Formal Synthesis of (±)-Coriolin by Diastereocontrolled Nickel(0)-Catalyzed 'Metallo-ene-type' Cyclization/Methoxycarbonylation

Bicyclooctanone (±)-2, an advanced intermediate for the synthesis of (±)-coriolin, has been synthesized in ten steps starting from 2,2-dimethylpent-4-enal (7). The key step 6 → 3 + 11 is a highly diastereoselective, Ni0-catalyzed, tandem intramolecular alkene allylation/carbonylation reaction

Slowed response to peripheral visual stimuli during strenuous exercise

Recently, we proposed that strenuous exercise impairs peripheral visual perception because visual responses to peripheral visual stimuli were slowed during strenuous exercise. However, this proposal was challenged because strenuous exercise is also likely to affect the brain network underlying motor responses. The purpose of the current study was to resolve this issue. Fourteen participants performed a visual reaction-time (RT) task at rest and while exercising at 50% (moderate) and 75% (strenuous) peak oxygen uptake. Visual stimuli were randomly presented at different distances from fixation in two task conditions: the Central condition (2° or 5° from fixation) and the Peripheral condition (30° or 50° from fixation). We defined premotor time as the time between stimulus onset and the motor response, as determined using electromyographic recordings. In the Central condition, premotor time did not change during moderate (167 ± 19 ms) and strenuous (168 ± 24 ms) exercise from that at rest (164 ± 17 ms). In the Peripheral condition, premotor time significantly increased during moderate (181 ± 18 ms, P < 0.05) and strenuous exercise (189 ± 23 ms, P < 0.001) from that at rest (173 ± 17 ms). These results suggest that increases in Premotor Time to the peripheral visual stimuli did not result from an impaired motor-response network, but rather from impaired peripheral visual perception. We conclude that slowed response to peripheral visual stimuli during strenuous exercise primarily results from impaired visual perception of the periphery

Direction of arrival estimation using off-the-shelf directional antennas array

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, 2018.Estimação da direção de chegada (do inglês: DoA) é um importante campo de estudo, sendo requerido em aplicações civis e militares como comunicações sem o, bus a e resgate, execução de leis, sonar e sismologia. Para todas essas aplicações, é necessário saber o ângulo de chegada de um sinal de rádio impingindo em um receptor para pós-processamento. Como o número de acidentes e incidentes envolvendo veículos aéreos não tripulados (VANTs) aumentou nos últimos anos, uma possível apli ação e também motivação para o presente estudo é a localização de VANTs invasores. Trabalhos anteriores sobre a estimação do ângulo de chegada a partir da potência do sinal recebido (do inglês: RSS) fez uso de uma geometria sólida platni a associada om o algoritmo MUSIC (do inglês: Multiple Signal Classication). Um algoritmo para a estimação da direção de chegada om menor complexidade computacional que o MUSIC é apresentado neste trabalho, no qual as diferenças das potên cias dos sinais recebidos em ada antena direcional do arranjo são comparadas om as diferenças dos padrões de ganho de diretividade de cada antena para a estimação do DoA de um sinal NTSC, tipi amente usado em VANTs. Diferente das técnicas tradicionais de estimação DoA baseadas na fase, as quais dependem, por exemplo, da diferença de fase dos sinais recebidos e, portanto, necessitam de uma extensa calibração prévia entre as antenas do arranjo, o proposto algoritmo baseado em RSS possui um uso mais direto e plug-and-play, tornando-o uma solução mais simples para aplicações como a estimação do DoA de VANTs. Após as simulações da técnica proposta e da verificação de sua e ciência, o melhor espaçamento angular entre as antenas do arranjo é computado. Em seguida, experimentos em campo foram feitos om equipamentos de baixo custo, como, por exemplo, a placa controladora AD-FMCOMMS5- EBZ que contém o receptor AD9361, vídeo- câmera, transmissor NTSC e antenas Yagi-Uda. São descritos experimentos que precisamente detectam a direção de chegada de sinais emitidos de um VANT invasor.Dire tion of arrival (DoA) estimation is an important eld of study, being required in ivilian and military appli ations su h as in wireless ommuni ations, sear h and res ue, law enfor ement, sonar, and seismology. For all these appli ations, it is neessary to know the angle of arriving of an impinging radio signal on a re eiver for further pro essing. Sin e the number of a idents and in idents involving unmanned aerial vehi les (UAVs) have in reased in the past years, a probable appli ation and also motivation for this study is the lo alizing of intruding UAVs. Previous works on DoA estimation via re eived signal strength (RSS) value used platoni solid geometry asso iated with the multiple signal lassi ation (MUSIC) algorithm. A DoA estimation algorithm with less omputational omplexity than the MUSIC algorithm is hereby presented, in whi h the dieren es of the RSS values measured between ea h dire tional antenna on the array is ompared with the dieren es between their dire tivity gain pattern in order to estimate the dire tion of arrival of an in oming NTSC signal, whi h are typi ally used in UAVs. Dierent from the traditional phase-based DoA estimation te hniques, whi h rely on, among others, the phase dieren e of the in oming signals, and thus need a previous time- onsuming alibration pro ess between the antennas on the array, the proposed RSS-based algorithm has a straightforward plug- and-play use, making it a simpler solution for appli ations su h as the DoA estimation of UAVs. After simulating the proposed te hnique and verifying its e ien y, the best angular spa ing between the antennas on the array is omputed. Then, eld experiments were held with o-the- shelf and low- ost equipment, for instan e, the AD-FMCOMMS5-EBZ daughter board ontaining the AD9361 re eiver, video amera, NTSC transmitter and Yagi-Uda antennas. Experiments that a urately dete t the dire tion of arrival of signals emitted from an intruder UAV is des ribed

Preparation of Some α-Substituted Cyclopropanecarboxylic Acids via Dichlorocarbene

Some α, β-unsaturated esters (1), including trans-crotonate, trans-α-methoxycrotonate, irans-α-fluorocrotonate, trans-cinnamate, trans-α-chlorocinnamate, cis- and trans-α-fluorocinnamates, fumarate, and maleate, were allowed to react with dichlorocarbene, generated by the thermal decomposition of sodium trichloroacetate at 120-160°C, to give the corresponding β, β-dichlorocyclopropanecarboxylates (2) in fair to good yields (38-88%). The additions of dichlorocarbene to these esters were stereospecific. A similar reaction of n-butyl acrylate gave only a very low yield (6%) of the dichlorocarbene adduct, probably because of the accompanying polymerization of the starting ester. The reduction of 1-unsubstituted or 1-methoxysubstituted 2, 2-dichloro-3-methylcyclopropanecarboxylate with tri-n-butyltin hydride at 90°C yielded both the completely reduced (3) and the partially reduced esters (4 and 5). That of 1-fluoro-substituted ester gave only the completely reduced product. These cyclopropanecarboxylates (2 and 3) were hydrolyzed with potassium hydroxide to give the corresponding free acids (6 and 7) in good yields (72-92%). The properties (bp, mp, nᴅ, pmr spectral data, etc.) of the cyclopropanecarboxylic acids and esters thus prepared are described

Demonstrating a new technology for space debris removal using a bidirectional plasma thruster

Abstract Space debris removal from Earth orbit by using a satellite is an emergent technological challenge for sustainable human activities in space. In order to de-orbit debris it is necessary to impart a force to decelerate it, resulting in its atmospheric re-entry. A satellite using an energetic plasma beam directed at the debris will need to eject plasma in the opposite direction in a controlled manner in order to maintain a constant distance between it and the debris during the deorbiting mission. By employing a magnetic nozzle plasma thruster having two open source exits, bi-directional plasma ejection can be achieved using a single electric propulsion device. Both the forces exerted on the thruster and the target plate simulating the debris are simultaneously measured in a laboratory space simulation chamber showing that a force decelerating the debris and a zero net force on the thruster can be successfully obtained. These two forces can be individually controlled by external electrical parameters, resulting in the ability to switch the acceleration and deceleration modes of the satellite and the debris removal mode using a single electric propulsion device