Understanding the Experience of Weight Gain and Body Image During Adolescent Pregnancy

This qualitative descriptive study explores the experience of adolescent pregnancy and the influence of body image and other factors on weight gain. It identified three main themes through content analysis: Continuity of Care, Adolescent Investment in a Healthy Pregnancy, and the Impact of Pregnancy Symptoms

Membrane Vesicles as a Vaccine Platform For Salmonella

Salmonella species cause substantial morbidity, mortality, and disease burden globally with multiple clinical syndromes. A protective host defense to Salmonella infection requires both T-cell (cell-mediated) and B-cell (humoral) immune response. Current vesicle vaccine platforms include inactivated, non-replicating, or synthetic liposomes which do not produce a robust immune response because they lack foreign distinctness and complexity. Membrane vesicles (MVs), released in a conserved process by Gramnegative bacteria, are discrete, spherical nano-particles that are composed of outer membrane and periplasmic constituents including lipopolysaccharides and proteins. MVs are promising vaccine candidates for the following reasons: their intrinsic adjuvant properties, genetically malleability via the parental bacterial strain that can alter vaccine efficacy, a minimal production cost, and they are stable in powder form. As biologically derived but nonreplicating particles they are important in the vaccine strategy for immunocompromised populations. My findings reveal MVs posses important inflammatory properties that demonstrate a viable vaccine platform potential for Salmonella infection

Free volume variation with molecular weight of polymers

Free volume measurements were made in several molecular weight fractions of two different geometries of poly(arylene ether ketone)s. Free volumes were measured using positron lifetime spectroscopy. It has been observed that the free volume cell size V(sub f) varies with the molecular weight M of the test samples according to an equation of the form V(sub f) = AM(B), where A and B are constants. The molecular weights computed from the free volume cell sizes are in good agreement with the values measured by gel permeation chromatography

HyPer - a Green Monopropellant for Small Satellite Propulsion

The theory, experimentation, and implementation of a green monopropellant propulsion system for small satellites is described, including the environmental testing and integration of the system onto a CubeSat slated to launch in early 2022. HyPer, named after its propellant hydrogen peroxide, was specifically designed with the smaller size, lower power availability, and challenging launch conditions of CubeSats in mind. Instead of using a traditional monopropellant management system –pressurized reactive liquid forced to a catalyst bed – HyPer uses the vacuum of space to boil the stored liquid hydrogen peroxide, delivering a highly-tunable flow of reactive vapor to the catalyst. This lower flow rate enables HyPer to target the millinewton range of thrust without many of the hydrodynamic complications (e.g., droplet and bubble formation, and thermocapillary flows) that prevent full decomposition in low-thrust liquid systems. This thrust range allows for a wide variety of mission-enabling maneuvers for low mass systems, including (1) constellation management, (2) formation flying, (3) rendezvous, (4) extended mission durations, and (5) orbit reconfiguration. Due to the reaction at the catalyst bed, HyPer still retains the performance associated with a monopropellant system, which allows for a smaller total propulsion package. The HyPer flight unit is exhaustively detailed from design decisions to performance metrics. There are several unique design elements due to the novelty of the concept. These include a propellant management device that controls the flow of vapor for propulsive activities and also allows for oxygen venting during long storage intervals, commercial-off-the-shelf components adapted for the harsh hydrogen peroxide environment, and a nozzle assembly designed to retain as much heat as possible in the catalyst bed. Performance was characterized by direct measurements of pressure, temperature, and mass flow rate in a vacuum environment. Launch survivability and on-orbit operability were verified with vibration, thermal cycle, leak rate, and life testing. On-board flight software and ground commanding were tested prior to integration to ensure appropriate timing and activation of safety features in case of an anomaly. HyPer’s checkout testing at different levels of satellite integration and propellant loading plan are also outlined

Discovery of Seven Companions To Intermediate-Mass Stars With Extreme Mass Ratios in the Scorpius-Centaurus Association

We report the detection of seven low-mass companions to intermediate-mass stars (SpT B/A/F; M similar to 1.5-4.5M(circle dot)) in the Scorpius-Centaurus (Sco-Cen) Association using nonredundant aperture masking interferometry. Our newly detected objects have contrasts Delta L' approximate to 4-6, corresponding to masses as low as similar to 20 M-Jup and mass ratios of q approximate to 0.01-0.08, depending on the assumed age of the target stars. With projected separations rho approximate to 10-30 AU, our aperture masking detections sample an orbital region previously unprobed by conventional adaptive optics imaging of intermediate-mass Sco-Cen stars covering much larger orbital radii (similar to 30-3000 AU). At such orbital separations, these objects resemble higher-mass versions of the directly imaged planetary mass companions to the 10-30 Myr, intermediate-mass stars HR 8799, beta Pictoris, and HD 95086. These newly discovered companions span the brown dwarf desert, and their masses and orbital radii provide a new constraint on models of the Formation of low-mass stellar and substellar companions to intermediate-mass stars.NASA through the Sagan Fellowship ProgramNSF Astronomy and Astrophysics Postdoctoral Fellowship AST-1203023Clay FellowshipNASA through Hubble Fellowship 51257.01AURA, Inc., for NASA NAS 5-26555W. M. Keck FoundationAstronom

Erupting Cataclysmic Variable Stars in the Nearest Globular Cluster, NGC 6397: Intermediate Polars?

NGC 6397 is the closest globular cluster, and hence the ideal place to search for faint stellar populations such as cataclysmic variables (CVs). HST and Chandra observers have identified nine certain and likely CVs in this nearby cluster, including several magnetic CV candidates. We have combined our recent UV imagery with archival HST images of NGC 6397 to search for new CV candidates and especially to look for dwarf nova-like eruptive events. We find remarkable and somewhat unexpected dwarf nova-like eruptions of the two well-known cataclysmic systems CV2 and CV3. These two objects have been claimed to be {\it magnetic} CVs, as indicated by their helium emission-line spectra. Magnetic fields in CVs are usually expected to prevent the disk instability that leads to dwarf nova eruptions. In fact, most field magnetic CVs are observed to not undergo eruptions. Our observations of the dwarf nova eruptions of CV2 and CV3 can be reconciled with these objects' HeII emission lines if both objects are infrequently-erupting intermediate polars, similar to EX Hya. If this is the case for most globular cluster CVs then we can reconcile the many X-ray and UV bright CV candidates seen by Chandra and HST with the very small numbers of erupting dwarf novae observed in cluster cores.Comment: 12 pages, 3 figures. Accepted for publication in The Astronomical Journal. Two additional authors adde

No difference in orbital parameters of RV-detected giant planets between 0.1 and 5 au in single vs multi-stellar systems

Our Keck/NIRC2 imaging survey searches for stellar companions around 144 systems with radial velocity (RV) detected giant planets to determine whether stellar binaries influence the planets' orbital parameters. This survey, the largest of its kind to date, finds eight confirmed binary systems and three confirmed triple systems. These include three new multi-stellar systems (HD 30856, HD 86081, and HD 207832) and three multi-stellar systems with newly confirmed common proper motion (HD 43691, HD 116029, and HD 164509). We combine these systems with seven RV planet-hosting multi-stellar systems from the literature in order to test for differences in the properties of planets with semimajor axes ranging between 0.1-5 au in single vs multi-stellar systems. We find no evidence that the presence or absence of stellar companions alters the distribution of planet properties in these systems. Although the observed stellar companions might influence the orbits of more distant planetary companions in these systems, our RV observations currently provide only weak constraints on the masses and orbital properties of planets beyond 5 au. In order to aid future efforts to characterize long period RV companions in these systems, we publish our contrast curves for all 144 targets. Using four years of astrometry for six hierarchical triple star systems hosting giant planets, we fit the orbits of the stellar companions in order to characterize the orbital architecture in these systems. We find that the orbital plane of the secondary and tertiary companions are inconsistent with an edge-on orbit in four out of six cases.Comment: 34 pages, 10 figures, 16 tables, including 4 tables in machine readable format and 7 tables with online supplemental dat

Wholly aromatic liquid crystalline polyetherimide (LC-PEI) resins

The benefits of liquid crystal polymers and polyetherimides are combined in an all-aromatic thermoplastic liquid crystalline polyetherimide. Because of the unique molecular structure, all-aromatic thermotropic liquid crystal polymers exhibit outstanding processing properties, excellent barrier properties, low solubilities and low coefficients of thermal expansion in the processing direction. These characteristics are combined with the strength, thermal, and radiation stability of polyetherimides