Alfvén wave heating and runaway discharges in the TCABR tokamak

Recent results of experiments on Alfvén wave heating and runaway discharges carried out in the TCABR tokamak are presented. A new antenna type has been installed to allow wave excitation with higher RF currents and lower dynamic polarization of the antenna straps than for the one previously used. In spite of edge plasma heating, which causes influx of impurities, we have obtained a clear confirmation of wave deposition inside the plasma from a localized increase of the electron temperature measured with the ECE radiometer. Detailed profiles of the plasma density and Ha emission were obtained in runaway disharges with currents around 100 kA. These profiles confirm our model of a low-temperature plasma maintained in equilibrium by the relativistic electron beam. Analysis of the Ha and density spikes indicate that recombination plays a substantial role in the particle and energy balance

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Implementation Of A Radio Over Fiber System In A Geographically-distributed Optical Network

This work presents an implementation of a Radio over Fiber system based on IEEE 802.15.4 standard, in a geographically-distributed optical network, called KyaTera. The input signal was launched into hundreds of kilometers from KyaTera Network under real conditions of temperature, pressure, humidity and wind. Experimental results show no performance degradation of the transmitted radio frequency signal.1639641Jia, Z., Yu, J., Ellinas, G., Gee-Kung, C., Key enabling technologies for optical wireless networks optical millimeter wave generation wavelength reuse and architecture (2007) J. of Light. Tech., 25, pp. 3452-3471Chang, S.C.W., (2002) RF Photonic Technology in Optical Fiber Links, , Cambridge University Presswww.kyatera.fapesp.brMarconi, J.D., Callegari, F.A., Abbade, M.L.F., Fragnito, H.L., Field trial evaluation of the Q-factor penalty introduced by fiber four-wave mixing wavelength converters (2008) Opt. Communications, , In Pres

Radio Over Fiber System Applied To Ieee 802.15.4 Standard

We have experimentally applied the Radio over Fiber (RoF) technology to a Wireless Sensor Network (WSN) based on IEEE 802.15.4 standard. Numerical simulations and experimental results demonstrate a successful implementation of a RoF technology operating at 2.4 GHz band over at least 160 km of a geographically-distributed optical network. ©2009IEEE.838840Jia, Z., Yu, J., Ellinas, G., Chang, G.-K., Key enabling technologies for optical wireless networks optical millimeter wave generation wavelength reuse and architecture (2007) Journal of Lightwave Technology, 25, pp. 3452-3471Cerqueira S Jr., A., Valente E Silva, D.C., Fortes, M.A.Q.R., Da Silva, L.F., Branquinho, O.C., Abbade, M.L.F., Performace analysis of a radio over fiber system based on IEEE 802.15.4 standard in a real optical network (2009) Microwave and Optical Technology Letters, 51, pp. 1876-1879William, S., Chang, C., (2002) RF Photonic Technology in Optical Fiber Links, , Cambridge University Presswww.kyatera.fapesp.brMarconi, J.D., Cerqueira S Jr., A., Robinson, J.T., Sherwwod-Droz, N., Okawachi, Y., Hernández-Figueroa, H.E., Lipson, M., Fragnito, H.L., Performance investigation of microphotonic-silicon devices in a field-trial all-optical network (2009) Optics Communications, 282, pp. 849-855Ma, J., Yu, J., Yu, C., Xin, X., Zeng, J., Chen, L., Fiber Dispersion Influence on Transmission of the Optical Millimeter-Waves Generated Using LN-MZM Intensity Modulation (2007) Journal of Ligthwave Technology, 25, pp. 3244-3256. , NovemberNovak, D., Hybrid Fiber Radio - The Application of Photonic Links in Wireless Communication Systems Optical Fiber Communications Conference, SC 217, 200

Low variation in ribosomal DNA and internal transcribed spacers of the symbiotic fungi of leaf-cutting ants (Attini: Formicidae)

Leaf-cutting ants of the genera Atta and Acromyrmex (tribe Attini) are symbiotic with basidiomycete fungi of the genus Leucoagaricus (tribe Leucocoprineae), which they cultivate on vegetable matter inside their nests. We determined the variation of the 28S, 18S, and 5.8S ribosomal DNA (rDNA) gene loci and the rapidly evolving internal transcribed spacers 1 and 2 (ITS1 and ITS2) of 15 sympatric and allopatric fungi associated with colonies of 11 species of leafcutter ants living up to 2,600 km apart in Brazil. We found that the fungal rDNA and ITS sequences from different species of ants were identical (or nearly identical) to each other, whereas 10 GenBank Leucoagaricus species showed higher ITS variation. Our findings suggest that Atta and Acromyrmex leafcutters living in geographic sites that are very distant from each other cultivate a single fungal species made up of closely related lineages of Leucoagaricus gongylophorus. We discuss the strikingly high similarity in the ITS1 and ITS2 regions of the Atta and Acromyrmex symbiotic L. gongylophorus studied by us, in contrast to the lower similarity displayed by their non-symbiotic counterparts. We suggest that the similarity of our L. gongylophorus isolates is an indication of the recent association of the fungus with these ants, and propose that both the intense lateral transmission of fungal material within leafcutter nests and the selection of more adapted fungal strains are involved in the homogenization of the symbiotic fungal stock