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Search Results: 1 - 10 of 374187 matches for " C. D. Anthony Herndon "
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Antenatal Hydronephrosis: Differential Diagnosis, Evaluation, and Treatment Options
C.D. Anthony Herndon
The Scientific World Journal , 2006, DOI: 10.1100/tsw.2006.366
Postnatal Imaging of Antenatal Hydronephrosis
David M. Kitchens,C. D. Anthony Herndon
The Scientific World Journal , 2009, DOI: 10.1100/tsw.2009.50
Prenatal Intervention for Lower Urinary Tract Obstruction
David M. Kitchens,C. D. Anthony Herndon
The Scientific World Journal , 2009, DOI: 10.1100/tsw.2009.49
The Management of Ureteropelvic Junction Obstruction Presenting with Prenatal Hydronephrosis
C.D. Anthony Herndon,David M. Kitchens
The Scientific World Journal , 2009, DOI: 10.1100/tsw.2009.51
Evaluation of nitrogen dioxide chemiluminescence monitors in a polluted urban environment
E. J. Dunlea,S. C. Herndon,D. D. Nelson,R. M. Volkamer
Atmospheric Chemistry and Physics Discussions , 2007,
Abstract: Data from a recent field campaign in Mexico City are used to evaluate the performance of the EPA Federal Reference Method for monitoring ambient concentrations of NO2. Measurements of NO2 from standard chemiluminescence monitors equipped with molybdenum oxide converters are compared with those from Tunable Infrared Laser Differential Absorption Spectroscopy (TILDAS) and Differential Optical Absorption Spectroscopy (DOAS) instruments. A significant interference in the chemiluminescence measurement is shown to account for up to 50% of ambient NO2 concentration during afternoon hours. As expected, this interference correlates well with non-NOx reactive nitrogen species (NOz as well as with ambient O3 concentrations, indicating a photochemical source for the interfering species. A combination of ambient gas phase nitric acid and alkyl and multifunctional alkyl nitrates is deduced to be the primary cause of the interference. Observations at four locations at varying proximities to emission sources indicate that the percentage contribution of HNO3 to the interference decreases with time as the air parcel ages. Alkyl and multifunctional alkyl nitrate concentrations are calculated to be reach concentrations as high as several ppb inside the city, on par with the highest values previously observed in other urban locations. Averaged over the MCMA-2003 field campaign, the CL NOx monitor interference resulted in an average measured NO2 concentration up to 22% greater than that from co-located spectroscopic measurements. Thus, this interference has the potential to initiate regulatory action in areas that are close to non-attainment and may mislead atmospheric photochemical models used to assess control strategies for photochemical oxidants.
Technical note: Evaluation of standard ultraviolet absorption ozone monitors in a polluted urban environment
E. J. Dunlea,S. C. Herndon,D. D. Nelson,R. M. Volkamer
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2006,
Abstract: The performance of the EPA Federal Equivalent Method (FEM) technique for monitoring ambient concentrations of O3 via ultraviolet absorption (UV) has been evaluated using data from the Mexico City Metropolitan Area field campaign (MCMA-2003). Comparisons of UV O3 monitors with open path Differential Optical Absorption Spectroscopy (DOAS) and open path Fourier Transform Infrared (FTIR) spectroscopy instruments in two locations revealed average discrepancies in the measured concentrations between +13% to 18%. Good agreement of two separate open path DOAS measurements at one location indicated that spatial and temporal inhomogeneities were not substantially influencing comparisons of the point sampling and open path instruments. The poor agreement between the UV O3 monitors and the open path instruments was attributed to incorrect calibration factors for the UV monitors, although interferences could not be completely ruled out. Applying a linear correction to these calibration factors results in excellent agreement of the UV O3 monitors with the co-located open path measurements; regression slopes of 0.94 to 1.04 and associated R2 values of >0.89. A third UV O3 monitor suffered from large spurious interferences, which were attributed to extinction of UV radiation within the monitor by fine particles (<0.2 μm). The overall performance of this particular monitor was poor owing to a combination of interferences from a contaminated particle filter and/or ozone scrubber. Suggestions for improved operation practices of these UV O3 monitors and recommendations for future testing are made.
Particulate polycyclic aromatic hydrocarbon spatial variability and aging in Mexico City
D. A. Thornhill,S. C. Herndon,T. B. Onasch,E. C. Wood
Atmospheric Chemistry and Physics Discussions , 2007,
Abstract: As part of the Megacities Initiative: Local and Global Research Observations (MILAGRO) study in the Mexico City Metropolitan Area in March 2006, we measured particulate polycyclic aromatic hydrocarbons (PAHs) and other gaseous species and particulate properties at six locations throughout the city. The measurements were intended to support the following objectives: to describe spatial and temporal patterns in PAH concentrations, to gain insight into sources and transformations of PAHs, and to quantify the relationships between PAHs and other pollutants. Total particulate PAHs at the Instituto Mexicano del Petróleo (T0 supersite) located near downtown averaged 50 ng m 3, and aerosol active surface area averaged 80 mm2 m 3. PAHs were also measured on board the Aerodyne Mobile Laboratory, which visited six sites encompassing a mixture of different land uses and a range of ages of air parcels transported from the city core. Weak intersite correlations suggest that local sources are important and variable and that exposure to PAHs cannot be represented by a single regional-scale value. The relationships between PAHs and other pollutants suggest that a variety of sources and ages of particles are present. Among carbon monoxide, nitrogen oxides (NOx), and carbon dioxide, particulate PAHs are most strongly correlated with NOx. Mexico City's PAH-to-black carbon mass ratio of 0.01 is similar to that found on a freeway loop in the Los Angeles area and approximately 8–30 times higher than that found in other cities. Ratios also indicate that primary combustion particles are rapidly coated by secondary aerosol in Mexico City. If so, the lifetime of PAHs may be prolonged if the coating protects them against photodegradation or heterogeneous reactions.
Integrating RFIDs and Smart Objects into a UnifiedInternet of Things Architecture  [PDF]
Evangelos A. Kosmatos, Nikolaos D. Tselikas, Anthony C. Boucouvalas
Advances in Internet of Things (AIT) , 2011, DOI: 10.4236/ait.2011.11002
Abstract: The term Internet of Things refers to the networked interconnection of objects of diverse nature, such as electronic devices, sensors, but also physical objects and beings as well as virtual data and environments. Although the basic concept of the Internet of Things sounds simple, its application is difficult and, so far, the respective existing architectural models are rather monolithic and are dominated by several limitations. The paper introduces a generic Internet of Things architecture trying to resolve the existing restrictions of current architectural models by integrating both RFID and smart object-based infrastructures, while also exploring a third parameter, i.e. the social potentialities of the Internet of Things building blocks towards shaping the “Social Internet of Things”. The proposed architecture is based on a layered lightweight and open middle-ware solution following the paradigm of Service Oriented Architecture and the Semantic Model Driven Ap-proach, which is realized at both design-time and deployment–time covering the whole service lifecycle for the corresponding services and applications provided.
A Combination of CDF and DO Limits on the Branching Ratio of B_s(d) to mu+ mu- Decays
R. Bernhard,D. Glenzinski,M. Herndon,T. Kamon,V. Krutelyov,G. Landsberg,F. Lehner,C. J. Lin,S. Mrenna
Physics , 2005,
Abstract: We combine the results of CDF and DO searches for the rare decays B_s to mu+ mu- and B_d to mu+ mu-. The experiments use 364 pb-1 and 300 pb-1 of data respectively. The limits on the branching ratios are obtained by normalizing the estimated sensitivity to the decay B+ to J/psi K+, taking into account the fragmentation ratios f_u/f_s(d). The combined results exclude branching ratios of BR(B_s to mu+ mu-) > 1.5x10-7 and BR(B_d to mu+ mu- > 4.0x10-8 at 95% confidence level. These are the most stringent limits on these decays at the present time.
Application of positive matrix factorization to on-road measurements for source apportionment of diesel- and gasoline-powered vehicle emissions in Mexico City
D. A. Thornhill, A. E. Williams, T. B. Onasch, E. Wood, S. C. Herndon, C. E. Kolb, W. B. Knighton, M. Zavala, L. T. Molina,L. C. Marr
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2010,
Abstract: The goal of this research is to quantify diesel- and gasoline-powered motor vehicle emissions within the Mexico City Metropolitan Area (MCMA) using on-road measurements captured by a mobile laboratory combined with positive matrix factorization (PMF) receptor modeling. During the MCMA-2006 ground-based component of the MILAGRO field campaign, the Aerodyne Mobile Laboratory (AML) measured many gaseous and particulate pollutants, including carbon dioxide, carbon monoxide (CO), nitrogen oxides (NOx), benzene, toluene, alkylated aromatics, formaldehyde, acetaldehyde, acetone, ammonia, particle number, fine particulate mass (PM2.5), and black carbon (BC). These serve as inputs to the receptor model, which is able to resolve three factors corresponding to gasoline engine exhaust, diesel engine exhaust, and the urban background. Using the source profiles, we calculate fuel-based emission factors for each type of exhaust. The MCMA's gasoline-powered vehicles are considerably dirtier, on average, than those in the US with respect to CO and aldehydes. Its diesel-powered vehicles have similar emission factors of NOx and higher emission factors of aldehydes, particle number, and BC. In the fleet sampled during AML driving, gasoline-powered vehicles are found to be responsible for 97% of total vehicular emissions of CO, 22% of NOx, 95–97% of each aromatic species, 72–85% of each carbonyl species, 74% of ammonia, negligible amounts of particle number, 26% of PM2.5, and 2% of BC; diesel-powered vehicles account for the balance. Because the mobile lab spent 17% of its time waiting at stoplights, the results may overemphasize idling conditions, possibly resulting in an underestimate of NOx and overestimate of CO emissions. On the other hand, estimates of the inventory that do not correctly account for emissions during idling are likely to produce bias in the opposite direction.The resulting fuel-based estimates of emissions are lower than in the official inventory for CO and NOx and higher for VOCs. For NOx, the fuel-based estimates are lower for gasoline-powered vehicles but higher for diesel-powered ones compared to the official inventory. While conclusions regarding the inventory should be interpreted with care because of the small sample size, 3.5 h of driving, the discrepancies with the official inventory agree with those reported in other studies.
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