931 research outputs found
Will global warming affect the distribution and abundance of the sweetpotato butterfly Acraea acerata Hew. in Africa?
In tropical Africa, the sweetpotato butterfly Acraea acerata, is a major endemic pest of sweetpotato (Ipomoea batatas (L.) Lam). Outbreaks of A. acerata are reported by farmers in Uganda to be more frequent than in the past 10 years. We therefore hypothesise that global warming may be responsible for this increased risk of outbreaks and abundance (damage potential). We used the Insect Life Cycle Modelling (ILCYM) software to develop temperature-based phenology models and applied three risk indices (establishment-, generation, and activity index) in a geographic information system (GIS) to map potential establishment, abundance and spread on global, regional and national scales. For current temperature conditions (year 2000) interpolated WorldClim data were used and for future climates (year 2050) downscaled data of the SRES-A1B scenario were applied
Chiral molecular films as electron polarizers and polarization modulators
Recent experiments on electron scattering through molecular films have shown
that chiral molecules can be efficient sources of polarized electrons even in
the absence of heavy nuclei as source of a strong spin-orbit interaction. We
show that self-assembled monolayers (SAMs) of chiral molecules are strong
electron polarizers due to the high density effect of the monolayers and
explicitly compute the scattering amplitude off a helical molecular model of
carbon atoms. Longitudinal polarization is shown to be the signature of chiral
scattering. For elastic scattering, we find that at least double scattering
events must take place for longitudinal polarization to arise. We predict
energy windows for strong polarization, determined by the energy dependences of
spin-orbit strength and multiple scattering probability. An incoherent
mechanism for polarization amplification is proposed, that increases the
polarization linearly with the number of helix turns, consistent with recent
experiments on DNA SAMs.Comment: 5 Pages, 4 figure
The Rosario dataset: Multisensor data for localization and mapping in agricultural environments
In this paper we present the Rosario dataset, a collection of sensor data for autonomous mobile robotics in agricultural scenes. The dataset is motivated by the lack of realistic sensor readings gathered by a mobile robot in such environments. It consists of six sequences recorded in soybean fields showing real and challenging cases: highly repetitive scenes, reflection, and burned images caused by direct sunlight and rough terrain among others. The dataset was conceived in order to provide a benchmark and contribute to the agricultural simultaneous localization and mapping (SLAM)/odometry and sensor fusion research. It contains synchronized readings of several sensors: wheel odometry, inertial measurement unit (IMU), stereo camera, and a Global Positioning System real-time kinematics (GPS-RTK) system. The dataset is publicly available from http://www.cifasis-conicet.gov.ar/robot/
A mesoscopic ring as a XNOR gate: An exact result
We describe XNOR gate response in a mesoscopic ring threaded by a magnetic
flux . The ring is attached symmetrically to two semi-infinite
one-dimensional metallic electrodes and two gate voltages, viz, and
, are applied in one arm of the ring which are treated as the inputs of
the XNOR gate. The calculations are based on the tight-binding model and the
Green's function method, which numerically compute the conductance-energy and
current-voltage characteristics as functions of the ring-to-electrode coupling
strength, magnetic flux and gate voltages. Our theoretical study shows that,
for a particular value of () (, the elementary
flux-quantum), a high output current (1) (in the logical sense) appears if both
the two inputs to the gate are the same, while if one but not both inputs are
high (1), a low output current (0) results. It clearly exhibits the XNOR gate
behavior and this aspect may be utilized in designing an electronic logic gate.Comment: 8 pages, 5 figure
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