Short-range Sources Research Articles

The impact of urban mobility on air pollution in Kampala, an exemplar sub-Saharan African city

This paper analyses the impact of urban mobility (UM) on air pollution by studying the effects of an intervention on local air quality. The study focuses on the PM2.5 levels in Kampala, the capital of Uganda, and considers COVID-19 as an unintentional intervention. The PM2.5 level of the city was obtained from a network of low-cost calibrated sensors, while UM is characterized by open-access Google reports. The period under consideration excludes the weeks immediately before and after the first lockdown. PM2.5 data were deweathered using the machine learning technique of random forest (RF) to exclude the variation of meteorological factors, seasonality, and weekday-weekend effect, and then the impact of the pandemic was parametrised. The traffic pattern is discussed, and air mass clustering and pollution polar plots are used to analyse the distribution of long- and short-range sources, respectively. The percentage change from the baseline (PCfB) of the average of UM dimensions is then assessed against that of deweathered PM2.5 level to investigate the impact of UM on the PM2.5 level. Our analysis shows a strong correlation between urban mobility and roadside PM2.5 levels and a weaker relationship with urban PM2.5 levels. The profile of long-range emission sources was consistent over the study period, with more than 61% of the modelled air masses that arrived in Kampala first passing over Kenya and Tanzania. Overall, the COVID-19 pandemic reduced PM2.5 levels in Kampala by about 10%, which is relatively small compared to many other cities that have been studied around the world.

Trans-dimensional range-dependent geoacoustic inversion using modal dispersion data in the South China Sea

This paper presents geoacoustic inversion of modal dispersion data in the South China Sea using a single hydrophone and multiple impulsive sources at ranges from 5–100 km along a shallow-water track with slowly varying bathymetry. As a first step, the source waveform and bubble pulse are deconvolved from the recorded time series using a short-range source recording, corrected for the surface reflection. A time-frequency warping analysis is used to filter individual modes and obtain dispersion (arrival time as a function of frequency) data for three modes. Trans-dimensional Bayesian inversion is applied to the modal dispersion data, based on probabilistic sampling over an unknown number of seabed layers. Range-dependent inversion is considered, based on separating the environment into a sequence of range-independent sections, with frequency-dependent modal propagation times summed over segments. The inversion results are compared to core samples collected at sites along the survey line and to an independent headwave arrival-time analysis of the impulsive-source data.

Factors Affecting Short-Range Host-Seeking for the Yellow Fever Mosquito (Diptera: Culicidae).

Understanding short-range cues (e.g., host odorants, heat, moisture) of host-seeking female Aedes aegypti L. is very important for attempts to reduce mosquito bites, to complement current control strategies, and to develop potential spatial repellents. We investigated behavior under semi-field conditions utilizing a new portable uni-port taxis box with a caged chicken host. The combined influences of airflow regimes (0, 1.5, 3, 5, and 6 m/s), distance from host odor (10, 50, 100 cm), host-odor confinement (partial confinement/unconfined), and foraging periodicity (day/evening) were studied. Statistical regression analysis was used to delineate the significant factors that predict upwind flight behavior and short-range source location. Almost 15% of host-seeking Ae. aegypti were activated by an unconfined chicken odor in still air. This was double the number of attracted mosquitoes to confined host odor. The maximum behavioral response was reported with airflow of 5 m/s during daytime (76.7% ± 2.85) at a distance of 10 (70.7% ± 2.47) and 50 cm (56.7% ± 8.88). However, airflow of 6 m/s activated host-seeking orientation during evening assays. The host-seeking response between indoor and outdoor experiments was not significantly different and demonstrated the reliability of the portable taxis box in evaluating mosquito short-range behavioral response toward hosts.

Flux Noise in a Superconducting Transmission Line

We study a superconducting transmission line (TL) formed by distributed LC oscillators and excited by external magnetic fluxes which are aroused from random magnetization (A) placed in substrate or (B) distributed at interfaces of a two-wire TL. Low-frequency dynamics of a random magnetic field is described based on the diffusion Langevin equation with a short-range source caused by (a) random amplitude or (b) gradient of magnetization. For a TL modeled as a two-port network with open and shorted ends, the effective magnetic flux at the open end has non-local dependency on noise distribution along the TL. The flux-flux correlation function is evaluated and analyzed for the regimes (Aa), (Ab). (Ba), and (Bb). Essential frequency dispersion takes place around the inverse diffusion time of random flux along the TL. Typically, noise effect increases with size faster than the area of TL. The flux-flux correlator can be verified both via the population relaxation rate of the qubit, which is formed by the Josephson junction shunted by the TL with flux noises, and via random voltage at the open end of the TL.

Comparison of the sector and conventional spherical harmonic analyses of the solar magnetic field on the photosphere, source surface, and in the Earth’s orbit on July 10–20, 2004

The results of a spherical harmonic analysis and a sector spherical harmonic analysis of the solar magnetic field on the photosphere, source surface, and in the Earth’s orbit on July 10–20, 2004, were compared. It was found that the field values according to a sector harmonic analysis are an order of magnitude as large as the same values according to a spherical harmonic analysis and differ in the configuration. A twocomponent magnetic field structure was revealed: short-range sources are better described by a sector spherical harmonic analysis; long-range sources are better described by a spherical harmonic analysis. This is caused by the different depths of the occurrence of sources below the photosphere.

Intraoperative 32P High-Dose Rate Brachytherapy of the Dura for Recurrent Primary and Metastatic Intracranial and Spinal Tumors

Treatment of spinal and intracranial tumors with dural involvement is complicated by radiation tolerance of sensitive structures, especially in the setting of previous treatment. To evaluate whether intraoperative brachytherapy with short-range sources allows therapeutic dose delivery without damaging sensitive structures. The median doses of previous treatment were 3000 cGy (range, 1800-7200 cGy) for 8 patients with primary/recurrent and 17 patients with metastatic spinal tumors and 5040 cGy (range, 1300-6040 cGy) for 5 patients with locally recurrent and 2 patients with metastatic intracranial tumors. Patients underwent gross total or maximal resection of the tumor and were then treated with an intraoperative brachytherapy plaque consisting of a flexible silicone film incorporating P. A dose of 1000 cGy was delivered to a depth of 1 mm; the percent depth dose was less than 1% at 4 mm from the prescription depth. Median postoperative radiation doses of 2700 cGy (range, 1800-3000 cGy) were delivered to 15 spinal tumor patients and 3000 cGy (range, 1800-3000 cGy) to 3 intracranial tumor patients. The median follow-up was 4.4 months (range, 2.6-23.3 months) for spinal tumor patients and 5.3 months (range, 0.7-16.2) for intracranial tumor patients. At 6-month follow-up, for all spinal tumor patients, local progression-free survival and overall survival rates were both 83.3% (95% confidence interval [CI]: 62.3%-94.3%); for all intracranial tumor patients, the local progression-free survival rate was 62.5% (95% CI: 23.8%-90.9%) and the overall survival rate was 66.7% (95% CI: 26.7%-92.9%). There were no intraoperative or postoperative complications secondary to radiotherapy. Use of the P brachytherapy plaque is technically simple and not associated with increased risk of complications, even after multiple radiation courses. Local control rates were more than 80% in patients with proven radiation-resistant spinal disease.

Intraoperative 32P High Dose Rate Brachytherapy Plaque for Primary, Recurrent, and Metastatic Intracranial and Paraspinal Tumors

Treatment of paraspinal and intracranial tumors is complicated by the tolerance of sensitive structures to radiation, especially in the setting of prior treatment; the dural surface is often a critical site at risk for recurrence. Intraoperative brachytherapy using a short range source may allow delivery of therapeutic dose without damage to sensitive structures.

PCDD/Fs in sediments of Central Vietnam coastal lagoons: In search of TCDD

Samples from nine Central Vietnam coastal lagoons, together with three soils and sediments collected in two freshwater reservoirs of the Thua Thien-Hué province, were analysed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Total concentrations are low, from 192 to 2912pgg−1 and depth profiles in Tam Giang-Cau Hai (TG-CH) sediment cores show only minor changes over time in PCDD/F input and composition. Octachloro dibenzo-p-dioxin (OCDD) is the prevailing congener (approximately 90%), indicating combustion as the main PCDD/F source to these coastal systems, whereas natural formation might be partly responsible for the presence at depth. 2,3,7,8-Tetrachloro dibenzo-p-dioxin (TCDD), largely sprayed together with Agent Orange over the study areas during the war (1961–1971), is absent or very low. This result supports the hypothesis of strong degradation soon after spraying. Multivariate statistical analyses account for the presence of local, short-range sources as observed in the northern part of the TG-CH lagoon.

Spark cross size in a sliding submicrosecond discharge of opposite polarities in rare gases: experiment and application of ionization wave front propagation theory to analysis

The results from an experimental measurement of the spark channel radius in a sliding multichannel discharge of opposite polarities in Ne, Ar and Xe are presented and discussed. The experiments were performed at submicrosecond discharge pulse duration (90–190 ns current pulse FWHM) and gas pressures of 30 and 100 kPa, with alumina ceramics as the dielectric substrate. The data showed the optical radius of the negative polarity spark channels to exceed 1.27–1.6 times those of the positive channels, depending on the gas type and its pressure. The earlier theoretical study by U Ebert, W van Saarloos and C Caroly on the propagation of opposite polarity ionization wave fronts was applied to the analysis of experimental results. From the two approaches of theory, only the ‘non-localized initial conditions’ one, which in addition to the gas impact ionization, drift and diffusion of electrons also takes into account the free initial electrons in the gas ahead of the ionization wave front, is capable of explaining concurrently the experimental observations on positive and negative channel radii, their ratios and the dependence on gas type and pressure. Numerical solutions of the channel expansion equation specified that the expansion speed is governed by both the drift electrons and free electrons generated by a short-range source in a narrow layer around the channel lateral surface. The depth of the latter layer was estimated to be comparable to the expansion wave front depth and, thus, much less than the channel radius.

Seabed acoustics of a sand ridge on the New Jersey continental shelf

Acoustic measurements were made on a sand ridge on the New Jersey continental shelf. Data collected on two L arrays separated by 20 km from a single multi-frequency tow suggest small horizontal environmental variability. Values for the sound speed structure of the seabed are extracted by first applying a geo-acoustic inversion method to broadband and narrowband acoustic data from short-range sources. Then, a parabolic equation algorithm is used to properly include the bathymetry and sub-bottom layering. Finally, the frequency dependence of the seabed attenuation is inferred by optimizing the model fit to long-range transmission loss data in the 50-3000 Hz band.

Geoacoustic inversion of short range source data using a plane wave reflection coefficient approach

Acoustic time series data were collected in a shallow, hard bottom lake environment located in central Texas using both short range (2 m) implosive data, obtained with the source and a single hydrophone located near mid-depth in the waveguide, along with longer range implosive and explosive data from a near surface source to a bottom mounted hydrophone. Matched field inversions using simulated annealing were performed with a ray trace plus complex plane wave reflection coefficient forward propagation model that was validated in previous work. Isolating bottom interacting paths to perform the inversions is shown to be essential to reduce parameter uncertainties in the hard bottom environment and enables a systematic approach to the inversions which establishes the number of layers needed to represent the lake environment. Measured transmission loss data from a towed source were compared through a RMS error analysis to modeled transmission loss, constructed with the parameters from inversions of data from several source types, to further establish the validity of the inversion approach for this environment. Geoacoustic parameters obtained by inversions of short range, low frequency impulsive data are used to predict transmission loss at longer ranges and higher frequencies. The range dependence of the global minimum is discussed.

Evidence for an Emission Source of Large Space-Time Extent in Au+Au Collisions at RHIC

The source imaging technique of Brown and Danielewicz has been used to extract two-pion emission source functions over a broad range of kT and centralities in Au+Au collisions at \(\sqrt s = 200\) GeV. The source functions reflect the combined contributions of a short-range Gaussian-like component and a long-range exponential-like component. A parametrization of the source function gives a RMS radius for the long-range source which is approximately three times that for the short-range source. The centrality dependence of the extracted source parameters for the short- and long-range sources indicate similar patterns.

Spatial accuracy of 3D reconstructed radioluminographs of serial tissue sections and resultant absorbed dose estimates

Many agents using tumour-associated characteristics are deposited heterogeneously within tumour tissue. Consequently, tumour heterogeneity should be addressed when obtaining information on tumour biology or relating absorbed radiation dose to biological effect. We present a technique that enables radioluminographs of serial tumour sections to be reconstructed using automated computerized techniques, resulting in a three-dimensional map of the dose-rate distribution of a radiolabelled antibody. The purpose of this study is to assess the reconstruction accuracy. Furthermore, we estimate the potential error resulting from registration misalignment, for a range of beta-emitting radionuclides. We compare the actual dose-rate distribution with that obtained from the same activity distribution but with manually defined translational and rotational shifts. As expected, the error produced with the short-range 14C is much larger than that for the longer range 90Y; similarly values for the medium range 131I are between the two. Thus, the impact of registration inaccuracies is greater for short-range sources.

Factors Influencing Atmospheric Concentrations of Polychlorinated Biphenyls in Birmingham, U.K.

Atmospheric concentrations of PCBs were measured in Birmingham, U.K., between 7/13/97 and 7/27/98. A significant positive relationship was detected between the cosine of the wind direction and In P for {Sigma}PCB and tri- and tetrachlorinated PCBs. This is consistent with input from northerly winds passing over Birmingham city center, 3 km from the site. Plots of the enthalpy of surface-air exchange ({Delta}H{sub SA}) versus laboratory-measured heats of vaporization ({Delta}H{sub v}) for all congeners revealed a highly significant positive linear relationship. According to Simcik et al. this indicates local sources to be the predominant influence. However, separate plots of {Delta}H{sub SA} versus {Delta}H{sub v} for (a) the tri- and tetrachlorinated PCBs and (b) the penta-, hexa-, and heptachlorinated congeners revealed a highly significant linear relationship for the latter group but {Delta}H{sub SA} to be essentially constant for the former. Strict interpretation of Simcik et al.'s hypothesis suggests long-range transport as the principal source of tri- and tetrachlorinated PCBs but not of the higher chlorinated congeners. This is not thought credible given the nearby influence of the city center on concentrations of the lower chlorinated congeners, and the authors suggest correlation between {Delta}H{sub SA} and {Delta}H{sub v} will only be observed when more » the principal source is both close to the sampling site and governed by equilibrium surface-air partitioning. They therefore believe that at their site, the principal source of tri- and tetrachlorinated PCBs is nonequilibrium short-range transport, while for penta-through heptachlorinated PCBs, equilibrium short-range transport is the predominant source. Indoor air ventilation is a short-range source governed by factors such as the building ventilation rate, rather than surface-air partitioning. They therefore hypothesize that it constitutes the principal source of tri- and tetrachlorinated PCBs at their site. « less