6,176 research outputs found
Atividade microbiana do solo sob diferentes cultivos irrigados em um Argissolo Vermelho Amarelo distrófico no Submédio São Francisco.
Este trabalho tem por objetivo avaliar a atividade biológica do solo sob diferentes cultivos com uso de irrigação e sua comparação com áreas de Caatinga. As amostras foram coletadas em novembro de 2006 em áreas com cultivo de manga, uva, culturas anuais, banana e em reserva de vegetação natural, no Campo Experimental da Embrapa Semi-¡rido no Distrito Irrigado de Bebedouro
Effect of Carbon Support, Capping Agent Amount, and Pd NPs Size for Bio-Adipic Acid Production from Muconic Acid and Sodium Muconate
The effect of support, stabilizing agent, and Pd nanoparticles (NPs) size was studied for sodium muconate and t,t-muconic acid hydrogenation to bio-adipic acid. Three different activated carbons (AC) were used (Norit, KB, and G60) and carbon morphology did not affect the substrate conversion, but it greatly influenced the adipic acid yield. 1% Pd/KB Darco catalyst, which has the highest surface area and Pd surface exposure, and the smallest NPs size displayed the highest activity. Furthermore, the effect of the amount of the protective agent was studied varying metal/protective agent weight ratios in the range of 1/0.00-1/1.20, using KB as the chosen support. For sodium muconate reduction 1% Pd/KB_1.2 catalyst gave the best results in terms of activity (0.73 s-1), conversion, and adipic acid yield (94.8%), while for t,t-muconic acid hydrogenation the best activity result (0.85 s-1) was obtained with 1% Pd/KB_0.0 catalyst. Correlating the results obtained from XPS and TEM analyses with catalytic results, we found that the amount of PVA (polyvinyl alcohol) influences mean Pd NPs size, Pd(0)/Pd(II) ratio, and Pd surface exposure. Pd(0)/Pd(II) ratio and Pd NPs size affected adipic acid yield and activity during sodium muconate hydrogenation, respectively, while adipic acid yield was related by exposed Pd amount during t,t-muconic acid hydrogenation. The synthesized catalysts showed higher activity than commercial 5% Pd/AC
Spatial distribution of two symmetric four-wave mixing signals induced by Gaussian beams
We present a theoretical analysis of the spatial shape of two symmetric
signals of degenerate four-wave mixing induced by Gaussian beams in a thin
sample of two-level atoms. Our calculations take into account the full spatial
and spectral dependencies of the relevant nonlinear susceptibilities that
govern the two processes. This reveals two interesting effects. The first one
is that the total power of incident beams affects the transverse profile of the
four-wave mixing signals at the medium exit and their free propagation. The
second one is the influence of the spectral characteristics of the medium on
the longitudinal profile of both generated signals upon free propagation. We
argue that the first effect can be seen as the saturation of the medium in
regions of higher intensity, while the second can be understood as the result
of a nonlinear contribution to the refractive index inside the atomic medium.
These effects can be symmetric between the two signals, with asymmetries
induced by different detunings from resonance of the incident fields
Tectonics and fluvial dynamism affecting the Tiber River in prehistoric Rome
Open access funding provided by Istituto Nazionale di Geofisica e Vulcanologia within the CRUI-CARE Agreement. Research funding was provided by Loeb Classical Library Foundation, Gerda Henkel Foundation, American Philosophical Society, Etruscan Foundation, Fondazione Lemmermann, University of Michigan, University of St Andrews, and the Leverhulme Trust.Geomorphological investigations in Rome’s river valley are revealing the dynamism of the prehistoric landscape. It is becoming increasingly apparent that paleogeographic conditions that defined Rome in the historical era are the product of changes since the Bronze Age, which may be the result of local fault activity in addition to fluvial dynamism. Through a dedicated borehole chronostratigraphic study, integrated by 14C and archaeological dates, and paleomagnetic investigations, we offer here new evidence for fault displacement since ca. 4500 years/BP. We present the failure of the sedimentary fabric of a clay horizon caused by liquefaction processes commonly linked with seismic shaking, interpreting an (ca. 4 m) offset to signify the existence of a fault line located at the foot of the Capitoline Hill. In addition, we show evidence for another (ca. 1 m) offset affecting a stratigraphic horizon in the river channel, occurring along another hypothesized fault line crossing through the Tiber Valley. Movement along this fault may have contributed to a documented phase of fast overflooding dated to the sixth century BCE which eventually led to the birth of the Tiber Island. The most plausible scenario implies progressive deformation, with an average tectonic rate of 2 mm/year, along these inferred fault lines. This process was likely punctuated with moderate earthquakes, but no large event necessarily occurred. Together, the available evidence suggests that during the early centuries of sedentary habitation at the site of Rome, active fault lines contributed to significant changes to the Tiber River valley, capable of challenging lowland activities.Publisher PDFPeer reviewe
Improvement of Subtropical Native Grasslands with the Introduction of Forage Species and Phosphorous Fertilizers
The experiment took place in Guarapuava-Brazil, from May 1994 to January, 1996 to evaluate the improvement of a subtropical native grassland by the introduction of species and phosphate fertilization. It was observed that for the higher dose applied there occurred an increase over the production of dry matter and crude protein production and absorption of P and K in the plant. A response was not found to the 180 kg P2O5/ha application probably because of the high capacity of soil adsorption, the method of fertilizer application, non favorable climatic conditions and liming interference. The single superphosphate-SS application was superior to Thermalphosphate- YT and Arad Rock Phosphate-ARP for production of dry matter and over the others sources for absorption of P and K, and only superior to YT for production of crude protein. The levels of Ca, Mg, NDF and ADF in the plant were also discussed
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