12,061 research outputs found
Efeito de fósforo e potássio no crescimento de teca (Tectona grandis L.) em solo de baixa fertilidade no Estado de Rondônia.
Este trabalho foi realizado com o objetivo de avaliar o crescimento, aos 14 meses de plantio de teca, cultivado em um Latossolo Amarelo distrófico, com diferentes níveis de fósforo e potássio.bitstream/item/63852/1/ct120-teca.pd
Asymmetric I-V characteristics and magnetoresistance in magnetic point contacts
We present a theoretical study of the transport properties of magnetic point
contacts under bias. Our calculations are based on the Keldish's
non-equilibrium Green's function formalism combined with a self-consistent
empirical tight-binding Hamiltonian, which describes both strong ferromagnetism
and charging effects. We demonstrate that large magnetoresistance solely due to
electronic effects can be found when a sharp domain wall forms inside a
magnetic atomic-scale point contact. Moreover we show that the symmetry of the
- characteristic depends on the position of the domain wall in the
constriction. In particular diode-like curves can arise when the domain wall is
placed off-center within the point contact, although the whole structure does
not present any structural asymmetry.Comment: 7 figures, submitted to PR
The Mass of the Convective Zone in FGK Main Sequence Stars and the Effect of Accreted Planetary Material on Apparent Metallicity Determinations
The mass of the outer convective zone in FGK main sequence stars decreases
dramatically with stellar mass. Therefore, any contamination of a star's
atmosphere by accreted planetary material should affect hotter stars much more
than cool stars. If recent suggestions that high metal abundances in stars with
planets are caused by planetesimal accretion are correct, then metallicity
enhancements in earlier-type stars with planets should be very pronounced. No
such trend is seen, however.Comment: Submitted ApJ Letters March 26th; accepted April 30th. 12 pages, 2
figure
Topological Line Defects around Graphene Nanopores for DNA Sequencing
Topological line defects in graphene represent an ideal way to produce highly
controlled structures with reduced dimensionality that can be used in
electronic devices. In this work we propose using extended line defects in
graphene to improve nucleobase selectivity in nanopore-based DNA sequencing
devices. We use a combination of QM/MM and non-equilibrium Green's functions
methods to investigate the conductance modulation, fully accounting for solvent
effects. By sampling over a large number of different orientations generated
from molecular dynamics simulations, we theoretically demonstrate that
distinguishing between the four nucleobases using line defects in a
graphene-based electronic device appears possible. The changes in conductance
are associated with transport across specific molecular states near the Fermi
level and their coupling to the pore. Through the application of a specifically
tuned gate voltage, such a device would be able to discriminate the four types
of nucleobases more reliably than that of graphene sensors without topological
line defects.Comment: 6 figures and 6 page
2D pattern evolution constrained by complex network dynamics
Complex networks have established themselves along the last years as being
particularly suitable and flexible for representing and modeling several
complex natural and human-made systems. At the same time in which the
structural intricacies of such networks are being revealed and understood,
efforts have also been directed at investigating how such connectivity
properties define and constrain the dynamics of systems unfolding on such
structures. However, lesser attention has been focused on hybrid systems,
\textit{i.e.} involving more than one type of network and/or dynamics. Because
several real systems present such an organization (\textit{e.g.} the dynamics
of a disease coexisting with the dynamics of the immune system), it becomes
important to address such hybrid systems. The current paper investigates a
specific system involving a diffusive (linear and non-linear) dynamics taking
place in a regular network while interacting with a complex network of
defensive agents following Erd\"os-R\'enyi and Barab\'asi-Albert graph models,
whose nodes can be displaced spatially. More specifically, the complex network
is expected to control, and if possible to extinguish, the diffusion of some
given unwanted process (\textit{e.g.} fire, oil spilling, pest dissemination,
and virus or bacteria reproduction during an infection). Two types of pattern
evolution are considered: Fick and Gray-Scott. The nodes of the defensive
network then interact with the diffusing patterns and communicate between
themselves in order to control the spreading. The main findings include the
identification of higher efficiency for the Barab\'asi-Albert control networks.Comment: 18 pages, 32 figures. A working manuscript, comments are welcome
Design and implementation of a real-time wireless sensor network
This paper describes the development of wireless
sensor network prototype that gathers biometrical data
and posture information from several wearable sensor
networks and sends it in real-time to a personal
computer where the information is monitored and
stored. The wireless sensor network is based on a low
power real-time MAC protocol that was designed and
implemented in the MICAz platform. This paper also
presents some analytical results and several
experimental results regarding the behavior of the
developed system.Fundação para a Ciência e a Tecnologia (FCT
Molecular characterization and genetic diversity of potato cultivars using SSR and RAPD markers.
This study aimed to evaluate the genetic diversity and identify potato cultivars by RAPD and SSR markers. The genomic DNA of 16 potato cultivars was amplified with 25 RAPD primers that generated 92 polymorphic bands and 20 SSR primer pairs that produced 136 polymorphic bands. The dendrograms generated by cluster analysis distinguished the cultivars genetically although the dendrograms were not correlated in the comparison of the two markers used. The PIC values demonstrated the high information content of the primers used and 16 potato varieties were identified based on six RAPD primers and three SSR primer pairs. Thus, by means of RAPD and SSR markers the genetic diversity was assessed and the 16 commercial potato cultivars analyzed in this study were identified
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