better to drought and defoliation in terms of sexual reproduction and leaf growth, and that can evade grazing due to a lower shoot: root ratio and a higher resource allocation to reserves (starch) in stem bases. Similarly, grazing has selected genotypes that respond better to drought and defoliation in terms of sexual reproduction and that can evade grazing due to a lower digestibility of leaf blades. These results allow us to extend concepts of previous models in plant adaptation to herbivory to models on plant adaptation to drought. The only variable in which we obtained a result opposite to predictions was plant height, as plants from semiarid sites were taller (and with more erect tillers) than plants from subhumid sites; we hypothesize that this result might have been a consequence of the selection exerted by the high solar radiation and soil temperatures of semiarid sites. In addition, our work allows for the prediction of the effects of dry or wet growing seasons on the performance of T. crinita plants. Our results suggest that we can rely on dry environments for selecting grazing-resistant genotypes and on high grazing pressure history environments for selecting drought-resistant ones.

Satellite passive microwave remote sensing for estimating diurnal variation of leaf water content, as a proxy of evapotranspiration, in the Dry Chaco Forest, Argentina

NASA Astrophysics Data System (ADS)

Barraza Bernadas, V.; Grings, F.; Ferrazzoli, P.; Carbajo, A.; Fernandez, R.; Karszenbaum, H.

2012-12-01

Evapotranspiration (ET) is a key component of water cycle, which is strongly linked with environmental condition and vegetation functioning. Since it is very difficult to robustly estimate it from remote sensing data at regional scale it is usually inferred from other proxies using water balance. This work describes a procedure to estimate ET in a dry forest by monitoring diurnal variation of leaf water content (LWC), using multitemporal passive microwave remote sensing observations. Hourly observations provide the opportunity to monitor repetitive diurnal variations of passive microwave observations, which can only be accounted by changes in LWC (which is itself related to water vapor that enters to the atmosphere from land surface). To this end, we calculated the vegetation frequency index (FI) as FI= 2*(TBKa-TBX)/ ((TBKa +TBX)), where TBKa and TBX indicate brightness temperatures at 37 and 10.6 GHz respectively. There is both theoretical and experimental evidence that link this index to microwave to LWC. The index was computed for vertical polarization, because it presents higher correlation with vegetation state. At diurnal temporal scale, changes in LWC are commonly very small. Nevertheless, it was previously shown that passive remote sensing data (FI computed using Ku and Ka bands) acquired at different hours can be used to estimate the seasonal changes in ET. In this work, we present a procedure based on the hourly changes of FI, which are interpreted as changes in LWC. In order to present a quantitative estimation, the discrete forest model described in (Ferrazzoli and Guerriero, 1996) has been used to simulate the variations of FI with LWC. To illustrate the procedure, AMSR-E and WINDSAT data from 2007-2009 at X and Ka bands were used, and up to four observations per day at four different local times (2.30 am, 7.00 am, 2.30 pm and 7.00 pm) were analyzed. The region addressed is the area of the Dry Chaco forest located in Bermejo River Basin in Argentina (22-27°S, and 58-66°W).This area is characterized for being an open dry forest (20% of tree crown cover), with mean annual temperatures between 20 and 22 °C, mean summer temperatures between 24 and 27 °C and minimal annual rainfall (500 mm). The annual behavior of diurnal LWC shows a range increase in summer and a decrease in winter, being correlated with vegetation annual growing season (foliation/defoliation). For summertime, our results show a decrease of FI values from 7.00 am to 2.30 pm and an increase between 2.30 pm to 7.00 pm. According to the interaction model, these observed changes of FI corresponded to an increase in LWC from ~0.4 g/g to 0.5 g/g in six hours (7.00 am - 2.30 pm) and then a similar decrease for the 2.30 pm to 7.00 pm period. We hypothesize that this daily variations (an increase of LWC during the sunny hours) could be related to more water being available at the leaves, to cope with evaporation needs in order to achieve positive diurnal water balance during the hot diurnal hours. This could be a specific adaptation to high temperature and drought environmental conditions, like the ones present in Chaco. Ferrazzoli P., Guerriero L.,(1996)"Passive microwave remote sensing of forests: a model investigation", IEEE Transactions on Geoscience and Remote Sensing, vol.34, n. 2, pp.433-443.

Genetic diversity of a late prehispanic group of the Quebrada de Humahuaca, northwestern Argentina.

PubMed

Mendisco, Fanny; Keyser, Christine; Seldes, Veronica; Rivolta, Clara; Mercolli, Pablo; Cruz, Pablo; Nielsen, Axel E; Crubezy, Eric; Ludes, Bertrand

2014-09-01

This palaeogenetic study focused on the analysis of a late prehispanic Argentinean group from the Humahuaca valley, with the main aim of reconstructing its (micro)evolutionary history. The Humahuaca valley, a natural passageway from the eastern plains to the highlands, was the living environment of Andean societies whose cultural but especially biological diversity is still poorly understood. We analyzed the DNA extracted from 39 individuals who populated this upper valley during the Regional Development period (RDP) (between the 11th and 15th centuries CE), to determine their maternal and paternal genetic ancestry. Some mitochondrial and Y-chromosomal haplotypes specific to the Andean region are consistent with an origin in the highlands of Central Andes. On the other hand, a significant genetic affinity with contemporary admixed communities of the Chaco area was detected. Expectedly, recent demographic events, such as the expansion of the Inca Empire or the European colonization, have changed the original mitochondrial gene pool of the ancient Humahuaca Valley community. Finally, we identified a particular geographical organization of the prehispanic populations of Northwestern Argentina. Our results suggest that the communities of the region were divided between two different spheres of interaction, which is consistent with assumptions made by means of craniometric traits. © 2014 John Wiley & Sons Ltd/University College London.

What I Learned about Higher Ed Assessment in a Small Village in South America

ERIC Educational Resources Information Center

Occhipinti, Laurie

2016-01-01

Does assessment change what is being taught? Laurie Occhipinti uses an analogy to answer this question. While conducting research on economic development in a remote rural area of the Argentine Chaco, a community had received some public funds to construct a new community center. They discussed where to place the center. The middle of the village…

The groundwater subsidy to vegetation: groundwater exchanges between landcover patches

NASA Astrophysics Data System (ADS)

Steven, L. I.; Gimenez, R.; Jobbagy, E. G.

2015-12-01

The Gran Chaco is a hot, dry plain, that spans over 60 million hectares across Bolivia, Paraguay, Brazil and Argentina. It supports high biodiversity in its dry forest and savannahs, but is rapidly being converted to agriculture in response to growing soy demand and technology including genetic modification and zero-till, that has made cultivation in drier landscapes more viable. Under natural conditions, the deep-rooted, native vegetation of the Chaco effectively captured all rainfall for evapotranspiration resulting in near zero groundwater recharge under the dry forest. Conversion to shallower rooted soy and corn, combined with the fallow period prior to the growing season, reduces evapotranspiration and allows some water to percolate through the root zone and recharge the groundwater system. When this groundwater recharge occurs, it creates groundwater mounding and a hydraulic gradient that drives flow to adjacent landcover patches where recharge does not occur. As the watertable rises, groundwater becomes available to the deep-rooted, dry forest vegetation. We develop a soil and groundwater flow model to simulate infiltration, percolation, evaporation, rootwater uptake, groundwater recharge and the lateral transfer of water between adjacent landcover patches to quantify this groundwater subsidy from converted agricultural lands to remnant patches of dry forest.

Range extension of Myotis midastactus​ (Chiroptera, Vespertilionidae) to Paraguay

PubMed Central

Idárraga, Liu; Wilson, Don Ellis

2015-01-01

Abstract Background Myotis midastactus Moratelli and Wilson, 2014 (Vespertilionidae, Myotinae) was described from the Myotis simus Thomas, 1901 complex based on collections from the Bolivian Savannah. New information Four vouchers previously assigned to M. simus from the Alto Chaco in Paraguay (West of the Paraguay River) are reassigned here to M. midastactus. These specimens extend the geographic distribution of M. midastactus 1200 km southward, and constitute the first evidence of the species in the country. Based on other material from the Brazilian Pantanal and Cerrado, Central Paraguay and north-eastern Argentina, we also discuss the identity of simus-like populations south of the Amazon Basin. The status of these populations is still unclear, but the little evidence we have at hand indicates that these populations may represent another taxon—M. guaycuru Proença, 1943; whereas M. simus seems to be restricted to the Amazon basin. This hypothesis is still very speculative and requires further investigation. With the assignment of material from Alto Chaco to M. midastactus, seven species of Myotis are confirmed for Paraguay: M. albescens, M. lavali, M. levis, M. midastactus, M. nigricans, M. riparius, and M. ruber. PMID:26379462

Discrete typing units of Trypanosoma cruzi identified in rural dogs and cats in the humid Argentinean Chaco

PubMed Central

ENRIQUEZ, G.F.; CARDINAL, M.V.; OROZCO, M.M.; LANATI, L.; SCHIJMAN, A.G.; GÜRTLER, R.E.

2013-01-01

SUMMARY The discrete typing units (DTUs) of Trypanosoma cruzi that infect domestic dogs and cats have rarely been studied. With this purpose we conducted a cross-sectional xenodiagnostic survey of dog and cat populations residing in two infested rural villages in Pampa del Indio, in the humid Argentine Chaco. Parasites were isolated by culture from 44 dogs and 12 cats with a positive xenodiagnosis. DTUs were identified from parasite culture samples using a strategy based on multiple polymerase-chain reactions. TcVI was identified in 37 of 44 dogs and in 10 of 12 cats, whereas TcV was identified in five dogs and in two cats –a new finding for cats. No mixed infections were detected. The occurrence of two dogs infected with TcIII –classically found in armadillos– suggests a probable link with the local sylvatic transmission cycle involving Dasypus novemcinctus armadillos and a potential risk of human infection with TcIII. Our study reinforces the importance of dogs and cats as domestic reservoir hosts and sources of various DTUs infecting humans, and suggests a link between dogs and the sylvatic transmission cycle of TcIII. PMID:23058180

Amazonia is the primary source of Neotropical biodiversity.

PubMed

Antonelli, Alexandre; Zizka, Alexander; Carvalho, Fernanda Antunes; Scharn, Ruud; Bacon, Christine D; Silvestro, Daniele; Condamine, Fabien L

2018-05-14

The American tropics (the Neotropics) are the most species-rich realm on Earth, and for centuries, scientists have attempted to understand the origins and evolution of their biodiversity. It is now clear that different regions and taxonomic groups have responded differently to geological and climatic changes. However, we still lack a basic understanding of how Neotropical biodiversity was assembled over evolutionary timescales. Here we infer the timing and origin of the living biota in all major Neotropical regions by performing a cross-taxonomic biogeographic analysis based on 4,450 species from six major clades across the tree of life (angiosperms, birds, ferns, frogs, mammals, and squamates), and integrate >1.3 million species occurrences with large-scale phylogenies. We report an unprecedented level of biotic interchange among all Neotropical regions, totaling 4,525 dispersal events. About half of these events involved transitions between major environmental types, with a predominant directionality from forested to open biomes. For all taxonomic groups surveyed here, Amazonia is the primary source of Neotropical diversity, providing >2,800 lineages to other regions. Most of these dispersal events were to Mesoamerica (∼1,500 lineages), followed by dispersals into open regions of northern South America and the Cerrado and Chaco biomes. Biotic interchange has taken place for >60 million years and generally increased toward the present. The total amount of time lineages spend in a region appears to be the strongest predictor of migration events. These results demonstrate the complex origin of tropical ecosystems and the key role of biotic interchange for the assembly of regional biotas. Copyright © 2018 the Author(s). Published by PNAS.

Amazonia is the primary source of Neotropical biodiversity

PubMed Central

2018-01-01

The American tropics (the Neotropics) are the most species-rich realm on Earth, and for centuries, scientists have attempted to understand the origins and evolution of their biodiversity. It is now clear that different regions and taxonomic groups have responded differently to geological and climatic changes. However, we still lack a basic understanding of how Neotropical biodiversity was assembled over evolutionary timescales. Here we infer the timing and origin of the living biota in all major Neotropical regions by performing a cross-taxonomic biogeographic analysis based on 4,450 species from six major clades across the tree of life (angiosperms, birds, ferns, frogs, mammals, and squamates), and integrate >1.3 million species occurrences with large-scale phylogenies. We report an unprecedented level of biotic interchange among all Neotropical regions, totaling 4,525 dispersal events. About half of these events involved transitions between major environmental types, with a predominant directionality from forested to open biomes. For all taxonomic groups surveyed here, Amazonia is the primary source of Neotropical diversity, providing >2,800 lineages to other regions. Most of these dispersal events were to Mesoamerica (∼1,500 lineages), followed by dispersals into open regions of northern South America and the Cerrado and Chaco biomes. Biotic interchange has taken place for >60 million years and generally increased toward the present. The total amount of time lineages spend in a region appears to be the strongest predictor of migration events. These results demonstrate the complex origin of tropical ecosystems and the key role of biotic interchange for the assembly of regional biotas. PMID:29760058

Regional simulation of interannual variability over South America

NASA Astrophysics Data System (ADS)

Misra, V.; Dirmeyer, P. A.; Kirtman, B. P.; Juang, H.-M. Henry; Kanamitsu, M.

2002-08-01

Three regional climate simulations covering the austral summer season during three contrasting phases of the El Niño-Southern Oscillation cycle were conducted with the Regional Spectral Model (RSM) developed at the National Centers for Environmental Prediction (NCEP). The simulated interannual variability of precipitation over the Amazon River Basin, the Intertropical Convergence Zone, the Pacific and Atlantic Ocean basins, and extratropical South America compare reasonably well with observations. The RSM optimally filters the peturbations about a time-varying base field, thereby enhancing the information content of the global NCEP reanalysis. The model is better than the reanalysis in reproducing the observed interannual variability of outgoing longwave radiation at both high frequencies (3-30 days) and intraseasonal (30-60 days) scales. The low-level jet shows a peak in its speed in 1998 and a minimum in the 1999 simulations. The lag correlation of the jet index with convection over various areas in continental South America indicates that the jet induces precipitation over the Pampas region downstream. A detailed moisture budget was conducted over various subregions. This budget reveals that moisture flux convergence determines most of the interannual variability of precipitation over the Amazon Basin, the Atlantic Intertropical Convergence Zone, and the Nordeste region of Brazil. However, both surface evaporation and surface moisture flux convergence were found to be critical in determining the interannual variability of precipitation over the southern Pampas, Gran Chaco area, and the South Atlantic Convergence Zone.

Growth, nutrient status, and photosynthetic response to diesel-contaminated soil of a cordgrass, Spartina argentinensis.

PubMed

Redondo-Gómez, Susana; Petenello, María C; Feldman, Susana R

2014-02-15

The present study was conduced to investigate the tolerance limits of Spartina argentinensis, which occurs in inland marshes of the Chaco-Pampean regions of Argentina, to diesel-contaminated soil. A glasshouse experiment was designed to investigate the effect of diesel fuel from 0% to 3% on growth and photosynthetic apparatus of S. densiflora by measuring gas exchange and photosynthetic pigments. We also performed chemical analysis of plant samples, and determined mycorrhizal index. Tiller and root biomasses declined with increasing diesel fuel concentration, as well as photosynthetic rate (A). Reductions in A could be accounted for by non-stomatal limitations. Mycorrhizal roots of S. argentinensis were reduced by the presence of diesel fuel, but did not affect its nutritional status; in fact, most element concentrations increased with diesel contamination. Despite the negative effect of diesel-contaminated soil, S. argentinensis continued growing, which could be useful management options for phytorremediation of diesel-contaminated soils. Copyright © 2014 Elsevier Ltd. All rights reserved.

STS-55 Earth observation of agricultural development in northern Argentina

NASA Technical Reports Server (NTRS)

1993-01-01

STS-55 Earth observation taken aboard Columbia, Orbiter Vehicle (OV) 102, is of agricultural development in northern Argentina. This photograph is from a mapping strip of photographs acquired by the STS-55 crew. This mapping strip runs from the 'eyelash forests' of the Bolivian Andes, southeast across the Chaco Plains, and into the upper Parana River Basin of north-central Argentina. The formerly densely forested areas between the upper Rio Pilcomayo and the Rio Teuco of NW Argentina rest on deep, rich alluvial and loess deposits. These modern soils were carried into the region by rivers from the Andes and by dust storms from large playa areas of the Altiplano (high plains) of Peru and Boliva. In this scene, representative of the long mapping strip, the process of converting forests to agriculture is far advanced. The original road network, a series of grids laid out in the forest, has nearly coalesced into a farm and ranch landscape. Some few relict forests are still visible as distin

Factors Controlling Pre-Columbian and Early Historic Maize Productivity in the American Southwest, Part 1: The Southern Colorado Plateau and Rio Grande Regions

USGS Publications Warehouse

Benson, L.V.

2011-01-01

Maize is the New World's preeminent grain crop and it provided the economic basis for human culture in many regions within the Americas. To flourish, maize needs water, sunlight (heat), and nutrients (e. g., nitrogen). In this paper, climate and soil chemistry data are used to evaluate the potential for dryland (rainon-field) agriculture in the semiarid southeastern Colorado Plateau and Rio Grande regions. Processes that impact maize agriculture such as nitrogen mineralization, infiltration of precipitation, bare soil evaporation, and transpiration are discussed and evaluated. Most of the study area, excepting high-elevation regions, receives sufficient solar radiation to grow maize. The salinities of subsurface soils in the central San Juan Basin are very high and their nitrogen concentrations are very low. In addition, soils of the central San Juan Basin are characterized by pH values that exceed 8.0, which limit the availability of both nitrogen and phosphorous. In general, the San Juan Basin, including Chaco Canyon, is the least promising part of the study area in terms of dryland farming. Calculations of field life, using values of organic nitrogen for the upper 50 cm of soil in the study area, indicate that most of the study area could not support a 10-bushel/acre crop of maize. The concepts, methods, and calculations used to quantify maize productivity in this study are applicable to maize cultivation in other environmental settings across the Americas. ?? 2010 US Government.

Analysis of uniparental lineages in two villages of Santiago Del Estero, Argentina, seat of Pueblos de Indios in colonial times.

PubMed

Pauro, Maia; García, Angelina; Nores, Rodrigo; Demarchi, Darío A

2013-10-01

Based on the analysis of the mitochondrial control region and seven biallelic markers of the Y chromosome, we investigated the genetic composition of two rural populations of southern Santiago del Estero, Argentina, that were seats in colonial times of pueblos de indios, a colonial practice that consisted of concentrating the indigenous populations in organized and accessible settlements, to facilitate Christianizing and policing. We found the Native American Y chromosome haplogroup Q1a3a in only 11% (3 of 27) of the males. Haplogroup R, common in European populations, is the most frequent haplogroup in Santiago del Estero (55%). In contrast, the persistence of Native American maternal lineages is extremely high (95%). This finding is most likely due to the low incidence in that region of the 20th century European wave of migration and to the existence of pueblos de indios from 1612 to the first decades of the 19th century. In contrast to archeological records that suggest Santiago del Estero late pre-Hispanic groups were strongly influenced by the Andean world, we did not find genetic evidence in support of significant gene fl ow. On the other hand, these populations share many mitochondrial DNA hypervariable region I (HVRI) haplotypes with other populations from the Sierras Pampeanas (particularly with Córdoba) and the Gran Chaco regions. Copyright © 2014 Wayne State University Press, Detroit, Michigan 48201-1309.

Traditional cattle vs. introduced deer management in Chaco Serrano woodlands (Argentina): Analysis of environmental sustainability at increasing densities.

PubMed

Charro, José Luis; López-Sánchez, Aida; Perea, Ramón

2018-01-15

Wild ungulate populations have increased and expanded considerably in many regions, including austral woodlands and forests where deer (Cervus elaphus) have been introduced as an alternative management to traditional cattle grazing. In this study, we compared traditional cattle with introduced deer management at increasing deer densities in the "Chaco Serrano" woodlands of Argentina to assess their ecological sustainability. We used three ecological indicators (abundance of tree regeneration, woody plant diversity and browsing damage) as proxies for environmental sustainability in woody systems. Our results indicate that traditional cattle management, at stocking rates of ∼10 ind km -2 , was the most ecologically sustainable management since it allowed greater tree regeneration abundance, higher richness of woody species and lower browsing damage. Importantly, cattle management and deer management at low densities (10 ind km -2 ) showed no significant differences in species richness and abundance of seedlings, although deer caused greater browsing damage on saplings and juveniles. However, management regimes involving high deer densities (∼35 deer km 2 ) was highly unsustainable in comparison to low (∼10 deer km -2 ) and medium (∼20 deer km -2 ) densities, with 40% probability of unsustainable browsing as opposed to less than 5% probability at low and medium densities. In addition, high deer densities caused a strong reduction in tree regeneration, with a 19-30% reduction in the abundance of seedlings and young trees when compared to low deer densities. These results showed that the effect of increasing deer densities on woody plant conservation was not linear, with high deer densities causing a disproportional deleterious effect on tree regeneration and sustainable browsing. Our results suggest that traditional management at low densities or the use of introduced ungulates (deer breeding areas) at low-medium densities (<20 deer km -2 ) are compatible with woody vegetation conservation. However, further research is needed on plant palatability, animal habitat use (spatial heterogeneity) and species turnover and extinction (comparison to areas of low-null historical browsing) to better estimate environmental sustainability of Neotropical ungulate-dominated woodlands. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enhanced Preliminary Assessment Report: Fort Wingate Depot Activity Gallup, New Mexico

DTIC Science & Technology

1990-03-01

Census, 1980 Census of Population. U 20 uranium exploration, mining, and milling, while the trade sector is influenced by the Zuni and Navajo ...Five Indian reservations, eight national park areas ( Navajo , Chaco Canyon, Aztec Ruins, El Moro National Monuments, Mesa Verde, and Petrified Forest...Argonne National Laboratory Argonne, Illinois 60439 IAppmvd bo o. 90 0611 090 CETHA-BC-CR-90051 Enhanced Preliminary Assessment Report: Fort Wingate Depot

Effects of Low Flying Aircraft on Archaeological Structures

DTIC Science & Technology

1988-09-26

obtained from direct observation of aircraft overflights at one particular site, Ixng House, near Kayenta . Arizona. 2. THE SITE The Long House site is...located approximately 20 km southwest of Kayenta , Arizona, as shown in Figure 1. The Long House ruins were part of an extensive Anasazi agricultural...community that was (Received for Publication 22 September 1988) 1 UTAH COLORADO ARIZONANEW MEXICO LONG HOUSE I FARMINGTON SITE KAYENTA I CHACO CANYON

Argentinian phlebotomine fauna, new records of Phlebotominae (Diptera: Psychodidae) for the country and the province of Chaco.

PubMed

Szelag, Enrique A; Filho, Jose D Andrade; Rosa, Juan R; Parras, Matias A; Quintana, Maria G; Quintana, Maria G; Salomon, Oscar D

2016-07-21

Sand flies are insects of medical and veterinary importance, because some species are able to transmit several pathogens such as Bartonella spp., Phlebovirus spp., and protozoan parasites of the genus Leishmania (Ross). They are widely distributed in the Americas, with recordings ranging from Canada to Argentina. Approximately 500 Phlebotominae species are known in the Americas, of which it is considered that at least 56 are involved in the transmission of leishmaniasis (Maroli et al. 2012). Previous studies have shown that the phlebotomine fauna in Argentina consists of 32 species distributed in 14 provinces (Quintana et al. 2012; Sábio et al. 2015; Salomón et al. 2010). Of these species, Lutzomyia longipalpis (Lutz & Neiva), Nyssomyia neivai (Pinto), Ny. whitmani (Antunes & Countinho), Cortelezzii complex [Evandromyia cortelezzii (Brèthes) - Ev. sallesi (Galvão & Coutinho)], Micropygomyia quinquefer (Dyar) and Migonemyia migonei (França) have been found with DNA of Leishmania spp. (Moya et al. 2015). Five new records of species in the province of Chaco, obtained from different projects carried out between 2001 and 2015, four of which are also new records for Argentina, are described in this article. Their importance as potential vectors and the correct determination of the sympatric species is also discussed.

Intestinal parasitic infections and associated epidemiological drivers in two rural communities of the Bolivian Chaco.

PubMed

Macchioni, Fabio; Segundo, Higinio; Totino, Valentina; Gabrielli, Simona; Rojas, Patricia; Roselli, Mimmo; Paredes, Grover Adolfo; Masana, Mario; Bartoloni, Alessandro; Cancrini, Gabriella

2016-09-30

In 2013 a coproparasitological survey was carried out in two rural communities of the Bolivian Chaco to determine the prevalence of intestinal parasitic infections (IPIs) and to investigate on possible infection drivers through a questionnaire interview. Faecal samples were examined by microscopy. Samples positive for Entamoeba histolytica complex and Blastocystis were molecularly examined to identify the species/subtypes involved. The overall infection rate was 86%, identical in both communities and mostly due to protozoa. Soil-transmitted helminths were detected in <3% of children and adults. The protozoa detected, including Blastocystis subtypes, indicate faecal contamination of the environment by both humans (as confirmed by the presence of Hymenolepis nana) and animals. Nested-PCR identified E. histolytica, thus signalling the possible occurrence of invasive amoebosis. Lack of safe water, environmental contamination, poor sanitation and hygiene, shared by both communities, are the main drivers of IPIs. In addition, unlike gender and socioeconomic factors, childhood (only for some species), crowding and cohabitation with animals proved to be further significant protozoon infection risk factors. These results highlight the need for the promotion of access to clean water, improved sanitation and better hygiene, thus reducing the frequency of preventive chemotherapy for STHs while continuing to monitor the population for possible recrudescence.

Active dispersal of Triatoma infestans and other triatomines in the Argentinean arid Chaco before and after vector control interventions.

PubMed

Abrahan, Luciana; Gorla, David; Catalá, Silvia

2016-06-01

Peridomestic structures are considered the main sites where Triatoma infestans (Hemiptera: Reduviidae) remain and disperse, representing the first risk factor for intradomestic invasion, even after vector control activities. This study analyzed T. infestans dispersal during vector control interventions in six rural houses of the arid Chaco (La Rioja, Argentina). Flying and walking dispersers were captured during five months of two consecutive warm seasons after insecticide spraying of intra- and peridomiciles. These data were compared with previous published data in the same scenario but without insecticide spraying in peridomiciles. Recorded climatic conditions were favorable for active dispersion during the study. Total number of T. infestans dispersers moving among domestic habitats decreased after insecticide spraying. Sylvatic triatomines T. guasayana, T. eratyrusiformis, T. garciabesi, and T. platensis, not targeted by insecticide spraying, were captured simultaneously within peridomestic areas and showed higher invasion pressure than T. infestans. Adult T. infestans peridomestic populations showed high nutritional status, indicating low dispersion probability. Some peridomiciles remained infested at the end of the study. However, no intradomiciles were recolonized. These results suggest that there is a low probability of intradomestic recolonization by active dispersion from peridomiciles during 15 months post-spraying. © 2016 The Society for Vector Ecology.

Brief communication: unusual finding at Pueblo Bonito: multiple cases of hyperostosis frontalis interna.

PubMed

Mulhern, Dawn M; Wilczak, Cynthia A; Dudar, J Christopher

2006-08-01

Hyperostosis frontalis interna (HFI) is a disease characterized by excess bone growth on the internal lamina of the frontal bone and, occasionally, other cranial bones. Although the disease is fairly common in modern populations, its etiology is poorly understood. Hyperostosis frontalis interna has been identified in antiquity, primarily in the Old World, but with a much lower frequency than in modern groups. The purpose of the present study is to report multiple cases of HFI at Pueblo Bonito (Chaco Canyon, New Mexico). Twelve out of 37 adults with observable frontal bones exhibited HFI, ranging from mild to severe, including 11 females and one male. This is the first published case report of HFI in archaeological remains from the New World having a frequency comparable with modern groups. Most archaeological cases of HFI are isolated, so comparative data for multiple cases at one site are rare. The results of this study emphasize the importance of looking for HFI in archaeological remains, although it is rarely observed. Possible genetic and environmental factors for the high frequency of HFI at Chaco Canyon are considered, but additional research is needed to discover the etiology and to better understand why HFI sometimes occurs at modern frequencies in ancient populations.

Large U.S. liquids plant starts up

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milios, P.B.; Harris, R.A.

1997-05-12

Operation began in 1996 on the new Chaco liquids-extraction plant in northwest New Mexico. The plant`s extraction capacity--50,000 b/d of NGLs from 600 MMcfd of gas--exceeds that of any other turboexpander plant in the lower 48 states. Regulatory reform made the project possible, and significant regulatory, economic, environmental, technical, and logistic challenges were overcome to achieve plant start-up. Operator El Paso Field Services, Houston, believes the new Chaco plant creates added value when compared to the lean-oil extraction plant which El Paso had operated at the San Juan basin site since the 1950s. Success of the project was based, inmore » part, on the following: creation of a free-market company by the spin-down of El Paso Field Services (EPFS) from El Paso Natural Gas (EPNG); establishment of agreements with producers behind the plant to share the benefits generated by the plant in exchange for acreage dedication; negotiation of an agreement with Mid-America Pipeline Co. to expand its pipeline system to receive and deliver to market liquids from the new plant; and selection of ABB Randall which committed to engineer, procure for, and construct the plant at a cost which provided an adequate rate of return. These four issues are discussed. Construction and start-up are described.« less

Depths of channels in the area of the San Juan Basin Regional Uranium Study, New Mexico, Colorado, Arizona, and Utah

USGS Publications Warehouse

Cooley, Maurice E.

1979-01-01

During December 1977 and January 1978 about 280 measurements were made of the depths of channels (arroyos) more than 6 feet deep in the San Juan Basin area. More than half of the measurements were made at sites where channel depths had been previously measured Between 1964 and 1969. Some channels in the western part of the basin had Been re-measured in 1969 and in 1971. The principal areas Being dissected by arroyos are near highlands along the margins of the Basin and in uplands in the northeastern part of the Basin. The most severe dissection by arroyos and the deepest arroyos--commonly Between 40 and 60 feet deep--are in the southeastern part of the Basin. Dissection By arroyos is least in the central part of the Basin near the Chaco River where most arroyos are less than 10 feet deep. Elsewhere, moderate dissection predominates with most arroyos Between 12 and 40 feet deep. Comparison of measurements made from 1964-71 with those made in 1977-78 shows that more channels in the western San Juan Basin were filling than were downcutting. Downcutting or filling was generally less than 2 feet. About two-fifths of the sites measured showed less than half a foot of downcutting or filling. Maximum downcutting was 4 feet along the Rio San Jose in the southeastern part of the basin. Maximum filling of 7 feet was along the Chaco River at the Chaco Canyon National Monument. Along ii other streams elsewhere in the western part of the basin, channels were filled 3 to 4.5 feet. The few measurements made in the southeastern San Juan Basin indicate that since 1964 downcutting has predominated over filling. Large floods during the summer of 1977 caused some change in channel depths in the southwestern part of the San Juan Basin. Some of the channels appeared to have been filled during the years prior to the cutting that occurred from the 1977 floods. At other places, flood flows aggraded (filled) channels. The rate of erosion and arroyo formation in the entire San Juan Basin is effected by man. The southeastern part of the basin--having been occupied by man for several centuries--shows the greatest effects of man on the rate of arroyo formation. Recent urban developments, particularly near Gallup, also appear to have affected the rate of erosion and arroyo formation. In contrast, arroyos appear to be aggrading below many earth-fill dams. In general, the effects of the petroleum, coal, and uranium exploration and development on arroyo formation have been minimal because the main trenching of the arroyos predates oil and mining operations. Some modification--degradation or aggradation--of the arroyos and local trenching of new arroyos have taken place in the area of some of the mines. Most of the observed effects from the mining operations on erosion and aggradation relate to the discharge of mine and mill water into the nearby streams.

Microgeographical study of insecticide resistance in Triatoma infestans from Argentina.

PubMed

Germano, Mónica D; Picollo, María Inés; Mougabure-Cueto, Gastón A

2013-12-01

Chagas disease is a chronic parasitic infection restricted to America where it is currently estimated that 90 million people are at risk of acquiring the infection. Chemical control with pyrethroid insecticides has been effective to reduce disease transmission in several areas of the Southern Cone, although insecticide resistance has evolved and diminished the campaigns' results. Considering previous reports on the different levels of resistance between Triatoma infestans from different geographical areas, the objective of this work was to determine if T. infestans populations are toxicologically structured within localities. Response to the insecticide was measured and compared between houses of two Argentine localities. Different toxicity of deltamethrin was detected between dwellings of Chaco province, accounting for both susceptible and resistant houses within the same locality. However no difference was found among houses of Salta province. The results obtained in this work suggest that geographical structure is present not only at the between localities level, but also at the microgeograhical level. Copyright © 2013 Elsevier B.V. All rights reserved.

Genetic and Morphometric Variability of Triatoma sordida (Hemiptera: Reduviidae) from the Eastern and Western Regions of Paraguay.

PubMed

Gonzalez-Britez, Nilsa E; Carrasco, Hernán J; Martínez Purroy, Clara Elena; Feliciangeli, M Dora; Maldonado, Marisel; López, Elsa; Segovia, Maikell J; Rojas de Arias, Antonieta

2014-01-01

Triatoma sordida is widely distributed throughout the Chaco and the Eastern Region of Paraguay. It is associated to palm trees and artificial ecotopes located in peridomestic environments. The aim of this work was to determine genetic and morphometric variability and feeding behavior among population of T. sordida captured in domicile and peridomicile areas of Paraguay. Feeding contents and levels of genetic and morphometric variation were determined in 124 T. sordida from domicile and peridomicile populations of San Pedro and Paraguarí departments of the Eastern Region and Boquerón and Presidente Hayes departments of the Western region using Double Diffusion Gel, random amplified polymorphic DNA (RAPD), and head and wings morphometry. Morphometric analysis revealed isolation of populations by geographic region and larger size in triatomine populations from the Western Region. RAPD showed no specific patterns for domicile and peridomicile populations. The estimator of diversity (F ST; 0.08) and high gene flow obtained (N m; 5.7) did not allow the establishment of genetic differentiation within the same region. The blood meal source showed that poultry feeding was 38% of host preferences, and human blood was the second feeding preference (24%) in the insects from the Eastern Region while poultry feeding was predominant in those from the Western Region (30%). This work showed homogeneity between T. sordida populations of the same region and between domicile and peridomicile. The genetic diversity was determined among T. sordida populations of both geographical regions suggesting differentiation associated to eco-geographical isolation by distance. It is important to notice that pattern feedings were different between the two regions. Further studies should be focused on how phenetic and genetic variations could be related to the adaptation capacity of these triatomine populations to domicile, increasing their vector potentiality in the transmission of Chagas disease.

The Role of Satellite Imagery to Improve Pastureland Estimates in South America

NASA Astrophysics Data System (ADS)

Graesser, J.

2015-12-01

Agriculture has changed substantially across the globe over the past half century. While much work has been done to improve spatial-temporal estimates of agricultural changes, we still know more about the extent of row-crop agriculture than livestock-grazed land. The gap between cropland and pastureland estimates exists largely because it is challenging to characterize natural versus grazed grasslands from a remote sensing perspective. However, the impasse of pastureland estimates is set to break, with an increasing number of spaceborne sensors and freely available satellite data. The Landsat satellite archive in particular provides researchers with immense amounts of data to improve pastureland information. Here we focus on South America, where pastureland expansion has been scrutinized for the past few decades. We explore the challenges of estimating pastureland using temporal Landsat imagery and focus on key agricultural countries, regions, and ecosystems. We focus on the suggested shift of pastureland from the Argentine Pampas to northern Argentina, and the mixing of small-scale and large-scale ranching in eastern Paraguay and how it could impact the Chaco forest to the west. Further, the Beni Savannahs of northern Bolivia and the Colombian Llanos—both grassland and savannah regions historically used for livestock grazing—have been hinted at as future areas for cropland expansion. There are certainly environmental concerns with pastureland expansion into forests; but what are the environmental implications when well-managed pasture systems are converted to intensive soybean or palm oil plantation? Tropical, grazed grasslands are important habitats for biodiversity, and pasturelands can mitigate soil erosion when well managed. Thus, we must improve estimates of grazed land before we can make informed policy and conservation decisions. This talk presents insights into pastureland estimates in South America and discusses the feasibility to improve current areal, land use, and scale estimates of livestock grazing using satellite imagery.

Is imidacloprid an effective alternative for controlling pyrethroid-resistant populations of Triatoma infestans (Hemiptera: Reduviidae) in the Gran Chaco ecoregion?

PubMed

Carvajal, Guillermo; Picollo, María Inés; Toloza, Ariel Ceferino

2014-09-01

The prevention of Chagas disease is based primarily on the chemical control of Triatoma infestans (Klug) using pyrethroid insecticides. However, high resistance levels, correlated with control failures, have been detected in Argentina and Bolivia. A previous study at our laboratory found that imidacloprid could serve as an alternative to pyrethroid insecticides. We studied the delayed toxicity of imidacloprid and the influence of the blood feeding condition of the insect on the toxicity of this insecticide; we also studied the effectiveness of various commercial imidacloprid formulations against a pyrethroid-resistant T. infestans population from the Gran Chaco ecoregion. Variations in the toxic effects of imidacloprid were not observed up to 72 h after exposure and were not found to depend on the blood feeding condition of susceptible and resistant individuals. Of the three different studied formulations of imidacloprid on glass and filter paper, only the spot-on formulation was effective. This formulation was applied to pigeons at doses of 1, 5, 20 and 40 mg/bird. The nymphs that fed on pigeons treated with 20 mg or 40 mg of the formulation showed a higher mortality rate than the control group one day and seven days post-treatment (p < 0.01). A spot-on formulation of imidacloprid was effective against pyrethroid-resistant T. infestans populations at the laboratory level.

Is imidacloprid an effective alternative for controlling pyrethroid-resistant populations of Triatoma infestans (Hemiptera: Reduviidae) in the Gran Chaco ecoregion?

PubMed Central

Carvajal, Guillermo; Picollo, María Inés; Toloza, Ariel Ceferino

2014-01-01

The prevention of Chagas disease is based primarily on the chemical control of Triatoma infestans (Klug) using pyrethroid insecticides. However, high resistance levels, correlated with control failures, have been detected in Argentina and Bolivia. A previous study at our laboratory found that imidacloprid could serve as an alternative to pyrethroid insecticides. We studied the delayed toxicity of imidacloprid and the influence of the blood feeding condition of the insect on the toxicity of this insecticide; we also studied the effectiveness of various commercial imidacloprid formulations against a pyrethroid-resistant T. infestans population from the Gran Chaco ecoregion. Variations in the toxic effects of imidacloprid were not observed up to 72 h after exposure and were not found to depend on the blood feeding condition of susceptible and resistant individuals. Of the three different studied formulations of imidacloprid on glass and filter paper, only the spot-on formulation was effective. This formulation was applied to pigeons at doses of 1, 5, 20 and 40 mg/bird. The nymphs that fed on pigeons treated with 20 mg or 40 mg of the formulation showed a higher mortality rate than the control group one day and seven days post-treatment (p < 0.01). A spot-on formulation of imidacloprid was effective against pyrethroid-resistant T. infestans populations at the laboratory level. PMID:25141281

Habitat degradation may affect niche segregation patterns in lizards

NASA Astrophysics Data System (ADS)

Pelegrin, N.; Chani, J. M.; Echevarria, A. L.; Bucher, E. H.

2013-08-01

Lizards partition resources in three main niche dimensions: time, space and food. Activity time and microhabitat use are strongly influenced by thermal environment, and may differ between species according to thermal requirements and tolerance. As thermal characteristics are influenced by habitat structure, microhabitat use and activity of lizards can change in disturbed habitats. We compared activity and microhabitat use of two abundant lizard species of the Semi-arid Chaco of Argentina between a restored and a highly degraded Chaco forest, to determine how habitat degradation affects lizard segregation in time and space, hypothesizing that as activity and microhabitat use of lizards are related to habitat structure, activity and microhabitat use of individual species can be altered in degraded habitats, thus changing segregation patterns between them. Activity changed from an overlapped pattern in a restored forest to a segregated pattern in a degraded forest. A similar trend was observed for microhabitat use, although to a less extent. No correlation was found between air temperature and lizard activity, but lizard activity varied along the day and among sites. Contrary to what was believed, activity patterns of neotropical diurnal lizards are not fixed, but affected by multiple factors related to habitat structure and possibly to interspecific interactions. Changes in activity patterns and microhabitat use in degraded forests may have important implications when analyzing the effects of climate change on lizard species, due to synergistic effects.

Archaeological Reconnaissance Survey of Pool 10, Upper Mississippi River, Grant and Crawford Counties, Wisconsin, and Allamakee and Clayton Counties, Iowa

DTIC Science & Technology

1984-10-01

buried archaeo- logical components during the Stage I sample provided useful - new information. At the same time , Stage I sample results demonstrated...by erosion directly related to maintenance and operation of the 9 foot navigation channel. At the same time , numerous sites of early to middle...Analysis. Publication No. 3, Chaco Center Studies. National Park Service and University of New Mexico. MALLAM, R. CLARK 1976 The Iowa Effigy Mound

The Coast Artillery Journal. Volume 78, Number 3, May-June 1935

DTIC Science & Technology

1935-06-01

proper. The two belligerents are now approaching what most military observers believe will be the final and de - cisive campaign of the war. Apart from the...all great leaders, he at once began an exhaustive study of the Chaco Boreal. In 1927 he finished a three-year course at the French Ecole Superieure de ... de - livered over the same terrain as the Julv offensive, forced Estigarribia to withdraw troops froni the defenses of Camp Jordan to meet it. Thereupon

Panoramic View of the Andes Mountains, Chile and Argentina

NASA Technical Reports Server (NTRS)

1992-01-01

This panoramic view of the Andes Mountains of Chile and Argentina (24.5S, 69.5W) is dominated by the yellows and browns of the coastal Atacama Desert and the full width of the Andes altiplano, about 300 miles. Winter snow can be seen capping the 22,000 to 23,000 ft. peaks of the Andes. Wisps of cirrus clouds lie over the altiplano and offshore fog obscures the coast. In the distance, the low Chaco Plain appears green with pastures and agriculture.

Biological Control of the Chagas Disease Vector Triatoma infestans with the Entomopathogenic Fungus Beauveria bassiana Combined with an Aggregation Cue: Field, Laboratory and Mathematical Modeling Assessment

PubMed Central

Forlani, Lucas; Pedrini, Nicolás; Girotti, Juan R.; Mijailovsky, Sergio J.; Cardozo, Rubén M.; Gentile, Alberto G.; Hernández-Suárez, Carlos M.; Rabinovich, Jorge E.; Juárez, M. Patricia

2015-01-01

Background Current Chagas disease vector control strategies, based on chemical insecticide spraying, are growingly threatened by the emergence of pyrethroid-resistant Triatoma infestans populations in the Gran Chaco region of South America. Methodology and findings We have already shown that the entomopathogenic fungus Beauveria bassiana has the ability to breach the insect cuticle and is effective both against pyrethroid-susceptible and pyrethroid-resistant T. infestans, in laboratory as well as field assays. It is also known that T. infestans cuticle lipids play a major role as contact aggregation pheromones. We estimated the effectiveness of pheromone-based infection boxes containing B. bassiana spores to kill indoor bugs, and its effect on the vector population dynamics. Laboratory assays were performed to estimate the effect of fungal infection on female reproductive parameters. The effect of insect exuviae as an aggregation signal in the performance of the infection boxes was estimated both in the laboratory and in the field. We developed a stage-specific matrix model of T. infestans to describe the fungal infection effects on insect population dynamics, and to analyze the performance of the biopesticide device in vector biological control. Conclusions The pheromone-containing infective box is a promising new tool against indoor populations of this Chagas disease vector, with the number of boxes per house being the main driver of the reduction of the total domestic bug population. This ecologically safe approach is the first proven alternative to chemical insecticides in the control of T. infestans. The advantageous reduction in vector population by delayed-action fungal biopesticides in a contained environment is here shown supported by mathematical modeling. PMID:25969989

Control of experimental Triatoma infestans populations: effect of pour-on cypermethrin applied to chickens under natural conditions in the Argentinean Chaco region.

PubMed

Amelotti, I; Catalá, S S; Gorla, D E

2014-06-01

Among peridomestic structures, chicken coops are sites of major importance for the domestic ecology of Triatoma infestans (Hemiptera: Reduviidae). The aim of this study was to evaluate in an experimental context the effects of a cypermethrin pour-on formulation applied to chickens on blood intake, moulting and mortality in T. infestans, under the natural climatic conditions of a region endemic for Chagas' disease. Experimental chicken huts were made of bricks and covered with plastic mosquito nets. Ninety fourth-instar nymphs were maintained in each hut. The study used a completely random design in which chickens in the experimental group were treated with a cypermethrin pour-on formulation. Five replicates (= huts) of the experimental and control groups were conducted. The number of live T. infestans, blood intake and moults to fifth-instar stage were recorded at 1, 5, 20, 35 and 45 days after the application of cypermethrin. Cumulative mortality was higher in nymphs exposed to treated chickens (> 71%) than in control nymphs (< 50%) (P < 0.01). Blood intake and moulting rate were lower in nymphs fed on treated chickens than in control nymphs (P < 0.05). Pour-on cypermethrin was able to cause significant mortality, although it did not eliminate the experimental population of T. infestans. © 2013 The Royal Entomological Society.

Antimicrobial susceptibility and emerging resistance determinants (blaCTX-M, rmtB, fosA3) in clinical isolates from urinary tract infections in the Bolivian Chaco.

PubMed

Bartoloni, Alessandro; Sennati, Samanta; Di Maggio, Tiziana; Mantella, Antonia; Riccobono, Eleonora; Strohmeyer, Marianne; Revollo, Carmen; Villagran, Ana Liz; Pallecchi, Lucia; Rossolini, Gian Maria

2016-02-01

Bolivia is among the lowest-resourced South American countries, with very few data available on antibiotic resistance in bacterial pathogens. The phenotypic and molecular characterization of bacterial isolates responsible for urinary tract infections (UTIs) in the Bolivian Chaco are reported here. All clinical isolates from UTIs collected in the Hospital Basico Villa Montes between June 2010 and January 2014 were analyzed (N=213). Characterization included susceptibility testing, extended-spectrum beta-lactamase (ESBL) detection, identification of relevant resistance determinants (e.g., CTX-M-type ESBLs, 16S rRNA methyltransferases, glutathione S-transferases), and genotyping of CTX-M producers. Very high resistance rates were observed. Overall, the lowest susceptibility was observed for trimethoprim-sulphamethoxazole, tetracycline, nalidixic acid, amoxicillin-clavulanic acid, ciprofloxacin, and gentamicin. Of E. coli and K. pneumoniae, 11.6% were ESBL producers. Resistance to nitrofurantoin, amikacin, and fosfomycin remained low, and susceptibility to carbapenems was fully preserved. CTX-M-15 was the dominant CTX-M variant. Four E. coli ST131 (two being H30-Rx) were identified. Of note, isolates harbouring rmtB and fosA3 were detected. Bolivia is not an exception to the very high resistance burden affecting many South American countries. Optimization of alternative approaches to monitor local antibiotic resistance trends in resource-limited settings is strongly encouraged to support the implementation of effective empiric treatment guidelines. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Classification of immature mosquito species according to characteristics of the larval habitat in the subtropical province of Chaco, Argentina.

PubMed

Stein, Marina; Ludueña-Almeida, Francisco; Willener, Juana Alicia; Almirón, Walter Ricardo

2011-06-01

To classify mosquito species based on common features of their habitats, samples were obtained fortnightly between June 2001-October 2003 in the subtropical province of Chaco, Argentina. Data on the type of larval habitat, nature of the habitat (artificial or natural), size, depth, location related to sunlight, distance to the neighbouring houses, type of substrate, organic material, vegetation and algae type and their presence were collected. Data on the permanence, temperature, pH, turbidity, colour, odour and movement of the larval habitat's water were also collected. From the cluster analysis, three groups of species associated by their degree of habitat similarity were obtained and are listed below. Group 1 consisted of Aedes aegypti. Group 2 consisted of Culex imitator, Culex davisi, Wyeomyia muehlensi and Toxorhynchites haemorrhoidalis separatus. Within group 3, two subgroups are distinguished: A (Psorophora ferox, Psorophora cyanescens, Psorophora varinervis, Psorophora confinnis, Psorophora cingulata, Ochlerotatus hastatus-oligopistus, Ochlerotatus serratus, Ochlerotatus scapularis, Culex intrincatus, Culex quinquefasciatus, Culex pilosus, Ochlerotatus albifasciatus, Culex bidens) and B (Culex maxi, Culex eduardoi, Culex chidesteri, Uranotaenia lowii, Uranotaenia pulcherrima, Anopheles neomaculipalpus, Anopheles triannulatus, Anopheles albitarsis, Uranotaenia apicalis, Mansonia humeralis and Aedeomyia squamipennis). Principal component analysis indicates that the size of the larval habitats and the presence of aquatic vegetation are the main characteristics that explain the variation among different species. In contrast, water permanence is second in importance. Water temperature, pH and the type of larval habitat are less important in explaining the clustering of species.

Arsenic concentration in water and bovine milk in Cordoba, Argentina. Preliminary results.

PubMed

Pérez-Carrera, Alejo; Fernández-Cirelli, Alicia

2005-02-01

The Chaco Pampean Plain of central Argentina constitutes one of the largest regions of high arsenic (As) groundwaters known, covering around 1 x 10(6) km2 (Smedley & Kinniburg, 2002; Farías et al. 2004). The high-As groundwaters are from Quaternary deposits of loess (mainly silt) with intermixed rhyolitic or dacitic volcanic ash (Nicolli et al. 1989, Smedley et al. 1998,2002). Early in the last century an endemic disease due to contamination of drinking water with arsenic was recognised. This disease is called HACRE (Hidroarsenicismo Crónico Regional Endémico, Chronic Endemic Regional Hydroarsenism) and is connected with a particular type of skin cancer (Astolfi et al. 1981). One of the most affected region is the province of Cordoba, where Nicolli et al. (1989) reported As concentrations that exceed the maximun level permitted for drinking water of 50 microg/l for 82% of the groundwater samples (n=60) of a study area comprising approximately 10000 km2. The southeast of Cordoba is an important milk production zone in Argentina, where dairy product consumption is up to 192 equivalent milk l/inhabitant/year. As a secretion of the mammary gland, milk can carry numerous xenobiotic substances, which constitute a technological risk factor for dairy products and above all for the health of the consumer (Licata et al. 2004). Nevertheless no studies on the incidence of high-As livestock drinking water in livestock health and its transfer to milk have been performed in Argentina. The aim of the present study was the determination of arsenic content in livestock drinking water and milk from dairy farms located in an area of high-As groundwaters, to analyse the relation between As uptake through water and its transfer to milk.

Distributional patterns of living ungulates (Mammalia: Cetartiodactyla and Perissodactyla) of the Neotropical region, the South American transition zone and Andean region

NASA Astrophysics Data System (ADS)

Absolon, Bruno Araujo; Gallo, Valéria; Avilla, Leonardo S.

2016-11-01

To recognize the distributional patterns of living ungulates in the Neotropical region, the South American transition zone, and Andean region using the panbiogeographical method of track analysis, and to attempt to correlate these patterns with geological history. The distribution of 24 species of living ungulates (in the families Camelidae, Cervidae, Tapiridae and Tayassuidae) was studied by the panbiogeographical method of track analysis. It was performed using distributional data acquired from literature and databases of scientific institutions. Individual tracks were obtained for each species by plotting locality records on maps and connecting them by minimum-spanning trees. Generalized tracks were determined from the spatial overlap between individual tracks, indicating a common history. The intersection between generalized tracks defined a biogeographic node, implying that these locations are biogeographic composites resulting from different ancestral biotas coming into spatial contact, possibly at different geologic times. The superposition of the 24 individual tracks resulted in five generalized tracks (GTs): GT1, Mesoamerican/Choco (composed of Mazama pandora, Mazama temama, Odoicoileus virginianus and Tapirus bairdii); GT2, Northern Andes (Mazama rufina, Pudu mephistophiles and Tapirus pinchaque); GT3, Central Andes (Hippocamelus antisensis, Lama guanicoe, Mazama chunyi and Vicugna vicugna); GT4, Chilean Patagonia (Hippocamelus bisulcus and Pudu puda); and GT5, Chaco/Central west Brazil (Blastocerus dichotomus, Catagonus wagneri and Ozotocerus bezoarticus). The biogeographic node was found in the Northwestern Colombia. The geological events such as tectonism and volcanism that occurred through the Neogene and mainly in the Pleistocene caused fragmentation, diversification and endemism of biota. The biogeographic node in Colombia occurred within a zone of convergence. This node emphasized the complexity of the area and it contains biotic elements with different origins, which represent a special condition for the establishment of priority conservation areas.

Melliferous insects and the uses assigned to their products in the northern Yungas of Salta, Argentina.

PubMed

Flores, Fabio Fernando; Hilgert, Norma Inés; Lupo, Liliana Concepción

2018-04-11

The order Hymenoptera comprises melliferous insects (bees, wasps and bumblebees); among them, stingless bees comprise a diverse group of eusocial insects present in tropical and subtropical areas. Of a total of approximately 500 species, 400 are found in the Neotropics. On the continent of America, before the introduction of Apis mellifera, these insects represented the main source of honey and wax. In Argentina, ethnobiological investigations had been carried out on this group of insects, principally in the Atlantic Forest and Chaco regions. Out of a total of 33 species, only 14 were recorded for use or breeding. In the Yungas, however, there are no ethnobiological studies analyzing this group of species, although the use of their products is mentioned in different ethnobotanical works. This paper studies the knowledge and uses of melliferous insects by the inhabitants of the village of Baritú and surrounding. Information on location, management and duties assigned (e.g., preparation and administration) to deal with bee products like honey, pollen, wax and propolis was obtained through semi-structured interviews. Besides, reference material was collected to identify melliferous insects known and used in the region. Fifteen ethnospecies were identified and grouped locally according to their defensive behavior. The culturally most important species is the stingless bee Plebeia sp. nov.-mansita-, in terms of frequency of citations and diversity of uses, and among those that sting, the honeybee Apis mellifera-extranjera-. Honey, pollen, wax, and propolis of Plebeia sp. nov. had the highest current frequency of use. Honey is used in food (incorporated at pure state, as a complement and in drinks), as nutraceutical food and in medicinal preparations. In addition, it is an important resource for marketing during the warm season, infusions being the main mode of administration. Pollen is used as a supplement for food and alcoholic drinks, wax mainly in candle making, and propolis. The data obtained in this study complements the information available in ethnobotanical studies carried out in the region. The present study is the first on melliferous insects in the area. A new species of stingless bee the genus Plebeia was registered, and it was observed that the known distribution of others has increased.

Disentangling the effects of shrubs and herbivores on tree regeneration in a dry Chaco forest (Argentina).

PubMed

Tálamo, Andrés; Barchuk, Alicia H; Garibaldi, Lucas A; Trucco, Carlos E; Cardozo, Silvana; Mohr, Federico

2015-07-01

Successful persistence of dry forests depends on tree regeneration, which depends on a balance of complex biotic interactions. In particular, the relative importance and interactive effects of shrubs and herbivores on tree regeneration are unclear. In a manipulative study, we investigated if thornless shrubs have a direct net effect, an indirect positive effect mediated by livestock, and/or an indirect negative effect mediated by small vertebrates on tree regeneration of two key species of Chaco forest (Argentina). In a spatial association study, we also explored the existence of net positive interactions from thorny and thornless shrubs. The number of Schinopsis lorentzii seedlings was highest under artificial shade with native herbivores and livestock excluded. Even excluding livestock, no seedlings were found with natural conditions (native herbivores present with natural shade or direct sunlight) at the end of the experiment. Surprisingly, seedling recruitment was not enhanced under thornless shrubs, because there was a complementary positive effect of shade and interference. Moreover, thornless shrubs had neither positive nor negative effects on regeneration of S. lorentzii. Regeneration of Aspidosperma quebracho-blanco was minimal in all treatments. In agreement with the experiment, spatial distributions of saplings of both tree species were independent of thornless shrubs, but positively associated with thorny shrubs. Our results suggest that in general thornless shrubs may have a negligible effect and thorny shrubs a net positive effect on tree regeneration in dry forests. These findings provide a conceptual framework for testing the impact of biotic interactions on seedling recruitment in other dry forests.

87Sr/86Sr sourcing of ponderosa pine used in Anasazi great house construction at Chaco Canyon, New Mexico

USGS Publications Warehouse

Reynolds, Amanda C.; Betancourt, Julio L.; Quade, Jay; Patchett, P. Jonathan; Dean, Jeffery S.; Stein, John

2005-01-01

Previous analysis of 87Sr/86Sr ratios shows that 10th through 12th century Chaco Canyon was provisioned with plant materials that came from more than 75 km away. This includes (1) corn (Zea mays) grown on the eastern flanks of the Chuska Mountains and floodplain of the San Juan River to the west and north, and (2) spruce (Picea sp.) and fir (Abies sp.) beams from the crest of the Chuska and San Mateo Mountains to the west and south. Here, we extend 87Sr/86Sr analysis to ponderosa pine (Pinus ponderosa) prevalent in the architectural timber at three of the Chacoan great houses (Pueblo Bonito, Chetro Ketl, Pueblo del Arroyo). Like the architectural spruce and fir, much of the ponderosa matches the 87Sr/86Sr ratios of living trees in the Chuska Mountains. Many of the architectural ponderosa, however, have similar ratios to living trees in the La Plata and San Juan Mountains to the north and Lobo Mesa/Hosta Butte to the south. There are no systematic patterns in spruce/fir or ponderosa provenance by great house or time, suggesting the use of stockpiles from a few preferred sources. The multiple and distant sources for food and timber, now based on hundreds of isotopic values from modern and archeological samples, confirm conventional wisdom about the geographic scope of the larger Chacoan system. The complexity of this procurement warns against simple generalizations based on just one species, a single class of botanical artifact, or a few isotopic values.

87Sr/86Sr sourcing of ponderosa pine used in Anasazi great house construction at Chaco Canyon, New Mexico

USGS Publications Warehouse

Reynolds, A.C.; Betancourt, J.L.; Quade, Jay; Patchett, P.J.; Dean, J.S.; Stein, J.

2005-01-01

Previous analysis of 87Sr/86Sr ratios shows that 10th through 12th century Chaco Canyon was provisioned with plant materials that came from more than 75 km away. This includes (1) corn (Zea mays) grown on the eastern flanks of the Chuska Mountains and floodplain of the San Juan River to the west and north, and (2) spruce (Picea sp.) and fir (Abies sp.) beams from the crest of the Chuska and San Mateo Mountains to the west and south. Here, we extend 87Sr/86Sr analysis to ponderosa pine (Pinus ponderosa) prevalent in the architectural timber at three of the Chacoan great houses (Pueblo Bonito, Chetro Ketl, Pueblo del Arroyo). Like the architectural spruce and fir, much of the ponderosa matches the 87Sr/86Sr ratios of living trees in the Chuska Mountains. Many of the architectural ponderosa, however, have similar ratios to living trees in the La Plata and San Juan Mountains to the north and Lobo Mesa/Hosta Butte to the south. There are no systematic patterns in spruce/fir or ponderosa provenance by great house or time, suggesting the use of stockpiles from a few preferred sources. The multiple and distant sources for food and timber, now based on hundreds of isotopic values from modern and archeological samples, confirm conventional wisdom about the geographic scope of the larger Chacoan system. The complexity of this procurement warns against simple generalizations based on just one species, a single class of botanical artifact, or a few isotopic values. ?? 2005 Elsevier Ltd. All rights reserved.

Molecular phylogeography of the Chagas' disease vector Triatoma infestans in Argentina

PubMed Central

Pérez de Rosas, A R; Segura, E L; García, B A

2011-01-01

Triatoma infestans is the main vector of Chagas' disease in South America between latitudes 10°S and 46°S. A multilocus microsatellite data set of 836 individuals from 27 populations of T. infestans, from all its range of distribution in Argentina, was analyzed. Our results favor the hypothesis of two independent migration events of colonization in Argentina and secondary contacts. The majority of the populations of the western provinces of Catamarca, La Rioja, San Juan and the west of Cordoba province, had almost no shared ancestry with the rest of the populations analyzed. Probably those populations, belonging to localities close to the Andean region, could have been established by the dispersal line of T. infestans that would have arrived to Argentina through the Andes, whereas most of the rest of the populations analyzed may have derived from the dispersal line of T. infestans in non-Andean lowlands. Among them, those from the provinces of Formosa, Chaco, Santiago del Estero and Santa Fe shared different percentages of ancestry and presented lower degree of genetic differentiation. The migratory movement linked to regional economies and possibly associated with passive dispersal, would allow a higher genetic exchange among these populations of T. infestans. This study, using microsatellite markers, provides a new approach for evaluating the validity of the different hypotheses concerning the evolutionary history of this species. Two major lineages of T. infestans, an Andean and non-Andean, are suggested. PMID:21224874

Modeling of skeletal members using polyurethane foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sena, J.M.F.; Weaver, R.W.

1983-11-01

At the request of the University of New Mexico's Maxwell Museum of Anthropology, members of the Plastic Section in the Process Development Division at SNLA undertook the special project of the Chaco Lady. The project consisted of polyurethane foam casting of a disinterred female skull considered to be approximately 1000 years old. Rubber latex molds, supplied by the UNM Anthropology Department, were used to produce the polymeric skull requested. The authors developed for the project a modified foaming process which will be used in future polyurethane castings of archaeological artifacts and contemporary skeletal members at the University.

Revisiting the Diego Blood Group System in Amerindians: Evidence for Gene-Culture Comigration.

PubMed

Bégat, Christophe; Bailly, Pascal; Chiaroni, Jacques; Mazières, Stéphane

2015-01-01

Six decades ago the DI*A allele of the Diego blood group system was instrumental in proving Native American populations originated from Siberia. Since then, it has received scant attention. The present study was undertaken to reappraise distribution of the DI*A allele in 144 Native American populations based on current knowledge. Using analysis of variance tests, frequency distribution was studied according to geographical, environmental, and cultural parameters. Frequencies were highest in Amazonian populations. In contrast, DI*A was undetectable in subarctic, Fuegian, Panamanian, Chaco and Yanomama populations. Closer study revealed a correlation that this unequal distribution was correlated with language, suggesting that linguistic divergence was a driving force in the expansion of DI*A among Native Americans. The absence of DI*A in circumpolar Eskimo-Aleut and Na-Dene speakers was consistent with a late migratory event confined to North America. Distribution of DI*A in subtropical areas indicated that gene and culture exchanges were more intense within than between ecozones. Bolstering the utility of classical genetic markers in biological anthropology, the present study of the expansion of Diego blood group genetic polymorphism in Native Americans shows strong evidence of gene-culture comigration.

Trade-offs between cattle production and bird conservation in an agricultural frontier of the Gran Chaco of Argentina.

PubMed

Mastrangelo, Matias E; Gavin, Michael C

2012-12-01

Intensification of food production in tropical landscapes in the absence of land-use planning can pose a major threat to biological diversity. Decisions on whether to spatially integrate or segregate lands for production and conservation depend in part on the functional relations between biological diversity and agricultural productivity. We measured diversity, density, and species composition of birds along a gradient of production intensification on an agricultural frontier of the Argentine Chaco, where dry tropical forests are cleared for cattle production. Bird species diversity in intact forests was higher than in any type of cattle-production system. Bird species richness decreased nonlinearly as cattle yield increased. Intermediate-intensity silvopastoral systems, those in which forest understory is selectively cleared to grow pastures of non-native plants beneath the tree canopy, produced 80% of the mean cattle yield obtained in pastures on cleared areas and were occupied by 70-90% of the number of bird species present in the nearest forest fragments. Densities of >50% of bird species were significantly lower in open pastures than in silvopastoral systems. Therefore, intermediate-intensity silvopastoral systems may have the greatest potential to sustain cattle yield and conserve a large percentage of bird species. However, compared with low-intensity production systems, in which forest structure and extent were intact, intermediate-intensity silvopastoral systems supported significantly fewer forest-restricted bird species and fewer frugivorous birds. These data suggest that the integration of production and conservation through intermediate-intensity silvopastoral systems combined with the protection of forest fragments may be required to maintain cattle yield, bird diversity, and conservation of forest-restricted species in this agricultural frontier. ©2012 Society for Conservation Biology.

Exploring the biological activity of condensed tannins and nutritional value of tree and shrub leaves from native species of the Argentinean Dry Chaco.

PubMed

García, Elisa M; Cherry, Nicole; Lambert, Barry D; Muir, James P; Nazareno, Mónica A; Arroquy, Jose I

2017-11-01

Tropical tree or shrub leaves are an important source of nutrients for ruminants and a potential source of biologically active compounds that may affect ruminal metabolism of nutrients. Therefore, eight woody species from the native flora of Argentinean Dry Chaco, rich in secondary compounds such as condensed tannins (CT), were assessed for their nutritional value, CT fractions and in vitro true digestibility of dry matter, as well as biological activity (BA). Differences among species were found in contents of total phenol, protein-precipitating phenols (PPP), bound proteins to PPP (BP) and BP/PPP (P < 0.0001). The BP/PPP ratio reveals differences among species in potential BA as indicated by protein precipitation. The major CT of each species were isolated and purified for use as a standard. Although Schinopsis balansae had the most (P ≤ 0.05) total CT (19.59% DM), Caesalpinia paraguariensis had greater (P ≤ 0.05) BA with the most PPP (530.21% dry matter). Larrea divaricata, at 0.97, followed by Acacia aroma, at 0.89, had CT with the highest (P ≤ 0.05) BP/PPP ratios, followed by Prosopis alba (0.59). There were differences in nutritive value and bioactivity among species. Those with the greatest CT were not necessarily those with the most BA. Caesalpinia paraguariensis, S. balansae and L. divaricata were the most promising species as native forage CT sources. Cercidiurm praecox (20.87% CP; 18.14% acid detergent fiber) and Prosopis nigra (19.00% CP; 27.96% acid detergent fiber) showed the best (P ≤ 0.05) nutritive values. According to their nutritive traits, these species might be complementary in grass-based ruminant diets. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Health evaluation of free-ranging and captive blue-fronted Amazon parrots (Amazona aestiva) in the Gran chaco, Bolivia.

PubMed

Deem, Sharon L; Noss, Andrew J; Cuéllar, Rosa Leny; Karesh, William B

2005-12-01

Bolivia has a total of 47 species of Psittacidae, seven of which have been identified in our study site, the semiarid Gran Chaco of the Isoso. One species, the blue-fronted parrot (Amazona aestiva), is frequently captured by local Isoseño Guaraní Indians for exploitation on the national and international market. These birds are often temporarily housed in small villages under unhygienic conditions with poultry and other domestic species. On occasion, these parrots escape back to the wild. Additionally, many of these birds are kept as pets or are used to lure wild. parrots within slingshot range for subsequent capture. In this study, we evaluated the health status, including the level of exposure to selected infectious agents, in the wild-caught captive birds and free-ranging birds. Physical examinations were performed, and blood was collected, from 54 live birds (20 captive and 34 free-ranging). Feces were collected from 15 birds (seven captive and eight free-ranging). Necropsies were also performed on four recently dead wild-caught birds. On serologic testing, no birds were found to have antibodies to avian influenza virus, Chlamydophila psittaci, infectious bronchitis virus, infectious bursal disease virus, infectious laryngotracheitis virus, Marek's disease virus, paramyxovirus-1, paramyxovirus-2, paramyxovirus-3, polyomavirus, eastern equine encephalitis virus, western equine encephalitis virus, or Venezuelan equine encephalitis virus. Positive antibody titers were found for psittacine herpesvirus (8/44, 18.2%), Aspergillus spp. (3/51, 5.9%), and Salmonella pullorum (33/49, 67.3%). All three of the birds that tested antibody positive for Aspergillus spp. were captive, whereas six of the eight and 15 of the 33 birds that tested positive for psittacine herpesvirus and S. pullorum, respectively, were wild.

The disjunct pattern of the Neotropical harvestman Discocyrtus dilatatus (Gonyleptidae) explained by climate-driven range shifts in the Quaternary: Paleodistributional and molecular evidence

PubMed Central

Vergara, Julia; González-Ittig, Raúl E.; Vaschetto, Luis M.; Gardenal, Cristina N.

2017-01-01

The disjunct distribution of the harvestman Discocyrtus dilatatus (Opiliones, Gonyleptidae) is used as a case study to test the hypothesis of a trans-Chaco Pleistocene paleobridge during range expansion stages. This would have temporarily connected humid regions (‘Mesopotamia’ in northeastern Argentina, and the ‘Yungas’ in the northwest, NWA) in the subtropical and temperate South American lowlands. The present study combines two independent approaches: paleodistributional reconstruction, using the Species Distribution Modeling method MaxEnt and projection onto Quaternary paleoclimates (6 kya, 21 kya, 130 kya), and phylogeographic analyses based on the cytochrome oxidase subunit I molecular marker. Models predict a maximal shrinkage during the warm Last Interglacial (130 kya), and the rise of the hypothesized paleobridge in the Last Glacial Maximum (21 kya), revealing that cold-dry stages (not warm-humid ones, as supposed) enabled the range expansion of this species. The disjunction was formed in the mid-Holocene (6 kya) and is intensified under current conditions. The median-joining network shows that NWA haplotypes are peripherally related to different Mesopotamian lineages; haplotypes from Santa Fe and Córdoba Provinces consistently occupy central positions in the network. According to the dated phylogeny, Mesopotamia-NWA expansion events would have occurred in the last glacial period, in many cases closely associated to the Last Glacial Maximum, with most divergence events occurring shortly thereafter. Only two (out of nine) NWA haplotypes are shared with Mesopotamian localities. A single, presumably relictual NWA haplotype was found to have diverged much earlier, suggesting an ancient expansion event not recoverable by the paleodistributional models. Different measures of sequence statistics, genetic diversity, population structure and history of demographic changes are provided. This research offers the first available evidence for the historical origin of NWA disjunct populations of a Mesopotamian harvestman. PMID:29141036

A Novel Candidate Region for Genetic Adaptation to High Altitude in Andean Populations

PubMed Central

Lippold, Sebastian; de Filippo, Cesare; Tang, Kun; López Herráez, David; Li, Jing; Stoneking, Mark

2015-01-01

Humans living at high altitude (≥2,500 meters above sea level) have acquired unique abilities to survive the associated extreme environmental conditions, including hypoxia, cold temperature, limited food availability and high levels of free radicals and oxidants. Long-term inhabitants of the most elevated regions of the world have undergone extensive physiological and/or genetic changes, particularly in the regulation of respiration and circulation, when compared to lowland populations. Genome scans have identified candidate genes involved in altitude adaption in the Tibetan Plateau and the Ethiopian highlands, in contrast to populations from the Andes, which have not been as intensively investigated. In the present study, we focused on three indigenous populations from Bolivia: two groups of Andean natives, Aymara and Quechua, and the low-altitude control group of Guarani from the Gran Chaco lowlands. Using pooled samples, we identified a number of SNPs exhibiting large allele frequency differences over 900,000 genotyped SNPs. A region in chromosome 10 (within the cytogenetic bands q22.3 and q23.1) was significantly differentiated between highland and lowland groups. We resequenced ~1.5 Mb surrounding the candidate region and identified strong signals of positive selection in the highland populations. A composite of multiple signals like test localized the signal to FAM213A and a related enhancer; the product of this gene acts as an antioxidant to lower oxidative stress and may help to maintain bone mass. The results suggest that positive selection on the enhancer might increase the expression of this antioxidant, and thereby prevent oxidative damage. In addition, the most significant signal in a relative extended haplotype homozygosity analysis was localized to the SFTPD gene, which encodes a surfactant pulmonary-associated protein involved in normal respiration and innate host defense. Our study thus identifies two novel candidate genes and associated pathways that may be involved in high-altitude adaptation in Andean populations. PMID:25961286

Assessment of processes controlling the regional distribution of fluoride and arsenic in groundwater of the Pampeano Aquifer in the Del Azul Creek basin (Argentina)

NASA Astrophysics Data System (ADS)

Zabala, M. E.; Manzano, M.; Vives, L.

2016-10-01

Groundwater in the upper 50 m of the Pampeano Aquifer in the Del Azul Creek basin (Argentina) has F and As contents above the WHO safe drinking levels. This basin is situated to the SE of the Chaco-Pampean plain, in Buenos Aires Province. The Pampeano Aquifer is a major water source for all uses. The aim of the study is to assess the primary processes controlling the regional distribution of F and As in the most exploited part of the aquifer. The study involved sampling for chemical and isotopic analyses, interpretation of data with different methods (diagrams, bivariate analyses, mineral saturation states, Principal Component Analysis) and deduction of leading processes. Information about aquifer mineralogy and hydrogeochemical processes involved in F and As solubilization in the aquifer has been taken from previous works of the same and other authors. Groundwater salinity increases to the NE, in the direction of the regional groundwater flow. Chemical types evolve from Ca/Mg-HCO3 in the upper part of the basin, to Na-HCO3 in the middle part and to Na-ClSO4 and Na-Cl in the lower part. The regional distribution of F is controlled by hydrogeochemical processes. The distribution of As is controlled by two types of processes dominating in different areas: hydrogeochemical controls prevail in the low to moderately mineralized groundwater of the middle and lower parts of the basin; hydrogeological controls lead to the NE of the lower basin and beyond it. In the last zone there are abundant lagoons and seasonal flooding is frequent, making evapoconcentration an important process for groundwater mineralization. The main hydrogeochemical processes involved in both F and As distribution are cation exchange, with Na release and Ca uptake, carbonate dissolution and pH increase. Arsenic release induced by redox processes may play to the NE, but its results would be masked by the effect of evaporation.

Illegal hunting cases detected with molecular forensics in Brazil

PubMed Central

2012-01-01

Background Illegal hunting is one of the major threats to vertebrate populations in tropical regions. This unsustainable practice has serious consequences not only for the target populations, but also for the dynamics and structure of tropical ecosystems. Generally, in cases of suspected illegal hunting, the only evidence available is pieces of meat, skin or bone. In these cases, species identification can only be reliably determined using molecular technologies. Here, we reported an investigative study of three cases of suspected wildlife poaching in which molecular biology techniques were employed to identify the hunted species from remains of meat. Findings By applying cytochrome b (cyt-b) and cytochrome oxidase subunit I (COI) molecular markers, the suspected illegal poaching was confirmed by the identification of three wild species, capybara (Hydrochoerus hydrochaeris), Chaco Chachalaca (Ortalis canicollis) and Pampas deer (Ozotoceros bezoarticus). In Brazil, hunting is a criminal offense, and based on this evidence, the defendants were found guilty and punished with fines; they may still be sentenced to prison for a period of 6 to 12 months. Conclusions The genetic analysis used in this investigative study was suitable to diagnose the species killed and solve these criminal investigations. Molecular forensic techniques can therefore provide an important tool that enables local law enforcement agencies to apprehend illegal poachers. PMID:22863070

[Vectorial and congenital transmission of Trypanosoma cruzi in Las Lomitas, Formosa].

PubMed

Sosa-Estani, Sergio; Dri, Lucía; Touris, Cecilia; Abalde, Sergio; Dell'arciprete, Ana; Braunstein, Jose

2009-01-01

Chagas disease, caused by Trypanosoma cruzi, is a major cause of morbidity and mortality in Latin America. The objective of this study was to describe the rate of infestation in four aboriginal communities in Las Lomitas (Great Chaco Region), Formosa, Argentina; the rate of infection in children residing in these communities, in blood donors and in pregnant women who received care at the Hospital Las Lomitas, as well as the rate of congenital infection in children born to women infected during the study period. The rate of infestation of 172 households evaluated in 2006 reached 32%. Prevalence of infection among 445 people was 17.5% and in children under 5 years old it was 8.6%. The rate of infection reached 18.6% in blood donors and 29.1% in pregnant women. The rate of infection among 47 children born to infected women, and living in residences under vectorial surveillance was 17.0%. These infections were considered as congenital. This study showed indexes compatible with active vectorial transmission at the beginning. After vectorial control with insecticides the infestation rate has been reduced to 3.3%. The local health system has introduced high impact procedures of primary and secondary prevention in order to prevent new cases and to treat infected people.

Possible impacts of early-11th-, middle-12th-, and late-13th-century droughts on western Native Americans and the Mississippian Cahokians

USGS Publications Warehouse

Benson, L.V.; Berry, M.S.; Jolie, E.A.; Spangler, J.D.; Stahle, D.W.; Hattori, E.M.

2007-01-01

One or more of three intense and persistent droughts impacted some Native American cultures in the early-11th, middle-12th and late-13th centuries, including the Anasazi, Fremont, Lovelock, and Mississippian (Cahokian) prehistorical cultures. Tree-ring-based reconstructions of precipitation and temperature indicate that warm drought periods occurred between AD 990 and 1060, AD 1135 and 1170, and AD 1276 and 1297. These droughts occurred during minima in the Pacific Decadal Oscillation and may have been associated with positive values of the Atlantic Multidecadal Oscillation. Each of the Native American cultures was supported, to a greater or lesser degree, by precipitation-dependent resources. Both the Four Corners region and Cahokia were sites of intense growth between about AD 1050 and 1130, and by AD 1150, cultures in both regions were undergoing stress. By AD 1300 the Anasazi and Fremont cultures had collapsed and their residual populations had either left their homelands or withered. In the case of Fremont populations, the AD 990-1060 drought may have had the greatest impact. This drought also may have affected the Anasazi, for it was at the end of this drought that some people from Chaco migrated to the San Juan River valley and founded the Salmon Ruin great house. Detailed data do not exist on the number of Lovelock habitation sites or populations over time; however, Lovelock populations appear to have retreated from the western Great Basin to California by AD 1300 or shortly thereafter.

Sedimentology of the mid-Carboniferous fill of the Olta paleovalley, eastern Paganzo Basin, Argentina: Implications for glaciation and controls on diachronous deglaciation in western Gondwana during the late Paleozoic Ice Age

NASA Astrophysics Data System (ADS)

Moxness, Levi D.; Isbell, John L.; Pauls, Kathryn N.; Limarino, Carlos O.; Schencman, Jazmin

2018-07-01

Both global and regional climate drivers contributed to glaciation during the late Paleozoic Ice Age (LPIA). However, the transition from icehouse to greenhouse conditions was asynchronous across Gondwana suggesting that, in some cases, regional controls played a significant role in deglaciation. Of particular interest to understanding changing LPIA climatic conditions, is the eastern Paganzo Basin. This region was flanked by ice centers in the Precordilleran and Sierras Pampeanas regions of Argentina on the west, and major ice sheets in the Paraná, Chaco-Paraná, and Sauce Grande basins to the east, all of which resided between ∼40 and 65° S latitude. Hypotheses on the occurrence of ice in the eastern Paganzo Basin are based on interpretations of the narrow, steep-walled, Olta-Malanzán paleovalley as carved by an alpine glacier or by an outlet glacier draining an eastern ice sheet, and that glaciers deposited coarse clastics within the paleovalley. However, we found no evidence for glaciation. Rather, gravel from prograding alluvial fans/fan deltas and rock falls ponded drainage resulting in lacustrine activity in the eastern end of the valley. A transition from either subaerially or shallow subaqueously deposited sandstones to marine mudstones in the western end of the Olta paleovalley suggest a marine transgression, which, in turn, was overlain by deposits of prograding Gilbert-type deltas. Dropstones were from rock falls off valley walls and rafting by lake ice rather than from icebergs. Therefore, we conclude that the climate in western Argentina resulted from uplift induced glaciation in the Precordilleran region and along the western margin of the Paganzo Basin, and the occurrence of a precipitation shadow to the east. The disappearance of the western glaciers during the mid-Carboniferous, prior to deglaciation elsewhere at the same paleolatitude, resulted from a westward shift in the position of the active margin, collapse of the glaciated upland(s), and an expansion of the precipitation shadow across the whole of western Argentina.

Origin of Aymaras from Bolivia and their relationship with other Amerindians according to HLA genes.

PubMed

Arnaiz-Villena, A; Siles, N; Moscoso, J; Zamora, J; Serrano-Vela, J I; Gomez-Casado, E; Castro, M J; Martinez-Laso, J

2005-04-01

Aymara Amerindians from the Titicaca Lake Andean highlands are studied for HLA-A, HLA-B, HLA-DRB1 and HLA-DQB1 gene frequencies. Genetic distances, neighbour-joining and correspondence analyses are performed by using other Amerindian and worldwide populations (15384 chromosomes are studied). The HLA genetic profile of Aymaras is different from neighbouring and language-related Quechuas (Incas). Both Quechuas and Aymaras seem to present an HLA-DRB1*0901 high frequency, which is present in a very low frequency or absent in Mesoamericans (Mazatecans, Mayans) and most studied Amerindians. Moreover, it is observed a closer relatedness of Aymaras with Amerindians from the Amazon Basin and Chaco lowlands, compared to Quechuans.

Human health risk assessment with spatial analysis: study of a population chronically exposed to arsenic through drinking water from Argentina.

PubMed

Navoni, J A; De Pietri, D; Olmos, V; Gimenez, C; Bovi Mitre, G; de Titto, E; Villaamil Lepori, E C

2014-11-15

Arsenic (As) is a ubiquitous element widely distributed in the environment. This metalloid has proven carcinogenic action in man. The aim of this work was to assess the health risk related to As exposure through drinking water in an Argentinean population, applying spatial analytical techniques in addition to conventional approaches. The study involved 650 inhabitants from Chaco and Santiago del Estero provinces. Arsenic in drinking water (Asw) and urine (UAs) was measured by hydride generation atomic absorption spectrophotometry. Average daily dose (ADD), hazard quotient (HQ), and carcinogenic risk (CR) were estimated, geo-referenced and integrated with demographical data by a health composite index (HI) applying geographic information system (GIS) analysis. Asw covered a wide range of concentration: from non-detectable (ND) to 2000 μg/L. More than 90% of the population was exposed to As, with UAs levels above the intervention level of 100 μg/g creatinine. GIS analysis described an expected level of exposure lower than the observed, indicating possible additional source/s of exposure to inorganic arsenic. In 68% of the locations, the population had a HQ greater than 1, and the CR ranged between 5·10(-5) and 2,1·10(-2). An environmental exposure area through ADD geo-referencing defined a baseline scenario for space-time risk assessment. The time of residence, the demographic density and the potential health considered outcomes helped characterize the health risk in the region. The geospatial analysis contributed to delimitate and analyze the change tendencies of risk in the region, broadening the scopes of the results for a decision-making process. Copyright © 2014 Elsevier B.V. All rights reserved.

Insecticide resistance in vector Chagas disease: evolution, mechanisms and management.

PubMed

Mougabure-Cueto, Gastón; Picollo, María Inés

2015-09-01

Chagas disease is a chronic parasitic infection restricted to America. The disease is caused by the protozoa Trypanosoma cruzi, which is transmitted to human through the feces of infected triatomine insects. Because no treatment is available for the chronic forms of the disease, vector chemical control represents the best way to reduce the incidence of the disease. Chemical control has been based principally on spraying dwellings with insecticide formulations and led to the reduction of triatomine distribution and consequent interruption of disease transmission in several areas from endemic region. However, in the last decade it has been repeatedly reported the presence triatomnes, mainly Triatoma infestans, after spraying with pyrethroid insecticides, which was associated to evolution to insecticide resistance. In this paper the evolution of insecticide resistance in triatomines is reviewed. The insecticide resistance was detected in 1970s in Rhodnius prolixus and 1990s in R. prolixus and T. infestans, but not until the 2000s resistance to pyrthroids in T. infestans associated to control failures was described in Argentina and Bolivia. The main resistance mechanisms (i.e. enhanced metabolism, altered site of action and reduced penetration) were described in the T. infestans resistant to pyrethrods. Different resistant profiles were demonstrated suggesting independent origin of the different resistant foci of Argentina and Bolivia. The deltamethrin resistance in T. infestans was showed to be controlled by semi-dominant, autosomally inherited factors. Reproductive and developmental costs were also demonstrated for the resistant T. infestans. A discussion about resistance and tolerance concepts and the persistence of T. infestans in Gran Chaco region are presented. In addition, theoretical concepts related to toxicological, evolutionary and ecological aspects of insecticide resistance are discussed in order to understand the particular scenario of pyrethroid resistance in triatomines. Copyright © 2015 Elsevier B.V. All rights reserved.

Mapping the influence of the deep Nazca slab on the geometry of the 660-km discontinuity beneath stable South America

NASA Astrophysics Data System (ADS)

Bianchi, M. B. D.; Assumpcao, M.; Julià, J.

2017-12-01

The fate of the deep Nazca subducted plate is poorly mapped under stable South America. Transition zone thickness and position is greatly dependent on mantle temperature and so is influenced by the colder Nazca plate position. We use a database of 35,000 LQT deconvolved receiver function traces to image the mantle transition zone and other upper mantle discontinuities under different terranes of stable South American continent. Data from the entire Brazilian Seismographic Network database, consisting of more than 80 broadband stations supplemented by 35 temporary stations deployed in west Brazil, Argentina, Paraguay, Bolivia and Uruguay were processed. Our results indicates that upper mantle velocities are faster than average under stable cratons and that most of the discontinuities are positioned with small variations in respect to nominal depths, except in places were the Nazca plate interacts with the transition zone. Under the Chaco-Pantanal basin the Nazca plate appears to be trapped in the transition zone for more than 1000 km with variations of up to 30 km in 660 km discontinuity topography under this region consistent with global tomographic models. Additional results obtained from SS precursor analysis of South Sandwich Islands teleseismic events recorded at USArray stations indicates that variations of transition zones thickness occur where the Nazca plate interacts with the upper mantle discontinuities in the northern part of Stable South American continent.

Chagas disease vector control and Taylor's law

PubMed Central

Rodríguez-Planes, Lucía I.; Gaspe, María S.; Cecere, María C.; Cardinal, Marta V.

2017-01-01

Background Large spatial and temporal fluctuations in the population density of living organisms have profound consequences for biodiversity conservation, food production, pest control and disease control, especially vector-borne disease control. Chagas disease vector control based on insecticide spraying could benefit from improved concepts and methods to deal with spatial variations in vector population density. Methodology/Principal findings We show that Taylor's law (TL) of fluctuation scaling describes accurately the mean and variance over space of relative abundance, by habitat, of four insect vectors of Chagas disease (Triatoma infestans, Triatoma guasayana, Triatoma garciabesi and Triatoma sordida) in 33,908 searches of people's dwellings and associated habitats in 79 field surveys in four districts in the Argentine Chaco region, before and after insecticide spraying. As TL predicts, the logarithm of the sample variance of bug relative abundance closely approximates a linear function of the logarithm of the sample mean of abundance in different habitats. Slopes of TL indicate spatial aggregation or variation in habitat suitability. Predictions of new mathematical models of the effect of vector control measures on TL agree overall with field data before and after community-wide spraying of insecticide. Conclusions/Significance A spatial Taylor's law identifies key habitats with high average infestation and spatially highly variable infestation, providing a new instrument for the control and elimination of the vectors of a major human disease. PMID:29190728

Where do these bugs come from? Phenotypic structure of Triatoma infestans populations after control interventions in the Argentine Chaco

PubMed Central

Gaspe, María Sol; Provecho, Yael Mariana; Piccinali, Romina Valeria; Gürtler/, Ricardo Esteban

2015-01-01

House re-invasion by native triatomines after insecticide-based control campaigns represents a major threat for Chagas disease vector control. We conducted a longitudinal intervention study in a rural section (Area III, 407 houses) of Pampa del Indio, northeastern Argentina, and used wing geometric morphometry to compare pre-spray and post-spray (re-infestant bugs) Triatoma infestans populations. The community-wide spraying with pyrethroids reduced the prevalence of house infestation by T. infestans from 31.9% to < 1% during a four-year follow-up, unlike our previous studies in the neighbouring Area I. Two groups of bug collection sites differing in wing shape variables before interventions (including 221 adults from 11 domiciles) were used as a reference for assigning 44 post-spray adults. Wing shape variables from post-spray, high-density bug colonies and pre-spray groups were significantly different, suggesting that re-infestant insects had an external origin. Insects from one house differed strongly in wing shape variables from all other specimens. A further comparison between insects from both areas supported the existence of independent re-infestation processes within the same district. These results point to local heterogeneities in house re-infestation dynamics and emphasise the need to expand the geographic coverage of vector surveillance and control operations to the affected region. PMID:25946158

Analysis of Population Substructure in Two Sympatric Populations of Gran Chaco, Argentina

PubMed Central

Sevini, Federica; Yao, Daniele Yang; Lomartire, Laura; Barbieri, Annalaura; Vianello, Dario; Ferri, Gianmarco; Moretti, Edgardo; Dasso, Maria Cristina; Garagnani, Paolo; Pettener, Davide; Franceschi, Claudio; Luiselli, Donata; Franceschi, Zelda Alice

2013-01-01

Sub-population structure and intricate kinship dynamics might introduce biases in molecular anthropology studies and could invalidate the efforts to understand diseases in highly admixed populations. In order to clarify the previously observed distribution pattern and morbidity of Chagas disease in Gran Chaco, Argentina, we studied two populations (Wichí and Criollos) recruited following an innovative bio-cultural model considering their complex cultural interactions. By reconstructing the genetic background and the structure of these two culturally different populations, the pattern of admixture, the correspondence between genealogical and genetic relationships, this integrated perspective had the power to validate data and to link the gap usually relying on a singular discipline. Although Wichí and Criollos share the same area, these sympatric populations are differentiated from the genetic point of view as revealed by Non Recombinant Y Chromosome genotyping resulting in significantly high Fst values and in a lower genetic variability in the Wichí population. Surprisingly, the Amerindian and the European components emerged with comparable amounts (20%) among Criollos and Wichí respectively. The detailed analysis of mitochondrial DNA showed that the two populations have as much as 87% of private haplotypes. Moreover, from the maternal perspective, despite a common Amerindian origin, an Andean and an Amazonian component emerged in Criollos and in Wichí respectively. Our approach allowed us to highlight that quite frequently there is a discrepancy between self-reported and genetic kinship. Indeed, if self-reported identity and kinship are usually utilized in population genetics as a reliable proxy for genetic identity and parental relationship, in our model populations appear to be the result not only and not simply of the genetic background but also of complex cultural determinants. This integrated approach paves the way to a rigorous reconstruction of demographic and cultural history as well as of bioancestry and propensity to diseases of Wichí and Criollos. PMID:23717528

House Reinfestation With Triatoma infestans (Hemiptera: Reduviidae) After Community-Wide Spraying With Insecticides in the Argentine Chaco: A Multifactorial Process.

PubMed

Provecho, Yael M; Gaspe, M Sol; Fernández, M Del Pilar; Gürtler, Ricardo E

2017-05-01

We investigated the dynamics and underlying causes of house (re)infestation with Triatoma infestans (Klug 1834) after a community-wide residual spraying with pyrethroids in a well-defined rural section of Pampa del Indio municipality (northeastern Argentina) over a 4-yr period. House infestation was assessed by timed manual searches, during insecticide applications, and by opportunistic householders' bug collections. All reinfested houses were selectively re-sprayed with insecticides. The resident population comprised Qom (66.6%) and Creole (33.4%) households, whose sociodemographic profiles differed substantially. The prevalence of house infestation dropped, less than expected, from 20.5% at baseline to 5.0% at 14 months postspraying (MPS), and then fluctuated between 0.8 and 4.2% over 21-51 MPS. Postspraying house infestation was positively and highly significantly associated with prespraying infestation. Most of the foci detected over 14-21 MPS were considered persistent (residual), some of which were moderately resistant to pyrethroids and were suppressed with malathion. Infestation patterns over 27-51 MPS suggested bug invasion from internal or external foci, but the sources of most findings were unaccounted for. Local spatial analysis identified two hotspots of postspraying house infestation. Using multimodel inference with model averaging, we corroborated that baseline domestic infestation was closely related to refuge availability, housing quality, and occurrence of peridomestic infestation. The diminished effectiveness of single pyrethroid treatments, partly attributable to moderate resistance compounded with rather insensitive vector detection methods and poor housing conditions, contributed to vector persistence. Improved control strategies combined with broad social participation are needed for the sustainable elimination of vector-borne human Chagas disease from the Gran Chaco. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Serologic evidence of canine parvovirus in domestic dogs, wild carnivores, and marsupials in the Argentinean Chaco.

PubMed

Orozco, María Marcela; Miccio, Luciano; Enriquez, Gustavo Fabián; Iribarren, Fabián Eduardo; Gürtler, Ricardo Esteban

2014-09-01

The transmission of pathogens between domestic dogs and generalist wildlife species may be modified by environmental degradation, biodiversity losses, host densities, and increased contact rates in remnant forest patches. A serologic survey of canine parvovirus (CPV) in rural domestic dogs and wild mammals was conducted in two neighboring rural areas (disturbed and protected) from Pampa del Indio, northeastern Argentina, between 2008 and 2011. A total of 174 domestic dogs and 26 wild mammals-4 crab-eating foxes (Cerdocyon thous), 3 crab-eating raccoons (Procyon cancrivorus), 17 white-eared opossums (Didelphis albiventris), and 2 gray four-eyed opossums (Philander opossum)-were examined for antibodies to CPV using a hemagglutination inhibition assay. Domestic dogs were numerous and their movements unrestricted. The main function of dogs differed significantly between areas, with more dogs used for herding or hunting around the protected area. The seroprevalence of antibodies to CPV in dogs from both areas was very high (93.9-94.6%) and increased steeply with age. Nearly all carnivores and marsupials showed high exposure to CPV. Although a higher exposure to CPV was expected in wild mammals from disturbed areas as a result of enhanced contact between dogs and wildlife, no significant differences were found between areas. To the authors' knowledge, this study is the first to document exposure to CPV of free-ranging Pr. cancrivorus, D. albiventris, and Ph. opossum, and include a detailed demographic study of the domestic dog populations living in the area. This study highlights that dogs and wildlife have potential opportunities for contact and shows that the edges of the protected area may be as suitable as other fragmented areas for the transmission of CPV. Rural domestic dogs may pose serious threats to the health and conservation of wild carnivores in both disturbed and protected areas, especially in the Gran Chaco, where habitat fragmentation is severely increasing.

Seasonal variation of temporal niche in wild owl monkeys (Aotus azarai azarai) of the Argentinean Chaco: a matter of masking?

PubMed

Erkert, Hans G; Fernandez-Duque, Eduardo; Rotundo, Marcelo; Scheideler, Angelika

2012-07-01

Among the more than 40 genera of anthropoid primates (monkeys, apes, and humans), only the South American owl monkeys, genus Aotus, are nocturnal. However, the southernmostly distributed species, Aotus azarai azarai, of the Gran Chaco may show considerable amounts of its 24-h activity during bright daylight. Due to seasonal changes in the duration of photophase and climatic parameters in their subtropical habitat, the timing and pattern of their daily activity are expected to show significant seasonal variation. By quantitative long-term activity recordings with Actiwatch AW4 accelerometer data logger devices of 10 wild owl monkeys inhabiting a gallery forest in Formosa, Argentina, the authors analyzed the seasonal variation in the temporal niche and activity pattern resulting from entrainment and masking of the circadian activity rhythm by seasonally and diurnally varying environmental factors. The owl monkeys always displayed a distinct bimodal activity pattern, with prominent activity bouts and peaks during dusk and dawn. Their activity rhythm showed distinct lunar and seasonal variations in the timing and daily pattern. During the summer, the monkeys showed predominantly crepuscular/nocturnal behavior, and a crepuscular/cathemeral activity pattern with similar diurnal and nocturnal activity levels during the cold winter months. The peak times of the evening and morning activity bouts were more closely related to the times of sunset and sunrise, respectively, than activity-onset and -offset. Obviously, they were better circadian markers for the phase position of the entrained activity rhythm than activity-onset and -offset, which were subject to more masking effects of environmental and/or internal factors. Total daily activity was lowest during the two coldest lunar months, and almost twice as high during the warmest months. Nighttime (21:00-06:00 h) and daytime (09:00-18:00 h) activity varied significantly across the year, but in an opposite manner. Highest nighttime activity occurred in summer and maximal daytime activity during the cold winter months. Dusk and dawn activity, which together accounted for 43% of the total daily activity, barely changed. The monkeys tended to terminate their nightly activity period earlier on warm and rainy days, whereas the daily amount of activity showed no significant correlation either with temperature or precipitation. These data are consistent with the dual-oscillator hypothesis of circadian regulation. They suggest the seasonal variations of the timing and pattern of daily activity in wild owl monkeys of the Argentinean Chaco result from a specific interplay of light entrainment of circadian rhythmicity and strong masking effects of various endogenous and environmental factors. Since the phase position of the monkeys' evening and morning activity peaks did not vary considerably over the year, the seasonal change from a crepuscular/nocturnal activity pattern in summer to a more crepuscular/cathemeral one in winter does not depend on a corresponding phase shift of the entrained circadian rhythm, but mainly on masking effects. Thermoregulatory and energetic demands and constraints seem to play a crucial role.

Genetic Characterization of Trypanosoma cruzi DTUs in Wild Triatoma infestans from Bolivia: Predominance of TcI

PubMed Central

Brenière, Simone Frédérique; Aliaga, Claudia; Waleckx, Etienne; Buitrago, Rosio; Salas, Renata; Barnabé, Christian; Tibayrenc, Michel; Noireau, François

2012-01-01

Background The current persistence of Triatoma infestans (one of the main vectors of Chagas disease) in some domestic areas could be related to re-colonization by wild populations which are increasingly reported. However, the infection rate and the genetic characterization of the Trypanosoma cruzi strains infecting these populations are very limited. Methodology/Principal Findings Of 333 wild Triatoma infestans specimens collected from north to south of a Chagas disease endemic area in Bolivia, we characterized 234 stocks of Trypanosoma cruzi using mini-exon multiplex PCR (MMPCR) and sequencing the glucose phosphate isomerase (Gpi) gene. Of the six genetic lineages (“discrete typing units”; DTU) (TcI-VI) presently recognized in T. cruzi, TcI (99.1%) was overdominant on TcIII (0.9%) in wild Andean T. infestans, which presented a 71.7% infection rate as evaluated by microscopy. In the lowlands (Bolivian Chaco), 17 “dark morph” T. infestans were analyzed. None of them were positive for parasites after microscopic examination, although one TcI stock and one TcII stock were identified using MMPCR and sequencing. Conclusions/Significance By exploring large-scale DTUs that infect the wild populations of T. infestans, this study opens the discussion on the origin of TcI and TcV DTUs that are predominant in domestic Bolivian cycles. PMID:22685616

Wild populations of Triatoma infestans: Compilation of positive sites and comparison of their ecological niche with domestic population niche.

PubMed

Brenière, Simone Frédérique; Buitrago, Rosio; Waleckx, Etienne; Depickère, Stéphanie; Sosa, Victor; Barnabé, Christian; Gorla, David

2017-12-01

For several years, the wild populations of Triatoma infestans, main vector of Trypanosoma cruzi causing Chagas disease, have been considered or suspected of being a source of reinfestation of villages. The number of sites reported for the presence of wild T. infestans, often close to human habitats, has greatly increased, but these data are scattered in several publications, and others obtained by our team in Bolivia have not been published yet. Herein is compiled the largest number of wild sites explored for the presence of T. infestans collected with two methods The standardized methods aimed to determine the relationship between wild T. infestans and the ecoregion, and the directed method help to confirm the presence/absence of triatomines in the ecoregions. Entomological indices were compared between ecoregions and an environmental niche modelling approach, based on bioclimatic variables, was applied. The active search for wild T. infestans in Bolivia suggests a discontinuous distribution from the Andean valleys to the lowlands (Chaco), while the models used suggest a continuous distribution between the two regions and very large areas where wild populations remain to be discovered. The results compile the description of different habitats where these populations were found, and we demonstrate that the environmental niches of wild and domestic populations, defined by climatic variables, are similar but not equivalent, showing that during domestication, T. infestans has conquered new spaces with wider ranges of temperature and precipitation. The great diversity of wild T. infestans habitats and the comparison of their ecological niches with that of domestic populations confirm the behavioural plasticity of the species that increase the possibility of contact with humans. The result of the geographical distribution model of the wild populations calls for more entomological vigilance in the corresponding areas in the Southern Cone countries and in Bolivia. The current presentation is the most comprehensive inventory of wild T. infestans-positive sites that can be used as a reference for further entomological vigilance in inhabited areas. Copyright © 2017 Elsevier B.V. All rights reserved.

Holocene multidecadal and multicentennial droughts affecting Northern California and Nevada

USGS Publications Warehouse

Benson, L.; Kashgarian, Michaele; Rye, R.; Lund, S.; Paillet, F.; Smoot, J.; Kester, C.; Mensing, S.; Meko, D.; Lindstrom, S.

2002-01-01

Continuous, high-resolution ??18O records from cored sediments of Pyramid Lake, Nevada, indicate that oscillations in the hydrologic balance occurred, on average, about every 150 years (yr) during the past 7630 calendar years (cal yr). The records are not stationary; during the past 2740 yr, drought durations ranged from 20 to 100 yr and intervals between droughts ranged from 80 to 230 yr. Comparison of tree-ring-based reconstructions of climate change for the past 1200 yr from the Sierra Nevada and the El alpais region of northwest New Mexico indicates that severe droughts associated with Anasazi withdrawal from Chaco Canyon at 820 cal yr BP (calendar years before present) and final abandonment of Chaco Canyon, Mesa Verde, and the Kayenta area at 650 cal yr BP may have impacted much of the western United States.During the middle Holocene (informally defined in this paper as extending from 8000 to 3000 cal yr BP), magnetic susceptibility values of sediments deposited in Pyramid Lake's deep basin were much larger than late-Holocene (3000-0 cal yr BP) values, indicating the presence of a shallow lake. In addition, the mean ?? 18O value of CaCO3 precipitated between 6500 and 3430 cal yr BP was 1.6??? less than the mean value of CaCO3 precipitated after 2740 cal yr BP. Numerical calculations indicate that the shift in the ??18O baseline probably resulted from a transition to a wetter (> 30%) and cooler (3-5??C) climate. The existence of a relatively dry and warm middle-Holocene climate in the Truckee River - Pyramid Lake system is generally consistent with archeological, sedimentological, chemical, physical, and biological records from various sites within the Great Basin of the western United States. Two high-resolution Holocene-climate records are now available from the Pyramid and Owens lake basins which suggest that the Holocene was characterized by five climatic intervals. TIC and ??18O records from Owens Lake indicate that the first interval in the early Holocene (11,600-10,000 cal yr BP) was characterized by a drying trend that was interrupted by a brief (200 yr) wet oscillation centered at 10,300 cal yr BP. This was followed by a second early-Holocene interval (10,000-8000 cal yr BP) during which relatively wet conditions prevailed. During the early part of the middle Holocene (8000-6500 cal yr BP), high-amplitude oscillations in TIC in Owens Lake and ??18O in Pyramid Lake indicate the presence of shallow lakes in both basins. During the latter part of the middle Holocene (6500-3800 cal yr BP), drought conditions dominated, Owens Lake desiccated, and Lake Tahoe ceased spilling to the Truckee River, causing Pyramid Lake to decline. At the beginning of the late Holocene (???3000 cal yr BP), Lake Tahoe rose to its sill level and Pyramid Lake increased in volume. ?? 2002 Elsevier Science Ltd. All rights reserved.

Sources and controls for the mobility of arsenic in oxidizing groundwaters from loess-type sediments in arid/semi-arid dry climates - evidence from the Chaco-Pampean plain (Argentina).

PubMed

Nicolli, Hugo B; Bundschuh, Jochen; García, Jorge W; Falcón, Carlos M; Jean, Jiin-Shuh

2010-11-01

In oxidizing aquifers, arsenic (As) mobilization from sediments into groundwater is controlled by pH-dependent As desorption from and dissolution of mineral phases. If climate is dry, then the process of evaporative concentration contributes further to the total concentration of dissolved As. In this paper the principal As mobility controls under these conditions have been demonstrated for Salí River alluvial basin in NW Argentina (Tucumán Province; 7000 km(2)), which is representative for other basins or areas of the predominantly semi-arid Chaco-Pampean plain (1,000,000 km(2)) which is one of the world's largest regions affected by high As concentrations in groundwater. Detailed hydrogeochemical studies have been performed in the Salí River basin where 85 groundwater samples from shallow aquifers (42 samples), deep samples (26 samples) and artesian aquifers (17 samples) have been collected. Arsenic concentrations range from 11.4 to 1660 μg L(-1) leaving 100% of the investigated waters above the provisional WHO guideline value of 10 μg L(-1). A strong positive correlation among As, F, and V in shallow groundwaters was found. The correlations among those trace elements and U, B and Mo have less significance. High pH (up to 9.2) and high bicarbonate (HCO(3)) concentrations favour leaching from pyroclastic materials, including volcanic glass which is present to 20-25% in the loess-type aquifer sediments and yield higher trace element concentrations in groundwater from shallow aquifers compared to deep and artesian aquifers. The significant increase in minor and trace element concentrations and salinity in shallow aquifers is related to strong evaporation under semi-arid climatic conditions. Sorption of As and associated minor and trace elements (F, U, B, Mo and V) onto the surface of Fe-, Al- and Mn-oxides and oxi-hydroxides, restricts the mobilization of these elements into groundwater. Nevertheless, this does not hold in the case of the shallow unconfined groundwaters with high pH and high concentrations of potential competitors for adsorption sites (HCO(3), V, P, etc.). Under these geochemical conditions, desorption of the above mentioned anions and oxyanions occurs as a key process for As mobilization, resulting in an increase of minor and trace element concentrations. These geochemical processes that control the concentrations of dissolved As and other trace elements and which determine the groundwater quality especially in the shallow aquifers, are comparable to other areas with high As concentrations in groundwater of oxidizing aquifers and semi-arid or arid climate, which are found in many parts of the world, such as the western sectors of the USA, Mexico, northern Chile, Turkey, Mongolia, central and northern China, and central and northwestern Argentina. Copyright © 2010 Elsevier Ltd. All rights reserved.

Holocene multidecadal and multicentennial droughts affecting Northern California and Nevada

NASA Astrophysics Data System (ADS)

Benson, Larry; Kashgarian, Michaele; Rye, Robert; Lund, Steve; Paillet, Fred; Smoot, Joseph; Kester, Cynthia; Mensing, Scott; Meko, Dave; Lindström, Susan

2002-02-01

Continuous, high-resolution δ18O records from cored sediments of Pyramid Lake, Nevada, indicate that oscillations in the hydrologic balance occurred, on average, about every 150 years (yr) during the past 7630 calendar years (cal yr). The records are not stationary; during the past 2740 yr, drought durations ranged from 20 to 100 yr and intervals between droughts ranged from 80 to 230 yr. Comparison of tree-ring-based reconstructions of climate change for the past 1200 yr from the Sierra Nevada and the El Malpais region of northwest New Mexico indicates that severe droughts associated with Anasazi withdrawal from Chaco Canyon at 820 cal yr BP (calendar years before present) and final abandonment of Chaco Canyon, Mesa Verde, and the Kayenta area at 650 cal yr BP may have impacted much of the western United States.During the middle Holocene (informally defined in this paper as extending from 8000 to 3000 cal yr BP), magnetic susceptibility values of sediments deposited in Pyramid Lake's deep basin were much larger than late-Holocene (3000-0 cal yr BP) values, indicating the presence of a shallow lake. In addition, the mean δ18O value of CaCO 3 precipitated between 6500 and 3430 cal yr BP was 1.6‰ less than the mean value of CaCO 3 precipitated after 2740 cal yr BP. Numerical calculations indicate that the shift in the δ18O baseline probably resulted from a transition to a wetter (>30%) and cooler (3-5°C) climate. The existence of a relatively dry and warm middle-Holocene climate in the Truckee River-Pyramid Lake system is generally consistent with archeological, sedimentological, chemical, physical, and biological records from various sites within the Great Basin of the western United States. Two high-resolution Holocene-climate records are now available from the Pyramid and Owens lake basins which suggest that the Holocene was characterized by five climatic intervals. TIC and δ18O records from Owens Lake indicate that the first interval in the early Holocene (11,600-10,000 cal yr BP) was characterized by a drying trend that was interrupted by a brief (200 yr) wet oscillation centered at 10,300 cal yr BP. This was followed by a second early-Holocene interval (10,000-8000 cal yr BP) during which relatively wet conditions prevailed. During the early part of the middle Holocene (8000-6500 cal yr BP), high-amplitude oscillations in TIC in Owens Lake and δ18O in Pyramid Lake indicate the presence of shallow lakes in both basins. During the latter part of the middle Holocene (6500-3800 cal yr BP), drought conditions dominated, Owens Lake desiccated, and Lake Tahoe ceased spilling to the Truckee River, causing Pyramid Lake to decline. At the beginning of the late Holocene (˜3000 cal yr BP), Lake Tahoe rose to its sill level and Pyramid Lake increased in volume.

Spatio-temporal variability of NDVI-precipitation over southernmost South America: possible linkages between climate signals and epidemics

NASA Astrophysics Data System (ADS)

Tourre, Y. M.; Jarlan, L.; Lacaux, J.-P.; Rotela, C. H.; Lafaye, M.

2008-10-01

Climate-environment variability affects the rates of incidence of vector-borne and zoonotic diseases and is possibly associated with epidemics outbreaks. Over southernmost South America the joint spatio-temporal evolution of climate-environment is analyzed for the 1982-2004 period. Detailed mapping of normalized difference vegetation index (NDVI) and rainfall variability are then compared to zones with preliminary epidemiological reports. A significant quasi-biennial signal (2.2- to 2.4-year periods, or QB) for joint NDVI-rainfall variability is revealed. From rotated EOFs, dominant NDVI patterns are partitioned according to their lead frequencies: (1) the 'QB group' (2.1-to 3-year periods) includes six modes over southern Brazil, Uruguay, northern-central Argentina (two modes), the southern Paraguay-northern Argentina border, and the Santa Cruz Province; (2) the QB1 (2.4- to 3-year periods) + quasi-quadrennial (QQ) mode over the Misiones Province; and (3) the QB2 (2.1- to 2.5-year periods) + QQ + inter-annual (IA) (3- to 7-year periods) two modes over south-eastern Argentina. Modes within the 'QB group' are positively correlated with global climate signals and SST. The Uruguayan mode is correlated with global ENSO (8-month lag) whilst the southern Entre-Rios/northern Buenos Aires provinces are correlated with central equatorial Pacific SSTs (3-month lag). The Santa Cruz (Patagonia) Province is most correlated with the Pacific South America (PSA) index and SST patterns (3-month lag) along the Antarctica circumpolar current. The spatial distribution of lead NDVI modes includes the Formosa, Misiones, Chaco and Buenos Aires provinces among others, known for being prone to vector-borne epidemics such as dengue fever, malaria, leishmaniasis (American cutaneous leishmaniasis or ACL), hantivirus, chagas and Argentine hemorrhagic fever (AHF). Some provinces also correspond to regions where lead NDVI PCs' modes are associated with high-frequency climate signals such as the quasi-biennial oscillation in northwest Argentina. The joint preliminary results (climate-environment-public health reports) presented here for the first time are meant: (1) to contribute to a better understanding of climate-environment-epidemics process-based and modeling studies and (2) to facilitate, in the long run, the implementation of local and regional health early warning systems (HEWS) over southernmost South America. The latter is becoming crucial with ever-increasing migration, urban sprawl (re-emergence of dengue fever epidemics since the late 1990s), all embedded in a climate change context.

South America as seen from the Apollo 7 spacecraft

NASA Image and Video Library

1968-10-17

AS07-07-1826 (17 Oct. 1968) --- This view of South America was photographed from the Apollo 7 spacecraft during its 81st revolution of Earth from an altitude of 120 nautical miles. The port city of Antofagasta, Chile, is located in the half-moon shaped bay in the lower left portion of the picture. Beyond the coast is the Andean peak of Llullaillaco Volcano which rises 22,000 feet above sea level. At left center is the Chuquicamata copper mines located near Coloma. At the center of the photo, behind the large salt lake and atop a 19,000 foot high volcano, the countries of Bolivia, Argentina, and Chile meet at a common point. Below the clouds in the upper portion of the photo are the Great Plains known as the Gran Chaco.

Arthropods on plants in a fragmented Neotropical dry forest: a functional analysis of area loss and edge effects.

PubMed

González, Ezequiel; Salvo, Adriana; Valladares, Graciela

2015-02-01

Loss and fragmentation of natural ecosystems are widely recognized as the most important threats to biodiversity conservation, with Neotropical dry forests among the most endangered ecosystems. Area and edge effects are major factors in fragmented landscapes. Here, we examine area and edge effects and their interaction, on ensembles of arthropods associated to native vegetation in a fragmented Chaco Serrano forest. We analyzed family richness and community composition of herbivores, predators, and parasitoids on three native plant species in 12 fragments of varying size and at edge/interior positions. We also looked for indicator families by using Indicator Species Analysis. Loss of family richness with the reduction of forest fragment area was observed for the three functional groups, with similar magnitude. Herbivores were richer at the edges without interaction between edge and area effects, whereas predators were not affected by edge/interior position and parasitoid richness showed an interaction between area and position, with a steeper area slope at the edges. Family composition of herbivore, predator, and parasitoid assemblages was also affected by forest area and/or edge/interior situation. We found three indicator families for large remnants and five for edges. Our results support the key role of forest area for conservation of arthropods taxonomic and functional diversity in a highly threatened region, and emphasize the need to understand the interactions between area and edge effects on such diversity. © 2014 Institute of Zoology, Chinese Academy of Sciences.

Indolizidine 239Q and Quinolizidine 275I. Major alkaloids in two Argentinian bufonid toads (Melanophryniscus)

PubMed Central

Daly, John W.; Garraffo, H. Martin; Spande, Thomas F.; Yeh, Herman J. C.; Peltzer, Paola M.; Cacivio, Pedro; Baldo, J. Diego; Faivovich, Julián

2008-01-01

Alkaloid profiles in skin of poison frogs/toads (Dendrobatidae, Mantellidae, Bufonidae, and Myobatrachidae) are highly dependent on diet and hence on the nature of habitat. Extracts of the two species of toads (Melanophryniscus klappenbachi and M. cupreuscapularis) from similar habitats in the Corrientes/Chaco Provinces of Argentina have similar profiles of alkaloids, which differ considerably from profiles from other Melanophryniscus species from Brazil, Uruguay and Argentina. Structures of two major alkaloids 239Q (1) and 275I (2) were determined by mass, FTIR, and NMR spectral analysis as 5Z,9Z-3-(1-hydroxybutyl)-5-propylindolizidine and 6Z,10E-4,6-di(pent-4-enyl) quinolizidine, respectively. A third alkaloid, 249F (3), is postulated to be a homopumiliotoxin with an unprecedented conjugated exocyclic diene moiety. PMID:18848574

Low-Level Jets and Their Effects on the South American Summer Climate as Simulated by the NCEP Eta Model(.

NASA Astrophysics Data System (ADS)

Vernekar, Anandu D.; Kirtman, Ben P.; Fennessy, Michael J.

2003-01-01

The National Centers for Environmental Prediction (NCEP) Eta Model (80 km, 38L) is used to simulate the tropical South American summer (January-March) climate for 1983, 1985, 1987, 1989, and 1991 using lateral boundary conditions from the NCEP-National Center for Atmospheric Research (NCAR) reanalysis. Simulations of the lower tropospheric circulation and precipitation are analyzed to study the variability on diurnal, intraseasonal, and interannual timescales. The results are compared with observations and previous studies.The Eta Model produces better regional circulation details, such as low-level jets (LLJs), than does the reanalysis because of its higher resolution, more realistic topography and coastal geometry, and because of its ability to realistically simulate the effects of mesoscale circulation on the time-mean flow. The model detects not only the LLJ east of the Andes Mountains and the LLJ west of northern Cordillera Occidental, which have been reported in previous studies, but it also detects three distinct LLJs just north of the equator embedded in the strong northeasterly trade winds over Colombia, Venezuela, and Guiana. All the LLJs show strong diurnal variability with a nocturnal maximum. The LLJ east of the Andes Mountains brings warm moist air from the Amazon basin to the Gran Chaco region where the jet exits. The moisture convergence in the jet exit region creates favorable conditions for precipitation. Hence, the precipitation over the region also shows strong diurnal variability with a nocturnal maximum. The LLJs just north of the equator bring moisture from the tropical Atlantic Ocean, the western Caribbean Sea, and the Gulf of Panama to their exit regions over the northern Amazon basin and west coasts of Colombia and Ecuador. The precipitation over these regions also has diurnal variability with a nocturnal maximum. The diurnal variability of precipitation over most of the Tropics has an afternoon rainfall maximum except for regions influenced by LLJs, which have a nocturnal rainfall maximum. The intraseasonal variability of the LLJs is episodic with an approximate period of 20 days. The interannual variability of the LLJs is dominated by the ENSO cycle. The LLJ east of the Andes Mountains is stronger in the warm phase of ENSO than in the cold phase. However, the model has some difficulty simulating the observed relationship between the strength of LLJ and precipitation, but the model succeeds in the case of LLJs just north of the equator. For example, these LLJs are weaker in the warm phase of ENSO than in the cold phase. Hence, during the warm (cold) phase of ENSO, dry (wet) conditions normally occur over the northern part of the Amazon basin, which is the exit region of these LLJs.

Key Source Habitats and Potential Dispersal of Triatoma infestans Populations in Northwestern Argentina: Implications for Vector Control

PubMed Central

Gürtler, Ricardo E.; Cecere, María C.; Fernández, María del Pilar; Vazquez-Prokopec, Gonzalo M.; Ceballos, Leonardo A.; Gurevitz, Juan M.; Kitron, Uriel; Cohen, Joel E.

2014-01-01

Background Triatoma infestans —the principal vector of the infection that causes Chagas disease— defies elimination efforts in the Gran Chaco region. This study identifies the types of human-made or -used structures that are key sources of these bugs in the initial stages of house reinfestation after an insecticide spraying campaign. Methodology and Principal Findings We measured demographic and blood-feeding parameters at two geographic scales in 11 rural communities in Figueroa, northwest Argentina. Of 1,297 sites searched in spring, 279 (21.5%) were infested. Bug abundance per site and female fecundity differed significantly among habitat types (ecotopes) and were highly aggregated. Domiciles (human sleeping quarters) had maximum infestation prevalence (38.7%), human-feeding bugs and total egg production, with submaximal values for other demographic and blood-feeding attributes. Taken collectively peridomestic sites were three times more often infested than domiciles. Chicken coops had greater bug abundance, blood-feeding rates, engorgement status, and female fecundity than pig and goat corrals. The host-feeding patterns were spatially structured yet there was strong evidence of active dispersal of late-stage bugs between ecotopes. Two flight indices predicted that female fliers were more likely to originate from kitchens and domiciles, rejecting our initial hypothesis that goat and pig corrals would dominate. Conclusions and Significance Chicken coops and domiciles were key source habitats fueling rapid house reinfestation. Focusing control efforts on ecotopes with human-fed bugs (domiciles, storerooms, goat corrals) would neither eliminate the substantial contributions to bug population growth from kitchens, chicken coops, and pig corrals nor stop dispersal of adult female bugs from kitchens. Rather, comprehensive control of the linked network of ecotopes is required to prevent feeding on humans, bug population growth, and bug dispersal simultaneously. Our study illustrates a demographic approach that may be applied to other regions and triatomine species for the design of innovative, improved vector control strategies. PMID:25299653

Effects of mining activities on heavy metal concentrations in water, sediment, and macroinvertebrates in different reaches of the Pilcomayo River, South America.

PubMed

Smolders, A J P; Lock, R A C; Van der Velde, G; Medina Hoyos, R I; Roelofs, J G M

2003-04-01

From 1997 until 1999 the extent and the ecological effects of zinc, copper, lead, and cadmium pollution were studied in different reaches of the South American Pilcomayo River. A comparison of metal concentrations in water, sediment, and chironomid larvae, as well as the diversity of macroinvertebrate species, was made between sites near the origin of the Pilcomayo River, with hardly any mining activities, sites in the Potosí region, with intensive mining, and sites located 500 km or further downstream of Potosí, in the Chaco plain. Samples were also collected in an unpolluted river (Cachi Mayu River) and in the Tarapaya River, which is strongly contaminated by mine tailings (1000 tons a day). The upper parts of the Pilcomayo River are strongly affected by the release of mine tailings from the Potosí mines where mean concentrations of lead, cadmium, copper, and zinc in water, filtered water, sediment, and chironomid larvae were up to a thousand times higher than the local background levels. The diversity of the benthic macroinvertebrate community was strongly reduced in the contaminated parts; 97% of the benthic macroinvertebrates consisted of chironomid larvae. The degree of contamination in the lower reaches of the river, however, was fairly low because of sedimentation processes and the strong dilution of mine tailings with enormous amounts of clean sediment from erosion processes. Analysis of sediment cores from the Ibibobo floodplain, however, reveal an increase of the heavy metal concentrations in the lower reaches since the introduction of the contaminating flotation process in the mine industry in 1985.

A screening questionnaire for convulsive seizures: A three-stage field-validation in rural Bolivia.

PubMed

Giuliano, Loretta; Cicero, Calogero Edoardo; Crespo Gómez, Elizabeth Blanca; Padilla, Sandra; Bruno, Elisa; Camargo, Mario; Marin, Benoit; Sofia, Vito; Preux, Pierre-Marie; Strohmeyer, Marianne; Bartoloni, Alessandro; Nicoletti, Alessandra

2017-01-01

Epilepsy is one of the most common neurological diseases in Latin American Countries (LAC) and epilepsy associated with convulsive seizures is the most frequent type. Therefore, the detection of convulsive seizures is a priority, but a validated Spanish-language screening tool to detect convulsive seizures is not available. We performed a field validation to evaluate the accuracy of a Spanish-language questionnaire to detect convulsive seizures in rural Bolivia using a three-stage design. The questionnaire was also administered face-to-face, using a two-stage design, to evaluate the difference in accuracy. The study was carried out in the rural communities of the Gran Chaco region. The questionnaire consists of a single screening question directed toward the householders and a confirmatory section administered face-to-face to the index case. Positive subjects underwent a neurological examination to detect false positive and true positive subjects. To estimate the proportion of false negative, a random sample of about 20% of the screened negative underwent a neurological evaluation. 792 householders have been interviewed representing a population of 3,562 subjects (52.2% men; mean age 24.5 ± 19.7 years). We found a sensitivity of 76.3% (95% CI 59.8-88.6) with a specificity of 99.6% (95% CI 99.4-99.8). The two-stage design showed only a slightly higher sensitivity respect to the three-stage design. Our screening tool shows a good accuracy and can be easily used by trained health workers to quickly screen the population of the rural communities of LAC through the householders using a three-stage design.

Unexpected Failures to Control Chagas Disease Vectors With Pyrethroid Spraying in Northern Argentina

PubMed Central

Gurevitz, J. M.; Gaspe, M. S.; Enríquez, G. F.; Vassena, C. V.; Alvarado-Otegui, J. A.; Provecho, Y. M.; Mougabure Cueto, G. A; Picollo, M. I.; Kitron, U.; Gürtler, R. E.

2013-01-01

Effectiveness of the elimination efforts against Triatoma infestans (Klug) in South America through residual application of pyrethroid insecticides has been highly variable in the Gran Chaco region. We investigated apparent vector control failures after a standard community-wide spraying with deltamethrin SC in a rural area of northeastern Argentina encompassing 353 houses. Insecticide spraying reduced house infestation less than expected: from 49.5% at baseline to 12.3 and 6.7% at 4 and 8 mo postspraying, respectively. Persistent infestations were detected in 28.4% of houses, and numerous colonies with late-stage bugs were recorded after the interventions. Laboratory bioassays showed reduced susceptibility to pyrethroids in the local bug populations. Eleven of 14 bug populations showed reduced mortality in diagnostic dose assays (range, 35 ± 5% to 97 ± 8%) whereas the remainder had 100% mortality. A fully enclosed residual bug population in a large chicken coop survived four pyrethroid sprays, including two double-dose applications, and was finally suppressed with malathion. The estimated resistance ratio of this bug population was 7.17 (range, 4.47–11.50). Our field data combined with laboratory bioassays and a residual foci experiment demonstrate that the initial failure to suppress T. infestans was mainly because of the unexpected occurrence of reduced susceptibility to deltamethrin in an area last treated with pyrethroid insecticides 12 yr earlier. Our results underline the need for close monitoring of the impact of insecticide spraying to provide early warning of possible problems due to enhanced resistance or tolerance and determine appropriate responses. PMID:23270166

Global Albedo

NASA Technical Reports Server (NTRS)

2002-01-01

Once home to the powerful Inca Empire, the spectacular vistas and canyons of the South American Andes are now a favorite to mountain bikers, climbers and other tourists looking for an adventure. This true color image of the Central Andes and surrounding landscape was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra spacecraft. The dark green area to the right of the brown mountains are the Gran Chaco planes, which consist mostly of alluvial fans and wetlands. To the west is the Pacific Ocean. In the upper half of this image, the Andes are formed by two distinct mountain ranges that appear as darker reddish-brown bands running northwest to southeast. Between the two ranges, shown in a lighter brown, sits the Altiplano plateau, which spans southern Peru and northern Bolivia. The plateau sits at 3660 meters (12,000 feet) and is covered in mazelike canyons, marshlands and lakes. The largest of the lakes-Lake Titticaca-can be seen as the dark blue patch in southern Peru. The two mountain ranges supporting the plateau eventually come together along the border of Argentina and Chile to form one continuous range. The Andes have been forming over the past 170 million years as the Nazca Plate lying under the Pacific Ocean has forced its way under the South American Plate and pushed up its western edge. The subduction of one plate under the other has given rise to a number of volcanoes that dot the western edge of the mountain range. Earthquakes are also very common in this region. Image by NASA GSFC, based on data from the MODIS science team.

[The transmission de Chagas disease in Salta and the detection of congenital cases].

PubMed

Basombrío, M A; Nasser, J; Segura, M A; Marco, D; Sánchez Negrette, O; Padilla, M; Mora, M C

1999-01-01

Data on the prevalence of Trypanosoma cruzi infection is presented for the province of Salta, Argentina. Special emphasis is given to the detection of congenital transmission and to the economic benefits of preventing Chagas' disease. Seroepidemiological data obtained from 20 year old army draftees revealed a reduction, from 22.7 to 11.11% between 1964 and 1985. In university students, a rate of 0.96% was found in 1998. Surveys carried out during 1996 showed that more than 15% of the pregnant women analyzed carried T. cruzi infection, particularly in the north of the province. This situation brings about a high risk of appearance of congenital cases and represents an opportunity to test the most adequate strategies for detection. By applying systematically microhematocrit, hemoculture and PCR methods, to umbilical chord blood, an increase in the early detection of congenitally infected babies is being achieved. In 1992-94, very high seroprevalence rates of infection were found among indians of the Chaco region of Salta. The overall rate was 37%, but there were 5 localities where more than 54% of the population was infected. These numbers indicate that, in vast areas of the provincial territory, fight against vector bugs must not merely consist of surveilance activities, but rather of renewed spraying attacks. The fight must include control of pregnant women and blood banks. An economic analysis of the economic return, calculated only for spraying activities and for the Department of Anta (Salta), indicated a net present value of over 7 million dollars and an internal rate of return exceeding 60%.

A search for natural bioactive compounds in Bolivia through a multidisciplinary approach. Part VI. Evaluation of the antimalarial activity of plants used by Isoceño-Guaraní Indians.

PubMed

Bourdy, G; Oporto, P; Gimenez, A; Deharo, E

2004-08-01

Seventy-seven plant extracts (corresponding to 62 different species) traditionally used by the Isoceño-Guaraní, a native community living in the Bolivian Chaco, were screened for antimalarial activity in vitro on Plasmodium falciparum chloroquine sensitive strain (F32), and on ferriprotoporphyrin (FP) IX biocrystallisation inhibition test (FBIT). Among these extracts, seven displayed strong in vitro antimalarial activity, and 25 were active in the FBIT test. Positive results on both tests were recorded for six extracts: Argemone subfusiformis aerial part, Aspidosperma quebracho-blanco bark, Castela coccinea leaves and bark, Solanum argentinum leaves and Vallesia glabra bark. Results are discussed in relation with Isoceño-Guaraní traditional medicine. Further studies to be undertaken in relation with these results are also highlighted.

Initial sequence characterization of the rhabdoviruses of squamate reptiles, including a novel rhabdovirus from a caiman lizard (Dracaena guianensis)

PubMed Central

Wellehan, James F.X.; Pessier, Allan P.; Archer, Linda L.; Childress, April L.; Jacobson, Elliott R.; Tesh, Robert B.

2012-01-01

Rhabdoviruses infect a variety of hosts, including non-avian reptiles. Consensus PCR techniques were used to obtain partial RNA-dependent RNA polymerase gene sequence from five rhabdoviruses of South American lizards; Marco, Chaco, Timbo, Sena Madureira, and a rhabdovirus from a caiman lizard (Dracaena guianensis). The caiman lizard rhabdovirus formed inclusions in erythrocytes, which may be a route for infecting hematophagous insects. This is the first information on behavior of a rhabdovirus in squamates. We also obtained sequence from two rhabdoviruses of Australian lizards, confirming previous Charleville virus sequence and finding that, unlike a previous sequence report but in agreement with serologic reports, Almpiwar virus is clearly distinct from Charleville virus. Bayesian and maximum likelihood phylogenetic analysis revealed that most known rhabdoviruses of squamates cluster in the Almpiwar subgroup. The exception is Marco virus, which is found in the Hart Park group. PMID:22397930

Evaluation of an autochthonous starter culture on the production of a traditional dry fermented sausage from Chaco (Argentina) at a small-scale facility.

PubMed

Palavecino Prpich, Noelia Z; Garro, Oscar A; Romero, Mara; Judis, María A; Cayré, María E; Castro, Marcela P

2016-05-01

The performance of a mixed starter culture, SAS-1, comprised of the autochthonous strains Lactobacillus sakei ACU-2 and Staphylococcus vitulinus ACU-10, was evaluated into the production process of a traditional dry sausage. Microbiological, physicochemical and sensory analyses were carried out to accomplish this goal. Results showed an improvement in performance through the introduction of SAS-1; adding mixed starter culture rapidly decreased pH, inhibited the growth of contaminant microorganisms and enhanced the beneficial ones, diminished TBARS, and highlighted color and aroma attributes. However, most influential organoleptic descriptors among consumer acceptance were not affected by the addition of the starter. This starter culture would represent a valuable tool to improve the homogeneity of artisanal manufacture of this traditional food. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ethnoastronomy in the Multicultural Context of the Agricultural Colonies in Northern Santa Fe Province, Argentina

NASA Astrophysics Data System (ADS)

Mudrik, Armando

In this paper, we present a study about cultural astronomy among European colonists and their Argentinean descendants, in the context of a complex interaction between criollos, aboriginals and European colonists from different origins and religions, who settled in the northern area of the Argentinean province of Santa Fe, which is part of the southern Gran Chaco. These colonists arrived among waves of immigration occurring in Argentina in the second half of the nineteenth century and the first half of the twentieth century. Through ethnographic field research among these immigrants and their descendants, we carried out a survey of their astronomical representations and practices, and the connections of these with their social life and farming tasks. Through this we gained an insight as to how the astronomical ideas of immigrants, criollos and aboriginal groups influenced each other, generating a variety of new relations with the celestial realm.

[A review of thirty years of activity of the Research Program in Psychiatric Epidemiology (PEPSI) of the CONICET].

PubMed

Pavlovsky, Federico

2003-01-01

This article summarizes the activity of the Programa de Investigaciones en Epidemiología Psiquiátrica (PEPSI) (Research Program in Psychiatric Epidemiology) of the CONICET, directed for more than thirty years by Fernando Pages Larraya. After an anthropologic psychiatric experience done in the Gran Chaco Gualamba, by the end of the 60s, Pages Larraya and his team developed the theory of Cultural Isoidias, zones into which the country could be divided for epidemiologic studies. This article summarizes some of the principal lines of investigation of this program which departures from an initial study of the prevalence of mental diseases in Argentina. Other lines of research (such as a study about marginality, about Alzheimer's disease, about alcoholism and about AIDS) are summarized very briefly so as to give the reader an idea about the enormous field of study embraced by the PEPSI.

Comparative and functional triatomine genomics reveals reductions and expansions in insecticide resistance-related gene families.

PubMed

Traverso, Lucila; Lavore, Andrés; Sierra, Ivana; Palacio, Victorio; Martinez-Barnetche, Jesús; Latorre-Estivalis, José Manuel; Mougabure-Cueto, Gaston; Francini, Flavio; Lorenzo, Marcelo G; Rodríguez, Mario Henry; Ons, Sheila; Rivera-Pomar, Rolando V

2017-02-01

Triatomine insects are vectors of Trypanosoma cruzi, a protozoan parasite that is the causative agent of Chagas' disease. This is a neglected disease affecting approximately 8 million people in Latin America. The existence of diverse pyrethroid resistant populations of at least two species demonstrates the potential of triatomines to develop high levels of insecticide resistance. Therefore, the incorporation of strategies for resistance management is a main concern for vector control programs. Three enzymatic superfamilies are thought to mediate xenobiotic detoxification and resistance: Glutathione Transferases (GSTs), Cytochromes P450 (CYPs) and Carboxyl/Cholinesterases (CCEs). Improving our knowledge of key triatomine detoxification enzymes will strengthen our understanding of insecticide resistance processes in vectors of Chagas' disease. The discovery and description of detoxification gene superfamilies in normalized transcriptomes of three triatomine species: Triatoma dimidiata, Triatoma infestans and Triatoma pallidipennis is presented. Furthermore, a comparative analysis of these superfamilies among the triatomine transcriptomes and the genome of Rhodnius prolixus, also a triatomine vector of Chagas' disease, and other well-studied insect genomes was performed. The expression pattern of detoxification genes in R. prolixus transcriptomes from key organs was analyzed. The comparisons reveal gene expansions in Sigma class GSTs, CYP3 in CYP superfamily and clade E in CCE superfamily. Moreover, several CYP families identified in these triatomines have not yet been described in other insects. Conversely, several groups of insecticide resistance related enzymes within each enzyme superfamily are reduced or lacking in triatomines. Furthermore, our qRT-PCR results showed an increase in the expression of a CYP4 gene in a T. infestans population resistant to pyrethroids. These results could point to an involvement of metabolic detoxification mechanisms on the high levels of pyrethroid resistance detected in triatomines from the Gran Chaco ecoregion. Our results help to elucidate the potential insecticide resistance mechanisms in vectors of Chagas' disease and provide new relevant information for this field. This study shows that metabolic resistance might be a contributing cause of the high pyrethroid resistance observed in wild T. infestans populations from the Gran Chaco ecoregion, area in which although subjected to intense pyrethroid treatments, vector control has failed. This study opens new avenues for further functional studies on triatomine detoxification mechanisms.

Comparative and functional triatomine genomics reveals reductions and expansions in insecticide resistance-related gene families

PubMed Central

Traverso, Lucila; Lavore, Andrés; Sierra, Ivana; Palacio, Victorio; Martinez-Barnetche, Jesús; Latorre-Estivalis, José Manuel; Mougabure-Cueto, Gaston; Francini, Flavio; Lorenzo, Marcelo G.; Rodríguez, Mario Henry; Ons, Sheila; Rivera-Pomar, Rolando V.

2017-01-01

Background Triatomine insects are vectors of Trypanosoma cruzi, a protozoan parasite that is the causative agent of Chagas’ disease. This is a neglected disease affecting approximately 8 million people in Latin America. The existence of diverse pyrethroid resistant populations of at least two species demonstrates the potential of triatomines to develop high levels of insecticide resistance. Therefore, the incorporation of strategies for resistance management is a main concern for vector control programs. Three enzymatic superfamilies are thought to mediate xenobiotic detoxification and resistance: Glutathione Transferases (GSTs), Cytochromes P450 (CYPs) and Carboxyl/Cholinesterases (CCEs). Improving our knowledge of key triatomine detoxification enzymes will strengthen our understanding of insecticide resistance processes in vectors of Chagas’ disease. Methods and findings The discovery and description of detoxification gene superfamilies in normalized transcriptomes of three triatomine species: Triatoma dimidiata, Triatoma infestans and Triatoma pallidipennis is presented. Furthermore, a comparative analysis of these superfamilies among the triatomine transcriptomes and the genome of Rhodnius prolixus, also a triatomine vector of Chagas’ disease, and other well-studied insect genomes was performed. The expression pattern of detoxification genes in R. prolixus transcriptomes from key organs was analyzed. The comparisons reveal gene expansions in Sigma class GSTs, CYP3 in CYP superfamily and clade E in CCE superfamily. Moreover, several CYP families identified in these triatomines have not yet been described in other insects. Conversely, several groups of insecticide resistance related enzymes within each enzyme superfamily are reduced or lacking in triatomines. Furthermore, our qRT-PCR results showed an increase in the expression of a CYP4 gene in a T. infestans population resistant to pyrethroids. These results could point to an involvement of metabolic detoxification mechanisms on the high levels of pyrethroid resistance detected in triatomines from the Gran Chaco ecoregion. Conclusions and significance Our results help to elucidate the potential insecticide resistance mechanisms in vectors of Chagas’ disease and provide new relevant information for this field. This study shows that metabolic resistance might be a contributing cause of the high pyrethroid resistance observed in wild T. infestans populations from the Gran Chaco ecoregion, area in which although subjected to intense pyrethroid treatments, vector control has failed. This study opens new avenues for further functional studies on triatomine detoxification mechanisms. PMID:28199333

Paleogeography of the upper Paleozoic basins of southern South America: An overview

NASA Astrophysics Data System (ADS)

Limarino, Carlos O.; Spalletti, Luis A.

2006-12-01

The paleogeographic evolution of Late Paleozoic basins located in southern South America is addressed. Three major types of basins are recognized: infracratonic or intraplate, arc-related, and retroarc. Intraplate basins (i.e., Paraná, Chaco-Paraná, Sauce Grande-Colorado, and La Golondrina) are floored by continental or quasi-continental crust, with low or moderate subsidence rates and limited magmatic and tectonic activity. Arc-related basins (northern and central Chile, Navidad-Arizaro, Río Blanco, and Calingasta-Uspallata basins and depocenters along Chilean Patagonia) show a very complex tectonic history, widespread magmatic activity, high subsidence rates, and in some cases metamorphism of Late Paleozoic sediments. An intermediate situation corresponds to the retroarc basins (eastern Madre de Dios, Tarija, Paganzo, and Tepuel-Genoa), which lack extensive magmatism and metamorphism but in which coeval tectonism and sedimentation rates were likely more important than those in the intraplate region. According to the stratigraphic distribution of Late Paleozoic sediments, regional-scale discontinuities, and sedimentation pattern changes, five major paleogeographic stages are proposed. The lowermost is restricted to the proto-Pacific and retroarc basins, corresponds to the Mississippian (stage 1), and is characterized by shallow marine and transitional siliciclastic sediments. During stage 2 (Early Pennsylvanian), glacial-postglacial sequences dominated the infracratonic (or intraplate) and retroarc basins, and terrigenous shallow marine sediments prevailed in arc-related basins. Stage 3 (Late Pennsylvanian-Early Cisuralian) shows the maximum extension of glacial-postglacial sediments in the Paraná and Sauce Grande-Colorado basins (intraplate region), whereas fluvial deposits interfingering with thin intervals of shallow marine sediments prevailed in the retroarc basins. To the west, arc-related basins were dominated by coastal to deep marine conditions (including turbiditic successions). In the Late Cisuralian (stage 4), important differences in sedimentation patterns are registered for the western arc-related basins and eastern intraplate basins. The former were locally dominated by volcaniclastic sediments or marine deposits, and the intraplate basins are characterized by shallow marine conditions punctuated by several episodes of deltaic progradation. Finally, in the Late Permian (stage 5), volcanism and volcaniclastic sedimentation dominated in basins located along the western South American margin. The intraplate basins in turn were characterized by T-R cycles composed of shallow marine, deltaic, and fluvial siliciclastic deposits.

Mycorrhizal fungi isolated from native terrestrial orchids of pristine regions in Cordoba (Argentina).

PubMed

Fernández Di Pardo, Agustina; Chiocchio, Viviana M; Barrera, Viviana; Colombo, Roxana P; Martinez, Alicia E; Gasoni, Laura; Godeas, Alicia M

2015-03-01

Orchidaceae is a highly dependent group on the Rhizoctonia complex that includes Ceratorhiza, Moniliopsis, Epulorhiza and Rhizoctonia, for seed germination and the development of new orchid plants. Thus, the isolation and identification of orchid mycorrhizal fungi are important to understand the orchid-fungus relationship, which can lead to the development of efficient conservation strategies by in vivo germination of seeds from endangered orchid plants. The aim of our work was to isolate and characterize the different mycorrhizal fungi found in roots of terrestrial orchids from Cordoba (Argentina), and, to learn about the natural habit and fungal associations in the Chaco Serrano woodland pristine region. In this study, bloomed orchid root and rhizosphere soil samples were obtained in two times from Valle de Punilla during spring of 2007; samples were kept in plastic bags until processed within 48 hours, and mycorrhizal condition confirmed assessing peloton presence. A total of 23 isolates of the orchideous mycorrhizal Rhizoctonia complex were obtained. The isolates were studied based on morphological characters and ITS-rDNA sequences. Morphological characteristics as color of colonies, texture, growth rate, hyphal diameter and length and presence of sclerotia were observed on culture media. To define the number of nuclei per cell, the isolates were grown in Petri dishes containing water-agar (WA) for three days at 25 degrees C and stained with Safranine-O solution. The mycorrhizal fungi were grouped into binucleate (MSGib, 10 isolates) and multinucleate (MSGim, 13 isolates) based on morphological characteristics of the colonies. We obtained the ITS1-5.8s-ITS4 region that was amplified using primers ITSI and ITS4. Based on DNA sequencing, isolates Q23 and Q29 were found to be related to species of Ceratobasidium. Isolates Q24 and Q4 were related to the binucleated anastomosis group AG-C of Rhizoctonia sp. The rest of the isolates grouped in the Ceratobasidium clade without grouping. From our knowledge this is the first report of the asso- ciation of the AG-C testers with terrestrial orchids. A high specificity was observed in the symbiotic relationship. As the mycorrhizal fungal isolates were obtained from native orchids, they could be incorporated in conservation programes of endangered orchids in Argentina.

Biological behavior of different Trypanosoma cruzi isolates circulating in an endemic area for Chagas disease in the Gran Chaco region of Argentina.

PubMed

Ragone, Paula G; Pérez Brandán, Cecilia; Padilla, Angel M; Monje Rumi, Mercedes; Lauthier, Juan J; Alberti D'Amato, Anahí M; Tomasini, Nicolás; Cimino, Ruben O; Romero, Nélida M; Portelli, Marcela; Nasser, Julio R; Basombrío, Miguel A; Diosque, Patricio

2012-09-01

The biological behavior of the different Trypanosoma cruzi strains is still unclear and the importance of exploring the relevance of these differences in natural isolates is of great significance. Herein we describe the biological behavior of four T. cruzi isolates circulating sympatrically in a restricted geographic area in Argentina endemic for Chagas Disease. These isolates were characterized as belonging to the Discrete Typing Units (DTUs) TcI, TcIII, TcV and TcVI as shown by Multilocus Enzyme Electrophoresis and Multilocus Sequence Typing. In order to study the natural behavior of the different isolates and to preserve their natural properties, we developed a vector transmission model that allows their maintenance in the laboratory. The model consisted of serial passages of these parasites between insect vectors and mice. Vector-derived parasite forms were then inoculated in C57BL/6J mice and number of parasite in peripheral blood, serological response and histological damage in acute and chronic phases of the infection were measured. Parasites from DTUs TcI, TcIII and TcVI were detected by direct fresh blood examination, while TcV parasites could only be detected by Polimerase Chain Reaction. No significant difference in the anti-T. cruzi antibody response was found during the chronic phase of infection, except for mice infected with TcV parasites where no antibodies could be detected. Histological sections showed that TcI isolate produced more damage in skeletal muscle while TcVI induced more inflammation in the heart. This work shows differential biological behavior among different parasite isolates obtained from the same cycle of transmission, permitting the opportunity to formulate future hypotheses of clinical and epidemiological importance. Copyright © 2012 Elsevier B.V. All rights reserved.

Initial sequence characterization of the rhabdoviruses of squamate reptiles, including a novel rhabdovirus from a caiman lizard (Dracaena guianensis).

PubMed

Wellehan, James F X; Pessier, Allan P; Archer, Linda L; Childress, April L; Jacobson, Elliott R; Tesh, Robert B

2012-08-17

Rhabdoviruses infect a variety of hosts, including non-avian reptiles. Consensus PCR techniques were used to obtain partial RNA-dependent RNA polymerase gene sequence from five rhabdoviruses of South American lizards; Marco, Chaco, Timbo, Sena Madureira, and a rhabdovirus from a caiman lizard (Dracaena guianensis). The caiman lizard rhabdovirus formed inclusions in erythrocytes, which may be a route for infecting hematophagous insects. This is the first information on behavior of a rhabdovirus in squamates. We also obtained sequence from two rhabdoviruses of Australian lizards, confirming previous Charleville virus sequence and finding that, unlike a previous sequence report but in agreement with serologic reports, Almpiwar virus is clearly distinct from Charleville virus. Bayesian and maximum likelihood phylogenetic analysis revealed that most known rhabdoviruses of squamates cluster in the Almpiwar subgroup. The exception is Marco virus, which is found in the Hart Park group. Copyright © 2012 Elsevier B.V. All rights reserved.

Where did the chili get its spice? Biogeography of capsaicinoid production in ancestral wild chili species.

PubMed

Tewksbury, Joshua J; Manchego, Carlos; Haak, David C; Levey, Douglas J

2006-03-01

The biogeography of pungency in three species of wild chili in the chaco and surrounding highland habitats of southeastern Bolivia is described. We report that Capsicum chacoense, C. baccatum, and C. eximium are polymorphic for production of capsaicin and its analogs, such that completely pungent and completely nonpungent individuals co-occur in some populations. In C. chacoense, the density of plants and the proportion of pungent plants increased with elevation. Above 900 m, all individuals in all populations except two were pungent; nonpungent individuals in at least one of the two polymorphic populations were likely a result of spreading by humans. The occurrence of pungent and nonpungent individuals in three species of ancestral Capsicum and the geographic variation of pungency within species suggest that production of capsaicin and its analogs entails both costs and benefits, which shift from one locality to another. Determining the selection pressures behind such shifts is necessary to understand the evolution of pungency in chilies.

Remote sensing and geographic database management systems applications for the protection and conservation of cultural heritage

NASA Astrophysics Data System (ADS)

Palumbo, Gaetano; Powlesland, Dominic

1996-12-01

The Getty Conservation Institute is exploring the feasibility of using remote sensing associated with a geographic database management system (GDBMS) in order to provide archaeological and historic site managers with sound evaluations of the tools available for site and information management. The World Heritage Site of Chaco Canyon, New Mexico, a complex of archeological sites dating to the 10th to the 13th centuries AD, was selected as a test site. Information from excavations conducted there since the 1930s, and a range of documentation generated by the National Park Service was gathered. NASA's John C. Stennis Space Center contributed multispectral data of the area, and the Jet Propulsion Laboratory contributed data from ATLAS (airborne terrestrial applications sensor) and CAMS (calibrated airborne multispectral scanner) scanners. Initial findings show that while 'automatic monitoring systems' will probably never be a reality, with careful comparisons of historic and modern photographs, and performing digital analysis of remotely sensed data, excellent results are possible.

INCIDENCE OF TRYPANOSOMA CRUZI INFECTION AMONG CHILDREN FOLLOWING DOMESTIC REINFESTATION AFTER INSECTICIDE SPRAYING IN RURAL NORTHWESTERN ARGENTINA

PubMed Central

GÜRTLER, RICARDO E.; CECERE, MARÍA C.; LAURICELLA, MARTA A.; PETERSEN, ROSARIO M.; CHUIT, ROBERTO; SEGURA, ELSA L.; COHEN, JOEL E.

2005-01-01

Following increasing reinfestation with Triatoma infestans after insecticide spraying, the household incidence of infection with Trypanosoma cruzi in children was positively related to the domestic abundance of infected T. infestans and the presence or proportion of infected dogs or cats in Amamá, a rural village in northwestern Argentina. Seven (12.1%) children seronegative for antibodies to T. cruzi at baseline, with no history of travel or blood transfusion, seroconverted after three years. Six incident cases lived in houses heavily infested with T. infestans, with high proportions of bugs infected with T. cruzi and having fed on humans or dogs. The remaining incident case occurred under a very light domestic infestation detected only at the endpoint, and most bugs had fed on humans. Dogs had a 17 times greater force of infection than children (4.3% per year). Sustained vector surveillance is crucially needed in high-risk areas for Chagas disease such as the Gran Chaco. PMID:16014842

Distribution of Region 1 and 2 currents in the quietand substorm time plasma sheetfrom THEMIS observations

NASA Astrophysics Data System (ADS)

Liu, J.; Angelopoulos, V.; Chu, X.; McPherron, R. L.

2016-12-01

Although Earth's Region 1 and 2 currents are related to activities such as substorm initiation, their magnetospheric origin remains unclear. Utilizing the triangular configuration of THEMIS probes at 8-12 RE downtail, we seek the origin of nightside Region 1 and 2 currents. The triangular configuration allows a curlometer-like technique which do not rely on active-time boundary crossings, so we can examine the current distribution in quiet times as well as active times. Our statistical study reveals that both Region 1 and 2 currents exist in the plasma sheet during quiet and active times. Especially, this is the first unequivocal, in-situ evidence of the existence of Region 2 currents in the plasma sheet. Farther away from the neutral sheet than the Region 2 currents lie the Region 1 currents which extend at least to the plasma sheet boundary layer. At geomagnetic quiet times, the separation between the two currents is located 2.5 RE from the neutral sheet. These findings suggest that the plasma sheet is a source of Region 1 and 2 currents regardless of geomagnetic activity level. During substorms, the separation between Region 1 and 2 currents migrates toward (away from) the neutral sheet as the plasma sheet thins (thickens). This migration indicates that the deformation of Region 1 and 2 currents is associated with redistribution of FAC sources in the magnetotail. In some substorms when the THEMIS probes encounter a dipolarization, a substorm current wedge (SCW) can be inferred from our technique, and it shows a distinctively larger current density than the pre-existing Region 1 currents. This difference suggests that the SCW is not just an enhancement of the pre-existing Region 1 current; the SCW and the Region 1 currents have different sources.

Interannual and Decadal Variability of Summer Rainfall over South America

NASA Technical Reports Server (NTRS)

Zhou, Jiayu; Lau, K.-M.

1999-01-01

Using the CPC (Climate Prediction Center) Merged Analysis of Precipitation product along with the Goddard Earth Observing System reanalysis and the Climate Analysis Center sea surface temperature (SST) data, we conduct a diagnostic study of the interannual and decadal scale variability of summer rainfall over South America. Results show three leading modes of rainfall variation identified with interannual, decadal, and long-term trend variability. Together, these modes explain more than half the total variance. The first mode is highly correlated with El Nino/southern oscillation (ENSO), showing severe drought over Northeast Brazil and copious rainfall over the Ecuador coast and the area of Uruguay-Southern Brazil in El Nino years. This pattern is attributed to the large scale zonal shift of the Walker circulation and local Hadley cell anomaly induced by positive (negative) SST anomaly over the eastern (western) equatorial Pacific. In El Nino years, two convective belts indicated by upper tropospheric velocity potential trough and mid-tropospheric rising motion, which are somewhat symmetric about the equator, extend toward the northeast and the southeast into the tropical North and South Atlantic respectively. Sandwiched between the ascent is a region of descending motion over Northeast Brazil. The southern branch of the anomalous Hadley cell is dynamically linked to the increase of rainfall over Uruguay-Southern Brazil. The regional response of anomalous circulation shows a stronger South American summer monsoon and an enhanced (weakened) subtropical high over the South Atlantic (South Pacific) Ocean. The decadal variation displays a meridional shift of the Intertropical Convergence Zone (ITCZ), which is tie to the anomalous cross-equatorial SST gradient over the Atlantic and the eastern Pacific. In conjunction with this mode is a large scale mass swing between the polar regions and midlatitudes in both hemispheres. Over the South Atlantic and the South Pacific, the changes of the strength of the subtropical high and the associated surface wind are dynamically consistent with the distribution of local SST anomalies, suggesting the importance of the atmospheric forcing in the decadal time scale. The decadal mode also presents a weak summer monsoon in its positive phase, which reduces the moisture supply from the equatorial Atlantic and the Amazon Basin and results in negative rainfall anomalies over the central Andes and Gran Chaco. The long-term trend shows decrease of rainfall from the northwest coast to the southeast subtropical region and a southward shift of Atlantic ITCZ that leads to increased rainfall over northern and eastern Brazil. Our result shows a close link of this mode to the observed SST warming trend over the subtropical South Atlantic and a remote connection to the interdecadal SST variation over the extratropical North Atlantic found in previous studies.

Magnetotellurics applied to the study of the Guaraní aquifer in Entre Ríos Province, N-E Argentina

NASA Astrophysics Data System (ADS)

Favetto, Alicia; Curcio, Ana; Pomposiello, Cristina

2011-07-01

The South American Guaraní Aquifer System covers the entire Parana basin and part of the Chaco-Parana basin. This system is one of the most important groundwater reservoirs; it is shared by four neighboring countries covering an area larger than one million square kilometers. The geological units closely related to the Guaraní Aquifer are the Piramboia and Botucatu Formations that consist of Triassic-Jurassic aeolian, fluvial and lacustrine sandstones, and the Serra Geral basalts with clastic intercalations. Serra Geral, an effusive Cretaceous complex, covers the sandstones and provides a high degree of confinement to the system. This paper presents the interpretation of magnetotelluric (MT) data collected during 2007-2008 in Entre Ríos Province, Argentina. These data, recorded in three profiles, mainly provide the depth to the crystalline basement, determinant for the presence of aquifer-related sediments. Models showed that the discrimination of the basalts strongly depends on local electrical characteristics. Model information is quite consistent with the information from oil and thermal wells located close to the profiles.

Stage-Dependent Expression of Deltamethrin Toxicity and Resistance in Triatoma infestans (Hemiptera: Reduviidae) From Argentina.

PubMed

Germano, Mónica D; Picollo, María I

2018-02-20

Triatoma infestans Klug (Hemiptera: Reduviidae) is the main vector of Chagas disease in Latin America. This insect has been controlled with pyrethroids since the 1980s, although the emergence of resistance to deltamethrin has decreased control success in some areas of the Gran Chaco ecoregion. The response of T. infestans to deltamethrin was evaluated per developmental stage. In addition, we evaluated the possible stage-dependent expression of deltamethrin resistance. The bioassays were conducted by topical application of the insecticide in acetone. The drop size, age at the time of exposure, and mortality measuring time were standardized per stage. The lethal dose of deltamethrin moderately increased with the developmental stage. The resistance to deltamethrin was expressed in every instar, and was the highest in the fourth- and fifth-instar nymphs. While increasing, weight plays a relevant role in lethal dose stage dependency, a number of contributing factors such as degradative metabolism are probably involved in the variability of insecticide effect and resistance described for different T. infestans developmental stages. Possible explanations for these differences and their implications on resistance management and chemical control are discussed.

STS-65 Earth observation of dust plumes from Rio Grande in Southern Bolivia

NASA Technical Reports Server (NTRS)

1994-01-01

STS-65 Earth observation taken aboard Columbia, Orbiter Vehicle (OV) 102, is of dust plumes from the Rio Grande in Southern Bolivia. A series of dust plumes can be seen rising from sand banks in the Rio Grande of southern Bolivia, bottom right of this northeast-looking view. The Rio Grande brings sediment from the Andes (foothills visible in the foreground, bottom left) and flows across the flat country of the northern Chaco plain. During the low-flow season, sand banks of this sediment are exposed to northerly winds which often blow dust into the surrounding forest. One of the significances of the dust plumes is that dust acts as a source of nutrient for the local soils. This is the most impressive example of dust ever recorded on Shuttle photography from this river. Such plumes have been seen on photographs from four previous missions (STS-31, STS-47, STS-48, STS-51I) emanating from the Rio Grande. The plumes are regularly space because the sand is blown only from those reaches of th

Heterogeneities in the Ecoepidemiology of Trypanosoma cruzi Infection in Rural Communities of the Argentinean Chaco

PubMed Central

Cardinal, M. Victoria; Orozco, M. Marcela; Enriquez, Gustavo F.; Ceballos, Leonardo A.; Gaspe, María Sol; Alvarado-Otegui, Julián A.; Gurevitz, Juan M.; Kitron, Uriel; Gürtler, Ricardo E.

2014-01-01

We conducted a cross-sectional survey of Trypanosoma cruzi infection of Triatoma infestans as well as dogs and cats in 327 households from a well-defined rural area in northeastern Argentina to test whether the household distribution of infection differed between local ethnic groups (Tobas and Creoles) and identify risk factors for host infection. Overall prevalence of infection of bugs (27.2%; 95% confidence interval = 25.3–29.3%), dogs (26.0%; 95% confidence interval = 23.3–30.1%), and cats examined (28.7%; 95% confidence interval = 20.2–39.0%) was similar. A multimodel inference approach showed that infection in dogs was associated strongly with the intensity and duration of local exposure to infected bugs and moderately with household ethnic background. Overall, Toba households were at a substantially greater risk of infection than Creole households. The strong heterogeneities in the distribution of bug, dog, and cat infections at household, village, and ethnic group levels may be used for targeted vector and disease control. PMID:24732461

[Phlebotominae: vectors of leishmaniasis in the provinces of Santa Fe and Entre Ríos, Argentina].

PubMed

Salomón, Oscar D; Mocarbel, Nicolás J; Pedroni, Elena; Colombo, Javier; Sandillú, Mónica

2006-01-01

The transmission of tegumentary leishmaniasis (TL) has increased in 9 provinces of Argentina since 1985. Santa Fe and Entre Ríos did not record in this period autochtonous probed cases: however, an epidemic outbreak took place in 2003 in Bella Vista, Corrientes, located in an area with ecological continuity and contiguous to both provinces. In order to evaluate the potential risk of transmission of LT, Phlebotominae were captured at locations close to and southern from Bella Vista during February 2004. The traps located on the shores of Parana river in Santa Fe (El Rabón, Villa Ocampo, Cayastá), and Entre Ríos (La Paz. La Celina-Villa Urquiza) captured 860 individuals of Lutzomyia neivai (99.5%) and Lu. migonei (0.5 %), both species with vectorial capacity for Leishmania (V.) braziliensis. In Tartagal, Santa Fe, the captures were consistent with the residual "chaco" landscape, 7 individuals of Lu. nerivai, Lu. migonei and Lu. cortelezzii. The risk of LT epidemic transmission in these provinces is highlighted, mainly due to the progressive southern tropicalization of the paranaense gallery forest. Clinical and entomological surveillance is recommended.

Cancer incidence and pattern of arsenic concentration in drinking water wells in Córdoba, Argentina.

PubMed

Aballay, Laura Rosana; Díaz, María del Pilar; Francisca, Franco Matías; Muñoz, Sonia Edith

2012-01-01

Cancer occurrence is associated with Arsenic (As) in drinking water. In Argentina, there are high As concentrations in groundwater but there is no published evidence yet of an association between geographic patterns of cancer incidence and the distribution of As in groundwater supplies. The purpose of this study is to assess the association between cancer incidence patterns and As in Córdoba province's aquifers. Age standardized incidence rates (ASIRs) were obtained from Córdoba Cancer Registry (CCR), and As data from official reports of monitoring wells. A multilevel model was applied. Total ASIRs by aquifers for males/females were 191.01/249.22 (Rioja plain); 215.03/225.37 (Pampa hills); and 239.42/188.93 (Chaco-Pampa plain). As was associated with increased risk of colon cancer in women, and lung and bladder cancers in both sexes. It had no association with breast cancer. ASIRs were related to As, controlling for unobserved heterogeneity. An overlapping pattern of higher As and higher risks was evident for lung, bladder and female colon cancers.

Reducing leakage current in semiconductor devices

DOEpatents

Lu, Bin; Matioli, Elison de Nazareth; Palacios, Tomas Apostol

2018-03-06

A semiconductor device includes a first region having a first semiconductor material and a second region having a second semiconductor material. The second region is formed over the first region. The semiconductor device also includes a current blocking structure formed in the first region between first and second terminals of the semiconductor device. The current blocking structure is configured to reduce current flow in the first region between the first and second terminals.

Natural Distribution of Parasitoids of Larvae of the Fall Armyworm, Spodoptera frugiperda, in Argentina

PubMed Central

Gabriela Murúa, M.; Molina-Ochoa, Jaime; Fidalgo, Patricio

2009-01-01

To develop a better understanding of the natural distribution of the fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), and to update the knowledge of the incidence of its complex of parasitoids. S. frugiperda, samplings in whorl-stage corn were carried out in provinces of Argentina from 1999 to 2003. S. frugiperda larvae were collected from corn in localities of the provinces of Tucumán, Salta, Jujuy, Santiago del Estero, La Rioja, Córdoba, San Luis, Chaco and Misiones. In each locality 30 corn plants were sampled and only larvae located in those plants were collected. The parasitoids that emerged from S. frugiperda larvae were identified and counted. The abundance of the parasitoids and the parasitism rate were estimated. The S. frugiperda parasitoids collected were Campoletis grioti (Blanchard) (Hymenoptera: Ichneumonidae), Chelonus insularis (Cresson) (Hymenoptera: Braconidae), Archytas marmoratus (Townsend) (Diptera Tachinidae) and/or A. incertus (Macquart), Ophion sp. (Hymenoptera: Ichneumonidae), Euplectrus platyhypenae Howard (Hymenoptera: Eulophidae), and Incamyia chilensis (Aldrich) (Diptera Tachinidae). C. grioti was the most abundant and frequent during the five-year survey. Similar diversity of parasitoids was obtained in all the provinces, with the exception of I. chilensis and E. platyhypenae that were recovered only in the province of Salta. In the Northwestern region, in Tucumán, C. grioti and species of Archytas were the most abundant and frequent parasitoids. On the contrary, in Salta and Jujuy Ch. insularis was the parasitoid most abundant and frequently recovered. The parasitism rate obtained in Tucumán, Salta and Jujuy provinces were 21.96%, 17.87% and 6.63% respectively with an average of 18.93%. These results demonstrate that hymenopteran and dipteran parasitoids of S. frugiperda occurred differentially throughout the Argentinian provinces and played an important role on the natural control of the S. frugiperda larval population. PMID:19613463

Crustal deformation of the Andean foreland at 31° 30‧S (Argentina) constrained by magnetotelluric survey

NASA Astrophysics Data System (ADS)

Orozco, Luz Amparo; Favetto, Alicia; Pomposiello, Cristina; Rossello, Eduardo; Booker, John

2013-01-01

Twenty-five new long-period magnetotelluric sites near 31.5°S were collected in a west-east profile. This profile and the previous one, aligned with and adjacent to the eastern end, have been merged to form a single profile of more than 700 km long, extending from the Precordillera to the Chaco-Pampean Plain. The geotectonic scenario is characterized by a modern flat subduction zone of the Nazca plate located at a depth of around 120 km and clearly defined by the distribution of earthquake hypocenters recorded by local and regional networks. A "bulge" shape at 68.5°W, with an anomalous dip to the west, is observed within this segment. The smooth slab deformation might result from the restriction on eastward motion due to the presence of an electrically resistive zone. The magnetotelluric model shows that this thick zone of increased resistivity is found from shallow crustal levels to upper mantle depths. The bulge geometry allows hot fluids and volatiles to rise from the deeper asthenospheric wedge, and reach the lower crust reducing its viscosity and letting it flow. The zones of low resistivity in the lower crust show spatial correlation with the areas of foreland deformation from Precordillera to the Sierras Pampeanas and may also suggest a ductile regime. Shear zones reactivated by Cenozoic faulting must necessarily have their roots in the levels of the ductile lower crust associated to conductive channels. The zone where the lower crust is closer to the surface coincides with the areas of greatest structural relief and erosion. The interface between the folded ductile lower crust and the brittle upper crust might act as the main level of décollement of the bordering structures between the Precordillera, Sierra de Pie de Palo and the Sierras Pampeanas. In addition, the geometry of the interface might be conditioning the vergence of those structures.

Tectonic map of Uruguay

NASA Astrophysics Data System (ADS)

Sanchez Bettucci, L.; Oyhantcabal, P.

2008-05-01

A compilation of available data about the geology of Uruguay allowed the definition of its main events and tectonic units. Based on a critical revision of different tectonic hypothesis found in the literature, a parsimonious tectonic evolution schema is presented, in the context of Western Gondwana. The tectonic map illustrates the general features of the structure and main tectonic units of Uruguay. The Precambrian shield, cropping out in the South and Southeast of the country is an Archean to Paleoprtoerozoic basement divided in three main tectonostratigraphic terrranes: the Piedra Alta (PAT) a juvenile Paleoproterozoic unit not reworked by later events; the Nico Pérez (NPT) a complex unit composed of several blocks where Archean to Mesoproterozoic events are recognised. The NPT was strongly reworked by Neoproterozoic (Brasiliano) orogeny. The Dom Feliciano Belt cropping out in eastern Uruguay is related to Western Gondwana amalgamation. Different tectonic settings are considered: pre-Brasiliano Basement inliers; supracrustal successions representing the evolution from a back- arc to a foreland basin; a magmatic arc; and post-collisional basins and related magmatism. In lower Paleozoic the Paraná foreland basin was generated as a consequence of orogenic events. The sedimentary successions in Uruguay include continental to shallow marine deposits where the influence of carboniferous to Permian glacial episode is recorded. The Mesozoic record is characterised by the influence of extension related to the break-up of Gondwana and the formation of the Atlantic Ocean: huge amounts of tholeiitic basalt were erupted (near 30.000 km3 in Uruguay), followed by cretaceous sediments in the northern area of the country while in the south-east, bimodal magmatism and sediments of the same age are associated to rift basins. The Cenozoic is characterised by tectonic quiescence. Subsidence is only observed in the western region (Chaco-Paraná Basin) and in the east (Laguna Merín Basin).

Late Quaternary eolian and alluvial response to paleoclimate, Canyonlands, southeastern Utah

USGS Publications Warehouse

Reheis, M.C.; Reynolds, R.L.; Goldstein, H.; Roberts, H.M.; Yount, J.C.; Axford, Y.; Cummings, L.S.; Shearin, N.

2005-01-01

In upland areas of Canyonlands National Park, Utah, thin deposits and paleosols show late Quaternary episodes of eolian sedimentation, pedogenesis, and climate change. Interpretation of the stratigraphy and optically stimulated luminescence ages of eolian and nearby alluvial deposits, their pollen, and intercalated paleosols yields the following history: (1) Eolian deposition at ca. 46 ka, followed by several episodes of alluviation from some time before ca. 40 ka until after 16 ka (calibrated). (2) Eolian deposition from ca. 17 ka to 12 ka, interrupted by periods of pedogenesis, coinciding with late Pleistocene alluviation as local climate became warmer and wetter. (3) A wetter period from 12 to 8.5 ka corresponding to the peak of summer monsoon influence, during which soils formed relatively quickly by infiltration of eolian silt and clay, and trees and grasses were more abundant. (4) A drier period between ca. 8.5 and 6 ka during which sheetwash deposits accumulated and more desertlike vegetation was dominant; some dunes were reactivated at ca. 8 ka. (5) Episodic eolian and fluvial deposition during a wetter, cooler period that began at ca. 6 ka and ended by ca. 3-2 ka, followed by a shift to drier modern conditions; localized mobilization of dune sand has persisted to the present. These interpretations are similar to those of studies at the Chaco dune field, New Mexico, and the Tusayan dune field, Arizona, and are consistent with paleoclimate interpretations of pollen and packrat middens in the region. A period of rapid deposition and infiltration of eolian dust derived from distant igneous source terranes occurred between ca. 12 and 8 ka. Before ca. 17 ka, and apparently back to at least 45 ka, paleosols contain little or no such infiltrated dust. After ca. 8 ka, either the supply of dust was reduced or the more arid climate inhibited translocation of dust into the soils. ?? 2005 Geological Society of America.

Antispasmodic effects and composition of the essential oils from two South American chemotypes of Lippia alba.

PubMed

Blanco, Marcos A; Colareda, Germán A; van Baren, Catalina; Bandoni, Arnaldo L; Ringuelet, Jorge; Consolini, Alicia E

2013-10-07

Lippia alba (Mill.) N. E. Brown (Verbenaceae) is an aromatic species used in Central and South America as eupeptic for indigestion. In Argentina, it is used by the "criollos" from the Chaco province. There are several chemotypes which differ in the chemical composition of the essential oils. Nowadays, it is experimentally cultivated in some countries of the region, including Argentina. To compare the chemical composition and pharmacology of the essential oils from two chemotypes: "citral" (CEO) and "linalool" (LEO), in isolated rat duodenum and ileum. Contractile concentration-response curves (CRC) of acetylcholine (ACh) and calcium in 40mM K(+)-medium (Ca(2+)-CRC) were done in isolated intestine portions, in the absence and presence of CEO or LEO at different concentrations. Likewise verapamil, CEO and LEO induced a non-competitive inhibition of the ACh-CRC, with IC50 of 7.0±0.3mg CEO/mL and 37.2±4.2mg LEO/mL. l-NAME, a NO-synthase blocker, increased the IC50 of CEO to 26.1±8.7mg CEO/mL. Likewise verapamil, CEO and LEO non-competitively inhibited the Ca(2+)-CRC, with IC50 of 6.3±1.7mg CEO/mL, 7.0±2.5mg LEO/mL and 0.24±0.04mg verapamil/mL (pIC50: 6.28). CEO was proved to possess limonene, neral, geranial and (-)-carvone as the major components, while LEO was rich in linalool. Results suggest that CEO has five times more potency than LEO to inhibit muscarinic contractions. The essential oils of both chemotypes interfered with the Ca(2+)-influx, but with an IC50 about 28 times higher than that of verapamil. Moreover, CEO partially stimulated the NO production. These results show the medicinal usefulness of both Lippia alba chemotypes, thus validating its traditional use, potency and mechanism of action. © 2013 Published by Elsevier Ireland Ltd.

Cluster analysis applied to the spatial and temporal variability of monthly rainfall in Mato Grosso do Sul State, Brazil

NASA Astrophysics Data System (ADS)

Teodoro, Paulo Eduardo; de Oliveira-Júnior, José Francisco; da Cunha, Elias Rodrigues; Correa, Caio Cezar Guedes; Torres, Francisco Eduardo; Bacani, Vitor Matheus; Gois, Givanildo; Ribeiro, Larissa Pereira

2016-04-01

The State of Mato Grosso do Sul (MS) located in Brazil Midwest is devoid of climatological studies, mainly in the characterization of rainfall regime and producers' meteorological systems and rain inhibitors. This state has different soil and climatic characteristics distributed among three biomes: Cerrado, Atlantic Forest and Pantanal. This study aimed to apply the cluster analysis using Ward's algorithm and identify those meteorological systems that affect the rainfall regime in the biomes. The rainfall data of 32 stations (sites) of the MS State were obtained from the Agência Nacional de Águas (ANA) database, collected from 1954 to 2013. In each of the 384 monthly rainfall temporal series was calculated the average and applied the Ward's algorithm to identify spatial and temporal variability of rainfall. Bartlett's test revealed only in January homogeneous variance at all sites. Run test showed that there was no increase or decrease in trend of monthly rainfall. Cluster analysis identified five rainfall homogeneous regions in the MS State, followed by three seasons (rainy, transitional and dry). The rainy season occurs during the months of November, December, January, February and March. The transitional season ranges between the months of April and May, September and October. The dry season occurs in June, July and August. The groups G1, G4 and G5 are influenced by South Atlantic Subtropical Anticyclone (SASA), Chaco's Low (CL), Bolivia's High (BH), Low Levels Jet (LLJ) and South Atlantic Convergence Zone (SACZ) and Maden-Julian Oscillation (MJO). Group G2 is influenced by Upper Tropospheric Cyclonic Vortex (UTCV) and Front Systems (FS). The group G3 is affected by UTCV, FS and SACZ. The meteorological systems' interaction that operates in each biome and the altitude causes the rainfall spatial and temporal diversity in MS State.

SKS Anisotropy Measurements in Mid-Plate South America: a Test of Subduction-Induced Upper Mantle Flow and the Effect of Cratonic Keels

NASA Astrophysics Data System (ADS)

Assumpcao, M.; Melo, B. C.

2017-12-01

Shear-wave splitting from core-refracted (SKS) waves indicates the amount and orientation of seismic anisotropy in the upper mantle, and is used to infer past and present mantle dynamics and continental evolution. Previous SKS studies in South America concentrated mainly in the Andes and in SE Brazil. Although effects of frozen anisotropy in the lithospheric mantle were suggested in some parts of SE Brazil, the main contribution to the orientation of the fast polarization directions have been attributed to asthenospheric flow around cratonic keels, especially around the São Francisco craton in eastern Brazil (Assumpção et al., 2006,2011). We added extra SKS splitting measurements in the area of the Pantanal and Paraná-Chaco basins (FAPESP-funded "3-Basins" Project). Results from 47 new stations will be presented, both from the temporary deployments and from the Brazilian permanent net. This data set partly fills the gap in SKS measurements between the Andes and SE Brazil, providing a more complete and robust anisotropy map of the S. American stable platform. On average, over most of the mid-continent, the fast polarization orientation tends to be close to the absolute plate motion given by the hotspot reference frame HS3-NUVEL-1A. Nevertheless, the new and previously published fast polarizations results suggest mantle flow around the Amazon and São Francisco cratons. A comparison with recent modeling of upper mantle flow induced by the Nazca plate subduction (Hu et al., 2017) shows good agreement with the predictions of mantle flow around the Amazon craton. Further south, however, especially in the Pantanal Basin, the observed SKS fast orientations are ENE-WSW, deviating from the general ESE-WNW predicted orientations. We propose that the observed ENE-WSW orientation may be due to flow around a possible cratonic nucleus beneath the northern part of the Paraná Basin ("Paranapanema block"). This cratonic block (inferred from geological observations) is also seen in regional surface-wave tomography. Large delay times at the Pantanal Basin may indicate a stronger asthenospheric channel, a more coherent flow, or a thicker asthenosphere. Similarly, small delay times beneath the northern Paraná Basin may indicate thinner anisotropic asthenosphere in that region, similar to the observations in the Amazon craton.

Characterization of the IMF By-dependent field-aligned currents in the cleft region based on DE 2 observations

NASA Technical Reports Server (NTRS)

Taguchi, S.; Sugiura, M.; Winningham, J. D.; Slavin, J. A.

1993-01-01

The magnetic field and plasma data from 47 passes of DE-2 are used to study the IMF By-dependent distribution of field-aligned currents in the cleft region. It is proposed that the low-latitude cleft current (LCC) region is not an extension of the region 1 or region 2 current system and that a pair of LCCs and high-latitude cleft currents (HCCs) constitutes the cleft field-aligned current regime. The proposed pair of cleft field-aligned currents is explained with a qualitative model in which this pair of currents is generated on open field lines that have just been reconnected on the dayside magnetopause. The electric fields are transmitted along the field lines to the ionosphere, creating a poleward electric field and a pair of field-aligned currents when By is positive; the pair of field-aligned currents consists of a downward current at lower latitudes and an upward current at higher latitudes. In the By negative case, the model explains the reversal of the field-aligned current direction in the LCC and HCC regions.

Relationship between Birkeland current regions, particle precipitation, and electric fields

NASA Technical Reports Server (NTRS)

De La Beaujardiere, O.; Watermann, J.; Newell, P.; Rich, F.

1993-01-01

The relationship of the large-scale dayside Birkeland currents to large-scale particle precipitation patterns, currents, and convection is examined using DMSP and Sondrestrom radar observations. It is found that the local time of the mantle currents is not limited to the longitude of the cusp proper, but covers a larger local time extent. The mantle currents flow entirely on open field lines. About half of region 1 currents flow on open field lines, consistent with the assumption that the region 1 currents are generated by the solar wind dynamo and flow within the surface that separates open and closed field lines. More than 80 percent of the Birkeland current boundaries do not correspond to particle precipitation boundaries. Region 2 currents extend beyond the plasma sheet poleward boundary; region 1 currents flow in part on open field lines; mantle currents and mantle particles are not coincident. On most passes when a triple current sheet is observed, the convection reversal is located on closed field lines.

Differences in regional air trapping in current smokers with normal spirometry.

PubMed

Karimi, Reza; Tornling, Göran; Forsslund, Helena; Mikko, Mikael; Wheelock, Åsa M; Nyrén, Sven; Sköld, C Magnus

2017-01-01

We investigated regional air trapping on computed tomography in current smokers with normal spirometry. It was hypothesised that presence of regional air trapping may indicate a specific manifestation of smoking-related changes.40 current smokers, 40 patients with chronic obstructive pulmonary disease (COPD), and 40 healthy never- smokers underwent computed tomography scans. Regional air trapping was assessed on end-expiratory scans and emphysema, micronodules and bronchial wall thickening on inspiratory scans. The ratio of expiratory and inspiratory mean lung attenuation (E/I) was calculated as a measure of static (fixed) air trapping.Regional air trapping was present in 63% of current smokers, in 45% of never smokers and in 8% of COPD patients (p<0.001). Current smokers with and without regional air trapping had E/I ratio of 0.81 and 0.91, respectively (p<0.001). Forced expiratory volume in 1 s (FEV 1 ) was significantly higher and emphysema less frequent in current smokers with regional air trapping.Current smokers with regional air trapping had higher FEV 1 and less emphysema on computed tomography. In contrast, current smokers without regional air trapping resembled COPD. Our results highlight heterogeneity among smokers with normal spirometry and may contribute to early detection of smoking related structural changes in the lungs. Copyright ©ERS 2017.

Spectral and Imaging Observations of a Current Sheet Region in a Small-scale Magnetic Reconnection Event

NASA Astrophysics Data System (ADS)

Xue, Zhike; Yan, Xiaoli; Yang, Liheng; Wang, Jincheng; Feng, Song; Li, Qiaoling; Ji, Kaifan; Zhao, Li

2018-05-01

We report a possible current sheet region associated with a small-scale magnetic reconnection event by using the spectral and imaging observations of the Interface Region Imaging Spectrograph (IRIS) and the magnetograms obtained by the Solar Dynamics Observatory on 2016 August 08. The length and width of the current sheet region are estimated to be from 1.4 ± 0.1 Mm to 3.0 ± 0.3 Mm and from 0.34 ± 0.01 Mm to 0.64 ± 0.09 Mm, respectively. The evolutions of the length of the current sheet region are positively correlated with that of the width. These measurements are among the smallest reported. When the IRIS slit scans the current sheet region, the spectroscopic observations show that the Si IV line is broadened in the current sheet region and the plasma has a blueshifted feature at the middle and a redshifted feature at the ends of the current sheet region. The maximum measured blueshifted and redshifted Doppler velocities are ‑20.8 ± 0.9 and 34.1 ± 0.4 km s‑1, respectively. Additionally, the electron number densities of the plasma in the current sheet region are computed to be around 1011 cm‑3 based on the spectrums of the two O IV lines. The emergence, movement, and cancellation of a small sunspot with negative polarity are observed during the formation and shift of the current sheet region. We suggest that the occurrence and evolution of the magnetic reconnection are driven by the movement of the small sunspot in the photosphere.

The spatial pattern and dominant drivers of woody cover change in Latin America and Caribbean from 2001 to 2010

NASA Astrophysics Data System (ADS)

Clark, M.; Aide, T.; Riner, G.; Redo, D.; Grau, H.; Bonilla-Moheno, M.; Lopez-Carr, D.; Levy, M.

2011-12-01

Change in woody vegetation (i.e., forests, shrublands) is a major component of global environmental change: it directly affects biodiversity, the global carbon budget, and ecosystem function. For several decades, remote sensing technology has been used to document deforestation in Latin America and the Caribbean (LAC), although mostly at local to regional scales (e.g., moist forests of the Amazon basin). Most studies have focused on forest loss, some local-scale studies have mapped forest recovery, with contrasting forest dynamics attributed to shifting demographic and socio-economic factors. For example, local population change (rural-urban migration) can stimulate forest recovery on abandoned land, while increasing global food demand may drive regional expansion of mechanized agriculture. However, there are no studies in LAC that simultaneously map both loss and gain in woody vegetation at continental, national, and municipality scales with consistent data sources, methods and accuracy; and thus, we lack a comprehensive assessment of the spatial distribution of woody vegetation change and the relative importance of the multi-scale drivers of this change. We overcame this limitation by producing annual land-cover maps between 2001 and 2010 for each of the >16,000 municipalities in LAC. We focused on mapping municipality-scale trends in three broad classes: woody vegetation, mixed woody/plantations, and agriculture/herbaceous vegetation. Our area estimates show that woody vegetation change during the past decade was dominated by deforestation, or loss (-541,830 km2), particularly in the Amazon basin moist forest and the tropical-subtropical Cerrado and Chaco ecoregions, where large swaths of forest have been transformed to pastures and agricultural lands. Extensive areas (362,431 km2) in LAC also gained woody vegetation, particularly in regions too dry or too steep for modern agriculture, including the desert/xeric shrub biome in NE Brazil and northern Mexico, the conifer forest and tropical dry forest biomes in Central America, and Andean montane areas. We used Random Forests regression, a non-linear and non-parametric analytical technique, as a means to assess the relative importance of demographic and environmental variables in explaining trends in woody vegetation at the municipality scale. We found no association between population change and woody vegetation change at this scale, suggesting that global demand for food (e.g., soybean production for export to China) is a more important driver of deforestation than local population change. Our results emphasize that both loss and gain (i.e., deforestation and reforestation) need to be addressed in a research framework that links multiple spatial scales of land change with global drivers of change.

Comparison of DMSP and SECS region-1 and region-2 ionospheric current boundary

NASA Astrophysics Data System (ADS)

Weygand, J. M.; Wing, S.

2016-06-01

The region-1 and region-2 boundary has traditionally been identified using data from a single spacecraft crossing the auroral region and measuring the large scale changes in the cross track magnetic field. With data from the AUTUMN, CANMOS, CARISMA, GIMA, DTU MGS, MACCS, McMAC, STEP, THEMIS, and USGS ground magnetometer arrays we applied a state-of-art technique based on spherical elementary current system (SECS) method developed by Amm and Viljanen (1999) in order to calculate maps of region-1 and region-2 current system over the North American and Greenland auroral region. Spherical elementary current (SEC) amplitude (proxy for vertical currents) maps can be inferred at 10 s temporal resolution, ~1.5° geographic latitude (Glat), and 3.5° geographic longitude (Glon) spatial resolution. We compare the location of the region-1 and region-2 boundary obtained by the DMSP spacecraft with the region-1 and region-2 boundary observed in the SEC current amplitudes. We find that the boundaries typically agree within 0.2°±1.3°. These results indicate that the location of the region-1 and region-2 boundary can reasonably be determined from ground magnetometer data. The SECS maps represent a value-added product from the magnetometer database and can be used for contextual interpretation in conjunction with other missions as well as help with our understanding of magnetosphere-ionosphere coupling mechanisms using the ground arrays and the magnetospheric spacecraft data.

Comparison of DMSP and SECS region-1 and region-2 ionospheric current boundary✩

PubMed Central

Weygand, J.M.; Wing, S.

2017-01-01

The region-1 and region-2 boundary has traditionally been identified using data from a single spacecraft crossing the auroral region and measuring the large scale changes in the cross track magnetic field. With data from the AUTUMN, CANMOS, CARISMA, GIMA, DTU MGS, MACCS, McMAC, STEP, THEMIS, and USGS ground magnetometer arrays we applied a state-of-art technique based on spherical elementary current system (SECS) method developed by Amm and Viljanen (1999) in order to calculate maps of region-1 and region-2 current system over the North American and Greenland auroral region. Spherical elementary current (SEC) amplitude (proxy for vertical currents) maps can be inferred at 10 s temporal resolution, ~1.5° geographic latitude (Glat), and 3.5° geographic longitude (Glon) spatial resolution. We compare the location of the region-1 and region-2 boundary obtained by the DMSP spacecraft with the region-1 and region-2 boundary observed in the SEC current amplitudes. We find that the boundaries typically agree within 0.2° ± 1.3°. These results indicate that the location of the region-1 and region-2 boundary can reasonably be determined from ground magnetometer data. The SECS maps represent a value-added product from the magnetometer database and can be used for contextual interpretation in conjunction with other missions as well as help with our understanding of magnetosphere-ionosphere coupling mechanisms using the ground arrays and the magnetospheric spacecraft data. PMID:29056861

Comparison of DMSP and SECS region-1 and region-2 ionospheric current boundary.

PubMed

Weygand, J M; Wing, S

2016-06-01

The region-1 and region-2 boundary has traditionally been identified using data from a single spacecraft crossing the auroral region and measuring the large scale changes in the cross track magnetic field. With data from the AUTUMN, CANMOS, CARISMA, GIMA, DTU MGS, MACCS, McMAC, STEP, THEMIS, and USGS ground magnetometer arrays we applied a state-of-art technique based on spherical elementary current system (SECS) method developed by Amm and Viljanen (1999) in order to calculate maps of region-1 and region-2 current system over the North American and Greenland auroral region. Spherical elementary current (SEC) amplitude (proxy for vertical currents) maps can be inferred at 10 s temporal resolution, ~1.5° geographic latitude (Glat), and 3.5° geographic longitude (Glon) spatial resolution. We compare the location of the region-1 and region-2 boundary obtained by the DMSP spacecraft with the region-1 and region-2 boundary observed in the SEC current amplitudes. We find that the boundaries typically agree within 0.2° ± 1.3°. These results indicate that the location of the region-1 and region-2 boundary can reasonably be determined from ground magnetometer data. The SECS maps represent a value-added product from the magnetometer database and can be used for contextual interpretation in conjunction with other missions as well as help with our understanding of magnetosphere-ionosphere coupling mechanisms using the ground arrays and the magnetospheric spacecraft data.

Phylogenetic and biogeographic relationships of the mouse opossum Thylamys (Didelphimorphia, Didelphidae) in southern South America.

PubMed

Eduardo Palma, R; Rivera-Milla, Eric; Yates, Terry L; Marquet, Pablo A; Meynard, Andrés P

2002-11-01

Nucleotide sequence data from the mitochondrial cytochrome b gene were used to evaluate the phylogenetic relationships among mouse opossum species of the genus Thylamys. Based on approximately 1000 bp in five of the six species of the genus and including different localities for some of the species, we concluded that T. macrura from the subtropical forests of eastern Paraguay is the most primitive taxon. Subsequent radiation of the genus is explained mainly via founder effect speciation. This evolutionary scenario would account for the speciation of T. pusilla, T. venusta, T. pallidior, and T. elegans in the Chaco, southern Bolivia and northern Argentina, the Andean Altiplano, the Coastal Desert of Chile, and coastal Perú, respectively. Calibration of a molecular clock set the Pleistocene as the period for the differentiation of Thylamys species. The molecular results confirm the strong genetic connection between populations that inhabit the "pre-cordillera" of northern Chile (T. pallidior) and the canyons that run through the Atacama Desert to the lowlands in northern Chile. Our results confirm the occurrence of two Thylamys species in Chile, T. pallidior and T. elegans, within and south to the Atacama Desert, respectively. Copyright 2002 Elsevier Science (USA)

Potential application of Northern Argentine propolis to control some phytopathogenic bacteria.

PubMed

Ordóñez, R M; Zampini, I C; Moreno, M I Nieva; Isla, M I

2011-10-20

The antimicrobial activity of samples of Northern Argentine propolis (Tucumán, Santiago del Estero and Chaco) against phytopathogenic bacteria was assessed and the most active samples were identified. Minimal inhibitory concentration (MIC) values were determined by agar macrodilution and broth microdilution assays. Strong antibacterial activity was detected against Erwinia carotovora spp carotovora CECT 225, Pseudomonas syringae pvar tomato CECT 126, Pseudomonas corrugata CECT 124 and Xanthomonas campestris pvar vesicatoria CECT 792. The most active propolis extract (Tucumán, T1) was selected to bioguide isolation and identified for antimicrobial compound (2',4'-dihydroxychalcone). The antibacterial chalcone was more active than the propolis ethanolic extract (MIC values of 0.5-1 μg ml(-1) and 9.5-15 μg ml(-1), respectively). Phytotoxicity assays were realized and the propolis extracts did not retard germination of lettuce seeds or the growth of onion roots. Propolis solutions applied as sprays on tomato fruits infected with P. syringae reduced the severity of disease. Application of the Argentine propolis extracts diluted with water may be promising for the management of post harvest diseases of fruits. Copyright © 2010 Elsevier GmbH. All rights reserved.

Astronomical Heritage and Aboriginal People: Conflicts and Possibilities

NASA Astrophysics Data System (ADS)

Martín López, Alejandro

2015-08-01

In this presentation we will address the issues relating to the astronomical heritage of contemporary aboriginal groups and othe minorities. We will deal specially with the intangible astronomical heritage and their particularities. We will study (from the ethnographic experience with Aboriginal groups, Creoles and Europeans in the Argentine Chaco) the conflicts referring to the different ways, in which the native's knowledge and practice are categorized by the natives themselves, by the scientists, the state politicians, the professional artists and NGOs. We will address several cases to illustrate this kind of conflicts. We will analyze the complexities of patrimonial policies when it are applied to practices and representations of contemporary communities involved in power relations with national states and the global system. The essentialization of identities, the folklorization of representations and practices, the fossilization of aboriginal peoples are some of the risks of give the label of "cultural heritage" without a careful consideration of each specific case.In particular we will suggest possible forms by which he international scientific community could collaborate to improve the agenda of national states instead of reproducing colonial prejudices. In this way we will contribute to promote the respect for ethnic and religious minorities.

Astronomical Heritage and Aboriginal People: Conflicts and Possibilities

NASA Astrophysics Data System (ADS)

López, Alejandro Martín

2016-10-01

In this presentation we address issues relating to the astronomical heritage of contemporary aboriginal groups and other minorities. We deal specially with intangible astronomical heritage and its particularities. Also, we study (from ethnographic experience with Aboriginal groups, Creoles and Europeans in the Argentine Chaco) the conflicts referring to the different ways in which the natives' knowledge and practice are categorized by the natives themselves, by scientists, state politicians, professional artists and NGOs. Furthermore, we address several cases that illustrate these kinds of conflicts. We aim to analyze the complexities of patrimonial policies when they are applied to practices and representations of contemporary communities involved in power relations with national states and the global system. The essentialization of identities, the folklorization of representations and practices, and the fossilization of aboriginal peoples are some of the risks of applying the label ``cultural heritage'' without a careful consideration of each specific case. In particular we suggest possible ways in which the international scientific community could collaborate to improve the agenda of national states instead of reproducing colonial prejudices. In this way, we aim to contribute to the promotion of respect for ethnic and religious minorities.

Current structure and flow pattern on the electron separatrix in reconnection region

NASA Astrophysics Data System (ADS)

Guo, Ruilong; Pu, Zuyin; Wei, Yong

2017-12-01

Results from 2.5D Particle-in-cell (PIC) simulations of symmetric reconnection with negligible guide field reveal that the accessible boundary of the electrons accelerated in the magnetic reconnection region is displayed by enhanced electron nongyrotropy downstream from the X-line. The boundary, hereafter termed the electron separatrix, occurs at a few d e (electron inertial length) away from the exhaust side of the magnetic separatrix. On the inflow side of the electron separatrix, the current is mainly carried by parallel accelerated electrons, served as the inflow region patch of the Hall current. The out-of-plane current density enhances at the electron separatrix. The dominating current carriers are the electrons, nongyrotropic distribution functions of which contribute significantly to the perpendicular electron velocity by increasing the electron diamagnetic drift velocity. When crossing the separatrix region where the Hall electric field is enhanced, electron velocity orientation is changed dramatically, which could be a diagnostic indicator to detect the electron separatrix. In the exhaust region, ions are the main carriers for the out-of-plane current, while the parallel current is still mainly carried by electrons. The current density peak in the separatrix region implies that a thin current sheet is formed apart from the neutral line, which can evolve to the bifurcated current sheet.

Inferred flows of electric currents in solar active regions

NASA Technical Reports Server (NTRS)

Ding, Y. J.; Hong, Q. F.; Hagyard, M. J.; Deloach, A. C.

1985-01-01

Techniques to identify sources of major current systems in active regions and their channels of flow are explored. Measured photospheric vector magnetic fields together with high resolution white light and H-alpha photographs provide the data base to derive the current systems in the photosphere and chromosphere of a solar active region. Simple mathematical constructions of active region fields and currents are used to interpret these data under the assumptions that the fields in the lower atmosphere (below 200 km) may not be force free but those in the chromosphere and higher are. The results obtained for the complex active region AR 2372 are: (1) Spots exhibiting significant spiral structure in the penumbral filaments were the source of vertical currents at the photospheric surface; (2) Magnetic neutral lines where the transverse magnetic field was strongly sheared were channels along which a strong current system flowed; (3) The inferred current systems produced a neutral sheet and oppositely-flowing currents in the area of the magnetic delta configuration that was the site of flaring.

On the energy budget in the current disruption region. [of geomagnetic tail

NASA Technical Reports Server (NTRS)

Hesse, Michael; Birn, Joachim

1993-01-01

This study investigates the energy budget in the current disruption region of the magnetotail, coincident with a pre-onset thin current sheet, around substorm onset time using published observational data and theoretical estimates. We find that the current disruption/dipolarization process typically requires energy inflow into the primary disruption region. The disruption dipolarization process is therefore endoenergetic, i.e., requires energy input to operate. Therefore we argue that some other simultaneously operating process, possibly a large scale magnetotail instability, is required to provide the necessary energy input into the current disruption region.

Some climatic indicators in the period A.D. 1200-1400 in New Mexico

USGS Publications Warehouse

Leopold, Luna Bergere; Leopold, Estella B.; Wendorf, F.

1963-01-01

Three centuries before Columbus landed in America, the alluvial valleys of the south-western United States teemed with activity. The indigenous peoples had been building for 300 years a culture centred around community life based on flood-water farming and on hunting. A large number of pueblos had developed on sites earlier occupied by pit-house people. Community organization had brought advances in the ceramic and decorative arts, and changes in these artistic activities were sufficiently rapid that accurate chronologies have become available through the work of archaeologists during the twentieth century. These chronologies were at first unrelated to absolute dates, but the excavations of the 1920s at Chaco Canyon (New Mexico) provided the materials through which absolute dates could be established. This was accomplished by matching the changes in tree-ring width backward in time from living trees through successively older samples. Trees overlapping in age provided, by unique successions of distinctive tree-ring widths, a calendar by which individual logs could be dated. Beams found in the excavations at Chaco Canyon gave the first material by which the cultural developments culminating about A.D. 1300 could be dated.As a result of the time sequence provided by the tree-ring calendar, the dates within which different pottery types were developed could be accurately established. The dates of pottery types have been checked at a sufficiently large number of sites throughout the south-western United States that absolute dating of a large number of distinctive patterns can be considered unassailable. The sequence of tree-ring widths gives some climatic indications of great interest both to archaeologists and to climatologists. A relatively large number of logs spanning the period from A.D. 1200 to 1300 and, in particular, the years between 1276 and 1299, indicate that this period was generally characterized by smaller tree-ring widths than in the centuries immediately before and after. As a first approximation, the hundred years of narrow tree-ring widths were interpreted as a time of relative aridity, and have been referred to as the “Pueblo Drought”. More recent studies of tree-ring widths using sophisticated statistical techniques have thrown some doubts on any direct correlation of tree-ring widths with rainfall. Such doubts have been put forward before by Glock (1955) whose studies have been aimed at separating the various effects of seasonal occurrence of precipitation, the amount falling in various seasons, and other climatic factors in their relative influence on tree-ring widths. At present, then, tree-ring widths may be considered more satisfactory for reading chronology than for reading climate. It is this concern about direct correlation of tree-ring width with climate that led to initiation of the present study. This work is a preliminary attempt to obtain independent evidence from pollen concerning the probable nature of the vegetation and thus the climate in a period known to be characterized by narrow tree rings.

Contribution of the graded region of a HgCdTe diode to its saturation current

NASA Technical Reports Server (NTRS)

Schacham, S. E.; Finkman, E.

1990-01-01

Experimental results show that the contribution of the graded region to the current of Hg(1-x)Cd(x)Te diodes is not negligible, as compared to that of the p type bulk. The theoretical analysis reveals the influence of the electric field present outside the depletion region on the current generated by the graded region. The analysis shows the importance of the lifetime profile in the graded region, which is a function of the specific recombination mechanism and its dependence on the local dopant concentration. The effect of parameters such as substrate concentration, surface concentration, and junction depth on this current is discussed.

Current collectors for improved safety

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdelmalak, Michael Naguib; Allu, Srikanth; Dudney, Nancy J.

A battery electrode assembly includes a current collector with conduction barrier regions having a conductive state in which electrical conductivity through the conduction barrier region is permitted, and a safety state in which electrical conductivity through the conduction barrier regions is reduced. The conduction barrier regions change from the conductive state to the safety state when the current collector receives a short-threatening event. An electrode material can be connected to the current collector. The conduction barrier regions can define electrical isolation subregions. A battery is also disclosed, and methods for making the electrode assembly, methods for making a battery, andmore » methods for operating a battery.« less

Heating the sun's lower transition region with fine-scale electric currents

NASA Technical Reports Server (NTRS)

Rabin, D.; Moore, R.

1984-01-01

Analytical and observational data are presented to show that the lower transition zone, a 100 km thick region at 10,000-200,000 K between the solar chromosphere and corona, is heated by local electric currents. The study was spurred by correlations between the enhanced atmospheric heating and magnetospheric flux in the chromospheric network and active regions. Field aligned current heated flux loops are asserted to mainly reside in and make up most of the transition region. It is shown that thermal conduction from the sides of hot gas columns generated by the current dissipation is the source of the observed temperature distribution in the transition regions.

SEQUENCE STRATIGRAPHIC ANALYSIS AND FACIES ARCHITECTURE OF THE CRETACEOUS MANCOS SHALE ON AND NEAR THE JICARILLA APACHE INDIAN RESERVATION, NEW MEXICO-THEIR RELATION TO SITES OF OIL ACCUMULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jennie Ridgley

2000-03-31

Oil distribution in the lower part of the Mancos Shale seems to be mainly controlled by fractures and by sandier facies that are dolomite-cemented. Structure in the area of the Jicarilla Apache Indian Reservation consists of the broad northwest- to southeast-trending Chaco slope, the deep central basin, and the monocline that forms the eastern boundary of the San Juan Basin. Superimposed on the regional structure are broad low-amplitude folds. Fractures seem best developed in the areas of these folds. Using sequence stratigraphic principals, the lower part of the Mancos Shale has been subdivided into four main regressive and transgressive components.more » These include facies that are the basinal time equivalents to the Gallup Sandstone, an overlying interbedded sandstone and shale sequence time equivalent to the transgressive Mulatto Tongue of the Mancos Shale, the El Vado Sandstone Member which is time equivalent to part of the Dalton Sandstone, and an unnamed interbedded sandstone and shale succession time equivalent to the regressive Dalton Sandstone and transgressive Hosta Tongue of the Mesaverde Group. Facies time equivalent to the Gallup Sandstone underlie an unconformity of regional extent. These facies are gradually truncated from south to north across the Reservation. The best potential for additional oil resources in these facies is in the southern part of the Reservation where the top sandier part of these facies is preserved. The overlying unnamed wedge of transgressive rocks produces some oil but is underexplored, except for sandstones equivalent to the Tocito Sandstone. This wedge of rocks is divided into from two to five units. The highest sand content in this wedge occurs where each of the four subdivisions above the Tocito terminates to the south and is overstepped by the next youngest unit. These terminal areas should offer the best targets for future oil exploration. The El Vado Sandstone Member overlies the transgressive wedge. It produces most of the oil (except for the Tocito Sandstone) from the lower Mancos. In the central and southern part of the Reservation, large areas, currently not productive or not tested, have the potential to contain oil in the El Vado simply based on the trend of the facies and structure. There has been little oil or gas production from the overlying regressive-transgressive wedge of rock and much of this interval is untested. Thus, large areas of the Reservation could contain hydrocarbon resources in these strata. Most of the Reservation lies within the oil generation window based on new Rock-Eval data from the Mancos Shale just south of the southern part of the Reservation. If these observations are valid then oil could have been generated locally and would only have needed to migrate short distances in to sandy reservoirs and fractures. This does not rule out long distance migration of oil from the deeper, more thermally mature part of the basin to the north. However, low porosity and permeability characterize sandier rocks in the Mancos, with the exception of Tocito-like sandstones. These factors could retard long distance oil migration through the sediment package, except through fracture or fault conduits. Thus, it is suggested that future oil and gas explorations in the Mancos treat the accumulations and reservoirs as unconventional and consider whether the source and reservoir are in closer proximity than has previously been assumed.« less

High latitude currents in the 0600 to 0900 MLT sector - Observations from Viking and DMSP-F7

NASA Technical Reports Server (NTRS)

Bythrow, P. F.; Potemra, T. A.; Zanetti, L. J.; Erlandson, R. A.; Hardy, D. A.; Rich, F. J.; Acuna, M. H.

1987-01-01

High-resolution magnetic field and charged-particle data acquired on March 25, 1986 by the Viking and DMSP-F7 satellites, as they traversed the dawn sector auroral zone on nearly antiparallel trajectories within 40 min of each oher, are analyzed. Magnetic field measurements by Viking at 0850 MLT and by DMSP at 0630 MLT indicate the presence of a large-scale earthward-directed region 1 Birkeland current and an upward-flowing region 2 current. Both satellites also observed a third Birkeland current adjacent to and poleward of the region 1 system with opposite flow. This poleward system is about 0.5 deg invariant latitude wide and has a current density comparable to the region 1 and 2 systems. The highest-latitude current is identified as region 0. Its charged-particle signatures were used to infer field line mapping to the equatorial plane.

[The Hessian care monitor. Transparency on regional labor markets].

PubMed

Lauxen, O; Bieräugel, R

2013-08-01

The Hessian Care Monitor is a Web-based monitoring system of the regional care labor market. It contains information on the current labor market and on future developments. Official statistics are analyzed, primary data are collected, and forecasts are calculated. Since 2008, the demand for nurses in Hesse has been higher than the supply. In 2010, there was a lack of more than 4,400 nurses. Moreover, in 2025, around 5,500 additional nurses will be needed to meet the increasing demand arising from demographic changes. However, there are three different regional patterns: regions with high current shortages but little additional demand in the future; regions with low current shortages but large future needs; and regions with high current shortages and large future demand. Appropriate strategies for handling labor shortages have to be selected according to the different regional patterns.

Structure of Dilute Pyroclastic Density Currents During Transport, Buoyancy Reversal and Liftoff

NASA Astrophysics Data System (ADS)

Andrews, B. J.

2014-12-01

Scaled laboratory experiments provide insight into structure, entrainment and liftoff in pyroclastic density currents (PDCs). Experiments are conducted in a 8.5×6.1×2.6 m air-filled tank and comprise turbulently suspended mixtures of heated 20-μm talc particles introduced to the tank at steady and sustained rates; the tank is large enough that the currents are effectively unconfined. Experiments are scaled with bulk (densimetric and thermal Richardson numbers, Froude number) and turbulent (Stokes and settling numbers) parameters dynamically similar to natural currents. The Reynolds numbers of experiments are smaller than those of natural PDCs, but analysis of the experiments demonstrates that they are fully turbulent. Red, green, and blue laser sheets illuminate orthogonal planes within the currents for imaging and recording with HD video cameras; those data are reprojected into cross-sectional and map-view planes for analysis of turbulent velocity fields and fluctuations in particle concentration. A green laser sheet can be swept through the tank at 60 Hz and imaged with a high-speed CCD camera at up to 3000 fps; sequences of 60-300 images are used to make 3D volumetric reconstructions of the currents at up to 10 Hz. Currents typically comprise a lower "bypass" region and an upper entraining region that turbulently mixes with the ambient air. The bypass region is generally about half of the total current thickness and moves faster than the overlying, entraining region. The bypass region controls runout distance and steadiness of currents. If turbulent structures in the entraining region penetrate through the bypass region, the trailing portion of the current can stall before resuming forward progress; thus a single, "steady" current can generate multiple currents. When a current lifts off, it focuses along a narrow axis beneath the rising (coignimbrite) plume. At that time, ambient air entrainment occurs primarily through the lateral margins of the narrow bypass region. Eddies that entrain air through the lateral margins grow in size with transport distance such that at the maximum runout distance, eddies have lengthscales comparable to the current width. The largest structures within the rising plumes have lengthscales comparable to the cross-stream plume width.

Current depression among women in California according to residence in the California-Mexico border region.

PubMed

Ryan-Ibarra, Suzanne; Epstein, Joan Faith; Induni, Marta; Wright, Michael A

2012-05-01

To estimate the prevalence of current depression; examine the relationship between current depression and immigration, health status, health care access, and health behaviors; and assess differences by California-Mexico border region (Imperial and San Diego Counties) among women in California. Using a cross-sectional, representative sample of adult women from the California Women's Health Survey (n = 13 454), a statewide telephone survey, prevalence of current depression and predictors of depression were examined in California and according to border region residence. Depression was assessed with the eight-item Patient Health Questionnaire. The prevalence of current depression for women in California was 12.0%. It was similar in the border (13.0%) and the nonborder (11.9%) regions. Odds of current depression in women were lower among recent immigrants (< 5 years or 5 to < 10 years in the United States) than in women born in the United States and in immigrants who had been living in the United States for 10 to < 15 years or longer (P < 0.05). Odds ratios for current depression and health status, health care access, and binge drinking were larger in the border region than outside the border region. Similar prevalences of current depression were observed among those who live in the border region of California and in those who do not, but the relationship between depression and health status, health care access, and binge drinking varied by border region residence. Ideally, future surveillance of depression and its predictors along the Mexico-California border will be conducted binationally to inform interventions and tracking such as the Healthy Border Program's objectives.

The Role of Nongyrotropy in Balancing the Reconnection Diffusion Region

NASA Astrophysics Data System (ADS)

Hesse, M.; Liu, Y. H.; Chen, L. J.; Bessho, N.; Wang, S.; Burch, J. L.; Moretto, T.; Genestreti, K.; Phan, T.; Tenfjord, P.

2017-12-01

The structure of the reconnection diffusion region is, to a large degree, determined by the requirement to balance both the current flow and its dissipation processes, and the forces exerted onto the current layer by the inflow magnetic pressure. These balances are critical: without resupply processes, the transport of accelerated and current-carrying particles away from the diffusion region would generate a current density depletion, which, in principle, could lead to a mismatch with the curl of the magnetic field. Similarly, without heating processes, the convection of hot plasma away from the diffusion region would generate a force imbalance with the ambient magnetic field. The fact that neither of these imbalances occur is a consequence of the reconnection electric field, which is therefore not only required to facilitate magnetic flux transport, but also to provide the energization required to maintain balance in the diffusion region. In this presentation, we will use particle-in-cell simulations to analyze these balance conditions. We will furthermore show that nongyrotropic particle dynamics plays a key role both as current dissipation mechanism, and as overall heating mechanism in the diffusion region current layer.

Tidal residual current and its role in the mean flow on the Changjiang Bank

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xuan, Jiliang; Yang, Zhaoqing; Huang, Daji

Tidal residual current may play an important role in the mean flow in the Changjiang Bank region, in addition to other residual currents, such as the Taiwan Warm Current, the Yellow Sea Coastal Current, and the Yellow Sea Warm Current. In this paper, a detailed structure of the tidal residual current, in particular the meso-scale eddies, in the Changjiang Bank region is observed from model simulations, and its role in the mean flow is quantified using the well-validated Finite Volume Coastal Ocean Model). The tidal residual current in the Changjiang Bank region consists of two components: an anticyclonic regional-scale tidalmore » residual circulation around the edge of the Changjiang Bank and some cyclonic meso-scale tidal residual eddies across the Changjiang Bank. The meso-scale tidal residual eddies occur across the Changjiang Bank and contribute to the regional-scale tidal residual circulation offshore at the northwest boundary and at the northeast edge of the Changjiang Bank, southeastward along the 50 m isobath. Tidal rectification is the major mechanism causing the tidal residual current to flow along the isobaths. Both components of the tidal residual current have significant effects on the mean flow. A comparison between the tidal residual current and the mean flow indicates that the contribution of the tidal residual current to the mean flow is greater than 50%.« less

Tidal residual current and its role in the mean flow on the Changjiang Bank

NASA Astrophysics Data System (ADS)

Xuan, Jiliang; Yang, Zhaoqing; Huang, Daji; Wang, Taiping; Zhou, Feng

2016-02-01

The tidal residual current may play an important role in the mean flow in the Changjiang Bank region, in addition to other residual currents, such as the Taiwan Warm Current, the Yellow Sea Coastal Current, and the Yellow Sea Warm Current. In this paper, a detailed structure of the tidal residual current, in particular the meso-scale eddies, in the Changjiang Bank region is observed from model simulations, and its role in the mean flow is quantified using the well-validated Finite Volume Coastal Ocean Model. The tidal residual current in the Changjiang Bank region consists of two components: an anticyclonic regional-scale tidal residual circulation around the edge of the Changjiang Bank and some cyclonic meso-scale tidal residual eddies across the Changjiang Bank. The meso-scale tidal residual eddies occur across the Changjiang Bank and contribute to the regional-scale tidal residual circulation offshore at the northwest boundary and on the northeast edge of the Changjiang Bank, southeastward along the 50 m isobath. Tidal rectification is the major mechanism causing the tidal residual current to flow along the isobaths. Both components of the tidal residual current have significant effects on the mean flow. A comparison between the tidal residual current and the mean flow indicates that the contribution of the tidal residual current to the mean flow is greater than 50%.

The Role of Ring Current on Slot Region Penetration

NASA Technical Reports Server (NTRS)

Fok, Mei-Ching; Elkington, Scot

2006-01-01

During magnetic quiet times, the inner belt, slot region and the outer belt are well defined regions. However, during some major storms, outer belt particles penetrate inward and significantly fill the slot region. In some extreme events, the outer belt particles travel through the slot and create a new belt in the inner region that persists from months to years. In this paper, we examine the role of the ring current on this radiation belt penetration into the slot region. The storm-time intensification of the ring current produces strong magnetic depression in the inner magnetosphere. This perturbation and its fluctuation enhance the radial transport and diffusion of the outer radiation belt particles. We perform kinetic and test-particle calculations to quantitatively assess the effects of the ring current field on filling of the slot region. Simulation results during major storms will be presented and discussed.

Strongly-sheared wind-forced currents in the nearshore regions of the central Southern California Bight

USGS Publications Warehouse

Noble, Marlene A.; Rosenberger, Kurt; Robertson, George L.

2015-01-01

Contrary to many previous reports, winds do drive currents along the shelf in the central portion of the Southern California Bight (SCB). Winds off Huntington Beach CA are the dominant forcing for currents over the nearshore region of the shelf (water depths less than 20 m). Winds control about 50–70% of the energy in nearshore alongshelf surface currents. The wind-driven current amplitudes are also anomalously high. For a relatively weak 1 dyne/cm2 wind stress, the alongshelf surface current amplitudes in this region can reach 80 cm/s or more. Mid-depth current amplitudes for the same wind stress are around 30–40 cm/s. These wind-driven surface current amplitudes are much larger than previously measured over other nearshore shelf regions, perhaps because this program is one of the few that measured currents within a meter of the surface. The near-bed cross-shelf currents over the nearshore region of the Huntington Beach shelf have an Ekman response to winds in that they upwell (downwell) for down (up) coast winds. This response disappears further offshore. Hence, there is upwelling in the SCB, but it does not occur across the entire shelf. Subthermocline water in the nearshore region that may contain nutrients and plankton move onshore when winds are southeastward, but subthermocline water over the shelf break is not transported to the beach. The currents over the outer shelf are not predominately controlled by winds, consistent with previous reports. Instead, they are mainly driven by cross-shelf pressure gradients that are independent of local wind stress.

Resistance to deltamethrin by domestic and wild Triatoma infestans populations in the municipality of Toro Toro, Potosi, Bolivia.

PubMed

Echeverria, Jorge Espinoza; Bustamante Gomez, Marinely B; Pessoa, Grasielle Caldas D Ávila; Cortez, Mirko Rojas; Rodriguez, Antonio Nogales; Diotaiuti, Liléia Gonçalves

2018-02-17

Chemical control with pyrethroid insecticides has been effective in reducing endemic areas of distribution of Triatoma infestans in the Southern Cone, as well as Bolivia; this had considerably reduced the infestation of households in a large part of the territory. Nowadays, areas such as the Chaco and the Inter-Andean Valleys are regions where the reach of vector control strategies is becoming limited, and infestations of insecticide-treated households are reported more often. The objective of this study was to determine if the persistence of T. infestans stems from changes in the susceptibility of its toxicological profile in four communities in the municipality of Toro Toro, Potosi, Bolivia. Susceptibility to deltamethrin of wild and domestic populations of T. infestans was evaluated in two stages (16 populations before and 13 populations after spraying) among DUs (structures in the intra- and peridomicile) and wild ecotopes, in four communities. Serial dilutions of deltamethrin in acetone (0.2 μl) were applied topically on standardized first-stage nymphs. Dose-response results were analyzed with the software PoloPlus and the relationships between lethal doses (LD) and resistance ratios (RR 50 ) were determined. Different degrees of RR 50 were detected among the populations before and after spraying (25.66-54.70 and 21.91-40.67, respectively), as well as in different ecotopes within a DU (DU JC 3, 28.06-36.13, in mixed structures of corrals and chicken coops; and DU JG 3, 46.27-25.70, in kitchen roofs), or in the wild environment of the community JG Sil (29.21-40.67). The mortality of insects undergoing diagnostic dose (DD) was never higher than 34%. The results obtained in this study showed resistance of T. infestans to deltamethrin in four communities, hence the complexity of this phenomenon is not only limited to the level of communities, but also applies to the microgeographical level, as in different ecotopes present within the DUs. This phenomenon should be considered while planning the activities of control programs.

Photospheric electric current and transition region brightness within an active region

NASA Technical Reports Server (NTRS)

Deloach, A. C.; Hagyard, M. J.; Rabin, D.; Moore, R. L.; Smith, B. J., Jr.; West, E. A.; Tandberg-Hanssen, E.

1984-01-01

Distributions of vertical electrical current density J(z) calculated from vector measurements of the photospheric magnetic field are compared with ultraviolet spectroheliograms to investigate whether resistive heating is an important source of enhanced emission in the transition region. The photospheric magnetic fields in Active Region 2372 were measured on April 6 and 7, 1980 with the Marshall Space Flight Center vector magnetograph; ultraviolet wavelength spectroheliograms (L-alpha and N V 1239 A) were obtained with the UV Spectrometer and Polarimeter experiment aboard the Solar Maximum Mission satellite. Spatial registration of the J(z) (5 arcsec resolution) and UV (3 arcsec resolution) maps indicates that the maximum current density is cospatial with a minor but persistent UV enhancement, but there is little detected current associated with other nearby bright areas. It is concluded that, although resistive heating may be important in the transition region, the currents responsible for the heating are largely unresolved in the present measurements and have no simple correlation with the residual current measured on 5-arcsec scales.

Observations of Magnetosphere-Ionosphere Coupling Processes in Jupiter's Downward Auroral Current Region

NASA Astrophysics Data System (ADS)

Clark, G. B.; Mauk, B.; Allegrini, F.; Bagenal, F.; Bolton, S. J.; Bunce, E. J.; Connerney, J. E. P.; Ebert, R. W.; Gershman, D. J.; Gladstone, R.; Haggerty, D. K.; Hospodarsky, G. B.; Kotsiaros, S.; Kollmann, P.; Kurth, W. S.; Levin, S.; McComas, D. J.; Paranicas, C.; Rymer, A. M.; Saur, J.; Szalay, J. R.; Tetrick, S.; Valek, P. W.

2017-12-01

Our view and understanding of Jupiter's auroral regions are ever-changing as Juno continues to map out this region with every auroral pass. For example, since last year's Fall AGU and the release of publications regarding the first perijove orbit, the Juno particles and fields teams have found direct evidence of parallel potential drops in addition to the stochastic broad energy distributions associated with the downward current auroral acceleration region. In this region, which appears to exist in an altitude range of 1.5-3 Jovian radii, the potential drops can reach as high as several megavolts. Associated with these potentials are anti-planetward electron angle beams, energetic ion conics and precipitating protons, oxygen and sulfur. Sometimes the potentials within the downward current region are structured such that they look like the inverted-V type distributions typically found in Earth's upward current region. This is true for both the ion and electron energy distributions. Other times, the parallel potentials appear to be intermittent or spatially structured in a way such that they do not look like the canonical diverging electrostatic potential structure. Furthermore, the parallel potentials vary grossly in spatial/temporal scale, peak voltage and associated parallel current density. Here, we present a comprehensive study of these structures in Jupiter's downward current region focusing on energetic particle measurements from Juno-JEDI.

Investigation of the double exponential in the current-voltage characteristics of silicon solar cells. [proton irradiation effects on ATS 1 cells

NASA Technical Reports Server (NTRS)

Wolf, M.; Noel, G. T.; Stirn, R. J.

1977-01-01

Difficulties in relating observed current-voltage characteristics of individual silicon solar cells to their physical and material parameters were underscored by the unexpected large changes in the current-voltage characteristics telemetered back from solar cells on the ATS-1 spacecraft during their first year in synchronous orbit. Depletion region recombination was studied in cells exhibiting a clear double-exponential dark characteristic by subjecting the cells to proton irradiation. A significant change in the saturation current, an effect included in the Sah, Noyce, Shockley formulation of diode current resulting from recombination in the depletion region, was caused by the introduction of shallow levels in the depletion region by the proton irradiation. This saturation current is not attributable only to diffusion current from outside the depletion region and only its temperature dependence can clarify its origin. The current associated with the introduction of deep-lying levels did not change significantly in these experiments.

Simultaneous prenoon and postnoon observations of three field-aligned current systems from Viking and DMSP-F7

NASA Technical Reports Server (NTRS)

Ohtani, S.; Potemra, T. A.; Newell, P. T.; Zanetti, L. J.; Iijima, T.; Watanabe, M.; Yamauchi, M.; Elphinstone, R. D.; De La Beauijardie, O.; Blomberg, L. G.

1995-01-01

The spatial structure of dayside large-scale field-aligned current (FAC) systems is examined by using Viking and Defense Meteorological Satellite Program-F7 (DMSP-F7) data. We focus on four events in which the satellites simultaneously observed postnoon and prenoon three FAC systems: the region 2, the region 1, and the mantle (referred to as midday region O) systems, from equatorward to poleward. These events provide the most solid evidence to date that the midday region O system is a separate and unique FAC system, and is not an extension of the region 1 system from other local times. The events are examined comprehensively by making use of a mulit-instrumental data set, which includes magnetic field, particle flux, electric field, auroral UV image data from the satellites, and the Sondrestrom convection data. The results are summarized as follows: (1) Region 2 currents flow mostly in the central plasma sheet (CPS) precipitation region, often overlapping with the boundary plasma sheet (BPD) at their poleward edge. (2) The region 1 system is located in the core part of the auroral oval and is confined in a relatively narrow range in latitude which includes the convection reversal. The low-latitude boundary layer, possibly including the outer part of the plasma sheet, and the external cusp are the major source regions of dayside region 1 currents. (2) Midday region O currents flow on open field lines and are collocated with the shear of antisunward convection flows with velocites decreasing poleward. On the basis of these results we support the view that both prenoon and postnoon current systems consist of the three-sheet structure when the disctortion ofthe convection pattern associated with interplanetary magnetic field (IMF) B(sub Y) is small and both morningside and eveningside convection cells are crescent-shaped. We also propose that the midday region O and a part of the region 1 systems are closely coupled to the same source.

Analysis of the transmission of Trypanosoma cruzi infection through hosts and vectors.

PubMed

Fabrizio, María C; Schweigmann, Nicolás J; Bartoloni, Norberto J

2016-08-01

Calculating epidemiological measures of infection by Trypanosoma cruzi, the causative agent of Chagas disease, is complex, because it involves several species, different stages of infection in humans and multiple transmission routes. Using the next-generation matrix method, we analysed a model which considers the three stages of human infection, triatomines and dogs (the main domestic reservoirs of T. cruzi when triatomines are present) and the main transmission routes. We derived R 0 and type-reproduction numbers T. We deduced formulas for the number of new infections generated through each transmission route by each infected individual. We applied our findings in Argentine Gran Chaco. The expressions achieved allowed quantifying the high infectivity of dogs and emphasizing the epidemiological importance of the long and asymptomatic chronic indeterminate stage in humans in the spread of the infection. According to the model, it is expected that one infected human infects 21 triatomines, that 100 infected triatomines are necessary to infect one human and 34 to infect a dog, and that each dog infects on average one triatomine per day. Our results may allow quantifying the effect of control measures on infected humans, triatomines and dogs (or other highly infected vertebrate) or on a specific route of transmission, in other scenarios.

Computer analysis of sound recordings from two Anasazi sites in northwestern New Mexico

NASA Astrophysics Data System (ADS)

Loose, Richard

2002-11-01

Sound recordings were made at a natural outdoor amphitheater in Chaco Canyon and in a reconstructed great kiva at Aztec Ruins. Recordings included computer-generated tones and swept sine waves, classical concert flute, Native American flute, conch shell trumpet, and prerecorded music. Recording equipment included analog tape deck, digital minidisk recorder, and direct digital recording to a laptop computer disk. Microphones and geophones were used as transducers. The natural amphitheater lies between the ruins of Pueblo Bonito and Chetro Ketl. It is a semicircular arc in a sandstone cliff measuring 500 ft. wide and 75 ft. high. The radius of the arc was verified with aerial photography, and an acoustic ray trace was generated using cad software. The arc is in an overhanging cliff face and brings distant sounds to a line focus. Along this line, there are unusual acoustic effects at conjugate foci. Time history analysis of recordings from both sites showed that a 60-dB reverb decay lasted from 1.8 to 2.0 s, nearly ideal for public performances of music. Echoes from the amphitheater were perceived to be upshifted in pitch, but this was not seen in FFT analysis. Geophones placed on the floor of the great kiva showed a resonance at 95 Hz.

Low prevalence of methicillin-resistant Staphylococcus aureus nasal carriage in urban and rural community settings in Bolivia and Peru.

PubMed

Bartoloni, Alessandro; Pallecchi, Lucia; Fernandez, Connie; Mantella, Antonia; Riccobono, Eleonora; Magnelli, Donata; Mannini, Dario; Strohmeyer, Marianne; Bartalesi, Filippo; Segundo, Higinio; Monasterio, Joaquin; Rodriguez, Hugo; Cabezas, César; Gotuzzo, Eduardo; Rossolini, Gian Maria

2013-05-01

To investigate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage in rural and urban community settings of Bolivia and Peru. MRSA nasal carriage was investigated in 585 individuals living in rural and urban areas of Bolivia and Peru (one urban area, one small rural village, and two native communities, one of which was highly isolated). MRSA isolates were subjected to molecular analysis for the detection of virulence genes, characterization of the staphylococcal cassette chromosome mec (SCCmec), and genotyping (multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE)). An overall very low prevalence of MRSA nasal carriage was observed (0.5%), with MRSA carriers being detected only in a small rural village of the Bolivian Chaco. The three MRSA isolates showed the characteristics of community-associated MRSA (being susceptible to all non-beta-lactam antibiotics and harboring the SCCmec type IV), were clonally related, and belonged to ST1649. This study provides an insight into the epidemiology of MRSA in community settings of Bolivia and Peru. Reliable, time-saving, and low-cost methods should be implemented to encourage continued surveillance of MRSA dissemination in resource-limited countries. Copyright © 2012 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Tropical ancient DNA reveals relationships of the extinct Bahamian giant tortoise Chelonoidis alburyorum

PubMed Central

Kehlmaier, Christian; Barlow, Axel; Hastings, Alexander K.; Vamberger, Melita; Paijmans, Johanna L. A.; Steadman, David W.; Albury, Nancy A.; Franz, Richard; Hofreiter, Michael

2017-01-01

Ancient DNA of extinct species from the Pleistocene and Holocene has provided valuable evolutionary insights. However, these are largely restricted to mammals and high latitudes because DNA preservation in warm climates is typically poor. In the tropics and subtropics, non-avian reptiles constitute a significant part of the fauna and little is known about the genetics of the many extinct reptiles from tropical islands. We have reconstructed the near-complete mitochondrial genome of an extinct giant tortoise from the Bahamas (Chelonoidis alburyorum) using an approximately 1 000-year-old humerus from a water-filled sinkhole (blue hole) on Great Abaco Island. Phylogenetic and molecular clock analyses place this extinct species as closely related to Galápagos (C. niger complex) and Chaco tortoises (C. chilensis), and provide evidence for repeated overseas dispersal in this tortoise group. The ancestors of extant Chelonoidis species arrived in South America from Africa only after the opening of the Atlantic Ocean and dispersed from there to the Caribbean and the Galápagos Islands. Our results also suggest that the anoxic, thermally buffered environment of blue holes may enhance DNA preservation, and thus are opening a window for better understanding evolution and population history of extinct tropical species, which would likely still exist without human impact. PMID:28077774

The floristic heterogeneity of the Pantanal and the occurrence of species with different adaptive strategies to water stress.

PubMed

Scremin-Dias, E; Lorenz-Lemke, A P; Oliveira, A K M

2011-04-01

The Pantanal is characterised by a diversity of environments with areas ranging from periodic or permanent heavy flooding to areas with low flood levels, and even environments that never flood. Plant species which inhabit the floodplain are distributed in specific niches, with influence of various phytogeographic domains, including the Seasonal Semi-deciduous Forest, Amazon Rainforest, Cerrado and Chaco, as well rocky remnants, with a wide ecological span in their components. In intensely flooded areas, aquatic macrophytes are widely distributed, with their dynamics closely linked to time, depth and extent of flooding. Although the term "Pantanal" suggests a huge swamp-type wetland, water level variation during a seasonal cycle does not directly reach the root system of many plants. The landscape diversity of the Pantanal wetland is molded by the flood pulse, which interferes with the dynamics of plant communities. Therefore, the retraction and expansion of populations or communities is reflected in important ecological characteristics, considering the variety of morphological, anatomical and ecophysiological features of the species, whose phenotype is the result of a particular genotype. The present study discusses peculiar issues in the adaptation of species distributed in the Pantanal biome and underscores the importance of multidisciplinary approaches to obtain conclusive data on adaptive studies.

Globalization’s unexpected impact on soybean production in South America: linkages between preferences for non-genetically modified crops, eco-certifications, and land use

NASA Astrophysics Data System (ADS)

Garrett, Rachael D.; Rueda, Ximena; Lambin, Eric F.

2013-12-01

The land use impacts of globalization and of increasing global food and fuel demand depend on the trade relationships that emerge between consuming and producing countries. In the case of soybean production, increasing trade between South American farmers and consumers in Asia and Europe has facilitated soybean expansion in the Amazon, Chaco, and Cerrado biomes. While these telecouplings have been well documented, there is little understanding of how quality preferences influence trade patterns and supply chains, incentivizing or discouraging particular land use practices. In this study we provide empirical evidence that Brazil’s continued production of non-genetically modified (GM) soybeans has increased its competitive advantage in European countries with preferences against GM foods. Brazil’s strong trade relationship with European consumers has facilitated an upgrading of the soybean supply chain. Upgraded soybean supply chains create new conservation opportunities by allowing farmers to differentiate their products based on environmental quality in order to access premiums in niche markets in Europe. These interactions between GM preferences, trade flows, and supply chain structure help to explain why Brazilian soybean farmers have adopted environmental certification programs on a larger scale than Argentinian, Bolivian, Paraguayan, and Uruguayan soybean producers.

Creating Geoscience Leaders

NASA Astrophysics Data System (ADS)

Buskop, J.; Buskop, W.

2013-12-01

The United Nations Educational, Scientific, and Cultural Organization recognizes 21 World Heritage in the United States, ten of which have astounding geological features: Wrangell St. Elias National Park, Olympic National Park, Mesa Verde National Park, Chaco Canyon, Glacier National Park, Carlsbad National Park, Mammoth Cave, Great Smokey Mountains National Park, Hawaii Volcanoes National Park, and Everglades National Park. Created by a student frustrated with fellow students addicted to smart phones with an extreme lack of interest in the geosciences, one student visited each World Heritage site in the United States and created one e-book chapter per park. Each chapter was created with original photographs, and a geological discovery hunt to encourage teen involvement in preserving remarkable geological sites. Each chapter describes at least one way young adults can get involved with the geosciences, such a cave geology, glaciology, hydrology, and volcanology. The e-book describes one park per chapter, each chapter providing a geological discovery hunt, information on how to get involved with conservation of the parks, geological maps of the parks, parallels between archaeological and geological sites, and how to talk to a ranger. The young author is approaching UNESCO to publish the work as a free e-book to encourage involvement in UNESCO sites and to prove that the geosciences are fun.

Tropical ancient DNA reveals relationships of the extinct Bahamian giant tortoise Chelonoidis alburyorum.

PubMed

Kehlmaier, Christian; Barlow, Axel; Hastings, Alexander K; Vamberger, Melita; Paijmans, Johanna L A; Steadman, David W; Albury, Nancy A; Franz, Richard; Hofreiter, Michael; Fritz, Uwe

2017-01-11

Ancient DNA of extinct species from the Pleistocene and Holocene has provided valuable evolutionary insights. However, these are largely restricted to mammals and high latitudes because DNA preservation in warm climates is typically poor. In the tropics and subtropics, non-avian reptiles constitute a significant part of the fauna and little is known about the genetics of the many extinct reptiles from tropical islands. We have reconstructed the near-complete mitochondrial genome of an extinct giant tortoise from the Bahamas (Chelonoidis alburyorum) using an approximately 1 000-year-old humerus from a water-filled sinkhole (blue hole) on Great Abaco Island. Phylogenetic and molecular clock analyses place this extinct species as closely related to Galápagos (C. niger complex) and Chaco tortoises (C. chilensis), and provide evidence for repeated overseas dispersal in this tortoise group. The ancestors of extant Chelonoidis species arrived in South America from Africa only after the opening of the Atlantic Ocean and dispersed from there to the Caribbean and the Galápagos Islands. Our results also suggest that the anoxic, thermally buffered environment of blue holes may enhance DNA preservation, and thus are opening a window for better understanding evolution and population history of extinct tropical species, which would likely still exist without human impact. © 2017 The Author(s).

Do Wildfires Promote Woody Species Invasion in a Fire-Adapted Ecosystem? Post-fire Resprouting of Native and Non-native Woody Plants in Central Argentina.

PubMed

Herrero, M Lucrecia; Torres, Romina C; Renison, Daniel

2016-02-01

We asked whether prescribed fire could be a useful management tool to reduce invasion by non-native plants in an ecosystem where native plants are supposed to be adapted to fires. Specifically, we compare the post-fire resprouting response of native and non-native woody species in Chaco Serrano forest of central Argentina. The measurements were carried out in five burnt areas where we selected ten native and seven non-native species. Our response variables were (1) post-fire survival, (2) types of resprouts, and (3) the growth of the resprouts. Our main results show that one year after the fire, survivals of native and non-native species were 0.84 and 0.89, respectively, with variances in survival seven times smaller in the native species group. Type of resprout was also less variable in native species, while growth of the resprouts was similar in native and non-native groups. We interpret that in most cases, the burning a forest with mixed native and non-native plants through prescribed fires will not differentially stop the invasion by non-native woody species even in ecosystems which are presumed to be relatively resistant to fires such as our study area.

Anomalous - viscosity current drive

DOEpatents

Stix, Thomas H.; Ono, Masayuki

1988-01-01

An apparatus and method for maintaining a steady-state current in a toroidal magnetically confined plasma. An electric current is generated in an edge region at or near the outermost good magnetic surface of the toroidal plasma. The edge current is generated in a direction parallel to the flow of current in the main plasma and such that its current density is greater than the average density of the main plasma current. The current flow in the edge region is maintained in a direction parallel to the main current for a period of one or two of its characteristic decay times. Current from the edge region will penetrate radially into the plasma and augment the main plasma current through the mechanism of anomalous viscosity. In another aspect of the invention, current flow driven between a cathode and an anode is used to establish a start-up plasma current. The plasma-current channel is magnetically detached from the electrodes, leaving a plasma magnetically insulated from contact with any material obstructions including the cathode and anode.

Generation of region 1 current by magnetospheric pressure gradients

NASA Technical Reports Server (NTRS)

Yang, Y. S.; Spiro, R. W.; Wolf, R. A.

1994-01-01

The Rice Convection Model (RCM) is used to illustrate theoretical possibilities for generating region 1 Birkeland currents by pressure gradients on closed field lines in the Earth's magnetosphere. Inertial effects and viscous forces are neglected. The RCM is applied to idealized cases, to emphasize the basic physical ideas rather than realistic representation of the actual magnetosphere. Ionospheric conductance is taken to be uniform, and the simplest possible representations of the magnetospheric plasma are used. Three basic cases are considered: (1) the case of pure northward Interplanetary Magnetic Field (IMF), with cusp merging assumed to create new closed field lines near the nose of the magnetosphere, following the suggestion by Song and Russell (1992); (2) the case where Dungey-type reconnection occurs at the nose, but magnetosheath plasma somehow enters closed field lines on the dawnside and duskside of the merging region, causing a pressure-driven low-latitude boundary layer; and (3) the case where Dungey-type reconnection occurs at the nose, but region 1 currents flow on sunward drifting plasma sheet field lines. In case 1, currents of region 1 sense are generated by pressure gradients, but those currents do not supply the power for ionospheric convection. Results for case 2 suggest that pressure gradients at the inner edge of the low-latitude boundary layer might generate a large fraction of the region 1 Birkeland currents that drive magnetospheric convection. Results for case 3 indicate that pressure gradients in the plasma sheet could provide part of the region 1 current.

Environmental Assessment for Selected Regions in the Mediterranean Sea

DTIC Science & Technology

1992-01-01

derived from gravity and turbidity flows and include ash layers interbedded with hemipelagic mud. Sedimen- tation rates in these regions are on the order of...CURRENT METERS, ALBORAN I (PISTEK 1984)0& CURRENT METERS, ALBORAN III (PISTEK 1987) A DRIFTING CURRENT METERIS , ALBORAN 11 (PISTEK 1987) 0: CURRENT

Plasma characteristics in the discharge region of a 20 A emission current hollow cathode

NASA Astrophysics Data System (ADS)

Mingming, SUN; Tianping, ZHANG; Xiaodong, WEN; Weilong, GUO; Jiayao, SONG

2018-02-01

Numerical calculation and fluid simulation methods were used to obtain the plasma characteristics in the discharge region of the LIPS-300 ion thruster’s 20 A emission current hollow cathode and to verify the structural design of the emitter. The results of the two methods indicated that the highest plasma density and electron temperature, which improved significantly in the orifice region, were located in the discharge region of the hollow cathode. The magnitude of plasma density was about 1021 m-3 in the emitter and orifice regions, as obtained by numerical calculations, but decreased exponentially in the plume region with the distance from the orifice exit. Meanwhile, compared to the emitter region, the electron temperature and current improved by about 36% in the orifice region. The hollow cathode performance test results were in good agreement with the numerical calculation results, which proved that that the structural design of the emitter and the orifice met the requirements of a 20 A emission current. The numerical calculation method can be used to estimate plasma characteristics in the preliminary design stage of hollow cathodes.

Kinematics of current region fragmentation in semi-inclusive deeply inelastic scattering

DOE PAGES

Boglione, M.; Collins, J.; Gamberg, L.; ...

2017-01-16

Different kinematical regions of semi-inclusive deeply inelastic scattering (SIDIS) processes correspond to different underlying partonic pictures, and it is important to understand the transition between them. We find criteria in semi-inclusive deeply inelastic scattering (SIDIS) for identifying the current fragmentation region — the kinematical region where a factorization picture with fragmentation functions is appropriate, especially for studies of transverse-momentum-dependent (TMD) functions. This region is distinguished from the central (soft) and target fragmentation regions. The basis of our argument is in the errors in approximations used in deriving factorization. As compared with previous work, we show that it is essential tomore » take account of the transverse momentum of the detected hadron, and we find a much more restricted range for genuine current fragmentation. As a result, we show that it is important to develop an extended factorization formulation to treat hadronization in the central region, as well as the current and target fragmentation regions, and to obtain a unified formalism spanning all rapidities for the detected hadron.« less

Hot-carrier-induced current capability degradation and optimization for lateral IGBT on thick SOI substrate

NASA Astrophysics Data System (ADS)

Zhang, Chunwei; Li, Yang; Yue, Wenjing; Fu, Xiaoqian; Li, Zhiming

2018-07-01

In this paper, the hot-carrier-induced current capability degradation of a 600 V lateral insulated gate bipolar transistor (LIGBT) on thick silicon on insulator (SOI) substrate is investigated. Our experiments found that, for the SOI-LIGBT, the worst stress condition is the maximum gate voltage (Vgmax) condition and the current degradation is dominated by the damages in the channel region under the Vgmax stress condition. However, further analyses show that the influence of channel region damages on the collector current degradation increases with the increase of measured collector voltage and is maximum in the current saturation region. Therefore, in our opinion, the hot-carrier-induced current capability degradation of the SOI-LIGBT should be evaluated by the degradation of saturation current under the Vgmax stress condition. In addition, a novel SOI-LIGBT structure with an external p-type region was also proposed, which can alleviate the damage in the channel region by reducing the lateral electric field peak. Our experimental results demonstrate that the proposed structure could optimize the hot-carrier reliability effectively with the other characteristics maintained. He is currently a lecturer at the University of Jinan, Jinan, China. His research interests include power electronics, high voltage devices and the electronics reliability.

Characteristics of ionospheric convection and field-aligned current in the dayside cusp region

NASA Technical Reports Server (NTRS)

Lu, G.; Lyons, L. R.; Reiff, P. H.; Denig, W. F.; Beaujardiere, O. De LA; Kroehl, H. W.; Newell, P. T.; Rich, F. J.; Opgenoorth, H.; Persson, M. A. L.

1995-01-01

The assimilative mapping of ionospheric electrodynamics (AMIE) technique has been used to estimate global distributions of high-latitude ionospheric convection and field-aligned current by combining data obtained nearly simultaneously both from ground and from space. Therefore, unlike the statistical patterns, the 'snapshot' distributions derived by AMIE allow us to examine in more detail the distinctions between field-aligned current systems associated with separate magnetospheric processes, especially in the dayside cusp region. By comparing the field-aligned current and ionospheric convection patterns with the corresponding spectrograms of precipitating particles, the following signatures have been identified: (1) For the three cases studied, which all had an IMF with negative y and z components, the cusp precipitation was encountered by the DMSP satellites in the postnoon sector in the northern hemisphere and in the prenoon sector in the southern hemisphere. The equatorward part of the cusp in both hemispheres is in the sunward flow region and marks the beginning of the flow rotation from sunward to antisunward. (2) The pair of field-aligned currents near local noon, i.e., the cusp/mantle currents, are coincident with the cusp or mantle particle precipitation. In distinction, the field-aligned currents on the dawnside and duskside, i.e., the normal region 1 currents, are usually associated with the plasma sheet particle precipitation. Thus the cusp/mantle currents are generated on open field lines and the region 1 currents mainly on closed field lines. (3) Topologically, the cusp/mantle currents appear as an expansion of the region 1 currents from the dawnside and duskside and they overlap near local noon. When B(sub y) is negative, in the northern hemisphere the downward field-aligned current is located poleward of the upward current; whereas in the southern hemisphere the upward current is located poleward of the downward current. (4) Under the assumption of quasi-steady state reconnection, the location of the separatrix in the ionosphere is estimated and the reconnection velocity is calculated to be between 400 and 550 m/s. The dayside separatrix lies equatorward of the dayside convection throat in the two cases examined.

Four large-scale field-aligned current systmes in the dayside high-latitude region

NASA Technical Reports Server (NTRS)

Ohtani, S.; Potemra, T. A.; Newell, P.T.; Zanetti, L. J.; Iijima, T.; Watanabe, M.; Blomberg, L. G.; Elphinstone, R. D.; Murphree, J. S.; Yamauchi, M.

1995-01-01

A system of four current sheets of large-scale field-aligned currents (FACs) was discovered in the data set of simultaneous Viking and Defense Meteorological Satellire Program-F7 (DMSP-F7) crossing of the dayside high-latitude region. This paper reports four examples of this system that were observed in the prenoon sector. The flow polarities of FACs are upward, downward, upward, and downward, from equatorward to poleward. The lowest-latitude upward current is flowing mostly in the central plasma sheet (CPS) precipitation region, often overlapping with the boundary plasma sheet (BPS) at its poleward edge, andis interpreted as a region 2 current. The pair of downward and upward FACs in the middle of te structure are collocated with structured electron precipitation. The precipitation of high-energy (greater than 1 keV) electrons is more intense in the lower-latitude downward current sheet. The highest-latitude downward flowing current sheet is located in a weak, low-energy particle precipitation region, suggesting that this current is flowing on open field lines. Simulaneous observations in the postnoon local time sector reveal the standard three-sheet structure of FACs, sometimes described as region 2, region 1, and mantle (referred to the midday region O) currents. A high correlation was found between the occurrence of the four FAC sheet structure and negative interplanetary magnetic field (IMF) B(sub Y). We discuss the FAC structurein terms of three types of convection cells: the merging, viscous, andlobe cells. During strongly negative IMF B(sub Y), two convection reversals exist in the prenoon sector; one is inside the viscous cell, and the other is between the viscous cell and the lobe cell. This structure of convection flow is supported by the Viking electric field and auroral UV image data. Based on the convection pattern, the four FAC sheet structure is interpreted as the latitude overlap of midday and morning FAC systems. We suggest that the for-current sheet structure is common in a certain prenoon localtime sector during strongly negative IMF B(sub Y).

Taxonomic analysis of Paraguayan samples of Homonota fasciata Duméril & Bibron (1836) with the revalidation of Homonota horrida Burmeister (1861) (Reptilia: Squamata: Phyllodactylidae) and the description of a new species.

PubMed

Cacciali, Pier; Morando, Mariana; Medina, Cintia D; Köhler, Gunther; Motte, Martha; Avila, Luciano J

2017-01-01

Homonota is a Neotropical genus of nocturnal lizards characterized by the following combination of characters: absence of femoral pores, infradigital lamellae not dilated, claws without sheath, inferior lamellae laterally not denticulate, and presence of a ceratobranchial groove. Currently the genus is composed of 10 species assembled in three groups: two groups with four species, and the fasciata group with only two species. Here, we analyzed genetic and morphologic data of samples of Homonota fasciata from Paraguay; according to Maximum Likelihood and Bayesian inference analyses, the Paraguay population represents an undescribed species. Additionally, morphological analysis of the holotype of H. fasciata (MNHN 6756) shows that it is morphologically different from the banded, large-scaled Homonota commonly referred to as " H. fasciata ". Given the inconsistency between morphological characters of the name-bearing type of H. fasciata and the species commonly referred to as H. fasciata , we consider them as different taxa. Thus, H. fasciata is a species inquirenda which needs further studies, and we resurrect the name H. horrida for the banded, large-scaled Homonota . The undescribed species from Paraguay is similar to H. horrida , but can be differentiated by the high position of the auditory meatus relative to the mouth commissure (vs. low position in H. horrida ); and less developed tubercles on the sides of the head, including a narrow area between the orbit and the auditory meatus covered with small granular scales with or without few tubercles (vs. several big tubercles on the sides of the head even in the area between the orbit and the auditory meatus). The new species is distributed in the Dry Chaco in South America. With the formal description of this species, the actual diversity of the genus Homonota is increased to 12 species. Furthermore, we infer phylogenetic relationships for 11 of the 12 described species of the genus, based on 11 molecular markers (two mitochondrial and nine nuclear genes), with concatenated and species tree approaches.

Taxonomic analysis of Paraguayan samples of Homonota fasciata Duméril & Bibron (1836) with the revalidation of Homonota horrida Burmeister (1861) (Reptilia: Squamata: Phyllodactylidae) and the description of a new species

PubMed Central

Morando, Mariana; Medina, Cintia D.; Köhler, Gunther; Motte, Martha; Avila, Luciano J.

2017-01-01

Homonota is a Neotropical genus of nocturnal lizards characterized by the following combination of characters: absence of femoral pores, infradigital lamellae not dilated, claws without sheath, inferior lamellae laterally not denticulate, and presence of a ceratobranchial groove. Currently the genus is composed of 10 species assembled in three groups: two groups with four species, and the fasciata group with only two species. Here, we analyzed genetic and morphologic data of samples of Homonota fasciata from Paraguay; according to Maximum Likelihood and Bayesian inference analyses, the Paraguay population represents an undescribed species. Additionally, morphological analysis of the holotype of H. fasciata (MNHN 6756) shows that it is morphologically different from the banded, large-scaled Homonota commonly referred to as “H. fasciata”. Given the inconsistency between morphological characters of the name-bearing type of H. fasciata and the species commonly referred to as H. fasciata, we consider them as different taxa. Thus, H. fasciata is a species inquirenda which needs further studies, and we resurrect the name H. horrida for the banded, large-scaled Homonota. The undescribed species from Paraguay is similar to H. horrida, but can be differentiated by the high position of the auditory meatus relative to the mouth commissure (vs. low position in H. horrida); and less developed tubercles on the sides of the head, including a narrow area between the orbit and the auditory meatus covered with small granular scales with or without few tubercles (vs. several big tubercles on the sides of the head even in the area between the orbit and the auditory meatus). The new species is distributed in the Dry Chaco in South America. With the formal description of this species, the actual diversity of the genus Homonota is increased to 12 species. Furthermore, we infer phylogenetic relationships for 11 of the 12 described species of the genus, based on 11 molecular markers (two mitochondrial and nine nuclear genes), with concatenated and species tree approaches. PMID:28828231

Relationships between field-aligned currents, electric fields, and particle precipitation as observed by Dynamics Explorer-2

NASA Technical Reports Server (NTRS)

Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

1984-01-01

The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.

Relationships between field-aligned currents, electric fields and particle precipitation as observed by dynamics Explorer-2

NASA Technical Reports Server (NTRS)

Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

1983-01-01

The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.

3D Magnetic Field Analysis of a Turbine Generator Stator Core-end Region

NASA Astrophysics Data System (ADS)

Wakui, Shinichi; Takahashi, Kazuhiko; Ide, Kazumasa; Takahashi, Miyoshi; Watanabe, Takashi

In this paper we calculated magnetic flux density and eddy current distributions of a 71MVA turbine generator stator core-end using three-dimensional numerical magnetic field analysis. Subsequently, the magnetic flux densities and eddy current densities in the stator core-end region on the no-load and three-phase short circuit conditions obtained by the analysis have good agreements with the measurements. Furthermore, the differences of eddy current and eddy current loss in the stator core-end region for various load conditions are shown numerically. As a result, the facing had an effect that decrease the eddy current loss of the end plate about 84%.

Energization of Ions in near-Earth current sheet disruptions

NASA Technical Reports Server (NTRS)

Taktakishvili, A.; Lopez, R. E.; Goodrich, C. C.

1995-01-01

In this study we examine observations made by AMPTE/CCE of energetic ion bursts during seven substorm periods when the satellite was located near the neutral sheet, and CCE observed the disruption cross-tail current in situ. We compare ion observations to analytic calculations of particle acceleration. We find that the acceleration region size, which we assume to be essentially the current disruption region, to be on the order of 1 R(sub E). Events exhibiting weak acceleration had either relatively small acceleration regions (apparently associated with pseudobreakup activity on the ground) or relatively small changes in the local magnetic field (suggesting that the magnitude of the local current disruption region was limited). These results add additional support for the view that the particle bursts observed during turbulent current sheet disruptions are due to inductive acceleration of ions.

Swarm observations of field-aligned currents associated with pulsating auroral patches

NASA Astrophysics Data System (ADS)

Gillies, D. M.; Knudsen, D.; Spanswick, E.; Donovan, E.; Burchill, J.; Patrick, M.

2015-11-01

We have performed a superposed epoch study of in situ field-aligned currents located near the edges of regions of pulsating aurora observed simultaneously using ground-based optical data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imager (ASI) network and magnetometers on board the Swarm satellites. A total of nine traversals of Swarm over regions of pulsating aurora identified using THEMIS ASI were studied. We determined that in the cases where a clear boundary can be identified, strong downward currents are seen just poleward and equatorward of the pulsating patches. A downward current in the range of ~1-6 μA/m2 can be seen just poleward of the boundary. A weaker upward current of ~1-3 μA/m2 is observed throughout the interior of the patch. These observations indicate that currents carried by precipitating electrons within patches could close through horizontal currents and be returned at the edges, in agreement with Oguti and Hayashi (1984) and Hosokawa et al. (2010b). In addition to confirming these earlier results and adding to their statistical significance, the contribution of this study is to quantify the upward and downward current magnitudes, in some cases using two satellites traversing the same pulsating regions. Finally, we compare Swarm's two-satellite field-aligned current product to the single-satellite results and determine that the data product can be compromised in regions of pulsating aurora, a phenomenon that occurs over widespread regions and tends to persist for long periods of time. These results underscore the importance of electrical coupling between the ionosphere and magnetosphere in regions of patchy pulsating aurora.

Gas stream analysis using voltage-current time differential operation of electrochemical sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woo, Leta Yar-Li; Glass, Robert Scott; Fitzpatrick, Joseph Jay

A method for analysis of a gas stream. The method includes identifying an affected region of an affected waveform signal corresponding to at least one characteristic of the gas stream. The method also includes calculating a voltage-current time differential between the affected region of the affected waveform signal and a corresponding region of an original waveform signal. The affected region and the corresponding region of the waveform signals have a sensitivity specific to the at least one characteristic of the gas stream. The method also includes generating a value for the at least one characteristic of the gas stream basedmore » on the calculated voltage-current time differential.« less

ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and its Implication to Ionospheric Closure Currents

NASA Technical Reports Server (NTRS)

Le, G.

2008-01-01

A major unsolved question in the physics of ionosphere-magnetosphere coupling is how field-aligned currents (FACs) close. In order to maintain the divergence free condition, overall downward FACs (carried mainly by upward electrons) must eventually balance the overall upward FACs associated with the precipitating electrons through ionospheric Pedersen currents. Although much of the current closure may take place via local Pedersen currents flowing between Region 1 (R1) and Region 2 (R2) FACs, there is a generally an imbalance, i.e., more currents in R1 than in R2, in total currents between them. The net currents may be closed within R1 via cross-polar cap Pedersen currents. In this study, we use the magnetic field observations from Space Technology 5 mission to quantify the imbalance of R1 and R2 currents. We will determine the net R1-R2 currents under various solar wind conditions and discuss the implication of such imbalance to the ionospheric closure currents.

The effects of magnetic field in plume region on the performance of multi-cusped field thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Peng, E-mail: hupengemail@126.com; Liu, Hui, E-mail: thruster@126.com; Yu, Daren

2015-10-15

The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field in the plume region were investigated. Five magnetic field shielding rings were separately mounted near the exit of discharge channel to decrease the strength of magnetic field in the plume region in different levels, while the magnetic field in the upstream was well maintained. The test results show that the electron current increases with the decrease of magnetic field strength in the plume region, which gives rise to higher propellant utilization and lower current utilization. On the other hand, the stronger magnetic field in the plume regionmore » improves the performance at low voltages (high current mode) while lower magnetic field improves the performance at high voltages (low current mode). This work can provide some optimal design ideas of the magnetic strength in the plume region to improve the performance of thruster.« less

A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources

NASA Astrophysics Data System (ADS)

Kirk, Ansgar Thomas; Kobelt, Tim; Spehlbrink, Hauke; Zimmermann, Stefan

2018-05-01

Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with high ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region. [Figure not available: see fulltext.

A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources.

PubMed

Kirk, Ansgar Thomas; Kobelt, Tim; Spehlbrink, Hauke; Zimmermann, Stefan

2018-05-08

Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with high ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region. Graphical Abstract ᅟ.

Ion current in a magnetic neutral region - Generation of an incipient magnetopause

NASA Technical Reports Server (NTRS)

Whipple, E. C.; Silevitch, M. B.

1982-01-01

The current contributed by ions trapped in the vicinity of a magnetic X line is calculated. The three dimensional configuration of the neutral region is found to be critical in determining the current in that the escape mechanism and trapping times depend on the three-dimensional aspects. A trapping criterion is defined. In the neutral region the ions can gain substantial kinetic energy, and the current will change the X line configuration in such a way that there will be a positive feedback effect, rapidly forming an extended magnetopauselike structure for even very small incident plasma densities.

Quench dynamics of the Josephson current in a topological Josephson junction

NASA Astrophysics Data System (ADS)

Sun, Dihao; Liu, Jie

2018-01-01

The 4 π -periodic Josephson effect is a distinguishing feature of a topological Josephson junction. However, stringent conditions make it hard to observe in experiments. In this work, we study the transient transport properties in a topological Josephson junction numerically. We show that the 4 π Josephson current can be sustained under nonequilibrium conditions. The properties of the Josephson current are analyzed for different conditions and three main regimes are identified. First, when both the superconducting wires of the Josephson junction lie in the topologically nontrivial region, a 4 π Josephson current can appear upon suddenly applying a dc voltage. Second, when one superconducting wire lies in the trivial region, while the other wire lies in the nontrivial region, the Josephson current is 2 π periodic but the component of the higher-order Josephson current increases. Third, when both wires lie in the trivial region, a stable 2 π Josephson current is observed. Most importantly, the fractional Josephson effect is fragile in the presence of disorder. Hence experiments should be designed carefully to eliminate the effect of disorder. These results could be helpful to optimize fine-tuning of the experimental parameters to observe the 4 π -periodic Josephson current in a topological Josephson junction.

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. III - NOAA active region 6233 (1990 August)

NASA Technical Reports Server (NTRS)

De La Beaujardiere, J.-F.; Canfield, Richard C.; Leka, K. D.

1993-01-01

We investigate the spatial relationship between vertical electric currents and flare phenomena in NOAA Active Region 6233, which was observed 1990, August 28-31 at Mees Solar Observatory. The two flares studied are the 1N/M1.8 flare on August 28, 22:30 UT and the 1N/M1.6 flare on August 29, 20:35 UT. Using Stokes polarimetry we make magnetograms of the region and compute the vertical current density. Using H-alpha imaging spectroscopy we identify sites of intense nonthermal electron precipitation or of high coronal pressure. The precipitation in these flares is barely strong enough to be detectable. We find that both precipitation and high pressure tend to occur near vertical currents, but that neither phenomenon is cospatial with current maxima. In contrast with the conclusion of other authors, we argue that these observations do not support a current-interruption model for flares, unless the relevant currents are primarily horizontal. The magnetic morphology and temporal evolution of these flares suggest that an erupting filament model may be relevant, but this model does not explicitly predict the relationship between precipitation, high pressure, and vertical currents.

Care and Cure: Health Curriculum for Current Needs. Regional Spotlight. Southern Regional Education Board, Vol. 3, No. 3, January/February 1974.

ERIC Educational Resources Information Center

Southern Regional Education Board, Atlanta, GA.

How will the health professionals in the Southern Regional Education Board (SREB) region handle increased demands for health care? This document describes one course of action illustrated by current efforts to increase the supply of health personnel by a shortened curriculum in professional schools. Usually these programs offer only about 3 months…

Explorations of electric current system in solar active regions. I - Empirical inferences of the current flows

NASA Technical Reports Server (NTRS)

Ding, Y. J.; Hong, Q. F.; Hagyard, M. J.; Deloach, A. C.; Liu, X. P.

1987-01-01

Techniques to identify sources of electric current systems and their channels of flow in solar active regions are explored. Measured photospheric vector magnetic fields together with high-resolution white-light and H-alpha filtergrams provide the data base to derive the current systems in the photosphere and chromosphere. As an example, the techniques are then applied to infer current systems in AR 2372 in early April 1980.

Connections Among the Spatial and Temporal Structures in Tidal Currents, Internal Bores, and Surficial Sediment Distributions Over the Shelf off Palos Verdes, California

USGS Publications Warehouse

Noble, Marlene A.; Rosenberger, Kurt J.; Xu, Jingping; Signell, Richard P.; Steele, Alex

2009-01-01

The topography of the Continental Shelf in the central portion of the Southern California Bight has rapid variations over relatively small spatial scales. The width of the shelf off the Palos Verdes peninsula, just northwest of Los Angeles, California, is only 1 to 3 km. About 7 km southeast of the peninsula, the shelf within San Pedro Bay widens to about 20 km. In 2000, the Los Angeles County Sanitation District began deploying a dense array of moorings in this complex region of the central Southern California Bight to monitor local circulation patterns. Moorings were deployed at 13 sites on the Palos Verdes shelf and within the northwestern portion of San Pedro Bay. At each site, a mooring supported a string of thermistors and an adjacent bottom platform housed an Acoustic Doppler Current Profiler. These instruments collected vertical profiles of current and temperature data continuously for one to two years. The variable bathymetry in the region causes rapid changes in the amplitudes and spatial structures of barotropic tidal currents, internal tidal currents, and in the associated nonlinear baroclinic currents that occur at approximate tidal frequencies. The largest barotropic tidal constituent is M2, the principal semidiurnal tide. The amplitude of this tidal current changes over fairly short along-shelf length scales. Tidal-current amplitudes are largest in the transition region between the two shelves; they increase from about 5 cm/s over the northern San Pedro shelf to nearly 10 cm/s on the southern portion of the Palos Verdes Shelf. Tidal-current amplitudes are then reduced to less than 2 cm/s over the very narrow section of the northern Palos Verdes shelf that lies just 6 km upcoast of the southern sites. Models suggest that the amplitude of the barotropic M2 tidal currents, which propagate toward the northwest primarily as a Kelvin wave, is adjusting to the short topographic length scales in the region. Semidiurnal sea-level oscillations are, as expected, independent of these topographic variations; they have a uniform amplitude and phase structure over the entire region. Because the cross-shelf angle of the seabed over most of the Palos Verdes shelf is 1 to 3 degrees, which is critical for the local generation and/or enhancement of nonlinear characteristics in semidiurnal internal tides, some internal tidal-current events have strong asymmetric current oscillations that are enhanced near the seabed. Near-bottom currents in these events are directed primarily offshore with amplitudes that exceed 30 cm/s. The spatial patterns in these energetic near-bottom currents have fairly short-length scales. They are largest over the inner shelf and in the transition region between the Palos Verdes and San Pedro shelves. This spatial pattern is similar to that found in the barotropic tidal currents. Because these baroclinic currents have an approximate tidal frequency, an asymmetric vertical structure, and a somewhat stable phase, they can produce a non-zero depth-mean flow for periods of a few months. These baroclinic currents can interact with the barotropic tidal current and cause an apparent increase (or decrease) in the estimated barotropic tidal-current amplitude. The apparent amplitude of the barotropic tidal current may change by 30 to 80 percent or more in a current record that is less than three months long. The currents and surficial sediments in this region are in dynamic equilibrium in that the spatial patterns in bottom stresses generated by near-bed currents from surface tides, internal tides, and internal bores partly control the spatial patterns in the local sediments. Coarser sediments are found in the regions with enhanced bottom stresses (that is, over the inner shelf and in the region between the Palos Verdes and San Pedro shelves). Finer sediments are found over the northwestern portion of the Palos Verdes shelf, where near-bottom currents are relatively weak. The nonlinear asymmetries in the i

CURRENT SHEET THINNING AND ENTROPY CONSTRAINTS DURING THE SUBSTORM GROWTH PHASE

NASA Astrophysics Data System (ADS)

Otto, A.; Hall, F., IV

2009-12-01

A typical property during the growth phase of geomagnetic substorms is the thinning of the near-Earth current sheet, most pronounced in the region between 6 and 15 R_E. We propose that the cause for the current sheet thinning is convection from the midnight tail region to the dayside to replenish magnetospheric magnetic flux which is eroded at the dayside as a result of dayside reconnection. Adiabatic convection from the near-Earth tail region toward the dayside must conserve the entropy on magnetic field lines. This constraint prohibits a source of the magnetic flux from a region further out in the magnetotail. Thus the near-Earth tail region is increasingly depleted of magnetic flux (the Erickson and Wolf [1980] problem) with entropy matching that of flux tubes that are eroded on the dayside. It is proposed that the magnetic flux depletion in the near-Earth tail forces the formation of thin current layers. The process is documented by three-dimensional MHD simulations. It is shown that the simulations yield a time scale, location, and other general characteristics of the current sheet evolution during the substorm growth phase.

The influence of surface waves on water circulation in a mid-Atlantic continental shelf region

NASA Technical Reports Server (NTRS)

Whitlock, C. H.; Talay, T. A.

1974-01-01

The importance of wave-induced currents in different weather conditions and water depths (18.3 m and 36.6 m) is assessed in a mid-Atlantic continental-shelf region. A review of general circulation conditions is conducted. Factors which perturb the general circulation are examined using analytic techniques and limited experimental data. Actual wind and wave statistics for the region are examined. Relative magnitudes of the various currents are compared on a frequency of annual occurrence basis. Results indicated that wave-induced currents are often the same order of magnitude as other currents in the region and become more important at higher wind and wave conditions. Wind-wave and ocean-swell characteristics are among those parameters which must be monitored for the analytical computation of continental-shelf circulation.

Electron Currents and Heating in the Ion Diffusion Region of Asymmetric Reconnection

NASA Technical Reports Server (NTRS)

Graham, D. B.; Khotyaintsev, Yu. V.; Norgren, C.; Vaivads, A.; Andre, M.; Lindqvist, P. A.; Marklund, G. T.; Ergun, R. E.; Paterson, W. R.; Gershman, D. J.;

Oxygen concentration sensor for an internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakajima, T.; Okada, Y.; Mieno, T.

1988-09-29

This patent describes an oxygen concentration sensor, comprising: an oxygen ion conductive solid electrolyte member forming a gas diffusion restricted region into which a measuring gas is introduced; a pair of electrodes sandwiching the solid electrolyte member; pump current supply means applying a pump voltage to the pair of electrodes through a current detection element to generate a pump current; and a heater element connected to the solid electrolyte member for heating the solid electrolyte member for heating the solid electrolyte member when a heater current is supplied from a heater current source; wherein the oxygen concentration sensor detects anmore » oxygen concentration in the measuring gas in terms of a current value of the pump current supplied through the current detection element and controls oxygen concentration in the gas diffusion restricted region by conducting oxygen ions through the solid electrolyte member in accordance to the flow of the pump current; and wherein the current detection element is connected to the electrode of the pair of electrodes facing the gas diffusion restricted region for insuring that the current value is representative of the pump current and possible leakage current from the heater current.« less

A quantity characterizing variation of observed magnetic twist in solar active regions

NASA Astrophysics Data System (ADS)

Gao, Yu

2018-03-01

An alternative parameter RJz is introduced as the ratio of one of two kinds of opposite-sign current to the total current and is used to investigate the relationship between this quantity and the hemispheric helicity sign rule (HSR) that has been established by a series of previous statistical studies. The classification of current in each hemisphere obeys the following rule: if the product of the current and the corresponding longitudinal field component contributes a consistent sign with respect to the HSR, it is called “HSR-compliant” current, otherwise it is called “HSR-noncompliant” current. Firstly, consistency between the butterfly diagram of RJz and current helicity was obtained in a statistical study. Active regions with RJz smaller than 0.5 tend to obey the HSR whereas those with RJz greater than 0.5 tend to disobey it. The “HSR-compliant” current systems have a 60% probability of realization compared to 40% for “HSR-noncompliant” current systems. Overall, the HSR is violated for active regions in which the “HSR-noncompliant” current is greater than the “HSR-compliant” current. Secondly, the parameter RJz was subsequently used to study the evolution of current systems in the case analyses of flare-productive active regions NOAA AR 11158 and AR 11283. It is found that there is a “RJz -quasi-stationary” phase that is relatively flare quiescent and “RJz -dynamic” phase that is characterized by the occurrence of large flares.

The Footprint of Continental-Scale Ocean Currents on the Biogeography of Seaweeds

PubMed Central

Wernberg, Thomas; Thomsen, Mads S.; Connell, Sean D.; Russell, Bayden D.; Waters, Jonathan M.; Zuccarello, Giuseppe C.; Kraft, Gerald T.; Sanderson, Craig; West, John A.; Gurgel, Carlos F. D.

2013-01-01

Explaining spatial patterns of biological organisation remains a central challenge for biogeographic studies. In marine systems, large-scale ocean currents can modify broad-scale biological patterns by simultaneously connecting environmental (e.g. temperature, salinity and nutrients) and biological (e.g. amounts and types of dispersed propagules) properties of adjacent and distant regions. For example, steep environmental gradients and highly variable, disrupted flow should lead to heterogeneity in regional communities and high species turnover. In this study, we investigated the possible imprint of the Leeuwin (LC) and East Australia (EAC) Currents on seaweed communities across ~7,000 km of coastline in temperate Australia. These currents flow poleward along the west and east coasts of Australia, respectively, but have markedly different characteristics. We tested the hypothesis that, regional seaweed communities show serial change in the direction of current flow and that, because the LC is characterised by a weaker temperature gradient and more un-interrupted along-shore flow compared to the EAC, then coasts influenced by the LC have less variable seaweed communities and lower species turnover across regions than the EAC. This hypothesis was supported. We suggest that this pattern is likely caused by a combination of seaweed temperature tolerances and current-driven dispersal. In conclusion, our findings support the idea that the characteristics of continental-scale currents can influence regional community organisation, and that the coupling of ocean currents and marine biological structure is a general feature that transcends taxa and spatial scales. PMID:24260352

Non-neutralized Electric Currents in Solar Active Regions and Flare Productivity

NASA Astrophysics Data System (ADS)

Kontogiannis, Ioannis; Georgoulis, Manolis K.; Park, Sung-Hong; Guerra, Jordan A.

2017-11-01

We explore the association of non-neutralized currents with solar flare occurrence in a sizable sample of observations, aiming to show the potential of such currents in solar flare prediction. We used the high-quality vector magnetograms that are regularly produced by the Helioseismic Magnetic Imager, and more specifically, the Space weather HMI Active Region Patches (SHARP). Through a newly established method that incorporates detailed error analysis, we calculated the non-neutralized currents contained in active regions (AR). Two predictors were produced, namely the total and the maximum unsigned non-neutralized current. Both were tested in AR time-series and a representative sample of point-in-time observations during the interval 2012 - 2016. The average values of non-neutralized currents in flaring active regions are higher by more than an order of magnitude than in non-flaring regions and correlate very well with the corresponding flare index. The temporal evolution of these parameters appears to be connected to physical processes, such as flux emergence and/or magnetic polarity inversion line formation, that are associated with increased solar flare activity. Using Bayesian inference of flaring probabilities, we show that the total unsigned non-neutralized current significantly outperforms the total unsigned magnetic flux and other well-established current-related predictors. It therefore shows good prospects for inclusion in an operational flare-forecasting service. We plan to use the new predictor in the framework of the FLARECAST project along with other highly performing predictors.

Paralleling power MOSFETs in their active region: Extended range of passively forced current sharing

NASA Technical Reports Server (NTRS)

Niedra, Janis M.

1989-01-01

A simple passive circuit that improves current balance in parallelled power MOSFETs that are not precisely matched and that are operated in their active region from a common gate drive are exhibited. A nonlinear circuit consisting of diodes and resistors generates the differential gate potential required to correct for unbalance while maintaining low losses over a range of current. Also application of a thin tape wound magnetic core to effect dynamic current balance is reviewed, and a simple theory is presented showing that for operation in the active region the branch currents tend to revert to their normal unbalanced values even if the core is not driven into saturation. Results of several comparative experiments are given.

Timing of wet episodes in Atacama Desert over the last 15 ka. The Groundwater Discharge Deposits (GWD) from Domeyko Range at 25°S.

NASA Astrophysics Data System (ADS)

Sáez, Alberto; Godfrey, Linda V.; Herrera, Christian; Chong, Guillermo; Pueyo, Juan J.

2016-08-01

A chronologically robust reconstruction of timing and dynamics of millennial time scale wet episodes encompassing the entire Atacama Desert during the last 15 ka has been constructed. To accomplish this, a new composite paleoclimatic record from Groundwater Discharge Deposits (GWD) in the Sierra de Varas (Domeyko Range, southern Atacama in Chile at 25°S) has been compiled and compared with other published paleohydrologic records from the Atacama region. In Sierra de Varas (SV), three millennial timescale wet climate phases have been characterized: around 14.5 ka cal BP, 12.2-9.8 ka cal BP, and 4.7 ka cal BP to the present day. These wet phases are interpreted from intervals of GWD facies formed during periods when the springs were active. GWD facies include: (1) black organic peat, rooted mudstones and sandstones formed in local wetland environments, and (2) gypsum-carbonate rich layers formed by interstitial growth. GWD intervals alternate with gravelly alluvial material deposited during arid phases. A trend towards less humid conditions during the Late Holocene wet episode characterizes GWD sedimentary series in Sierra the Varas, suggesting the onset of a dry episode over the last few centuries. Around 0.7 ka BP a very short wet episode is recorded in the central part of the desert suggesting this was the time of maximum humidity for the entire late Holocene wet period. A brief arid phase occurred between 1.5 and 2.0 ka BP indicated by the absence of GWD in the Domeyko Range. The paleoclimatic reconstruction encompassing the entire Atacama region shows that both the intensity and occurrence of wetter conditions were governed mainly by the distance to the source of moisture, and secondarily by the elevation of the sites. In the northern Atacama (16-20°S), four wet phases fed by N-NE summer monsoon precipitations have been proposed: Tauca phase (18-14 ka cal BP) and Coipasa phase (13-10 ka cal BP) during the Late Glacial, followed by Early Holocene and Late Holocene phases. In contrast, southern Atacama records (23-28°S) display only three pluvial periods which result from SE summer monsoon precipitation and outbreaks from the Westerlies during wintertime. The Early Holocene in the southern Atacama was a period of aridity, generating important landscape differences to those in the Northern Atacama where conditions were wetter. The core of Atacama (20-23°S) is the overall driest part of the desert because it is located in the distal limits of both N-NE and SE sources of moisture, the Amazon Basin and Gran Chaco areas, respectively.

Contribution of Field Strength Gradients to the Net Vertical Current of Active Regions

NASA Astrophysics Data System (ADS)

Vemareddy, P.

2017-12-01

We examined the contribution of field strength gradients for the degree of net vertical current (NVC) neutralization in active regions (ARs). We used photospheric vector magnetic field observations of AR 11158 obtained by Helioseismic and Magnetic Imager on board SDO and Hinode. The vertical component of the electric current is decomposed into twist and shear terms. The NVC exhibits systematic evolution owing to the presence of the sheared polarity inversion line between rotating and shearing magnetic regions. We found that the sign of shear current distribution is opposite in dominant pixels (60%–65%) to that of twist current distribution, and its time profile bears no systematic trend. This result indicates that the gradient of magnetic field strength contributes to an opposite signed, though smaller in magnitude, current to that contributed by the magnetic field direction in the vertical component of the current. Consequently, the net value of the shear current is negative in both polarity regions, which when added to the net twist current reduces the direct current value in the north (B z > 0) polarity, resulting in a higher degree of NVC neutralization. We conjecture that the observed opposite signs of shear and twist currents are an indication, according to Parker, that the direct volume currents of flux tubes are canceled by their return currents, which are contributed by field strength gradients. Furthermore, with the increase of spatial resolution, we found higher values of twist, shear current distributions. However, the resolution effect is more useful in resolving the field strength gradients, and therefore suggests more contribution from shear current for the degree of NVC neutralization.

[Centralized immunization schedules and regional equity of access: an audit among Apulian healthcare workers].

PubMed

Tafuri, S; Martinelli, D; Caputi, G; Fortunato, F; Germinario, C; Prato, R

2009-01-01

The reform of the Vth Title of the Italian Constitution has given the Regions autonomous power over planning of their immunization programme and immunization calendar. This amendment has federalized Italy's vaccination system and, is justified by epidemiological evidence however casts doubt on its provision of equal rights to health care. The objective of this current study is to gain insight into the opinion of vaccine services officers in the Apulia region on federal immunization and the regional immunization programme. Research was conducted using an anonymous standardized questionnaire to which 302 vaccines services staff responded. 67.4% of respondents believe that the current federal vaccination programme should be maintained, whilst 20.2% believe that the current system should be eradicated and 12.4% believe it should be phased out gradually. The current apulian vaccination calendar provides free and active immunizations for all newborns for the pneumococcal, meningitis C, chickenpox and hepatitis A vaccines. The interviewees believe that the vaccinations provided in the regional immunization programme are very important (average importance out of 10 = 6.1/7). The positive response to the regional vaccination plan given by the health officers explains, at least in part, the conservative attitude tewards federal vaccination plans. It cannot be excluded that sacrificing regional autonomy over vaccination programmes might be considered by the vaccination officers as being responsible for the abandonment of the Region's long established immunization practices. The success of these practices is evident in the case of the Region's Hepatitis A immunization programme where the active provision of this vaccine has drastically reduced the endemicity of the illness in Apulia. These experiences of good practice should be adequately considered in before opting to phase out the current immunisation programme.

Kinetic Studies of Thin Current Sheets at Magnetosheath Jets

NASA Astrophysics Data System (ADS)

Eriksson, E.; Vaivads, A.; Khotyaintsev, Y. V.; Graham, D. B.; Yordanova, E.; Hietala, H.; Markidis, S.; Giles, B. L.; Andre, M.; Russell, C. T.; Le Contel, O.; Burch, J. L.

2017-12-01

In near-Earth space one of the most turbulent plasma environments is the magnetosheath (MSH) downstream of the quasi-parallel shock. The particle acceleration and plasma thermalization processes there are still not fully understood. Regions of strong localized currents are believed to play a key role in those processes. The Magnetospheric Multiscale (MMS) mission has sufficiently high cadence to study these processes in detail. We present details of studies of two different events that contain strong current regions inside the MSH downstream of the quasi-parallel shock. In both cases the shape of the current region is in the form of a sheet, however they show internal 3D structure on the scale of the spacecraft separation (15 and 20 km, respectively). Both current sheets have a normal magnetic field component different from zero indicating that the regions at the different sides of the current sheets are magnetically connected. Both current sheets are boundaries between two different plasma regions. Furthermore, both current sheets are observed at MSH jets. These jets are characterized by localized dynamic pressure being larger than the solar wind dynamic pressure. One current sheet does not seem to be reconnecting while the other shows reconnection signatures. Inside the non-reconnecting current sheet we observe locally accelerated electron beams along the magnetic field. At energies above the beam energy we observe a loss cone consistent with part of the hot MSH-like electrons escaping into the colder solar wind-like plasma. This suggests that the acceleration process within this current sheet is similar to the one that occurs at the bow shock, where electron beams and loss cones are also observed. Therefore, we conclude that electron beams observed in the MSH do not have to originate from the bow shock, but can also be generated locally inside the MSH. The reconnecting current sheet also shows signs of thermalization and electron acceleration processes that are discussed in detail.

A High-resolution Model of Field-aligned Currents Through Empirical Orthogonal Functions Analysis (MFACE)

NASA Technical Reports Server (NTRS)

He, Maosheng; Vogt, Joachim; Luehr, Hermann; Sorbalo, Eugen; Blagau, Adrian; Le, Guan; Lu, Gang

2012-01-01

Ten years of CHAMP magnetic field measurements are integrated into MFACE, a model of field-aligned currents (FACs) using empirical orthogonal functions (EOFs). EOF1 gives the basic Region-1/Region-2 pattern varying mainly with the interplanetary magnetic field Bz component. EOF2 captures separately the cusp current signature and By-related variability. Compared to existing models, MFACE yields significantly better spatial resolution, reproduces typically observed FAC thickness and intensity, improves on the magnetic local time (MLT) distribution, and gives the seasonal dependence of FAC latitudes and the NBZ current signature. MFACE further reveals systematic dependences on By, including 1) Region-1/Region-2 topology modifications around noon; 2) imbalance between upward and downward maximum current density; 3) MLT location of the Harang discontinuity. Furthermore, our procedure allows quantifying response times of FACs to solar wind driving at the bow shock nose: we obtain 20 minutes and 35-40 minutes lags for the FAC density and latitude, respectively.

Musculoskeletal disorder risk during automotive assembly: current vs. seated

PubMed Central

Ferguson, Sue A.; Marras, William S.; Allread, W. Gary; Knapik, Gregory G.; Splittstoesser, Riley E.

2013-01-01

Musculoskeletal disorder risk was assessed during automotive assembly processes. The risk associated with current assembly processes was compared to using a cantilever chair intervention. Spine loads and normalized shoulder muscle activity were evaluated during assembly in eight regions of the vehicle. Eight interior cabin regions of the vehicle were classified by reach distance, height from vehicle floor and front to back. The cantilever chair intervention tool was most effective in the far reach regions regardless of the height. In the front far reach regions both spine loads and normalized shoulder muscle activity levels were reduced. In the middle and close reach regions spine loads were reduced, however, shoulder muscle activity was not, thus an additional intervention would be necessary to reduce shoulder risk. In the back far reach region, spine loads were not significantly different between the current and cantilever chair conditions. Thus, the effectiveness of the cantilever chair was dependent on the region of the vehicle. PMID:22036450

Direct molecular identification of Trypanosoma cruzi discrete typing units in domestic and peridomestic Triatoma infestans and Triatoma sordida from the Argentine Chaco.

PubMed

Maffey, L; Cardinal, M V; Ordóñez-Krasnowski, P C; Lanati, L A; Lauricella, M A; Schijman, A G; Gürtler, R E

2012-10-01

We assessed the distribution of Trypanosoma cruzi Discrete Typing Units (DTUs) in domestic and peridomestic Triatoma infestans and Triatoma sordida specimens collected in a well-defined rural area in Pampa del Indio, northeastern Argentina. Microscopically-positive bugs were randomly selected with a multi-level sampling design, and DTUs were identified using direct PCR strategies. TcVI predominated in 61% of 69 T. infestans and in 56% of 9 T. sordida. TcV was the secondary DTU in T. infestans (16%) and was found in 1 T. sordida specimen (11%). Three T. sordida (33%) were found infected with TcI, a DTU also identified in local Didelphis albiventris opossums. Mixed DTU infections occurred rarely (5%) and were detected both directly from the bugs' rectal ampoule and parasite cultures. The identified DTUs and bug collection sites of T. infestans were significantly associated. Bugs infected with TcV were almost exclusively captured in domiciles whereas those with TcVI were found similarly in domiciles and peridomiciles. All mixed infections occurred in domiciles. TcV-infected bugs fed more often on humans than on dogs, whereas TcVI-infected bugs showed the reverse pattern. T. sordida is a probable sylvatic vector of TcI linked to D. albiventris, and could represent a secondary vector of TcVI and TcV in the domestic/peridomestic cycle.

Direct molecular identification of Trypanosoma cruzi Discrete Typing Units in domestic and peridomestic Triatoma infestans and Triatoma sordida from the Argentine Chaco

PubMed Central

MAFFEY, L.; CARDINAL, M.V.; ORDÓÑEZ-KRASNOWSKI, P.C.; LANATI, L.A.; LAURICELLA, M.A.; SCHIJMAN, A.G.; GÜRTLER, R.E.

2013-01-01

SUMMARY We assessed the distribution of Trypanosoma cruzi Discrete Typing Units (DTUs) in domestic and peridomestic Triatoma infestans and Triatoma sordida specimens collected in a well-defined rural area in Pampa del Indio, northeastern Argentina. Microscopically-positive bugs were randomly selected with a multi-level sampling design, and DTUs were identified using direct PCR strategies. TcVI predominated in 61% of 69 T. infestans and in 56% of 9 T. sordida. TcV was the secondary DTU in T. infestans (16%) and was found in one T. sordida specimen (11%). Three T. sordida (33%) were found infected with TcI, a DTU also identified in local Didelphis albiventris opossums. Mixed DTU infections occurred rarely (5%) and were detected both directly from the bugs’ rectal ampoule and parasite cultures. The identified DTUs and bug collection sites of T. infestans were significantly associated. Bugs infected with TcV were almost exclusively captured in domiciles whereas those with TcVI were found similarly in domiciles and peridomiciles. All mixed infections occurred in domiciles. TcV-infected bugs fed more often on humans than on dogs, whereas TcVI-infected bugs showed the reverse pattern. T. sordida is a probable sylvatic vector of TcI linked to D. albiventris, and could represent a secondary vector of TcVI and TcV in the domestic/peridomestic cycle. PMID:23036510

Review of Available Water-Quality Data for the Southern Colorado Plateau Network and Characterization of Water Quality in Five Selected Park Units in Arizona, Colorado, New Mexico, and Utah, 1925 to 2004

USGS Publications Warehouse

Brown, Juliane B.

2008-01-01

Historical water-quality data in the National Park Service Southern Colorado Plateau Network have been collected irregularly and with little followup interpretation, restricting the value of the data. To help address these issues, to inform future water-quality monitoring planning efforts, and to address relevant National Park Service Inventory and Monitoring Program objectives, the U.S. Geological Survey, in cooperation with the National Park Service, compiled, reviewed, and summarized available historical water-quality data for 19 park units in the Southern Colorado Plateau Network. The data are described in terms of availability by major water-quality classes, park unit, site type, and selected identified water sources. The report also describes the geology, water resources, water-quality issues, data gaps, and water-quality standard exceedances identified in five of the park units determined to be of high priority. The five park units are Bandelier National Monument in New Mexico, Canyon de Chelly National Monument in Arizona, Chaco Culture National Historical Park in New Mexico, Glen Canyon National Recreation Area in Arizona and Utah, and Mesa Verde National Park in Colorado. Statistical summaries of water-quality characteristics are presented and considerations for future water-quality monitoring are provided for these five park units.

Ethnic characterization of a population of children exposed to high doses of arsenic via drinking water and a possible correlation with metabolic processes

PubMed Central

Bobillo, Cecilia; Navoni, Julio A; Olmos, Valentina; Merini, Luciano J; Villaamil Lepori, Edda; Corach, Daniel

2014-01-01

Because the ratio between the two major arsenic metabolites is related to the adverse health effects of arsenic, numerous studies have been performed to establish a relationship between the ability to metabolically detoxify arsenic and other variables, including exposure level, gender, age and ethnicity. Because ethnicity may play a key role and provide relevant information for heterogeneous populations, we characterized a group of 70 children from rural schools in the Argentinean provinces of Chaco and Santiago del Estero who were exposed to high levels of arsenic. We used genetic markers for maternal, paternal and bi-parental ancestry to achieve this goal. Our results demonstrate that the Amerindian maternal linages are present in 100% of the samples, whereas the Amerindian component transmitted through the paternal line is less than 10%. Informative markers for autosomal ancestry show a predominantly European ancestry, in which 37% of the samples contained between 90 and 99% European ancestry. The native American component ranged from 50 to 80% in 15.7% of the samples, and in all but four samples, the African component was less than 10%. Correlation analysis demonstrated that the ethnicity and the ratio of the excreted arsenic metabolites monomethyl arsenic and dimethyl arsenic are not associated, dismissing a relationship between ethnic origin and differential metabolism. PMID:24596592

ANALYSIS OF OIL-BEARING CRETACEOUS SANDSTONE HYDROCARBON RESERVOIRS, EXCLUSIVE OF THE DAKOTA SANDSTONE, ON THE JICARILLA APACHE INDIAN RESERVATION, NEW MEXICO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jennie Ridgley

2000-01-21

An additional 450 wells were added to the structural database; there are now 2550 wells in the database with corrected tops on the Juana Lopez, base of the Bridge Creek Limestone, and datum. This completes the structural data base compilation. Fifteen oil and five gas fields from the Mancos-ElVado interval were evaluated with respect to the newly defined sequence stratigraphic model for this interval. The five gas fields are located away from the structural margins of the deep part of the San Juan Basin. All the fields have characteristics of basin-centered gas and can be considered as continuous gas accumulationsmore » as recently defined by the U.S. Geological Survey. Oil production occurs in thinly interbedded sandstone and shale or in discrete sandstone bodies. Production is both from transgressive and regressive strata as redefined in this study. Oil production is both stratigraphically and structurally controlled with production occurring along the Chaco slope or in steeply west-dipping rocks along the east margin of the basin. The ElVado Sandstone of subsurface usage is redefined to encompass a narrower interval; it appears to be more time correlative with the Dalton Sandstone. Thus, it was deposited as part of a regressive sequence, in contrast to the underlying rock units which were deposited during transgression.« less

Sustainable vector control and management of Chagas disease in the Gran Chaco, Argentina

PubMed Central

Gürtler, Ricardo E.; Kitron, Uriel; Cecere, M. Carla; Segura, Elsa L.; Cohen, Joel E.

2007-01-01

Chagas disease remains a serious obstacle to health and economic development in Latin America, especially for the rural poor. We report the long-term effects of interventions in rural villages in northern Argentina during 1984–2006. Two community-wide campaigns of residual insecticide spraying immediately and strongly reduced domestic infestation and infection with Trypanosoma cruzi in Triatoma infestans bugs and dogs and more gradually reduced the seroprevalence of children <15 years of age. Because no effective surveillance and control actions followed the first campaign in 1985, transmission resurged in 2–3 years. Renewed interventions in 1992 followed by sustained, supervised, community-based vector control largely suppressed the reestablishment of domestic bug colonies and finally led to the interruption of local human T. cruzi transmission. Human incidence of infection was nearly an order of magnitude higher in peripheral rural areas under pulsed, unsupervised, community-based interventions, where human transmission became apparent in 2000. The sustained, supervised, community-based strategy nearly interrupted domestic transmission to dogs but did not eliminate T. infestans despite the absence of pyrethroid-insecticide resistance. T. infestans persisted in part because of the lack of major changes in housing construction and quality. Sustained community participation grew out of establishing a trusted relationship with the affected communities and the local schools. The process included health promotion and community mobilization, motivation, and supervision in close cooperation with locally nominated leaders. PMID:17913895

Ionospheric convection driven by NBZ currents

NASA Technical Reports Server (NTRS)

Rasmussen, C. E.; Schunk, R. W.

1987-01-01

Computer simulations of Birkeland currents and electric fields in the polar ionosphere during periods of northward IMF were conducted. When the IMF z component is northward, an additional current system, called the NBZ current system, is present in the polar cap. These simulations show the effect of the addition of NBZ currents on ionospheric convection, particularly in the polar cap. When the total current in the NBZ system is roughly 25 to 50 percent of the net region 1 and 2 currents, convection in the central portion of the polar cap reverses direction and turns sunward. This creates a pattern of four-cell convection with two small cells located in the polar cap, rotating in an opposite direction from the larger cells. When the Birkeland currents are fixed (constant current source), the electric field is reduced in regions of relatively high conductivity, which affects the pattern of ionospheric convection. Day-night asymmetries in conductivity change convection in such a way that the two polar-cap cells are located within the large dusk cell. When ionospheric convection is fixed (constant voltage source), Birkeland currents are increased in regions of relatively high conductivity. Ionospheric currents, which flow horizontally to close the Birkeland currents, are changed appreciably by the NBZ current system. The principal effect is an increase in ionospheric current in the polar cap.

Electric currents and coronal heating in NOAA active region 6952

NASA Technical Reports Server (NTRS)

Metcalf, T. R.; Canfield, R. C.; Hudson, H. S.; Mickey, D. L.; Wulser, J. -P.; Martens, P. C. H.; Tsuneta, S.

1994-01-01

We examine the spatial and temporal relationship between coronal structures observed with the soft X-ray telescope (SXT) on board the Yohkoh spacecraft and the vertical electric current density derived from photospheric vector magnetograms obtained using the Stokes Polarimeter at the Mees Solar Observatory. We focus on a single active region: AR 6952 which we observed on 7 days during 1991 December. For 11 independent maps of the vertical electric current density co-aligned with non-flaring X-ray images, we search for a morphological relationship between sites of high vertical current density in the photosphere and enhanced X-ray emission in the overlying corona. We find no compelling spatial or temporal correlation between the sites of vertical current and the bright X-ray structures in this active region.

Pure spin polarized current through a full magnetic silicene junction

NASA Astrophysics Data System (ADS)

Lorestaniweiss, Zeinab; Rashidian, Zeinab

2018-06-01

Using the Landauer-Buttiker formula, we investigate electronic transport in silicene junction composed of ferromagnetic silicene. The direction of magnetization in the middle region may change in a plane perpendicular to the junction, whereas the magnetization direction keep fixed upward in silicene electrodes. We investigate how the various magnetization directions in the middle region affect the electronic transport. We demonstrate that conductance depends on the orientation of magnetizations in the middle region. It is found that by changing the direction of the magnetization in the middle region, a pure spin up current can be achieved. This achievement makes this full magnetic junction a good design for a full spin-up current polarizer.

Line-of-sight magnetic flux imbalances caused by electric currents

NASA Technical Reports Server (NTRS)

Gary, G. Allen; Rabin, Douglas

1995-01-01

Several physical and observational effects contribute to the significant imbalances of magnetic flux that are often observed in active regions. We consider an effect not previously treated: the influence of electric currents in the photosphere. Electric currents can cause a line-of-sight flux imbalance because of the directionality of the magnetic field they produce. Currents associated with magnetic flux tubes produce larger imbalances than do smoothly-varying distributions of flux and current. We estimate the magnitude of this effect for current densities, total currents, and magnetic geometry consistent with observations. The expected imbalances lie approximately in the range 0-15%, depending on the character of the current-carying fields and the angle from which they are viewed. Observationally, current-induced flux imbalances could be indicated by a statistical dependence of the imbalance on angular distance from disk center. A general study of magnetic flux balance in active regions is needed to determine the relative importance of other- probably larger- effects such as dilute flux (too weak to measure or rendered invisible by radiative transfer effects), merging with weak background fields, and long-range connections between active regions.

Shear Alfven Wave Injection in the Magnetosphere by Ionospheric Modifications in the Absence of Electrojet Currents

NASA Astrophysics Data System (ADS)

Papadopoulos, K.; Eliasson, B.; Shao, X.; Labenski, J.; Chang, C.

2011-12-01

A new concept of generating ionospheric currents in the ULF/ELF range with modulated HF heating using ground-based transmitters even in the absence of electrojet currents is presented. The new concept relies on using HF heating of the F-region to modulate the electron temperature and has been given the name Ionospheric Current Drive (ICD). In ICD, the pressure gradient associated with anomalous or collisional F-region electron heating drives a local diamagnetic current that acts as an antenna to inject mainly Magneto-Sonic (MS) waves in the ionospheric plasma. The electric field associated with the MS wave drives Hall currents when it reaches the E region of the ionosphere. The Hall currents act as a secondary antenna that inject waves in the Earth-Ionosphere Waveguide (EIW) below and shear Alfven waves or EMIC waves upwards towards the conjugate regions. The paper presents: (i) Theoretical results using a cold Hall MHD model to study ICD and the generation of ULF/ELF waves by the modulation of the electron pressure at the F2-region with an intense HF electromagnetic wave. The model solves equations governing the dynamics of the shear Alfven and magnetosonic modes, of the damped modes in the diffusive Pedersen layer, and of the weakly damped helicon wave mode in the Hall-dominated E-region. The model incorporates realistic profile of the ionospheric conductivities and magnetic field configuration. We use the model to simulate propagation and dynamics of the low-frequency waves and their injection into the magnetosphere from the HAARP and Arecibo ionospheric heaters. (ii) Proof of principle experiments using the HAARP ionospheric heater in conjunction with measurements by the DEMETER satellite This work is supported by ONR MURI grant and DARPA BRIOCHE Program

The Effects of Bursty Bulk Flows on Global-Scale Current Systems

NASA Astrophysics Data System (ADS)

Yu, Y.; Cao, J.; Fu, H.; Lu, H.; Yao, Z.

2017-12-01

Using a global magnetospheric MHD model coupled with a kinetic ring current model, we investigate the effects of magnetotail dynamics, particularly the earthward bursty bulk flows (BBFs) produced by the tail reconnection, on the global-scale current systems. The simulation results indicate that after BBFs brake around X = -10 RE due to the dipolar "magnetic wall," vortices are generated on the edge of the braking region and inside the inner magnetosphere. Each pair of vortex in the inner magnetosphere disturbs the westward ring current to arc radially inward as well as toward high latitudes. The resultant pressure gradient on the azimuthal direction induces region-1 sense field-aligned component from the ring current, which eventually is diverted into the ionosphere at high latitudes, giving rise to a pair of field-aligned current (FAC) eddies in the ionosphere. On the edge of the flow braking region where vortices also emerge, a pair of region-1 sense FACs arises, diverted fromthe cross-tail duskward current, generating a substorm current wedge. This is again attributed to the increase of thermal pressure ahead of the bursty flows turning azimuthally. It is further found that when multiple BBFs, despite their localization, continually and rapidly impinge on the "wall," carrying sufficient tail plasma sheet population toward the Earth, they can lead to the formation of a new ring current. These results indicate the important role that BBFs play in bridging the tail and the inner magnetosphere ring current and bring new insight into the storm-substorm relation.

The effects of bursty bulk flows on global-scale current systems

NASA Astrophysics Data System (ADS)

Yu, Yiqun; Cao, Jinbin; Fu, Huishan; Lu, Haoyu; Yao, Zhonghua

2017-06-01

Using a global magnetospheric MHD model coupled with a kinetic ring current model, we investigate the effects of magnetotail dynamics, particularly the earthward bursty bulk flows (BBFs) produced by the tail reconnection, on the global-scale current systems. The simulation results indicate that after BBFs brake around X = -10 RE due to the dipolar "magnetic wall," vortices are generated on the edge of the braking region and inside the inner magnetosphere. Each pair of vortex in the inner magnetosphere disturbs the westward ring current to arc radially inward as well as toward high latitudes. The resultant pressure gradient on the azimuthal direction induces region-1 sense field-aligned component from the ring current, which eventually is diverted into the ionosphere at high latitudes, giving rise to a pair of field-aligned current (FAC) eddies in the ionosphere. On the edge of the flow braking region where vortices also emerge, a pair of region-1 sense FACs arises, diverted from the cross-tail duskward current, generating a substorm current wedge. This is again attributed to the increase of thermal pressure ahead of the bursty flows turning azimuthally. It is further found that when multiple BBFs, despite their localization, continually and rapidly impinge on the "wall," carrying sufficient tail plasma sheet population toward the Earth, they can lead to the formation of a new ring current. These results indicate the important role that BBFs play in bridging the tail and the inner magnetosphere ring current and bring new insight into the storm-substorm relation.

Field-aligned currents and large scale magnetospheric electric fields

NASA Technical Reports Server (NTRS)

Dangelo, N.

1980-01-01

D'Angelo's model of polar cap electric fields (1977) was used to visualize how high-latitude field-aligned currents are driven by the solar wind generator. The region 1 and region 2 currents of Iijima and Potemra (1976) and the cusp field-aligned currents of Wilhjelm et al. (1978) and McDiarmid et al. (1978) are apparently driven by different generators, although in both cases the solar wind is their ultimate source.

A statistical study of current-sheet formation above solar active regions based on selforganized criticality

NASA Astrophysics Data System (ADS)

Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M.; Anastasiadis, A.; Toutountzi, A.

2013-09-01

We treat flaring solar active regions as physical systems having reached the self-organized critical state. Their evolving magnetic configurations in the low corona may satisfy an instability criterion, related to the excession of a specific threshold in the curl of the magnetic field. This imposed instability criterion implies an almost zero resistivity everywhere in the solar corona, except in regions where magnetic-field discontinuities and. hence, local currents, reach the critical value. In these areas, current-driven instabilities enhance the resistivity by many orders of magnitude forming structures which efficiently accelerate charged particles. Simulating the formation of such structures (thought of as current sheets) via a refined SOC cellular-automaton model provides interesting information regarding their statistical properties. It is shown that the current density in such unstable regions follows power-law scaling. Furthermore, the size distribution of the produced current sheets is best fitted by power laws, whereas their formation probability is investigated against the photospheric magnetic configuration (e.g. Polarity Inversion Lines, Plage). The average fractal dimension of the produced current sheets is deduced depending on the selected critical threshold. The above-mentioned statistical description of intermittent electric field structures can be used by collisional relativistic test particle simulations, aiming to interpret particle acceleration in flaring active regions and in strongly turbulent media in astrophysical plasmas. The above work is supported by the Hellenic National Space Weather Research Network (HNSWRN) via the THALIS Programme.

Convection Constraints and Current Sheet Thinning During the Substorm Growth Phase

NASA Astrophysics Data System (ADS)

Otto, A.; Hsieh, M.

2012-12-01

A typical property during the growth phase of geomagnetic substorms is the thinning of the near-Earth current sheet, most pronounced in the region between 6 and 15 RE. We propose that the cause for this current sheet thinning is convection from the midnight tail region to the dayside to replenish magnetospheric magnetic flux that is eroded at the dayside as a result of dayside reconnection. Slow (adiabatic) convection from the near-Earth tail region toward the dayside must conserve the entropy on magnetic field lines. This constraint prohibits a source of magnetic flux from a region further out in the magnetotail. Thus the near-Earth tail region is increasingly depleted of magnetic flux (the Erickson and Wolf [1980] problem) with entropy matching that of flux tubes that are eroded on the dayside. It is proposed that the magnetic flux depletion in the near-Earth tail forces the formation of thin current layers. The process is illustrated and examined by three-dimensional meso-scale MHD simulations. It is shown that the simulations yield a time scale, location, and other general characteristics of the current sheet evolution consistent with observations during the substorm growth phase. The developing thin current sheet is easily destabilized and can undergo localized reconnection events. We present properties of the thinning current sheet, the associated entropy evolution, examples of localized reconnection onset and we discuss the dependence of this process on external parameters such the global reconnection rate.

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. II - NOAA active region 5747 (1989 October)

NASA Technical Reports Server (NTRS)

Leka, K. D.; Canfield, Richard C.; Mcclymont, A. N.; De La Beaujardiere, J.-F.; Fan, Yuhong; Tang, F.

1993-01-01

The paper describes October 1989 observations in NOAA Active Region 5747 of the morphology of energetic electron precipitation and high-pressure coronal flare plasmas of three flares and their relation to the vector magnetic field and vertical electric currents. The H-alpha spectroheliograms were coaligned with the vector magnetograms using continuum images of sunspots, enabling positional accuracy of a few arcsec. It was found that, during the gradual phase, the regions of the H-alpha flare that show the effects of enhanced pressure in the overlying corona often encompass extrema of the vertical current density, consistent with earlier work showing a close relationship between H-alpha emission and line-of-sight currents. The data are also consistent with the overall morphology and evolution described by erupting-filament models such as those of Kopp and Pneuman (1976) and Sturrock (1989).

A case study of magnetotail current sheet disruption and diversion

NASA Technical Reports Server (NTRS)

Lui, A. T. Y.; Lopez, R. E.; Krimigis, S. M.; Mcentire, R. W.; Zanetti, L. J.

1988-01-01

On June 1, 1985 the AMPTE/CCE spacecraft (at a geocentric distance of about 8.8 earth radii at the midnight neutral sheet region) observed a dispersionless energetic particle injection and an increase in magnetic field magnitude, which are features commonly attributed to disruption of the near-earth cross-tail current sheet during substorm expansion onsets. An analysis based on high time-resolution measurements from the magnetometer and the energetic particle detector indicates that the current sheet disruption region exhibited localized (less than 1 earth radius) and transient (less than 1 min) particle intensity enhancements, accompanied by complex magnetic field changes with occasional development of a southward magnetic field component. Similar features are seen in other current disruption/diversion events observed by the CCE. The present analysis suggests that the current disruption region is quite turbulent, similar to laboratory experiments on current sheet disruption, with signatures unlike those expected from an X-type neutral line configuration. No clear indication of periodicity in any magnetic field parameter is discernible for this current disruption event.

Finite geometry effects of field-aligned currents

NASA Technical Reports Server (NTRS)

Fung, Shing F.; Hoffman, R. A.

1992-01-01

Results are presented of model calculations of the magnetic field produced by finite current regions that would be measured by a spaceborne magnetometer. Conditions were examined under which the infinite current sheet approximation can be applied to the calculation of the field-aligned current (FAC) density, using satellite magnetometer data. The accuracy of the three methods used for calculating the current sheet normal direction with respect to the spacecraft trajectory was assessed. It is shown that the model can be used to obtain the position and the orientation of the spacecraft trajectory through the FAC region.

Reduction, analysis, and properties of electric current systems in solar active regions

NASA Technical Reports Server (NTRS)

Gary, G. Allen; Demoulin, Pascal

1995-01-01

The specific attraction and, in large part, the significance of solar magnetograms lie in the fact that they give the most important data on the electric currents and the nonpotentiality of active regions. Using the vector magnetograms from the Marshall Space Flight Center (MSFC), we employ a unique technique in the area of data analysis for resolving the 180 deg ambiguity in order to calculate the spatial structure of the vertical electric current density. The 180 deg ambiguity is resolved by applying concepts from the nonlinear multivariable optimization theory. The technique is shown to be of particular importance in very nonpotential active regions. The characterization of the vertical electric current density for a set of vector magnetograms using this method then gives the spatial scale, locations, and magnitude of these current systems. The method, which employs an intermediate parametric function which covers the magnetogram and which defines the local `preferred' direction, minimizes a specific functional of the observed transverse magnetic field. The specific functional that is successful is the integral of the square of the vertical current density. We find that the vertical electric current densities have common characteristics for the extended bipolar (beta) (gamma) (delta)-regions studied. The largest current systems have j(sub z)'s which maximizes around 30 mA/sq m and have a linear decreasing distribution to a diameter of 30 Mn.

Reduction, Analysis, and Properties of Electric Current Systems in Solar Active Regions

NASA Technical Reports Server (NTRS)

Gary, G. Allen; Demoulin, Pascal

1995-01-01

The specific attraction and, in large part, the significance of solar vector magnetograms lie in the fact that they give the most important data on the electric currents and the nonpotentiality of active regions. Using the vector magnetograms from the Marshall Space Flight Center (MSFC), we employ a unique technique in the area of data analysis for resolving the 180 degree ambiguity in order to calculate the spatial structure of the vertical electric current density. The 180 degree ambiguity is resolved by applying concepts from the nonlinear multivariable optimization theory. The technique is shown to be of particular importance in very nonpotential active regions. The characterization of the vertical electric current density for a set of vector magnetograms using this method then gives the spatial scale, locations, and magnitude of these current systems. The method, which employs an intermediate parametric function which covers the magnetogram and which defines the local "preferred" direction, minimizes a specific functional of the observed transverse magnetic field. The specific functional that is successful is the integral of the square of the vertical current density. We find that the vertical electric current densities have common characteristics for the extended bipolar beta gamma delta-regions studied. The largest current systems have j(sub z)'s which maximizes around 30 mA per square meter and have a linear decreasing distribution to a diameter of 30 Mm.

Child mortality and poverty in three world regions (the West, Asia and Sub-Saharan Africa) 1988-2010: Evidence of relative intra-regional neglect?

PubMed

Pritchard, Colin; Keen, Steven

2016-12-01

Poverty kills children. This study assesses the relationship between poverty and child mortality rates (CMRs) in 71 societies from three world regions to determine whether some countries, relative to their region, neglect their children. Spearman rank order correlations were calculated to determine any association between the CMR and poverty data, including income inequality and gross national income. A current CMR one standard deviation (SD) above or below the regional average and a percentage change between 1988 and 2010 were used as the measures to assess the progress of nations. There were positive significant correlations between higher CMRs and relative poverty measures in all three regions. In Western countries, the current CMRs in the USA, New Zealand and Canada were 1 SD below the Western mean. The narrowest income inequalities, apart from Japan, were seen in the Scandinavian nations alongside low CMRs. In Asia, the current CMRs in Pakistan, Myanmar and India were the highest in their region and were 1 SD below the regional mean. Alongside South Korea, these nations had the lowest percentage reductions in CMRs. In Sub-Saharan Africa, the current CMRs in Somalia, Burkina Faso, Sierra Leone, Chad, Democratic Republic of Congo and Angola were the highest in their region and were 1 SD below the regional mean. Those concerned with the pursuit of social justice need to alert their societies to the corrosive impact of poverty on child mortality. Progress in reducing CMRs provides an indication of how well nations are meeting the needs of their children. Further country-specific research is required to explain regional differences.

Upward electron beams measured by DE-1 - A primary source of dayside region-1 Birkeland currents

NASA Technical Reports Server (NTRS)

Burch, J. L.; Reiff, P. H.; Sugiura, M.

1983-01-01

Measurements made by the High Altitude Plasma Instrument on DE-1 have shown that intense upward electron beams with energies from about 20 eV to about 200 eV are a common feature of the region just equatorward of the morning-side polar cusp. Computations of the currents carried by these beams and by the precipitating cusp electrons show excellent agreement with the simultaneous DE-1 magnetometer measurements for both upward and downward Birkeland currents. The data indicate that cold ionospheric electrons, which carry the downward region-1 Birkeland currents on the morning side, are accelerated upward by potential drops of a few tens of eV at altitudes of several thousand kilometers. This acceleration process allows spacecraft above those altitudes to measure routinely the charge carriers of both downward and upward current systems.

Field-aligned current and auroral Hall current characteristics derived from the Swarm constellation

NASA Astrophysics Data System (ADS)

Huang, Tao; Wang, Hui; Hermann, Luehr

2017-04-01

On the basis of field-aligned currents (FACs) and Hall currents derived from high-resolution magnetic field data of the Swarm constellation the average characteristics of these two current systems in the auroral regions are comprehensively investigated by statistical methods. This is the first study considering both current types simultaneously and for both hemispheres. The FAC distribution, derived from the Swarm dual-spacecraft approach, reveals the well-known features of Region 1 (R1) and Region 2 (R2) FACs. At high latitudes, Region 0 (R0) FACs appear on the dayside. Their direction depends on the orientation of the interplanetary magnetic field (IMF) By component. Of particular interest is the distribution of auroral Hall currents. The most prominent auroral electrojets are found to be closely controlled by the solar wind input. But there is no dependence on the IMF By orientation. The eastward electrojet is about twice as strong in summer as in winter. Conversely, the westward electrojet shows less dependence on season. Part of the electrojet current is closed over the polar cap. Here the seasonal variation of conductivity mainly controls the current density. There is a clear channeling of return currents over the polar cap. Depending on IMF By orientation most of the current is flowing either on the dawn or dusk side. The direction of Hall currents in the noon sector depends directly on the orientation of the IMF By. This is true for both signs of the IMF Bz component. But largest differences between summer and winter seasons are found for northward IMF Bz. Around the midnight sector the westward substorm electrojet is dominating. As expected, it is highly dependent on magnetic activity, but shows only little response to the IMF By polarity.

Spatial and temporal distribution of house infestation by Triatoma infestans in the Toro Toro municipality, Potosi, Bolivia.

PubMed

Espinoza Echeverria, Jorge; Rodriguez, Antonio Nogales; Cortez, Mirko Rojas; Diotaiuti, Liléia Gonçalves; Gorla, David E

2017-02-02

Triatoma infestans is the main vector of Trypanosoma cruzi in Bolivia. The species is present both in domestic and peridomestic structures of rural areas, and in wild ecotopes of the Andean valleys and the Great Chaco. The identification of areas persistently showing low and high house infestation by the vector is important for the management of vector control programs. This study aimed at analyzing the temporal and spatial distribution of house infestation by T. infestans in the Toro Toro municipality (Potosi, Bolivia) between 2009 and 2014, and its association with environmental variables. House infestation and T. infestans density were calculated from entomological surveys of houses in the study area, using a fixed-time effort sampling technique. The spatial heterogeneity of house infestation was evaluated using the SatScan statistic. Association between house infestation with Bioclim variables (Worldclim database) and altitude was analyzed using a generalized linear model (GLM) with a logit link. Model selection was based on the Akaike information criteria after eliminating collinearity between variables using the variable inflation factor. The final model was used to create a probability map of house infestation for the Toro Toro municipality. A total of 73 communities and 16,489 house evaluation events were analyzed. Presence of T. infestans was recorded on 480 house evaluation events, giving an overall annual infestation of 2.9% during the studied period (range 1.5-5.4% in 2009 and 2012). Vector density remained at about 1.25 insects/ house. Infestation was highly aggregated in five clusters, including 11 communities. Relative risk of infestation within these clusters was 1.7-3.9 times the value for the regional average. Four environmental variables were identified as good descriptors of house infestation, explaining 57% of house infestation variability. The model allowed the estimation of a house infestation surface for the Toro Toro municipality. This study shows that residual and persistent populations of T. infestans maintain low house infestation, representing a potential risk for the transmission of T. cruzi in these communities, and it is possible to stratify house infestation using EV, and produce a risk map to guide the activities of vector control interventions in the municipality of Toro Toro (Potosi, Bolivia).

Double gate graphene nanoribbon field effect transistor with single halo pocket in channel region

NASA Astrophysics Data System (ADS)

Naderi, Ali

2016-01-01

A new structure for graphene nanoribbon field-effect transistors (GNRFETs) is proposed and investigated using quantum simulation with a nonequilibrium Green's function (NEGF) method. Tunneling leakage current and ambipolar conduction are known effects for MOSFET-like GNRFETs. To minimize these issues a novel structure with a simple change of the GNRFETs by using single halo pocket in the intrinsic channel region, "Single Halo GNRFET (SH-GNRFET)", is proposed. An appropriate halo pocket at source side of channel is used to modify potential distribution of the gate region and weaken band to band tunneling (BTBT). In devices with materials like Si in channel region, doping type of halo and source/drain regions are different. But, here, due to the smaller bandgap of graphene, the mentioned doping types should be the same to reduce BTBT. Simulations have shown that in comparison with conventional GNRFET (C-GNRFET), an SH-GNRFET with appropriately halo doping results in a larger ON current (Ion), smaller OFF current (Ioff), a larger ON-OFF current ratio (Ion/Ioff), superior ambipolar characteristics, a reduced power-delay product and lower delay time.

Cerebral cortex activation mapping upon electrical muscle stimulation by 32-channel time-domain functional near-infrared spectroscopy.

PubMed

Re, Rebecca; Muthalib, Makii; Contini, Davide; Zucchelli, Lucia; Torricelli, Alessandro; Spinelli, Lorenzo; Caffini, Matteo; Ferrari, Marco; Quaresima, Valentina; Perrey, Stephane; Kerr, Graham

2013-01-01

The application of different EMS current thresholds on muscle activates not only the muscle but also peripheral sensory axons that send proprioceptive and pain signals to the cerebral cortex. A 32-channel time-domain fNIRS instrument was employed to map regional cortical activities under varied EMS current intensities applied on the right wrist extensor muscle. Eight healthy volunteers underwent four EMS at different current thresholds based on their individual maximal tolerated intensity (MTI), i.e., 10 % < 50 % < 100 % < over 100 % MTI. Time courses of the absolute oxygenated and deoxygenated hemoglobin concentrations primarily over the bilateral sensorimotor cortical (SMC) regions were extrapolated, and cortical activation maps were determined by general linear model using the NIRS-SPM software. The stimulation-induced wrist extension paradigm significantly increased activation of the contralateral SMC region according to the EMS intensities, while the ipsilateral SMC region showed no significant changes. This could be due in part to a nociceptive response to the higher EMS current intensities and result also from increased sensorimotor integration in these cortical regions.

Measurement of Beta Particles Induced Electron-Hole Pairs Recombination in Depletion Region of GaAs PN Junction

NASA Astrophysics Data System (ADS)

Chen, Hai-Yang; Jiang, Lan; Li, Da-Rang

2011-05-01

PN junctions and schottky diodes are widely employed as electron-hole pair collectors in electron beam induced current (EBIC) techniques and betavoltaic batteries, in which the recombination in depletion regions is ignored. We measured the beta particles induced electron-hole pairs recombination in the depletion region of a GaAs P+PN+ junction, based on comparisons between measured short currents and ideal values. The results show that only 20% electron-hole pairs in the depletion can be collected, causing the short current. This indicates an electron-hole pair diffusion length of 0.2μm in the depletion region. Hence, it is necessary to evaluate the recombination in the EBIC techniques and betavoltaic design.

Coastal currents and mass transport of surface sediments over the shelf regions of Monterey Bay, California

USGS Publications Warehouse

Wolf, S.C.

1970-01-01

In Monterey Bay, the highest concentrations of medium and fine sands occur nearshore between ten and thirty fathoms. Silt and clay accumulate in greater depths. Contours of median diameter roughly parallel the isobaths. Fine-grained materials are supplied to the bay region from erosion of cliffs which partly surround Monterey Bay, from sediment laden river discharge, and from continual reworking of widespread Pleistocene and Recent sea floor sediments. These sediments in turn are picked up by coastal currents and distributed over the shelf regions by present day current regimes. Studies of bottom currents over the shelf regions and in Monterey Canyon have revealed patterns which vary with seasonal changes. Current patterns during August and September exhibit remarkable symmetry about the axis of Monterey Submarine Canyon. Central Shelf currents north and south of Monterey Canyon flowed northwest at an average rate of 0.2 knots and south at 0.3 knots respectively. On the North Shelf between January and March currents flowed east to southeast at 0.3-0.5 knots with mirror image patterns above the South Shelf during the same period. Irregular current flow in the canyon indicates a complex current structure with frequent shifts in counterclockwise and clockwise direction over very short periods of time. Bottom topography of the canyon complex often causes localization of canyon currents. One particular observation at a depth of 51 fathoms indicated up-canyon flow at a rate of 0.2 knots. Most of the observed currents are related to seasonal variations, upwelling, ocean swell patterns, and to changes in the California and Davidson currents. Changes in current regimes are reflected in the patterns of sediment distribution and transport. Sediment transport is chiefly parallel to the isobaths, particularly on the North and South Shelf regions. Complex dispersal patterns are observed near Monterey Canyon and Moss Landing Harbor jetties. Longshore currents move sediments southward except near Monterey Canyon which acts as a physiographic barrier and the extreme southern end of the bay where currents are non persistent. Some sediments are also transported offshore by rip currents and other agencies and deposited in deeper, quieter waters. Supply of sediments to the canyon head results in over-filling and steepening with subsequent mass movement of sediments seaward followed by deposition in channels and on the broad deep sea fan. ?? 1970.

Current Sheet Thinning Associated with Dayside Reconnection

NASA Astrophysics Data System (ADS)

Hsieh, M.; Otto, A.; Ma, X.

2011-12-01

The thinning of the near-Earth current sheet during the growth phase is of critical importance to understand geomagnetic substorms and the conditions that lead to the onset of the expansion phase. We have proposed that convection from the midnight tail region to the dayside as the cause for this current sheet thinning. Adiabatic convection from the near-Earth tail region toward the dayside must conserve the entropy on magnetic field lines. This constraint prohibits a source of the magnetic flux from a region further out in the magnetotail. Thus the near-Earth tail region is increasingly depleted of magnetic flux (the Erickson and Wolf [1980] problem) with entropy matching that of flux tubes that are eroded on the dayside. The process is examined by three-dimensional MHD simulations. The properties of the current sheet thinning are determined as a function of the magnitude of convection toward the dayside and the lobe boundary conditions. It is shown that the model yields a time scale, location, and other general characteristics of the current sheet evolution consistent with observations during the substorm growth phase.

Investigating the Relationship between Ocean Surface Currents and Seasonal Precipitation in the Western United States

NASA Astrophysics Data System (ADS)

Chiang, F.; AghaKouchak, A.

2017-12-01

While many studies have explored the predictive capabilities of teleconnections associated with North American climate, currently established teleconnections offer limited predictability for rainfall in the Western United States. A recent example was the 2015-16 California drought in which a strong ENSO signal did not lead to above average precipitation as was expected. From an exploration of climate and ocean variables available from satellite data, we hypothesize that ocean currents can provide additional information to explain precipitation variability and improve seasonal predictability on the West Coast. Since ocean currents are influenced by surface wind and temperatures, characterizing connections between currents and precipitation patterns has the potential to further our understanding of coastal weather patterns. For the study, we generated gridded point correlation maps to identify ocean areas with high correlation to precipitation time series corresponding to climate regions in the West Coast region. We also used other statistical measures to evaluate ocean `hot spot' regions with significant correlation to West Coast precipitation. Preliminary results show that strong correlations can be found in the tropical regions of the globe.

Nonlinear MHD simulation of current drive by multi-pulsed coaxial helicity injection in spherical torus

NASA Astrophysics Data System (ADS)

Kanki, Takashi; Nagata, Masayoshi; Kagei, Yasuhiro

2011-10-01

The dynamics of structures of magnetic field, current density, and plasma flow generated during multi-pulsed coaxial helicity injection in spherical torus is investigated by 3-D nonlinear MHD simulations. During the driven phase, the flux and current amplifications occur due to the merging and magnetic reconnection between the preexisting plasma in the confinement region and the ejected plasma from the gun region involving the n = 1 helical kink distortion of the central open flux column (COFC). Interestingly, the diamagnetic poloidal flow which tends toward the gun region is then observed due to the steep pressure gradients of the COFC generated by ohmic heating through an injection current winding around the inboard field lines, resulting in the formation of the strong poloidal flow shear at the interface between the COFC and the core region. This result is consistent with the flow shear observed in the HIST. During the decay phase, the configuration approaches the axisymmetric MHD equilibrium state without flow because of the dissipation of magnetic fluctuation energy to increase the closed flux surfaces, suggesting the generation of ordered magnetic field structure. The parallel current density λ concentrated in the COFC then diffuses to the core region so as to reduce the gradient in λ, relaxing in the direction of the Taylor state.

Radial expansion of the tail current disruption during substorms - A new approach to the substorm onset region

NASA Technical Reports Server (NTRS)

Ohtani, S.; Kokubun, S.; Russell, C. T.

1992-01-01

A new method is used to examine the radial expansion of the tail current disruption and the substorm onset region. The expansion of the disruption region is specified by examining the time sequence (phase relationship) between the north-south component and the sun-earth component. This method is tested by applying it to the March 6, 1979, event. The phase relationship indicates that the current disruption started on the earthward side of the spacecraft, and expanded tailward past the spacecraft. The method was used for 13 events selected from the ISEE magnetometer data. The results indicate that the current disruption usually starts in the near-earth magnetotail and often within 15 RE from the earth.

Fragmented Canopies Control the Regimes of Gravity Current Development

NASA Astrophysics Data System (ADS)

Barcelona, Aina; Serra, Teresa; Colomer, Jordi

2018-03-01

Coastal ecosystems (marine littoral regions, wetlands, and deltas) are regions of high biological productivity. However, they are also one of the world's most threatened ecosystems. Wetlands are characterized by aquatic vegetation adapted to high salinity levels and climatic variations. Wetland canopies buffer these hydrodynamic and atmospheric variations and help retain sediment by reducing current velocity during sea storms or runoff after periods of rain. This work focuses on the effect of the presence of a gap (i.e., nonvegetated zone) parallel to the direction of the main current has on the sedimentation and hydrodynamics of a gravity current. The study aims to (1) address the behavior of a gravity current in a vegetated region compared to one without vegetation (i.e., the gap), (2) determine the effect gap size has on how a gravity current evolves, and 3) determine the effect gap sizes have on the sedimentary rates from a gravity current. Laboratory experiments were carried out in a flume using four different sediment concentrations, four different canopy densities (884, 354, 177, and 0 plants·m-2) and three different gap widths (H/2, H, and 1.5H, where H is the height of the water). This work shows that a gravity current's evolution and its sedimentary rates depend on the fractional volume occupied by the vegetation. While current dynamics in experiments with wider gaps are similar to the nonvegetated case, for smaller gaps the dynamics are closer to the fully vegetated case. Nonetheless, the gravity current exhibits the same behavior in both the vegetated region and the gap.

Field-aligned currents in Saturn's northern nightside magnetosphere: Evidence for interhemispheric current flow associated with planetary period oscillations

NASA Astrophysics Data System (ADS)

Hunt, G. J.; Cowley, S. W. H.; Provan, G.; Bunce, E. J.; Alexeev, I. I.; Belenkaya, E. S.; Kalegaev, V. V.; Dougherty, M. K.; Coates, A. J.

2015-09-01

We investigate the magnetic perturbations associated with field-aligned currents observed on 34 Cassini passes over the premidnight northern auroral region during 2008. These are found to be significantly modulated not only by the northern planetary-period oscillation (PPO) system, similar to the southern currents by the southern PPO system found previously, but also by the southern PPO system as well, thus providing the first clear evidence of PPO-related interhemispheric current flow. The principal field-aligned currents of the two PPO systems are found to be co-located in northern ionospheric colatitude, together with the currents of the PPO-independent (subcorotation) system, located between the vicinity of the open-closed field boundary and field lines mapping to ~9 Saturn radius (Rs) in the equatorial plane. All three systems are of comparable magnitude, ~3 MA in each PPO half-cycle. Smaller PPO-related field-aligned currents of opposite polarity also flow in the interior region, mapping between ~6 and ~9 Rs in the equatorial plane, carrying a current of ~ ±2 MA per half-cycle, which significantly reduce the oscillation amplitudes in the interior region. Within this interior region the amplitudes of the northern and southern oscillations are found to fall continuously with distance along the field lines from the corresponding hemisphere, thus showing the presence of cross-field currents, with the southern oscillations being dominant in the south, and modestly lower in amplitude than the northern oscillations in the north. As in previous studies, no oscillations related to the opposite hemisphere are found on open field lines in either hemisphere.

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

Severe wind and snow storms hit the Pacific Northwest region on December 14 – 15, 2006, following severe flooding during the past few days. The severe weather resulted in major power outages through the region. At peak there were 1.8 million customers without power which included BC Hydro in Canada. Currently, there are over 1.5 million outages in the region as a result of the Pacific Northwest Storms. This represents about 42 percent of customers in affected utility service areas in Oregon and Washington. See table below. Because the current wind and snow storms are coming on the heels ofmore » extensive flooding in the region, electric utilities are experiencing damage. Wind gusts reached close to 100 mph in some areas of the region. The storm is expected to bring its strong winds and heavy snow into Idaho, Montana and Wyoming Friday and into the weekend. There are currently no reported major impacts to the petroleum and natural gas infrastructure.« less

An Assessment of Regional Water Resources and Agricultural Sustainability in the Mississippi River Alluvial Aquifer System of Mississippi and Arkansas Under Current and Future Climate

NASA Astrophysics Data System (ADS)

Rigby, J.; Reba, M.

2011-12-01

The Lower Mississippi River Alluvial Plain is a highly productive agricultural region for rice, soy beans, and cotton that depends heavily on irrigation. Development of the Mississippi River Alluvial Aquifer (MRAA), one of the more prolific agricultural aquifers in the country, has traditionally been the primary source for irrigation in the region yielding over 1,100 Mgal/day to irrigation wells. Increasingly, the realities of changing climate and rapidly declining water tables have highlighted the necessity for new water management practices. Tail-water recovery and reuse is a rapidly expanding practice due in part to the efforts and cost-sharing of the NRCS, but regional studies of the potential for such practices to alleviate groundwater mining under current and future climate are lacking. While regional studies of aquifer geology have long been available, including assessments of regional groundwater flow, much about the aquifer is still not well understood including controls on recharge rates, a crucial component of water management design. We review the trends in regional availability of surface and groundwater resources, their current status, and the effects of recent changes in management practices on groundwater decline in Mississippi and Arkansas. Global and regional climate projections are used to assess scenarios of sustainable aquifer use under current land use and management along with the potential for more widely practiced surface water capture and reuse to alleviate groundwater decline. Finally, we highlight crucial knowledge gaps and challenges associated with the development of water management practices for sustainable agricultural use in the region.

High-resolution disruption halo current measurements using Langmuir probes in Alcator C-Mod

NASA Astrophysics Data System (ADS)

Tinguely, R. A.; Granetz, R. S.; Berg, A.; Kuang, A. Q.; Brunner, D.; LaBombard, B.

2018-01-01

Halo currents generated during disruptions on Alcator C-Mod have been measured with Langmuir ‘rail’ probes. These rail probes are embedded in a lower outboard divertor module in a closely-spaced vertical (poloidal) array. The dense array provides detailed resolution of the spatial dependence (~1 cm spacing) of the halo current distribution in the plasma scrape-off region with high time resolution (400 kHz digitization rate). As the plasma limits on the outboard divertor plate, the contact point is clearly discernible in the halo current data (as an inversion of current) and moves vertically down the divertor plate on many disruptions. These data are consistent with filament reconstructions of the plasma boundary, from which the edge safety factor of the disrupting plasma can be calculated. Additionally, the halo current ‘footprint’ on the divertor plate is obtained and related to the halo flux width. The voltage driving halo current and the effective resistance of the plasma region through which the halo current flows to reach the probes are also investigated. Estimations of the sheath resistance and halo region resistivity and temperature are given. This information could prove useful for modeling halo current dynamics.

GRIL: genome rearrangement and inversion locator.

PubMed

Darling, Aaron E; Mau, Bob; Blattner, Frederick R; Perna, Nicole T

2004-01-01

GRIL is a tool to automatically identify collinear regions in a set of bacterial-size genome sequences. GRIL uses three basic steps. First, regions of high sequence identity are located. Second, some of these regions are filtered based on user-specified criteria. Finally, the remaining regions of sequence identity are used to define significant collinear regions among the sequences. By locating collinear regions of sequence, GRIL provides a basis for multiple genome alignment using current alignment systems. GRIL also provides a basis for using current inversion distance tools to infer phylogeny. GRIL is implemented in C++ and runs on any x86-based Linux or Windows platform. It is available from http://asap.ahabs.wisc.edu/gril

DE 1 observations of theta aurora plasma source regions and Birkeland current charge carriers

NASA Technical Reports Server (NTRS)

Menietti, J. D.; Burch, J. L.

1987-01-01

Detailed analyses of the DE 1 high-altitude plasma instrument electron and ion data have been performed for four passes during which theta auroras were observed. The data indicate that the theta auroras occur on what appear to be closed field lines with particle signatures and plasma parameters that are quite similar to those of the magnetospheric boundary plasma sheet. The field-aligned currents computed from particle fluxes in the energy range 18-13 keV above the theta auroras are observed to be generally downward on the dawnside of the arcs with a narrower region of larger (higher density) upward currents on the duskside of the arcs. These currents are carried predominantly by field-aligned beams of accelerated cold electrons. Of particualr interest in regions of upward field-aligned current are downward electron beams at energies less than the inferred potential drop above the spacecraft.

Spontaneous Currents in Superconducting Systems with Strong Spin-Orbit Coupling

NASA Astrophysics Data System (ADS)

Mironov, S.; Buzdin, A.

2017-02-01

We show that Rashba spin-orbit coupling at the interface between a superconductor and a ferromagnet should produce a spontaneous current in the atomic thickness region near the interface. This current is counterbalanced by the superconducting screening current flowing in the region of the width of the London penetration depth near the interface. Such a current-carrying state creates a magnetic field near the superconductor surface, generates a stray magnetic field outside the sample edges, changes the slope of the temperature dependence of the critical field Hc 3 , and may generate the spontaneous Abrikosov vortices near the interface.

Self-focusing of a high current density ion beam extracted with concave electrodes in a low energy region around 150 eV.

PubMed

Hirano, Y; Kiyama, S; Koguchi, H; Sakakita, H

2014-02-01

Spontaneous self-focusing of ion beam with high current density (Jc ∼ 2 mA/cm(2), Ib ∼ 65 mA) in low energy region (∼150 eV) is observed in a hydrogen ion beam extracted from an ordinary bucket type ion source with three electrodes having concave shape (acceleration, deceleration, and grounded electrodes). The focusing appears abruptly in the beam energy region over ∼135-150 eV, and the Jc jumps up from 0.7 to 2 mA/cm(2). Simultaneously a strong electron flow also appears in the beam region. The electron flow has almost the same current density. Probably these electrons compensate the ion space charge and suppress the beam divergence.

Analysis of source/drain engineered 22nm FDSOI using high-k spacers

NASA Astrophysics Data System (ADS)

Malviya, Abhishek Kumar; Chauhan, R. K.

2018-04-01

While looking at the current classical scaling of devices there are lots of short channel effects come into consideration. In this paper, a novel device structure is proposed that is an improved structure of Modified Source(MS) FDSOI in terms of better electrical performance, on current and reduced off state leakage current with a higher Ion/Ioff ratio that helps in fast switching of low power nano electronic devices. Proposed structure has Modified drain and source regions with two different type to doping profile at 22nm gate length. In the upper part of engineered region (MD and MS) the doping concentration is kept high and less in the lower region. The purpose was to achieve low parasitic capacitance in source and drain region by reducing doping concentration [1].

Rethinking the solar flare paradigm

NASA Astrophysics Data System (ADS)

D, B. MELROSE

2018-07-01

It is widely accepted that solar flares involve release of magnetic energy stored in the solar corona above an active region, but existing models do not include the explicitly time-dependent electrodynamics needed to describe such energy release. A flare paradigm is discussed that includes the electromotive force (EMF) as the driver of the flare, and the flare-associated current that links different regions where magnetic reconnection, electron acceleration, the acceleration of mass motions and current closure occur. The EMF becomes localized across regions where energy conversion occurs, and is involved in energy propagation between these regions.

Current Closure in the Auroral Ionosphere: Results from the Auroral Current and Electrodynamics Structure Rocket Mission

NASA Technical Reports Server (NTRS)

Kaeppler, S. R.; Kletzing, C. A.; Bounds, S. R.; Gjerloev, J. W.; Anderson, B. J.; Korth, H.; LaBelle, J. W.; Dombrowski, M. P.; Lessard, M.; Pfaff, R. F.;

Current Closure in the Auroral Ionosphere: Results from the Auroral Current and Electrodynamics Structure Rocket Mission

NASA Technical Reports Server (NTRS)

Kaeppler, S. R.; Kletzing, C. A.; Bounds, S. R.; Gjerloev, J. W.; Anderson, B. J.; Korth, H.; LaBelle, J. W.; Dombrowski, M. P.; Lessard, M.; Pfaff, R. F.;

Extreme energetic particle decreases near geostationary orbit - A manifestation of current diversion within the inner plasma sheet

NASA Technical Reports Server (NTRS)

Baker, D. N.; Mcpherron, R. L.

1990-01-01

A qualitative model of magnetic field reconfiguration as might result from neutral line formation in the central plasma sheet late in a substorm growth phase is considered. It is suggested that magnetic reconnection probably begins before the substorm expansion phase and that cross-tail current is enhanced across the plasma sheet both earthward and tailward of a limited region near the neutral line. Such an enhanced cross-tail current earthward of the original X line region may contribute to thinning the plasma sheet substantially, and this would in turn affect the drift currents in that location, thus enhancing the current even closer toward the earth. In this way a redistribution and progressive diversion of normal cross-tail current throughout much of the inner portion of the plasma sheet could occur. The resulting intensified current, localized at the inner edge of the plasma sheet, would lead to a very thin plasma confinement region. This would explain the very taillike field and extreme particle dropouts often seen late in substorm growth phases.

ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and Its Implication to the Cross-Polar Cap Pedersen Currents

NASA Technical Reports Server (NTRS)

Le, Guan; Slavin, J. A.; Strangeway, Robert

2011-01-01

In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and its Implication to the Cross-Polar Cap Pedersen Currents

NASA Technical Reports Server (NTRS)

Le, Guan; Slavin, J. A.; Strangeway, Robert

2010-01-01

In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar windmagnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of approximately 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

Currents and Associated Electron Scattering and Bouncing Near the Diffusion Region at Earth's Magnetopause

NASA Technical Reports Server (NTRS)

Lavraud, B.; Zhang, Y. C.; Vernisse, Y.; Gershman, D. J.; Dorelli, J.; Cassak, P. A.; Dargent, J.; Pollock, C.; Giles, B.; Aunai, N.;

Multi-region relaxed magnetohydrodynamics in plasmas with slowly changing boundaries -- Resonant response of a plasma slab

DOE PAGES

Dewar, R. L.; Hudson, S. R.; Bhattacharjee, A.; ...

2017-04-03

The adiabatic limit of a recently proposed dynamical extension of Taylor relaxation, multi-region relaxed magnetohydrodynamics (MRxMHD), is summarized, with special attention to the appropriate definition of a relative magnetic helicity. The formalism is illustrated using a simple two-region, sheared-magnetic-field model similar to the Hahm-Kulsrud-Taylor (HKT) rippled-boundary slab model. In MRxMHD, a linear Grad-Shafranov equation applies, even at finite ripple amplitude. The adiabatic switching on of boundary ripple excites a shielding current sheet opposing reconnection at a resonant surface. The perturbed magnetic field as a function of ripple amplitude is calculated by invoking the conservation of magnetic helicity in the twomore » regions separated by the current sheet. Here, at low ripple amplitude, "half islands" appear on each side of the current sheet, locking the rotational transform at the resonant value. Beyond a critical amplitude, these islands disappear and the rotational transform develops a discontinuity across the current sheet. Published by AIP Publishing.« less

Multi-region relaxed magnetohydrodynamics in plasmas with slowly changing boundaries -- Resonant response of a plasma slab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dewar, R. L.; Hudson, S. R.; Bhattacharjee, A.

The adiabatic limit of a recently proposed dynamical extension of Taylor relaxation, multi-region relaxed magnetohydrodynamics (MRxMHD), is summarized, with special attention to the appropriate definition of a relative magnetic helicity. The formalism is illustrated using a simple two-region, sheared-magnetic-field model similar to the Hahm-Kulsrud-Taylor (HKT) rippled-boundary slab model. In MRxMHD, a linear Grad-Shafranov equation applies, even at finite ripple amplitude. The adiabatic switching on of boundary ripple excites a shielding current sheet opposing reconnection at a resonant surface. The perturbed magnetic field as a function of ripple amplitude is calculated by invoking the conservation of magnetic helicity in the twomore » regions separated by the current sheet. Here, at low ripple amplitude, "half islands" appear on each side of the current sheet, locking the rotational transform at the resonant value. Beyond a critical amplitude, these islands disappear and the rotational transform develops a discontinuity across the current sheet. Published by AIP Publishing.« less

Influence of the magnetic field profile on ITER conductor testing

NASA Astrophysics Data System (ADS)

Nijhuis, A.; Ilyin, Y.; ten Kate, H. H. J.

2006-08-01

We performed simulations with the numerical CUDI-CICC code on a typical short ITER (International Thermonuclear Experimental Reactor) conductor test sample of dual leg configuration, as usually tested in the SULTAN test facility, and made a comparison with the new EFDA-Dipole test facility offering a larger applied DC field region. The new EFDA-Dipole test facility, designed for short sample testing of conductors for ITER, has a homogeneous high field region of 1.2 m, while in the SULTAN facility this region is three times shorter. The inevitable non-uniformity of the current distribution in the cable, introduced by the joints at both ends, has a degrading effect on voltage-current (VI) and voltage-temperature (VT) characteristics, particularly for these short samples. This can easily result in an underestimation or overestimation of the actual conductor performance. A longer applied DC high field region along a conductor suppresses the current non-uniformity by increasing the overall longitudinal cable electric field when reaching the current sharing mode. The numerical interpretation study presented here gives a quantitative analysis for a relevant practical case of a test of a short sample poloidal field coil insert (PFCI) conductor in SULTAN. The simulation includes the results of current distribution analysis from self-field measurements with Hall sensor arrays, current sharing measurements and inter-petal resistance measurements. The outcome of the simulations confirms that the current uniformity improves with a longer high field region but the 'measured' VI transition is barely affected, though the local peak voltages become somewhat suppressed. It appears that the location of the high field region and voltage taps has practically no influence on the VI curve as long as the transverse voltage components are adequately cancelled. In particular, for a thin conduit wall, the voltage taps should be connected to the conduit in the form of an (open) azimuthally soldered wire, averaging the transverse conduit surface potentials initiated in the joints.

The auroral current circuit and field-aligned currents observed by FAST

NASA Astrophysics Data System (ADS)

Elphic, R. C.; Bonnell, J. W.; Strangeway, R. J.; Kepko, L.; Ergun, R. E.; McFadden, J. P.; Carlson, C. W.; Peria, W.; Cattell, C. A.; Klumpar, D.; Shelley, E.; Peterson, W.; Moebius, E.; Kistler, L.; Pfaff, R.

FAST observes signatures of small-scale downward-going current at the edges of the inverted-V regions where the primary (auroral) electrons are found. In the winter pre-midnight auroral zone these downward currents are carried by upward flowing low- and medium-energy (up to several keV) electron beams. FAST instrumentation shows agreement between the current densities inferred from both the electron distributions and gradients in the magnetic field. FAST data taken near apogee (˜4000-km altitude) commonly show downward current magnetic field deflections consistent with the observed upward flux of ˜109 electrons cm-2 s-1, or current densities of several µA m-2. The electron, field-aligned current and electric field signatures indicate the downward currents may be associated with “black aurora” and auroral ionospheric cavities. The field-aligned voltage-current relationship in the downward current region is nonlinear.

State diagram of magnetostatic coupling phase-locked spin-torque oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Mengwei; Wang, Longze; Wei, Dan, E-mail: weidan@mail.tsinghua.edu.cn

2015-05-07

The state diagram of magnetostatic coupling phase-locked spin torque oscillator (STO) with perpendicular reference layer and planar field generation layer (FGL) is studied by the macrospin model and the micromagnetic model. The state diagrams of current densities are calculated under various external fields. The simulation shows that there are two phase-lock current density regions. In the phase-locked STOs in low current region I, the spin configuration of FGL is uniform; in high current region II, the spin configuration of FGL is highly nonuniform. In addition, the results with different STOs separation L{sub s} are compared, and the coupling between twomore » STOs is largely decreased when L{sub s} is increased from 40 nm to 60 nm.« less

Statistical survey of day-side magnetospheric current flow using Cluster observations: magnetopause

NASA Astrophysics Data System (ADS)

Liebert, Evelyn; Nabert, Christian; Perschke, Christopher; Fornaçon, Karl-Heinz; Glassmeier, Karl-Heinz

2017-05-01

We present a statistical survey of current structures observed by the Cluster spacecraft at high-latitude day-side magnetopause encounters in the close vicinity of the polar cusps. Making use of the curlometer technique and the fluxgate magnetometer data, we calculate the 3-D current densities and investigate the magnetopause current direction, location, and magnitude during varying solar wind conditions. We find that the orientation of the day-side current structures is in accordance with existing magnetopause current models. Based on the ambient plasma properties, we distinguish five different transition regions at the magnetopause surface and observe distinctive current properties for each region. Additionally, we find that the location of currents varies with respect to the onset of the changes in the plasma environment during magnetopause crossings.

The interhemispheric and F region dynamo currents revisited with the Swarm constellation

NASA Astrophysics Data System (ADS)

Lühr, Hermann; Kervalishvili, Guram; Michaelis, Ingo; Rauberg, Jan; Ritter, Patricia; Park, Jaeheung; Merayo, Jose M. G.; Brauer, Peter

2015-05-01

Based on magnetic field data sampled by the Swarm satellite constellation it is possible for the first time to determine uniquely F region currents at low latitudes. Initial results are presented from the first 200 days of formation flight (17 April to 5 November 2014). Detailed results have been obtained for interhemispheric field-aligned currents connecting the solar quiet day magnetic variation (Sq) current systems in the two hemispheres. We obtain prominent currents from the Southern (winter) Hemisphere to the Northern around noon. Weaker currents in opposite direction are observed during morning and evening hours. Furthermore, we could confirm the existence of vertical currents above the dip equator, downward around noon and upward around sunset. For both current systems we present and discuss longitudinal variations.

Relationship between field-aligned currents and inverted-V parallel potential drops observed at midaltitudes

NASA Astrophysics Data System (ADS)

Sakanoi, T.; Fukunishi, H.; Mukai, T.

1995-10-01

The inverted-V field-aligned acceleration region existing in the altitude range of several thousand kilometers plays an essential role for the magnetosphere-ionosphere coupling system. The adiabatic plasma theory predicts a linear relationship between field-aligned current density (J∥) and parallel potential drop (Φ∥), that is, J∥=KΦ∥, where K is the field-aligned conductance. We examined this relationship using the charged particle and magnetic field data obtained from the Akebono (Exos D) satellite. The potential drop above the satellite was derived from the peak energy of downward electrons, while the potential drop below the satellite was derived from two different methods: the peak energy of upward ions and the energy-dependent widening of electron loss cone. On the other hand, field-aligned current densities in the inverted-V region were estimated from the Akebono magnetometer data. Using these potential drops and field-aligned current densities, we estimated the linear field-aligned conductance KJΦ. Further, we obtained the corrected field-aligned conductance KCJΦ by applying the full Knight's formula to the current-voltage relationship. We also independently estimated the field-aligned conductance KTN from the number density and the thermal temperature of magnetospheric source electrons which were obtained by fitting accelerated Maxwellian functions for precipitating electrons. The results are summarized as follows: (1) The latitudinal dependence of parallel potential drops is characterized by a narrow V-shaped structure with a width of 0.4°-1.0°. (2) Although the inverted-V potential region exactly corresponds to the upward field aligned current region, the latitudinal dependence of upward current intensity is an inverted-U shape rather than an inverted-V shape. Thus it is suggested that the field-aligned conductance KCJΦ changes with a V-shaped latitudinal dependence. In many cases, KCJΦ values at the edge of the inverted-V region are about 5-10 times larger than those at the center. (3) By comparing KCJΦ with KTN, KCJΦ is found to be about 2-20 times larger than KTN. These results suggest that low-energy electrons such as trapped electrons, secondary and back-scattered electrons, and ionospheric electrons significantly contribute to upward field-aligned currents in the inverted-V region. It is therefore inferred that non adiabatic pitch angle scattering processes play an important role in the inverted-V region. .

Observations of high-plasma density region in the inner coma of 67P/Churyumov-Gerasimenko during early activity

NASA Astrophysics Data System (ADS)

Yang, Lei; Paulsson, J. J. P.; Wedlund, C. Simon; Odelstad, E.; Edberg, N. J. T.; Koenders, C.; Eriksson, A. I.; Miloch, W. J.

2016-11-01

In 2014 September, as Rosetta transitioned to close bound orbits at 30 km from comet 67P/Churyumov-Gerasimenko, the Rosetta Plasma Consortium Langmuir probe (RPC-LAP) data showed large systematic fluctuations in both the spacecraft potential and the collected currents. We analyse the potential bias sweeps from RPC-LAP, from which we extract three sets of parameters: (1) knee potential, that we relate to the spacecraft potential, (2) the ion attraction current, which is composed of the photoelectron emission current from the probe as well as contributions from local ions, secondary emission, and low-energy electrons, and (3) an electron current whose variation is, in turn, an estimate of the electron density variation. We study the evolution of these parameters between 4 and 3.2 au in heliocentric and cometocentric frames. We find on September 9 a transition into a high-density plasma region characterized by increased knee potential fluctuations and plasma currents to the probe. In conjunction with previous studies, the early cometary plasma can be seen as composed of two regions: an outer region characterized by solar wind plasma, and small quantities of pick-up ions, and an inner region with enhanced plasma densities. This conclusion is in agreement with other RPC instruments such as RPC-MAG, RPC-IES and RPC-ICA, and numerical simulations.

Hydrodynamics of spatially inhomogeneous real membranes

NASA Astrophysics Data System (ADS)

Kirii, V. A.; Shelistov, V. S.; Demekhin, E. A.

2017-07-01

Electrokinetic processes in the vicinity of inhomogeneous ion-selective surfaces (electrodes, membranes, microchannels, and nanochannels) consisting of alternating conducting and nonconducting regions in the presence of a normal-to-surface electric current are numerically studied. An increase in the electric current density is observed in the case of some particular alternation of conducting and nonconducting regions of the surface. The current-voltage characteristics of homogeneous and inhomogeneous electric membranes are found to be in qualitative agreement. Various physical phenomena leading to the emergence of a supercritical current in homogeneous and inhomogeneous membranes are detected.

Extreme energetic particle decreases near geostationary orbit - A manifestation of current diversion within the inner plasma sheet

NASA Technical Reports Server (NTRS)

Baker, D. N.; Mcpherron, R. L.

1990-01-01

A qualitative model of cross-tail current flow is considered. It is suggested that when magnetic reconnection begins, the current effectively flows across the plasma sheet both earthward and tailward of the disruption region near the neutral line. It is shown that an enhanced cross-tail current earthward of this region would thin the plasma sheet substantially due to the magnetic pinch effect. The results explain the very taillike field and extreme particle dropouts often seen late in substorm growth phases.

The Substorm Current Wedge: Further Insights from MHD Simulations

NASA Technical Reports Server (NTRS)

Birn, J.; Hesse, M.

2015-01-01

Using a recent magnetohydrodynamic simulation of magnetotail dynamics, we further investigate the buildup and evolution of the substorm current wedge (SCW), resulting from flow bursts generated by near-tail reconnection. Each flow burst generates an individual current wedge, which includes the reduction of cross-tail current and the diversion to region 1 (R1)-type field-aligned currents (earthward on the dawn and tailward on the duskside), connecting the tail with the ionosphere. Multiple flow bursts generate initially multiple SCW patterns, which at later times combine to a wider single SCW pattern. The standard SCWmodel is modified by the addition of several current loops, related to particular magnetic field changes: the increase of Bz in a local equatorial region (dipolarization), the decrease of |Bx| away from the equator (current disruption), and increases in |By| resulting from azimuthally deflected flows. The associated loop currents are found to be of similar magnitude, 0.1-0.3 MA. The combined effect requires the addition of region 2 (R2)-type currents closing in the near tail through dawnward currents but also connecting radially with the R1 currents. The current closure at the inner boundary, taken as a crude proxy of an idealized ionosphere, demonstrates westward currents as postulated in the original SCW picture as well as North-South currents connecting R1- and R2-type currents, which were larger than the westward currents by a factor of almost 2. However, this result should be applied with caution to the ionosphere because of our neglect of finite resistance and Hall effects.

Electrodynamic parameters in the nighttime sector during auroral substorms

NASA Technical Reports Server (NTRS)

Fujii, R.; Hoffman, R. A.; Anderson, P. C.; Craven, J. D.; Sugiura, M.; Frank, L. A.; Maynard, N. C.

1994-01-01

The characteristics of the large-scale electrodynamic parameters, field-aligned currents (FACs), electric fields, and electron precipitation, which are associated with auroral substorm events in the nighttime sector, have been obtained through a unique analysis which places the ionospheric measurements of these parameters into the context of a generic substorm determined from global auroral images. A generic bulge-type auroral emission region has been deduced from auroral images taken by the Dynamics Explorer 1 (DE 1) satellite during a number of isolated substorms, and the form has been divided into six sectors, based on the peculiar emission characteristics in each sector: west of bulge, surge horn, surge, middle surge, eastern bulge, and east of bulge. By comparing the location of passes of the Dynamics Explorer 2 (DE 2) satellite to the simultaneously obtained auroral images, each pass is placed onto the generic aurora. The organization of DE 2 data in this way has systematically clarified peculiar characteristics in the electrodynamic parameters. An upward net current mainly appears in the surge, with little net current in the surge horn and the west of bulge. The downward net current is distributed over wide longitudinal regions from the eastern bulge to the east of bulge. Near the poleward boundary of the expanding auroral bulge, a pair of oppositely directed FAC sheets is observed, with the downward FAC on the poleward side. This downward FAC and most of the upward FAC in the surge and the middle surge are assoc iated with narrow, intense antisunwqard convection, corresponding to an equatorward directed spikelike electric field. This pair of currents decreases in amplitude and latitudinal width toward dusk in the surge and the west of bulge, and the region 1 and 2 FACs become embedded in the sunward convection region. The upward FAC region associated with the spikelike field on the poleward edge of the bulge coincides well with intense electron precipitation and aurora appearing in this western and poleward protion of the bulge. The convection reversal is sharp in the west of bulge and surge horn sectors, and near the high-latitude boundary of the upward region 1, with a near stagnation region often extending over a large interval of latitude. In the eastern bulge and east of bulge sectors, the region 1 and 2 FACs are located in the sunward convection region, while a spikelike electric field occasionally appears poleward of the aurora but usually not associated with a pair of FAC sheets. In the eastern bulge, magnetic field data show complicated FAC distributions which correspond to current segments and filamentary currents.

Two-fluid dynamo relaxation and momentum transport induced by CHI on HIST

NASA Astrophysics Data System (ADS)

Nagata, Masayoshi; Hirono, Hidetoshi; Hanao, Takafumi; Hyobu, Takahiro; Ito, Kengo; Matsumoto, Keisuke; Nakayama, Takashi; Oki, Nobuharu; Kikuchi, Yusuke; Fukumoto, Naoyuki

2013-10-01

Non-inductive current drive by using Multi-pulsing coaxial helicity injection was studied on HIST. In the double-pulsing CHI experiment, we have examined two-fluid effects by reversing polarity of the bias poloidal coil current. In the ST magnetic configurations with the right-handed magnetic field (positive CHI), there are a diamagnetic structure in the open flux column region and a paramagnetic structure in the closed flux region. It is naturally understood that the direction of the poloidal magnetic field (toroidal current) is reversed in reversing the polarity of the bias flux from positive to negative. However, the poloidal current is surprisingly reversed in reversing the magnetic helicity polarity. The direction of the poloidal current is opposite in the each region. The toroidal flow is reversed, but a shear profile of the poloidal flow is not changed significantly. In this configuration, the diamagnetic structure appears in the closed flux region. Thus, not only Jt×Bp but also Jp×Bt force contributes on pressure balance leading to a higher beta. We are studying a more general helicity conservation that constrains the interaction between flows and magnetic fields and momentum transport in the two-fluid framework.

Current status of Crimean-Congo haemorrhagic fever in the World Health Organization Eastern Mediterranean Region: issues, challenges, and future directions.

PubMed

Al-Abri, Seif S; Abaidani, Idris Al; Fazlalipour, Mehdi; Mostafavi, Ehsan; Leblebicioglu, Hakan; Pshenichnaya, Natalia; Memish, Ziad A; Hewson, Roger; Petersen, Eskild; Mala, Peter; Nhu Nguyen, Tran Minh; Rahman Malik, Mamunur; Formenty, Pierre; Jeffries, Rosanna

2017-05-01

Crimean-Congo haemorrhagic fever (CCHF) is the most widespread, tick-borne viral disease affecting humans. The disease is endemic in many regions, such as Africa, Asia, Eastern and Southern Europe, and Central Asia. Recently, the incidence of CCHF has increased rapidly in the countries of the World Health Organization Eastern Mediterranean Region (WHO EMR), with sporadic human cases and outbreaks of CCHF being reported from a number of countries in the region. Despite the rapidly growing incidence of the disease, there are currently no accurate data on the burden of the disease in the region due to the different surveillance systems used for CCHF in these countries. In an effort to increase our understanding of the epidemiology and risk factors for the transmission of the CCHF virus (CCHFV; a Nairovirus of the family Bunyaviridae) in the WHO EMR, and to identify the current knowledge gaps that are hindering effective control interventions, a sub-regional meeting was organized in Muscat, Oman, from December 7 to 9, 2015. This article summarizes the current knowledge of the disease in the region, identifies the knowledge gaps that present challenges for the prevention and control of CCHFV, and details a strategic framework for research and development activities that would be necessary to curb the ongoing and new threats posed by CCHFV. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Field-aligned currents in the undisturbed polar ionosphere

NASA Astrophysics Data System (ADS)

Kroehl, H. W.

1989-09-01

Field-aligned currents, FAC's, which couple ionospheric currents at high latitudes with magnetospheric currents have become an essential cornerstone to our understanding of plasma dynamics in the polar region and in the earth's magnetosphere. Initial investigators of polar electrodynamics including the aurora were unable to distinguish between the ground magnetic signatures of a purely two-dimensional current and those from a three-dimensional current system, ergo many scientists ignored the possible existence of these vertical currents. However, data from magnetometers and electrostatic analyzers flown on low-altitude, polar-orbiting satellites proved beyond any reasonable doubt that field-aligned currents existed, and that different ionospheric regions were coupled to different magnetospheric regions which were dominated by different electrodynamic processes, e.g., magnetospheric convection electric fields, magnetospheric substorms and parallel electric fields. Therefore, to define the “undisturbed” polar ionosphere and its structure and dynamics, one needs to consider these electrodynamic processes, to select times for analysis when they are not strongly active and to remember that the polar ionosphere may be disturbed when the equatorial, mid-latitude and sub-auroral ionospheres are not. In this paper we will define the principle high-latitude current systems, describe the effects of FAC's associated with these systems, review techniques which would minimize these effects and present our description of the “undisturbed” polar ionosphere.

An iterative model for the steady state current distribution in oxide-confined vertical-cavity surface-emitting lasers (VCSELs)

NASA Astrophysics Data System (ADS)

Chuang, Hsueh-Hua

The purpose of this dissertation is to develop an iterative model for the analysis of the current distribution in vertical-cavity surface-emitting lasers (VCSELs) using a circuit network modeling approach. This iterative model divides the VCSEL structure into numerous annular elements and uses a circuit network consisting of resistors and diodes. The measured sheet resistance of the p-distributed Bragg reflector (DBR), the measured sheet resistance of the layers under the oxide layer, and two empirical adjustable parameters are used as inputs to the iterative model to determine the resistance of each resistor. The two empirical values are related to the anisotropy of the resistivity of the p-DBR structure. The spontaneous current, stimulated current, and surface recombination current are accounted for by the diodes. The lateral carrier transport in the quantum well region is analyzed using drift and diffusion currents. The optical gain is calculated as a function of wavelength and carrier density from fundamental principles. The predicted threshold current densities for these VCSELs match the experimentally measured current densities over the wavelength range of 0.83 mum to 0.86 mum with an error of less than 5%. This model includes the effects of the resistance of the p-DBR mirrors, the oxide current-confining layer and spatial hole burning. Our model shows that higher sheet resistance under the oxide layer reduces the threshold current, but also reduces the current range over which single transverse mode operation occurs. The spatial hole burning profile depends on the lateral drift and diffusion of carriers in the quantum wells but is dominated by the voltage drop across the p-DBR region. To my knowledge, for the first time, the drift current and the diffusion current are treated separately. Previous work uses an ambipolar approach, which underestimates the total charge transferred in the quantum well region, especially under the oxide region. However, the total result of the drift current and the diffusion current is less significant than the Ohmic current, especially in the cavity region. This simple iterative model is applied to commercially available oxide-confined VCSELs. The simulation results show excellent agreement with experimentally measured voltage-current curves (within 3.7% for a 10 mum and within 4% for a 5 mum diameter VCSEL) and light-current curves (within 2% for a 10 mum and within 9% for a 5 mum diameter VCSEL) curves and provides insight into the detailed distributions of current and voltage within a VCSEL. This difference between the theoretically calculated results and the measured results is less than the variation shown in the data sheets for production VCSELs.

A comparison of photospheric electric current and ultraviolet and X-ray emission in a solar active region

NASA Astrophysics Data System (ADS)

Haisch, B. M.; Bruner, M. E.; Hagyard, M. J.; Bonnet, R. M.

1986-01-01

This paper presents an extensive set of coordinated observations of a solar active region, taking into account spectroheliograms obtained with the aid of the Solar Maximum Mission (SMM) Ultraviolet Spectrometer Polarimeter (UVSP) instrument, SMM soft X-ray polychromator (XRP) raster maps, and high spatial resolution ultraviolet images of the sun in Lyman-alpha and in the 1600 A continuum. These data span together the upper solar atmosphere from the temperature minimum to the corona. The data are compared to maps of the inferred photospheric electric current derived from the Marshall Space Flight Center (MSFC) vector magnetograph observations. Some empirical correlation is found between regions of inferred electric current density and the brightest features in the ultraviolet continuum and to a lesser extent those seen in Lyman-alpha within an active region.

Reduced Sodium Current in the Lateral Ventricular Wall Induces Inferolateral J-Waves.

PubMed

Meijborg, Veronique M F; Potse, Mark; Conrath, Chantal E; Belterman, Charly N W; De Bakker, Jacques M T; Coronel, Ruben

2016-01-01

J-waves in inferolateral leads are associated with a higher risk for idiopathic ventricular fibrillation. We aimed to test potential mechanisms (depolarization or repolarization dependent) responsible for inferolateral J-waves. We hypothesized that inferolateral J-waves can be caused by regional delayed activation of myocardium that is activated late during normal conditions. Computer simulations were performed to evaluate how J-point elevation is influenced by reducing sodium current conductivity (GNa), increasing transient outward current conductivity (Gto), or cellular uncoupling in three predefined ventricular regions (lateral, anterior, or septal). Two pig hearts were Langendorff-perfused with selective perfusion with a sodium channel blocker of lateral or anterior/septal regions. Volume-conducted pseudo-electrocardiograms (ECG) were recorded to detect the presence of J-waves. Epicardial unipolar electrograms were simultaneously recorded to obtain activation times (AT). Simulation data showed that conduction slowing, caused by reduced sodium current, in lateral, but not in other regions induced inferolateral J-waves. An increase in transient outward potassium current or cellular uncoupling in the lateral zone elicited slight J-point elevations which did not meet J-wave criteria. Additional conduction slowing in the entire heart attenuated J-waves and J-point elevations on the ECG, because of masking by the QRS. Experimental data confirmed that conduction slowing attributed to sodium channel blockade in the left lateral but not in the anterior/septal ventricular region induced inferolateral J-waves. J-waves coincided with the delayed activation. Reduced sodium current in the left lateral ventricular myocardium can cause inferolateral J-waves on the ECG.

Anaglyph, South America

NASA Technical Reports Server (NTRS)

2003-01-01

This anaglyph (stereoscopic view) of South America was generated with data from the Shuttle Radar Topography Mission (SRTM). It is best viewed at or near full resolution with anaglyph glasses. For this broad view the resolution of the data was first reduced to 30 arcseconds (about 928 meters north-south but variable east-west), matching the best previously existing global digital topographic data set called GTOPO30. The data were then resampled to a Mercator projection with approximately square pixels (about one kilometer, or 0.6 miles, on each side). Even at this decreased resolution the variety of landforms comprising the South American continent is readily apparent.

Topographic relief in South America is dominated by the Andes Mountains, which extend all along the Pacific Coast. These mountains are created primarily by the convergence of the Nazca and South American tectonic plates. The Nazca Plate, which underlies the eastern Pacific Ocean, slides under western South America resulting in crustal thickening, uplift, and volcanism. Another zone of plate convergence occurs along the northwestern coast of South America where the Caribbean Plate also slides under the South American Plate and forms the northeastern extension of the Andes Mountains.

East of the Andes, much of northern South America drains into the Amazon River, the world's largest river in terms of both watershed area and flow volume. Topographic relief is very low in much of the Amazon Basin but SRTM data provide an excellent detailed look at the basin's three-dimensional drainage pattern, including the geologic structural trough (syncline) that hosts the eastern river channel.

North of the Amazon, the Guiana Highlands commonly stand in sharp contrast to the surrounding lowlands, indeed hosting the world's tallest waterfall, Angel Falls (979 meters or 3212 feet). Folded and fractured bedrock structures are distinctive in the topographic pattern.

South of the Amazon, the Brazilian Highlands show a mix of landforms, including some broad areas of consistent topographic patterns that indicate the occurrence of simple erosional processes acting upon fairly uniform bedrock. Very smooth plateaus here are remnants of landforms most likely developed under geologic and environmental conditions much different than those present today. Fractures paralleling the coast are likely related to the opening of the Atlantic Ocean as South America drifted away from Africa, starting about 130 million years ago.

To the southwest, broad lowlands host the Gran Chaco and Pampas regions. The depositional Gran Chaco drainages run almost exclusively from west to east from the Andes Mountains to the western edge of the Brazilian Highlands as a result of the much greater sediment supply from the Andes. Geologic processes on the Pampas are much more diverse, with stream erosion, stream deposition, subsidence, and wind processes all evident, even at the one-kilometer resolution shown here.

Further south, Patagonia also displays these geologic processes plus more prominent volcanic features, including bumpy mesas, which are lava plateaus with small (and some large) volcanic cones. At its southern tip, of South America breaks into islands that include Tierra del Fuego and the Straits of Magellan.

This anaglyph was created by deriving a shaded relief image from the SRTM data, draping it back over the SRTM elevation model, and then generating two differing perspectives, one for each eye. Illumination is from the north (top). When viewed through special glasses, the anaglyph is a vertically exaggerated view of the Earth's surface in its full three dimensions. Anaglyph glasses cover the left eye with a red filter and cover the right eye with a blue filter.

Elevation data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D.C.

Location: 15 degrees North to 60 degrees South latitude, 30 to 90 degrees West longitude Orientation: North toward the top, Mercator projection Image Data: shaded SRTM elevation model Original Data Resolution: SRTM 1 arcsecond (about 30 meters or 98 feet) Date Acquired: February 2000

South America, Shaded Relief and Colored Height

NASA Technical Reports Server (NTRS)

2003-01-01

This image of South America was generated with data from the Shuttle Radar Topography Mission (SRTM). For this broad view the resolution of the data was first reduced to 30 arcseconds (about 928 meters north-south but variable east-west), matching the best previously existing global digital topographic data set called GTOPO30. The data were then resampled to a Mercator projection with approximately square pixels (about one kilometer, or 0.6 miles, on each side). Even at this decreased resolution the variety of landforms comprising the South American continent is readily apparent.

Topographic relief in South America is dominated by the Andes Mountains, which extend all along the Pacific Coast. These mountains are created primarily by the convergence of the Nazca and South American tectonic plates. The Nazca Plate, which underlies the eastern Pacific Ocean, slides under western South America resulting in crustal thickening, uplift, and volcanism. Another zone of plate convergence occurs along the northwestern coast of South America where the Caribbean Plate also slides under the South American Plate and forms the northeastern extension of the Andes Mountains.

East of the Andes, much of northern South America drains into the Amazon River, the world's largest river in terms of both watershed area and flow volume. Topographic relief is very low in much of the Amazon Basin but SRTM data provide an excellent detailed look at the basin's three-dimensional drainage pattern, including the geologic structural trough (syncline) that hosts the eastern river channel.

North of the Amazon, the Guiana Highlands commonly stand in sharp contrast to the surrounding lowlands, indeed hosting the world's tallest waterfall, Angel Falls (979 meters or 3212 feet). Folded and fractured bedrock structures are distinctive in the topographic pattern.

South of the Amazon, the Brazilian Highlands show a mix of landforms, including some broad areas of consistent topographic patterns that indicate the occurrence of simple erosional processes acting upon fairly uniform bedrock. Very smooth plateaus here are remnants of landforms most likely developed under geologic and environmental conditions much different than those present today. Fractures paralleling the coast are likely related to the opening of the Atlantic Ocean as South America drifted away from Africa, starting about 130 million years ago.

To the southwest, broad lowlands host the Gran Chaco and Pampas regions. The depositional Gran Chaco drainages run almost exclusively from west to east from the Andes Mountains to the western edge of the Brazilian Highlands as a result of the much greater sediment supply from the Andes. Geologic processes on the Pampas are much more diverse, with stream erosion, stream deposition, subsidence, and wind processes all evident, even at the one-kilometer resolution shown here.

Further south, Patagonia also displays these geologic processes plus more prominent volcanic features, including bumpy mesas, which are lava plateaus with small (and some large) volcanic cones. At its southern tip South America breaks into islands that include Tierra del Fuego and the Straits of Magellan.

Two visualization methods were combined to produce the image: shading and color coding of topographic height. The shade image was derived by computing topographic slope in the northwest-southeast direction, so that northwest slopes appear bright and southeast slopes appear dark. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and tan, to white at the highest elevations.

Elevation data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D.C.

Location: 15 degrees North to 60 degrees South latitude, 30 to 90 degrees West longitude Orientation: North toward the top, Mercator projection Image Data: shaded and colored SRTM elevation model Original Data Resolution: SRTM 1 arcsecond (about 30 meters or 98 feet) Date Acquired: February 2000

Modelling the effect of electrode displacement on transcranial direct current stimulation (tDCS)

NASA Astrophysics Data System (ADS)

Ramaraju, Sriharsha; Roula, Mohammed A.; McCarthy, Peter W.

2018-02-01

Objective. Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that delivers a low-intensity, direct current to cortical areas with the purpose of modulating underlying brain activity. Recent studies have reported inconsistencies in tDCS outcomes. The underlying assumption of many tDCS studies has been that replication of electrode montage equates to replicating stimulation conditions. It is possible however that anatomical difference between subjects, as well as inherent inaccuracies in montage placement, could affect current flow to targeted areas. The hypothesis that stimulation of a defined brain region will be stable under small displacements was tested. Approach. Initially, we compared the total simulated current flowing through ten specific brain areas for four commonly used tDCS montages: F3-Fp2, C3-Fp2, Fp1-F4, and P3-P4 using the software tool COMETS. The effect of a slight (~1 cm in each of four directions) anode displacement on the simulated regional current density for each of the four tDCS montages was then determined. Current flow was calculated and compared through ten segmented brain areas to determine the effect of montage type and displacement. The regional currents, as well as the localised current densities, were compared with the original electrode location, for each of these new positions. Main results. Recommendations for montages that maximise stimulation current for the ten brain regions are considered. We noted that the extent to which stimulation is affected by electrode displacement varies depending on both area and montage type. The F3-Fp2 montage was found to be the least stable with up to 38% change in average current density in the left frontal lobe while the Fp1-F4 montage was found to the most stable exhibiting only 1% change when electrodes were displaced. Significance. These results indicate that even relatively small changes in stimulation electrode placement appear to result in surprisingly large changes in current densities and distribution.

Cross-tail current, field-aligned current, and B(y)

NASA Technical Reports Server (NTRS)

Kaufmann, Richard L.; Lu, Chen; Larson, Douglas J.

1994-01-01

Orbits of individual charged particles were traced in a one-dimensional magnetic field model that included a uniform cross-tail component B(sub yo). The effects of B(sub yo) on the cross-tail current distribution j(sub y)(z), the average cross-tail drift velocity(nu(sub y)z), and the average pitch angle change(delta alpha) experienced during current sheet encounters were calculated. The addition of a B(sub yo) that exceeded several tenths of one nanotesla completely eliminated all resonance effects for odd-N orbits. An odd-N resonance involves ions that enter and exit the current sheet on the same side. Pitch angles of nearly all such ions changed substantially during a typical current sheet interaction, and there was no region of large cross-tail drift velocity in the presence of a modest B(sub yo). the addition of a very large B(sub yo) guide field in the direction that enhances the natural drift produces a large j(y) and small (Delta alpha) for ions with all energies. The addition of a modest B(sub yo) had less effect near even-N resonances. In this case, ions in a small energy range were found to undergo so little change in pitch angle that particles which originated in the ionosphere would pass through the current sheet and return to the conjugate ionosphere. Finally, the cross-tail drift of ions from regions dominated by stochastic orbits to regions dominated by either resonant or guiding center orbits was considered. The ion drift speed changed substantially during such transitions. The accompanying electrons obey the guiding center equations, so electron drift is more uniform. Any difference between gradients in the fluxes associated with electron and ion drifts requires the presence of a Birkeland current in order to maintain charge neutrality. This plasma sheet region therefore serves as a current generator. The analysis predicts that the resulting Birkeland current connects to the lowest altitude equatorial regions in which ions drift to or from a point at which stochastic orbits predominate. The proposed mechanism appears only in analyses that include non-guiding-center effects.

Reaction μ-+6Li-->3H+3H+νμ and the axial current form factor in the timelike region

NASA Astrophysics Data System (ADS)

Mintz, S. L.

1983-09-01

The differential muon-capture rate dΓdET is obtained for the reaction μ-+6Li-->3H+3H+νμ over the allowed range of ET, the tritium energy, for two assumptions concerning the behavior of FA, the axial current form factor, in the timelike region; analytic continuation from the spacelike region and mirror behavior, FA(q2, timelike)=FA(q2, spacelike). The values of dΓdET under these two assumptions are found to vary substantially in the timelike region as a function of the mass MA in the dipole fit to FA. Values of dΓdET are given for MA2=2mπ2, 4.95mπ2, and 8mπ2. NUCLEAR REACTIONS Muon capture 6Li(μ-, νμ)3H3H, Γ, dΓdET calculated for two assumptions concerning the axial current form factor behavior in timelike region.

Pediatric regional anesthesia: what is the current safety record?

PubMed

Polaner, David M; Drescher, Jessica

2011-07-01

The use of regional anesthetics, whether as adjuncts, primary anesthetics or postoperative analgesia, is increasingly common in pediatric practice. Data on safety remain limited because of the paucity of very large-scale prospective studies that are necessary to detect low incidence events, although several studies either have been published or have reported preliminary results. This paper will review the data on complications and risk in pediatric regional anesthesia. Information currently available suggests that regional blockade, when performed properly, carries a very low risk of morbidity and mortality in appropriately selected infants and children. © 2010 Blackwell Publishing Ltd.

A Combined Study of Photospheric Magnetic and Current Helicities and Subsurface Kinetic Helicities of Solar Active Regions during 2006-2013

NASA Astrophysics Data System (ADS)

Seligman, D.; Petrie, G. J. D.; Komm, R.

2014-11-01

We compare the average photospheric current helicity Hc , photospheric twist parameter α (a well-known proxy for the full relative magnetic helicity), and subsurface kinetic helicity Hk for 194 active regions observed between 2006-2013. We use 2440 Hinode photospheric vector magnetograms, and the corresponding subsurface fluid velocity data derived from GONG (2006-2012) and Helioseismic and Magnetic Imager (2010-2013) dopplergrams. We find a significant hemispheric bias in all three parameters. The subsurface kinetic helicity is preferentially positive in the southern hemisphere and negative in the northern hemisphere. The photospheric current helicity and the α parameter have the same bias for strong fields (|B| > 1000 G) and no significant bias for weak fields (100 G <|B| < 500 G). We find no significant region-by-region correlation between the subsurface kinetic helicity and either the strong-field current helicity or α. Subsurface fluid motions of a given handedness correspond to photospheric helicities of both signs in approximately equal numbers. However, common variations appear in annual averages of these quantities over all regions. Furthermore, in a subset of 77 regions, we find significant correlations between the temporal profiles of the subsurface and photospheric helicities. In these cases, the sign of the linear correlation coefficient matches the sign relationship between the helicities, indicating that the photospheric magnetic field twist is sensitive to the twisting motions below the surface.

Influence of clamping plate permeability and metal screen structures on three-dimensional magnetic field and eddy current loss in end region of a turbo-generator by numerical analysis

NASA Astrophysics Data System (ADS)

Likun, Wang; Weili, Li; Yi, Xue; Chunwei, Guan

2013-11-01

A significant problem of turbogenerators on complex end structures is overheating of local parts caused by end losses in the end region. Therefore, it is important to investigate the 3-D magnetic field and eddy current loss in the end. In end region of operating large turbogenerator at thermal power plants, magnetic leakage field distribution is complex. In this paper, a 3-D mathematical model used for the calculation of the electromagnetic field in the end region of large turbo-generators is given. The influence of spatial locations of end structures, the actual shape and material of end windings, clamping plate, and copper screen are considered. Adopting the time-step finite element (FE) method and taking the nonlinear characteristics of the core into consideration, a 3-D transient magnetic field is calculated. The objective of this paper is to investigate the influence of clamping plate permeability and metal screen structures on 3-D electromagnetic field distribution and eddy current loss in end region of a turbo-generator. To reduce the temperature of copper screen, a hollow metal screen is proposed. The eddy current loss, which is gained from the 3D transient magnetic field, is used as heat source for the thermal field of end region. The calculated temperatures are compared with test data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krauz, V. I., E-mail: krauz@nfi.kiae.ru; Mitrofanov, K. N.; Voitenko, D. A.

Results are presented from magnetic probe measurements in the pinching region formed during the compression of the plasma current sheath (PCS) in a discharge in deuterium at the KPF-4-Phoenix plasma focus facility. The fine structure (shock front-magnetic piston) of the PCS and its time evolution in the course of plasma compression toward the facility axis was studied by means of magnetic probes. It is shown that the fraction of the current transported into the axial region by the PCS does not exceed 65% of the total discharge current. The integral neutron yield Y{sub n} is well described by the formulamore » Y{sub n} ≈ (1.5–3) × 10{sup 10}I{sub p}{sup 4}, where I{sub p} (in MA) is the pinch current flowing in the region r ≤ 22 mm.« less

Temperature and electrolyte optimization of the α-hemolysin latch sensing zone for detection of base modification in double-stranded DNA.

PubMed

Johnson, Robert P; Fleming, Aaron M; Jin, Qian; Burrows, Cynthia J; White, Henry S

2014-08-19

The latch region of the wild-type protein pore α-hemolysin (α-HL) constitutes a sensing zone for individual abasic sites (and furan analogs) in double-stranded DNA (dsDNA). The presence of an abasic site or furan within a DNA duplex, electrophoretically captured in the α-HL vestibule and positioned at the latch region, can be detected based on the current blockage prior to duplex unzipping. We investigated variations in blockage current as a function of temperature (12-35°C) and KCl concentration (0.15-1.0 M) to understand the origin of the current signature and to optimize conditions for identifying the base modification. In 1 M KCl solution, substitution of a furan for a cytosine base in the latch region results in an ∼ 8 kJ mol(-1) decrease in the activation energy for ion transport through the protein pore. This corresponds to a readily measured ∼ 2 pA increase in current at room temperature. Optimal resolution for detecting the presence of a furan in the latch region is achieved at lower KCl concentrations, where the noise in the measured blockage current is significantly lower. The noise associated with the blockage current also depends on the stability of the duplex (as measured from the melting temperature), where a greater noise in the measured blockage current is observed for less stable duplexes. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Sequential soil transport and its influence on the spatial organisation of collective digging in leaf-cutting ants.

PubMed

Pielström, Steffen; Roces, Flavio

2013-01-01

The Chaco leaf-cutting ant Atta vollenweideri (Forel) inhabits large and deep subterranean nests composed of a large number of fungus and refuse chambers. The ants dispose of the excavated soil by forming small pellets that are carried to the surface. For ants in general, the organisation of underground soil transport during nest building remains completely unknown. In the laboratory, we investigated how soil pellets are formed and transported, and whether their occurrence influences the spatial organisation of collective digging. Similar to leaf transport, we discovered size matching between soil pellet mass and carrier mass. Workers observed while digging excavated pellets at a rate of 26 per hour. Each excavator deposited its pellets in an individual cluster, independently of the preferred deposition sites of other excavators. Soil pellets were transported sequentially over 2 m, and the transport involved up to 12 workers belonging to three functionally distinct groups: excavators, several short-distance carriers that dropped the collected pellets after a few centimetres, and long-distance, last carriers that reached the final deposition site. When initiating a new excavation, the proportion of long-distance carriers increased from 18% to 45% within the first five hours, and remained unchanged over more than 20 hours. Accumulated, freshly-excavated pellets significantly influenced the workers' decision where to start digging in a choice experiment. Thus, pellets temporarily accumulated as a result of their sequential transport provide cues that spatially organise collective nest excavation.

Access to Electric Light Is Associated with Shorter Sleep Duration in a Traditionally Hunter-Gatherer Community.

PubMed

de la Iglesia, Horacio O; Fernández-Duque, Eduardo; Golombek, Diego A; Lanza, Norberto; Duffy, Jeanne F; Czeisler, Charles A; Valeggia, Claudia R

2015-08-01

Access to electric light might have shifted the ancestral timing and duration of human sleep. To test this hypothesis, we studied two communities of the historically hunter-gatherer indigenous Toba/Qom in the Argentinean Chaco. These communities share the same ethnic and sociocultural background, but one has free access to electricity while the other relies exclusively on natural light. We fitted participants in each community with wrist activity data loggers to assess their sleep-wake cycles during one week in the summer and one week in the winter. During the summer, participants with access to electricity had a tendency to a shorter daily sleep bout (43 ± 21 min) than those living under natural light conditions. This difference was due to a later daily bedtime and sleep onset in the community with electricity, but a similar sleep offset and rise time in both communities. In the winter, participants without access to electricity slept longer (56 ± 17 min) than those with access to electricity, and this was also related to earlier bedtimes and sleep onsets than participants in the community with electricity. In both communities, daily sleep duration was longer during the winter than during the summer. Our field study supports the notion that access to inexpensive sources of artificial light and the ability to create artificially lit environments must have been key factors in reducing sleep in industrialized human societies. © 2015 The Author(s).

Access to Electric Light Is Associated with Shorter Sleep Duration in a Traditionally Hunter-Gatherer Community

PubMed Central

de la Iglesia, Horacio O.; Fernández-Duque, Eduardo; Golombek, Diego A.; Lanza, Norberto; Duffy, Jeanne F.; Czeisler, Charles A.; Valeggia, Claudia R.

2017-01-01

Access to electric light might have shifted the ancestral timing and duration of human sleep. To test this hypothesis, we studied two communities of the historically hunter-gatherer indigenous Toba/Qom in the Argentinean Chaco. These communities share the same ethnic and sociocultural background, but one has free access to electricity while the other relies exclusively on natural light. We fitted participants in each community with wrist activity data loggers to assess their sleep-wake cycles during one week in the summer and one week in the winter. During the summer, participants with access to electricity had a tendency to a shorter daily sleep bout (43 ± 21 min) than those living under natural light conditions. This difference was due to a later daily bedtime and sleep onset in the community with electricity, but a similar sleep offset and rise time in both communities. In the winter, participants without access to electricity slept longer (56 ± 17 min) than those with access to electricity, and this was also related to earlier bedtimes and sleep onsets than participants in the community with electricity. In both communities, daily sleep duration was longer during the winter than during the summer. Our field study supports the notion that access to inexpensive sources of artificial light and the ability to create artificially lit environments must have been key factors in reducing sleep in industrialized human societies. PMID:26092820

A History of NASA Remote Sensing Contributions to Archaeology

NASA Technical Reports Server (NTRS)

Giardino, Marco J.

2010-01-01

During its long history of developing and deploying remote sensing instruments, NASA has provided a scientific data that have benefitted a variety of scientific applications among them archaeology. Multispectral and hyperspectral instrument mounted on orbiting and suborbital platforms have provided new and important information for the discovery, delineation and analysis of archaeological sites worldwide. Since the early 1970s, several of the ten NASA centers have collaborated with archaeologists to refine and validate the use of active and passive remote sensing for archeological use. The Stennis Space Center (SSC), located in Mississippi USA has been the NASA leader in archeological research. Together with colleagues from Goddard Space Flight Center (GSFC), Marshall Space Flight Center (MSFC), and the Jet Propulsion Laboratory (JPL), SSC scientists have provided the archaeological community with useful images and sophisticated processing that have pushed the technological frontiers of archaeological research and applications. Successful projects include identifying prehistoric roads in Chaco canyon, identifying sites from the Lewis and Clark Corps of Discovery exploration and assessing prehistoric settlement patterns in southeast Louisiana. The Scientific Data Purchase (SDP) stimulated commercial companies to collect archaeological data. At present, NASA formally solicits "space archaeology" proposals through its Earth Science Directorate and continues to assist archaeologists and cultural resource managers in doing their work more efficiently and effectively. This paper focuses on passive remote sensing and does not consider the significant contributions made by NASA active sensors. Hyperspectral data offers new opportunities for future archeological discoveries.

Development of large-scale Birkeland currents determined from the Active Magnetosphere and Planetary Electrodynamics Response Experiment

DOE PAGES

Anderson, B. J.; Korth, H.; Waters, C. L.; ...

2014-05-07

The Active Magnetosphere and Planetary Electrodynamics Response Experiment uses magnetic field data from the Iridium constellation to derive the global Birkeland current distribution every 10 min. We examine cases in which the interplanetary magnetic field (IMF) rotated from northward to southward resulting in onsets of the Birkeland currents. Dayside Region 1/2 currents, totaling ~25% of the final current, appear within 20 min of the IMF southward turning and remain steady. In the onset of nightside currents occurs 40 to 70 min after the dayside currents appear. Afterwards, the currents intensify at dawn, dusk, and on the dayside, yielding a fullymore » formed Region 1/2 system ~30 min after the nightside onset. Our results imply that the dayside Birkeland currents are driven by magnetopause reconnection, and the remainder of the system forms as magnetospheric return flows start and progress sunward, ultimately closing the Dungey convection cycle.« less

Space Technology 5 (ST-5) Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents

NASA Technical Reports Server (NTRS)

Le, Guan

2010-01-01

Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total RI currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of approx. 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

Substorm Birkeland currents and Cowling channels in the ionosphere

NASA Astrophysics Data System (ADS)

Fujii, R.

2016-12-01

Field-aligned current (FAC) connects electromagnetically the ionosphere with the magnetosphere and plays important roles on dynamics and energetics in the magnetosphere and the ionosphere. In particular, connections between FACs in the ionosphere give important information on various current sources in the magnetosphere and the linkage between them, although the connection between FACs in the ionosphere does not straightforwardly give that in the magnetosphere. FACs in the ionosphere are closed to each other through ionospheric currents determined with the electric field and the Hall and Pedersen conductivities. The electric field and the conductivities are not independently distributed, but rather they are harmonized with each other spatially and temporarily in a physically consistent manner to give a certain FAC. In particular, the divergence of the Hall current due to the inhomogeneity of the Hall conductivity either flows in/out to the magnetosphere as a secondary FAC or accumulates excess charges that produce a secondary electric field. This electric field drives a current circuit connecting the Hall current with the Pedersen current; a Cowling channel current circuit. The FAC (the electric field) we observe is the sum of the primary and secondary FACs (electric fields). The talk will present characteristics of FACs and associated electric field and auroras during substorms, and the ionospheric current closures between the FACs. A statistical study has shown that the majority of region 1 currents are connected to their adjacent region 2 or region 0 currents, indicating the Pedersen current closure rather than the Hall current closure is dominant. On the other hand, the Pedersen currents associated with surge and substorm-related auroras often are connected to the Hall currents, forming a Cowling channel current circuit within the ionosphere.

REGIONAL VULNERABILITY ASSESSMENT OF THE MID-ATLANTIC REGION: EVALUATION OF INTEGRATION METHODS AND ASSESSMENTS RESULTS

EPA Science Inventory

This report describes methods for quantitative regional assessment developed by the Regional Vulnerability Assessment (ReVA) program. The goal of ReVA is to develop regional-scale assessments of the magnitude, extent, distribution, and uncertainty of current and anticipated envir...

Electric currents and voltage drops along auroral field lines

NASA Technical Reports Server (NTRS)

Stern, D. P.

1983-01-01

An assessment is presented of the current state of knowledge concerning Birkeland currents and the parallel electric field, with discussions focusing on the Birkeland primary region 1 sheets, the region 2 sheets which parallel them and appear to close in the partial ring current, the cusp currents (which may be correlated with the interplanetary B(y) component), and the Harang filament. The energy required by the parallel electric field and the associated particle acceleration processes appears to be derived from the Birkeland currents, for which evidence is adduced from particles, inverted V spectra, rising ion beams and expanded loss cones. Conics may on the other hand signify acceleration by electrostatic ion cyclotron waves associated with beams accelerated by the parallel electric field.

Region 9 RTOC Charter

EPA Pesticide Factsheets

U.S. EPA Pacific Southwest (Region 9) Regional Tribal Operations Committee (RTOC) Charter as amended 11/13/2014: Mission, Goals, Scope, Structure & Membership, Meetings, Administration, Charter Amendment/Review, and Current Working Draft.

Auroral Current and Electrodynamics Structure (ACES) Observations of Ionospheric Feedback in the Alfven Resonator

NASA Technical Reports Server (NTRS)

Cohen, Ian J.; Lessard, Marc; Lund, Eric J.; Bounds, Scott R.; Kletzing, Craig; Kaeppler, Stephen R.; Sigsbee, Kristine M.; Streltsov, Anatoly V.; Labelle, James W.; Dombrowski, Micah P.;

Planetary Protection and Mars Special Regions--A Suggestion for Updating the Definition.

PubMed

Rettberg, Petra; Anesio, Alexandre M; Baker, Victor R; Baross, John A; Cady, Sherry L; Detsis, Emmanouil; Foreman, Christine M; Hauber, Ernst; Ori, Gian Gabriele; Pearce, David A; Renno, Nilton O; Ruvkun, Gary; Sattler, Birgit; Saunders, Mark P; Smith, David H; Wagner, Dirk; Westall, Frances

2016-02-01

We highlight the role of COSPAR and the scientific community in defining and updating the framework of planetary protection. Specifically, we focus on Mars "Special Regions," areas where strict planetary protection measures have to be applied before a spacecraft can explore them, given the existence of environmental conditions that may be conducive to terrestrial microbial growth. We outline the history of the concept of Special Regions and inform on recent developments regarding the COSPAR policy, namely, the MEPAG SR-SAG2 review and the Academies and ESF joint committee report on Mars Special Regions. We present some new issues that necessitate the update of the current policy and provide suggestions for new definitions of Special Regions. We conclude with the current major scientific questions that remain unanswered regarding Mars Special Regions.

Core-shell homojunction silicon vertical nanowire tunneling field-effect transistors.

PubMed

Yoon, Jun-Sik; Kim, Kihyun; Baek, Chang-Ki

2017-01-23

We propose three-terminal core-shell (CS) silicon vertical nanowire tunneling field-effect transistors (TFETs), which can be fabricated by conventional CMOS technology. CS TFETs show lower subthreshold swing (SS) and higher on-state current than conventional TFETs through their high surface-to-volume ratio, which increases carrier-tunneling region with no additional device area. The on-state current can be enhanced by increasing the nanowire height, decreasing equivalent oxide thickness (EOT) or creating a nanowire array. The off-state current is also manageable for power saving through selective epitaxial growth at the top-side nanowire region. CS TFETs with an EOT of 0.8 nm and an aspect ratio of 20 for the core nanowire region provide the largest drain current ranges with point SS values below 60 mV/dec and superior on/off current ratio under all operation voltages of 0.5, 0.7, and 1.0 V. These devices are promising for low-power applications at low fabrication cost and high device density.

Control of bootstrap current in the pedestal region of tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaing, K. C.; Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53796; Lai, A. L.

2013-12-15

The high confinement mode (H-mode) plasmas in the pedestal region of tokamaks are characterized by steep gradient of the radial electric field, and sonic poloidal U{sub p,m} flow that consists of poloidal components of the E×B flow and the plasma flow velocity that is parallel to the magnetic field B. Here, E is the electric field. The bootstrap current that is important for the equilibrium, and stability of the pedestal of H-mode plasmas is shown to have an expression different from that in the conventional theory. In the limit where ‖U{sub p,m}‖≫ 1, the bootstrap current is driven by themore » electron temperature gradient and inductive electric field fundamentally different from that in the conventional theory. The bootstrap current in the pedestal region can be controlled through manipulating U{sub p,m} and the gradient of the radial electric. This, in turn, can control plasma stability such as edge-localized modes. Quantitative evaluations of various coefficients are shown to illustrate that the bootstrap current remains finite when ‖U{sub p,m}‖ approaches infinite and to provide indications how to control the bootstrap current. Approximate analytic expressions for viscous coefficients that join results in the banana and plateau-Pfirsch-Schluter regimes are presented to facilitate bootstrap and neoclassical transport simulations in the pedestal region.« less

Generation of field-aligned currents and Alfven waves by 3D magnetic reconnection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Z.W.; Lee, L.C.; Otto, A.

1995-07-01

The authors have carried out a three-dimensional compressible MHD simulation to study the generation of field-aligned currents (FAC`s) and Alfven waves by magnetic reconnection for locally antiparallel magnetic fields across the current sheet. Reconnection is triggered by a localized resistivity. The results indicate that both FAC`s and Alfven waves are generated by the three-dimensional reconnection process. Two pairs of FAC`s are generated on each side of current sheet. The polarities of the resulting FAC pair in the leading bulge region are opposite to those of a FAC pair in the trailing quasi-steady region. It is further found that a largemore » portion of the FAC`s ({approximately}40%) is located in the closed field line region. They examine the Walen relation between FAC and parallel vorticity and find that Alfven waves are generated and propagate away from the reconnection site. They discuss the relevance of the results to the observed Region 1 FAC`s at noon. 15 refs., 4 figs.« less

The interplanetary magnetic field B sub y -dependent field-aligned current in the dayside polar cap under quiet conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamauchi, M.; Araki, T.

1989-03-01

Spatial distribution and temporal variation of the interplanetary magnetic field (IMF) B{sub y}-dependent cusp region field-aligned currents (FACs) during quiet periods were studied by use of magnetic data observed by Magsat. The analysis was made for 11 events (each event lasts more than one and a half days) when the IMF B{sub y} component was steadily large and B{sub x} was relatively small ({vert bar}B{sub z}{vert bar} < {vert bar}B{sub y}{vert bar}). Results of the analysis of total 62 half-day periods for the IMF B{sub y}-dependent cusp region FAC are summarized as follows: (1) the IMF B{sub y}-dependent cusp regionmore » FAC is located at around 86{degree}-87{degree} invariant latitude local noon, which is more poleward than the location of the IMF B{sub z}-dependent cusp region FAC; (2) the current density of this FAC is greater than previous studies ({ge} 4 {mu}A/m{sup 2} for IMF B{sub y} = 6 nT); (3) there are two time scales for the IMF B{sub y}-dependent cusp region FAC to appear: the initial rise of the current is on a short time scale, {approximately} 10 min, and it is followed by a gradual increase on a time scale of several hours to a half day; (4) the seasonal change of this FAC is greater than that of the nightside region 1 or region 2 FACs; (5) the IMF B{sub z}-dependent cusp region FAC is not well observed around the cusp when the IMF B{sub y}-dependent cusp region FAC is intense.« less

Global characteristics of auroral Hall currents derived from the Swarm constellation: dependences on season and IMF orientation

NASA Astrophysics Data System (ADS)

Huang, Tao; Lühr, Hermann; Wang, Hui

2017-11-01

On the basis of field-aligned currents (FACs) and Hall currents derived from high-resolution magnetic field data of the Swarm constellation, the average characteristics of these two current systems in the auroral regions are comprehensively investigated by statistical methods. This is the first study considering both current types determined simultaneously by the same spacecraft in both hemispheres. The FAC distribution, derived from the novel Swarm dual-spacecraft approach, reveals the well-known features of Region 1 (R1) and Region 2 (R2) FACs. At high latitudes, Region 0 (R0) FACs appear on the dayside. Their flow direction, up or down, depends on the orientation of the interplanetary magnetic field (IMF) By component. Of particular interest is the distribution of auroral Hall currents. The prominent auroral electrojets are found to be closely controlled by the solar wind input, but we find no dependence of their intensity on the IMF By orientation. The eastward electrojet is about 1.5 times stronger in local summer than in winter. Conversely, the westward electrojet shows less dependence on season. As to higher latitudes, part of the electrojet current is closed over the polar cap. Here the seasonal variation of conductivity mainly controls the current density. During local summer of the Northern Hemisphere, there is a clear channeling of return currents over the polar cap. For positive (negative) IMF By a dominant eastward (westward) Hall current circuit is formed from the afternoon (morning) electrojet towards the dawn side (dusk side) polar cap return current. The direction of polar cap Hall currents in the noon sector depends directly on the orientation of the IMF By. This is true for both signs of the IMF Bz component. Comparable Hall current distributions can be observed in the Southern Hemisphere but for opposite IMF By signs. Around the midnight sector the westward substorm electrojet is dominating. As expected, it is highly dependent on magnetic activity, but it shows only little response to season and IMF By polarity. An important finding is that all the IMF By dependences of FACs and Hall currents practically disappear in the dark winter hemisphere.

A new theoretical model for transmembrane potential and ion currents induced in a spherical cell under low frequency electromagnetic field.

PubMed

Zheng, Yu; Gao, Yang; Chen, Ruijuan; Wang, Huiquan; Dong, Lei; Dou, Junrong

2016-10-01

Time-varying electromagnetic fields (EMF) can induce some physiological effects in neuronal tissues, which have been explored in many applications such as transcranial magnetic stimulation. Although transmembrane potentials and induced currents have already been the subjects of many theoretical studies, most previous works about this topic are mainly completed by utilizing Maxwell's equations, often by solving a Laplace equation. In previous studies, cells were often considered to be three-compartment models with different electroconductivities in different regions (three compartments are often intracellular regions, membrane, and extracellular regions). However, models like that did not take dynamic ion channels into consideration. Therefore, one cannot obtain concrete ionic current changes such as potassium current change or sodium current change by these models. The aim of the present work is to present a new and more detailed model for calculating transmembrane potentials and ionic currents induced by time-varying EMF. Equations used in the present paper originate from Nernst-Plank equations, which are ionic current-related equations. The main work is to calculate ionic current changes induced by EMF exposure, and then transmembrane potential changes are calculated with Hodgkin-Huxley model. Bioelectromagnetics. 37:481-492, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

REGIONAL SCALE COMPARATIVE RISK ASSESSMENT

EPA Science Inventory

Regional Vulnerability Assessment (ReVA) is an approach to regional-scale ecological risk assessment that is currently under development by EPA's Office of Research and Development. The pilot assessment will be done for the mid-Atlantic region and builds on data collected for th...

Demonstration of Bias-Controlled Algorithmic Tuning of Quantum Dots in a Well (DWELL) MidIR Detectors

DTIC Science & Technology

2009-06-01

additionally be utilized to cover a wider spectral range. In recent years, the long-wave IR ( LWIR : 8–12 m) region of the electromagnetic spectrum has been... LWIR region, and they can be sensed by their apparent temper- atures and spectral signatures in the LWIR . Currently, there are three main material...technologies for photonic IR photodetectors in the LWIR region. The HgCdTe (MCT) detector is the current state of the art due to its high responsivity

Macroecology of biodiversity: disentangling local and regional effects.

PubMed

Pärtel, Meelis; Bennett, Jonathan A; Zobel, Martin

2016-07-01

Contents 404 I. 404 II. 404 III. 405 IV. 406 V. 407 VI. 408 409 References 409 SUMMARY: Macroecology of biodiversity disentangles local and regional drivers of biodiversity by exploring large-scale biodiversity relationships with environmental or biotic gradients, generalizing local biodiversity relationships across regions, or comparing biodiversity patterns among species groups. A macroecological perspective is also important at local scales: a full understanding of local biodiversity drivers, including human impact, demands that regional processes be taken into account. This requires knowledge of which species could inhabit a site (the species pool), including those that are currently absent (dark diversity). Macroecology of biodiversity is currently advancing quickly owing to an unprecedented accumulation of biodiversity data, new sampling techniques and analytical methods, all of which better equip us to face current and future challenges in ecology and biodiversity conservation. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Comparison of photospheric electric current and ultraviolet and x-ray emission in a solar active region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haisch, B.M.; Bruner, M.E.; Hagyard, M.J.

This paper presents an extensive set of coordinated observations of a solar active region, taking into account spectroheliograms obtained with the aid of the Solar Maximum Mission (SMM) Ultraviolet Spectrometer Polarimeter (UVSP) instrument, SMM soft x-ray polychromator (XRP) raster maps, and high spatial resolution ultraviolet images of the sun in Lyman-alpha and in the 1600 A continuum. These data span together the upper solar atmosphere from the temperature minimum to the corona. The data are compared to maps of the inferred photospheric electric current derived from the Marshall Space Flight Center (MSFC) vector magnetograph observations. Some empirical correlation is foundmore » between regions of inferred electric current density and the brightest features in the ultraviolet continuum and to a lesser extent those seen in Lyman-alpha within an active region. 29 references.« less

THE EVOLUTION OF THE ELECTRIC CURRENT DURING THE FORMATION AND ERUPTION OF ACTIVE-REGION FILAMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jincheng; Yan, Xiaoli; Qu, Zhongquan

We present a comprehensive study of the electric current related to the formation and eruption of active region filaments in NOAA AR 11884. The vertical current on the solar surface was investigated by using vector magnetograms (VMs) observed by HMI on board the Solar Dynamics Observatory. To obtain the electric current along the filament's axis, we reconstructed the magnetic fields above the photosphere by using nonlinear force-free field extrapolation based on photospheric VMs. Spatio-temporal evolutions of the vertical current on the photospheric surface and the horizontal current along the filament's axis were studied during the long-term evolution and eruption-related period,more » respectively. The results show that the vertical currents of the entire active region behaved with a decreasing trend and the magnetic fields also kept decreasing during the long-term evolution. For the eruption-related evolution, the mean transverse field strengths decreased before two eruptions and increased sharply after two eruptions in the vicinity of the polarity inversion lines underneath the filament. The related vertical current showed different behaviors in two of the eruptions. On the other hand, a very interesting feature was found: opposite horizontal currents with respect to the current of the filament's axis appeared and increased under the filament before the eruptions and disappeared after the eruptions. We suggest that these opposite currents were carried by the new flux emerging from the photosphere bottom and might be the trigger mechanism for these filament eruptions.« less

SEE-GRID eInfrastructure for Regional eScience

NASA Astrophysics Data System (ADS)

Prnjat, Ognjen; Balaz, Antun; Vudragovic, Dusan; Liabotis, Ioannis; Sener, Cevat; Marovic, Branko; Kozlovszky, Miklos; Neagu, Gabriel

In the past 6 years, a number of targeted initiatives, funded by the European Commission via its information society and RTD programmes and Greek infrastructure development actions, have articulated a successful regional development actions in South East Europe that can be used as a role model for other international developments. The SEEREN (South-East European Research and Education Networking initiative) project, through its two phases, established the SEE segment of the pan-European G ´EANT network and successfully connected the research and scientific communities in the region. Currently, the SEE-LIGHT project is working towards establishing a dark-fiber backbone that will interconnect most national Research and Education networks in the region. On the distributed computing and storage provisioning i.e. Grid plane, the SEE-GRID (South-East European GRID e-Infrastructure Development) project, similarly through its two phases, has established a strong human network in the area of scientific computing and has set up a powerful regional Grid infrastructure, and attracted a number of applications from different fields from countries throughout the South-East Europe. The current SEEGRID-SCI project, ending in April 2010, empowers the regional user communities from fields of meteorology, seismology and environmental protection in common use and sharing of the regional e-Infrastructure. Current technical initiatives in formulation are focusing on a set of coordinated actions in the area of HPC and application fields making use of HPC initiatives. Finally, the current SEERA-EI project brings together policy makers - programme managers from 10 countries in the region. The project aims to establish a communication platform between programme managers, pave the way towards common e-Infrastructure strategy and vision, and implement concrete actions for common funding of electronic infrastructures on the regional level. The regional vision on establishing an e-Infrastructure compatible with European developments, and empowering the scientists in the region in equal participation in the use of pan- European infrastructures, is materializing through the above initiatives. This model has a number of concrete operational and organizational guidelines which can be adapted to help e-Infrastructure developments in other world regions. In this paper we review the most important developments and contributions by the SEEGRID- SCI project.

Pathways and Hydrography in the Mesoamerican Barrier Reef System Part 1: Circulation

NASA Astrophysics Data System (ADS)

Carrillo, L.; Johns, E. M.; Smith, R. H.; Lamkin, J. T.; Largier, J. L.

2015-10-01

Acoustic Doppler Current Profiler (ADCP) measurements and surface drifters released from two oceanographic cruises conducted during March 2006 and January/February 2007 are used to investigate the circulation off the Mesoamerican Barrier Reef System (MBRS). We show that the MBRS circulation can be divided into two distinct regimes, a northern region dominated by the strong, northward-flowing Yucatan Current, and a southern region with weaker southward coastal currents and the presence of the Honduras Gyre. The latitude of impingement of the Cayman Current onto the coastline varies with time, and creates a third region, which acts as a boundary between the northern and southern circulation regimes. This circulation pattern yields two zones in terms of dispersal, with planktonic propagules in the northern region being rapidly exported to the north, whereas plankton in the southern and impingement regions may be retained locally or regionally. The latitude of the impingement region shifts interannually and intra-annually up to 3° in latitude. Sub-mesoscale features are observed in association with topography, e.g., flow bifurcation around Cozumel Island, flow wake north of Chinchorro Bank and separation of flow from the coast just north of Bahia de la Ascencion. This third feature is evident as cyclonic recirculation in coastal waters, which we call the Ascencion-Cozumel Coastal Eddy. An understanding of the implications of these different circulation regimes on water mass distributions, population connectivity, and the fate of land-based pollutants in the MBRS is critically important to better inform science-based resource management and conservation plans for the MBRS coral reefs.

The Current Driven Kink Instability and its Relationship to Delta-Spot Active Regions

NASA Astrophysics Data System (ADS)

Linton, Mark George

The current driven kink instability may be the cause of both the unusual morphology of solar δ-spot active regions and the tendency of these regions to be significantly more flare active than most active regions. We investigate the current driven kink instability of flux tubes in the solar interior both with a linear stability analysis and with nonlinear MHD simulations. The linear analysis shows that there is a critical twist, which depends on the axial magnetic field profile, that a flux tube needs to become kink unstable. This critical twist decreases as the tube expands, so twisted flux tubes will become increasingly unstable as they rise through the convection zone. The nonlinear simulations show that a twisted tube excited by a single unstable kink mode will evolve to a helical equilibrium state. The emergence through the photosphere of such a kinked tube would create an active region which was tilted with respect to Hale's law and which would rotate as it evolved, as δ-spots are observed to do. We then find that, when excited by multiple unstable kink modes, highly twisted flux tubes develop concentrated kinks. These concentrated kinks would produce more of the observed characteristics of δ-spot active regions. They would create active regions which, in addition to emerging tilted and then rotating, would remain compact as they evolved, and develop strong shear along their magnetic neutral line. Finally, we find that a strong concentrated kink develops a current sheet at which the magnetic field reconnects, which may be the cause of the high flare activity of δ-spots.

High voltage MOSFET devices and methods of making the devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Sujit; Matocha, Kevin; Chatty, Kiran

A SiC MOSFET device having low specific on resistance is described. The device has N+, P-well and JFET regions extended in one direction (Y-direction) and P+ and source contacts extended in an orthogonal direction (X-direction). The polysilicon gate of the device covers the JFET region and is terminated over the P-well region to minimize electric field at the polysilicon gate edge. In use, current flows vertically from the drain contact at the bottom of the structure into the JFET region and then laterally in the X direction through the accumulation region and through the MOSFET channels into the adjacent N+more » region. The current flowing out of the channel then flows along the N+ region in the Y-direction and is collected by the source contacts and the final metal. Methods of making the device are also described.« less

High voltage MOSFET devices and methods of making the devices

DOEpatents

Banerjee, Sujit; Matocha, Kevin; Chatty, Kiran

2015-12-15

A SiC MOSFET device having low specific on resistance is described. The device has N+, P-well and JFET regions extended in one direction (Y-direction) and P+ and source contacts extended in an orthogonal direction (X-direction). The polysilicon gate of the device covers the JFET region and is terminated over the P-well region to minimize electric field at the polysilicon gate edge. In use, current flows vertically from the drain contact at the bottom of the structure into the JFET region and then laterally in the X direction through the accumulation region and through the MOSFET channels into the adjacent N+ region. The current flowing out of the channel then flows along the N+ region in the Y-direction and is collected by the source contacts and the final metal. Methods of making the device are also described.

Influence of solar radiation absorbed by phytoplankton on the thermal structure and circulation of the tropical Atlantic Ocean

NASA Astrophysics Data System (ADS)

Frouin, Robert; Ueyoshi, Kyozo; Kampel, Milton

2007-09-01

Numerical experiments conducted with an ocean general ocean circulation model reveal the potential influence of solar radiation absorbed by phytoplankton on the thermal structure and currents of the Tropical Atlantic Ocean. In the model, solar radiation penetration is parameterized explicitly as a function of chlorophyll-a concentration, the major variable affecting water turbidity in the open ocean. Two types of runs are performed, a clear water (control) run with a constant minimum chlorophyll-a concentration of 0.02 mgm -3, and a turbid water (chlorophyll) run with space- and time-varying chlorophyll-a concentration from satellite data. The difference between results from the two runs yields the biological effects. In the chlorophyll run, nutrients and biology production are implicitly taken into account, even though biogeochemical processes are not explicitly included, since phytoplankton distribution, prescribed from observations, is the result of those processes. Due to phytoplankton-radiation forcing, the surface temperature is higher by 1-2 K on average annually in the region of the North Equatorial current, the Northern part of the South Equatorial current, and the Caribbean system, and by 3-4 K in the region of the Guinea current. In this region, upwelling is reduced, and heat trapped in the surface layers by phytoplankton is not easily removed. The surface temperature is lower by 1 K in the Northern region of the Benguela current, due to increased upwelling. At depth, the equatorial Atlantic is generally cooler, as well as the eastern part of the tropical basin (excluding the region of the sub-tropical gyres). The North and South equatorial currents, as well as the Equatorial undercurrent, are enhanced by as much as 3-4 cms -1, and the circulation of the subtropical gyres is increased. Pole-ward heat transport is slightly reduced North of 35°N, suggesting that phytoplankton, by increasing the horizontal return flow in the subtropical region, may exert a cooling influence on higher latitude regions. The findings indicate that biology-induced buoyancy plays a significant role, in an indirect if not direct way, in the variability of the Tropical Atlantic Ocean, with consequences on atmospheric circulation and climate.

Investigation of the double exponential in the current-voltage characteristics of silicon solar cells

NASA Technical Reports Server (NTRS)

Wolf, M.; Noel, G. T.; Stirn, R. J.

1976-01-01

A theoretical analysis is presented of certain peculiarities of the current-voltage characteristics of silicon solar cells, involving high values of the empirical constant A in the diode equation for a p-n junction. An attempt was made in a lab experiment to demonstrate that the saturation current which is associated with the exponential term qV/A2kT of the I-V characteristic, with A2 roughly equal to 2, originates in the space charge region and that it can be increased, as observed on ATS-1 cells, by the introduction of additional defects through low energy proton irradiation. It was shown that the proton irradiation introduces defects into the space charge region which give rise to a recombination current from this region, although the I-V characteristic is, in this case, dominated by an exponential term which has A = 1.

Passive runaway electron suppression in tokamak disruptions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, H. M.; Helander, P.; Boozer, A. H.

2013-07-15

Runaway electrons created in disruptions pose a serious problem for tokamaks with large current. It would be desirable to have a runaway electron suppression method which is passive, i.e., a method that does not rely on an uncertain disruption prediction system. One option is to let the large electric field inherent in the disruption drive helical currents in the wall. This would create ergodic regions in the plasma and increase the runaway losses. Whether these regions appear at a suitable time and place to affect the formation of the runaway beam depends on disruption parameters, such as electron temperature andmore » density. We find that it is difficult to ergodize the central plasma before a beam of runaway current has formed. However, the ergodic outer region will make the Ohmic current profile contract, which can lead to instabilities that yield large runaway electron losses.« less

The quiet evening auroral arc and the structure of the growth phase near-Earth plasma sheet

NASA Astrophysics Data System (ADS)

Coroniti, F. V.; Pritchett, P. L.

2014-03-01

The plasma pressure and current configuration of the near-Earth plasma sheet that creates and sustains the quiet evening auroral arc during the growth phase of magnetospheric substorms is investigated. We propose that the quiet evening arc (QEA) connects to the thin near-Earth current sheet, which forms during the development of the growth phase enhancement of convection. The current sheet's large polarization electric fields are shielded from the ionosphere by an Inverted-V parallel potential drop, thereby producing the electron precipitation responsible for the arc's luminosity. The QEA is located in the plasma sheet region of maximal radial pressure gradient and, in the east-west direction, follows the vanishing of the approximately dawn-dusk-directed gradient or fold in the plasma pressure. In the evening sector, the boundary between the Region1 and Region 2 current systems occurs where the pressure maximizes (approximately radial gradient of the pressure vanishes) and where the approximately radial gradient of the magnetic flux tube volume also vanishes in an inflection region. The proposed intricate balance of plasma sheet pressure and currents may well be very sensitive to disruption by the arrival of equatorward traveling auroral streamers and their associated earthward traveling dipolarization fronts.

Observations and modeling of the ionospheric gravity and diamagnetic current systems from CHAMP and Swarm measurements

NASA Astrophysics Data System (ADS)

Alken, P.

2016-01-01

The CHAMP and Swarm satellites, which provide high-quality magnetic field measurements in low-altitude polar orbits, are ideally suited for investigating ionospheric current systems. In this study, we focus on the F region low-latitude gravity and diamagnetic currents which are prominent in the equatorial ionization anomaly (EIA) region in the North and South Hemisphere. During its 10 year mission, CHAMP has sampled nearly the entire altitude range of the EIA, offering the opportunity to study these currents from above, inside, and below their source region. The Swarm constellation offers the unique opportunity to study near-simultaneous measurements of the current systems at different longitudinal separations. In this study, we present new observations of these current systems, investigate their seasonal and local time dependence, investigate the use of in situ electron density measurements as a proxy for the magnetic perturbations, and compute the longitudinal self correlation of these currents. We find that these currents are strongest during spring and fall, produce nighttime magnetic fields at satellite altitude of up to 5-7 nT during solar maximum, 2-3 nT during solar minimum, and are highly correlated with in situ electron density measurements. We also find these currents are self-correlated above 70% up to 15° longitude in both hemispheres during the evening.

Early afterdepolarizations promote transmural reentry in ischemic human ventricles with reduced repolarization reserve

PubMed Central

Dutta, Sara; Mincholé, Ana; Zacur, Ernesto; Quinn, T. Alexander; Taggart, Peter; Rodriguez, Blanca

2016-01-01

Aims Acute ischemia is a major cause of sudden arrhythmic death, further promoted by potassium current blockers. Macro-reentry around the ischemic region and early afterdepolarizations (EADs) caused by electrotonic current have been suggested as potential mechanisms in animal and isolated cell studies. However, ventricular and human-specific arrhythmia mechanisms and their modulation by repolarization reserve remain unclear. The goal of this paper is to unravel multiscale mechanisms underlying the modulation of arrhythmic risk by potassium current (IKr) block in human ventricles with acute regional ischemia. Methods and results A human ventricular biophysically-detailed model, with acute regional ischemia is constructed by integrating experimental knowledge on the electrophysiological ionic alterations caused by coronary occlusion. Arrhythmic risk is evaluated by determining the vulnerable window (VW) for reentry following ectopy at the ischemic border zone. Macro-reentry around the ischemic region is the main reentrant mechanism in the ischemic human ventricle with increased repolarization reserve due to the ATP-sensitive potassium current (IK(ATP)) activation. Prolongation of refractoriness by 4% caused by 30% IKr reduction counteracts the establishment of macro-reentry and reduces the VW for reentry (by 23.5%). However, a further decrease in repolarization reserve (50% IKr reduction) is less anti-arrhythmic despite further prolongation of refractoriness. This is due to the establishment of transmural reentry enabled by electrotonically-triggered EADs in the ischemic border zone. EADs are produced by L-type calcium current (ICaL) reactivation due to prolonged low amplitude electrotonic current injected during the repolarization phase. Conclusions Electrotonically-triggered EADs are identified as a potential mechanism facilitating intramural reentry in a regionally-ischemic human ventricles model with reduced repolarization reserve. PMID:26850675

Improving integrated waste management at the regional level: the case of Lombardia.

PubMed

Rigamonti, Lucia; Falbo, Alida; Grosso, Mario

2013-09-01

The article summarises the main results of the 'Gestione Rifiuti in Lombardia: Analisi del ciclo di vita' (Waste management in Lombardia region: Life cycle assessment; GERLA) project. Life cycle assessment (LCA) has been selected by Regione Lombardia as a strategic decision support tool in the drafting of its new waste management programme. The goal was to use the life cycle thinking approach to assess the current regional situation and thus to give useful strategic indications for the future waste management. The first phase of the study consisted of the LCA of the current management of municipal waste in the Lombardia region (reference year: 2009). The interpretation of such results has allowed the definition of four possible waste management scenarios for the year 2020, with the final goal being to improve the environmental performance of the regional system. The results showed that the current integrated waste management of Lombardia region is already characterised by good energy and environmental performances. However, there is still room for further improvement: actions based, on the one hand, on a further increase in recycling rates and, on the other hand, on a series of technological modifications, especially in food waste and residual waste management, can be undertaken to improve the overall system.

The effect of Birkeland currents on magnetic field topology

NASA Technical Reports Server (NTRS)

Peroomian, Vahe; Lyons, Larry R.; Schulz, Michael

1996-01-01

A technique was developed for the inclusion of large scale magnetospheric current systems in magnetic field models. The region 1 and 2 Birkeland current systems are included in the source surface model of the terrestrial magnetosphere. The region 1 and 2 Birkeland currents are placed in the model using a series of field aligned, infinitely thin wire segments. The normal component of the magnetic field from these currents is calculated on the surface of the magnetopause and shielded using image current carrying wires placed outside of the magnetosphere. It is found that the inclusion of the Birkeland currents in the model results in a northward magnetic field in the near-midnight tail, leading to the closure of previously open flux in the tail, and a southward magnetic field in the flanks. A sunward shift in the separatrix is observed.

[Morphology determination of ionization region in multi-needle-to-plate negative corona discharge].

PubMed

Su, Peng-Hao; Zhu, Yi-Min; Chen, Hai-Feng

2007-11-01

Based on the former work on the current-voltage characteristics of a multi-needle-to-plate negative corona discharge at atmospheric pressure, the present work uses the method of OES (optical emission spectrum) for measuring N2 emission spectrum, and the morphology determination of the ionization region has been investigated. According to the distribution of N2 second positive band's intensity I(SPB), the highest of all bands, the outline of the ionization region was drawn fairly accurately. The relationship between I(SPB) and discharge current I can be obtained through the volume integral of the I(SPB). The experimental results show that the size of the ionization region enhances with the rise of the applied voltage U, and the electron avalanche begins at about 1 mm off the tips of needle electrode and multiplies only in the range of several millimeters, indicating that, the range of the ionization region is at the magnitude of mm. The electron avalanche along the axis of the needle develops farther than that along the radial direction of needle, and the shape of the ionization region looks like a bullet. The integral of I(SPB) is second-order linear to I, with a very second order coefficient, meaning that the main excited substance is N2. Energetic electrons mainly exist in ionization region while ions are the main charged particles to form discharge current in the transfer region.

Evaluation of wind induced currents modeling along the Southern Caspian Sea

NASA Astrophysics Data System (ADS)

Bohluly, Asghar; Esfahani, Fariba Sadat; Montazeri Namin, Masoud; Chegini, Fatemeh

2018-02-01

To improve our understanding of the Caspian Sea hydrodynamics, its circulation is simulated with special focus on wind-driven currents of its southern basin. The hydrodynamic models are forced with a newly developed fine resolution wind field to increase the accuracy of current modeling. A 2D shallow water equation model and a 3D baroclinic model are applied separately to examine the performance of each model for specific applications in the Caspian Sea. The model results are validated against recent field measurements including AWAC and temperature observations in the southern continental shelf region. Results show that the 2D model is able to well predict the depth-averaged current speed in storm conditions in narrow area of southern coasts. This finding suggests physical oceanographers apply 2D modeling as a more affordable method for extreme current speed analysis at the continental shelf region. On the other hand the 3D model demonstrates a better performance in reproducing monthly mean circulation and hence is preferable for surface circulation of Caspian Sea. Monthly sea surface circulation fields of the southern basin reveal a dipole cyclonic-anticyclonic pattern, a dominant eastward current along the southern coasts which intensifies from May to November and a dominant southward current along the eastern coasts in all months except February when the flow is northward. Monthly mean wind fields exhibit two main patterns including a north-south pattern occurring at warm months and collision of two wind fronts especially in the cold months. This collision occurs on a narrow region at the southern continental shelf regions. Due to wind field complexities, it leads to a major source of uncertainty in predicting the wind-driven currents. However, this source of uncertainty is significantly alleviated by applying a fine resolution wind field.

The feasibility of a regional CTDI{sub vol} to estimate organ dose from tube current modulated CT exams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khatonabadi, Maryam; Kim, Hyun J.; Lu, Peiyun

Purpose: In AAPM Task Group 204, the size-specific dose estimate (SSDE) was developed by providing size adjustment factors which are applied to the Computed Tomography (CT) standardized dose metric, CTDI{sub vol}. However, that work focused on fixed tube current scans and did not specifically address tube current modulation (TCM) scans, which are currently the majority of clinical scans performed. The purpose of this study was to extend the SSDE concept to account for TCM by investigating the feasibility of using anatomic and organ specific regions of scanner output to improve accuracy of dose estimates. Methods: Thirty-nine adult abdomen/pelvis and 32more » chest scans from clinically indicated CT exams acquired on a multidetector CT using TCM were obtained with Institutional Review Board approval for generating voxelized models. Along with image data, raw projection data were obtained to extract TCM functions for use in Monte Carlo simulations. Patient size was calculated using the effective diameter described in TG 204. In addition, the scanner-reported CTDI{sub vol} (CTDI{sub vol,global}) was obtained for each patient, which is based on the average tube current across the entire scan. For the abdomen/pelvis scans, liver, spleen, and kidneys were manually segmented from the patient datasets; for the chest scans, lungs and for female models only, glandular breast tissue were segmented. For each patient organ doses were estimated using Monte Carlo Methods. To investigate the utility of regional measures of scanner output, regional and organ anatomic boundaries were identified from image data and used to calculate regional and organ-specific average tube current values. From these regional and organ-specific averages, CTDI{sub vol} values, referred to as regional and organ-specific CTDI{sub vol}, were calculated for each patient. Using an approach similar to TG 204, all CTDI{sub vol} values were used to normalize simulated organ doses; and the ability of each normalized dose to correlate with patient size was investigated. Results: For all five organs, the correlations with patient size increased when organ doses were normalized by regional and organ-specific CTDI{sub vol} values. For example, when estimating dose to the liver, CTDI{sub vol,global} yielded a R{sup 2} value of 0.26, which improved to 0.77 and 0.86, when using the regional and organ-specific CTDI{sub vol} for abdomen and liver, respectively. For breast dose, the global CTDI{sub vol} yielded a R{sup 2} value of 0.08, which improved to 0.58 and 0.83, when using the regional and organ-specific CTDI{sub vol} for chest and breasts, respectively. The R{sup 2} values also increased once the thoracic models were separated for the analysis into females and males, indicating differences between genders in this region not explained by a simple measure of effective diameter. Conclusions: This work demonstrated the utility of regional and organ-specific CTDI{sub vol} as normalization factors when using TCM. It was demonstrated that CTDI{sub vol,global} is not an effective normalization factor in TCM exams where attenuation (and therefore tube current) varies considerably throughout the scan, such as abdomen/pelvis and even thorax. These exams can be more accurately assessed for dose using regional CTDI{sub vol} descriptors that account for local variations in scanner output present when TCM is employed.« less

A combined study of photospheric magnetic and current helicities and subsurface kinetic helicities of solar active regions during 2006-2013

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seligman, D.; Petrie, G. J. D.; Komm, R.

2014-11-10

We compare the average photospheric current helicity H{sub c} , photospheric twist parameter α (a well-known proxy for the full relative magnetic helicity), and subsurface kinetic helicity H{sub k} for 194 active regions observed between 2006-2013. We use 2440 Hinode photospheric vector magnetograms, and the corresponding subsurface fluid velocity data derived from GONG (2006-2012) and Helioseismic and Magnetic Imager (2010-2013) dopplergrams. We find a significant hemispheric bias in all three parameters. The subsurface kinetic helicity is preferentially positive in the southern hemisphere and negative in the northern hemisphere. The photospheric current helicity and the α parameter have the same biasmore » for strong fields (|B| > 1000 G) and no significant bias for weak fields (100 G <|B| < 500 G). We find no significant region-by-region correlation between the subsurface kinetic helicity and either the strong-field current helicity or α. Subsurface fluid motions of a given handedness correspond to photospheric helicities of both signs in approximately equal numbers. However, common variations appear in annual averages of these quantities over all regions. Furthermore, in a subset of 77 regions, we find significant correlations between the temporal profiles of the subsurface and photospheric helicities. In these cases, the sign of the linear correlation coefficient matches the sign relationship between the helicities, indicating that the photospheric magnetic field twist is sensitive to the twisting motions below the surface.« less

The Asia Pacific Association for Medical Informatics (APAMI) and World Organisation of Family Doctors (WONCA) Consortium on General and Family Practice Informatics--a statement of intent.

PubMed

Liaw, S T; Kidd, M; Cesnik, B; Lun, K C; Goh, L G; Yoo, T; Wun, Y T

1998-01-01

This paper describes the establishment of a consortium to advance health and medical informatics in general/family practice in the Asia Pacific Region. The objectives, current activities currently taking place in the region and key activities planned will be outlined.

Reconstruction of F-Region Electric Current Densities from more than 2 Years of Swarm Satellite Magnetic data

NASA Astrophysics Data System (ADS)

Tozzi, R.; Pezzopane, M.; De Michelis, P.; Pignalberi, A.; Siciliano, F.

2016-12-01

The constellation geometry adopted by ESA for Swarm satellites has opened the way to new investigations based on magnetic data. An example is the curl-B technique that allows reconstructing F-region electric current density in terms of its radial, meridional, and zonal components based on data from two satellites of Swarm constellation (Swarm A and B) which fly at different altitudes. Here, we apply this technique to more than 2 years of Swarm magnetic vector data and investigate the average large scale behaviour of F-region current densities as a function of local time, season and different interplanetary conditions (different strength and direction of the three IMF components and/or geomagnetic activity levels).

Comparison of field-aligned currents at ionospheric and magnetospheric altitudes

NASA Technical Reports Server (NTRS)

Spence, H. E.; Kivelson, M. G.; Walker, R. J.

1988-01-01

Using the empirical terrestrial magnetospheric magnetic field models of Tsyganenko and Usmanov (1982) and Tsyganenko (1987) the average field-aligned currents (FACs) in the magnetosphere were determined as a function of the Kp index. Three major model FAC systems were identified, namely, the dayside region 1, the nightside region 1, and the nightside polar cap. The models provide information about the sources of the current systems. Mapped ionospheric model FACs are compared with low-altitude measurements obtained by the spacecraft. It is found that low-altitude data can reveal either classic region 1/2 or more highly structured FAC patterns. Therefore, statistical results either obtained from observations or inferred from models are expected to be averages over temporally and spatially shifting patterns.

Current distribution in conducting nanowire networks

NASA Astrophysics Data System (ADS)

Kumar, Ankush; Vidhyadhiraja, N. S.; Kulkarni, Giridhar U.

2017-07-01

Conducting nanowire networks find diverse applications in solar cells, touch-screens, transparent heaters, sensors, and various related transparent conducting electrode (TCE) devices. The performances of these devices depend on effective resistance, transmittance, and local current distribution in these networks. Although, there have been rigorous studies addressing resistance and transmittance in TCE, not much attention is paid on studying the distribution of current. Present work addresses this compelling issue of understanding current distribution in TCE networks using analytical as well as Monte-Carlo approaches. We quantified the current carrying backbone region against isolated and dangling regions as a function of wire density (ranging from percolation threshold to many multiples of threshold) and compared the wired connectivity with those obtained from template-based methods. Further, the current distribution in the obtained backbone is studied using Kirchhoff's law, which reveals that a significant fraction of the backbone (which is believed to be an active current component) may not be active for end-to-end current transport due to the formation of intervening circular loops. The study shows that conducting wire based networks possess hot spots (extremely high current carrying regions) which can be potential sources of failure. The fraction of these hot spots is found to decrease with increase in wire density, while they are completely absent in template based networks. Thus, the present work discusses unexplored issues related to current distribution in conducting networks, which are necessary to choose the optimum network for best TCE applications.

USEPA REGION 10 REGIONAL ENVIRONMENTAL MONITORING AND ASSESSMENT PROGRAM: PROGRAM OVERVIEW

EPA Science Inventory

The USEPA designed and implemented the Environmental Assessment Program (EMAP) to determine the current status, extent, changes, and trends in indicators of the condition of the Nations ecological resources on regional and national scales with known confidence. USEPA Region 10s ...

Currents' spatial structure in the Western, Central and South-Eastern Baltic on the base of numerical model and ADCP data analysis

NASA Astrophysics Data System (ADS)

Golenko, Mariya; Golenko, Nikolay

2014-05-01

Numerical modeling of the currents' spatial structure in some regions of the Baltic Sea is performed on the base of POM (Princeton Ocean Model). The calculations were performed under the westerly (most frequent in the Baltic) and north-easterly wind forcings. In the regions adjacent to the Kaliningrad Region's, Polish and Lithuanian coasts these winds generate oppositely directed geostrophic, drift and others types of currents. On the whole these processes can be considered as downwelling and upwelling. Apart from the regions mentioned above the Slupsk Furrow region, which determines the mass and momentum exchange between the Western and Central Baltic, is also considered. During the analysis of currents not only the whole model velocity but also components directed along and across the barotropic geostrophic current velocity are considered. The along geostrophic component for one's turn is separated into the geostrophic current itself and an ageostrophic part. The across geostrophic component is totally ageostrophic. The velocity components directed along and across the geostrophic current approximately describe the velocity components directed along the coast (along isobathes) and from the coast towards the open sea. The suggested approach allowed to present the currents' spatial structures typical for different wind forcings as two maps with the components directed along and across the barotropic geostrophic current velocity. On these maps the areas of the intensive alongshore currents are clearly depicted (for ex. near the base of the Hel Spit, in the region of the Slupsk Sill). The combined analysis of the vectors of the whole and geostrophic velocities allows to reveal the areas where the geostrophic component is significantly strengthened or weakened by the ageostrophic component. Under the westerly wind such currents' features are clearly observed near the end of the Hel Spit and at the southern boarder of the Slupsk Sill, under the north-easterly wind - near the base of the Hel Spit, at the southern boarder of the Slupsk Furrow, near the Curonian Spit (where the relief is bent). On the maps presenting the spatial distributions of the across shore velocities the areas where the mass and momentum transport from the shore to the open sea in the surface layer and vice versa takes place are discriminated. There are also revealed the areas where sharp changes of different velocity components under the wind changes are expected as well as the areas where such changes are expected to be minimal. The model is validated using the field surveys of current velocities by ADCP in the area adjacent to the Kaliningrad region. The comparison of current velocities has shown a close correspondence. In rather wide area the directions and amplitudes of the model and ADCP surface velocities are close, that is additionally confirmed by the comparison of the local vorticity distributions. On the vertical transects of the ADCP current velocity directed across the shoreline the geostrophic jet is clearly pronounced. Its horizontal and vertical scales are in close correspondence with ones of the model jet. At that the more detail calculations which are allowed during the modeling have shown that the geostrophic currents amount to 40-60% (in average) of the whole velocity; two components of the ageostrophic velocity directed along and across the geostrophic velocity are highly variable (from 10 to 60% of the whole velocity). The ageostrophic component directed along the geostrophic current generally strengthens it (up to 20-40% in average and up to 60-70% near the end of the Hel Spit). But in some regions, for example, in the Slupsk Furrow the ageostrophic component slows down the geostrophic current (to 30-40%). In some narrow local areas immediately adjacent to the coast currents directed oppositely to the general quasi geostrophic jet were registered on both field and model data. Before the comparison with the field data these local jets revealed on the model data were considered as improbable. As a result, the comparative analysis of the field and model data led to more detail understanding of dynamic processes in some coastal parts of the Baltic Sea.

Connectivity of the South Florida Coral Reef Ecosystem to Upstream Waters of the Western Caribbean and Gulf of Mexico

NASA Astrophysics Data System (ADS)

Johns, E. M.; Smith, R. H.; Lamkin, J. T.; Birbriezca, L. C.; Vasquez-Yeomans, L.; Cordero, E. S.

2008-05-01

The coastal waters of south Florida, including the coral reefs of NOAA's Florida Keys National Marine Sanctuary (FKNMS), are directly connected by means of strong ocean currents with upstream waters of the western Caribbean Sea and the Gulf of Mexico. The Caribbean Current and the Loop Current provide a rapid conduit for transport from Mexican and Belizean coral reefs, located off the eastern shore of the Yucatan Peninsula, to nearshore regions of northern Cuba, Florida, and the Bahamas. Interdisciplinary cruise data collected in August 2002, March 2006 and January 2007 aboard the NOAA Ship Gordon Gunter, in combination with satellite-tracked surface drifter trajectories and remote sensing imagery, clearly show the highly variable and dynamic nature of the regional current regimes and provide a means of quantifying the potential pathways and transport rates of the coastal waters and their biological and chemical constituents from one region to another. Results from these cruises and ancillary data show that the study areas are connected with rapid transport time scales, and that frontal eddies and gyres play an important role in establishing the time and length scales of this connectivity. Such direct physical connectivity between the coral reef biota of these geographically separated spawning grounds via ocean currents may have an important influence on the degree of biological connectivity between regional larval populations. Initial analyses of ichthyoplankton surveys and inshore collections along the Yucatan mesoamerican reef suggest large scale variability in both local recruitment and large scale spatial distribution. Despite strong northward flowing currents, inshore collections indicate that local recruitment in some areas is strongly influenced by small scale circulation patterns. However, the distribution of spawning aggregations along the Yucatan coast suggests a larger role for the Caribbean Current. Determining the interactions between the larger scale circulation patterns and the smaller scale biological processes is a key research objective for understanding the observed regional population connections.

Interplanetary magnetic field control of mantle precipitation and associated field-aligned currents

NASA Technical Reports Server (NTRS)

Xu, Dingan; Kivelson, Margaret G.; Walker, Ray J.; Newell, Patrick T.; Meng, C.-I.

1995-01-01

Dayside reconnection, which is particularly effective for a southward interplanetary magnetic field (IMF), allows magnetosheath particles to enter the magnetosphere where they form the plasma mantle. The motions of the reconnected flux tube produce convective flows in the ionosphere. It is known that the convection patterns in the polar cap are skewed to the dawnside for a positive IMF B(sub y) (or duskside for a negative IMF B(sub y)) in the northern polar cap. Correspondingly, one would expect to find asymmetric distributions of mantle particle precipitation, but previous results have been unclear. In this paper the correlation between B(sub y) and the distribution of mantle particle precipitation is studied for steady IMF conditions with southward IMF. Ion and electron data from the Defense Meteorological Satellite Program (DMSP) F6 and F7 satellites are used to identify the mantle region and IMP 8 is used as a solar wind monitor to characterize the IMF. We study the local time extension of mantle precipitation in the prenoon and postnoon regions. We find that, in accordance with theoretical expectations for a positive (negative) IMF B(sub y), mantle particle precipitation mainly appears in the prenoon region of the northern (southern) hemisphere. The mantle particle precipitation can extend to as early as 0600 magnetic local time (MLT) in the prenoon region but extends over a smaller local time region in the postnoon sector (we did not find mantle plasma beyond 1600 MLT in our data set although coverage is scant in this area). Magnetometer data from F7 are used to determine whether part of the region 1 current flows on open field lines. We find that at times part of the region 1 sense current extends into the region of mantle particle precipitation, and is therefore on open field lines. In other cases, region 1 currents are absent on open field lines. Most of the observed features can be readily interpreted in terms of the open magnetosphere model.

GUARD RING SEMICONDUCTOR JUNCTION

DOEpatents

Goulding, F.S.; Hansen, W.L.

1963-12-01

A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

Break-up of the Atlantic deep western boundary current into eddies at 8 degrees S.

PubMed

Dengler, M; Schott, F A; Eden, C; Brandt, P; Fischer, J; Zantopp, R J

2004-12-23

The existence in the ocean of deep western boundary currents, which connect the high-latitude regions where deep water is formed with upwelling regions as part of the global ocean circulation, was postulated more than 40 years ago. These ocean currents have been found adjacent to the continental slopes of all ocean basins, and have core depths between 1,500 and 4,000 m. In the Atlantic Ocean, the deep western boundary current is estimated to carry (10-40) x 10(6) m3 s(-1) of water, transporting North Atlantic Deep Water--from the overflow regions between Greenland and Scotland and from the Labrador Sea--into the South Atlantic and the Antarctic circumpolar current. Here we present direct velocity and water mass observations obtained in the period 2000 to 2003, as well as results from a numerical ocean circulation model, showing that the Atlantic deep western boundary current breaks up at 8 degrees S. Southward of this latitude, the transport of North Atlantic Deep Water into the South Atlantic Ocean is accomplished by migrating eddies, rather than by a continuous flow. Our model simulation indicates that the deep western boundary current breaks up into eddies at the present intensity of meridional overturning circulation. For weaker overturning, continuation as a stable, laminar boundary flow seems possible.

Spectroscopic study of transparency current in mid-infrared quantum cascade lasers.

PubMed

Revin, Dmitry G; Hassan, Randa S; Krysa, Andrey B; Wang, Yongrui; Belyanin, Alexey; Kennedy, Kenneth; Atkins, Chris N; Cockburn, John W

2012-08-13

We report measurements which give direct insight into the origins of the transparency current for λ ~5 µm In0.6Ga0.4As/In0.42Al0.58As quantum cascade lasers in the temperature range of 80-280 K. The transparency current values have been found from broadband transmission measurements through the laser waveguides under sub-threshold operating conditions. Two active region designs were compared. The active region of the first laser is based on double-LO-phonon relaxation approach, while the second device has only one lower level, without specially designed resonant LO-phonon assisted depopulation. It is shown that transparency current contributes more than 70% to the magnitude of threshold current at high temperatures for both designs.

The new Andean Regional Office of Astronomy for Development

NASA Astrophysics Data System (ADS)

Char, Farid; Forero-Romero, Jaime

2016-10-01

The Andean Regional Office of Astronomy for Development (ROAD) is a new effort in South America to serve several goals in astronomical development. The six countries in the Andean ROAD (Bolivia, Colombia, Chile, Ecuador, Peru and Venezuela) represent a common language block in the region. They work together to develop strategies to strengthen the professional research, education and popularization of astronomy. Our current Working Structure comprises a ROAD Coordinator and one Coordinators in each Task Force. Here we describe the main points of the ROAD's current action plan.

The analytical approach to optimization of active region structure of quantum dot laser

NASA Astrophysics Data System (ADS)

Korenev, V. V.; Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V.

2014-10-01

Using the analytical approach introduced in our previous papers we analyse the possibilities of optimization of size and structure of active region of semiconductor quantum dot lasers emitting via ground-state optical transitions. It is shown that there are optimal length' dispersion and number of QD layers in laser active region which allow one to obtain lasing spectrum of a given width at minimum injection current. Laser efficiency corresponding to the injection current optimized by the cavity length is practically equal to its maximum value.

Correlation between magnetic and electric field perturbations in the field-aligned current regions deduced from DE 2 observations

NASA Technical Reports Server (NTRS)

Ishii, M.; Sugiura, M.; Iyemori, T.; Slavin, J. A.

1992-01-01

The satellite-observed high correlations between magnetic and electric field perturbations in the high-latitude field-aligned current regions are investigated by examining the dependence of the relationship between Delta-B and E on spatial scale, using the electric and magnetic field data obtained by DE 2 in the polar regions. The results are compared with the Pedersen conductivity inferred from the international reference ionosphere model and the Alfven wave velocity calculated from the in situ ion density and magnetic field measurements.

High voltage design structure for high temperature superconducting device

DOEpatents

Tekletsadik, Kasegn D [Rexford, NY

2008-05-20

In accordance with the present invention, modular corona shields are employed in a HTS device to reduce the electric field surrounding the HTS device. In a exemplary embodiment a fault current limiter module in the insulation region of a cryogenic cooling system has at least one fault current limiter set which employs a first corona shield disposed along the top portion of the fault current limiter set and is electrically coupled to the fault current limiter set. A second corona shield is disposed along the bottom portion of the fault current limiter set and is electrically coupled to the fault current limiter set. An insulation barrier is disposed within the insulation region along at least one side of the fault current limiter set. The first corona shield and the second corona shield act together to reduce the electric field surrounding the fault limiter set when voltage is applied to the fault limiter set.

The Effect of the Leeuwin Current on Offshore Surface Gravity Waves in Southwest Western Australia

NASA Astrophysics Data System (ADS)

Wandres, Moritz; Wijeratne, E. M. S.; Cosoli, Simone; Pattiaratchi, Charitha

2017-11-01

The knowledge of regional wave regimes is critical for coastal zone planning, protection, and management. In this study, the influence of the offshore current regime on surface gravity waves on the southwest Western Australian (SWWA) continental shelf was examined. This was achieved by coupling the three dimensional, free surface, terrain-following hydrodynamic Regional Ocean Modelling System (ROMS) and the third generation wave model Simulating WAves Nearshore (SWAN) using the Coupled Ocean-Atmosphere-WaveSediment Transport (COAWST) model. Different representative states of the Leeuwin Current (LC), a strong pole-ward flowing boundary current with a persistent eddy field along the SWWA shelf edge were simulated and used to investigate their influence on different large wave events. The coupled wave-current simulations were compared to wave only simulations, which represented scenarios in the absence of a background current field. Results showed that the LC and the eddy field significantly impact SWWA waves. Significant wave heights increased (decreased) when currents were opposing (aligning with) the incoming wave directions. During a fully developed LC system significant wave heights were altered by up to ±25% and wave directions by up to ±20°. The change in wave direction indicates that the LC may modify nearshore wave dynamics and consequently alter sediment patterns. Operational regional wave forecasts and hindcasts may give flawed predictions if wave-current interaction is not properly accounted for.

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

NASA Astrophysics Data System (ADS)

Khrabry, A.; Kaganovich, I. D.; Nemchinsky, V.; Khodak, A.

2018-01-01

The atmospheric pressure arcs have recently found application in the production of nanoparticles. The distinguishing features of such arcs are small length and hot ablating anode characterized by intensive electron emission and radiation from its surface. We performed a one-dimensional modeling of argon arc, which shows that near-electrode effects of thermal and ionization non-equilibrium play an important role in the operation of a short arc, because the non-equilibrium regions are up to several millimeters long and are comparable to the arc length. The near-anode region is typically longer than the near-cathode region and its length depends more strongly on the current density. The model was extensively verified and validated against previous simulation results and experimental data. The Volt-Ampere characteristic (VAC) of the near-anode region depends on the anode cooling mechanism. The anode voltage is negative. In the case of strong anode cooling (water-cooled anode) when the anode is cold, temperature and plasma density gradients increase with current density, resulting in a decrease of the anode voltage (the absolute value increases). Falling VAC of the near-anode region suggests the arc constriction near the anode. Without anode cooling, the anode temperature increases significantly with the current density, leading to a drastic increase in the thermionic emission current from the anode. Correspondingly, the anode voltage increases to suppress the emission, and the opposite trend in the VAC is observed. The results of simulations were found to be independent of sheath model used: collisional (fluid) or collisionless model gave the same plasma profiles for both near-anode and near-cathode regions.

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

DOE PAGES

Khrabry, A.; Kaganovich, I. D.; Nemchinsky, V.; ...

2018-01-22

The atmospheric pressure arcs have recently found application in the production of nanoparticles. The distinguishing features of such arcs are small length and hot ablating anode characterized by intensive electron emission and radiation from its surface. We performed a one-dimensional modeling of argon arc, which shows that near-electrode effects of thermal and ionization non-equilibrium play an important role in the operation of a short arc, because the non-equilibrium regions are up to several millimeters long and are comparable to the arc length. The near-anode region is typically longer than the near-cathode region and its length depends more strongly on themore » current density. The model was extensively verified and validated against previous simulation results and experimental data. The Volt-Ampere characteristic (VAC) of the near-anode region depends on the anode cooling mechanism. The anode voltage is negative. In the case of strong anode cooling (water-cooled anode) when the anode is cold, temperature and plasma density gradients increase with current density, resulting in a decrease of the anode voltage (the absolute value increases). Falling VAC of the near-anode region suggests the arc constriction near the anode. Without anode cooling, the anode temperature increases significantly with the current density, leading to a drastic increase in the thermionic emission current from the anode. Correspondingly, the anode voltage increases to suppress the emission, and the opposite trend in the VAC is observed. Here, the results of simulations were found to be independent of sheath model used: collisional (fluid) or collisionless model gave the same plasma profiles for both near-anode and near-cathode regions.« less

Effects of multi-pulsed coaxial helicity injection on dynamics of spherical torus

NASA Astrophysics Data System (ADS)

Kanki, T.; Nagata, M.; Kagei, Y.

2012-10-01

The mechanism to rebuild the magnetic fields and to amplify the currents in the high-q spherical torus (ST) by the multi-pulsed coaxial helicity injection is investigated using the resistive nonlinear 3D-MHD simulations. During the driven phase, the dynamics is almost axisymmetric because the magnetic fluctuation level of n=0 mode compared with other higher modes is much larger. The toroidal current It is effectively amplified due to the merging of plasmoid ejected from the gun region with the pre-existing ST in the confinement region. The poloidal flux is not significantly amplified because the current sheet generated by the merging process does not rapidly decay. The negative toroidal flow vt is then induced in the direction of It around the central open flux column (OFC) region by inductive toroidal electric field Et (=-vzBr) because of the plasmoid ejection. The strong poloidal flow vz (=ErBt) is also driven from the gun to confinement region due to the Lorentz force. As the result of vz, the flow vortices associated with the dynamo effect are caused around the upper confinement region. During the decay phase, the closed field lines are regenerated due to the dissipation of magnetic fluctuations. The helical distortion of the OFC becomes small, and then ordered magnetic field structures without flows are built. Just after turning off the external electric field, the poloidal flow from the confinement to gun region is caused by the pressure gradients. The parallel current density λ concentrated in the OFC diffuses to the core region, but does not relax in the direction of the Taylor state due to the pressure gradients.

Conductance of P2X4 purinergic receptor is determined by conformational equilibrium in the transmembrane region.

PubMed

Minato, Yuichi; Suzuki, Shiho; Hara, Tomoaki; Kofuku, Yutaka; Kasuya, Go; Fujiwara, Yuichiro; Igarashi, Shunsuke; Suzuki, Ei-Ichiro; Nureki, Osamu; Hattori, Motoyuki; Ueda, Takumi; Shimada, Ichio

2016-04-26

Ligand-gated ion channels are partially activated by their ligands, resulting in currents lower than the currents evoked by the physiological full agonists. In the case of P2X purinergic receptors, a cation-selective pore in the transmembrane region expands upon ATP binding to the extracellular ATP-binding site, and the currents evoked by α,β-methylene ATP are lower than the currents evoked by ATP. However, the mechanism underlying the partial activation of the P2X receptors is unknown although the crystal structures of zebrafish P2X4 receptor in the apo and ATP-bound states are available. Here, we observed the NMR signals from M339 and M351, which were introduced in the transmembrane region, and the endogenous alanine and methionine residues of the zebrafish P2X4 purinergic receptor in the apo, ATP-bound, and α,β-methylene ATP-bound states. Our NMR analyses revealed that, in the α,β-methylene ATP-bound state, M339, M351, and the residues that connect the ATP-binding site and the transmembrane region, M325 and A330, exist in conformational equilibrium between closed and open conformations, with slower exchange rates than the chemical shift difference (<100 s(-1)), suggesting that the small population of the open conformation causes the partial activation in this state. Our NMR analyses also revealed that the transmembrane region adopts the open conformation in the state bound to the inhibitor trinitrophenyl-ATP, and thus the antagonism is due to the closure of ion pathways, except for the pore in the transmembrane region: i.e., the lateral cation access in the extracellular region.

Conductance of P2X4 purinergic receptor is determined by conformational equilibrium in the transmembrane region

PubMed Central

Minato, Yuichi; Suzuki, Shiho; Hara, Tomoaki; Kofuku, Yutaka; Kasuya, Go; Fujiwara, Yuichiro; Igarashi, Shunsuke; Suzuki, Ei-ichiro; Nureki, Osamu; Hattori, Motoyuki; Ueda, Takumi; Shimada, Ichio

2016-01-01

Ligand-gated ion channels are partially activated by their ligands, resulting in currents lower than the currents evoked by the physiological full agonists. In the case of P2X purinergic receptors, a cation-selective pore in the transmembrane region expands upon ATP binding to the extracellular ATP-binding site, and the currents evoked by α,β-methylene ATP are lower than the currents evoked by ATP. However, the mechanism underlying the partial activation of the P2X receptors is unknown although the crystal structures of zebrafish P2X4 receptor in the apo and ATP-bound states are available. Here, we observed the NMR signals from M339 and M351, which were introduced in the transmembrane region, and the endogenous alanine and methionine residues of the zebrafish P2X4 purinergic receptor in the apo, ATP-bound, and α,β-methylene ATP-bound states. Our NMR analyses revealed that, in the α,β-methylene ATP-bound state, M339, M351, and the residues that connect the ATP-binding site and the transmembrane region, M325 and A330, exist in conformational equilibrium between closed and open conformations, with slower exchange rates than the chemical shift difference (<100 s−1), suggesting that the small population of the open conformation causes the partial activation in this state. Our NMR analyses also revealed that the transmembrane region adopts the open conformation in the state bound to the inhibitor trinitrophenyl-ATP, and thus the antagonism is due to the closure of ion pathways, except for the pore in the transmembrane region: i.e., the lateral cation access in the extracellular region. PMID:27071117

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khrabry, A.; Kaganovich, I. D.; Nemchinsky, V.

The atmospheric pressure arcs have recently found application in the production of nanoparticles. The distinguishing features of such arcs are small length and hot ablating anode characterized by intensive electron emission and radiation from its surface. We performed a one-dimensional modeling of argon arc, which shows that near-electrode effects of thermal and ionization non-equilibrium play an important role in the operation of a short arc, because the non-equilibrium regions are up to several millimeters long and are comparable to the arc length. The near-anode region is typically longer than the near-cathode region and its length depends more strongly on themore » current density. The model was extensively verified and validated against previous simulation results and experimental data. The Volt-Ampere characteristic (VAC) of the near-anode region depends on the anode cooling mechanism. The anode voltage is negative. In the case of strong anode cooling (water-cooled anode) when the anode is cold, temperature and plasma density gradients increase with current density, resulting in a decrease of the anode voltage (the absolute value increases). Falling VAC of the near-anode region suggests the arc constriction near the anode. Without anode cooling, the anode temperature increases significantly with the current density, leading to a drastic increase in the thermionic emission current from the anode. Correspondingly, the anode voltage increases to suppress the emission, and the opposite trend in the VAC is observed. Here, the results of simulations were found to be independent of sheath model used: collisional (fluid) or collisionless model gave the same plasma profiles for both near-anode and near-cathode regions.« less

Constrained circulation at Endeavour ridge facilitates colonization by vent larvae.

PubMed

Thomson, Richard E; Mihály, Steven F; Rabinovich, Alexander B; McDuff, Russell E; Veirs, Scott R; Stahr, Frederick R

2003-07-31

Understanding how larvae from extant hydrothermal vent fields colonize neighbouring regions of the mid-ocean ridge system remains a major challenge in oceanic research. Among the factors considered important in the recruitment of deep-sea larvae are metabolic lifespan, the connectivity of the seafloor topography, and the characteristics of the currents. Here we use current velocity measurements from Endeavour ridge to examine the role of topographically constrained circulation on larval transport along-ridge. We show that the dominant tidal and wind-generated currents in the region are strongly attenuated within the rift valley that splits the ridge crest, and that hydrothermal plumes rising from vent fields in the valley drive a steady near-bottom inflow within the valley. Extrapolation of these findings suggests that the suppression of oscillatory currents within rift valleys of mid-ocean ridges shields larvae from cross-axis dispersal into the inhospitable deep ocean. This effect, augmented by plume-driven circulation within rift valleys having active hydrothermal venting, helps retain larvae near their source. Larvae are then exported preferentially down-ridge during regional flow events that intermittently over-ride the currents within the valley.

Surface currents on the plasma-vacuum interface in MHD equilibria

NASA Astrophysics Data System (ADS)

Hanson, James

2017-10-01

The VMEC non-axisymmetric MHD equilibrium code can compute free-boundary equilibria. Since VMEC assumes that magnetic fields within the plasma form closed and nested flux surfaces, the plasma-vacuum interface is a flux surface, and the total magnetic field there has no normal component. VMEC imposes this condition of zero normal field using the potential formulation of Merkel, and solves a Neumann problem for the magnetic potential in the exterior region. This boundary condition necessarily admits the possibility of a surface current on the interface. While this surface current may be small in MHD equilibrium, it is readily computed in terms of the magnetic potentials in both the interior and exterior regions, evaluated on the surface. If only the external magnetic potential is known (as in VMEC), then the surface current can be computed from the discontinuity of the tangential field across the interface. Examples of the surface current for VMEC equilibria will be shown for a zero-pressure stellarator equilibrium. Field-line following of the vacuum magnetic field shows magnetic islands within the plasma region.

Evaluation of regional climate simulations over the Great Lakes region driven by three global data sets

Treesearch

Shiyuan Zhong; Xiuping Li; Xindi Bian; Warren E. Heilman; L. Ruby Leung; William I. Jr. Gustafson

2012-01-01

The performance of regional climate simulations is evaluated for the Great Lakes region. Three 10-year (1990-1999) current-climate simulations are performed using the MM5 regional climate model (RCM) with 36-km horizontal resolution. The simulations employed identical configuration and physical parameterizations, but different lateral boundary conditions and sea-...

NATIONAL GEODATABASE OF TIDAL STREAM POWER RESOURCE IN USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Brennan T; Neary, Vincent S; Stewart, Kevin M

2012-01-01

A geodatabase of tidal constituents is developed to present the regional assessment of tidal stream power resource in the USA. Tidal currents are numerically modeled with the Regional Ocean Modeling System (ROMS) and calibrated with the available measurements of tidal current speeds and water level surfaces. The performance of the numerical model in predicting the tidal currents and water levels is assessed by an independent validation. The geodatabase is published on a public domain via a spatial database engine with interactive tools to select, query and download the data. Regions with the maximum average kinetic power density exceeding 500 W/m2more » (corresponding to a current speed of ~1 m/s), total surface area larger than 0.5 km2 and depth greater than 5 m are defined as hotspots and documented. The regional assessment indicates that the state of Alaska (AK) has the largest number of locations with considerably high kinetic power density, followed by, Maine (ME), Washington (WA), Oregon (OR), California (CA), New Hampshire (NH), Massachusetts (MA), New York (NY), New Jersey (NJ), North and South Carolina (NC, SC), Georgia (GA), and Florida (FL).« less

Public Notice Distribution List for CAA Permits in the Mountains and Plains Region (Region 8)

EPA Pesticide Factsheets

Clean Air Act public notice notification list - subscription form. Currently this is for EPA Region 8 states Colorado, Utah, Wyoming, Montana, North Dakota and South Dakota, and 27 Indian Reservations

Regional Information System for Educators: Installation and Evaluation.

ERIC Educational Resources Information Center

Kromer, Charles

This document describes the installation and evaluation of the Regional Information System within the Michigan-Ohio Regional Educational Laboratory (MOREL). MOREL is an agency established to develop and test alternatives to current educational practice under Title IV of ESEA. The Regional Information System was established to provide referrals to…

GROUNDWATER DATA - CERCLA NPL SITES - USEPA REGION 10

EPA Science Inventory

Information has been compiled for a subgroup of the National Priority List (NPL) Superfund sites located in Region 10. You can also view the current list of all NPL Sites in Region 10 along with general reference maps for the region with enlarged views for the Puget Sound, Portla...

Nonguiding Center Motion and Substorm Effects in the Magnetotail

NASA Technical Reports Server (NTRS)

Kaufmann, Richard L.; Kontodinas, Ioannis D.; Ball, Bryan M.; Larson, Douglas J.

1997-01-01

Thick and thin models of the middle magnetotail were developed using a consistent orbit tracing technique. It was found that currents carried near the equator by groups of ions with anisotropic distribution functions are not well approximated by the guiding center expressions. The guiding center equations fail primarily because the calculated pressure tensor is not magnetic field aligned. The pressure tensor becomes field aligned as one moves away from the equator, but here there is a small region in which the guiding center equations remain inadequate because the two perpendicular components of the pressure tensor are unequal. The significance of nonguiding center motion to substorm processes then was examined. One mechanism that may disrupt a thin cross-tail current sheet involves field changes that cause ions to begin following chaotic orbits. The lowest-altitude chaotic region, characterized by an adiabaticity parameter kappa approx. equal to 0.8, is especially important. The average cross-tail particle drift is slow, and we were unable to generate a thin current sheet using such ions. Therefore, any process that tends to create a thin current sheet in a region with kappa approaching 0.8 may cause the cross-tail current to get so low that it becomes insufficient to support the lobes. A different limit may be important in resonant orbit regions of a thin current sheet because particles reach a maximum cross-tail drift velocity. If the number of ions per unit length decreases as the tail is stretched, this part of the plasma sheet also may become unable to carry the cross-tail current needed to support the lobes. Thin sheets are needed for both resonant and chaotic orbit mechanisms because the distribution function must be highly structured. A description of current continuity is included to show how field aligned currents can evolve during the transition from a two-dimensional (2-D) to a 3-D configuration.

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. I - Introduction and methods

NASA Technical Reports Server (NTRS)

Canfield, Richard C.; De La Beaujardiere, J.-F.; Fan, Yuhong; Leka, K. D.; Mcclymont, A. N.; Metcalf, Thomas R.; Mickey, Donald L.; Wuelser, Jean-Pierre; Lites, Bruce W.

1993-01-01

Electric current systems in solar active regions and their spatial relationship to sites of electron precipitation and high-pressure in flares were studied with the purpose of providing observational evidence for or against the flare models commonly discussed in the literature. The paper describes the instrumentation, the data used, and the data analysis methods, as well as improvements made upon earlier studies. Several flare models are overviewed, and the predictions yielded by each model for the relationships of flares to the vertical current systems are discussed.

Electron transport property of cobalt-centered porphyrin-armchair graphene nanoribbon (AGNR) junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mondal, Rajkumar; Sarkar, Utpal, E-mail: utpalchemiitkgp@yahoo.com

2015-06-24

We have investigated the electron transport properties of Cobalt-centered (Co-centered) porphyrin molecule using the density functional theory and non-equilibrium greens function method. Here we have reported transmission coefficient as well as current voltage characteristics of Co-centered porphyrine molecule connected between armchair graphene nanoribbons. It has been found that at low bias region i.e., 0 V to 0.3 V it does not contribute any current. Gradual increase of bias voltage results different order of magnitude of current in different bias region.

Basic corrections to predictions of solar cell performance required by nonlinearities

NASA Technical Reports Server (NTRS)

Lindholm, F. A.; Fossum, J. G.; Burgess, E. L.

1976-01-01

The superposition principle is used to derive the approximation that the current-voltage characteristic of an illuminated solar cell is the dark current-voltage characteristic shifted by the short-circuit photocurrent. The derivation requires the linearity of the boundary value problems that underlie the electrical characteristics. The shifting approximation is invalid if considerable photocurrent and considerable dark current both occur within the junction space-charge region; it is invalid also if sizable series resistance is present or if high-injection concentrations of holes and electrons exist within the quasi-neutral regions.

Dual control active superconductive devices

DOEpatents

Martens, Jon S.; Beyer, James B.; Nordman, James E.; Hohenwarter, Gert K. G.

1993-07-20

A superconducting active device has dual control inputs and is constructed such that the output of the device is effectively a linear mix of the two input signals. The device is formed of a film of superconducting material on a substrate and has two main conduction channels, each of which includes a weak link region. A first control line extends adjacent to the weak link region in the first channel and a second control line extends adjacent to the weak link region in the second channel. The current flowing from the first channel flows through an internal control line which is also adjacent to the weak link region of the second channel. The weak link regions comprise small links of superconductor, separated by voids, through which the current flows in each channel. Current passed through the control lines causes magnetic flux vortices which propagate across the weak link regions and control the resistance of these regions. The output of the device taken across the input to the main channels and the output of the second main channel and the internal control line will constitute essentially a linear mix of the two input signals imposed on the two control lines. The device is especially suited to microwave applications since it has very low input capacitance, and is well suited to being formed of high temperature superconducting materials since all of the structures may be formed coplanar with one another on a substrate.