414 research outputs found

    The mosses of Easter Island

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    The bryophyte flora of Easter Island has been poorly known primarily because few botanists have collected there. In order to increase the knowledge of the flora the two authors collected bryophytes from 12 localities on the island from April 28-May 3, 2000. The small island, which is south of the Tropic of Capricorn, is of volcanic origin and the volcanic soil as well as the destruction of most of the native flora have undoubtedly contributed to the paucity of bryophytes. The present study revealed that the bryophyte flora consists of only a few species, including one unidentifiable member of the Anthocerotaceae, 11 hepatics and 30 mosses. Eighteen mosses are new to the island. Three mosses, Chenia leptophylla (Müll. Hal.) R. H. Zander, Dicranella hawaiica (Müll. Hal.) Broth. and Tortella humilis (Hedw.) Jennings, are new for Chile, while three, Fissidens pascuanus Broth. in Skottsb., Ptychomitrium subcylindricum Thér. and Trematodon pascuanus Thér., are presently known to be endemic to Easter Island. Two of the three endemics, Fissidens pascuanus and Ptychomitrium subcylindricum, were rediscovered on the island. Fissidens pascuanus was found with sporophytes for the first time and a revised description of the species is provided

    The moss genus Isopterygium (Hypnaceae) in Latin America

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    The pleurocarpous moss genus Isopterygium (Hypnaceae) is revised for Latin America. Although as many as 92 species and varieties have been reported for the region over past years, these are currently accommodated by the present revision into only eight species. The most common taxon throughout most of Latin America, Isopterygium tenerum (Sw.) Mitt, is also the most polymorphic and presently 45 taxa are recognized as synonyms. The other seven species are I. affusum Mitt., I. acutifolium Irel., I. byssobolax Par., I. jamaicense Buck Broth., I. subglobosum Herz., and I. tenerifolium Mitt.

    Stimulating dynamic value: social capital and business incubation as a pathway to competitive success

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    Studies of business incubation tend to examine how managing the incubator can help incubating firms create value. In the past, emphasis has centred on the provision of core business services and the design of the incubator, but more recent approaches focus on the provision of a rich network through which an incubating firm can engage in collaborations. We argue that such provisions dictate only the opportunities for value creation; how incubating firms choose to behave and pursue network opportunities dictates the extent to which these opportunities can be realised and, thus, the value creation. Firms' destiny lies in the hands of their combinations of strategic networking activities, and incubation outcomes do not occur because of their mere presence in an incubator. We identify two value-stimulating behaviours (networking activities)—resource pooling activity (resource-seeking behaviour) and strategic network involvement (knowledge-seeking behaviour)—and develop a value matrix that classifies incubation into four types of outcomes on the basis of the extensive versus narrow combinations of these activities. Each incubation outcome has merits and can be used to inform the evaluation of incubating firms and the relational strategies of their managers

    Effects of Acquisitions on R&D Inputs and Outputs

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    Making acquisitions, although a popular strategy, may not always lead to positive firm performance. Researchers have offered several explanations for this relationship. One is that acquisitions lead to lower investments in R&D and curtail the championing process whereby organization members internally promote new products and processes in firms. The current research found that acquisitions had negative effects on R&D intensity and patent intensity

    Are Acquisitions a Poison Pill for Innovation?

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    The recent wave of acquisition activity may be damaging the innovative capabilities of American firms, thus making them less competitive in the global marketplace. In fact, acquisitions often serve as a substitute for innovation, which may cause further neglect of internal research and development (R&D) programs. Additionally, acquisitions often lead to increases in leverage, diversification, and absorb significant amounts of executive time, which may lead to reduced managerial commitment to innovation. In this article, evidence is presented suggesting that acquisition activity may result in reductions in R&D inputs and outputs. On average, the 191 firms in the sample reduced their allocations to R&D relative to their competitors following acquisitions. Furthermore, the firms also experienced reductions in the number of patents. Implications from this evidence are offered for executives and acquisition strategies. Specifically, based on our results, we propose that firms can compensate for the negative effects of acquisitions. Moreover, acquisitions, when properly planned and targeted, may enhance or complement a firm\u27s innovation processes. Firms should search for acquisitions that complement R&D projects, facilitate product commercialization and/or enhance their core competences

    Social capital and learning advantages: a problem of absorptive capacity

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    Theoretically, social capital allows entrepreneurial firms to capitalize on learning advantages of newness and gain access to knowledge as the foundation for improved performance. But this understates its complexity. We consider whether learning through social capital relationships has a direct effect on performance and whether absorptive capacity mediates and moderates this relationship. We find that network-based learning has no direct relationship with performance, but this is mediated in each instance by absorptive capacity and is moderated twice. Our findings challenge the learning advantages of newness thesis and reveal how absorptive capacity can enable business performance from a firm's network relationships

    Structure and morphology of ACEL ZnS:Cu,Cl phosphor powder etched by hydrochloric acid

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    © The Electrochemical Society, Inc. 2009. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version is available at the link below.Despite many researches over the last half century, the mechanism of ac powder electroluminescence remains to be fully elucidated and, to this end, a better understanding of the relatively complex structure of alternate current electroluminescence (ACEL) phosphors is required. Consequently, the structure and morphology of ZnS:Cu,Cl phosphor powders have been investigated herein by means of scanning electron microscopy (SEM) on hydrochloric acid-etched samples and X-ray powder diffraction. The latter technique confirmed that, as a result of two-stage firing during their synthesis, the phosphors were converted from the high temperature hexagonal (wurtzite) structure to the low temperature cubic (sphalerite) polymorph having a high density of planar stacking faults. Optical microscopy revealed that the crystal habit of the phosphor had the appearance of the hexagonal polymorph, which can be explained by the sphalerite pseudomorphing of the earlier wurtzite after undergoing the hexagonal to cubic phase transformation during the synthesis. SEM micrographs of the hydrochloric-etched phosphor particles revealed etch pits, a high density of planar stacking faults along the cubic [111] axis, and the pyramids on the (111) face. These observations were consistent with unidirectional crystal growth originating from the face showing the pyramids.EPSRC, DTI, and the Technology Strategy Board-led Technology Program

    Visible Light Photo-oxidation of Model Pollutants Using CaCu3Ti4O12: An Experimental and Theoretical Study of Optical Properties, Electronic Structure, and Selectivity

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    [Image: see text] Charge transfer between metal ions occupying distinct crystallographic sublattices in an ordered material is a strategy to confer visible light absorption on complex oxides to generate potentially catalytically active electron and hole charge carriers. CaCu(3)Ti(4)O(12) has distinct octahedral Ti(4+) and square planar Cu(2+) sites and is thus a candidate material for this approach. The sol−gel synthesis of high surface area CaCu(3)Ti(4)O(12) and investigation of its optical absorption and photocatalytic reactivity with model pollutants are reported. Two gaps of 2.21 and 1.39 eV are observed in the visible region. These absorptions are explained by LSDA+U electronic structure calculations, including electron correlation on the Cu sites, as arising from transitions from a Cu-hybridized O 2p-derived valence band to localized empty states on Cu (attributed to the isolation of CuO(4) units within the structure of CaCu(3)Ti(4)O(12)) and to a Ti-based conduction band. The resulting charge carriers produce selective visible light photodegradation of 4-chlorophenol (monitored by mass spectrometry) by Pt-loaded CaCu(3)Ti(4)O(12) which is attributed to the chemical nature of the photogenerated charge carriers and has a quantum yield comparable with commercial visible light photocatalysts

    THE USE OF HIGH BLOCKAGE RIBS TO ENHANCE HEAT TRANSFER COEFFICIENT DISTRIBUTIONS IN A MODEL OF AN INTEGRALLY CAST COOLING MANIFOLD

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    ABSTRACT In this paper detailed experimental measurements and computational predictions of heat transfer coefficient distributions in a large scale perspex model of a novel integrally cast blade cooling geometry are reported. In a gas turbine blade, the cooling passage investigated is integrally cast into the blade wall, providing good thermal contact with the outer surface of the turbine blade. Flow enters the racetrack passage through the root of the blade and exits to a central plenum through a series of nineteen transfer holes equally spaced in a staggered arrangement across the span of the blade. The Reynolds number changes continuously along the passage length because of the continuous ejection of fluid through a series of 19 transfer holes to the plenum. The smooth passage surface opposite is in closest proximity to the external surface, and this investigation has characterised the heat transfer coefficient on this surface at a range of engine representative inlet Reynolds numbers using a hybrid transient liquid crystal technique. The ability of three different rib configurations to enhance the heat transfer on this surface was also determined. Because the passage at engine scale is necessarily small, the rib height in all cases was 32.5% of the passage height. As the entire passage wetted surface is able to contribute to the blade cooling, and knowledge of the heat transfer coefficient distribution on the holed surfaces is crucial to prediction of blade life, a commercial CFD package, Fluent, was used to predict the heat transfer coefficient distributions on the holed surface, where there was no optical access during these tests. This also allowed investigation of additional rib configurations, and comparison of the pressure penalty associated with each design. The study showed that the turbulator configuration used allows the position and maximum level of heat transfer coefficient enhancement to be chosen by the engine designer. For the configurations tested heat transfer coefficient enhancement of up to 32% and 51% could be achieved on the holed surface and the ribbed surface respectively. For minimum additional pressure drop 45° ribs should be used
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