1,903 research outputs found
The formation of the solar system
The solar system started to form about 4.56 Gyr ago and despite the long
intervening time span, there still exist several clues about its formation. The
three major sources for this information are meteorites, the present solar
system structure and the planet-forming systems around young stars. In this
introduction we give an overview of the current understanding of the solar
system formation from all these different research fields. This includes the
question of the lifetime of the solar protoplanetary disc, the different stages
of planet formation, their duration, and their relative importance. We consider
whether meteorite evidence and observations of protoplanetary discs point in
the same direction. This will tell us whether our solar system had a typical
formation history or an exceptional one. There are also many indications that
the solar system formed as part of a star cluster. Here we examine the types of
cluster the Sun could have formed in, especially whether its stellar density
was at any stage high enough to influence the properties of today's solar
system. The likelihood of identifying siblings of the Sun is discussed.
Finally, the possible dynamical evolution of the solar system since its
formation and its future are considered.Comment: 36 pages, 7 figures, invited review in Physica Script
Universally diverging Grueneisen parameter and the magnetocaloric effect close to quantum critical points
At a generic quantum critical point, the thermal expansion is more
singular than the specific heat . Consequently, the "Gr\"uneisen ratio'',
\GE=\alpha/c_p, diverges. When scaling applies, \GE \sim T^{-1/(\nu z)} at
the critical pressure , providing a means to measure the scaling
dimension of the most relevant operator that pressure couples to; in the
alternative limit and , \GE \sim \frac{1}{p-p_c} with a
prefactor that is, up to the molar volume, a simple {\it universal} combination
of critical exponents. For a magnetic-field driven transition, similar
relations hold for the magnetocaloric effect .
Finally, we determine the corrections to scaling in a class of metallic quantum
critical points.Comment: 4 pages, 1 figure; general discussion on how the Grueneisen exponent
measures the scaling dimension of the most relevant operator at any QCP is
expande
Monitoramento do ácido chiquímico em plantas de citrus sob diferentes sistemas de manejo de plantas daninhas.
Glifosato; Planta daninha
Análise da expressão diferencial de fatores de elongação e transerição de tomateiros resistentes e suscetíveis infectados com Tomato chlorotic mottle virus.
O objetivo desse trabalho foi analisar a expressão de genes da família dos fatores de elongação e de transcrição do hospedeiro durante a infecção viral por tomato chlorotic mottle virus (ToCMoV) em isolinhas de tomateiros resistentes (LAM157) e suscetíveis (Santa Clara).Resumo 253-1
Magnetoresistivity and Complete in
Detailed magneto-transport data on dense wires of are reported for
applied magnetic fields up to 18 T. The temperature and field dependencies of
the electrical resistivity are consistent with behaving like a simple
metal and following a generalized form of Kohler's rule. In addition, given the
generally high values and narrow resistive transition widths associated
with synthesized in this manner, combined with applied magnetic fields
of up to 18 T, an accurate and complete curve could be determined.
This curve agrees well with curves determined from lower field measurements on
sintered pellets and wires of . is linear in over a wide
range of temperature (7 K 32 K) and has an upward curvature for
close to . These features are similar to other high , clean limit,
boron-bearing intermetallics: and .Comment: minor changes in styl
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