A 300 GHz "Always-in-Focus" Focusing System for Target Detection

A focusing system for a 300 GHz radar with 5 m target distance and 10 mm diameter spot size resolution is proposed. The focusing system is based on a Gaussian telescope scheme and its main parameters have been de¬signed using Gaussian beam quasi-optical propagation theory with an in-house developed MATLAB® based analysis tool. Then, this approach has been applied to a real focusing system based on two elliptical mirrors in order to reduce the distortion and cross-polar level and a plane mirror to provide scanning capabilities. The over¬all system has been simulated with a full-wave electromag¬netic simulator and its behavior is presented. With this approach, the focusing system always works "in-focus" since the only mirror that is rotated when scanning is the output plane mirror, so the beam is almost not distorted. The design process, although based in the well-known Gaussian beam quasi-optical propagation theory, provides a fast and accurate method and minimizes the overall size of the mirrors. As a consequence, the size of the focusing system is also reduced

Review

Functional ultrasound (fUS) is a hemodynamic-based functional neuroimaging technique, primarily used in animal models, that combines a high spatiotemporal resolution, a large field of view, and compatibility with behavior. These assets make fUS especially suited to interrogating brain activity at the systems level. In this review, we describe the technical capabilities offered by fUS and discuss how this technique can contribute to the field of functional connectomics. First, fUS can be used to study intrinsic functional connectivity, namely patterns of correlated activity between brain regions. In this area, fUS has made the most impact by following connectivity changes in disease models, across behavioral states, or dynamically. Second, fUS can also be used to map brain-wide pathways associated with an external event. For example, fUS has helped obtain finer descriptions of several sensory systems, and uncover new pathways implicated in specific behaviors. Additionally, combining fUS with direct circuit manipulations such as optogenetics is an attractive way to map the brain-wide connections of defined neuronal populations. Finally, technological improvements and the application of new analytical tools promise to boost fUS capabilities. As brain coverage and the range of behavioral contexts that can be addressed with fUS keep on increasing, we believe that fUS-guided connectomics will only expand in the future. In this regard, we consider the incorporation of fUS into multimodal studies combining diverse techniques and behavioral tasks to be the most promising research avenue

Resonant demagnetization of a dipolar BEC in a 3D optical lattice

We study dipolar relaxation of a chromium BEC loaded into a 3D optical lattice. We observe dipolar relaxation resonances when the magnetic energy released during the inelastic collision matches an excitation towards higher energy bands. A spectroscopy of these resonances for two orientations of the magnetic field provides a 3D band spectroscopy of the lattice. The narrowest resonance is registered for the lowest excitation energy. Its line-shape is sensitive to the on-site interaction energy. We use such sensitivity to probe number squeezing in a Mott insulator, and we reveal the production of three-body states with entangled spin and orbital degrees of freedom.Comment: 5 pages, 3 Figures, Supplemental Materia

Caracterização física do carvão de cajá (Spondias mombin L.).

Estudos voltados para melhorar a estrutura do solo e o aumenta da sua capacidade de retenção de água e nutrientes são constantes. A descoberta da 'terra preta do índio', em registros arqueológicos de comunidades indígenas da Amazônia, tem despertado diversas pesquisas, pois foi verificada a presença de grande quantidade de matéria orgânica, oriunda de carvão, que exibia propriedades coloidais e alta capacidade de troca catiônica, além de possuírem grande capacidade de retenção de água quando comparado a outros solos. O carvão encontrado nesses solos é uma substância orgânica, obtida utilizando-se o processo de pirólise. Esse sistema utiliza o aquecimento do material na presença de pouco ou nenhum oxigênio a uma temperatura média de 400 graus. O que retém boa parte do carbono presente no material orgânico pirolisado, que é incorporado ao solo em uma forma de grande estabilidade física e química. O objetivo deste trabalho foi determinar alguns parâmetros físicos em partículas com diâmetro das frações areia e silte mais argila, de um carvão oriundo da madeira do cajá (Spondias mombin L.).PDF. 002

A utilização do carvão vegetal como condicionador de solos.

A terra preta do Índio (TPI) surgiu a partir de ações antrópicas. Evidências provam que esses solos foram formados por antigas comunidades indígenas amazônicas, que habitavam áreas densamente povoadas. O hábito de queimar resíduos orgânicos em fogo lento, combustão em alta temperatura na ausência ou presença de pequeno volume de oxigênio (pirólise), pode reter até 80% do carbono presente no material orgânico ao se transformar em carvão. A adição de carvão ao solo, em partículas no tamanho das frações de areia, silte e argila, pode alterar os limites de consistência, melhorar a capacidade de retenção de água, elevar o pH e contribuir para melhorar a estrutura do solo. O objetivo deste trabalho foi avaliar o potencial de utilização do carvão como condicionador de solos em Latossolos Amarelos Coesos dos Tabuleiros Costeiros

Dipolar atomic spin ensembles in a double-well potential

We experimentally study the spin dynamics of mesoscopic ensembles of ultracold magnetic spin-3 atoms located in two separated wells of an optical dipole trap. We use a radio-frequency sweep to selectively flip the spin of the atoms in one of the wells, which produces two separated spin domains of opposite polarization. We observe that these engineered spin domains are metastable with respect to the long-range magnetic dipolar interactions between the two ensembles. The absence of inter-cloud dipolar spin-exchange processes reveals a classical behavior, in contrast to previous results with atoms loaded in an optical lattice. When we merge the two subsystems, we observe spin-exchange dynamics due to contact interactions which enable the first determination of the s-wave scattering length of 52Cr atoms in the S=0 molecular channel a_0=13.5^{+11}_{-10.5}a_B (where a_B is the Bohr radius).Comment: 9 pages, 7 figure