131,880 research outputs found
Generalized Additive Modelling of Mixed Distribution Markov Models with Application to Melbourne's Rainfall.
No full textWe consider modelling time series using a generalized additive model with first- order Markov structure and mixed transition density having a discrete component at zero and a continuous component with positive sample space. Such models have application, for example, in modelling daily occurrence and intensity of rainfall, and in modelling the number and size of insurance claims. We show how these methods extend the usual sinusoidal seasonal assumption in standard chain- dependent models by assuming a general smooth pattern of occurrence and intensity over time. These models can be fitted using standard statistical software. The methods of Grunwald and Jones (1998) can be used to combine these separate occurrence and intensity models into a single model for amount. We use 36 years of rainfall data from Melbourne, Australia, as a vehicle of illustration, and use the models to investigate the effect of the El Nino phenomenon on Melbourne's rainfall.Time Series ; Econometric Models ; Mixed Distribution Markov Models
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
The highly conserved nuclear lamin Ig-fold binds to PCNA : its role in DNA replication
No full textThis study provides insights into the role of nuclear lamins in DNA replication. Our data demonstrate that the Ig-fold motif located in the lamin C terminus binds directly to proliferating cell nuclear antigen ( PCNA), the processivity factor necessary for the chain elongation phase of DNA replication. We find that the introduction of a mutation in the Ig-fold, which alters its structure and causes human muscular dystrophy, inhibits PCNA binding. Studies of nuclear assembly and DNA replication show that lamins, PCNA, and chromatin are closely associated in situ. Exposure of replicating nuclei to an excess of the lamin domain containing the Ig-fold inhibits DNA replication in a concentration-dependent fashion. This inhibitory effect is significantly diminished in nuclei exposed to the same domain bearing the Ig-fold mutation. Using the crystal structures of the lamin Ig-fold and PCNA, molecular docking simulations suggest probable interaction sites. These findings also provide insights into the mechanisms underlying the numerous disease-causing mutations located within the lamin Ig-fold
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Effect of inflow conditions on tip vortex breakdown in a high Reynolds number wind turbine wake
No full textUnderstanding the re-energization of wind turbine wakes is crucial for the design and control of wind farms. Close to the rotor, this process is determined by the dynamics of the tip vortices. Here, we experimentally investigate the downstream evolution of the tip vortices for different inflow conditions. The experiments were performed in the Variable Density Turbulence Tunnel at the Max Planck Institute for Dynamics and Self-Organization, which uses pressurized SF 6 as the working fluid to achieve a turbine diameter-based Reynolds number of Re D = 2.9 × 10 6 . An active turbulence grid was used to generate atmospheric inflow conditions with varying levels of mean shear and turbulence intensity. Hot wire measurements of the streamwise velocity component were conducted in the inflow and the wake of a model wind turbine MoWiTO 0.6 for various tip speed ratios and are used to investigate the scaling of tip vortex breakdown in the near wake. Three different scaling regimes can be identified, which we link to an initial advection phase, the vortex breakdown, and a decaying turbulence regime. While the scaling in the vortex breakdown regime is only weakly affected by variations in mean velocity shear and turbulence intensity, higher tip speed ratios lead to faster breakdown
Peripheral arterial tone as an on-line measure of load in a simulated flight task
No full textVariations in continuous and discrete flight demands were investigated in a simulated flight mission measuring peripheral arterial tone (PAT) from the tip of the finger. A total of 12 participants performed a computer-simulated agricultural flight task. They were required to fly over a specific lane of asimulated corn field (continuous task) and change lanes in response to flags, which appeared at varying intervals (discrete task). The difficulty of the flight task was manipulated by varying the airplane control (single- vs. dual-axis control), while the difficulty of the discrete task was manipulated by varyingthe amount of lateral change signalled by the flag. PAT amplitude was lower in the difficult level of the continuous task and was further attenuated following the appearance of the flag only when a change in the flight position was required. These results suggest the potential utility of PAT as an on-line measure of the joint continuous and discrete demands of a flight mission
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Peripheral arterial tone as an on-line measure of flight load.
No full textWe investigated variations in continuous and discrete flight demands in a simulated flight mission employing a novel physiological measure of invested effort, Peripheral Arterial Tone (PAT). Twelve male subjects performed a computer-simulated agricultural flight task. They were required to fly over a specific lane of a field (continuous task) and change lanes in response to flags, which were presented at varying intervals (discrete task). The difficulty of the flight task was manipulated by changing the plane control (single- vs. dual-axis control), while the difficulty associated with the discrete events was manipulated byvarying the amount of lateral change signalled by the flag (no change vs. 1.5 or 3 lanes of change). PAT amplitude values were lower in the difficult level of the continuous task and was further attenuated following the appearance of the flag whena change in the flight position was required
The determinant of FDI in Central, Eastern and South-Eastern Europe: lesson from the past and prospects for the future
No full textThis chapter provides a critical review of the literature on the determinants of FDI in European transition countries, focusing on the external factors that are likely to affect the location and the magnitude of foreign investments. The contribution of the chapter is to evaluate what we can say with relative confidence about FDI behaviour in transition countries, and what we cannot say because of the lack of evidence. To guide the analysis, the chapter starts with a summary of the major
trends in foreign investments in Central, Eastern and South-Eastern
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European countries since the fall of the Berlin Wall. A brief discussion of
the main theories on FDI determinants will precede the analysis of the
empirical literature on such determinants in Central, Eastern and South-
Eastern European countries. This critical review aims both at understanding general trends, and at highlighting the issues that still need extra analysis, such as similarities and differences across economic sectors and the geographical location of foreign firms within the considered countries. This analysis can serve both as a guide for a better comprehension of future patterns of FDI into the region, and as a starting point for future research areas
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