105 research outputs found

    Self-consistent quantal treatment of decay rates within the perturbed static path approximation

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    The framework of the Perturbed Static Path Approximation (PSPA) is used to calculate the partition function of a finite Fermi system from a Hamiltonian with a separable two body interaction. Therein, the collective degree of freedom is introduced in self-consistent fashion through a Hubbard-Stratonovich transformation. In this way all transport coefficients which dominate the decay of a meta-stable system are defined and calculated microscopically. Otherwise the same formalism is applied as in the Caldeira-Leggett model to deduce the decay rate from the free energy above the so called crossover temperature T0T_0.Comment: 17 pages, LaTex, no figures; final version, accepted for publication in PRE; e-mail: [email protected]

    Electronic entropy, shell structure, and size-evolutionary patterns of metal clusters

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    We show that electronic-entropy effects in the size-evolutionary patterns of relatively small (as small as 20 atoms), simple-metal clusters become prominent already at moderate temperatures. Detailed agreement between our finite-temperature-shell-correction-method calculations and experimental results is obtained for certain temperatures. This agreement includes a size-dependent smearing out of fine-structure features, accompanied by a measurable reduction of the heights of the steps marking major-shell and subshell closings, thus allowing for a quantitative analysis of cluster temperatures.Comment: Latex/Revtex, 4 pages with 3 Postscript figure

    Bloom dynamics of an exceptional red tide of the toxigenic dinoflagellate

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    The toxic dinoflagellate Alexandrium minutum generally proliferates in semi-enclosed sites such as estuaries, harbours and lagoons, where stratification, restricted circulation and accumulation of resting cysts set suitable conditions for its development. In the Galician RĂ­as (NW Iberian Peninsula), its blooms follow also this pattern. They are recurrent in small, shallow estuarine bays inside the RĂ­as, but rarely detected, and if so in minor amount, out of these areas. However, a massive proliferation of A. minutum from June to July 2018 in the RĂ­as Baixas (Vigo and Pontevedra) changed this picture. The bloom initiated in semi-enclosed waters, as previously described for this species, but thereafter spread to the whole embayments where persisted more than one month. It generated a noticeable red tide with disperse patches that became heavily concentrated inside the port of Vigo. During that period shellfish harvesting closures and paralytic shellfish toxins in certain marine invertebrates and fish were reported for the first time in Spain. Meteorological conditions (higher than usual rains/runoff, sustained temperature increment and oscillating wind pattern promoting a series of upwelling-relaxation cycles) fostered optimal circumstances for the outbreak of A. minutum: strong vertical stratification and the alternation of retention and dispersion processes. Simulations from a particle tracking model portrayed the observed bloom development phases: onset, transport within the surface layer towards the interior parts of the RĂ­a of Vigo, and dispersion all over the embayment. High concentrations of resting cysts were detected several months after the bloom, which may have favoured flourish of A. minutum in the following years, markedly in 2020

    HABs in coastal upwelling systems: Insights from an exceptional red tide of the toxigenic dinoflagellate Alexandrium minutum

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    Alexandrium minutum blooms generally occur in semi-enclosed sites such as estuaries, harbours and lagoons, where enhanced stratification, restricted circulation and accumulation of resting cysts in the sediment set suitable habitat conditions for the proliferation of this paralytic shellfish poisoning toxigenic species. In the Galician Rías Baixas (NW Iberian Peninsula), according to weekly time-series between 1994 and 2020, blooms of A. minutum were recurrent in small, shallow estuarine bays inside the Rías de Vigo and Pontevedra, but rarely detected, and if so at low concentrations, out of these environments. However, from May to July 2018 it developed as usual in the small inner bays but then spread over both Rías (Vigo and Pontevedra) causing discoloured waters during one month and prolonged harvesting closures. Meteorological conditions during that period (rains / runoff higher than climatological averages, sustained temperature increment and oscillating wind pattern –i.e., series of upwelling-relaxation cycles), fostered optimal circumstances for the development of that extensive and massive proliferation: strong vertical stratification and the alternation of retention and dispersion processes. Simulations from a particle tracking model portrayed the observed bloom development phases: onset and development inside a small inner bay; transport within the surface layer, from these sites towards the interior parts of the Ría; and dispersion all over the embayment. Seedbeds with high concentrations of resting cysts were detected several months after the bloom, which may have favoured flourishment of A. minutum in the following two years, markedly in 2020. The present work contributes to the general understanding of the dynamics of harmful algal blooms (HABs), from which surveillance indicators of the state of marine ecosystems and their evolution can be derived. We hypothesize that the intensity and frequency of A. minutum proliferations in the Galician Rías could increase under projected climate trends.Postprint2,69

    Reliability of infrared thermography in skin temperature evaluation of wheelchair users

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    To examine the reliability of infrared thermography (IRT) in wheelchair users (WCUs), as a noninvasive and risk-free technique to detect the natural thermal radiation emitted by human skin and to allow subsequent interpretations of temperature distributions

    Mesenchymal stem/stromal cells as a delivery platform in cell and gene therapies

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    International Alliance Strategies: A Case Study of the Indonesian Medical Device Industry

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    This study aims to investigate how the multinational corporations form alliance strategies with local businesses under the dynamic institutional environment in the Indonesian context. We used a qualitative approach with a case study of the medical device industry to examine how the institutional environment affects the choice of the strategic alliance. By collecting the qualitative data, including interviews, observations and archival data, the interpretive approach was adopted to understand social worlds from the point of view of participants. We identified five types of alliance strategies: the wholly owned subsidiary with contractual collaboration, the wholly owned subsidiary with the licence agreement, the international trade with the licence agreement, joint venture and outsourcing. There are also two main issues of the institutional environments that determine the choice of alliance strategic: the restriction for foreign companies to carry out direct selling and the new policy that introduces the electronic procurement system. This study provides evidence of the role of the institutional environment on collaboration strategies between the multinational enterprises from the developed countries and the local distributors from Indonesia. The results extend the concept of international business in the Asian context
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