1,248 research outputs found

    Potential of MODIS EVI and surface temperature for directly estimating per-pixel ecosystem C fluxes

    Get PDF
    We tested the potential of estimating per-pixel gross primary production (GPP) directly from the MODIS enhanced vegetation index (EVI) and respiration directly from MODIS surface temperature (MOD11). Carbon flux data were obtained from 10 eddy covariance tower sites representing a wide range of North American vegetations. The correlation between across-site tower GPP and EVI was comparable (r = 0.77) to that between tower GPP and MOD17-GPP (r = 0.73), suggesting that EVI could be used to provide reasonably accurate direct estimates of GPP on a truly per-pixel basis. There was also a strong relationship (r2 = 0.67) between respiration and surface temperature of dense vegetation, suggesting that estimation of net ecosystem exchange (NEE) may be possible with relatively simple pixel based models, at least for some vegetation types

    Gross Domestic Product (GDP) and productivity of schizophrenia trials: an ecological study

    Get PDF
    The 5000 randomised controlled trials (RCTs) in the Cochrane Schizophrenia Group's database affords an opportunity to research for variables related to the differences between nations of their output of schizophrenia trials. Ecological study – investigating the relationship between four economic/demographic variables and number of schizophrenia RCTs per country. The variable with closest correlation was used to predict the expected number of studies. GDP closely correlated with schizophrenia trial output, with 76% of the total variation about the Y explained by the regression line (r = 0.87, 95% CI 0.79 to 0.92, r2 = 0.76). Many countries have a strong tradition of schizophrenia trials, exceeding their predicted output. All nations with no identified trial output had GDPs that predicted zero trial activity. Several nations with relatively small GDPs are, nevertheless, highly productive of trials. Some wealthy countries seem either not to have produced the expected number of randomised trials or not to have disseminated them to the English-speaking world. This hypothesis-generating study could not investigate causal relationships, but suggests, that for those seeking all relevant studies, expending effort searching the scientific literature of Germany, Italy, France, Brazil and Japan may be a good investment

    Reducing the Vulnerability of Electric Power Infrastructure Against Natural Disasters by Promoting Distributed Generation

    Get PDF
    Natural disasters cause significant damage to the electrical power infrastructure every year. Therefore, there is a crucial need to reduce the vulnerability of the electric power grid against natural disasters. Distributed generation (DG) represents small-scale decentralized power generation that can help reduce the vulnerability of the grid, among many other benefits. Examples of DG include small-scale photo-voltaic (PV) systems. Accordingly, the goal of this paper is to investigate the benefits of DG in reducing the vulnerability of the electric power infrastructure by mitigating against the impact of natural disasters on transmission lines. This was achieved by developing a complex system-of-systems (SoS) framework using agent-based modeling (ABM) and optimal power flow (OPF). N-1 contingency analysis and optimization were performed under two approaches: The first approach determined the minimum DG needed at any single location on the electric grid to avoid blackouts. The second approach used a genetic algorithm (GA) to identify the minimum total allocation of DG distributed over the electric grid to mitigate against the failure of any transmission line. Accordingly, the model integrates ABM, OPF, and GA to optimize the allocation of DG and reduce the vulnerability of electric networks. The model was tested on a modified IEEE 6-bus system as a proof of concept. The outcomes of this research are intended to support the understanding of the benefits of DG in reducing the vulnerability of the electric power grid. The presented framework can guide future research concerning policies and incentives that can strategically influence consumer decision to install DG and reduce the vulnerability of the electric power infrastructure

    Is the US dollar a suitable anchor for the newly proposed GCC currency?

    Get PDF
    Responses of inflation and non-oil output growth from the Gulf Cooperation Council (GCC) countries to monetary policy shocks from the United States (US) were estimated to determine whether there is evidence to support the US Dollar as the anchor for the proposed unified currency. A structural vector autoregression identified with short-run restrictions was employed for each country with Fed funds rate as the US monetary policy instrument, non-oil output growth, and inflation. The main results suggest that for inflation, the GCC countries show synchronised responses to monetary policy shocks from the US which are similar to inflation in the US, and for non-oil output growth, there is no clear indication that US monetary policy can be as effective for the GCC countries as it is domestically. Consequently, importing US monetary policy via a Dollar peg may guarantee only stable inflation for the GCC countries - not necessarily stable non-oil output growth. If the non-oil output response is made conscientiously - and there are concerns over the Dollar's ability to perform its role as a store of value - a basket peg with both the US Dollar and the Euro may be a sound alternative as confirmed by the variance decomposition analysis of our augmented SVAR with a proxy for the European short-term interest rate

    Egyptian historical parks, authenticity vs. change in Cairo's cultural landscapes

    Get PDF
    As a historically intense country, Egypt's built environment has always been the focus of plentiful urban research. However, the natural component in the urban fabric of Egyptian cities has been undermined and understudied in between all the numerous ideas and data. In a historical city like Cairo, layers of history are illustrated in its parks and gardens. Left unearthed and neglected, these vital spaces are subject to negative change and decay under the pressure of land use demands, among various other challenges. Many of Cairo's parks and gardens date back to the 19th and 20th century, containing endless gestures from the cultural essence of this time era in their design. This paper discusses ten public parks and gardens in Cairo founded in the 19th and 20th centuries, and survive to our present day (whether completely or partially). Viewing the initial design and development of these parks in comparison with their current state is rather intriguing to investigate. These historical parks and gardens are worthy of identification for preservation. With resourceful and directed management, these spaces can dramatically change the view of Cairo as a suffocating dense urban tissue, to a more perforated and engaging urban experience for its community

    On the use of MODIS EVI to assess gross primary productivity of North American ecosystems

    Get PDF
    [1] Carbon flux models based on light use efficiency (LUE), such as the MOD17 algorithm, have proved difficult to parameterize because of uncertainties in the LUE term, which is usually estimated from meteorological variables available only at large spatial scales. In search of simpler models based entirely on remote‐sensing data, we examined direct relationships between the enhanced vegetation index (EVI) and gross primary productivity (GPP) measured at nine eddy covariance flux tower sites across North America. When data from the winter period of inactive photosynthesis were excluded, the overall relationship between EVI and tower GPP was better than that between MOD17 GPP and tower GPP. However, the EVI/GPP relationships vary between sites. Correlations between EVI and GPP were generally greater for deciduous than for evergreen sites. However, this correlation declined substantially only for sites with the smallest seasonal variation in EVI, suggesting that this relationship can be used for all but the most evergreen sites. Within sites dominated by either evergreen or deciduous species, seasonal variation in EVI was best explained by the severity of summer drought. Our results demonstrate that EVI alone can provide estimates of GPP that are as good as, if not better than, current versions of the MOD17 algorithm for many sites during the active period of photosynthesis. Preliminary data suggest that inclusion of other remote‐sensing products in addition to EVI, such as the MODIS land surface temperature (LST), may result in more robust models of carbon balance based entirely on remote‐sensing data

    Non-L\'evy mobility patterns of Mexican Me'Phaa peasants searching for fuelwood

    Full text link
    We measured mobility patterns that describe walking trajectories of individual Me'Phaa peasants searching and collecting fuelwood in the forests of "La Monta\~na de Guerrero" in Mexico. These one-day excursions typically follow a mixed pattern of nearly-constant steps when individuals displace from their homes towards potential collecting sites and a mixed pattern of steps of different lengths when actually searching for fallen wood in the forest. Displacements in the searching phase seem not to be compatible with L\'evy flights described by power-laws with optimal scaling exponents. These findings however can be interpreted in the light of deterministic searching on heavily degraded landscapes where the interaction of the individuals with their scarce environment produces alternative searching strategies than the expected L\'evy flights. These results have important implications for future management and restoration of degraded forests and the improvement of the ecological services they may provide to their inhabitants.Comment: 15 pages, 4 figures. First version submitted to Human Ecology. The final publication will be available at http://www.springerlink.co
    corecore