40 research outputs found

    Healthy aims: developing new medical implants and diagnostic equipment

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    Healthy Aims is a €23-million, four-year project, funded under the EU’s Information Society Technology Sixth Framework program to develop intelligent medical implants and diagnostic systems (www.healthyaims.org). The project has 25 partners from 10 countries, including commercial, clinical, and research groups. This consortium represents a combination of disciplines to design and fabricate new medical devices and components as well as to test them in laboratories and subsequent clinical trials. The project focuses on medical implants for nerve stimulation and diagnostic equipment based on straingauge technology

    Optimized dose regimen for whole-body FDG-PET imaging

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    BACKGROUND: The European Association of Nuclear Medicine procedure guidelines for whole-body fluorodeoxyglucose positron-emission tomography (FDG-PET) scanning prescribe a dose proportional to the patient’s body mass. However, clinical practice shows degraded image quality in obese patients indicating that using an FDG dose proportional to body mass does not overcome size-related degradation of the image quality. The aim of this study was to optimize the administered FDG dose as a function of the patient’s body mass or a different patient-dependent parameter, providing whole-body FDG-PET images of a more constant quality. METHODS: Using a linear relation between administered dose and body mass, FDG-PET imaging was performed on two PET/computed tomography scanners (Biograph TruePoint and Biograph mCT, Siemens). Image quality was assessed by the signal-to-noise ratio (SNR) in the liver in 102 patients with a body mass of 46 to 130 kg. Moreover, the best correlating patient-dependent parameter was derived, and an optimized FDG dose regimen was determined. This optimized dose regimen was validated on the Biograph TruePoint system in 42 new patients. Furthermore, this relation was verified by a simulation study, in which patients with different body masses were simulated with cylindrical phantoms. RESULTS: As expected, both PET systems showed a significant decrease in SNR with increasing patient’s body mass when using a linear dosage. When image quality was fitted to the patient-dependent parameters, the fit with the patient’s body mass had the highest R(2). The optimized dose regimen was found to be A(new)= c/t × m(2), where m is the body mass, t is the acquisition time per bed position and c is a constant (depending on scanner type). Using this relation, SNR no longer varied with the patient’s body mass. This quadratic relation between dose and body mass was confirmed by the simulation study. CONCLUSION: A quadratic relation between FDG dose and the patient’s body mass is recommended. Both simulations and clinical observations confirm that image quality remains constant across patients when this quadratic dose regimen is used

    Quantifying the Ocean, Freshwater and Human Effects on Year-to-Year Variability of One-Sea-Winter Atlantic Salmon Angled in Multiple Norwegian Rivers

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    Many Atlantic salmon, Salmo salar, populations are decreasing throughout the species' distributional range probably due to several factors acting in concert. A number of studies have documented the influence of freshwater and ocean conditions, climate variability and human impacts resulting from impoundment and aquaculture. However, most previous research has focused on analyzing single or only a few populations, and quantified isolated effects rather than handling multiple factors in conjunction. By using a multi-river mixed-effects model we estimated the effects of oceanic and river conditions, as well as human impacts, on year-to-year and between-river variability across 60 time series of recreational catch of one-sea-winter salmon (grilse) from Norwegian rivers over 29 years (1979–2007). Warm coastal temperatures at the time of smolt entrance into the sea and increased water discharge during upstream migration of mature fish were associated with higher rod catches of grilse. When hydropower stations were present in the course of the river systems the strength of the relationship with runoff was reduced. Catches of grilse in the river increased significantly following the reduction of the harvesting of this life-stage at sea. However, an average decreasing temporal trend was still detected and appeared to be stronger in the presence of salmon farms on the migration route of smolts in coastal/fjord areas. These results suggest that both ocean and freshwater conditions in conjunction with various human impacts contribute to shape interannual fluctuations and between-river variability of wild Atlantic salmon in Norwegian rivers. Current global change altering coastal temperature and water flow patterns might have implications for future grilse catches, moreover, positioning of aquaculture facilities as well as the implementation of hydropower schemes or other encroachments should be made with care when implementing management actions and searching for solutions to conserve this species

    Ecosystem consequences of wolf behavioral response to climate

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    Because apex predators exert considerable influence on the structure and function of top-down ecosystems, their responses to climate may shape responses at lower trophic levels. Previous reports of trophic cascades and ecosystem dynamics induced by predators have focused on changes in their abundance, whereas we investigated whether changes in predator behavior could precipitate cascades of similar ecological scale. Here we report the ecological consequences of predator behavioral response to global climatic variation using 40 years of data on wolf predation from Isle Royale, USA, where wolves limit abundance of moose, which limit productivity of fir trees. In response to increases in winter snow related to the North Atlantic Oscillation, wolves hunted in larger packs and, consequently, tripled the number of moose killed per day compared with less snowy years when they hunted in smaller packs. Following increased predation rates, moose abundance declined, and, following release from heavy browsing, growth of understory fir increased. Hence, cascading behavioral responses of apex predators may be a substantial link in the pathway from climatic change to ecosystem function

    Parallel Simulation Engines for Whole-Cell Models

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    The enormous complexity of whole-cell models needs new algorithmic approaches and high performant simulators. Our goal is the integration of deterministic and stochastic simulation algorithms in a highly scalable parallel simulator. Our hardware platform is a cluster of workstations as they are available in most research institutions. Therefore our parallel simulation engines are based on the Message Passing Interface (MPI) [1] standard, which has been implemented for many hard- and software environments. MPI is available as a library and represents a reliable platform for our work. We have implemented two parallel simulation engines, the Parallel Deterministic Simulation Engine (PDSE) and the Parallel Stochastic Simulation Engine (PSSE). Both use MPI for interprocess communication and share the same interface. Sharing a single library for parallel processing (MPI) reduces the amount of external software our simulator depends on and the system becomes easier to install and maintain. The PDSE is written in C++ and based on the Portable Extensible Toolkit for Scientific Computing (PETSc) [2], which is a software library providing routines and data structures for the numerical solution of partial differential equations and related problems on parallel (and serial) computers. PETSc uses MPI (as described above) for interprocess communication. The PDSE performs simulations on a distributed (regular) grid, that can be either 2- or 3-dimensional. The size of the grid may be customized according to the reaction volume to be simulated. Using the forward or the backward Euler method, PETSc solves the ordinary differential equations arising from the discretization of time-dependent partial differential equations that describe the biochemical model under investigation. Concerning the solution of ordinary differential equations we can rely on the stable numerical methods provided by the PETSc library. However, we are also able to use our own routines, since PETSc offers an interface to external ODE solvers as well. The PSSE is also written in C++ and uses an efficient implementation of the Next Reaction Method introduced by Gibson [3]. The reaction volume is subdivided into a cubic grid and each sub

    Ecological effects of the North Atlantic Oscillation

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