4,619 research outputs found
Monolith-based68Ga processing: A new strategy for purification to facilitate direct radiolabelling methods
The post-processing of68Ga generator eluate by means of a novel high capacity cation-exchange silica monolith column has been validated in this work. Quantitative release of a purified68Ga solution in high concentration can be achieved using weak acidic solutions which can be directly used for chelator or conjugate labelling in an injectable form with improved radiochemical characteristics. The system has the potential to be incorporated in a flow based microfluidic system for dose-on-demand radiotracer synthesis
Optimization viewpoint on Kalman smoothing, with applications to robust and sparse estimation
In this paper, we present the optimization formulation of the Kalman
filtering and smoothing problems, and use this perspective to develop a variety
of extensions and applications. We first formulate classic Kalman smoothing as
a least squares problem, highlight special structure, and show that the classic
filtering and smoothing algorithms are equivalent to a particular algorithm for
solving this problem. Once this equivalence is established, we present
extensions of Kalman smoothing to systems with nonlinear process and
measurement models, systems with linear and nonlinear inequality constraints,
systems with outliers in the measurements or sudden changes in the state, and
systems where the sparsity of the state sequence must be accounted for. All
extensions preserve the computational efficiency of the classic algorithms, and
most of the extensions are illustrated with numerical examples, which are part
of an open source Kalman smoothing Matlab/Octave package.Comment: 46 pages, 11 figure
Muscle Glycogen Utilisation during an Australian Rules Football Game.
PURPOSE: To better understand the carbohydrate (CHO) requirement of Australian Football (AF) match play by quantifying muscle glycogen utilisation during an in-season AF match. METHODS: After a 24 h CHO loading protocol of 8 g/kg and 2 g/kg in the pre-match meal, two elite male forward players had biopsies sampled from m. vastus lateralis before and after participation in a South Australian Football League game. Player A (87.2kg) consumed water only during match play whereas player B (87.6kg) consumed 88 g CHO via CHO gels. External load was quantified using global positioning system technology. RESULTS: Player A completed more minutes on the ground (115 vs. 98 min) and covered greater total distance (12.2 vs. 11.2 km) than Player B, though with similar high-speed running (837 vs. 1070 m) and sprinting (135 vs. 138 m), respectively. Muscle glycogen decreased by 66% in Player A (Pre-: 656, Post-: 223 mmol∙kg-1 dw) and 24% in Player B (Pre-: 544, Post-: 416 mmol∙kg-1 dw), respectively. CONCLUSION: Pre-match CHO loading elevated muscle glycogen concentrations (i.e. >500 mmol.kg-1 dw), the magnitude of which appears sufficient to meet the metabolic demands of elite AF match play. The glycogen cost of AF match play may be greater than soccer and rugby and CHO feeding may also spare muscle glycogen use. Further studies using larger sample sizes are now required to quantify the inter-individual variability of glycogen cost of match play (including muscle and fibre-type specific responses) as well examine potential metabolic and ergogenic effects of CHO feeding
A Universal Model of Global Civil Unrest
Civil unrest is a powerful form of collective human dynamics, which has led
to major transitions of societies in modern history. The study of collective
human dynamics, including collective aggression, has been the focus of much
discussion in the context of modeling and identification of universal patterns
of behavior. In contrast, the possibility that civil unrest activities, across
countries and over long time periods, are governed by universal mechanisms has
not been explored. Here, we analyze records of civil unrest of 170 countries
during the period 1919-2008. We demonstrate that the distributions of the
number of unrest events per year are robustly reproduced by a nonlinear,
spatially extended dynamical model, which reflects the spread of civil disorder
between geographic regions connected through social and communication networks.
The results also expose the similarity between global social instability and
the dynamics of natural hazards and epidemics.Comment: 8 pages, 3 figure
Securing Cloud File Systems using Shielded Execution
Cloud file systems offer organizations a scalable and reliable file storage
solution. However, cloud file systems have become prime targets for
adversaries, and traditional designs are not equipped to protect organizations
against the myriad of attacks that may be initiated by a malicious cloud
provider, co-tenant, or end-client. Recently proposed designs leveraging
cryptographic techniques and trusted execution environments (TEEs) still force
organizations to make undesirable trade-offs, consequently leading to either
security, functional, or performance limitations. In this paper, we introduce
TFS, a cloud file system that leverages the security capabilities provided by
TEEs to bootstrap new security protocols that meet real-world security,
functional, and performance requirements. Through extensive security and
performance analyses, we show that TFS can ensure stronger security guarantees
while still providing practical utility and performance w.r.t. state-of-the-art
systems; compared to the widely-used NFS, TFS achieves up to 2.1X speedups
across micro-benchmarks and incurs <1X overhead for most macro-benchmark
workloads. TFS demonstrates that organizations need not sacrifice file system
security to embrace the functional and performance advantages of outsourcing
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