2,354 research outputs found
Two generalizations of the PRV conjecture
Let G be a complex connected reductive group. The PRV conjecture, which was
proved independently by S. Kumar and O. Mathieu in 1989, gives explicit
irreducible submodules of the tensor product of two irreducible G-modules. This
paper has three aims. First, we simplify the proof of the PRV conjecture, then
we generalize it to other branching problems. Finally, we find other
irreducible components of the tensor product of two irreducible G-modules that
appear for "the same reason" as the PRV ones
Dielectric anomalies and spiral magnetic order in CoCr2O4
We have investigated the structural, magnetic, thermodynamic, and dielectric
properties of polycrystalline CoCrO, an insulating spinel exhibiting
both ferrimagnetic and spiral magnetic structures. Below = 94 K the
sample develops long-range ferrimagnetic order, and we attribute a sharp phase
transition at 25 K with the onset of long-range spiral magnetic
order. Neutron measurements confirm that while the structure remains cubic at
80 K and at 11 K; there is complex magnetic ordering by 11 K. Density
functional theory supports the view of a ferrimagnetic semiconductor with
magnetic interactions consistent with non-collinear ordering. Capacitance
measurements on CoCrO, show a sharp decrease in the dielectric constant
at , but also an anomaly showing thermal hysteresis falling between
approximately = 50 K and = 57 K. We tentatively attribute the
appearance of this higher temperature dielectric anomaly to the development of
\textit{short-range} spiral magnetic order, and discuss these results in the
context of utilizing dielectric spectroscopy to investigate non-collinear
short-range magnetic structures.Comment: & Figure
Predicting morphotropic phase boundary locations and transition temperatures in Pb- and Bi-based perovskite solid solutions from crystal chemical data and first-principles calculations
Using data obtained from first-principles calculations, we show that the
position of the morphotropic phase boundary (MPB) and transition temperature at
MPB in ferroelectric perovskite solutions can be predicted with quantitative
accuracy from the properties of the constituent cations. We find that the mole
fraction of PbTiO at MPB in Pb(BB)O-PbTiO,
BiBO-PbTiO and Bi(BB)O-PbTiO exhibits a linear
dependence on the ionic size (tolerance factor) and the ionic displacements of
the B-cations as found by density functional theory calculations. This
dependence is due to competition between the local repulsion and A-cation
displacement alignment interactions. Inclusion of first-principles displacement
data also allows accurate prediction of transiton temperatures at the MPB. The
obtained structure-property correlations are used to predict morphotropic phase
boundaries and transition temperatures in as yet unsynthesized solid solutions.Comment: Accepted for publication in J. Appl. Phy
The effect of calcium channel blockers against scopolamine induced cognitive impairment and oxidative stress
Background: the present work has been planned to find out the effect of calcium channel blockers on learning and memory. there are numerous reports indicating that calcium channel blockers (CCBS) impair memory and learning and on the other side there are reports indicating that CCBS improve memory and learning .This contradictory reports led us to investigate the effect of CCBS on memory and learning by taking three different types of calcium channel blockers verapamil, nimodipine and diltiazem.Methods: The methods used were elevated plus maze and novel recognition object tests. Ten groups of animals were treated with CCBS and scopolamine. Both prophylactic and curative studies were carried out.Results: It was evident from our studies that the CCBS effectively antagonized the scopolamine induced cognitive impairment in the paradiagms studied. The inflex ratio and novel object discrimination index also increased indicating decrease in the trancefer latencies. CCBS showed good protection against scopolamine induced cognitive.Conclusions: In our Studies we observed that verapamil was good in prophylactic studies and diltiazem in curative studies
Nuevo puente, en Ceilán
Sobre el rÃo Kelani Ganga, situado al norte de la ciudad de Colombo, capital de Ceilán, se ha construido un nuevo puente de hormigón armado, de diez tramos, 275 m de longitud total, 24 m de anchura de tablero y calzada de 18 m de ancho, que se ha subdivido en seis bandas de circulación, tres para cada una de las dos direcciones de tráfico
Warragamba. Sydney, Australia
El pantano de Warragamba, cuyo objeto es el de producir energÃa hidroeléctrica en su primera fase de explotación y solamente agua potable cuando las necesidades de ésta asà lo requieran, se haya situado en las proximidades de Sydney (Australia). Su extensa cuenca está constituida por una serie de rÃos en cuyas cabeceras se han construido diques de retención, que no solamente almacenan grandes cantidades de agua, sino que sirven parcialmente para la regularización de caudales, función de gran interés en esta zona donde las avenidas, seguidas de extensas inundaciones, se hacen sentir con relativa frecuencia
Reactor atómico, Trombay
El reactor de Trombay, denominado reactor Canadá-India, e instalado en las proximidades de Bombay (India), constituye el proyecto de mayor amplitud construido con la colaboración internacional y dedicado al empleo de la energÃa atómica para usos de carácter puramente pacÃficos
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