12,979 research outputs found
Comparison of six derivatizing agents for the determination of nine synthetic cathinones using gas chromatography-mass spectrometry
Six acylation reagents have been compared for their derivatisation potential towards nine synthetic cathinones by gas chromatography-mass spectrometry (GC-MS). The evaluated reagents were pentafluoropropionic anhydride (PFPA), trifluoroacetic anhydride (TFA), chlorodifluoroacetic anhydride (CLF2AA), heptafluorobutyric anhydride (HFBA), acetic anhydride (AA) and propionic anhydride (PA). The synthetic cathinones included flephedrone (4-fluoromethcathinone or 4-FMC), mephedrone (4-methylmethcathinone or 4-MMC), pentedrone (also known as α-methylamino-valerophenone), methedrone (4-methoxy-N-methcathinone, p-methoxymethcathinone), methylone (3,4-methylenedioxy-N-methylcathinone or bk-MDMA), butylone (β-keto-N-methylbenzodioxolylbutanamine or bk-MBDB), ethylone (3,4-methylenedioxy-N-ethylcathinone MDEC or bk-MDEA), pyrovalerone (4-methyl-β-keto-prolintane) and 3,4-methylenedioxypyrovalerone (MDPV). The derivatizing agents were optimised for incubation time and temperature with some important validation parameters studied to evaluate derivatisation reactions. The anhydrides studied proved to be suitable for synthetic cathinones – all of them showing RSD and accuracy below 20%. PFPA and HFBA followed by TFA are the best choice of derivatising agents based on validation parameters. Five internal standards were evaluated with good results. Three way ANOVA, interference, fragmentation patterns and high peak area values at a concentration of 0.50 μg ml−1 were evaluated and discussed. AA and PA derivatives give high relative abundance for most drugs examined. HFBA gives more ions and multi-fragmentation patterns
A holistic analysis method to assess the controllability of commercial buildings and their systems
This paper describes a novel design process for advanced MIMO (multiple inputs and multiple outputs) control system design and simulation for buildings. The paper describes the knowledge transfer from high technology disciplines such as aerospace flight control systems and the space industry to establish a three-step modelling and design process. In step 1, simplified, but holistic nonlinear and linearised dynamic models of the building and its systems is derived. This model is used to analyse the controllability of the building. In step 2, further synthesis of this model leads to the correct topology of the control system design. This is proved through the use of simulation using the simple building model. In step 3, the controller design is proved using a fully detailed building simulation such as ESP-r that acts as a type of virtual prototype of the building. The conclusions show that this design approach can help in the design of superior and more complex control systems especially for buildings designed with a Climate Adaptive Building (CAB) philosophy where many control inputs and outputs are used to control the building's temperature, concentration of CO2, humidity and lighting levels
Automatic vs Manual Provenance Abstractions: Mind the Gap
In recent years the need to simplify or to hide sensitive information in
provenance has given way to research on provenance abstraction. In the context
of scientific workflows, existing research provides techniques to semi
automatically create abstractions of a given workflow description, which is in
turn used as filters over the workflow's provenance traces. An alternative
approach that is commonly adopted by scientists is to build workflows with
abstractions embedded into the workflow's design, such as using sub-workflows.
This paper reports on the comparison of manual versus semi-automated approaches
in a context where result abstractions are used to filter report-worthy results
of computational scientific analyses. Specifically; we take a real-world
workflow containing user-created design abstractions and compare these with
abstractions created by ZOOM UserViews and Workflow Summaries systems. Our
comparison shows that semi-automatic and manual approaches largely overlap from
a process perspective, meanwhile, there is a dramatic mismatch in terms of data
artefacts retained in an abstracted account of derivation. We discuss reasons
and suggest future research directions.Comment: Preprint accepted to the 2016 workshop on the Theory and Applications
of Provenance, TAPP 201
Slepian Spatial-Spectral Concentration on the Ball
We formulate and solve the Slepian spatial-spectral concentration problem on
the three-dimensional ball. Both the standard Fourier-Bessel and also the
Fourier-Laguerre spectral domains are considered since the latter exhibits a
number of practical advantages (spectral decoupling and exact computation). The
Slepian spatial and spectral concentration problems are formulated as
eigenvalue problems, the eigenfunctions of which form an orthogonal family of
concentrated functions. Equivalence between the spatial and spectral problems
is shown. The spherical Shannon number on the ball is derived, which acts as
the analog of the space-bandwidth product in the Euclidean setting, giving an
estimate of the number of concentrated eigenfunctions and thus the dimension of
the space of functions that can be concentrated in both the spatial and
spectral domains simultaneously. Various symmetries of the spatial region are
considered that reduce considerably the computational burden of recovering
eigenfunctions, either by decoupling the problem into smaller subproblems or by
affording analytic calculations. The family of concentrated eigenfunctions
forms a Slepian basis that can be used be represent concentrated signals
efficiently. We illustrate our results with numerical examples and show that
the Slepian basis indeeds permits a sparse representation of concentrated
signals.Comment: 33 pages, 10 figure
Non-linear convergence in Asian interest rates and inflation rates
We examine the dynamics of convergence of the ASEAN5 plus the big three for nominal interest rates, inflation rates, and real interest rates. We test for convergence relative to the U.S and Japan, using monthly data over the period January 1990 - December 2010, using non-linear unit root tests. The results show strong evidence of stationary inflation and real interest rate differentials in all but China’s inflation differential relative to the U.S., and stationary nominal interest differentials in most of the cases. We interpret these results as convergence in inflation rates and real interest rates in all cases, and as nominal interest convergence in most of the cases. Moreover, examining the impact of the Asian crisis shows less number of convergences before the crisis and more convergences after the crisis. This suggests that convergence has increased after the 1997/98 Asian crisis, and that the crisis has pulled the economies together.interest rates convergence; inflation convergence; nonlinear unit root tests
An Optimal Dimensionality Sampling Scheme on the Sphere for Antipodal Signals In Diffusion Magnetic Resonance Imaging
We propose a sampling scheme on the sphere and develop a corresponding
spherical harmonic transform (SHT) for the accurate reconstruction of the
diffusion signal in diffusion magnetic resonance imaging (dMRI). By exploiting
the antipodal symmetry, we design a sampling scheme that requires the optimal
number of samples on the sphere, equal to the degrees of freedom required to
represent the antipodally symmetric band-limited diffusion signal in the
spectral (spherical harmonic) domain. Compared with existing sampling schemes
on the sphere that allow for the accurate reconstruction of the diffusion
signal, the proposed sampling scheme reduces the number of samples required by
a factor of two or more. We analyse the numerical accuracy of the proposed SHT
and show through experiments that the proposed sampling allows for the accurate
and rotationally invariant computation of the SHT to near machine precision
accuracy.Comment: Will be published in the proceedings of the International Conference
Acoustics, Speech and Signal Processing 2015 (ICASSP'2015
Multi-channel GaAs-based planar gunn diodes
We present a multi-channel GaAs-based planar Gunn
diode. By introducing extra channels, the output RF power has
been significantly improved compared to single-channel GaAsbased
planar Gunn diodes. For a 1.14 μm length and 60 μm wide
device, the highest power achieved was approximately -4 dBm
operating in fundamental mode at 109 GHz, and -26.6 dBm at its
second-harmonic at 218 GHz
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