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

Bose-Einstein Condensation of S = 1 Ni spin degrees of freedom in NiCl2-4SC(NH2)2

It has recently been suggested that the organic compound NiCl$_2$-4SC(NH$_2$)$_2$ (DTN) exhibits Bose-Einstein Condensation (BEC) of the Ni spin degrees of freedom for fields applied along the tetragonal c-axis. The Ni spins exhibit 3D XY-type antiferromagnetic order above a field-induced quantum critical point at $H_{c1} \sim 2$ T. The Ni spin fluid can be characterized as a system of effective bosons with a hard-core repulsive interaction in which the antiferromagnetic state corresponds to a Bose-Einstein condensate (BEC) of the phase coherent $S = 1$ Ni spin system. We have investigated the the high-field phase diagram and the occurrence of BEC in DTN by means of specific heat and magnetocaloric effect measurements to dilution refrigerator temperatures. Our results indicate that a key prediction of BEC is satisfied; the magnetic field-temperature quantum phase transition line $H_c(T)-H_{c1} \propto T^\alpha$ approaches a power-law at low temperatures, with an exponent $\alpha = 1.47 \pm 0.06$ at the quantum critical point, consistent with the BEC theory prediction of $\alpha = 1.5$.Comment: 4 pages, 4 figure

Atributos do solo impactados por cultivos sucessivos de arroz de terras altas.

O objetivo deste trabalho foi determinar, utilizando esse tipo de análise, quais atributos de um Latossolo Vermelho de Cerrado são mais impactados por cultivos sucessivos de arroz de terras altas sob semeadura direta

Upland rice development under a no-tillage system as a function of gypsum and phosphorus.

the objective of this work was to determine the effect of the combination of gypsum applied to the soil surface without tillage and P applied in the sowing furrow on soil attributes and the plant height, number of panicles m-1 and grain yield of upland rice cultivated in an no-tillage system

Adubação a lanço sem incorporação na produtividade do feijão-comum.

O objetivo desse trabalho de pesquisa foi de determinar o efeito de doses de fertilizantes, distribuídos na superfície do solo sem incorporação, nos componentes de produção e produtividade de grãos da cultura do feijão-comum.CONAF

Trees Lose Their Leaves Later in Agroforestry Systems

In Brazilianagroforestry systems (AFS), Cordia oncocalyx trees, a native species of Caatinga, lose their leaves late in relation to the trees of the same species occurring in secondary forest. Our hypothesis is that, due to environmental features, the trees of the AFS maintain better water status. This work aims to present environmental humidity (rainfall, soil moisture and air relative humidity) and trees (photosynthesis, stomatal conductance and transpiration) data to explain the late loss of leaves in anagrosilvopastoral system (AGP) in the Brazilian semiarid region compared to a secondary forest (SF).Meteorological data were obtained from two weather stations installed in the AGP and SF areas. The physiological traits were measured using an infrared gas analyzer. There was a correlation between physiological processes (transpiration and stomatal conductance) and soil water content in plants of AGP, but not in SF, showing some independence of the plants of this system to variations in soil moisture. This indicates that AGP plants may have developed the physiological and anatomical features that enable to them to keep photosynthesis even when climatic conditions are more severe. Although the most inhospitable environmental conditions in the AGP system, the lower density of plants, and therefore less competition for water, favoring photosynthesis longer, causing the leaves to fall later