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

Algorithms For Fwm-aware Routing And Wavelength Assignment

This work presents a study on the impact of the Four Wave Mixing in dynamic optical networks. We have proposed two algorithms for routing and wavelength assignment based on the limitations imposed by Four Wave Mixing crosstalk. When the efficiency of the effect is not very high, the algorithms present a good performance in order to minimize the Four Wave Mixing. The results suggest that, under certain conditions, there is no loss in basing the allocation of long routes only on the amount of FWM contamination of the new path, and not on the other active paths.707712Tkach, R.W., Chrplyvy, A.R., Forghieri, F., Gnauck, A.H., Derosier, R.M., Four-photon mixing and high-speed WDM systems (1995) J. Lightwave Technol., 13 (5). , MayInoue, K., A simple expression for optical FDM network scale considering fiber four-wave mixing and optical amplifier noise (1995) J. Lightwave Technology, 13, pp. MayForghieri, F., Tkach, R.W., Chraplyvy, A.R., WDM systems with unequally spaced channels (1995) Journal of Lightwave Technology, 13 (5). , MayMoschim, E., Abbade, M.L.F., Fonseca, I.E., Competition between FWM dynamics and modulational instability in dispersion shifted fibers (2002) IEEE Photonics Technology Letters, 14 (1). , JanRamaswami, R., Sivarajan, K.N., Routing and wavelength assignment in all-optical networks (1995) IEEE/ACM Transactions on Networking, 3 (5). , OctWaldman, H., Campelo, D.R., Camelo, R., Dynamic Prioryty Strategies for Wavelength Assignment in WDM Rings (2000) Proc. IEEE Globecom'00Krishnaswamy, R.M., Sivarajan, K.N., Algorithms for routing and wavelength assignment based on solutions of LP-relaxations (2001) IEEE Communications Letters, 5 (10). , OctMaeda, M.W., Management and control of transparent optical networks (1998) IEEE J. Select. Areas Commun., 16. , SeptSong, S., Allen, C.T., Demarest, K.R., Hui, R., Intensity-Dependent Phase-Matching Effects on Four-Wave Mixing in Optical Fibers (1999) Journal of Lightwave Tecnology, 17. , NovAli, M., Elie-Dit-Cosaque, D., Tancevski, L., Network Optimization with Transmission Impairments-Based Routing (2001) ECOC'01Ali, M., Tancevski, L., Impact of Polarization-Mode Dispersion on the Design of Wavelength-Routed Networks (2002) IEEE Photonics Technology Letters, 14 (5). , MayLevandovsky, D., Wavelength routing based on physical impairments (2001) Proc. IEEE OFC'01Rossi, S.M., Barros, M.R.X., Rocha, M.L., Rosolem, J.B., Paradisi, A., Padua, F.J.L., Moschim, E., Impact of Physical Layer Impairments on Optical Network Performance (2002) Proc. IEEE ITS 2002, , Natal-RN, BrazilRamaswami, R., Sivarajan, K.N., (2002) "Optical Networks: A Practical Perspective", Second Edition, , Morgan Kaufmann Publishers, Inc., San Francisco, CaliforniaBarry, R.A., Humblet, P.A., Models of Blocking Probability in All-optical Networks with and without Wavelength Changers (1996) IEEE J. Select. Areas Commun., 14. , Ju

Meeting Optical Qos Requirements With Reduced Complexity In Dynamic Wavelength Assignment

Physical layer impairments may require highly complex implementations of the control plane in dynamic networks with Quality of Service (QoS) constraints. In order to alleviate this problem, we propose that dynamic wavelength assignment should be based on the elementary First-Fit (FF) algorithm using off-line optimized priority lists. It is shown that this may significantly reduce the effects of physical impairments with no additional computational cost for the control of dynamic networks. A simple metric is proposed to evaluate optical QoS taking the performance of the network as a whole. Different heuristics are presented and evaluated. Results show that there are particular lists capable of reducing in four orders of magnitude the probability of FWM impacting network performance. © 2004 IEEE.331333Ramamurthy, B., Datta, D., Feng, H., Heritage, J.P., Mukherjee, B., Impact of transmission impairments on the teletraffic performance of wavelength-routed optical networks (1999) J. Ligthwave Technology, 17, pp. 1713-1723. , OctAli, M., Tancevski, L., Impact of polarization-mode dispersion on the design of wavelength-routed networks (2002) Photonics Technology Letters, 14, pp. 720-722. , MayFonseca, I.E., Ribeiro, M.R.N., Almeida Jr., R.C., Waldman, H., Preserving global optical QoS in FWM impaired dynamic networks (2004) Electronics Letters, 40, pp. 191-192. , FebXu, B., Brandt-Pearce, M., Comparison of FWM- And XPM-induced crosstalk using the Volterra series transfer function method (2003) J. Ligthwave Technology, 21, pp. 40-53. , JanFonseca, I.E., Almeida Jr., R.C., Ribeiro, M.R.N., Waldman, H., Algorithms for FWM-aware routing and wavelength assignment (2003) Proc. IEEE IMOC'03, 2, pp. 707-713. , SepInoue, K., A simple expression for optical FDM network scale considering fiber FWM and optical amplifier noise (1995) J. Ligthwave Technology, 13, pp. 856-861. , MayForghieri, F., Tkach, R.W., Chraplyvy, A.R., Marcuse, D., Reduction of four-wave mixing crosstalk in WDM systems using unequally spaced channels (1994) Photonics Technology Letters, 6, pp. 754-756. , Jun(2002) Spectral Grids for WDM Application: DWDM Frequency Grid, , ITU-T Rec. G.694.1, Ju