Optical black hole lasers

Using numerical simulations we show how to realise an optical black hole laser, i.e. an amplifier formed by travelling refractive index perturbations arranged so as to trap light between a white and a black hole horizon. The simulations highlight the main features of these lasers: the growth inside the cavity of positive and negative frequency modes accompanied by a weaker emission of modes that occurs in periodic bursts corresponding to the cavity round trips of the trapped modes. We then highlight a new regime in which the trapped mode spectra broaden until the zero-frequency points on the dispersion curve are reached. Amplification at the horizon is highest for zero-frequencies, therefore leading to a strong modification of the structure of the trapped light. For sufficiently long propagation times, lasing ensues only at the zero-frequency modes.Comment: accepted for publication in Classical and Quantum Gravit

TROPICAL FRUGIVOROUS BIRDS MOLT AND BREED IN RELATION TO THE AVAILABILITY OF FOOD RESOURCES

ABSTRACT ∙ Few studies have investigated how the abundance of food resources influences the phenology of the annual cycles of tropical birds. Frugivorous birds are good models for such investigation because the abundance of their main food types, fruits and arthropods, vary independently from each other. We investigated how the consumption and availability of fruits and arthropods are related to breeding and molt cycles of frugivorous birds in a fragmented landscape of the Brazilian Atlantic forest. We recorded the occurrence of brood patches and the molting of flight feathers in mist‐netted birds, from which we also analyzed the contents of fecal samples. Using nonparametric and parametric correlation tests we investigated the relationships among breeding and molt stage with the availability of fruits and arthropods. We found that the availability of fruits and arthropods fluctuates temporally and independently, but both food sources have shortage periods, apparently more pronounced for fruits. During periods when fruit was scarce, birds relied more heavily on arthropods as food. Incubation occurred when fruit availability was high, whereas the molt period that followed was coincident with the availability of arthropods. Although our observational study does not permit definite conclusions regarding the relationship between food availability and the timing of the annual cycle events investigated, it is suggestive that avian breeding and molt cycles coincide with fruit and arthropod availability, respectively. Together with arthropods, fruits are important for nestlings of frugivorous birds, and protein from arthropods may be especially important for the development of new feathers.RESUMO ∙ Relação entre disponibilidade de alimento, muda de penas e reprodução de aves frugívoras Poucos estudos abordaram a influência da abundância de recursos alimentares sobre a fenologia do ciclo anual de aves tropicais. Aves frugívoras são bons modelos para esse propósito porque as abundâncias dos seus principais alimentos, frutas e artrópodes, podem variar no tempo de maneira independente. Neste trabalho investigamos como os ciclos de muda de penas de voo e reprodução estão relacionados com a disponibilidade e o consumo de frutos e artrópodes em uma paisagem fragmentada de Mata Atlântica. Para isso registramos a ocorrência de placa de choco e mudas nas penas de voo de aves capturadas em redes de neblina e sua relação temporal com a disponibilidade de frutos e artrópodes amostrados nas áreas das redes. A disponibilidade de frutos e artrópodes apresentaram flutuações temporais independentes, porém ambos apresentaram períodos de escassez, aparentemente mais pronunciado para os frutos. Durante períodos de escassez de frutos, as aves consumiram mais artrópodes. O período de incubação ocorreu quando a disponibilidade de frutos era maior, enquanto a muda de penas coincidiu com o período de maior disponibilidade de artrópodes. Embora nosso estudo observacional não permita conclusões definitivas sobre a relação entre a disponibilidade de alimentos e os eventos de ciclo anual investigados, é sugestivoque os períodos de reprodução e muda tenham coincidido com maior disponibilidade de frutos e artrópodes, respectivamente. Juntamente com artrópodes, frutos podem ser importantes para a criação dos filhotes das aves frugívoras, enquanto proteína proveniente dos artrópodes pode ser especialmente importante para o desenvolvimento de novas penas.

Estudo comparativo de custos entre três tipos de lajes (maciça, vigota treliçada e nervurada com cubetas plásticas) da nova reitoria da Universidade Federal do Tocantins (UFT)

The slabs, which are almost always the elements with the largest volume and area of any building, have a great impact on the final cost of a structure. This work is a comparative study of costs between three types of slabs (massive, latticed joist and ribbed with plastic buckets) using the new Rectory of the Federal University of Tocantins (UFT) as an architectural reference. The work evaluated the impacts on the consumption of steel, form and concrete on the final costs of a five-story building when changing the types of slabs. The projects were developed with the Eberick software and the budget was based on the tables of SINAPI and ORSE. The projects were launched according to the architectural design of the Rectory of UFT made available by the UFT City Hall and pre-dimensioned based on the graphs and tables of Rebello (2000). In order to carry out the budget, both the price of the inputs and the service performed to carry them out were considered. Among the three types of slabs studied, the lattice slab was the cheapest because the greatest reduction in materials and when compared to the most expensive presented savings of 15.63%, followed by the massive slab with a reduction of 9.88% of the total value of the most expensive and finally the ribbed slab with plastic buckets, which obtained the highest value, presenting the highest consumption of inputs for the slabs, pillars and Shallow foundation, resulting in a cost of R$1,758,461.73.As lajes, que quase sempre são os elementos com maior volume e área de qualquer edificação, têm um grande impacto no custo final de uma estrutura. Esse trabalho é um estudo comparativo de custos entre três tipos de lajes (maciça, vigota treliçada e nervurada com cubetas plásticas) usando como referência arquitetônica a nova Reitoria da Universidade Federal do Tocantins (UFT). O trabalho avaliou os impactos no consumo de aço, forma e concreto nos custos finais de uma edificação de cinco pavimentos ao se trocar os tipos de lajes. Os projetos estruturais foram desenvolvidos com o software Eberick e a orçamentação se baseou nas tabelas do SINAPI e ORSE. Os projetos foram lançados segundo o projeto arquitetonico da Reitoria da UFT disponibilizados pela Prefeitura Universitária da UFT e pré dimensionados baseando-se nos gráficos e tabelas de Rebello (2000). Para a realização da orçamentação foram considerados tanto o preço dos insumos quanto o serviço necessários para realiza-los. Dentre os três tipos de lajes estudadas, a laje em vigota treliçada foi a mais barata pois permitiu a maior redução de materiais e quando comparada à mais cara apresentou uma economia de 15,63com uma redução de 9,88cubetas plásticas, que obteve o maior valor, apresentando o maior consumo de insumos para as lajes, pilares e sapatas, resultando assim em um custo de R$1.758.461,73

techno economic design of wind farms a methodology and multi scenario application

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TPLATE recruitment reveals endocytic dynamics at sites of symbiotic interface assembly in arbuscular mycorrhizal interactions

Introduction: Arbuscular mycorrhizal (AM) symbiosis between soil fungi and the majority of plants is based on a mutualistic exchange of organic and inorganic nutrients. This takes place inside root cortical cells that harbor an arbuscule: a highly branched intracellular fungal hypha enveloped by an extension of the host cell membrane—the perifungal membrane—which outlines a specialized symbiotic interface compartment. The perifungal membrane develops around each intracellular hypha as the symbiotic fungus proceeds across the root tissues; its biogenesis is the result of an extensive exocytic process and shows a few similarities with cell plate insertion which occurs at the end of somatic cytokinesis. Materials and Methods: We here analyzed the subcellular localization of a GFP fusion with TPLATE, a subunit of the endocytic TPLATE complex (TPC), a central actor in plant clathrin-mediated endocytosis with a role in cell plate anchoring with the parental plasma membrane. Results: Our observations demonstrate that Daucus carota and Medicago truncatula root organ cultures expressing a 35S::AtTPLATE-GFP construct accumulate strong fluorescent green signal at sites of symbiotic interface construction, along recently formed perifungal membranes and at sites of cell-to-cell hyphal passage between adjacent cortical cells, where the perifungal membrane fuses with the plasmalemma. Discussion: Our results strongly suggest that TPC-mediated endocytic processes are active during perifungal membrane interface biogenesis—alongside exocytic transport. This novel conclusion, which might be correlated to the accumulation of late endosomes in the vicinity of the developing interface, hints at the involvement of TPC-dependent membrane remodeling during the intracellular accommodation of AM fungi

toward a real time reconfiguration of self adaptive smart assembly systems

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towards optimum energy utilization by using the inverters for industrial production

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A design methodology for soft-core platforms on FPGA with SMP Linux, OpenMP support, and distributed hardware profiling system

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Counterpropagating frequency mixing with terahertz waves in diamond

Frequency conversion by means of Kerr-nonlinearity is one of the most common and exploited nonlinear optical processes in the UV, visible, IR and Mid-IR spectral regions. Here we show that wave mixing of an optical field and a Terahertz wave can be achieved in diamond, resulting in the frequency conversion of the THz radiation either by sum- or difference-frequency generation. In the latter case, we show that this process is phase-matched and most efficient in a counter-propagating geometry

CCD-based imaging and 3D space--time mapping of terahertz fields via Kerr frequency conversion

We investigate the spatially and temporally resolved four-wave mixing of terahertz (THz) fields and optical pulses in large-bandgap dielectrics, such as diamond. We show that it is possible to perform beam profiling and space–time resolved mapping of THz fields by encoding the spatial information into an optical signal, which can then be recorded by a standard CCD camera