Spectral Engineering with Coupled Microcavities: Active Control of Resonant Mode-Splitting

Optical mode-splitting is an efficient tool to shape and fine-tune the spectral response of resonant nanophotonic devices. The active control of mode-splitting, however, is either small or accompanied by undesired resonance shifts, often much larger than the resonance-splitting. We report a control mechanism that enables reconfigurable and widely tunable mode-splitting while efficiently mitigating undesired resonance shifts. This is achieved by actively controlling the excitation of counter-traveling modes in coupled resonators. The transition from a large splitting (80 GHz) to a single-notch resonance is demonstrated using low power microheaters (35 mW). We show that the spurious resonance-shift in our device is only limited by thermal crosstalk and resonance-shift-free splitting control may be achieved.Comment: 4 pages, 3 figure

Comparison between GC-MS-SIM and GC-ECD for the determination of residues of organochlorine and organophosphorus pesticides in Brazilian citrus essential oils.

Óleos essenciais cítricos brasileiros (mandarina, laranja, limão, bergamota e tangerina) foram analisados a fim de determinar resíduos de pesticidas organoclorados (aldrin, clordano, dieldrin e dicofol) e organofosforados (clorpirifós metílico, dimetoato, metidationa e paration metílico). Um estudo comparativo entre cromatografia gasosa acoplada a espectrometria de massas em modo de monitoramento seletivo de íons (CG-EM-MSI) e cromatografia gasosa com detector por captura de elétrons (CG-DCE) foi realizado usando extração em fase sólida (EFS) com fase Florisil® para pré-concentração dos pesticidas. A recuperação média dos pesticidas foi de 71 a 83% por CG-EM-MSI e de 99 a 104% por CG-DCE. O limite de quantificação foi de 0,93 a 3,93 mg L-1 por CG-EM-MSI e de 0,09 a 0,12 mg L-1 por CG-DCE. Quinze amostras comerciais de óleos essenciais cítricos brasileiros foram analisadas e seis amostras apresentaram contaminação com valores acima do limite máximo de resíduos (LMR) permitido pelo Codex Alimentarius

Modeling quasi-dark states with Temporal Coupled-Mode Theory

Coupled resonators are commonly used to achieve tailored spectral responses and allow novel functionalities in a broad range of applications, from optical modulation and filtering in integrated photonic circuits to the study of nonlinear dynamics in arrays of resonators. The Temporal Coupled-Mode Theory (TCMT) provides a simple and general tool that is widely used to model these devices and has proved to yield very good results in many different systems of low-loss, weakly coupled resonators. Relying on TCMT to model coupled resonators might however be misleading in some circumstances due to the lumped-element nature of the model. In this article, we report an important limitation of TCMT related to the prediction of dark states. Studying a coupled system composed of three microring resonators, we demonstrate that TCMT predicts the existence of a dark state that is in disagreement with experimental observations and with the more general results obtained with the Transfer Matrix Method (TMM) and the Finite-Difference Time-Domain (FDTD) simulations. We identify the limitation in the TCMT model to be related to the mechanism of excitation/decay of the supermodes and we propose a correction that effectively reconciles the model with expected results. A comparison with TMM and FDTD allows to verify both steady-state and transient solutions of the modified-TCMT model. The proposed correction is derived from general considerations, energy conservation and the non-resonant power circulating in the system, therefore it provides good insight on how the TCMT model should be modified to eventually account for the same limitation in a different coupled-resonator design. Moreover, our discussion based on coupled microring resonators can be useful for other electromagnetic resonant systems due to the generality and far-reach of the TCMT formalism.Comment: 7 pages, 4 figure

Mites (Acari: Mesostigmata, Sarcoptiformes and Trombidiformes) associated to soybean in Brazil, including new records from the Cerrado areas.

In Brazil, soybean Glycine max (L.) Merril crops are subjected to incidence of several pests, which are mainly insect species. However, the occurrences of other pest species are growing. In this context, outbreaks of phytophagous mites are becoming more frequent. Nevertheless, records of mites in such crop are available only for Maranhão, Mato Grosso, Minas Gerais and Rio Grande do Sul states. Thus, this work gathers all information published about the diversity of mites found in soybean in Brazil, and also new records of mite species made on samplings taken from the central Cerrado area. In the whole, occurrence of 44 species of plant mites in soybean has been recorded in Brazil. Data from prior studies and the results of this work present the tetranychid Mononychellus planki (McGregor) as the mite species most frequently occurring in the Brazilian soybean crops. A large portion of Phytoseiidae species has occurred in crops from Rio Grande do Sul state. In addition, spontaneous soybean has hosted almost half of the phytoseiid species sampled in Cerrado region. High diversity of Tarsonemidae has been found in the cultivated soybean. More studies about soybean mites are needed to clarify the damage potential of phytophagous mites and the biological role of predatory mites in this crop. RESUMO: No Brasil, lavouras de soja Glycine max (L.) Merril estão sujeitas a incidência de várias pragas, as quais são principalmente espécies de insetos. No entanto, a ocorrência de outras espécies-praga tem aumentado. Neste contexto, surtos populacionais de ácaros fitófagos têm se tornado mais frequentes. Apesar disso, os registros de ácaros para esta cultura estão disponíveis apenas para os estados de Maranhão, Mato Grosso, Minas Gerais e Rio Grande do Sul. Assim, este trabalho agrega toda a informação publicada sobre a diversidade de ácaros encontrados em soja no Brasil, além de novos registros feitos através de amostragens na região central do Cerrado. No total, 44 espécies de ácaros foram registradas em soja no Brasil. Dados de estudos anteriores, somados aos resultados deste trabalho, apresentam o tetraniquídeo Mononychellus planki (McGregor) como a espécie de ácaro mais frequente em lavouras de soja brasileiras. Considerável número de espécies de Phytoseiidae tem ocorrido nas lavouras amostradas do Rio Grande do Sul. Além disso, a soja espontânea abrigou quase metade das espécies de fitoseídeos amostrados na região central do Cerrado. Por sua vez, uma elevada diversidade de Tarsonemidae foi encontrada na soja cultivada. Mais estudos sobre ácaros em soja são necessários para esclarecer o potencial de dano dos ácaros fitófagos e o papel biológico dos ácaros predadores nesta cultura

Reconsidering mammal extinctions in the Pernambuco Endemism Center of the Brazilian Atlantic Forest

Reconsiderando la extinción de mamíferos en el Centro de Endemismo Pernambuco perteneciente al bosque atlántico brasileño Se ha calculado que, en los últimos 500 años, se han extinguido 21 mamíferos en el Centro de Endemismo Pernambuco. En el presente estudio, realizamos un examen crítico de los datos aportados en las publicaciones científicas históricas y recientes, y concluimos que el número real de mamíferos extintos es de siete, lo que indica que la cifra anterior de 21 especies extintas es una sobrestimación de aproximadamente 30 %. Nuestra lista difiere de las publicaciones previas en que incluye especies aún existentes (n = 5) y excluye otras que nunca habían sido registradas en el Centro de Endemismo Pernambuco (n = 8). Asimismo, señalamos que, al elaborar listas de fauna extinta a escala regional, es necesario adoptar un planteamiento más riguroso en relación con los registros históricos y recientes, dado que las identificaciones erróneas y las suposiciones falsas podrían conducir a la pérdida de credibilidad ante las partes interesadas y, en última instancia, ser negativas para la conservación de especies.In the last 500 years, there have been an estimated 21 mammal extinctions in the Pernambuco Endemism Center. We critically reviewed the published historical and recent literature records and concluded that the actual number of mammal species extinction was seven, indicating that the previous figure of 21 species lost is an overestimation of approximately 30 %. Our checklist differs from previous publications by including species that are still extant (n = 5), and removing species that have never been recorded in the Pernambuco Endemism Center (n = 8). We point out that a more rigorous approach towards historical and recent records is needed when producing lists of regionally extinct fauna, given that the implications of misidentifications and false assumptions can potentially lead to loss of credibility by stakeholders and ultimately have a negative effect on species conservation.Reconsiderando la extinción de mamíferos en el Centro de Endemismo Pernambuco perteneciente al bosque atlántico brasileño Se ha calculado que, en los últimos 500 años, se han extinguido 21 mamíferos en el Centro de Endemismo Pernambuco. En el presente estudio, realizamos un examen crítico de los datos aportados en las publicaciones científicas históricas y recientes, y concluimos que el número real de mamíferos extintos es de siete, lo que indica que la cifra anterior de 21 especies extintas es una sobrestimación de aproximadamente 30 %. Nuestra lista difiere de las publicaciones previas en que incluye especies aún existentes (n = 5) y excluye otras que nunca habían sido registradas en el Centro de Endemismo Pernambuco (n = 8). Asimismo, señalamos que, al elaborar listas de fauna extinta a escala regional, es necesario adoptar un planteamiento más riguroso en relación con los registros históricos y recientes, dado que las identificaciones erróneas y las suposiciones falsas podrían conducir a la pérdida de credibilidad ante las partes interesadas y, en última instancia, ser negativas para la conservación de especies

Dirac-Surface-State-Dominated Spin to Charge Current Conversion in the Topological Insulator (Bi0.22Sb0.78)2Te3(Bi_{0.22}Sb_{0.78})_2Te_3 Films at Room Temperature

We report the spin to charge current conversation in an intrinsic topological insulator (TI) $(Bi_{0.22}Sb_{0.78})_2Te_3$ film at room temperature. The spin currents are generated in a thin layer of permalloy (Py) by two different processes, spin pumping (SPE) and spin Seebeck effects (SSE). In the first we use microwave-driven ferromagnetic resonance of the Py film to generate a SPE spin current that is injected into the TI $(Bi_{0.22}Sb_{0.78})_2Te_3$ layer in direct contact with Py. In the second we use the SSE in the longitudinal configuration in Py without contamination by the Nernst effect made possible with a thin NiO layer between the Py and $(Bi_{0.22}Sb_{0.78})_2Te_3$ layers. The spin-to-charge current conversion is attributed to the inverse Edelstein effect (IEE) made possible by the spin-momentum locking in the electron Fermi contours due to the Rashba field. The measurements by the two techniques yield very similar values for the IEE parameter, which are larger than the reported values in the previous studies on topological insulators.Comment: 18 pages and 7 figure