Application of an atomic oxygen beam facility to the investigation of shuttle glow chemistry

A facility for the investigation of the interactions of energetic atomic oxygen with solids is described. The facility is comprised of a four chambered, differentially pumped molecular beam apparatus which can be equipped with one of a variety of sources of atomic oxygen. The primary source is a dc arc heated supersonic nozzle source which produces a flux of atomic oxygen in excess of 10 to the 15th power sq cm/sec at the target, at a velocity of 3.5 km/sec. Results of applications of this facility to the study of the reactions of atomic oxygen with carbon and polyimide films are briefly reviewed and compared to data obtained on various flights of the space shuttle. A brief discussion of possible application of this facility to investigation of chemical reactions which might contribute to atmosphere induced vehicle glow is presented

Laboratory studies of atomic oxygen reactions with solids

Atomic beam experiments were performed to investigate the rate of atomic oxygen etching of carbon and polyimide films. The main emphasis of these experiments was on gaining an understanding of the role of atomic oxygen translational energy and substrate temperature in promoting the reactions. The experimental facility and techniques are described and results reviewed

Disc-planet interactions in sub-keplerian discs

One class of protoplanetary disc models, the X-wind model, predicts strongly subkeplerian orbital gas velocities, a configuration that can be sustained by magnetic tension. We investigate disc-planet interactions in these subkeplerian discs, focusing on orbital migration for low-mass planets and gap formation for high-mass planets. We use linear calculations and nonlinear hydrodynamical simulations to measure the torque and look at gap formation. In both cases, the subkeplerian nature of the disc is treated as a fixed external constraint. We show that, depending on the degree to which the disc is subkeplerian, the torque on low-mass planets varies between the usual Type I torque and the one-sided outer Lindblad torque, which is also negative but an order of magnitude stronger. In strongly subkeplerian discs, corotation effects can be ignored, making migration fast and inward. Gap formation near the planet's orbit is more difficult in such discs, since there are no resonances close to the planet accommodating angular momentum transport. In stead, the location of the gap is shifted inwards with respect to the planet, leaving the planet on the outside of a surface density depression. Depending on the degree to which a protoplanetary disc is subkeplerian, disc-planet interactions can be very different from the usual Keplerian picture, making these discs in general more hazardous for young planets.Comment: 4 pages, 4 figures, accepted in Astronomy and Astrophysics Letters, minor language change

Numerical simulations of the type III migration:I. Disc model and convergence tests

We investigate the fast (type III) migration regime of high-mass protoplanets orbiting in protoplanetary disks. This type of migration is dominated by corotational torques. We study the details of flow structure in the planet's vicinity, the dependence of migration rate on the adopted disc model, and the numerical convergence of models (independence of certain numerical parameters such as gravitational softening). We use two-dimensional hydrodynamical simulations with adaptive mesh refinement,based on the FLASH code with improved time-stepping scheme. We perform global disk simulations with sufficient resolution close to the planet, which is allowed to freely move throughout the grid. We employ a new type of equation of state in which the gas temperature depends on both the distance to the star and planet, and a simplified correction for self-gravity of the circumplanetary gas. We find that the migration rate in the type III migration regime depends strongly on the gas dynamics inside the Hill sphere (Roche lobe of the planet) which, in turn, is sensitive to the aspect ratio of the circumplanetary disc. Furthermore, corrections due to the gas self-gravity are necessary to reduce numerical artifacts that act against rapid planet migration. Reliable numerical studies of Type III migration thus require consideration of both the thermal andthe self-gravity corrections, as well as a sufficient spatial resolution and the calculation of disk-planet attraction both inside and outside the Hill sphere. With this proviso, we find Type III migration to be a robust mode of migration, astrophysically promising because of a speed much faster than in the previously studied modes of migration.Comment: 17 pages, 15 figures, submitted to MNRAS. Comments welcom

The Dynamical Origin of the Multi-Planetary System HD45364

The recently discovered planetary system HD45364 which consists of a Jupiter and Saturn mass planet is very likely in a 3:2 mean motion resonance. The standard scenario to form planetary commensurabilities is convergent migration of two planets embedded in a protoplanetary disc. When the planets are initially separated by a period ratio larger than two, convergent migration will most likely lead to a very stable 2:1 resonance for moderate migration rates. To avoid this fate, formation of the planets close enough to prevent this resonance may be proposed. However, such a simultaneous formation of the planets within a small annulus, seems to be very unlikely. Rapid type III migration of the outer planet crossing the 2:1 resonance is one possible way around this problem. In this paper, we investigate this idea in detail. We present an estimate for the required convergent migration rate and confirm this with N-body and hydrodynamical simulations. If the dynamical history of the planetary system had a phase of rapid inward migration that forms a resonant configuration, we predict that the orbital parameters of the two planets are always very similar and hence should show evidence of that. We use the orbital parameters from our simulation to calculate a radial velocity curve and compare it to observations. Our model can explain the observational data as good as the previously reported fit. The eccentricities of both planets are considerably smaller and the libration pattern is different. Within a few years, it will be possible to observe the planet-planet interaction directly and thus distinguish between these different dynamical states.Comment: 9 pages, 9 figures - accepted for publication in Astronomy and Astrophysic

Crystal structure of Cu-Sn-In alloys around the {\eta} phase field studied by neutron diffraction

The study of the Cu-Sn-In ternary system has become of great importance in recent years, due to new environmental regulations forcing to eliminate the use of Pb in bonding technologies for electronic devices. A key relevant issue concerns the intermetallic phases which grow in the bonding zone and are determining in their quality and performance. In this work, we focus in the {\eta}-phase (Cu2In or Cu6Sn5) that exists in both end binaries and as a ternary phase. We present a neutron diffraction study of the constitution and crystallography of a series of alloys around the 60 at.% Cu composition, and with In contents ranging from 0 to 25 at.%, quenched from 300\degreeC. The alloys were characterized by scanning electron microscopy, probe microanalysis and high-resolution neutron diffraction. The Rietveld refinement of neutron diffraction data allowed to improve the currently available model for site occupancies in the hexagonal {\eta}-phase in the binary Cu-Sn as well as in ternary alloys. For the first time, structural data is reported in the ternary Cu-Sn-In {\eta}-phase as a function of composition, information that is of fundamental technological importance as well as valuable input data for ongoing modelisations of the ternary phase diagram.Comment: 8 pages, 10 figure

Professional Development Impact on Quality Interactions in Home-Based Early Childhood Settings

Recent literature was examined to explore the relationship between professional development and quality interactions in home-based early childhood settings. Home-based child care was identified as a setting preferred by parents (Melvin et al., 2022). However, the educators in these settings often worked alone, worked long hours, and were less likely to have a degree than educators in other early childhood settings (Durden et al., 2016). The understanding of what constituted quality in these under-recognized settings was more challenging to quantify and less studied than quality in other early education settings (Han et al., 2021). A thorough literature review was conducted, and data was synthesized to extract information about home-based settings, degree attainment, professional development needs, quality indicators, and how educators in these settings defined quality. Other factors that may impact quality interactions were identified. Home-based early childhood educators overwhelmingly were found to view themselves as professionals and defined quality in home-based settings differently than measurement tool definitions (Hooper et al., 2021). Process and practical quality were surmised to be the niche in which home-based educators excel (Lanigan, 2011). It was found that supporting this subset of early childhood educators required regular and ongoing professional development that honored and acknowledged the uniqueness of this setting (Abell et al., 2014; Durden et al., 2016)

Characterization of thiG Gene in B. cepacia as a Thiazole Synthase

Burkholderia cepacia is a gram-negative bacterium found in water and soil that is known to cause infection in plants and humans. Limited treatments are available for this bacteria due to widespread antibiotic resistance and a lack of knowledge of the mechanisms of virulence used by B. cepacia. This work seeks to identify virulence factors needed for pathogenesis. Transposon mutagenesis in B. cepacia ATCC 25416 was used to generate mutants that were screened for defects in pathogenesis in an onion infection model and mutant 370 was selected for further studies. Recent data from the model demonstrate that the mutant produced smaller wound sizes beginning at 48 hours post-infection, indicating that the gene product may be involved in promoting infection in a host. Genetic characterization of mutant 370 determined that the mutation occurred in the thiG gene on chromosome 1, whose product is predicted to be a thiazole synthase, which is likely used in the metabolic processes of the bacteria and could play a role in infection. The transmembrane hydropathy plot suggests that the gene product is found in the cytoplasm, which corresponds to its expected use in the metabolism. Examination of the growth and biofilm production assays revealed that the thiG mutant displays stunted growth and limited biofilm production, suggesting that thiG is not involved in virulence but instead plays an important role in the basic metabolism of the bacteria. Future research will focus on determining thiG’s involvement in metabolism to determine if thiG could be an important target for antibacterials.https://digitalcommons.snc.edu/collaborative_presentations/1082/thumbnail.jp

Optimal Joint Angles of a Free Throw Shot in NCAA Division II Women\u27s Collegiate Basketball Players

The purpose of the present study was to analyze the free throw shooting form of NCAA Division II women’s basketball collegiate athletes. Joint angles of the wrist, elbow, shoulder, hip, knee, and ankle were assessed in the sagittal plane to identify differences between proficient (³ 80%) and non-proficient (\u3c 80%) shooters, along with differences between made and missed free throw shots. Fourteen healthy athletes (19.9 ± 1.5 yrs.) completed four sessions of 25 free throw attempts for a total of 100 attempts per athlete and video data on each of the six joint angles was examined in both the preparation and follow-through phases. Proficient (³ 80%) free throw shooters had more hip flexion, along with less wrist extension, elbow flexion, knee flexion, and ankle dorsiflexion than non-proficient (\u3c 80%) shooters in the preparation phase. Proficient shooters also have more hip extension, and less wrist flexion, elbow extension, knee extension, and plantarflexion than non-proficient shooters in the follow-through phase. Greater shoulder extension at the preparation phase was found to be significant (p £ 0.014), and less knee extension at the follow-through phase approached significance (p £ 0.064) between made and missed free throw shots in this population. Results from this study have potential to be applied to coaching cues and form correction at the free throw line in basketball athletes

Dynamics of core accretion

(shortened) We perform 3D hydrodynamic simulations of gas flowing around a planetary core of mass \mplan=10\me embedded in a near Keplerian background flow, using a modified shearing box approximation. We employ a nested grid hydrodynamic code with as many as six nested grids, providing spatial resolution on the finest grid comparable to the present day diameters of Neptune and Uranus. We find that a strongly dynamically active flow develops such that no static envelope can form. The activity is not sensitive to plausible variations in the rotation curve of the underlying disk. It is sensitive to the thermodynamic treatment of the gas, as modeled by prescribed equations of state (either `locally isothermal' or `locally isentropic') and the temperature of the background disk material. The activity is also sensitive to the shape and depth of the core's gravitational potential, through its mass and gravitational softening coefficient. The varying flow pattern gives rise to large, irregular eruptions of matter from the region around the core which return matter to the background flow: mass in the envelope at one time may not be found in the envelope at any later time. The angular momentum of material in the envelope, relative to the core, varies both in magnitude and in sign on time scales of days to months near the core and on time scales a few years at distances comparable to the Hill radius. We show that material entering the dynamically active environment may suffer intense heating and cooling events the durations of which are as short as a few hours to a few days. Peak temperatures in these events range from $T \sim 1000$ K to as high as $T \sim 3-4000$ K, with densities $\rho\sim 10^{-9}-10^{-8}$ g/cm$^3$. These time scales, densities and temperatures span a range consistent with those required for chondrule formation in the nebular shock model.Comment: Accepted for publication in MNRA