988 research outputs found
Compatible Discrete Series
Several very interesting results connecting the theory of abelian ideals of
Borel subalgebras, some ideas of D. Peterson relating the previous theory to
the combinatorics of affine Weyl groups, and the theory of discrete series are
stated in a recent paper (\cite{Ko2}) by B. Kostant. In this paper we provide
proofs for most of Kostant's results extending them to -nilpotent ideals
and develop one direction of Kostant's investigation, the compatible discrete
series.Comment: AmsTex file, 27 Pages; minor corrections; to appear in Pacific
Journal of Mathematic
On the structure of Borel stable abelian subalgebras in infinitesimal symmetric spaces
Let g=g_0+g_1 be a Z_2-graded Lie algebra. We study the posets of abelian
subalgebras of g_1 which are stable w.r.t. a Borel subalgebra of g_0. In
particular, we find out a natural parametrization of maximal elements and
dimension formulas for them. We recover as special cases several results of
Kostant, Panyushev, Suter.Comment: Latex file, 35 pages, minor corrections, some examples added. To
appear in Selecta Mathematic
Closed-Loop Targeted Memory Reactivation during Sleep Improves Spatial Navigation
Sounds associated with newly learned information that are replayed during non-rapid eye movement (NREM) sleep can improve recall in simple tasks. The mechanism for this improvement is presumed to be reactivation of the newly learned memory during sleep when consolidation takes place. We have developed an EEG-based closed-loop system to precisely deliver sensory stimulation at the time of down-state to up-state transitions during NREM sleep. Here, we demonstrate that applying this technology to participants performing a realistic navigation task in virtual reality results in a significant improvement in navigation efficiency after sleep that is accompanied by increases in the spectral power especially in the fast (12\u201315 Hz) sleep spindle band. Our results show promise for the application of sleep-based interventions to drive improvement in real-world tasks
Potencialidad de la cosecha y rendimiento industrial de bosques de Nothofagus antarctica en Tierra del Fuego (Argentina)
MartÃnez Pastur, G.; Lencinas, M.V. CADIC-CONICET. Casilla 92 (9410) Ushuaia, Argentina.
Cellini, J.M. Cátedra de BiometrÃa. Universidad Nacional de La Plata, La Plata, Argentina.
Peri, P. UNPA-INTA-CONICET, RÃo Gallegos, Argentina.La propuesta silvÃcola para bosques de Nothofagus antarctica es el manejo silvopastoril,
siendo la limitante para su implementación la falta de mercado para los productos
madereros generados durante su aplicación. En Tierra del Fuego (Argentina) existen más de
180 mil ha, de las cuales 23% pertenecen a sitios medio-altos (>11,5 m de altura). El
potencial de cosecha y el rendimiento industrial fueron analizados en 12 parcelas de 500
m², cuya área basal fue 58,7±11,5 m².ha-1 (promedio ± desvÃo estándar) con un remanente
de 29,9±7,6 m².ha-1 luego de la aplicación de raleos. El volumen cosechado fue 102,2±29,0
m3.ha-1. El rendimiento en aserradero (127 trozas en 20 paquetes de muestreo) varió con la
calidad y el tamaño de las trozas. Trozas >30 cm presentaron rendimientos del 34, 10, y 4%
para calidades alta, media y baja, respectivamente. Trozas <30 cm de alta calidad
presentaron rendimientos del 27%, y 10% para la de calidad media. Las trozas >30 cm de
mejor calidad produjeron 9% de tablones, 21% de tablas, 49% de tirantes, 5% de madera
corta y 16% de madera para pallet y las trozas <30 cm produjeron 0-1, 8-11%, 30-53%, 7-
16% y 32-43%, respectivamente. Los rendimientos sugieren la posibilidad de incorporar al
aserrado solo trozas de alta calidad de cualquier diámetro, lo que representa rendimientos
de cosecha de 50,0±27,9 m3.ha-1 para bosques de calidad de sitio media-alta. Considerando
solo el punto de vista maderero, los rendimientos obtenidos pueden solventar la aplicación
de los tratamientos silvopastoriles con ingresos brutos de hasta U$S 3500 por hectárea.Proyecto PID2005 35648 (SECYT-Argentina
Root polytopes and abelian ideals
We study the root polytope of a finite irreducible
crystallographic root system using its relation with the abelian ideals
of a Borel subalgebra of a simple Lie algebra with root system . We
determine the hyperplane arrangement corresponding to the faces of codimension
2 of and analyze its relation with the facets of . For of type or , we show that the orbits of some
special subsets of abelian ideals under the action of the Weyl group
parametrize a triangulation of . We show that this
triangulation restricts to a triangulation of the positive root polytope
.Comment: 41 pages, revised version, accepted for publication in Journal of
Algebraic Combinatoric
The c4 atriplex halimus vs. The c3 atriplex hortensis: Similarities and differences in the salinity stress response
open7noSoil properties and the ability to sustain agricultural production are seriously impaired by salinity. The cultivation of halophytes is seen as a solution to cope with the problem. In this framework, a greenhouse pot experiment was set up to assess salinity response in the perennial C4 species Atriplex halimus, and in the following three cultivars of the annual C3 Atriplex hortensis: green, red, and scarlet. The four genotypes were grown for 35 days with water salinity (WS) ranging from 0 to 360 mM NaCl. Plant height and fresh weight (FW) increased at 360 vs. 0 WS. The stomatal conductance (GS) and transpiration rate (E) were more severely affected by salinity in the C4 A. halimus than in the C3 species A. hortensis. This was reflected in a lower leaf water potential indicating stronger osmotic adjustment, and a higher relative water content associated with more turgid leaves, in A. halimus than A. hortensis. In a PCA including all the studied traits, the GS and E negatively correlated to the FW, which, in turn, positively correlated with Na concentration and intrinsic water use efficiency (iWUE), indicating that reduced gas exchange associated with Na accumulation contributed to sustain iWUE under salinity. Finally, FTIR spectroscopy showed a reduced amount of pectin, lignin, and cellulose under salinity, indicating a weakened cell wall structure. Overall, both species were remarkably adapted to salinity: From an agronomic perspective, the opposite strategies of longer vs. faster soil coverage, involved by the perennial A. halimus vs. the annual A. hortensis cv. scarlet, are viable natural remedies for revegetating marginal saline soils and increasing soil organic carbon.openCalone R.; Cellini A.; Manfrini L.; Lambertini C.; Gioacchini P.; Simoni A.; Barbanti L.Calone R.; Cellini A.; Manfrini L.; Lambertini C.; Gioacchini P.; Simoni A.; Barbanti L
Endocrine and metabolic complications in children and adolescents with Sickle Cell Disease: An Italian cohort study
Background: Children with Sickle Cell Disease (SCD) show endocrine complications and metabolic alterations. The physiopathology of these conditions is not completely understood: iron overload due to chronic transfusions, ischemic damage, and inflammatory state related to vaso-occlusive crises may be involved. Aims of this study were to evaluate the growth pattern, endocrine complications, and metabolic alterations and to detect the relationship between these conditions and the SCD severity in affected children and adolescents. Methods: Fifty-two children and adolescents with SCD [38 homozygous sickle hemoglobin (HbSS) and 14 heterozygous sickle hemoglobin (HbSC); age range 3-18 years] were recruited. Anthropometric [height, body mass index (BMI), arm span, sitting height, target height (TH), and pubertal status] and laboratory [blood cell counts, hemolysis indices, metabolic and nutritional status indices and hormonal blood levels] data were evaluated. The SCD severity was defined according to hematological and clinical parameters. Results: Height-SDS adjusted for TH and BMI-SDS were significantly higher in HbSC children than in HbSS ones. Forty-eight out of 52 patients (92%) had at least one metabolic and/or endocrine alteration: insufficiency/deficiency of vitamin D (84.7%), insulin resistance (11.5%), growth hormone deficiency (3.8%), subclinical hypothyroidism (3.8%), and hypogonadism (1.9%). Levels of vitamin D were significantly and negatively correlated with clinical indicators of the SCD severity. Subjects with HbSS genotype show significant lower levels of both insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein 3 than children with HbSC. In the study population IGF-1 values were significantly and positively correlated with Hb and negatively with lactate dehydrogenase. Conclusions: Metabolic alterations and endocrine complications are very common in children and adolescents with SCD. A regular follow-up is necessary to identify subjects at risk for complications to precociously start an appropriate treatment and to improve the quality of life of SCD patients
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