958 research outputs found

    Contribution of advanced regeneration of Pinus Radiata D. Don. to transpiration by a fragment of Native forest in central Chile is out of proportion with the contribution to sapwood area

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    The transpiration of Nothofagus glauca (Phil.) Krasser and advanced Pinus radiata D. Don. regeneration was measured in a fragment of native N. glauca forest. Over the eight months of this study, P. radiata contributed approximately 60% of the total stand transpiration. This was out of proportion with the approximately 34% of the stand sapwood area contributed by P. radiata. This was due to the significantly greater sap flux density of the P. radiata compared to the N. glauca between May and October. Though the results are from a small study conducted as part of a larger experiment, it is argued that they suggest that invasion by P. radiata may substantially increase the risk from climate change to reserves of N. glauca forest in the Maule region of central Chile. In some reserves of N. glauca forest, Forestal Arauco S.A. manually removed P. radiata that regenerated after the wildfire of January 2017. This was a costly operation and there is a need for indices to assess competition. The ratio of sapwood area to leaf area is suggested as a potential index for assessing competition to identify stands at risk. © 2020 by the author

    Contribution of advanced regeneration of Pinus Radiata D. Don. to transpiration by a fragment of Native forest in central Chile is out of proportion with the contribution to sapwood area

    Get PDF
    The transpiration of Nothofagus glauca (Phil.) Krasser and advanced Pinus radiata D. Don. regeneration was measured in a fragment of native N. glauca forest. Over the eight months of this study, P. radiata contributed approximately 60% of the total stand transpiration. This was out of proportion with the approximately 34% of the stand sapwood area contributed by P. radiata. This was due to the significantly greater sap flux density of the P. radiata compared to the N. glauca between May and October. Though the results are from a small study conducted as part of a larger experiment, it is argued that they suggest that invasion by P. radiata may substantially increase the risk from climate change to reserves of N. glauca forest in the Maule region of central Chile. In some reserves of N. glauca forest, Forestal Arauco S.A. manually removed P. radiata that regenerated after the wildfire of January 2017. This was a costly operation and there is a need for indices to assess competition. The ratio of sapwood area to leaf area is suggested as a potential index for assessing competition to identify stands at risk. © 2020 by the author

    Universal quantum gates based on both geometric and dynamic phases in quantum dots

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    A large-scalable quantum computer model, whose qubits are represented by the subspace subtended by the ground state and the single exciton state on semiconductor quantum dots, is proposed. A universal set of quantum gates in this system may be achieved by a mixed approach, composed of dynamic evolution and nonadibatic geometric phase.Comment: 4 pages, to appear in Chin. Phys. Let

    Bundle Theory of Improper Spin Transformations

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    {\it We first give a geometrical description of the action of the parity operator (P^\hat{P}) on non relativistic spin 12{{1}\over{2}} Pauli spinors in terms of bundle theory. The relevant bundle, SU(2)Z2O(3)SU(2)\odot \Z_2\to O(3), is a non trivial extension of the universal covering group SU(2)SO(3)SU(2)\to SO(3). P^\hat{P} is the non relativistic limit of the corresponding Dirac matrix operator P=iγ0{\cal P}=i\gamma_0 and obeys P^2=1\hat{P}^2=-1. Then, from the direct product of O(3) by Z2\Z_2, naturally induced by the structure of the galilean group, we identify, in its double cover, the time reversal operator (T^\hat{T}) acting on spinors, and its product with P^\hat{P}. Both, P^\hat{P} and T^\hat{T}, generate the group Z4×Z2\Z_4 \times \Z_2. As in the case of parity, T^\hat{T} is the non relativistic limit of the corresponding Dirac matrix operator T=γ3γ1{\cal T}=\gamma^3 \gamma^1, and obeys T^2=1\hat{T}^2=-1.}Comment: 8 pages, Plaintex; titled changed, minor text modifications, one reference complete

    Quantum decoherence of excitons in a leaky cavity with quasimode

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    For the excitons in the quantum well placed within a leaky cavity, the quantum decoherence of a mesoscopically superposed states is investigated based on the factorization theory for quantum dissipation. It is found that the coherence of the exciton superposition states will decrease in an oscillating form when the cavity field interacting with the exciton is of the form of quasimode. The effect of the thermal cavity fields on the quantum decoherence of the superposition states of the exciton is studied and it is observed that the higher the temperature of the environment is, the shorter the decoherence characteristic time is.Comment: 1 figure, 7 page

    Alpha-synuclein targets GluN2A NMDA receptor subunit causing striatal synaptic dysfunction and visuospatial memory alteration

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    Parkinson's disease is a progressive neurodegenerative disorder characterized by altered striatal dopaminergic signalling that leads to motor and cognitive deficits. Parkinson's disease is also characterized by abnormal presence of soluble toxic forms of \u3b1-synuclein that, when clustered into Lewy bodies, represents one of the pathological hallmarks of the disease. However, \u3b1-synuclein oligomers might also directly affect synaptic transmission and plasticity in Parkinson's disease models. Accordingly, by combining electrophysiological, optogenetic, immunofluorescence, molecular and behavioural analyses, here we report that \u3b1-synuclein reduces N-methyl-d-aspartate (NMDA) receptor-mediated synaptic currents and impairs corticostriatal long-term potentiation of striatal spiny projection neurons, of both direct (D1-positive) and indirect (putative D2-positive) pathways. Intrastriatal injections of \u3b1-synuclein produce deficits in visuospatial learning associated with reduced function of GluN2A NMDA receptor subunit indicating that this protein selectively targets this subunit both in vitro and ex vivo. Interestingly, this effect is observed in spiny projection neurons activated by optical stimulation of either cortical or thalamic glutamatergic afferents. We also found that treatment of striatal slices with antibodies targeting \u3b1-synuclein prevents the \u3b1-synuclein-induced loss of long-term potentiation and the reduced synaptic localization of GluN2A NMDA receptor subunit suggesting that this strategy might counteract synaptic dysfunction occurring in Parkinson's disease

    A Fast and Reliable Method for Simultaneous Waveform, Amplitude and Latency Estimation of Single-Trial EEG/MEG Data

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    The amplitude and latency of single-trial EEG/MEG signals may provide valuable information concerning human brain functioning. In this article we propose a new method to reliably estimate single-trial amplitude and latency of EEG/MEG signals. The advantages of the method are fourfold. First, no a-priori specified template function is required. Second, the method allows for multiple signals that may vary independently in amplitude and/or latency. Third, the method is less sensitive to noise as it models data with a parsimonious set of basis functions. Finally, the method is very fast since it is based on an iterative linear least squares algorithm. A simulation study shows that the method yields reliable estimates under different levels of latency variation and signal-to-noise ratioÕs. Furthermore, it shows that the existence of multiple signals can be correctly determined. An application to empirical data from a choice reaction time study indicates that the method describes these data accurately

    Exposure to green areas: modelling health benefits in a context of study heterogeneity

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    This is the final version. Available on open access from Elsevier via the DOI in this record Although the beneficial health effects of green areas are gaining recognition, epidemiological studies show mixed results with significance varying considerably by study and context, indicating that there is no unique and clear evidence. This relationship is influenced by multiple factors and characterised by high complexity not previously been incorporated in one single analysis. This study proposes a new application of the Heckman selection model to find evidence of key patterns emerging throughout the literature and identify main determinants affecting the relationship. The model aggregates outcomes of different studies and allows an assessment of both significant and non-significant results from the literature in order to correct for unobserved selection bias. Close attention is paid to the relevance of the background, particularly socioeconomic context. The results show significant health benefits associated with increased exposure to green areas, where higher risk reductions are observed for old and adult age groups, as well as in poorer countries, taking into account the correction for the publication bias. This last issue points towards a redistributive impact of green areas in terms of health and the importance of co-benefits arising from Ecosystem-based Adaptation, especially in poorer neighbourhoods, translating in health care savings and reduced productivity loss.European Commissio

    Rare Species Are Valued Big Time

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    Background: It has recently been postulated that the value humans place on rarity could cause the extinction of rare species. This is because people are willing to pay the high costs of exploiting the last individuals. Many hobbies, such as ecotourism or the keeping of exotic pets may cause this effect – known as the anthropogenic Allee effect. However, the entire theory relies on the insofar undemonstrated assumption that people do value rarity. Methodology/Principal Findings: In order to quantify how much people valued rare species relative to common ones, we created online slideshows of photographs of either rare or common species on an Internet web site. The slideshow with photographs of rare species attracted more visitors, and visitors spent, in general, more time waiting to view it. Conclusions/Significance: We provide evidence that people value rare more than common species. As we did not target consumers of a specific market, this finding suggests that the anthropogenic Allee effect is likely be driven by a large part of the population. Given the substantial participation in our online experiment, we highlight the potential of the world wide web resource as a tool for conservation action. However, the evidence presented here that the general public value rare species, combined with the assumption that anthropogenic Allee effect is operating, implies that conservationists should be prudent when using rarity to promote conservation.Peer reviewe

    Urban green space: creating a triple win for environmental sustainability, health, and health equity through behavior change

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    Urbanization, costs of green space maintenance, and diminishing connection between people and nature all exert pressures on urban green space. This is regrettable as green space has the potential to create wins for environmental sustainability, health, and health equity. This paper explores this potential triple win and investigates how to increase the use of urban green space through behavior change. A narrative literature review was conducted and was supplemented with literature suggested by experts. Results show that creating well-designed green spaces and stimulating people to use them can indeed deliver this triple win. Providing accessible, attractive, well-maintained green space with room for socialization, and where people feel safe, may increase the opportunity and motivation of people to use it more often. Informing and educating people and organizing activities may increase capability (and motivation) to use green space. Since the use of green space depends on life stage, lifestyle factors and individual values, it is important to involve potential users in its design. We recommend a specific focus on those groups who may benefit most from the use of green space. More evaluation is needed to inform effective green space interventions and to assess related economic, social, and environmental benefits.info:eu-repo/semantics/publishedVersio
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