An analysis of textbooks in problems of democracy

Thesis (M.A.)--Boston University, 1945. This item was digitized by the Internet Archive

New giant H II regions in the southern sky

We present results of a search for giant H II regions in southern galaxies. Using high-resolution spectra, obtained with the Magellan Inamori Kyocera Echelle (MIKE) at the Las Campanas Magellan II telescope, we were able to resolve the emission-line profiles and determine the intrinsic velocity dispersion of the ionized gas. Out of four observed regions, selected from previous CCD narrow-band photometry, we detected three H II regions showing supersonic velocity dispersion, characteristic of giant H II regions, and their location in diagnostic diagrams suggests that a powerful starburst is the source of ionization energy.Facultad de Ciencias Astronómicas y Geofísica

Spectroscopic study of the N159/N160 complex in the Large Magellanic Cloud

We present a spectroscopic study of the N159/N160 massive star-forming region south of 30 Doradus in the Large Magellanic Cloud, classifying a total of 189 stars in the field of the complex. Most of them belong to O and early B spectral classes; we have also found some uncommon and very interesting spectra, including members of the Onfp class, a Be PCygni star, and some possible multiple systems. Using spectral types as broad indicators of evolutionary stages, we considered the evolutionary status of the region as a whole. We infer that massive stars at different evolutionary stages are present throughout the region, favoring the idea of a common time for the origin of recent star formation in the N159/N160 complex as a whole, while sequential star formation at different rates is probably present in several subregions.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

High-resolution spectroscopy of the blue compact dwarf galaxy Haro 15 : I. Internal kinematics

Using echelle spectroscopy, obtained at Las Campanas Observatory, we present a detailed study of the internal kinematics of the nebular material in multiple knots of the blue compact dwarf galaxy Haro15. A detailed analysis of the complex emission-line profiles shows the presence of an underlying broad component in almost all knots, and the brightest star-forming region shows unmistakable signs for the presence of two distinct narrow kinematical components. We also study the information that our analysis provides regarding the motion of the individual knots in the Haro15 galaxy potential, confirming that they follow galactic rotation. Finally, we examine the relation between their velocity dispersion and luminosity, finding that almost all knots follow the relation for virialized systems. This holds for the strong narrow components identified in complex fits and for single profile fits, although the latter show a flatter slope. In agreement with previous findings, in this paper we show that the existence of multiple kinematical components among massive starbursts cannot be overlooked, as it has a noticeable effect on any subsequent analysis that relies on basic parameters.Facultad de Ciencias Astronómicas y Geofísica

The massive double-lined O-type binary HD 165052

We present a new optical spectroscopic study of the O-type binary HD 165052 based on high-and intermediate-resolution CCD observations. We re-investigated the spectral classification of the binary components, obtaining spectral types of O6.5 V and O7.5 V for the primary and secondary, respectively, finding that both stars display weak CIII λ5696 emission in their spectra. We also determined a radial-velocity orbit for HD 165052 with a period of 2.95510 ± 0.00001 d, and semi-amplitudes of 94.8 and 104.7 ± 0.5km s-1, resulting in a mass ratio Q = 0.9. From a comparison with previous radial-velocity determinations, we found evidence of apsidal motion in the system. Several signatures of wind-wind collision, such as phase-locked variability of the X-ray flux and the Struve-Sahade effect, are also considered. It was also found that the reddening in the region should be normal, in contrast with previous determinations.Facultad de Ciencias Astronómicas y Geofísica

Rapid Diagnostics for Infectious Disease using Noble Metal Nanoparticles

Rapid point-of-care (POC) diagnostic devices are needed for field-forward screening of severe acute systemic febrile illnesses such as dengue, Ebola, chikungunya, and others. Multiplexed rapid lateral flow diagnostics have the potential to distinguish among multiple pathogens, thereby facilitating diagnosis and improving patient care. We present a platform for multiplexed pathogen detection which uses gold or silver nanoparticles conjugated to antibodies to sense the presence of biomarkers for different infectious diseases. We exploit the size-dependent optical properties of Ag NPs to construct a multiplexed paperfluidic lateral flow POC sensor. AgNPs of different sizes were conjugated to antibodies that bind to specific biomarkers. Red AgNPs were conjugated to antibodies that could recognize the glycoprotein for Ebola virus, green AgNPs to those that could recognize nonstructural protein 1 for dengue virus, and orange AgNPs for non structural protein 1 for yellow fever virus. Presence of each of the biomarkers resulted in a different colored band on the test line in the lateral flow test. Thus, we were able to use NP color to distinguish among three pathogens that cause a febrile illness. Because positive test lines can be imaged by eye or a mobile phone camera, the approach is adaptable to low-resource, widely deployable settings. This design requires no external excitation source and permits multiplexed analysis in a single channel, facilitating integration and manufacturing. We will also discuss engineering the nanoparticle physical properties and surface chemistry for improving detection and also optimizing device properties, and expansion of the device to detect other diseases