993 research outputs found
Partition Functions of Pure Spinors
We compute partition functions describing multiplicities and charges of
massless and first massive string states of pure-spinor superstrings in
3,4,6,10 dimensions. At the massless level we find a spin-one gauge multiplet
of minimal supersymmetry in d dimensions. At the first massive string level we
find a massive spin-two multiplet. The result is confirmed by a direct analysis
of the BRST cohomology at ghost number one. The central charges of the pure
spinor systems are derived in a manifestly SO(d) covariant way confirming that
the resulting string theories are critical. A critical string model with
N=(2,0) supersymmetry in d=2 is also described.Comment: LaTex, 30 p
Is there a direct role for erythrocytes in the immune response?
Erythrocytes are highly abundant circulating cells in the vertebrates, which, with the notable exception of mammals, remain nucleated throughout the entire life cycle. The major function associated with these cells is respiratory gas exchange however other functions including interaction with the immune system have been attributed to these cells. Many viral, prokaryotic and eukaryotic pathogens directly target this cell type and across the vertebrate group a significant number of related pathologies have been reported. Across the primary literature mechanisms of interaction, invasion and replication between viruses and erythrocytes have been well described however the functional response of the erythrocyte has been poorly studied. A fragmented series of reports spanning the vertebrates suggests that these cells are capable of functional responses to viral infection. In contrast, in-depth proteomic studies using human erythrocytes have strongly progressed throughout the past decade providing a rich source of information related to protein expression and potential function. Furthermore information at the gene expression level is becoming available. Here we provide a review of erythrocyte-pathogen interactions, erythrocyte functions in immunity and propose in light of recent -omics research that the nucleated erythrocytes may have a direct role in the immune response
Agronomic characterization of a collection of avocado varieties (Persea americana Miller) at the Subestacion Fraijanes, Alajuela, Costa Rica
Este estudio se realizó durante el año 2001, se registraron las caracterÃsticas del árbol, fruto y semilla de una colección de 122 árboles con 26 variedades de aguacate conservados en el Banco de Germoplasma de la Subestación Experimental Fraijanes (SEF) de la Universidad de Costa Rica (UCR). La mayorÃa de los árboles se plantaron en el periodo 1992-1993. Las 19 variables registradas fueron mes de cosecha, hábito de crecimiento, cantidad de follaje, altura del árbol, número de frutos por árbol, forma del fruto, longitud del fruto, anchura del fruto, peso del fruto, color de la cáscara, apariencia externa de la cáscara, color de la pulpa, presencia de fibras en pulpa, textura de la pulpa, sabor de la pulpa, peso de la semilla e indicador de cosecha. En general, las variedades mostraron diferencias muy marcadas en cuanto a producción de frutos: Choquette, Ettinger, Horshim, Itzamna, Jim y Zutano(50 frutos por árbol); Edranol, Kahalu y Simpson(100 frutos por árbol); Fuerte y Reed(400 frutos por árbol) y Fujikawa, Hass, Pinkerton, y Guatemala (700 frutos por árbol). El peso de los frutos varia desde 187,6 g de la variedad Edranol hasta 348,8 g para la variedad Fujikawa. La variedad Hasstuvo el menor peso de la semilla (17,3 g), mientras que Choquette, el mayor (58,8 g). El sabor de pulpa tuvo diferencias también muy marcadas ya que solo cinco variedades de las quince que produjeron frutos (Fujikawa, Kahalu, Pinkerton Fuertey Hass) mostraron el mejor sabor; el resto de las variedades alcanzaron un sabor de pulpa inferior. Con base en el rendimiento, la calidad y el sabor, se obtuvo que, para las condiciones de esta zona, además de las variedades comerciales de Hass y Fuerte, otras tres variedades (Pinkerton, Fujikaway Kahalu) mostraron indicios de un buen potencial bajo sistemas de producción agroforestal.This study was conducted using data from the tree, fruit and seed characteristics of the avocado live collection of one hundred twenty two trees (twenty six varieties) grown at the University of Costa Rica avocado germplasm bank, located at the Fraijanes Experiment Station. The nineteen recorded variables were: month of harvest, growth habit, amount of foliage, tree height, number of fruits per tree, fruit shape, fruit length, fruit width, fruit weight, peel color, external peel appearance, pulp color, presence of fiber in the pulp, pulp texture, pulp flavor, seed weight and harvest indicator. In general, the varieties showed great differences on fruit production: Choquette, Ettinger, Horshim, Itzamna, Jim and Zutano had a production of 50 fruit per tree; Edranol, Kahalu and Simpson produced 100 fruit per tree; Fuerte and Reed had 400 fruits per tree and finally, Fujikawa, Hass, Pinkerton and Guatemala attained a production of 700 fruit per tree. The Edranol variety had the lowest fruit weight with 187.6 g while the Fujikawa variety had the largest mean fruit weight with 348.8 g. The Hassvariety had the lowest seed weight with 17.3 g and the highest seed weight was for the Choquettevariety with 58.8 g. There were large differences between varieties for pulp flavor, only five varieties (Fujikawa, Pinkerton, Kahalu, Hass and Fuerte) showed the best flavor, the rest of the varieties had a lower pulp flavor. From the studied characteristics, it is possible to conclude that additionally to the Hass and Fuerte varieties, three good genotypes (Pinkerton, Fujikawa and Kahalu) were distinguished with high potential to be grown commercially under an agro- forestry production system.UCR::VicerrectorÃa de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental AgrÃcola Fabio Baudrit Moreno (EEAFBM
El Niño–Southern Oscillation (ENSO)-driven hypersedimentation in the Poechos Reservoir, northern Peru
Although extreme El Niño events (EENEs) have always impacted
hydrological anomalies and sediment transport in South America, their
intensification by global warming and their association with changes in
human activities and land cover after humid periods may lead to the
acceleration of sediment transfers in river systems and dam reservoirs. This
situation may threaten soil and water resources in arid and semiarid regions
highly dependent on water originating from large dams. In this study, we
investigated the sediment sequence accumulated in the Poechos Reservoir
(northern Peru) and provided a retrospective reconstruction of the
interactions of El Niño–Southern Oscillation (ENSO), agricultural
practices and vegetation cover changes with sediment dynamics (1978–2019). To
this end, a sediment core was dated and characterized by physical and
chemical analyses (e.g., scanner tomography, X-ray fluorescence, particle
size analysis) to estimate the evolution of sedimentation rates and
changes in sediment sources during the last 5Â decades.
Sediment tracing results indicated the occurrence of changes in sediment
sources associated with positive and negative phases of the Eastern Pacific
index with a greater contribution of the lowland dry-forest area in
comparison to that of the Andean area to sediment during the El Niño
events (mean contribution of 76 %; up to 90 % during the coastal El
Niño events (CENEs) of 2016–2017). This source contribution was mostly
controlled by the stationary rainfall occurring during the EENEs in the lowland dry-forest area characterized by a low vegetation cover. Overall, after an extreme phase of ENSO, like after the
EENE 1982–1983, the normal discharges and persistent sediment supplies from
the middle- and upper-catchment parts led to river aggradation and the
storage of substantial amounts of sediment in alluvial plains. In the
absence of a significant EENE between 1983 and 1997, the large volume of
sediment stored in the alluvial plains was exported by the EENE 1997–1998
resulting in an increase in sedimentation rate of 140 % after 1997 with
a significant aggradation of the deltaic zone of the reservoir. In addition
to the impact of extreme climate events on sediment dynamics, the
development of agriculture along the riverine system after an extreme phase
of ENSO increased the availability of sediments in the main channel of the
rivers, easily transported by the next EENE. This study suggests that
intensification of human activities associated with a higher frequency of
extreme rainfall events amplified the quantity of sediment transported by
the river system, which will significantly decrease the lifespan of the
reservoir, which is essential to meeting the freshwater demands of the farmers and the
populations living in this arid and semiarid region.</p
Comparison between conjugated linoleic acid and essential fatty acids in preventing oxidative stress in bovine mammary epithelial cells
Some in vitro and in vivo studies have demonstrated protective effects of conjugated linoleic acid (CLA) isomers against oxidative stress and lipid peroxidation. However, only a few and conflicting studies have been conducted showing the antioxidant potential of essential fatty acids. The objectives of the study were to compare the effects of CLA to other essential fatty acids on the thiol redox status of bovine mammary epithelia cells (BME-UV1) and their protective role against oxidative damage on the mammary gland by an in vitro study. The BME-UV1 cells were treated with complete medium containing 50 μM of cis-9,trans-11 CLA, trans-10,cis-12 CLA, α-linolenic acid, γ-linolenic acid, and linoleic acid. To assess the cellular antioxidant response, glutathione, NADPH, and γ-glutamyl-cysteine ligase activity were measured 48 h after addition of fatty acids (FA). Intracellular reactive oxygen species and malondialdehyde production were also assessed in cells supplemented with FA. Reactive oxygen species production after 3 h of H2O2 exposure was assessed to evaluate and to compare the potential protection of different FA against H2O2-induced oxidative stress. All FA treatments induced an intracellular GSH increase, matched by high concentrations of NADPH and an increase of γ-glutamyl-cysteine ligase activity. Cells supplemented with FA showed a reduction in intracellular malondialdehyde levels. In particular, CLA isomers and linoleic acid supplementation showed a better antioxidant cellular response against oxidative damage induced by H2O2 compared with other FA
The use of straw mulch as a strategy to prevent extreme soil erosion rates in citrus orchard. A Rainfall simulation approach
Not only the Sahel (Haregeweyn et al., 2013), the deforested land (Borelli et al., 2013) the chinese Plateau are
affected by intense soil erosion rates (Zhao et al., 2013). Soil erosion affect agriculture land (Cerdà et al., 2009),
and citrus orchards are being seeing as one of the crops with the highest erosion rates due to the managements
that avoid the catch crops, weeds or litter. Example of the research carried out on citrus orchards is found in the
Mediterranean (Cerdà and Jurgensen, 2008; 2009; Cerdà et al., 2009a; 2009b; Cerdà et al., 2011; 2012) and in
China (Wu et al., 1997; Xu et al., 2010; Wang et al., 2011; Wu et al., 2011; Liu et al., 2011; Lü et al., 2011; Xu et
al., 2012), and they confirm the non sustainable soil losses measured. The land management in citrus plantations
results in soil degradation too (Lu et al., 1997; Lü et al., 2012; Xu et al., 2012). The use of cover crops to reduce
the soil losses (Lavigne et al., 2012; Le Bellec et al., 2012) and the use of residues such as dried citrus peel has
been found successful. There is a need to find new plants or residues to protect the soils on citrus orchards.
Agriculture produces a high amount of residues. The pruning can contribute with a valuable source of nutrients
and a good soil protection. The leaves of the trees, and some parts of the plants, once harvest can contribute to
reduce the soil losses. Due to the mechanization of the agriculture, and the reduction of the draft animals (mainly
horses, mules, donkeys and oxen) the straw is being a residue instead of a resource. The Valencia region is the
largest producer of citrus in Europe, and the largest exporter in the world. This citrus production region is located
in the eastern cost of Spain where we can find the rice production area of the l’Albufera Lagoon paddy fields,
the third largest production region in Spain. This means, a rice production region surrounded by the huge citrus
production region. There, the rice straw is not used in the paddy fields after harvesting and the straw is being as
a residue that damages the air quality when burnt, the water quality due to the decomposition and the methane
production, and is not accepted in the field by the farmers. This is a new problem as few years ago the rice straw
was use for animal feeding. Many attempts were developed in the last decade to remove and use the straw to avoid
fires and water pollution (Iranzo et al., 2004; Silvestre et al., 2013).
Our goal is to test if a residue such as the rice straw can be transformed as a resource: soil erosion control. Straw
has been seen as a very efficient to reduce the water losses in agriculture land (GarcÃa Moreno et al., 2013), the
soil losses in fire affected land (Robichaud et al., 2013a; 2013b; Fernandez and Vega, 2014), and soil properties
(GarcÃa Orenes et al., 2009; 2010; Jordán et al., 2010; GarcÃa Orenes 2012).
Rainfall simulations under 55 mm h-1 rainfall intensity during one hour on 0,25 m2 plots were carried out on plots
paired plots: bare and covered with straw. The plots covered with straw had different straw mulch cover: from 10
to 100 % cover and from 0,005 g m2 to 300 g m2. The results show a positive effect of the straw cover that show
an exponential relation between the straw cover and weight with the sediment yield.
Acknowledgements
The research projects GL2008-02879/BTE, LEDDRA 243857 and RECARE supported this research
The effect of temperature on mobility of Angiostrongylus costaricensis third stage larvae
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