621 research outputs found

    Intrapopulational chromosome number variation in Zephyranthes sylvatica Baker (Amaryllidaceae: Hippeastreae) from northeast Brazil.

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    Zephyranthes Herb. is a taxonomically complex and cytologically variable group, withabout 65 species of Neotropical distribution. Chromosome number variability in 32 individuals of a Zephyranthes sylvaticapopulation from Northeast Brazil was investigated. Three cytotypes were found: 2n = 12 (one metacentric, four submetacentricand one acrocentric pairs), in 24 individuals; 2n = 12 + 1B, in five and three individuals with 2n = 18, a triploid cytotype.All diploid individuals showed chromosomes with polymorphism in pair one and two, while in triploids this polymorphismwas observed in all chromosome triplets, generally with two homomorphic chromosomes and a higher or lower heteromorphicchromosome. All individuals had reticulated interfasic nucleus and a slightly asymmetric chromosome complement, withone metacentric chromosome pair and the others more submetacentric to acrocentric. These data confirm the cytologicalvariability previously registered for the genus. Mechanisms involved in karyotypic evolution in this population are discussed

    Geometry and quantum delocalization of interstitial oxygen in silicon

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    The problem of the geometry of interstitial oxygen in silicon is settled by proper consideration of the quantum delocalization of the oxygen atom around the bond-center position. The calculated infrared absorption spectrum accounts for the 517 and 1136 cm−1^{-1} bands in their position, character, and isotope shifts. The asymmetric lineshape of the 517 cm−1^{-1} peak is also well reproduced. A new, non-infrared-active, symmetric-stretching mode is found at 596 cm−1^{-1}. First-principles calculations are presented supporting the nontrivial quantum delocalization of the oxygen atom.Comment: uuencoded, compressed postscript file for the whole. 4 pages (figures included), accepted in PR

    Gymnosperms on the EDGE

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    Driven by limited resources and a sense of urgency, the prioritization of species for conservation has been a persistent concern in conservation science. Gymnosperms (comprising ginkgo, conifers, cycads, and gnetophytes) are one of the most threatened groups of living organisms, with 40% of the species at high risk of extinction, about twice as many as the most recent estimates for all plants (i.e. 21.4%). This high proportion of species facing extinction highlights the urgent action required to secure their future through an objective prioritization approach. The Evolutionary Distinct and Globally Endangered (EDGE) method rapidly ranks species based on their evolutionary distinctiveness and the extinction risks they face. EDGE is applied to gymnosperms using a phylogenetic tree comprising DNA sequence data for 85% of gymnosperm species (923 out of 1090 species), to which the 167 missing species were added, and IUCN Red List assessments available for 92% of species. The effect of different extinction probability transformations and the handling of IUCN data deficient species on the resulting rankings is investigated. Although top entries in our ranking comprise species that were expected to score well (e.g. Wollemia nobilis, Ginkgo biloba), many were unexpected (e.g. Araucaria araucana). These results highlight the necessity of using approaches that integrate evolutionary information in conservation science

    Empresa MASAME

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    En el siguiente documento se presenta el trabajo realizado en el Proyecto de AplicaciĂłn Profesional ConsultorĂ­a para la Competitividad (PAP CC) en el cual se intervino a la empresa, basĂĄndonos en el diagnĂłstico que realizĂł el equipo de primavera 2022 nos dimos cuenta de que habĂ­a 3 ĂĄreas de mejora importante, estrategia, gestiĂłn de mercado y sistemas de calidad. Por cuestiones de tiempo, decidimos enfocarnos en una sola ĂĄrea para entregar resultados completos y de calidad. Tras las visitas a la empresa y el anĂĄlisis previo nos dimos cuenta de que la empresa no podrĂ­a mejorar su gestiĂłn de mercado y los sistemas de calidad si no contaban con una estrategia bien definida, por lo que se tomĂł la decisiĂłn de definir y mejorar la estrategia de esta. Uno de los productos para la empresa fue la propuesta de un organigrama, con la finalidad de que puedan ver lo que ya tienen y tambiĂ©n considerar que es lo que les falta para cubrir todas las necesidades de la empresa. La segunda propuesta realizada fue una visiĂłn y una misiĂłn mĂĄs profunda y completa. Estos aspectos son los que le dan una razĂłn de ser a la empresa y una razĂłn de estar a los empleados por lo que tienen que inspirar y guiar. TambiĂ©n se trabajĂł en desarrollar el Business Model Canvas el cual plasma de manera visual la idea, los componentes y los participantes fundamentales de la empresa. Por Ășltimo, se realizĂł un formato financiero que proporciona indicadores para ayudar en la toma de decisiones.ITESO, A.C

    Heralded quantum entanglement between two crystals

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    Quantum networks require the crucial ability to entangle quantum nodes. A prominent example is the quantum repeater which allows overcoming the distance barrier of direct transmission of single photons, provided remote quantum memories can be entangled in a heralded fashion. Here we report the observation of heralded entanglement between two ensembles of rare-earth-ions doped into separate crystals. A heralded single photon is sent through a 50/50 beamsplitter, creating a single-photon entangled state delocalized between two spatial modes. The quantum state of each mode is subsequently mapped onto a crystal, leading to an entangled state consisting of a single collective excitation delocalized between two crystals. This entanglement is revealed by mapping it back to optical modes and by estimating the concurrence of the retrieved light state. Our results highlight the potential of rare-earth-ions doped crystals for entangled quantum nodes and bring quantum networks based on solid-state resources one step closer.Comment: 10 pages, 5 figure

    The stable free rank of symmetry of products of spheres

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    A well known conjecture in the theory of transformation groups states that if p is a prime and (Z/p)^r acts freely on a product of k spheres, then r is less than or equal to k. We prove this assertion if p is large compared to the dimension of the product of spheres. The argument builds on tame homotopy theory for non simply connected spaces.Comment: 30 pages; improved exposition, some details adde

    Forced Solid-State Interactions for the Selective “Turn-On” Fluorescence Sensing of Aluminum Ions in Water Using a Sensory Polymer Substrate

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    Selective and sensitive solid sensory substrates for detecting Al(III) in pure water are reported. The material is a flexible polymer film that can be handled and exhibits gel behavior and membrane performance. The film features a chemically anchored salicylaldehyde benzoylhydrazone derivative as an aluminum ion fluorescence sensor. A novel procedure for measuring Al(III) at the ppb level using a single solution drop in 20 min was developed. In this procedure, a drop was allowed to enter the hydrophilic material for 15 min before a 5 min drying period. The process forced the Al(III) to interact with the sensory motifs within the membrane before measuring the fluorescence of the system. The limit of detection of Al(III) was 22 ppm. Furthermore, a water-soluble sensory polymer containing the same sensory motifs was developed with a limit of detection of Al(III) of 1.5 ppb, which was significantly lower than the Environmental Protection Agency recommendations for drinking water.Spanish Ministerio de Economía y Competitividad-Feder (MAT2011-22544) and by the Consejería de Educación - Junta de Castilla y León (BU232U13)

    A hybrid method for accurate iris segmentation on at-a-distance visible-wavelength images

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    [EN] This work describes a new hybrid method for accurate iris segmentation from full-face images independently of the ethnicity of the subject. It is based on a combination of three methods: facial key-point detection, integro-differential operator (IDO) and mathematical morphology. First, facial landmarks are extracted by means of the Chehra algorithm in order to obtain the eye location. Then, the IDO is applied to the extracted sub-image containing only the eye in order to locate the iris. Once the iris is located, a series of mathematical morphological operations is performed in order to accurately segment it. Results are obtained and compared among four different ethnicities (Asian, Black, Latino and White) as well as with two other iris segmentation algorithms. In addition, robustness against rotation, blurring and noise is also assessed. Our method obtains state-of-the-art performance and shows itself robust with small amounts of blur, noise and/or rotation. 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