406 research outputs found
Controlling trapping potentials and stray electric fields in a microfabricated ion trap through design and compensation
Recent advances in quantum information processing with trapped ions have
demonstrated the need for new ion trap architectures capable of holding and
manipulating chains of many (>10) ions. Here we present the design and detailed
characterization of a new linear trap, microfabricated with scalable
complementary metal-oxide-semiconductor (CMOS) techniques, that is well-suited
to this challenge. Forty-four individually controlled DC electrodes provide the
many degrees of freedom required to construct anharmonic potential wells,
shuttle ions, merge and split ion chains, precisely tune secular mode
frequencies, and adjust the orientation of trap axes. Microfabricated
capacitors on DC electrodes suppress radio-frequency pickup and excess
micromotion, while a top-level ground layer simplifies modeling of electric
fields and protects trap structures underneath. A localized aperture in the
substrate provides access to the trapping region from an oven below, permitting
deterministic loading of particular isotopic/elemental sequences via
species-selective photoionization. The shapes of the aperture and
radio-frequency electrodes are optimized to minimize perturbation of the
trapping pseudopotential. Laboratory experiments verify simulated potentials
and characterize trapping lifetimes, stray electric fields, and ion heating
rates, while measurement and cancellation of spatially-varying stray electric
fields permits the formation of nearly-equally spaced ion chains.Comment: 17 pages (including references), 7 figure
Introgressive hybridisation between domestic pigs (<i>Sus scrofa domesticus</i>) and endemic Corsican wild boars (<i>S. s. meridionalis</i>):Effects of human-mediated interventions
Owing to the intensified domestication process with artificial trait selection, introgressive hybridisation between domestic and wild species poses a management problem. Traditional free-range livestock husbandry, as practiced in Corsica and Sardinia, is known to facilitate hybridisation between wild boars and domestic pigs (Sus scrofa). Here, we assessed the genetic distinctness and genome-wide domestic pig ancestry levels of the Corsican wild boar subspecies S. s. meridionalis, with reference to its Sardinian conspecifics, employing a genome-wide single nucleotide polymorphism (SNP) assay and mitochondrial control region (mtCR) haplotypes. We also assessed the reliance of morphological criteria and the melanocortin-1 receptor (MC1R) coat colour gene to identify individuals with domestic introgression. While Corsican wild boars showed closest affinity to Sardinian and Italian wild boars compared to other European populations based on principal component analysis, the observation of previously undescribed mtCR haplotypes and high levels of nuclear divergence (Weir's θ > 0.14) highlighted the genetic distinctness of Corsican S. s. meridionalis. Across three complementary analyses of mixed ancestry (i.e., STRUCTURE, PCADMIX, and ELAI), proportions of domestic pig ancestry were estimated at 9.5% in Corsican wild boars, which was significantly higher than in wild boars in Sardinia, where free-range pig keeping was banned in 2012. Comparison of morphologically pure- and hybrid-looking Corsican wild boars suggested a weak correlation between morphological criteria and genome-wide domestic pig ancestry. The study highlights the usefulness of molecular markers to assess the direct impacts of management practices on gene flow between domestic and wild species
Granular Packings: Nonlinear elasticity, sound propagation and collective relaxation dynamics
Experiments on isotropic compression of a granular assembly of spheres show
that the shear and bulk moduli vary with the confining pressure faster than the
1/3 power law predicted by Hertz-Mindlin effective medium theories (EMT) of
contact elasticity. Moreover, the ratio between the moduli is found to be
larger than the prediction of the elastic theory by a constant value. The
understanding of these discrepancies has been a longstanding question in the
field of granular matter. Here we perform a test of the applicability of
elasticity theory to granular materials. We perform sound propagation
experiments, numerical simulations and theoretical studies to understand the
elastic response of a deforming granular assembly of soft spheres under
isotropic loading. Our results for the behavior of the elastic moduli of the
system agree very well with experiments. We show that the elasticity partially
describes the experimental and numerical results for a system under
compressional loads. However, it drastically fails for systems under shear
perturbations, particularly for packings without tangential forces and
friction. Our work indicates that a correct treatment should include not only
the purely elastic response but also collective relaxation mechanisms related
to structural disorder and nonaffine motion of grains.Comment: 21 pages, 13 figure
Demonstration of integrated microscale optics in surface-electrode ion traps
In ion trap quantum information processing, efficient fluorescence collection
is critical for fast, high-fidelity qubit detection and ion-photon
entanglement. The expected size of future many-ion processors require scalable
light collection systems. We report on the development and testing of a
microfabricated surface-electrode ion trap with an integrated high numerical
aperture (NA) micromirror for fluorescence collection. When coupled to a low NA
lens, the optical system is inherently scalable to large arrays of mirrors in a
single device. We demonstrate stable trapping and transport of 40Ca+ ions over
a 0.63 NA micromirror and observe a factor of 1.9 enhancement in photon
collection compared to the planar region of the trap.Comment: 15 pages, 8 figure
Fatores de produção na cultura do milho sob efeito de doses e queima de resĂduos orgânicos.
Os resĂduos orgânicos quando corretamente manejados e utilizados revertem-se em fornecedores de nutrientes e condicionadores das propriedades fĂsicas e biolĂłgicas do solo, garantindo ambiente adequado para o desenvolvimento do sistema radicular das plantas por uma lado e aumentando a produção de alimentos, fibras e energia, por outro. O aproveitamento agrĂcola dos resĂduos de podas das árvores das cidades, na forma de composto orgânico ou in natura tem sido apontado como uma solução adequada, uma vez que, proporciona a liberação de nutrientes para as plantas semcausar grande impacto..
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