Farmers' Demand for Information about Agribusiness

This study is focused on the habits of the Brazilian farmers that access the Internet for searching information to their economical activities. The main goal is to understand how come those agents of the agribusiness use the formal and informal (personal contact) means of communication, as well as the functions that each of those means accomplish to this public. In other words, it intends to identify the channels of communication of major importance to farmers (used more often, considered the ones of more credibility and preferred among them). That is possible by means of a questionnaire sent exclusively by e-mail, answered by Brazilian farmers. The motivation of the study is to contribute to make the communication more efficient to those who work on farms. That can produce benefits to the communication companies and to the public. The results show that the Internet is the mean of communication more often used and preferred on the process of searching information about the agribusiness among Brazilian farmers. The personal contact, not considered in the valuation about preference, appears in second position in the ranking for intensity of use. On the other hand, the radio, regional press newspapers and newsletters of class entities were the less consulted and the last ones in the ranking of preference.Agribusiness, Teaching/Communication/Extension/Profession,

Bilayer Metasurface: Induced Transparency and Fabry Perot Resonance

A Fabry-Perot resonator utilizes two solid, non-resonating, reflecting mirrors to form resonant patterns when the separation between the mirrors satisfies the resonance conditions. The resonant mode concentrates at the middle of the cavity. In this study, we constructed a Fabry-Perot cavity with nanostructured resonant metasurfaces as meta-mirrors. The individual metasurfaces exhibit resonant transmission dips with a minimum transmission and a quality factor of t0 and Qs, respectively. The coherent interference between the two metasurfaces changes the behavior of the entire resonant system, generating an induced transparency in the original spectrum. The sharpness of the induced transparency peak is linearly related to the group delay of the single metasurface. Assuming a Lorentzian lineshape, we show that for small t0, the quality factor of the induced transparency peak is Qs/t0^3. The field confines to the meta-mirrors region rather than at the middle of the Fabry-Perot cavity. We provide examples of practical metasurfaces made from dielectric scatters composed of silicon thin nanodisks and demonstrate high quality factors and phase dispersion that are unattainable by any nano or microscale flat optics systems

Entanglement of two qubits mediated by one-dimensional plasmonic waveguides

We investigate qubit-qubit entanglement mediated by plasmons supported by one-dimensional waveguides. We explore both the situation of spontaneous formation of entanglement from an unentangled state and the emergence of driven steady-state entanglement under continuous pumping. In both cases, we show that large values for the concurrence are attainable for qubit-qubit distances larger than the operating wavelength by using plasmonic waveguides that are currently available.Comment: 4 pages, 4 figures. Minor Changes. Journal Reference added. Highlighted in Physic

Faddeev eigenfunctions for point potentials in two dimensions

We present explicit formulas for the Faddeev eigenfunctions and related generalized scattering data for point (delta-type) potentials in two dimensions. In particular, we obtain the first explicit examples of such eigenfunctions with contour singularity in spectral parameter at a fixed real energy

Applicability of Ammonia Sensors for Controlling Environmental Parameters in Accommodations for Lamb Fattening

Electrochemical ammonia sensors were used to analyse the existing relationship between the ammonia concentration and ambient levels of both temperature and relative humidity in commercial lamb fattening housing equipped with mechanical ventilation and straw-bedded pens. In the first stage of the experiment, sensors were placed over straw beds covered in lamb urine and analysed under laboratory conditions in order to determine ammonia emission evolution over time; three control temperatures (25, 35, and 50 degrees C) were used. A HOBO H8 temperature and relative humidity logger and a Drager NH3LC-6809680 electrochemical ammonia sensor placed in a Drager Polytron 7000 gas detector were utilized as sensors. A positive correlation was established between both ammonia emission time and emitted amount with temperature. Additionally, tests were performed in a commercial lamb housing to determine ammonia concentration variation with respect to height from the ground; three ammonia sensors placed at 50, 90, and 135 cm above the ground were used simultaneously. The ammonia concentration significantly decreased as height increased. A 90 cm height was selected, and three ammonia probes were placed in three different pens inside the livestock housing, along with temperature and relative humidity sensors; four different housing ventilation rates were then tested under real conditions over a time period of 4 months. An adjustment polynomial equation between the housing ambient temperature and the ammonia concentration was obtained with R-2 = 0.632. In conclusion, a relationship can be established between temperature and ammonia concentration in commercial lamb housing under certain handling conditions, which in turn allows for estimating the ammonia concentration adequately based on the ambient internal temperature

Active control of focal length and beam deflection in a metallic nano-slit array lens with multiple sources

We propose a surface plasmon-polariton based nano-rod array lens structure that incorporates two additional lateral input channels, with the ability to control the focal length and the deflection of the transmitted beam through the lens actively by the intensity of the channel sources. We demonstrate by numerical simulations that, applying the sources with the same intensity can change the focal point and the beam waist, whereas unequal intensities generate an asymmetric field profile in the nano-rod array inducing an off-axis beam deflection.Comment: 4 pages, 5 figure

Order N photonic band structures for metals and other dispersive materials

We show, for the first time, how to calculate photonic band structures for metals and other dispersive systems using an efficient Order N scheme. The method is applied to two simple periodic metallic systems where it gives results in close agreement with calculations made with other techniques. Further, the approach demonstrates excellent numerical stablity within the limits we give. Our new method opens the way for efficient calculations on complex structures containing a whole new class of material.Comment: Four pages, plus seven postscript figures. Submitted to Physical Review Letter

Geometrically induced modification of surface plasmons in the optical and telecom regimes

We demonstrate that the introduction of a subwavelength periodic modulation into a metallic structure strongly modifies the guiding characteristics of the surface plasmon modes supported by the system. Moreover, it is also shown how a new type of a tightly confined surface plasmon polariton mode can be created by just milling a periodic corrugation into a metallic ridge placed on top of a metal surface