Spatially and temporally resolved measurements of NO_<i>x</i> fluxes by airborne eddy covariance over Greater London

Flux measurements of nitrogen oxides (NOx) were made over London using airborne eddy covariance from a low-flying aircraft. Seven low-altitude flights were conducted over Greater London, performing multiple overpasses across the city during eight days in July 2014. NOx fluxes across the Greater London region (GLR) exhibited high heterogeneity and strong diurnal variability, with central areas responsible for the highest emission rates (20–30 mg m−2 h−1). Other high-emission areas included the M25 orbital motorway. The complexity of London's emission characteristics makes it challenging to pinpoint single emissions sources definitively using airborne measurements. Multiple sources, including road transport and residential, commercial and industrial combustion sources, are all likely to contribute to measured fluxes. Measured flux estimates were compared to scaled National Atmospheric Emissions Inventory (NAEI) estimates, accounting for monthly, daily and hourly variability. Significant differences were found between the flux-driven emissions and the NAEI estimates across Greater London, with measured values up to 2 times higher in Central London than those predicted by the inventory. To overcome the limitations of using the national inventory to contextualise measured fluxes, we used physics-guided flux data fusion to train environmental response functions (ERFs) between measured flux and environmental drivers (meteorological and surface). The aim was to generate time-of-day emission surfaces using calculated ERF relationships for the entire GLR; 98 % spatial coverage was achieved across the GLR at 400 m2 spatial resolution. All flight leg projections showed substantial heterogeneity across the domain, with high emissions emanating from Central London and major road infrastructure. The diurnal emission structure of the GLR was also investigated, through ERF, with the morning rush hour distinguished from lower emissions during the early afternoon. Overall, the integration of airborne fluxes with an ERF-driven strategy enabled the first independent generation of surface NOx emissions, at high resolution using an eddy-covariance approach, for an entire city region.

Spatially and temporally resolved measurements of NO_x fluxes by airborne eddy-covariance over Greater London

Flux measurements of nitrogen oxides (NOx) were made over London using airborne eddy-covariance from a low flying aircraft. Seven low altitude flights were conducted over Greater London performing multiple over-passes across the city during eight days in July 2014. NOx fluxes across the Greater London region exhibited high heterogeneity and strong diurnal variability, with central areas responsible for the highest emission rates (20–30 mg m−2 h−1). Other high emission areas included the M25 orbital motorway. The complexity of London’s emission characteristics makes it challenging to pinpoint single emission sources definitively using airborne measurements. Multiple sources, including road transport and residential, commercial and industrial combustion sources are all likely to contribute to measured fluxes. Measured flux estimates were compared to scaled National Atmospheric Emissions Inventory (NAEI) estimates, accounting for; monthly, daily and hourly variability. Significant differences were found between the flux-driven emissions and the NAEI estimates across Greater London, with measured values up to two times higher in Central London than those predicted by the inventory. To overcome the limitations of using the national inventory to contextualise measured fluxes, we used physics-guided flux data fusion to train environmental response functions (ERF) between measured flux and environmental drivers (meteorological and surface). The aim was to generate time-of-day emission surfaces using calculated ERF relationships for the entire Greater London region (GLR). 98 % spatial coverage was achieved across GLR at 400 m2 spatial resolution. All flight leg projections showed substantial heterogeneity across the domain, with high emissions emanating from Central London and major road infrastructure. The diurnal emission structure of the GLR was also investigated, through ERF, with the morning rush-hour distinguished from lower emissions during the early afternoon. Overall, the integration of airborne fluxes with an ERF-driven strategy enabled the first independent generation of surface NOx emissions, at high resolution using an eddy-covariance approach, for an entire city region.

Free fatty acid flux measured using [1-11C]palmitate positron emission tomography and [U-13C]palmitate in humans

PET radiopharmaceuticals can noninvasively measure free fatty acid (FFA) tissue uptake. Investigators often use PET scan-derived data to calculate FFA flux. We tested whether the [1-11C]palmitate PET measures of palmitate flux provide results equivalent to a continuous infusion of [U-13C]palmitate. Nine volunteers participated in study 1 to evaluate whether a rapidly (10–20 s) given bolus of [1-11C]palmitate affects calculated flux results. Thirty volunteers participated in study 2, which was identical to study 1 except that the [1-11C]palmitate bolus was given over 1 min. Volunteers in both studies also received a continuous intravenous infusion of [U-13C]palmitate. Plasma palmitate concentrations and enrichment were measured by liquid chromatography-mass spectrometry. The PET/CT images were analyzed on a workstation running PMOD. Palmitate flux was estimated using PET time-activity curve (TAC) data from regions of interest in the left ventricle (LV) and aorta both with and without hybrid TACs that employed the 11CO2-corrected data for the first 5 min and the 11CO2-corrected blood radioactivity for the remainder of the PET scan. Palmitate flux in study 1 measured with PET [1-11C]palmitate and [U-13C]palmitate were not correlated, and the PET [1-11C]palmitate flux was significantly less than the [U-13C]palmitate measured flux. In study 2, the palmitate flux using PET [1-11C]palmitate hybrid LV models provided closer mean estimates of [U-13C]palmitate measured flux. The best PET calculation approaches predicted 64% of the interindividual variance in [U-13C]palmitate measured flux. Palmitate kinetics measured using [1-11C]palmitate/PET do not provide the same palmitate kinetic results as the continuous infusion [U-13C]palmitate approach.

Effects of baffle reflection and shadow in an integrating sphere on the total luminous flux measurement of a linearly-shaped lamp

<p class="Text">The measured total luminous flux of a linearly-shaped lamp by using the integrating sphere substitution method against a standard spherical lamp can be deviated from accurate by the presence of a baffle in the sphere. The baffle introduced two main effects on the sphere response: the baffle reflection, or high-signal region, and the baffle shadow, or low-signal region. Once the baffle condition changed, the two effects changed, causing the measured value to change differently regarding the lamp alignment. In the perpendicular alignment, increasing the baffle length increased the measured flux value. This was due to the dramatic increase in the magnitude of the signal in the baffle reflection behind the baffle. In a coaxial alignment, on the contrary, increasing the baffle length resulted in the decrease of the measured flux value. This was due to the increase in the area of the baffle shadow on the opposite hemisphere from the baffle, which increased at the higher ratio than the area of the baffle reflection. In both alignments, the measurement uncertainty increased with the baffle length due to the increasing magnitude of the signal fluctuations. The trends were similar for all linearly-shaped test lamps with different lengths and diameters.</p>

Low-Frequency Spectral Energy Distributions of Radio Pulsars Detected with the Murchison Widefield Array

We present low-frequency spectral energy distributions of 60 known radio pulsars observed with the Murchison Widefield Array telescope. We searched the GaLactic and Extragalactic All-sky Murchison Widefield Array survey images for 200-MHz continuum radio emission at the position of all pulsars in the Australia Telescope National Facility (ATNF) pulsar catalogue. For the 60 confirmed detections, we have measured flux densities in 20 × 8 MHz bands between 72 and 231 MHz. We compare our results to existing measurements and show that the Murchison Widefield Array flux densities are in good agreement.

Stochastic models for the evaluation of magnetisation faults

Purpose – The introduction of stochastic deviations due to production faults into the finite element (FE) simulation of electrical machines requires suitable error-model. These models should describe the occurring deviations from the ideal case. Permanent magnets, which can be used as rotor excitations in synchronous machines (PMSM), are one out of many possible sources for the aforementioned stochastic production variations. Fitting measured magnet variations to simulation models with the aim of describing the occurring production deviations, however, poses a problem due to two reasons: to begin with, only data of measured flux-densities are available. Second, a solution of the inverse problem is required to obtain data about changes inside the magnet. This paper, therefore, presents two solutions to this problem. Design/methodology/approach – Two error-models, one based on knowledge about the magnetisation process, the other one built upon principal component analysis, are presented. Both models are evaluated by parametrising them, using a set of measured flux-density data from magnets. Afterwards, each model's applicability and reproduction quality is assessed. Findings – Both models still have some drawbacks. While the first model seems to be too coarse grained for certain variations, the second model lacks applicability for a high reproduction quality. Originality/value – The comparison of both methods reveals guidelines, which methodology should be applied for predicting which variations. Furthermore, solutions are shown, how to mitigate the problems of the two presented models.

Radio polarization observations of large supernova remnants at λ6 cm

We have observed 79 supernova remnants (SNRs) with the Urumqi 25 m telescope at λ6 cm during the Sino-German λ6 cm polarization survey of the Galactic plane. We measured flux densities of SNRs at λ6 cm, some of which are the first ever measured or the measurements at the highest frequency, so that we can determine or improve spectra of SNRs. Our observations have ruled out spectral breaks or spectral flattening that were suggested for a few SNRs, and confirmed the spectral break of S147. By combining our λ6 cm maps with λ11 cm and λ21 cm maps from the Effelsberg 100 m telescope, we calculated the spectral index maps of several large SNRs. For many remnants we obtained for the first time polarization images, which show the intrinsic magnetic field structures at λ6 cm. We disapproved three objects as being SNRs, OA184, G192.8−1.1 and G16.8−1.1, which show a thermal spectrum and no polarization. We have discovered two large supernova remnants, G178.2−4.2 and G25.1−2.3., in the survey maps.