Coordinated aircraft and ship surveys for determining impact of river inputs on great lakes waters. Remote sensing results

The remote sensing results of aircraft and ship surveys for determining the impact of river effluents on Great Lakes waters are presented. Aircraft multi-spectral scanner data were acquired throughout the spring and early summer of 1976 at five locations: the West Basin of Lake Erie, Genesee River - Lake Ontario, Menomonee River - Lake Michigan, Grand River - Lake Michigan, and Nemadji River - Lake Superior. Multispectral scanner data and ship surface sample data are correlated resulting in 40 contour plots showing large-scale distributions of parameters such as total suspended solids, turbidity, Secchi depth, nutrients, salts, and dissolved oxygen. The imagery and data analysis are used to determine the transport and dispersion of materials from the river discharges, especially during spring runoff events, and to evaluate the relative effects of river input, resuspension, and shore erosion. Twenty-five LANDSAT satellite images of the study sites are also included in the analysis. Examples of the use of remote sensing data in quantitatively estimating total particulate loading in determining water types, in assessing transport across international boundaries, and in supporting numerical current modeling are included. The importance of coordination of aircraft and ship lake surveys is discussed, including the use of telefacsimile for the transmission of imagery

Spectral aerosol extinction (SpEx): a new instrument for in situ ambient aerosol extinction measurements across the UV/visible wavelength range

We introduce a new instrument for the measurement of in situ ambient aerosol extinction over the 300– 700 nm wavelength range, the spectral aerosol extinction (SpEx) instrument. This measurement capability is envisioned to complement existing in situ instrumentation, allowing for simultaneous measurement of the evolution of aerosol optical, chemical, and physical characteristics in the ambient environment. In this work, a detailed description of the instrument is provided along with characterization tests performed in the laboratory. Measured spectra of NO2 and polystyrene latex spheres (PSLs) agreed well with theoretical calculations. Good agreement was also found with simultaneous aerosol extinction measurements at 450, 530, and 630 nm using CAPS PMex instruments in a series of 22 tests including nonabsorbing compounds, dusts, soot, and black and brown carbon analogs. SpEx measurements are expected to help identify the presence of ambient brown carbon due to its 300 nm lower wavelength limit compared to measurements limited to longer UV and visible wavelengths. Extinction spectra obtained with SpEx contain more information than can be conveyed by a simple power law fit (typically represented by Ångström exponents). Planned future improvements aim to lower detection limits and ruggedize the instrument for mobile operation

The performance of magnetorheological fluid in squeeze mode

Abstract: In magnetorheological (MR) fluid, the rheological properties can be changed in a controlled way, the changes being reversible and dependent on the strength of the magnetic field. The fluids have potentially beneficial applications when placed in various geometrical arrangements. The squeeze mode is a geometrical arrangement where two flat parallel solid surfaces, facing each other, are pushed towards each other by an external force operating at right angles to the surfaces. The liquid initially in the gap between them is free to move away from this increasingly small gap, and it does so by flowing parallel to the surfaces, and collecting in a region where it is no longer in the gap between them. The performance of an MR fluid in compression ( squeeze) mode has been studied with the magnetic field being generated by a coil carrying different magnitudes of DC electrical current. A test rig was designed to perform this operation with the flat surfaces being horizontal and being pushed together in a vertical direction and the liquid being forced to move in all directions in a horizontal plane. The rig operated by decreasing the size of the gap at a constant rate. For each trial the current in the coil was kept constant and the instantaneous compressive force was recorded. When plotting compressive stress against compressive strain for each trial, the slope of the curve was found to be larger in general when the current was larger. This was an expected result; however, the behaviour is more complicated than this. For a significant range of values of compressive strain, the slope falls to zero, so that the compressive stress shows no increase during this period while the compressive strain continues to increase. The details of this behaviour are strongly dependent on the initial size of the ga

Flow induced by a sphere settling in an aging yield-stress fluid

We have studied the flow induced by a macroscopic spherical particle settling in a Laponite suspension that exhibits a yield-stress, thixotropy and shear-thinning. We show that the fluid thixotropy (or aging) induces an increase with time of both the apparent yield stress and shear-thinning properties but also a breaking of the flow fore-aft symmetry predicted in Hershel-Bulkley fluids (yield-stress, shear-thinning fluids with no thixotropy). We have also varied the stress exerted by the particles on the fluid by using particles of different densities. Although the stresses exerted by the particles are of the same order of magnitude, the velocity field presents utterly different features: whereas the flow around the lighter particle shows a confinement similar to the one observed in shear-thinning fluids, the wake of the heavier particle is characterized by an upward motion of the fluid ("negative wake"), whatever the fluid's age. We compare the features of this negative wake to the one observed in viscoelastic shear-thinning fluids (polymeric or micelle solutions). Although the flows around the two particles strongly differ, their settling behaviors display no apparent difference which constitutes an intriguing result and evidences the complexity of the dependence of the drag factor on flow field

Observational evidence for the convective transport of dust over the central United States

Bulk aerosol composition and aerosol size distributions measured aboard the DC-8 aircraft during the Deep Convective Clouds and Chemistry Experiment mission in May/June 2012 were used to investigate the transport of mineral dust through nine storms encountered over Colorado and Oklahoma. Measurements made at low altitudes (\u3c5 km mean sea level (MSL)) in the storm inflow region were compared to those made in cirrus anvils (altitude \u3e 9 km MSL). Storm mean outflow Ca2+ mass concentrations and total coarse (1 µm \u3c diameter \u3c 5 µm) aerosol volume (Vc) were comparable to mean inflow values as demonstrated by average outflow/inflow ratios greater than 0.5. A positive relationship between Ca2+, Vc, ice water content, and large (diameter \u3e 50 µm) ice particle number concentrations was not evident; thus, the influence of ice shatter on these measurements was assumed small. Mean inflow aerosol number concentrations calculated over a diameter range (0.5 µm \u3c diameter \u3c 5.0 µm) relevant for proxy ice nuclei (NPIN) were ~15–300 times higher than ice particle concentrations for all storms. Ratios of predicted interstitial NPIN (calculated as the difference between inflow NPIN and ice particle concentrations) and inflow NPIN were consistent with those calculated for Ca2+ and Vc and indicated that on average less than 10% of the ingested NPIN were activated as ice nuclei during anvil formation. Deep convection may therefore represent an efficient transport mechanism for dust to the upper troposphere where these particles can function as ice nuclei cirrus forming in situ

Patterns of mtDNA Diversity in Northwestern North America

The mitochondrial DNA (mtDNA) haplogroups of 54 full-blooded modern and 64 ancient Native Americans from northwestern North America were determined. The control regions of 10 modern and 30 ancient individuals were sequenced and compared. Within the Northwest, the frequency distribution for haplogroup A is geographically structured, with haplogroup A decreasing with distance from the Pacific Coast. The haplogroup A distribution suggests that a prehistoric population intrusion from the subarctic and coastal region occurred on the Columbia Plateau in prehistoric times. Overall, the mtDNA pattern in the Northwest suggests significant amounts of gene flow among Northwest Coast, Columbia Plateau, and Great Basin populations

SARS-CoV-2 Seroprevalence: Demographic and Behavioral Factors Associated With Seropositivity Among College Students in a University Setting

Purpose: Examine SARS-CoV-2 seroprevalence and the association of seropositivity with demographic, geographic, and behavioral variables among University of North Carolina Chapel Hill (UNC-CH) undergraduate students enrolled in the fall 2020 semester. Methods: All UNC-CH undergraduate students were invited to participate in the Heelcheck study; participants were weighted to the UNC-CH undergraduate population using raking methods. We estimate SARS-CoV-2 seroprevalence at study entrance (11/12/2020–12/10/2020) and bivariable associations using log-binomial regression. Results: SARS-CoV-2 seroprevalence was 7.3% (95% confidence interval (CI): 5.4%–9.2%) at baseline. Compared to students who were living off-campus in the Chapel Hill/Carrboro area (CH) for the Fall 2020 semester (8.6% seroprevalence), students who never returned to CH had lower seroprevalence (1.9%, prevalence ratio (PR), 95% CI: 0.22, 0.06–0.81), whereas, students who started the semester on-campus and moved to off-campus CH housing had 18.9% seroprevalence (PR, 95% CI: 2.21, 1.04–4.72) and students who spent the semester living in a Sorority/Fraternity house had 46.8% seroprevalence (PR, 95% CI: 5.47, 2.62–11.46). Those who predicted they would join an indoor party unmasked had 3.8 times the seroprevalence of those who indicated they would not attend (PR, 95% CI: 3.80, 1.58–9.16). Compared to students who disagreed with the statement “…I am not going to let COVID-19 stop me from having fun…”, those who agreed had higher seroprevalence (14.0% vs. 5.7%; (PR, 95% CI: 2.45, 1.13–5.32)). Discussion: Increased seroprevalence was associated with congregate living and participation (actual or endorsed) in social activities. During pandemics, universities must create safe socializing opportunities while minimizing transmission

Association of statin pretreatment with collateral circulation and final infarct volume in acute ischemic stroke patients: A meta-analysis

Statin pretreatment (SP) is associated with improved outcomes in acute ischemic stroke (AIS) patients. Collateral circulation status and final infarct volume (FIV) are independent predictors of functional outcome in AIS.info:eu-repo/semantics/publishedVersio

Aircraft Engine Particulate Matter Emissions from Sustainable Aviation Fuels: Results from Ground-Based Measurements during the NASA/DLR Campaign ECLIF2/ND-MAX

The use of alternative jet fuels by commercial aviation has increased substantially in recent years. Beside the reduction of carbon dioxide emission, the use of sustainable aviation fuels (SAF) may have a positive impact on the reduction of particulate emissions. This study summarizes the results from a ground-based measurement activity conducted in January 2018 as part of the ECLIF2/ND-MAX campaign in Ramstein, Germany. Two fossil reference kerosenes and three different blends with the renewable fuel component HEFA-SPK (Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene) were burned in an A320 with V2527-A5 engines to investigate the effect of fuel naphthalene/aromatic content and the corresponding fuel hydrogen content on non-volatile particle number and mass emissions. Reductions up to 70% in non-volatile particle mass emission compared to the fossil reference fuel were observed at low power settings. The reduction trends to decrease with increasing power settings. The fuels showed a decrease in particle emission with increasing fuel hydrogen content. Consequently, a second fossil fuel with similar hydrogen content as one of the HEFA blends featured similar reduction factors in particle mass and number. Changes in the fuel naphthalene content had significant impact on the particle number emission. A comparison to in-flight emission data shows similar trends at cruise altitudes. The measurements highlight the importance of individual fuel components in regulating engine emissions, particularly at the low thrust settings typically employed during ground operations (e.g. during idle and taxi). Therefore, when selecting and mixing SAF blends to meet present fuel-certification standards, attention should be paid to minimizing complex aromatic content to achieve the greatest possible air quality and climate benefits