Monolith formation and ring-stain suppression in low-pressure evaporation of poly(ethylene oxide) droplets

When droplets of dilute suspensions are left to evaporate the final dry residue is typically the familiar coffee-ring stain, with nearly all material deposited at the initial triple line (Deegan et al, Nature, vol. 389, 1997, pp. 827-829). However, aqueous poly(ethylene oxide) (PEO) droplets only form coffee-ring stains for a very narrow range of the experimental parameters molecular weight, concentration and drying rate. Instead, over a wide range of values they form either a flat disk or a very distinctive tall central monolith via a four-stage deposition process which includes a remarkable bootstrap-building step. To predict which deposit will form, we present a quantitative model comparing the effects of advective build-up at the triple line to diffusive flux and use this to calculate a dimensionless number χ. By experimentally varying concentration and flux (using a low-pressure drying chamber), the prediction is tested over nearly two orders of magnitude in both variables and shown to be in good agreement with the boundary between disks and monoliths at χ ≈ 1.6

Outflows from active galactic nuclei: The BLR-NLR metallicity correlation

The metallicity of active galactic nuclei (AGNs), which can be measured by emission line ratios in their broad and narrow line regions (BLRs and NLRs), provides invaluable information about the physical connection between the different components of AGNs. From the archival databases of the International Ultraviolet Explorer, the Hubble Space Telescope and the Sloan Digital Sky Survey, we have assembled the largest sample available of AGNs which have adequate spectra in both the optical and ultraviolet bands to measure the narrow line ratio [N II]/H{\alpha} and also, in the same objects, the broad-line N V/C IV ratio. These permit the measurement of the metallicities in the NLRs and BLRs in the same objects. We find that neither the BLR nor the NLR metallicity correlate with black hole masses or Eddington ratios, but there is a strong correlation between NLR and BLR metallicities. This metallicity correlation implies that outflows from BLRs carry metal-rich gas to NLRs at characteristic radial distances of ~ 1.0 kiloparsec. This chemical connection provides evidence for a kinetic feedback of the outflows to their hosts. Metals transported into the NLR enhance the cooling of the ISM in this region, leading to local star formation after the AGNs turn to narrow line LINERs. This post-AGN star formation is predicted to be observable as an excess continuum emission from the host galaxies in the near infrared and ultraviolet, which needs to be further explored.Comment: 19 pages, 13 figures, 3 tables. Accepted for publication at MNRA

Mechanism of activation of H2O2 by peroxidases: kinetic studies on a model system

AbstractKinetic studies on the peroxidase activity of microperoxidase-8 at pH 5.5–8.5 show that the rate is increased by raising the pH or by the presence of guanidinium ion. Comparison with published data on the peroxidases provides evidence that the enzyme activates H2O2 through the cooperative binding of H+ + HO−2 and suggests a role for the invariant distal Arg

Paradoxical popups: Why are they hard to catch?

Even professional baseball players occasionally find it difficult to gracefully approach seemingly routine pop-ups. This paper describes a set of towering pop-ups with trajectories that exhibit cusps and loops near the apex. For a normal fly ball, the horizontal velocity is continuously decreasing due to drag caused by air resistance. But for pop-ups, the Magnus force (the force due to the ball spinning in a moving airflow) is larger than the drag force. In these cases the horizontal velocity decreases in the beginning, like a normal fly ball, but after the apex, the Magnus force accelerates the horizontal motion. We refer to this class of pop-ups as paradoxical because they appear to misinform the typically robust optical control strategies used by fielders and lead to systematic vacillation in running paths, especially when a trajectory terminates near the fielder. In short, some of the dancing around when infielders pursue pop-ups can be well explained as a combination of bizarre trajectories and misguidance by the normally reliable optical control strategy, rather than apparent fielder error. Former major league infielders confirm that our model agrees with their experiences.Comment: 28 pages, 10 figures, sumitted to American Journal of Physic

Measuring Fundamental Galactic Parameters with Stellar Tidal Streams and SIM PlanetQuest

Extended halo tidal streams from disrupting Milky Way satellites offer new opportunities for gauging fundamental Galactic parameters without challenging observations of the Galactic center. In the roughly spherical Galactic potential tidal debris from a satellite system is largely confined to a single plane containing the Galactic center, so accurate distances to stars in the tidal stream can be used to gauge the Galactic center distance, R_0, given reasonable projection of the stream orbital pole on the X_GC axis. Alternatively, a tidal stream with orbital pole near the Y_GC axis, like the Sagittarius stream, can be used to derive the speed of the Local Standard of Rest (\Theta_LSR). Modest improvements in current astrometric catalogues might allow this measurement to be made, but NASA's Space Interferometry Mission (SIM PlanetQuest) can definitively obtain both R_0 and \Theta_LSR using tidal streams.Comment: 8 pages, 4 figures, accepted for publication in ApJ Letters (minor text revisions). Version with high resolution figures available at http://www.astro.caltech.edu/~drlaw/Papers/GalaxyParameters.pd

Wild Horses, Livestock, and Wildlife Use of Springs and Riparian Areas on the Devil\u27s Garden

In Modoc County, located in northeastern California there is a unique rangeland area heavily populated by wild horses and managed primarily by United States Forest Service known as the Devil\u27s Garden. Wild horses have significantly exceeded (4000 horses) appropriate management levels (206-402 horses) in recent years and expanded their range outside of the wild horse territory (258,000 acres) and on to private and tribal lands (over 450,000 acres). This increase has prompted concern about resource degradation particularly associated with riparian areas. In otherwise arid sage steppe rangelands, springs provide critical watering sources as well as wildlife habitat for sage grouse, deer, elk, pronghorn, and other wildlife. Our objective is to quantify the relative frequency, duration, and timing of use by horses, permitted livestock, and wildlife at spring locations. We correlate how varying levels of horse and/or livestock use affects spring site vegetation and riparian health standards. Ten representative study locations were selected on the Devil’s Garden and motion sensitive cameras were deployed at each location for 14-day sampling periods during the spring, summer and fall of 2015-2017. All photos were visually assessed to record species present, number of each species, and the time, date, and location of the observation. We present preliminary occupancy data, as well as results of corresponding vegetative cover, plant community, and bank alteration sampling. Implications for management and on-going research are discussed

Seismic stratigraphic framework of the continental shelf offshore Delmarva, USA: implications for Mid-Atlantic Bight evolution since the Pliocene

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Brothers, L. L., Foster, D. S., Pendleton, E. A., & Baldwin, W. E. Seismic stratigraphic framework of the continental shelf offshore Delmarva, USA: implications for Mid-Atlantic Bight evolution since the Pliocene. Marine Geology, 428, : (2020)106287, doi:10.1016/j.margeo.2020.106287.Understanding how past coastal systems have evolved is critical to predicting future coastal change. Using over 12,000 trackline kilometers of recently collected, co-located multi-channel boomer, sparker and chirp seismic reflection profile data integrated with previously collected borehole and vibracore data, we define the upper (< 115 m below mean lower low water) seismic stratigraphic framework offshore of the Delmarva Peninsula, USA. Twelve seismic units and 11 regionally extensive unconformities (U1-U11) were mapped over 5900 km2 of North America's Mid-Atlantic continental shelf. We interpret U3, U7, U9, U11 as transgressive ravinement surfaces, while U1,2,4,5,6,8,10 are subaerial unconformities illustrating distinct periods of lower sea-level. Based on areal distribution, stratigraphic relationships and dating results (Carbon 14 and amino acid racemization estimates) from earlier vibracore and borehole studies, we interpret the infilled channels as late Neogene and Quaternary courses of the Susquehanna, Potomac, Rappahannock, York, James rivers and tributaries, and a broad flood plain. These findings indicate that the region's geologic framework is more complex than previously thought and that Pleistocene paleochannels are abundant in the Mid-Atlantic. This study synthesizes and correlates the findings of other Atlantic Margin studies and establishes a large-scale Quaternary framework that enables more detailed stratigraphic analysis in the future. Such work has implications for inner continental shelf systems tract evolution, the relationship between antecedent geology and modern coastal systems, assessments of eustacy, glacial isostatic adjustment, and other processes and forcings that play a role in passive margin evolution.This work was supported by the U.S. Department of the Interior's Response to Hurricane Sandy

Progression of pulmonary hyperinflation and trapped gas associated with genetic and environmental factors in children with cystic fibrosis

BACKGROUND: Functional deterioration in cystic fibrosis (CF) may be reflected by increasing bronchial obstruction and, as recently shown, by ventilation inhomogeneities. This study investigated which physiological factors (airway obstruction, ventilation inhomogeneities, pulmonary hyperinflation, development of trapped gas) best express the decline in lung function, and what role specific CFTR genotypes and different types of bronchial infection may have upon this process. METHODS: Serial annual lung function tests, performed in 152 children (77 males; 75 females) with CF (age range: 6–18 y) provided data pertaining to functional residual capacity (FRC(pleth), FRC(MBNW)), volume of trapped gas (V(TG)), effective specific airway resistance (sR(eff)), lung clearance index (LCI), and forced expiratory indices (FVC, FEV(1), FEF(50)). RESULTS: All lung function parameters showed progression with age. Pulmonary hyperinflation (FRC(pleth )> 2SDS) was already present in 39% of patients at age 6–8 yrs, increasing to 67% at age 18 yrs. The proportion of patients with V(TG )> 2SDS increased from 15% to 54% during this period. Children with severe pulmonary hyperinflation and trapped gas at age 6–8 yrs showed the most pronounced disease progression over time. Age related tracking of lung function parameters commences early in life, and is significantly influenced by specific CFTR genotypes. The group with chronic P. aeruginosa infection demonstrated most rapid progression in all lung function parameters, whilst those with chronic S. aureus infection had the slowest rate of progression. LCI, measured as an index of ventilation inhomogeneities was the most sensitive discriminator between the 3 types of infection examined (p < 0.0001). CONCLUSION: The relationships between lung function indices, CFTR genotypes and infective organisms observed in this study suggest that measurement of other lung function parameters, in addition to spirometry alone, may provide important information about disease progression in CF