Search

A particle-into-liquid sampler (PILS) was coupled to a flow-through conductivity cell to provide a continuous, nondestructive, online measurement in support of offline ion chromatography analysis. The conductivity measurement provides a rapid assessment of the total ion concentration augmenting slower batch-sample data from offline analysis and is developed primarily to assist airborne measurements, where fast time-response is essential. A conductivity model was developed for measured ions and excellent closure was derived for laboratory-generated aerosols (97% conductivity explained, R(2) > 0.99). The PILS-conductivity measurement was extensively tested throughout the NASA Cloud, Aerosol and Monsoon Processes: Philippines Experiment (CAMP(2)Ex) during nineteen research flights. A diverse range of ambient aerosol was sampled from biomass burning, fresh and aged urban pollution, and marine sources. Ambient aerosol did not exhibit the same degree of closure as the laboratory aerosol, with measured ions only accountable for 43% of the conductivity. The remaining fraction of the conductivity was examined in combination with ion charge balance and found to provide additional supporting information for diagnosing and modeling particle acidity. An urban plume case study was used to demonstrate the utility of the measurement for supplementing compositional data and augmenting the temporal capability of the PILS.

Sublime expression of three ectocranial occipital superstructures (OSSs)—occipital torus tubercles (TOTs), retromastoid processes (PRs), and posterior supramastoid tubercles (TSPs)—is virtually res...

Aircraft-based aerosol sampling in clouds is complicated by the generation of shatter artifact particles from aerodynamic or impaction breakup of cloud droplets and ice particles in and around the aerosol inlet. Aerodynamic breakup occurs when the Weber number of a droplet, which primarily depends on the droplet size and the magnitude of the relative motion of the droplet and the local air mass, exceeds a critical value. Impaction breakup of a droplet occurs when the droplet's impaction breakup parameter, K, which is a combination of Weber and Ohnesorge numbers, exceeds a critical value. Considering these two mechanisms, the critical breakup diameters are estimated for two aerosol inlets of different designs—a conventional forward-facing solid diffuser inlet (SDI) and a cross-flow sampling sub-micron aerosol inlet (SMAI). From numerical simulations, it is determined that cloud droplets of all sizes will experience impaction breakup in SDI, while only droplets larger than ∼16 μm will experience impaction b...

The optical properties of soot particles in plumes emanating from a high bypass turbofan aircraft engine (V2527) were measured at distances of 40–80 m behind the engine with a cavity-enhanced phase shift (CAPS)-based extinction monitor (known as the CAPS PMex) and a multi-angle absorption photometer, both operating at wavelength ∼630 nm. Integrated plume measurements from the two instruments were highly correlated with each other (r 2 > 0.99, N = 12) and with measured carbon dioxide emission concentrations. Ancillary measurements indicated that the soot particle volume-weighted mobility diameter distribution peaked at 60 nm with a full width at half maximum of ∼60 nm. The soot single scattering albedo determined using the absorption and extinction measurements under engine idle conditions was 0.05 ± 0.02 (where the uncertainty represents 2σ precision), in agreement with previous measurements of aircraft exhaust. The engine soot emission index (mass soot per mass fuel burned) for this particular engine, de...

Particulate emission indices (per kg fuel) have been determined by sampling the advected plumes of in-use commercial aircraft at two different airports using a novel approach. Differences are observed in the number, magnitude, and composition of the particle emissions between idle and take-off. At the first airport, Electrical Low Pressure Impactor (ELPI) data indicate that number based emission indices (EI n ) vary by an order of magnitude for take-off plumes from different aircraft. Additionally, EI n values for idle plumes are greater than take-off. At the second airport, EI n values derived from condensation particle counter (CPC) measurements span ∼ an order of magnitude (3–50 × 10 15 particles per kg fuel). The median values of the idle and take-off plumes were 1.8 × 10 16 and 7.6 × 10 15 particles per kg fuel, respectively. For take-off plumes, the magnitude of the particulate emission index is not correlated with NO x at either airport. The surface properties of the particulate emissions in take-o...

Few empirical findings or technical guidelines are available on the current transition from analog to digital audio recording in childhood speech sound disorders. Of particular concern in the present context was whether a transition from analog- to digital-based transcription and coding of prosody and voice features might require re-standardizing a reference database for research in childhood speech sound disorders. Two research transcribers with different levels of experience glossed, transcribed, and prosody-voice coded conversational speech samples from eight children with mild to severe speech disorders of unknown origin. The samples were recorded, stored, and played back using representative analog and digital audio systems. Effect sizes calculated for an array of analog versus digital comparisons ranged from negligible to medium, with a trend for participants' speech competency scores to be slightly lower for samples obtained and transcribed using the digital system. We discuss the implications of these and other findings for research and clinical practise.

The formation of ZrO2, Al2O3/ZrO2, and SiO2/ZrO2 coatings on TiO2 particles by a continuous gas-phase process was studied. Titania particles were formed by the reaction of TiCl4 vapor with O2 in a hot-wall tubular reactor at 1300°C and were mixed with ZrCl4 and AlCl3 or SiCl4 vapors near the end of the reactor. The ZrCl4/TiCl4 molar ratio was varied from 6.7 x 10-4 to 5 x 10-3 while the AlCl3/TiCl4and SiCl4/TiCl4 molar ratios varied in the ranges 8 x 10-3-8 x 10-2 and 2 x 10-2-8 x 10-2, respectively. Discrete tetragonal ZrO2 nanoparticles of average diameter 20 nm were formed on the surfaces of the titania particles at a surface concentration that increased with the ZrCl4 gas-phase concentration. The sequential introduction of AlCl3 and ZrCl4 vapors resulted in composite coatings. These consisted of dense, coherent, amorphous, and smooth Al2O3 layers approximately 10 nm thick, on top of which ZrO2 nanocrystalline particles were dispersed in a similar pattern as in the absence of Al2O3. Concentration depth...

The well-preserved immature skeletons of three individuals, aged at about five and one-half fetal months, nine and one-half fetal months, and one year, are examined. The youngest was delivered to the Human Identification Laboratory in its surrounding matrix, thus enabling precise identification of individual bones. This fact takes on added importance because vertebral anomalies are present. These anomalies, fusions of adjacent neural hemi-arches, are also exhibited by the individual aged at nine and one-half fetal months. Additional abnormalities in two ribs of this infant indicate the possibility of Klippel-Feil Syndrome, an inherited cervical spine disorder. The one-year-old infant has a marked facial asymmetry, another manifestation of this syndrome, thus suggesting a genetic link among all three individuals. Finally, cribra orbitalia, which could have been caused by an iron-deficiency anemia, may be evident in the one-year-old child.