262 research outputs found
An unusual case of labial fusion
Labial fusion is sealing of labia minora in midline. It is also known as Labial adhesion or Labial agglutination or synechia vulvae. This condition is common in pre-pubertal females when estrogen levels are low and commonly resolves spontaneously post-puberty. Usually asymptomatic and typically treated conservatively. Medical treatment includes use of estrogen cream or betamethasone cream. Surgical treatment rarely required, if not responding to medical treatment or dense adhesions. This case report is unusual as it presented in a post-pubertal female and which needed surgical management
An unusual presentation of degenerating fibroid
Degeneration in a fibroid is seen when the blood supply falls inadequate to support the center of fibroid. Usually degeneration in a fibroid requires a symptomatic medical management. This is a case report of a degenerating fibroid that uncommonly presented in postpartum period as a retroperitoneal abscess requiring exploratory laparotomy
A Field-Based Approach for Determining ATOFMS Instrument Sensitivities to Ammonium and Nitrate
Aerosol time-of-flight mass spectrometry (ATOFMS) instruments measure the size and chemical composition of individual particles in real-time. ATOFMS chemical composition measurements are difficult to quantify, largely because the instrument sensitivities to different chemical species in mixed ambient aerosols are unknown. In this paper, we develop a field-based approach for determining ATOFMS instrument sensitivities to ammonium and nitrate in size-segregated atmospheric aerosols, using tandem ATOFMS-impactor sampling. ATOFMS measurements are compared with collocated impactor measurements taken at Riverside, CA, in September 1996, August 1997, and October 1997. This is the first comparison of ion signal intensities from a single-particle instrument with quantitative measurements of atmospheric aerosol chemical composition. The comparison reveals that ATOFMS instrument sensitivities to both NH_4^+ and NO_3^- decline with increasing particle aerodynamic diameter over a 0.32−1.8 μm calibration range. The stability of this particle size dependence is tested over the broad range of fine particle concentrations (PM_(1.8) = 17.6 ± 2.0−127.8 ± 1.8 μg m^(-3)), ambient temperatures (23−35 °C), and relative humidity conditions (21−69%), encountered during the field experiments. This paper describes a potentially generalizable methodology for increasing the temporal and size resolution of atmospheric aerosol chemical composition measurements, using tandem ATOFMS-impactor sampling
Coexistence and Phase Separation in Sheared Complex Fluids
We demonstrate how to construct dynamic phase diagrams for complex fluids
that undergo transitions under flow, in which the conserved composition
variable and the broken-symmetry order parameter (nematic, smectic,
crystalline, etc.) are coupled to shear rate. Our construction relies on a
selection criterion, the existence of a steady interface connecting two stable
homogeneous states. We use the (generalized) Doi model of lyotropic nematic
liquid crystals as a model system, but the method can be easily applied to
other systems, provided non-local effects are included.Comment: 4 pages REVTEX, 5 figures using epsf macros. To appear in Physical
Review E (Rapid Communications
Simulating emission and chemical evolution of coarse sea-salt particles in the Community Multiscale Air Quality (CMAQ) model
Chemical processing of sea-salt particles in coastal environments significantly impacts concentrations of particle components and gas-phase species and has implications for human exposure to particulate matter and nitrogen deposition to sensitive ecosystems. Emission of sea-salt particles from the coastal surf zone is known to be elevated compared to that from the open ocean. Despite the importance of sea-salt emissions and chemical processing, the US EPA's Community Multiscale Air Quality (CMAQ) model has traditionally treated coarse sea-salt particles as chemically inert and has not accounted for enhanced surf-zone emissions. In this article, updates to CMAQ are described that enhance sea-salt emissions from the coastal surf zone and allow dynamic transfer of HNO3, H2SO4, HCl, and NH3 between coarse particles and the gas phase. Predictions of updated CMAQ models and the previous release version, CMAQv4.6, are evaluated using observations from three coastal sites during the Bay Regional Atmospheric Chemistry Experiment (BRACE) in Tampa, FL in May 2002. Model updates improve predictions of NO3 , SO42 , NH4+, Na+, and Cl concentrations at these sites with only a 8% increase in run time. In particular, the chemically interactive coarse particle mode dramatically improves predictions of nitrate concentration and size distributions as well as the fraction of total nitrate in the particle phase. Also, the surf-zone emission parameterization improves predictions of total sodium and chloride concentration. Results of a separate study indicate that the model updates reduce the mean absolute error of nitrate predictions at coastal CASTNET and SEARCH sites in the eastern US. Although the new model features improve performance relative to CMAQv4.6, some persistent differences exist between observations and predictions. Modeled sodium concentration is biased low and causes under-prediction of coarse particle nitrate. Also, CMAQ over-predicts geometric mean diameter and standard deviation of particle modes at the BRACE sites. These over-predictions may cause too rapid particle dry deposition and partially explain the low bias in sodium predictions. Despite these shortcomings, the updates to CMAQ enable more realistic simulations of chemical processes in environments where marine air mixes with urban pollution. The model updates described in this article are included in the public release of CMAQv4.7 (http://www.cmaq-model.org)
Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE): Emissions of particulate matter from wood-and dung-fueled cooking fires, garbage and crop residue burning, brick kilns, and other sources
The Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) characterized widespread and under-sampled combustion sources common to South Asia, including brick kilns, garbage burning, diesel and gasoline generators, diesel groundwater pumps, idling motorcycles, traditional and modern cooking stoves and fires, crop residue burning, and heating fire. Fuel-based emission factors (EFs; with units of pollutant mass emitted per kilogram of fuel combusted) were determined for fine particulate matter (PM2.5), organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals, and organic species. For the forced-draft zigzag brick kiln, EFPM2.5 ranged from 12 to 19gkg-1 with major contributions from OC (7%), sulfate expected to be in the form of sulfuric acid (31.9%), and other chemicals not measured (e.g., particle-bound water). For the clamp kiln, EFPM2.5 ranged from 8 to 13gkg-1, with major contributions from OC (63.2%), sulfate (23.4%), and ammonium (16%). Our brick kiln EFPM2.5 values may exceed those previously reported, partly because we sampled emissions at ambient temperature after emission from the stack or kiln allowing some particle-phase OC and sulfate to form from gaseous precursors. The combustion of mixed household garbage under dry conditions had an EFPM2.5 of 7.4±1.2gkg-1, whereas damp conditions generated the highest EFPM2.5 of all combustion sources in this study, reaching up to 125±23gkg-1. Garbage burning emissions contained triphenylbenzene and relatively high concentrations of heavy metals (Cu, Pb, Sb), making these useful markers of this source. A variety of cooking stoves and fires fueled with dung, hardwood, twigs, and/or other biofuels were studied. The use of dung for cooking and heating produced higher EFPM2.5 than other biofuel sources and consistently emitted more PM2.5 and OC than burning hardwood and/or twigs; this trend was consistent across traditional mud stoves, chimney stoves, and three-stone cooking fires. The comparisons of different cooking stoves and cooking fires revealed the highest PM emissions from three-stone cooking fires (7.6-73gkg-1), followed by traditional mud stoves (5.3-19.7gkg-1), mud stoves with a chimney for exhaust (3.0-6.8gkg-1), rocket stoves (1.5-7.2gkg-1), induced-draft stoves (1.2-5.7gkg-1), and the bhuse chulo stove (3.2gkg-1), while biogas had no detectable PM emissions. Idling motorcycle emissions were evaluated before and after routine servicing at a local shop, which decreased EFPM2.5 from 8.8±1.3 to 0.71±0.45gkg-1 when averaged across five motorcycles. Organic species analysis indicated that this reduction in PM2.5 was largely due to a decrease in emission of motor oil, probably from the crankcase. The EF and chemical emissions profiles developed in this study may be used for source apportionment and to update regional emission inventories
A Field-Based Approach for Determining ATOFMS Instrument Sensitivities to Ammonium and Nitrate
Aerosol time-of-flight mass spectrometry (ATOFMS) instruments measure the size and chemical composition of individual particles in real-time. ATOFMS chemical composition measurements are difficult to quantify, largely because the instrument sensitivities to different chemical species in mixed ambient aerosols are unknown. In this paper, we develop a field-based approach for determining ATOFMS instrument sensitivities to ammonium and nitrate in size-segregated atmospheric aerosols, using tandem ATOFMS-impactor sampling. ATOFMS measurements are compared with collocated impactor measurements taken at Riverside, CA, in September 1996, August 1997, and October 1997. This is the first comparison of ion signal intensities from a single-particle instrument with quantitative measurements of atmospheric aerosol chemical composition. The comparison reveals that ATOFMS instrument sensitivities to both NH_4^+ and NO_3^- decline with increasing particle aerodynamic diameter over a 0.32−1.8 μm calibration range. The stability of this particle size dependence is tested over the broad range of fine particle concentrations (PM_(1.8) = 17.6 ± 2.0−127.8 ± 1.8 μg m^(-3)), ambient temperatures (23−35 °C), and relative humidity conditions (21−69%), encountered during the field experiments. This paper describes a potentially generalizable methodology for increasing the temporal and size resolution of atmospheric aerosol chemical composition measurements, using tandem ATOFMS-impactor sampling
Phase Separation of Rigid-Rod Suspensions in Shear Flow
We analyze the behavior of a suspension of rigid rod-like particles in shear
flow using a modified version of the Doi model, and construct diagrams for
phase coexistence under conditions of constant imposed stress and constant
imposed strain rate, among paranematic, flow-aligning nematic, and log-rolling
nematic states. We calculate the effective constitutive relations that would be
measured through the regime of phase separation into shear bands. We calculate
phase coexistence by examining the stability of interfacial steady states and
find a wide range of possible ``phase'' behaviors.Comment: 23 pages 19 figures, revised version to be published in Physical
Review
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