857 research outputs found

    New Distribution Records for Mosquitoes in Michigan (Diptera: Culicidae)

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    (excerpt) Since the late 1940\u27s very little information has appeared in the literature dealing with the geographical distribution of mosquitoes in Michigan. The earliest attempt at establish- ing a comprehensive list of species was made by Irwin (1941) who catalogued 43 species by county. A survey by Pederson (1947) resulted in the collection of 48 species and provided the most extensive distribution list of mosquitoes in Michigan. Recent studies by Newson et al. (1975), McGroarty et al. (1976) and Grimstad (1977) have contributed several new distribution and state records. Prompted by the 1975 St. Louis encephalitis outbreak in Michigan, and a lack of current information on the species of mosquitoes in Isabella County, a survey of mosquitoes was conducted in the Mount Pleasant area

    Control of macrophytes by grass carp (ctenopharyngodon idella) in a Waikato drain, New Zealand

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    Hornwort (Ceratophyllum demersum L.) and other aquatic macrophytes have historically been mechanically removed from the Rangiriri drain and Churchill East drain to maintain drain efficiency. As an alternative control method for the high plant biomass that accumulates at the end of summer, the effect of stocking diploid grass carp (Ctenopharyngodon idella L.) on the aquatic vegetation was evaluated in these Waikato drainage systems. At the start of the trial, both drains had a low diversity of aquatic macrophytes, and of the nine species (including the emergents), seven were exotic. Two months after grass carp were released to Churchill East drain (the treated drain) the four submerged and floating macrophyte species became scarce in the main drain. Over the same period, these species increased in biomass in Rangiriri drain (the untreated drain), where hornwort became dense and surface-reaching and remained so for the duration of the trial. However, grass carp did not control submerged vegetation in smaller side drains or the shallow, upper parts of the main drain, or the marginal sprawling species and emergent species. The cost of leasing the grass carp was similar to the cost of clearing the drains mechanically, but grass carp provided continuous weed control. However, subsequent to this trial, 62 dead grass carp were found in Churchill East drain in February 2001, and weed cover subsequently increased. This illustrates that grass carp management in New Zealand agricultural drains can be problematic due to periodic fish kills

    Constructing Lifshitz solutions from AdS

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    Under general assumptions, we show that a gravitational theory in d+1 dimensions admitting an AdS solution can be reduced to a d-dimensional theory containing a Lifshitz solution with dynamical exponent z=2. Working in a d=4, N=2 supergravity setup, we prove that if the AdS background is N=2 supersymmetric, then the Lifshitz geometry preserves 1/4 of the supercharges, and we construct the corresponding Killing spinors. We illustrate these results in examples from supersymmetric consistent truncations of type IIB supergravity, enhancing the class of known 4-dimensional Lifshitz solutions of string theory. As a byproduct, we find a new AdS4 x S1 x T(1,1) solution of type IIB.Comment: 29 pages, no figures; v2 minor corrections, a reference adde

    Effects of polysaccharide-based edible coatings enriched with dietary fiber on quality attributes of fresh-cut apples

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    Little information is available regarding the incorporation of dietary fiber into edible films and coatings. In this work, apple fiber and inulin were incorporated into polysaccharide-based (alginate, pectine and gellan gum) edible coating formulations and their effects on the quality attributes of fresh-cut apples were evaluated. Antioxidant properties, color, firmness, sensory quality and microbial growth of fresh-cut apple were studied during 16 days of storage at 4 A degrees C. Results show that dietary fiber extracts incorporated to gellan gum, pectin and alginate-based coatings together with calcium chloride and ascorbic acid successfully maintained the firmness and color of coated fresh-cut apples in comparison with uncoated control samples, which presented severe texture softening and browning. The firmness of apple pieces coated with polysaccharide-based coating formulations incorporating apple fiber doubled, and sometimes tripled, that of uncoated samples. Any of the assayed coatings exhibited a positive effect on the sensory properties of fresh-cut apples. The incorporation of apple fiber, together with the use of ascorbic acid, contributed to keep the antioxidant potential of the fruit at least during the first week of storage. Furthermore, gellan gum coatings had a marked effect in reducing mesophilic and psychrophilic counts on fresh-cut apples throughout storage regardless the addition of dietary fibers. The results achieved demonstrate the feasibility of the addition of dietary fiber to edible coating formulations for increasing the nutritional value of fresh-cut apples without compromising their fresh-like quality attributes.This work was supported by Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT, Argentina) and by Spanish Ministry of Economy and Competitiveness, through the project AGL2010-21572. An ICREA Academia Award is also acknowledged

    Gold nanoparticles on nanodiamond for nanophotonic applications

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    We present here some recent results of a research focused on the prepn. of detonation nanodiamond/Au nanoparticles hybrid materials. Two different exptl. routes are followed for the decoration of diamond nanoparticles by Au nanoparticles, that are in turn prepd. by an innovative electroless approach. Structure and morphol. at the nanoscale level of the Au-on-nanodiamond deposits have been deeply investigated by electron microscopy (FE-SEM, HR-TEM) and diffraction (XRD) techniques. Optical properties of these systems have been detd. by performing scattering and UV-Vis absorption measurements, and by comparing the exptl. data with simulated extinction spectra. The results highlighted very interesting plasmonic and scattering behaviors, mainly related to the high refractive index of diamond

    de Sitter Supersymmetry Revisited

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    We present the basic N=1\mathcal{N} =1 superconformal field theories in four-dimensional de Sitter space-time, namely the non-abelian super Yang-Mills theory and the chiral multiplet theory with gauge interactions or cubic superpotential. These theories have eight supercharges and are invariant under the full SO(4,2)SO(4,2) group of conformal symmetries, which includes the de Sitter isometry group SO(4,1)SO(4,1) as a subgroup. The theories are ghost-free and the anti-commutator α{Qα,Qα}\sum_\alpha\{Q_\alpha, Q^{\alpha\dagger}\} is positive. SUSY Ward identities uniquely select the Bunch-Davies vacuum state. This vacuum state is invariant under superconformal transformations, despite the fact that de Sitter space has non-zero Hawking temperature. The N=1\mathcal{N}=1 theories are classically invariant under the SU(2,21)SU(2,2|1) superconformal group, but this symmetry is broken by radiative corrections. However, no such difficulty is expected in the N=4\mathcal{N}=4 theory, which is presented in appendix B.Comment: 21 pages, 2 figure

    Heterotic Flux Attractors

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    We find attractor equations describing moduli stabilization for heterotic compactifications with generic SU(3)-structure. Complex structure and K\"ahler moduli are treated on equal footing by using SU(3)xSU(3)-structure at intermediate steps. All independent vacuum data, including VEVs of the stabilized moduli, is encoded in a pair of generating functions that depend on fluxes alone. We work out an explicit example that illustrates our methods.Comment: 37 pages, references and clarifications adde

    Consistent reduction of charged D3-D7 systems

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    We provide a consistent reduction to five dimensions of the system of D3-branes at Calabi-Yau singularities coupled to D7-branes with world-volume gauge flux. The D3-branes source the dual to would-be conformal quiver theories. The D7-branes, which are homogeneously distributed in their transverse directions, are dual to massless matter in the fundamental representation at finite (baryon) density. We provide the five-dimensional action and equations of motion, and discuss a few sub-truncations. The reduction can be used in the study of transport properties and stability of D3-D7 charged systems.Comment: 23 pages. v2: references added and minor change

    Hypermoduli Stabilization, Flux Attractors, and Generating Functions

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    We study stabilization of hypermoduli with emphasis on the effects of generalized fluxes. We find a class of no-scale vacua described by ISD conditions even in the presence of geometric flux. The associated flux attractor equations can be integrated by a generating function with the property that the hypermoduli are determined by a simple extremization principle. We work out several orbifold examples where all vector moduli and many hypermoduli are stabilized, with VEVs given explicitly in terms of fluxes.Comment: 45 pages, no figures; Version submitted to JHE

    Holographic Renormalization for z=2 Lifshitz Space-Times from AdS

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    Lifshitz space-times with critical exponent z=2 can be obtained by dimensional reduction of Schroedinger space-times with critical exponent z=0. The latter space-times are asymptotically AdS solutions of AdS gravity coupled to an axion-dilaton system and can be uplifted to solutions of type IIB supergravity. This basic observation is used to perform holographic renormalization for 4-dimensional asymptotically z=2 locally Lifshitz space-times by Scherk-Schwarz dimensional reduction of the corresponding problem of holographic renormalization for 5-dimensional asymptotically locally AdS space-times coupled to an axion-dilaton system. We can thus define and characterize a 4-dimensional asymptotically locally z=2 Lifshitz space-time in terms of 5-dimensional AdS boundary data. In this setup the 4-dimensional structure of the Fefferman-Graham expansion and the structure of the counterterm action, including the scale anomaly, will be discussed. We find that for asymptotically locally z=2 Lifshitz space-times obtained in this way there are two anomalies each with their own associated nonzero central charge. Both anomalies follow from the Scherk--Schwarz dimensional reduction of the 5-dimensional conformal anomaly of AdS gravity coupled to an axion-dilaton system. Together they make up an action that is of the Horava-Lifshitz type with nonzero potential term for z=2 conformal gravity.Comment: 32 pages, v2: modified discussion of the central charge
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